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   14392篇
  免费   800篇
  国内免费   239篇
医药卫生   15431篇
  2023年   80篇
  2022年   65篇
  2021年   420篇
  2020年   198篇
  2019年   274篇
  2018年   421篇
  2017年   299篇
  2016年   350篇
  2015年   445篇
  2014年   650篇
  2013年   679篇
  2012年   1048篇
  2011年   1026篇
  2010年   627篇
  2009年   517篇
  2008年   821篇
  2007年   886篇
  2006年   756篇
  2005年   757篇
  2004年   649篇
  2003年   521篇
  2002年   506篇
  2001年   437篇
  2000年   404篇
  1999年   323篇
  1998年   196篇
  1997年   166篇
  1996年   159篇
  1995年   129篇
  1994年   101篇
  1993年   84篇
  1992年   131篇
  1991年   124篇
  1990年   113篇
  1989年   113篇
  1988年   88篇
  1987年   98篇
  1986年   78篇
  1985年   74篇
  1984年   51篇
  1983年   34篇
  1982年   41篇
  1981年   31篇
  1980年   36篇
  1979年   37篇
  1977年   46篇
  1976年   52篇
  1975年   38篇
  1974年   28篇
  1972年   30篇
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
991.
Small pulmonary nodules: volume measurement at chest CT--phantom study   总被引:13,自引:0,他引:13  
Three-dimensional methods for quantifying pulmonary nodule volume at computed tomography (CT) and the effect of imaging variables were studied by using a realistic phantom. Two fixed-threshold methods, a partial-volume method (PVM) and a variable method, were used to calculate volumes of 40 plastic nodules (largest dimension, <5 mm: 20 nodules with solid attenuation and 20 with ground-glass attenuation) of known volume. Tube current times (20 and 120 mAs), reconstruction algorithms (high and low frequency), and nodule characteristics were studied. Higher precision was associated with use of a PVM with predetermined pure nodule attenuation, high-frequency algorithm, and diagnostic CT technique (120 mAs). A PVM is promising for volume quantification and follow-up of nodules.  相似文献   
992.
BACKGROUND: Castleman disease of the pleura is unusual, and we present our experience with eight surgically proven cases. METHODS: Between 1980 and 2002, 8 patients (7 women and 1 man; age range, 20 to 53 years; mean, 26.5 years) with surgically proven, pleural Castleman disease (six hyaline vascular type, one plasma cell type, and one mixed type) were encountered. Their clinical, imaging, and surgical findings were reviewed. RESULTS: Five patients were asymptomatic, 1 had dyspnea, 1 had cough, and 1 experienced chest discomfort. Chest radiography showed a well-circumscribed interlobar, cardiophrenic, or paraaortic mass in 6 patients, a massive effusion in 1, and a focal diaphragmatic bulge in 1. Six tumors showed varying degrees of contrast enhancement (10 to 95 HU; mean, 46 HU) on computed tomography. Three cases appeared as well-defined, heterogeneously hyperintense pleural masses on magnetic resonance imaging. The masses varied in size from 3 to 10 cm (mean, 5.2 cm). Five masses greater than 5 cm had prominent pleural arterial blood supply and severe adhesions requiring thoracotomy and resection of nearby structures for radical tumor excision. Blood loss from patients varied between 100 and 850 mL (mean, 620 mL). No tumor recurrence was noted during follow-up (range, 1 to 16 years; mean, 6.5 years). CONCLUSIONS: Pleural Castleman disease predominately affects young women and manifests as a well-circumscribed mass with a varying degree of contrast enhancement on computed tomography and heterogeneity on magnetic resonance imaging. Tumors greater than 5 cm have profuse pleural blood supplies and severe adhesion necessitating open thoracotomy and resection of neighboring structures. Radical resection can produce a satisfactory outcome.  相似文献   
993.
