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   1515596篇
  免费   117433篇
  国内免费   3597篇
耳鼻咽喉   19912篇
儿科学   49652篇
妇产科学   43479篇
基础医学   214832篇
口腔科学   41385篇
临床医学   132550篇
内科学   309919篇
皮肤病学   36707篇
神经病学   125052篇
特种医学   56145篇
外国民族医学   464篇
外科学   223276篇
综合类   33325篇
现状与发展   3篇
一般理论   519篇
预防医学   120481篇
眼科学   33818篇
药学   105781篇
  1篇
中国医学   3852篇
肿瘤学   85473篇
  2021年   13207篇
  2019年   14245篇
  2018年   20785篇
  2017年   15115篇
  2016年   16473篇
  2015年   18488篇
  2014年   25465篇
  2013年   37796篇
  2012年   53116篇
  2011年   56119篇
  2010年   32341篇
  2009年   30009篇
  2008年   50853篇
  2007年   53807篇
  2006年   53734篇
  2005年   52129篇
  2004年   49326篇
  2003年   46884篇
  2002年   45118篇
  2001年   75467篇
  2000年   77458篇
  1999年   63739篇
  1998年   17395篇
  1997年   15682篇
  1996年   15826篇
  1995年   14982篇
  1994年   13552篇
  1993年   12718篇
  1992年   46681篇
  1991年   44193篇
  1990年   42193篇
  1989年   40114篇
  1988年   36648篇
  1987年   35820篇
  1986年   33352篇
  1985年   31683篇
  1984年   24127篇
  1983年   20261篇
  1982年   12325篇
  1981年   10885篇
  1979年   20983篇
  1978年   14754篇
  1977年   12255篇
  1976年   11532篇
  1975年   11848篇
  1974年   14252篇
  1973年   13835篇
  1972年   12884篇
  1971年   11747篇
  1970年   11170篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
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   
4.
5.
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   
6.
7.
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   
8.
9.
10.
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