首页 | 官方网站   微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   54594篇
  免费   3295篇
  国内免费   593篇
医药卫生   58482篇
  2023年   299篇
  2022年   204篇
  2021年   1982篇
  2020年   986篇
  2019年   1287篇
  2018年   1667篇
  2017年   1241篇
  2016年   1757篇
  2015年   2559篇
  2014年   3058篇
  2013年   3488篇
  2012年   5314篇
  2011年   4806篇
  2010年   2803篇
  2009年   2360篇
  2008年   3416篇
  2007年   3095篇
  2006年   2652篇
  2005年   2352篇
  2004年   2026篇
  2003年   1693篇
  2002年   1435篇
  2001年   1363篇
  2000年   1262篇
  1999年   906篇
  1998年   362篇
  1997年   249篇
  1996年   192篇
  1995年   175篇
  1994年   147篇
  1993年   132篇
  1992年   331篇
  1991年   315篇
  1990年   280篇
  1989年   258篇
  1988年   247篇
  1987年   248篇
  1986年   177篇
  1985年   165篇
  1984年   119篇
  1983年   111篇
  1982年   55篇
  1981年   57篇
  1979年   81篇
  1978年   68篇
  1975年   50篇
  1974年   60篇
  1973年   51篇
  1972年   50篇
  1970年   48篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Appendicitis is a common intra-abdominal inflammatory disease, and morbidity increases with age when perforation occurs. Because, not all patients require emergency surgery, there have been numerous studies on factors for predicting perforated appendicitis. In this study, we aimed to confirm whether the delta neutrophil index (DNI) and the time from symptom onset to surgery are effective predictors for perforated appendicitis in different age groups.This was a retrospective study conducted on 542 appendicitis patients who underwent surgery at Kangdong Sacred Heart Hospital. The simple group consisted of 431 subjects, and the perforation group consisted of 111 subjects.Multiple logistic regression analyses demonstrated that age, neutrophil percentage, DNI, C-reactive protein (CRP), and symptomatic time were significant predictors of perforation. Analysis of the receiver-operating characteristic curve showed that the DNI was the most reliable predictive value. In the analyses according to age, the perforation rate was higher in the >65-year-age group; these patients also had a higher DNI, CRP, and symptomatic time. In the DNI analysis using receiver operating characteristic (ROC) analysis, the area under the curve was higher in the >65-year-age group than in other age groups. In addition, the cutoff values have been determined and perforation occurred significantly in the group with a DNI value of 2.1 or higher and a symptomatic time of 33 hours or longer.DNI is effective in predicting perforation in patients with appendicitis compared with other inflammatory factors. Furthermore, the simultaneous measurement of symptomatic time and DNI is helpful in predicting perforation and determining whether emergency surgery is necessary.  相似文献   
992.
Posaconazole prophylaxis is effective in decreasing the incidence of invasive fungal diseases (IFDs) in patients with acute myeloid leukemia (AML). However, the use of antifungal prophylaxis varies in real-life practice, and only a small number of studies have compared the incidence of IFDs between those receiving posaconazole prophylaxis and those without prophylaxis. We compared the clinical characteristics and outcomes of IFDs between patients with AML who received posaconazole prophylaxis and those without antifungal prophylaxis.We reviewed the medical records of adult AML patients who underwent induction chemotherapy between June 2016 and October 2019 at Asan Medical Center (Seoul, South Korea), where posaconazole prophylaxis is not administered in patients with gastrointestinal symptoms that may hinder sufficient absorption of oral prophylactic agents, and in patients with abnormal liver functions considering the possible exacerbation of adverse events. Patients who received posaconazole prophylaxis for ≥7 days were included in the prophylaxis group. Clinical characteristics and outcomes including the incidence of IFDs were compared between the 2 groups.Of the 247 patients with AML who underwent induction chemotherapy, 162 (66%) received posaconazole prophylaxis and 85 (34%) did not receive any prophylaxis. The incidence of proven/probable IFD was significantly higher in the no prophylaxis group than in the prophylaxis group (9.4% [8/85] vs 2.5% [4/162], P = .03). Of the 8 cases of IFDs in the no prophylaxis group, 7 were mold infections and 1 was invasive candidiasis. Of the 4 cases of IFDs in the prophylaxis group, 3 were mold infections and 1 was invasive candidiasis. Patients with posaconazole prophylaxis less frequently received therapeutic antifungal therapy (2.5% vs 9.4%, P = .03) and had a longer median, duration from chemotherapy to antifungal therapy compared with the no prophylaxis group (18 vs 11 days, P < .01). The rate of IFD-related mortality was similar between the 2 groups (0.6% vs 0%, P > .99).Patients with AML who received posaconazole prophylaxis had a lower incidence of breakthrough IFDs compared with those who did not receive any prophylaxis. Invasive mold infection was the most common IFD regardless of antifungal prophylaxis.  相似文献   