Introduction: The overarching goal of the National Cancer Institute is to eliminate death and suffering from all cancers in the next 15 years. Longitudinal analyses of population-based cancer registries allow for meaningful comparisons of epidemiology and survival-related outcomes. In order to assess the quality of US cancer care, this study uses 2 complimentary population-based datasets to report the epidemiology and outcomes of nine surgery-related cancers over the past 3 decades. Methods: Using the SEER cancer database (1973-1999), all patients (>18 y/o) diagnosed with adenocarcinoma of esophagus, stomach, biliary duct, pancreas, small bowel, colon, rectum; esophageal squamous cell carcinoma (ESC), and hepatocellular (HCC) carcinoma (n = 382,032) were analyzed. Changes in incidence rates, stage at presentation (local, regional, distant), and 5-year cancer and stage-specific survivals were determined. The OSHPD database (1990-2000), which reports California inpatient discharges, was concurrently used to evaluate inpatient mortality after surgical resection for each cancer (n = 34,057). Results: Incidence rates increased for 3 cancers (esophageal, HCC, small bowel); decreased for 3 (rectal, stomach, ESC); and stayed constant for 3 (biliary, pancreatic, colon). More patients presented with local/regional disease in the 1990s (compared to 1970s) for 8 tumors (except small bowel, p < 0.05). Five-year overall survival improved for all but small bowel (p < 0.05); and survival for local stage tumors was improved for all cancer types except small bowel and biliary (p < 0.05). Finally, inpatient mortality rates, which can be a proxy for surgical quality and safety, declined significantly for liver, esophageal, pancreatic, and gastric resections (p < 0.05) over the past decade. Conclusions: This report card evaluates longitudinal trends in epidemiology and outcomes for 9 surgery-related cancers and identifies where improvements have been made. Not only does it appear that we are detecting tumors at an earlier and more treatable stage, but also that therapies have become more effective and safe over the past 3 decades. While these findings are encouraging, it highlights the importance of examining longitudinal trends for evaluating outcomes and areas for further study.  相似文献   
994.
995.
AIMS: Minimal change disease (MCD) is the most common primary nephrotic syndrome in children. Some suggested that interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-alpha) are involved in the pathogenesis of MCD. This study was done to see changes of plasma and urinary IL-8, TNF-alpha, and their effects on determination of permeability of glomerular basement membrane (BM) contributed by heparan sulfate proteoglycan (HSPG). METHODS: Study patients consisted of 19 biopsy-proven MCD children aged 2-15 years old. Both plasma, urinary IL-8 and TNF-alpha were measured. Employing the Millicell system, IL-8 and TNF-alpha were screened for the permeability factors. We examined whether IL-8 and TNF-alpha regulated BM HSPG gene expression and HS synthesis in the glomerular epithelial cells (GECs). RESULTS: Urinary IL-8 during relapse was significantly increased when compared with that of during remission or controls (13,996 +/- 2,811 vs. 2,941 +/- 373, 5,331 +/- 640 ng/mg.cr) (p < 0.05). Urinary TNF-alpha during relapse was also significantly increased (364.4 +/- 51.2 vs. 155.3 +/- 20.8, 36.0 +/- 4.5 ng/mg.cr) (p < 0.05). Plasma IL-8 during relapse was significantly increased compared to that during remission(1.19 +/- 0.62 vs. 0.51 +/- 0.42 ng/ml) (p < 0.05). However, the negative results were obtained in the permeability assay using the Millicell system. No difference was seen in BM HSPG gene expression and HS synthesis in the GECs. CONCLUSION: Therefore, it seems that both IL-8 and TNF-alpha may not play a disease-specific role in the pathogenesis of MCD.  相似文献   
996.
BACKGROUND AND OBJECTIVES: The aim of our study was to compare the three different regional anaesthesia methods in patients who underwent transurethral resection of the prostate (TURP) and to determine the ideal anaesthesia method for TURP operation. METHODS: Totally 77 ASA II-III patients were preloaded with 500 ml 0.9% NaCl solution before regional anaesthesia. In group E (n:27) epidural anaesthesia were achieved by applying 75 mg bupivacaine heavy + 50 microg fentanyl in the L3-L4 intervertebral space. In group SP (n:28) 15 mg bupivacaine heavy + 50 microg fentanyl were used for spinal anaesthesia (L3-L4 intervertebral space) while in group SA (n:30) 10 mg bupivacaine heavy + 50 microg fentanyl were used with saddle blockade. Systolic arterial pressure (SAP), heart rate (HR), peripheral oxygen saturation (SpO2), serum sodium measurement was recorded before and after hydration and during operation. The motor block and sensory level have been measured. RESULTS: Intraoperative SAP values were more stable than the other groups in group SA. The decrease in HR values were significant 15 minutes after prehydration in three groups (p < 0.05). SpO2 values of the groups were stable during the operation. The time to reach the maximum block was very short in patients in Group SA (p < 0.0001). There was a statistically significant difference between the groups in terms of motor block values (p < 0.0001). No fully paralysed sample was seen in Group SA even though there was a sufficient surgical anaesthesia. CONCLUSIONS: Saddle block has some advantages compared to spinal and epidural anaesthesia methods such as achieving adequate anaesthesia, stable haemodynami, the lower degree of motor blockage and no full blockage in patients. Saddle block is an the most optimal anaesthesia method for TURP operation.  相似文献   
997.
