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   2701104篇
  免费   209646篇
  国内免费   4929篇
耳鼻咽喉   37260篇
儿科学   83509篇
妇产科学   69322篇
基础医学   373426篇
口腔科学   72459篇
临床医学   243006篇
内科学   529877篇
皮肤病学   51149篇
神经病学   232797篇
特种医学   111098篇
外国民族医学   899篇
外科学   413957篇
综合类   60515篇
现状与发展   2篇
一般理论   1120篇
预防医学   218471篇
眼科学   62202篇
药学   197767篇
  5篇
中国医学   5222篇
肿瘤学   151616篇
  2019年   20733篇
  2018年   48936篇
  2017年   38290篇
  2016年   42942篇
  2015年   28158篇
  2014年   39998篇
  2013年   59553篇
  2012年   86807篇
  2011年   104071篇
  2010年   66707篇
  2009年   58227篇
  2008年   98600篇
  2007年   106300篇
  2006年   85840篇
  2005年   85755篇
  2004年   83925篇
  2003年   82028篇
  2002年   78803篇
  2001年   114265篇
  2000年   118220篇
  1999年   100041篇
  1998年   30037篇
  1997年   27351篇
  1996年   26922篇
  1995年   26024篇
  1994年   24443篇
  1993年   22708篇
  1992年   80203篇
  1991年   77195篇
  1990年   74238篇
  1989年   71410篇
  1988年   66389篇
  1987年   65295篇
  1986年   61832篇
  1985年   58933篇
  1984年   44844篇
  1983年   38162篇
  1982年   23625篇
  1981年   20917篇
  1979年   41650篇
  1978年   29330篇
  1977年   24594篇
  1976年   23143篇
  1975年   24153篇
  1974年   29861篇
  1973年   28235篇
  1972年   26347篇
  1971年   24280篇
  1970年   22838篇
  1969年   21157篇
排序方式: 共有10000条查询结果,搜索用时 25 毫秒
71.
72.
73.
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   
74.
Hepatic NADPH-cytochrome P450 oxidoreductase null (HRN?) mice exhibit normal hepatic and extrahepatic biotransformation enzyme activities when compared to wild-type (WT) mice, but express no functional hepatic cytochrome P450 activities. When incubated in vitro with [14C]-diclofenac, liver microsomes from WT mice exhibited extensive biotransformation to oxidative and glucuronide metabolites and covalent binding to proteins was also observed. In contrast, whereas glucuronide conjugates and a quinone-imine metabolite were formed when [14C]-diclofenac was incubated with HRN? mouse liver, only small quantities of P450-derived oxidative metabolites were produced in these samples and covalent binding to proteins was not observed. Livers from vehicle-treated HRN? mice exhibited enhanced lipid accumulation, bile duct proliferation, hepatocellular degeneration and necrosis and inflammatory cell infiltration, which were not present in livers from WT mice. Elevated liver-derived alanine aminotransferase, glutamate dehydrogenase and alkaline phosphatase activities were also observed in plasma from HRN? mice. When treated orally with diclofenac for 7 days, at 30 mg/kg/day, the severities of the abnormal liver histopathology and plasma liver enzyme findings in HRN? mice were reduced markedly. Oral diclofenac administration did not alter the liver histopathology or elevate plasma enzyme activities of WT mice. These findings indicate that HRN? mice are valuable for exploration of the role played by hepatic P450s in drug biotransformation, but poorly suited to investigations of drug-induced liver toxicity. Nevertheless, studies in HRN? mice could provide novel insights into the role played by inflammation in liver injury and may aid the evaluation of new strategies for its treatment.  相似文献   
75.
76.
77.
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   
78.
79.
80.
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