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   2295709篇
  免费   175261篇
  国内免费   3370篇
耳鼻咽喉   32149篇
儿科学   77826篇
妇产科学   63545篇
基础医学   334334篇
口腔科学   63205篇
临床医学   208686篇
内科学   450901篇
皮肤病学   49873篇
神经病学   182636篇
特种医学   88431篇
外国民族医学   901篇
外科学   338385篇
综合类   49135篇
现状与发展   4篇
一般理论   890篇
预防医学   183559篇
眼科学   51905篇
药学   169946篇
  8篇
中国医学   4103篇
肿瘤学   123918篇
  2018年   24040篇
  2017年   18231篇
  2016年   20015篇
  2015年   22929篇
  2014年   31697篇
  2013年   48617篇
  2012年   66564篇
  2011年   70956篇
  2010年   41674篇
  2009年   39989篇
  2008年   67319篇
  2007年   72121篇
  2006年   71992篇
  2005年   70386篇
  2004年   68252篇
  2003年   65706篇
  2002年   64188篇
  2001年   105094篇
  2000年   108260篇
  1999年   91934篇
  1998年   25859篇
  1997年   23307篇
  1996年   23941篇
  1995年   22613篇
  1994年   21290篇
  1993年   19816篇
  1992年   73337篇
  1991年   71945篇
  1990年   69875篇
  1989年   67285篇
  1988年   62217篇
  1987年   61251篇
  1986年   57698篇
  1985年   55061篇
  1984年   41714篇
  1983年   35631篇
  1982年   21005篇
  1981年   19181篇
  1979年   38382篇
  1978年   27607篇
  1977年   23185篇
  1976年   21694篇
  1975年   23330篇
  1974年   27825篇
  1973年   27228篇
  1972年   25421篇
  1971年   23468篇
  1970年   22051篇
  1969年   20535篇
  1968年   18970篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
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   
64.
65.
66.
Bipolar disorder (BD) is a common psychiatric mood disorder affecting more than 1-2% of the general population of different European countries. Unfortunately, there is no objective laboratory-based test to aid BD diagnosis or monitor its progression, and little is known about the molecular basis of BD. Here, we performed a comparative proteomic study to identify differentially expressed plasma proteins in various BD mood states (depressed BD, manic BD, and euthymic BD) relative to healthy controls. A total of 10 euthymic BD, 20 depressed BD, 15 manic BD, and 20 demographically matched healthy control subjects were recruited. Seven high-abundance proteins were immunodepleted in plasma samples from the 4 experimental groups, which were then subjected to proteome-wide expression profiling by two-dimensional electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight/time-of-flight tandem mass spectrometry. Proteomic results were validated by immunoblotting and bioinformatically analyzed using MetaCore. From a total of 32 proteins identified with 1.5-fold changes in expression compared with healthy controls, 16 proteins were perturbed in BD independent of mood state, while 16 proteins were specifically associated with particular BD mood states. Two mood-independent differential proteins, apolipoprotein (Apo) A1 and Apo L1, suggest that BD pathophysiology may be associated with early perturbations in lipid metabolism. Moreover, down-regulation of one mood-dependent protein, carbonic anhydrase 1 (CA-1), suggests it may be involved in the pathophysiology of depressive episodes in BD. Thus, BD pathophysiology may be associated with early perturbations in lipid metabolism that are independent of mood state, while CA-1 may be involved in the pathophysiology of depressive episodes.  相似文献   
67.
68.
69.
70.
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   
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