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   1843100篇
  免费   136212篇
  国内免费   3734篇
耳鼻咽喉   24171篇
儿科学   60307篇
妇产科学   50964篇
基础医学   279315篇
口腔科学   48072篇
临床医学   167260篇
内科学   358055篇
皮肤病学   42766篇
神经病学   142735篇
特种医学   69913篇
外国民族医学   512篇
外科学   275027篇
综合类   38821篇
现状与发展   5篇
一般理论   582篇
预防医学   142664篇
眼科学   41708篇
药学   133308篇
  2篇
中国医学   4184篇
肿瘤学   102675篇
  2019年   14560篇
  2018年   20785篇
  2017年   15636篇
  2016年   17953篇
  2015年   20030篇
  2014年   27896篇
  2013年   41351篇
  2012年   57243篇
  2011年   61589篇
  2010年   36042篇
  2009年   33748篇
  2008年   56692篇
  2007年   60694篇
  2006年   60773篇
  2005年   58830篇
  2004年   56503篇
  2003年   54033篇
  2002年   52180篇
  2001年   89220篇
  2000年   91229篇
  1999年   75527篇
  1998年   21096篇
  1997年   18819篇
  1996年   18944篇
  1995年   18017篇
  1994年   16278篇
  1993年   15503篇
  1992年   57203篇
  1991年   56491篇
  1990年   54755篇
  1989年   52712篇
  1988年   48373篇
  1987年   47511篇
  1986年   44174篇
  1985年   42202篇
  1984年   31922篇
  1983年   26929篇
  1982年   15816篇
  1979年   28601篇
  1978年   20218篇
  1977年   16641篇
  1976年   16319篇
  1975年   17649篇
  1974年   20746篇
  1973年   20029篇
  1972年   18680篇
  1971年   17257篇
  1970年   16301篇
  1969年   15038篇
  1968年   14280篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
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   
43.
44.
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   
45.
46.
47.
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   
48.
49.
50.
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