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   2070268篇
  免费   165180篇
  国内免费   4799篇
耳鼻咽喉   28890篇
儿科学   65725篇
妇产科学   60120篇
基础医学   295585篇
口腔科学   58094篇
临床医学   184359篇
内科学   405183篇
皮肤病学   46555篇
神经病学   170784篇
特种医学   80566篇
外国民族医学   626篇
外科学   313893篇
综合类   52380篇
现状与发展   4篇
一般理论   704篇
预防医学   162995篇
眼科学   48220篇
药学   148764篇
  1篇
中国医学   4465篇
肿瘤学   112334篇
  2018年   21879篇
  2017年   16797篇
  2016年   19024篇
  2015年   21590篇
  2014年   30684篇
  2013年   46188篇
  2012年   62430篇
  2011年   65874篇
  2010年   38671篇
  2009年   36873篇
  2008年   61336篇
  2007年   65504篇
  2006年   65936篇
  2005年   64091篇
  2004年   61708篇
  2003年   59182篇
  2002年   57149篇
  2001年   96832篇
  2000年   99121篇
  1999年   82838篇
  1998年   24085篇
  1997年   21808篇
  1996年   21750篇
  1995年   20647篇
  1994年   19082篇
  1993年   17896篇
  1992年   64790篇
  1991年   62342篇
  1990年   60292篇
  1989年   57638篇
  1988年   53474篇
  1987年   52343篇
  1986年   49296篇
  1985年   47302篇
  1984年   36324篇
  1983年   30806篇
  1982年   19195篇
  1981年   17331篇
  1979年   34086篇
  1978年   24270篇
  1977年   20274篇
  1976年   18920篇
  1975年   19854篇
  1974年   24355篇
  1973年   23471篇
  1972年   22191篇
  1971年   20351篇
  1970年   19402篇
  1969年   18370篇
  1968年   16954篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
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   
12.
13.
14.
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   
15.
16.
17.
18.
19.
20.
AimsWe previously showed that the protective effects of endothelial progenitor cells (EPCs)‐released exosomes (EPC‐EXs) on endothelium in diabetes. However, whether EPC‐EXs are protective in diabetic ischemic stroke is unknown. Here, we investigated the effects of EPC‐EXs on diabetic stroke mice and tested whether miR‐126 enriched EPC‐EXs (EPC‐EXsmiR126) have enhanced efficacy.MethodsThe db/db mice subjected to ischemic stroke were intravenously administrated with EPC‐EXs 2 hours after ischemic stroke. The infarct volume, cerebral microvascular density (MVD), cerebral blood flow (CBF), neurological function, angiogenesis and neurogenesis, and levels of cleaved caspase‐3, miR‐126, and VEGFR2 were measured on day 2 and 14.ResultsWe found that (a) injected EPC‐EXs merged with brain endothelial cells, neurons, astrocytes, and microglia in the peri‐infarct area; (b) EPC‐EXsmiR126 were more effective than EPC‐EXs in decreasing infarct size and increasing CBF and MVD, and in promoting angiogenesis and neurogenesis as well as neurological functional recovery; (c) These effects were accompanied with downregulated cleaved caspase‐3 on day 2 and vascular endothelial growth factor receptor 2 (VEGFR2) upregulation till day 14.ConclusionOur results indicate that enrichment of miR126 enhanced the therapeutic efficacy of EPC‐EXs on diabetic ischemic stroke by attenuating acute injury and promoting neurological function recovery.  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