993.
Nerve injury especially inferior alveolar nerve (IAN) is the one of the complications that occur when the mandibular third molar (M3) is extracted and in case of high risk patients, coronectomy might be an alternative to tooth extraction. The purpose of this retrospective study was to analyze root migration and its influencing factors at 6 months after coronectomy in both 2- and 3-dimensions using periapical view and cone-beam computed tomography (CBCT). We analyzed 33 cases of root remnant after coronectomy and measured the amount of migration in CBCT. The following factors that could possibly affect root migration were also analyzed: age, gender, number of M3 roots, shape of M3s, Pell, and Gregory classification, mesiodistal (MD) angulation, buccolingual (BL) angulation, contact point with the second molar, root curvature, and complete removal of the coronal portion. Migration of greater than 2 mm was found in 64% of the roots in the 2-dimensional (2D) analysis, and the average root migration was 4.11 mm in the 3-dimensional (3D) analysis. The factors affecting migration were the root morphology, complete removal of the coronal portion, impaction depth, and MD angulation in the 2D analysis, and MD and BL angulation in the 3D analysis. Ensuring sufficient space for root migration especially considering angulation, depth and complete removal of the coronal portion might be important factors after coronectomy of the M3. Root remnant after coronectomy of M3 may migrate in young patients who has sufficient empty coronal space and this may reduce the nerve damage by the separation of IAN and M3.  相似文献   
994.
Anhedonia, the inability to feel pleasure, and amotivation, the lack of motivation, are two prominent negative symptoms of schizophrenia, which contribute to the poor social and occupational behaviors in the patients. Recently growing evidence shows that anhedonia and amotivation are tied together, but have distinct neural correlates. It is important to note that both of these symptoms may derive from deficient functioning of the reward network. A further analysis into the neuroimaging findings of schizophrenia shows that the neural correlates overlap in the reward network including the ventral striatum, anterior cingulate cortex and orbitofrontal cortex. Other neuroimaging studies have demonstrated the involvement of the default mode network in anhedonia. The identification of a specific deficit in hedonic and motivational capacity may help to elucidate the mechanisms behind social functioning deficits in schizophrenia, and may also lead to more targeted treatment of negative symptoms.  相似文献   
995.
BackgroundWe have previously reported that unilateral groin‐single transseptal (ST) ablation in patients with paroxysmal atrial fibrillation (AF) was safe and significantly reduced patient discomfort compared with bilateral groin‐double transseptal (DT) ablation.HypothesisIn the present study, we hypothesized that ST ablation would be as effective and safe as DT ablation in real‐world practice like previous study. Among the 1765 consecutive patients in the Yonsei AF ablation cohort from October 2015 to January 2020, 1144 patients who underwent radiofrequency ablation were included for the analysis. Among them, 450 underwent ST ablation and 694 underwent DT ablation.ResultsThe total procedure time, ablation time, and fluoroscopy time were longer in the ST group than in the DT group (p < .05 for all). The hospital stay after catheter ablation was 1.3 ± 1.1 days which was longer in DT group than ST group (p = .001). No significant difference was observed in the complication rate (p = .263) and AF‐free survival rate (log‐rank p = .19) between the groups. However, after excluding patients who used antiarrhythmic drugs when AF recurred, the AF‐free survival rates were lower in the DT group than in the ST group before and after propensity score matching (log‐rank p = .026 and .047, respectively).ConclusionAlthough the ST approach increases the procedure time compared with the DT approach owing to the need for more frequent catheter exchanges, the ST approach is a feasible and safe strategy for AF ablation in terms of rhythm outcomes and risk of complications.  相似文献   
996.