Hong SJ  Ko WJ  Kim SI  Chung BH 《European urology》2003,44(1):94-9; discussion 99-100
OBJECTIVE: The aim of this study was to identify the clinical baseline factors that affect the long-term treatment failure of benign prostatic hyperplasia (BPH). METHODS: 437 men over 50 years of age with BPH were enrolled for this analysis. Patients were allocated to a medication and a surgical treatment (following medication) group. We initially examined the International Prostatic Symptom Score (IPSS), uroflow rate, prostate volume, postvoid residual volume, and the serum prostate specific antigen level as clinical baseline factors and analyzed differences between the two groups. RESULTS: 337 patients (77.1%) were given maintenance medical treatment during follow-up, and 100 patients (22.9%) had surgical treatment following medication. Statistically significant differences were found in IPSS and prostate volume between the surgical and medication groups (IPSS: 22.6+/-6.4 vs. 18.7+/-5.8, prostate volume (cm(3)): 36.3+/-14.4 vs. 30.1+/-11.0, respectively). According to the ROC curve-based prediction of the failure for medical therapy, the best cutoff values of IPSS and prostate volume were 21 (area under ROC curve: 0.67) and 32cm(3) (area under ROC curve: 0.65), respectively. CONCLUSIONS: The results show that BPH patients with more severe IPSS and larger prostate volume have a higher risk of medical treatment failure, and suggest that the IPSS and prostate volume may be useful predictors of medical treatment maintenance.  相似文献   
998.
999.
A 62 year-old man sustained esophageal perforation following intra-operative transesophageal echocardiography (TEE) in a valvular replacement surgery. Septic shock developed on the 12th postoperative day (POD) and the esophageal perforation was diagnosed with chest CT. Emergent operation together with intensive care saved the patient's life. We speculate that the mechanism of perforation was not due to manipulation of the probe, but rather due to ischemia of the esophagus resulting from the combination of probe compression, non-pulsatile flow and the distension of the atria during a lengthy procedure. It is advisable that in patients with operative risk factors, such as distension of atria, long cardiac procedure and likely ischemia of organs due to cardiopulmonary bypass, the monitoring probe of TEE should not constantly rest in the esophagus and be withdrawn when it is idle or not in actual use. In addition, if resistance has been met during the intraoperative manipulation of the probe in a patient without previous history of esophageal disease, perforation might suspected if he or she sustains postoperative fever with positive chest X-ray findings.  相似文献   
1000.
There have been conflicting reports concerning the effect of carnitine supplementation on lipid metabolism in patients on peritoneal dialysis (PD). We investigated several parameters of lipid metabolism in pediatric PD patients supplemented with carnitine. The study included 20 patients receiving PD (treatment group) aged 2–18 years and a matched healthy control group. In the treatment group, baseline triglyceride, total cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, and apolipoprotein B levels were higher than in the control group. High-density lipoprotein cholesterol, free fatty acid, phospholipids, and apolipoprotein A-I levels were not different from those in the control group. The baseline plasma free carnitine level was lower and acyl-carnitine level was higher in the treatment group. No difference was found between the groups with respect to plasma total carnitine levels. Oral l-carnitine supplementation (50 mg/kg per day for 30 days) led to a significant decrease (from a baseline value of 146.6±51.8 mg/dl to 63.6±22.2 mg/dl, P<0.001) in apolipoprotein B levels, and no significant change in the other lipid parameters of the treatment group. Oral l-carnitine supplementation does not ameliorate the lipid profile in pediatric PD patients, but it causes a significant decrease in apolipoprotein B levels. Hence, carnitine supplementation may be recommended for decreasing apolipoprotein B levels in this patient population.  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