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   424152篇
  免费   23451篇
  国内免费   704篇
耳鼻咽喉   6211篇
儿科学   14257篇
妇产科学   13026篇
基础医学   62195篇
口腔科学   11819篇
临床医学   32110篇
内科学   87890篇
皮肤病学   10517篇
神经病学   31155篇
特种医学   14537篇
外国民族医学   44篇
外科学   62572篇
综合类   8446篇
现状与发展   1篇
一般理论   196篇
预防医学   32467篇
眼科学   9809篇
药学   29570篇
中国医学   1433篇
肿瘤学   20052篇
  2021年   5024篇
  2020年   2786篇
  2019年   5337篇
  2018年   8517篇
  2017年   5541篇
  2016年   5750篇
  2015年   6471篇
  2014年   8126篇
  2013年   12524篇
  2012年   18194篇
  2011年   19271篇
  2010年   11085篇
  2009年   9147篇
  2008年   16544篇
  2007年   17832篇
  2006年   17107篇
  2005年   16637篇
  2004年   15467篇
  2003年   14549篇
  2002年   13758篇
  2001年   17102篇
  2000年   18087篇
  1999年   14718篇
  1998年   3589篇
  1997年   3181篇
  1996年   2983篇
  1995年   2845篇
  1992年   9577篇
  1991年   9495篇
  1990年   9201篇
  1989年   8835篇
  1988年   7939篇
  1987年   7699篇
  1986年   7331篇
  1985年   7025篇
  1984年   5138篇
  1983年   4397篇
  1982年   2613篇
  1979年   4752篇
  1978年   3421篇
  1977年   2918篇
  1976年   2708篇
  1975年   3094篇
  1974年   3662篇
  1973年   3700篇
  1972年   3403篇
  1971年   3244篇
  1970年   3118篇
  1969年   2866篇
  1968年   2794篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
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   
22.
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   
23.
24.
25.
26.
27.
Obesity Surgery - Laparoscopic sleeve gastrectomy (LSG) is increasingly playing a key role in obesity management. Such operations, however, carry complications sometimes including leaks. The...  相似文献   
28.
Pharmaceutical Chemistry Journal - Three extracts were produced from the above-ground part of the meadowsweet Filipendula ulmaria (L.) Maxim. using water, 40% ethanol, and 70% ethanol. Comparative...  相似文献   
29.
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