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   4113篇
  免费   159篇
  国内免费   39篇
医药卫生   4311篇
  2024年   4篇
  2023年   30篇
  2022年   71篇
  2021年   122篇
  2020年   69篇
  2019年   91篇
  2018年   137篇
  2017年   76篇
  2016年   97篇
  2015年   126篇
  2014年   168篇
  2013年   249篇
  2012年   303篇
  2011年   325篇
  2010年   204篇
  2009年   160篇
  2008年   303篇
  2007年   267篇
  2006年   245篇
  2005年   263篇
  2004年   227篇
  2003年   197篇
  2002年   196篇
  2001年   32篇
  2000年   23篇
  1999年   18篇
  1998年   37篇
  1997年   27篇
  1996年   29篇
  1995年   21篇
  1994年   19篇
  1993年   18篇
  1992年   14篇
  1991年   14篇
  1990年   11篇
  1989年   12篇
  1988年   15篇
  1987年   14篇
  1986年   8篇
  1985年   9篇
  1984年   6篇
  1983年   4篇
  1982年   8篇
  1981年   5篇
  1980年   8篇
  1977年   3篇
  1975年   3篇
  1971年   2篇
  1969年   2篇
  1931年   2篇
排序方式: 共有4311条查询结果,搜索用时 15 毫秒
91.
Experiments were undertaken to assess the role of amifostine in the activation of latent TGFbeta1 and in the smad proteins cascade (smad 2/3, smad4, smad7), focusing on megakaryocytes, in the bone marrow irradiated in vivo. Non-irradiated megakaryocytes were negative for active TGFbeta1. Immunopositivity to active TGFbeta1 was detected in megakaryocytes 10 days after irradiation in amifostine- treated and untreated marrows. Smad 2/3 and smad 4 were strongly positive in the nucleus of megakaryocytes 10 days after irradiation. At the same time, a predominant hypocellular bone marrow with foci of hematopoiesis was observed with few megakaryocytes. An increase in the number of reticulin fibers was also seen. In amifostine-treated marrows, smad 2/3 and smad4 were not detected in the nucleus but were positive in the cytoplasm of megakaryocytes 10 days after irradiation. Coincidentally, bone marrows were cellular with megakaryocytes. Smad7 immunoexpression was detected in the cytoplasm of megakaryocytes in the non-irradiated, amifostine-treated and in the irradiated, amifostine-treated marrows. Data indicate that amifostine does not prevent latent TGFbeta1 activation in irradiated megakaryocytes. While TGFbeta1 signal transduction occurs in megakaryocytes in untreated bone marrows, it is inhibited in megakaryocytes in amifostine-treated marrows due to the induction of smad 7 activation. This is the first report showing smad 7 activation by amifostine. Our results also suggest a role for TGFbeta1 as an inhibitor of megakaryocytes in vivo.  相似文献   
92.
93.

Background

The Temperament Evaluation of Memphis, Pisa, Paris and San Diego – Autoquestionnaire (TEMPS-A) is a widely used self-reported tool aimed at measuring the affective temperaments that define the bipolar spectrum, with cyclothymic, depressive, irritable, hyperthymic, and anxious subscales. Confirmatory factor analysis (CFA) was rarely used to confirm the expected five-factor model. Measurement invariance was never tested.

Methods

Cross-sectional, survey design involving 649 Italian college students (males: 47%). The short 39-item TEMPS-A and the 12-item General Health Questionnaire (GHQ-12) were used as measures of the affective temperaments and of psychological distress, respectively. CFA was applied to the TEMPS-A. Measurement invariance by gender, age and levels of psychological distress on the GHQ-12 was calculated with the establishment of subsequent equivalence constraints in the model parameters across groups.

Results

The expected five-factor model had the best fit for all CFA indexes. Configural, metric and scalar invariance of the five-factor model of the TEMPS-A was proved across gender, age and levels of psychological distress of the participants. The hyperthymic temperament subscale has low or no links with the other affective temperament subscales, which were interrelated with medium to large effect sizes.

Limitations

College students might be not representative of the general population. No information on the clinical status of the students was available beyond self-report data.

