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   2470265篇
  免费   187227篇
  国内免费   5528篇
耳鼻咽喉   35051篇
儿科学   78687篇
妇产科学   71592篇
基础医学   347681篇
口腔科学   71034篇
临床医学   216053篇
内科学   487233篇
皮肤病学   57224篇
神经病学   201164篇
特种医学   96138篇
外国民族医学   879篇
外科学   376272篇
综合类   57674篇
现状与发展   8篇
一般理论   864篇
预防医学   184382篇
眼科学   57758篇
药学   180189篇
  5篇
中国医学   5443篇
肿瘤学   137689篇
  2018年   25302篇
  2017年   19642篇
  2016年   21995篇
  2015年   24741篇
  2014年   35045篇
  2013年   52758篇
  2012年   70452篇
  2011年   74582篇
  2010年   44137篇
  2009年   42517篇
  2008年   70159篇
  2007年   75179篇
  2006年   76167篇
  2005年   73913篇
  2004年   71062篇
  2003年   68277篇
  2002年   66722篇
  2001年   119211篇
  2000年   122298篇
  1999年   102664篇
  1998年   28459篇
  1997年   25835篇
  1996年   25377篇
  1995年   24070篇
  1994年   22179篇
  1993年   20704篇
  1992年   78676篇
  1991年   75604篇
  1990年   73430篇
  1989年   70873篇
  1988年   65630篇
  1987年   64241篇
  1986年   61110篇
  1985年   57984篇
  1984年   43962篇
  1983年   37199篇
  1982年   22558篇
  1981年   20339篇
  1979年   40532篇
  1978年   28795篇
  1977年   24582篇
  1976年   22558篇
  1975年   24658篇
  1974年   29295篇
  1973年   28520篇
  1972年   27048篇
  1971年   24915篇
  1970年   23757篇
  1969年   22530篇
  1968年   21261篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
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   
54.
55.
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   
56.
57.
58.
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   
59.
60.
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