Aim:

Free fatty acid receptor 4 (FFA4; formerly known as GPR120) is the G protein-coupled receptor (GPCR) for omega-3 polyunsaturated fatty acids. FFA4 has been found to express in the small intestines and colons of mice and humans. In this study we investigate the effects of omega-3 polyunsaturated fatty acids on FFA4 in human colon epithelial cells in vitro.

Methods:

HCT116 and HT-29 human colon epithelial cell lines endogenously expressing FFA4 were used. Intracellular Ca2+ concentration ([Ca2+]i) was measured in fura 2-AM-loaded cells with fluorescence spectrophotometry. RT-PCR and immunohistochemistry were used to detect FFA4.

Results:

Ten to 100 μmol/L of omega-3 polyunsaturated fatty acids α-linolenic acid (αLA) or eicosapentaenoic acid (EPA) induced dose-dependent [Ca2+]i increase in HCT116 and HT-29 cells, whereas docosahexaenoic acid (DHA) had no effect. In addition, the omega-6 fatty acids linoleic acid and γ-linoleic acid also dose-dependently increase [Ca2+]i, but the mono-unsaturated fatty acid oleic acid and saturated fatty acids such as stearic acid and palmitic acid had no effect. In HCT116 and HT-29 cells, the αLA-induced [Ca2+]i increase was partially inhibited by pretreatment with EGTA, phospholipase C inhibitor edelfosine, cADPR inhibitors 8-bro-cADPR or DAB, and abolished by pretreatment with Ca2+ATPase inhibitor thapsigargin, but was not affected by Gi/o protein inhibitor PTX or IP3R inhibitor 2-APB.

Conclusion:

Omega-3 and omega-6 long-chain polyunsaturated fatty acids (C18-20) induce Ca2+ mobilization responses in human colonic epithelial cells in vitro through activation of FFA4 and PTX-insensitive Gi/o protein, followed by Ca2+ release from thapsigargin-sensitive Ca2+ stores and Ca2+ influx across the plasma membrane.  相似文献   
997.
Our previous study demonstrated that patients with end-stage renal disease had decreased structural and functional brain connectivity, and there was a significant association between brain connectivity and cognitive function. The aim of this study was to evaluate the alterations of structural and functional connectivity using graph theoretical analysis in neurologically asymptomatic patients with relatively early-stage chronic kidney disease (CKD).We enrolled 18 neurologically asymptomatic patients with early CKD and 28 healthy controls. All the subjects underwent diffusion-tension imaging and resting functional magnetic resonance imaging. We calculated structural and functional connectivity based on diffusion-tension imaging and resting functional magnetic resonance imaging using a graph theoretical analysis. Then, we investigated differences of structural and functional connectivity between the CKD patients and the healthy controls.All the measures of structural connectivity were significantly different between the patients with CKD and healthy controls. The global efficiency, local efficiency, mean clustering coefficient, and small-worldness index were decreased, whereas the characteristic path length was increased in the patients with CKD compared with healthy controls. The structural betweenness centrality of the left calcarine and right posterior cingulum was also significantly different from that in healthy participants. However, all the measures of global functional connectivity in patients with CKD were not different from those in healthy controls. In patients with CKD, the functional betweenness centrality of the right insular cortex, right occipital pole, and right thalamus was significantly different from that in healthy participants.There are significant alterations of the global structural connectivity between the patients with CKD and the healthy subjects, whereas the global functional connectivity of the brain network is preserved. We find that the efficiency of the structural brain network is decreased in the patients with CKD.  相似文献   
998.
Rationale:A case of traumatic atlanto-axial rotatory subluxation (AARS), dens fracture, rupture of transverse atlantal ligament (TAL), and subaxial spinal cord injury without radiographic abnormality (SCIWORA) of Brown-Sequard syndrome has never been reported in a child.Patient concerns:A 7-year-old boy presented to hospital with torticollis, neck pain, and limited neck rotation after a seat-belt injury sustained during a car accident. Neurologic examination revealed right-side motor weakness and left-side sensory abnormality, known as Brown-Sequard syndrome.Diagnosis:Radiologic examinations revealed type II AARS (Fielding and Hawkins classification), increased atlanto-dental interval (ADI) of 4.5 mm due to a type 1B TAL rupture (Dickman classification), a displaced transverse dens fracture along with an ossiculum terminale, and an intramedullary hemorrhage on the right side of the spinal cord at C3–4.Interventions:The patient immediately received methylprednisolone, and his motor weakness and sensory abnormality gradually improved. At the same time, the patient underwent initial halter traction for 2 weeks, but he failed to achieve successful reduction and required manual reduction under general anesthesia.Outcomes:At the 7-month follow-up visit, radiologic examinations showed a corrected type II AARS that was well maintained and normalization of the ADI to 2 mm. The reduced transverse dens fracture was well maintained but still not united. All clinical symptoms were significantly improved, except the remaining motor weakness of the right upper extremity.Lessons:To the best of our knowledge, this is the first report of traumatic AARS, dens fracture, TAL rupture, and subaxial SCIWORA of Brown-Sequard syndrome in a child. Appropriate diagnosis and careful treatment strategy are required for successful management of complex cervical injuries in a child.  相似文献   
999.
Along with recent developments in deep learning techniques, computer-aided diagnosis (CAD) has been growing rapidly in the medical imaging field. In this work, we evaluate the deep learning-based CAD algorithm (DCAD) for detecting and localizing 3 major thoracic abnormalities visible on chest radiographs (CR) and to compare the performance of physicians with and without the assistance of the algorithm. A subset of 244 subjects (60% abnormal CRs) was evaluated. Abnormal findings included mass/nodules (55%), consolidation (21%), and pneumothorax (24%). Observer performance tests were conducted to assess whether the performance of physicians could be enhanced with the algorithm. The area under the receiver operating characteristic (ROC) curve (AUC) and the area under the jackknife alternative free-response ROC (JAFROC) were measured to evaluate the performance of the algorithm and physicians in image classification and lesion detection, respectively. The AUCs for nodule/mass, consolidation, and pneumothorax were 0.9883, 1.000, and 0.9997, respectively. For the image classification, the overall AUC of the pooled physicians was 0.8679 without DCAD and 0.9112 with DCAD. Regarding lesion detection, the pooled observers exhibited a weighted JAFROC figure of merit (FOM) of 0.8426 without DCAD and 0.9112 with DCAD. DCAD for CRs could enhance physicians’ performance in the detection of 3 major thoracic abnormalities.  相似文献   
1000.
Malignant gastric lymphoma (MGL) accounts for a small proportion (upto 5%) of gastric malignancies. However, unlike for advanced gastric cancer (AGC) that requires surgical treatment, the standard treatments for MGL are chemotherapy and radiotherapy. Hence, the initial impression of the endoscopist is critical for the differential diagnosis and for planning future treatment. The purpose of this study was to assess the endoscopic diagnostic accuracy and the possibility of distinguishing between AGC and MGL depending on the endoscopist''s experience.A total of 48 patients who had MGL, and 48 age and sex-matched patients who had AGC were assessed by endoscopic review at a tertiary referral hospital between June 2008 and February 2017. Two endoscopic specialists reviewed the endoscopic findings and divided these diagnoses into 5 groups: Borrmann type (1, 2, 3, and 4) and early gastric cancer-like type. After this, 7 experts and 8 trainees were asked to complete a quiz that was comprised of 6 images for each of the 96 cases and to provide an endoscopic diagnosis for each case. The test results were analyzed to assess the diagnostic accuracy according to the pathologic results, endoscopic subgroups, and endoscopists’ experience. For inter-observer agreement was calculated with Fleiss kappa values.The overall diagnostic accuracy of endoscopic findings by the experts was 0.604 and that by the trainees was 0.493 (P = .050). There was no significant difference in the diagnosis according to the final pathology (lymphoma cases, 0.518 vs 0.440, P = .378; AGC cases, 0.690 vs 0.547, P = .089, respectively). In the subgroup analysis, the experts showed significantly higher diagnostic accuracy for the endoscopic Borrmann type 4 subgroup, including lymphoma or AGC cases, than the trainees (P = .001). Inter-observer agreement of final diagnosis (Fleiss kappa, 0.174) and endoscopic classification groups (Fleiss kappa, 0.123–0.271) was slightly and fair agreement.The experts tended to have a higher endoscopic diagnostic accuracy. Distinguishing MGL from AGC based on endoscopic findings is difficult, especially for the beginners. Even if the endoscopic impression is AGC, it is important to consider MGL in the differential diagnosis.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号