Conclusion

The study proved the measurement invariance of the (short) TEMPS-A, which is a pre-requisite to compare groups or individuals in cross-sectional and longitudinal surveys. Generalizability cannot be assumed without replication of the findings in clinical samples.  相似文献   
94.
Serotonin 7 (5-hydroxytryptamine7 or 5-HT7) is the most recently identified serotonin receptor. It is involved in mood disorders and is studied as a target for antidepressants. Here, we report on the structural manipulation of the 5-HT7 receptor ligand 4-[2-(3-methoxyphenyl)ethyl]-1-(2-methoxyphenyl)piperazine (1a) aimed at obtaining 5-HT7 receptor ligands endowed with good in vitro metabolic stability. A set of N-[3-methoxyphenyl)ethyl-substituted] 1-arylpiperazine, 4-arylpiperidine and 1-aryl-4-aminopiperidine was synthesized and tested in radioligand binding assays at human cloned 5-HT7 and 5-HT1A receptors. In vitro metabolic stability of the target compounds was assessed after incubation with rat hepatic S9 microsomal fraction. Among the new compounds, 1-(2-biphenyl)-4-[2-(3-methoxyphenyl)ethyl]piperazine (1d) and 4-(2-biphenyl)-1-[2-(3-methoxyphenyl)ethyl]piperidine (2d) showed a good compromise between affinity at 5-HT7 receptor (K i = 7.5 nM and 13 nM, respectively) and in vitro metabolic stability (26 and 65 % recovery of parent compound, respectively) but were poorly selective over 5-HT1A receptor.  相似文献   
95.
In this work, we propose that for further studies of the physiopathology and treatment for inflammatory bowel diseases, an integral view of the conditions, including the triad of microbiota–heat shock proteins (HSPs)–probiotics, ought to be considered. Microbiota is the complex microbial flora that resides in the gut, affecting not only gut functions but also the health status of the whole body. Alteration in the microbiota’s composition has been implicated in a variety of pathological conditions (e.g., ulcerative colitis, UC), involving both gut and extra-intestinal tissues and organs. Some of these pathologies are also associated with an altered expression of HSPs (chaperones) and this is the reason why they may be considered chaperonopathies. Probiotics, which are live microorganisms able to restore the correct, healthy equilibrium of microbiota composition, can ameliorate symptoms in patients suffering from UC and modulate expression levels of HSPs. However, currently probiotic therapy follows ex-adiuvantibus criteria, i.e., treatments with beneficial effects but whose mechanism of action is unknown, which should be changed so the probiotics needed in each case are predetermined on the basis of the patient’s microbiota. Consequently, efforts are necessary to develop diagnostic tools for elucidating levels and distribution of HSPs and the microbiota composition (microbiota fingerprint) of each subject and, thus, guide specific probiotic therapy, tailored to meet the needs of the patient. Microbiota fingerprinting ought to include molecular biology techniques for sequencing highly conserved DNA, e.g., genes encoding 16S RNA, for species identification and, in addition, quantification of each relevant microbe.  相似文献   
96.
Tumor necrosis factor alpha (TNFα) in intestinal mucosa plays a key role in the inflammation characterizing Crohn’s disease (CD). Moreover, adhesion molecule syndecan-1 mediates the maintenance of mucosal integrity and supports tissue repair. Therefore, our aim in this study was to correlate simultaneous expression of TNFα and syndecan-1 in patients affected by CD. Biopsies from 10 patients with CD of large bowel and 10 subjects with irritable bowel syndrome (controls) were studied by immunohistochemical detection of both TNFα and syndecan-1 on successive serial sections. Overall labeling index (OLI) was indicated by the percentage of positive stromal (i.e., nonepithelial) cells/1000 counted in randomized fields, whereas selected labeling index (SLI) was represented by the simultaneous evaluation of both molecules in a same single selected field of each specimen. TNFα and syndecan-1 OLI were significantly higher in CD compared with controls, while SLI showed an inverse relationship between the molecules in CD which was not observed in controls. Epithelial syndecan-1 cytoplasmatic staining of superficial epithelium was associated with loss of basolateral staining in the crypts and high stromal TNFα in CD. In conclusion, TNFα and syndecan-1 expression is increased in the intestinal mucosa of patients with CD. However, the expression of the two molecules is inversely related when a single field is considered, these data supporting the possibility of a downregulation exerted by TNFα.  相似文献   
97.
Cognition can be deteriorated in older persons because of several potential mechanisms including the hormonal changes occurring with age. Stress events cause modification in hormonal balance with acute and chronic changes such as increase in cortisol and thyroid hormones, and simultaneous alterations in dehydroepiandrosterone sulphate, testosterone and insulin like growth factor-1 levels. The ability to cope with stress and regain previous healthy status, also called resiliency, is particularly impaired in older persons Thus, stressful conditions and hormonal dysregulation might concur to the onset of cognitive impairment in this population.  相似文献   
98.
BackgroundEpidemiological evidence suggests that anti-inflammatory and immunomodulatory properties of statins may reduce the risk of infections and infection-related complications.ObjectiveWe aimed to assess the impact of prior statin use on coronavirus disease (COVID-19) severity and mortality.MethodsIn this observational multicenter study, consecutive patients hospitalized for COVID-19 were enrolled. In-hospital mortality and severity of COVID-19 assessed with National Early Warning Score (NEWS) were deemed primary and secondary outcomes, respectively. Propensity score (PS) matching was used to obtain balanced cohorts.ResultsAmong 842 patients enrolled, 179 (21%) were treated with statins before admission. Statin patients showed more comorbidities and more severe COVID-19 (NEWS 4 [IQR 2–6] vs 3 [IQR 2–5], p < 0.001). Despite having similar rates of intensive care unit admission, noninvasive ventilation, and mechanical ventilation, statin users appeared to show higher mortality rates. After balancing pre-existing relevant clinical conditions that could affect COVID-19 prognosis with PS matching, statin therapy confirmed its association with a more severe disease (NEWS ≥5 61% vs. 48%, p = 0.025) but not with in-hospital mortality (26% vs. 28%, p = 0.185). At univariate logistic regression analysis, statin use was confirmed not to be associated with mortality (OR 0.901; 95% CI: 0.537 to 1.51; p = 0.692) and to be associated with a more severe disease (NEWS≥5 OR 1.7; 95% CI 1.067–2.71; p = 0.026).ConclusionsOur results did not confirm the supposed favorable effects of statin therapy on COVID-19 outcomes. Conversely, they suggest that statin use should be considered as a proxy of underlying comorbidities, which indeed expose to increased risks of more severe COVID-19.  相似文献   
99.

