首页 | 本学科首页   官方微博 | 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   1417746篇
  免费   114230篇
  国内免费   3359篇
耳鼻咽喉   18496篇
儿科学   46741篇
妇产科学   41194篇
基础医学   201708篇
口腔科学   38073篇
临床医学   126594篇
内科学   286028篇
皮肤病学   33530篇
神经病学   117398篇
特种医学   53959篇
外国民族医学   464篇
外科学   211576篇
综合类   32809篇
现状与发展   4篇
一般理论   493篇
预防医学   110750篇
眼科学   31620篇
药学   98979篇
  1篇
中国医学   3378篇
肿瘤学   81540篇
  2021年   11072篇
  2019年   11913篇
  2018年   16825篇
  2017年   12843篇
  2016年   14448篇
  2015年   16215篇
  2014年   22826篇
  2013年   33700篇
  2012年   45840篇
  2011年   48416篇
  2010年   28439篇
  2009年   27284篇
  2008年   44667篇
  2007年   47215篇
  2006年   47798篇
  2005年   46199篇
  2004年   44070篇
  2003年   41968篇
  2002年   40462篇
  2001年   73145篇
  2000年   74707篇
  1999年   61703篇
  1998年   17045篇
  1997年   15469篇
  1996年   15611篇
  1995年   14824篇
  1994年   13445篇
  1993年   12612篇
  1992年   45918篇
  1991年   43573篇
  1990年   41560篇
  1989年   39616篇
  1988年   36239篇
  1987年   35413篇
  1986年   32909篇
  1985年   31339篇
  1984年   23857篇
  1983年   20047篇
  1982年   12222篇
  1981年   10796篇
  1979年   20741篇
  1978年   14620篇
  1977年   12111篇
  1976年   11385篇
  1975年   11658篇
  1974年   14031篇
  1973年   13562篇
  1972年   12663篇
  1971年   11488篇
  1970年   10938篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Metabolism describes the series of chemical reactions that are concerned with the provision of energy to biological systems. They may be divided into reactions involved in energy yield (catabolism: demand exceeds supply), and energy storage (anabolism: supply exceeds demand). Regulation of these pathways is critical for homeostasis, and derangements in metabolism are seen in a wide variety of pathological processes. Understanding metabolism is key to the treatment of many diseases, notably diabetes, as well as underpinning clinical nutritional support.  相似文献   
23.
24.
25.
Sinus venosus atrial septal defect (SV‐ASD) usually coexists with partial anomalous pulmonary vein connection (PAPVC). It is a difficult diagnosis in transthoracic echocardiography (TTE) due to eccentric position of defects. We present a rare case of atypical anatomical variation in PAPVC, which was never described before. Two right pulmonary veins drained into superior vena cava, which overrode SV‐ASD and interatrial septum, a third pulmonary vein into the right atrium. Complete diagnosis could not be set after TTE, nor transesophageal echocardiography, whereas angio‐CT was finally conclusive. This diagnostic approach allowed the surgical planning.  相似文献   
26.
27.
In the current immunosuppressive therapy era, vessel thrombosis is the most common cause of early graft loss after renal transplantation. The prevalence of IgA anti–β2-glycoprotein I antibodies (IgA-aB2GPI-ab) in patients on dialysis is elevated (>30%), and these antibodies correlate with mortality and cardiovascular morbidity. To evaluate the effect of IgA-aB2GPI-ab in patients with transplants, we followed all patients transplanted from 2000 to 2002 in the Hospital 12 de Octubre prospectively for 10 years. Presence of IgA-aB2GPI-ab in pretransplant serum was examined retrospectively. Of 269 patients, 89 patients were positive for IgA-aB2GPI-ab (33%; group 1), and the remaining patients were negative (67%; group 2). Graft loss at 6 months post-transplant was significantly higher in group 1 (10 of 89 versus 3 of 180 patients in group 2; P=0.002). The most frequent cause of graft loss was thrombosis of the vessels, which was observed only in group 1 (8 of 10 versus 0 of 3 patients in group 2; P=0.04). Multivariate analysis showed that the presence of IgA-aB2GPI-ab was an independent risk factor for early graft loss (P=0.04) and delayed graft function (P=0.04). There were no significant differences regarding patient survival between the two groups. Graft survival was similar in both groups after 6 months. In conclusion, patients with pretransplant IgA-aB2GPI-ab have a high risk of early graft loss caused by thrombosis and a high risk of delayed graft function. Therefore, pretransplant IgA-aB2GPI-ab may have a detrimental effect on early clinical outcomes after renal transplantation.  相似文献   
28.
29.
Analyzing functional species’ characteristics (species traits) that represent physiological, life history and morphological characteristics of species help understanding the impacts of various stressors on aquatic communities at field conditions. This research aimed to study the combined effects of pesticides and other environmental factors (temperature, dissolved oxygen, dissolved organic carbon, floating macrophytes cover, phosphate, nitrite, and nitrate) on the trait modality distribution of aquatic macrofauna communities. To this purpose, a field inventory was performed in a flower bulb growing area of the Netherlands with significant variation in pesticides pressures. Macrofauna community composition, water chemistry parameters and pesticide concentrations in ditches next to flower bulb fields were determined. Trait modalities of nine traits (feeding mode, respiration mode, locomotion type, resistance form, reproduction mode, life stage, voltinism, saprobity, maximum body size) likely to indicate pesticides impacts were analyzed. According to a redundancy analysis, phosphate -and not pesticides- constituted the main factor structuring the trait modality distribution of aquatic macrofauna. The functional composition could be ascribed for 2–4 % to pesticides, and for 3–11 % to phosphate. The lack of trait responses to pesticides may indicate that species may have used alternative strategies to adapt to ambient pesticides stress. Biomass of animals exhibiting trait modalities related to feeding by predation and grazing, presence of diapause form or dormancy, reproduction by free clutches and ovoviviparity, life stage of larvae and pupa, was negatively correlated to the concentration of phosphate. Hence, despite the high pesticide pollution in the area, variation in nutrient-related stressors seems to be the dominant driver of the functional composition of aquatic macrofauna assembly in agricultural ditches.  相似文献   
30.
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