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   25956篇
  免费   2172篇
  国内免费   1895篇
  2024年   41篇
  2023年   237篇
  2022年   669篇
  2021年   1304篇
  2020年   896篇
  2019年   1099篇
  2018年   1080篇
  2017年   816篇
  2016年   1129篇
  2015年   1558篇
  2014年   1851篇
  2013年   2014篇
  2012年   2303篇
  2011年   2129篇
  2010年   1343篇
  2009年   1233篇
  2008年   1422篇
  2007年   1248篇
  2006年   1068篇
  2005年   966篇
  2004年   801篇
  2003年   783篇
  2002年   662篇
  2001年   491篇
  2000年   441篇
  1999年   430篇
  1998年   238篇
  1997年   211篇
  1996年   209篇
  1995年   192篇
  1994年   183篇
  1993年   124篇
  1992年   179篇
  1991年   128篇
  1990年   121篇
  1989年   84篇
  1988年   67篇
  1987年   51篇
  1986年   40篇
  1985年   42篇
  1984年   18篇
  1983年   20篇
  1982年   19篇
  1981年   9篇
  1980年   7篇
  1979年   7篇
  1978年   7篇
  1975年   6篇
  1973年   6篇
  1967年   5篇
排序方式: 共有10000条查询结果,搜索用时 640 毫秒
31.
32.
33.
In this article, we designed and synthesized two series of matrine analogs with ring-opening in the lactam portion of the molecule. Our in vitro cytotoxicity study showed that analog N-(3-bromophenyl)-4-[(1R,3aS,10aR,10bS)-decahydro-1H,4H-pyrido[3,2,1-ij][1,6]naphthyridin-1-yl]butanamide ( B11 ) with a meta-bromide on the phenyl ring displayed the best antiproliferative activity. Moreover, B11 induced cell cycle arrest in G1 phase and cell apoptosis in a dose-dependent manner in A549 cells. Molecular modeling revealed that B11 achieved a higher docking score compared to its precursor tert-butyl (1R,3aS,10aR,10bS)-1-[4-(3-bromoanilino)-4-oxobutyl]octahydro-1H,4H-pyrido[3,2,1-ij][1,6]naphthyridine-2(3H)-carboxylate ( A11 , an analog of B11 with a Boc group) and parent compound matrine, possibly because B11 formed a hydrogen bond with SER91 and a halogen bond with GLN320 on the binding site of annexin A2. Overall, we discovered the potential anticancer lead compound B11 , which can be used for further study both in vitro and in vivo.  相似文献   
34.
35.
36.
The purpose of this review is to provide an overview of the effects of adenovirus and influenza virus infections on obesity in various experimental models. We reviewed studies that were conducted within the past 10 years and were related to virus infection and obesity prevalence. Here, we discuss a different causal relationship between adenovirus and influenza infections with obesity. Adenovirus infection can cause obesity, whereas obesity can be a risk factor for increasing influenza virus infection and increases the risk of morbidity and mortality. The prevalence of obesity due to adenovirus infections may be due to an increase in glucose uptake and reduction in lipolysis caused by an increase in corticosterone secretion. Adenovirus infections may lead to increases in appetite by decreasing norepinephrine and leptin levels and also cause immune dysfunction. The relationship between obesity and influenza virus infection could be summarized by the following features: decreases in memory T-cell functionality and interferon (IFN)-α, IFN-β, and IFN-γ mRNA expression, increases in viral titer and infiltration, and impaired dendritic cell function in obese individuals. Moreover, leptin resistance may play an important role in increasing influenza virus infections in obese individuals. In conclusion, prevention of adenovirus infections could be a good approach for reducing obesity prevalence, and prevention of obesity could reduce influenza virus infections from the point of view of viral infections and obesity.  相似文献   
37.
Journal of Plant Biochemistry and Biotechnology - The dried buds of Lonicera hypoglauca Miq. have antipyretic, antidotal and anti-inflammatory properties and as Flos lonicerae are widely used in...  相似文献   
38.
This paper describes a generic algorithm for finding restrictionsites within DNA sequences. The ‘genericity’ ofthe algorithm is made possible through the use of set theory.Basic elements of DNA sequences, i.e. nucleotides (bases), arerepresented in sets, and DNA sequences, whether specific, ambiguousor even protein-coding, are represented as sequences of thosesets. The set intersection operation demonstrates its abilityto perform pattern-matching correctly on various DNA sequences.The performance analysis showed that the degree of complexityof the pattern matching is reduced from exponential to linear.An example is given to show the actual and potential restrictionsites, derived by the generic algorithm, in the DNA sequencetemplate coding for a synthetic calmodulin. Received on October 2, 1990; accepted on December 18, 1990  相似文献   
39.
40.
Aorta smooth myosin contains two types of light chain, LC20 and LC17, which fold together with the N-terminal region of each heavy chain to form the globular head region of myosin. We demonstrate an altered conformation of LC20 after its separation from heavy chain by high concentrations of urea, on the basis of the following evidende: 1) A polyclonal antibody against LC20 was not able to recognize this conformationally altered form; 2) Myosin reconstituted from heavy chains and urea-dissociated light chains exhibited extremely low ATPase activity. Circular dichroism unfolding profiles showed that light chains dissociated from heavy chains by SDS appeared to be more stable than those generated by urea dissociation.  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