Objective

To evaluate the influence of pulmonary hypertension in the ultra-fast-track anesthesia technique in adult cardiac surgery.

Methods

A retrospective study. They were included 40 patients divided into two groups: GI (without pulmonary hypertension) and GII (with pulmonary hypertension). Based on data obtained by transthoracic echocardiography. We considered as the absence of pulmonary hypertension: a pulmonary artery systolic pressure (sPAP) <36 mmHg, with tricuspid regurgitation velocity <2.8 m/s and no additional echocardiographic signs of PH, and PH as presence: a sPAP >40 mmHg associated with additional echocardiographic signs of PH. It was established as influence of pulmonary hypertension: the impossibility of extubation in the operating room, the increase in the time interval for extubation and reintubation the first 24 hours postoperatively. Univariate and multivariate analyzes were performed when necessary. Considered significant a P value <0.05.

Results

The GI was composed of 21 patients and GII for 19. All patients (100%) were extubated in the operating room in a medium time interval of 17.58±8.06 min with a median of 18 min in GII and 17 min in GI. PH did not increase the time interval for extubation (P=0.397). It required reintubation of 2 patients in GII (5% of the total), without statistically significant as compared to GI (P=0.488).

Conclusion

In this study, pulmonary hypertension did not influence on ultra-fast-track anesthesia in adult cardiac surgery.  相似文献   
100.

Purpose

The treatment of adult scoliosis is a challenge especially in patients over 50 years old with severe, rigid curves in whom the use of vertebral osteotomies may be necessary to correct the deformity. The aim the study was to analyse the perioperative complications related to vertebral osteotomies in elderly treated for spinal deformity.

Methods

We analysed 72 consecutive cases of kyphoscoliosis, we classify them according to Berjano–Lamartina classification. We divided patients into two groups: we only practised SPO and/or PO in patients that composed group A; we practised also PSO in patients that composed group B. We retrospectively analysed the perioperative complications and radiographical results. Average follow-up was 30 months.

Results

We had 50 cases of degenerative segment diseases (DSD) Type III, 13 Type IVa DSD and 9 Type IVb DSD. Mean age was 60.7 years old. Overall complication rate was 22.2 %. In group A, the complication rate was 16.9 % while in group B it was 46.2 %. Mean Cobb primary curve angle was 41.75° with average C7 plumb line (C7PL) of 4.49 cm, residual scoliosis after surgery was 15.41° and average C7PL of 2.08 cm, with statistically significant differences.

Conclusions

Previous studies have shown increased complication rates with vertebral osteotomies in elderly patients, our experience support this evidence. Our study demonstrates a high incidence of intraoperative complication rate in elderly patients underwent a PSO. PSO is a demanding technique to be considered in very selected and motivated patients who must be carefully informed about the risks of the procedure.
  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