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   67791篇
  免费   4595篇
  国内免费   14篇
  2023年   370篇
  2022年   541篇
  2021年   1131篇
  2020年   880篇
  2019年   1092篇
  2018年   1758篇
  2017年   1537篇
  2016年   2176篇
  2015年   2933篇
  2014年   3103篇
  2013年   4034篇
  2012年   4688篇
  2011年   4372篇
  2010年   2869篇
  2009年   2506篇
  2008年   3437篇
  2007年   3350篇
  2006年   3236篇
  2005年   2723篇
  2004年   2722篇
  2003年   2426篇
  2002年   2285篇
  2001年   1738篇
  2000年   1638篇
  1999年   1336篇
  1998年   687篇
  1997年   509篇
  1996年   493篇
  1995年   494篇
  1994年   396篇
  1993年   370篇
  1992年   775篇
  1991年   721篇
  1990年   651篇
  1989年   647篇
  1988年   574篇
  1987年   584篇
  1986年   519篇
  1985年   497篇
  1984年   412篇
  1983年   376篇
  1982年   293篇
  1979年   393篇
  1978年   265篇
  1975年   254篇
  1974年   307篇
  1973年   306篇
  1972年   271篇
  1970年   253篇
  1969年   255篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
111.
112.
A sensitive and reliable method to determine the stereochemical composition of 3-phosphoglyceric acid is presented. Results obtained with this method show that 3-phosphoglyceric acid formed in the ribulose-1,5-bisphosphate carboxylase reaction is a mixture of 10% L-3-PGA and 90% D-3-PGA.  相似文献   
113.
114.
115.
This study focuses on assessing the reproduction mode of an important model species for evolutionary and behavioural ecology by using digital image analysis: the European bitterling Rhodeus amarus (Bloch, 1782). Specifications of mode of reproduction were determined using oocyte size distribution, seasonal dynamics in mean oocyte diameter and total number of oocytes in ovary samples gained from April to July 2007. The rapid oocyte count was enabled by using lucia image analysis software, which also provided measurement and colour estimations of oocytes. Bitterling ovaries showed features typical for indeterminate spawners, i.e. a continuous distribution of oocyte size over the reproductive season and recruitment of new pre‐vitelogenic oocytes in the second half of the reproductive season. These results are consistent with the view that the European bitterling is a batch spawning fish with indeterminate fecundity.  相似文献   
116.
The peptidic sequence (Sarcosine-1-Isoleucine-8)-Angiotensin II has been demonstrated to be an in vitro specific and competitive antagonist of the Angiotensin II action. The present results show it to be a competitive antagonist also in vivo since pA2 values are similar, always reaches a 100% response on increasing the Angiotensin II dose, and when relating log (DR-1) and log dose of agonist, the slope is very near to one (0.925).  相似文献   
117.
118.
The effects produced on bacteriorhodopsin by low concentrations of several detergents have been studied by absorption and fourth-derivative spectrophotometry. Sodium dodecyl sulfate induces the appearance of the blue form of bacteriorhodopsin (λmax = 600 nm) at pH values up to 7.0 in a reversible manner. The apparent pK of the purple-to-blue transition raised with increasing concentration of SDS. Of the other detergents tested, only sodium dodecyl-N-sarcosinate showed a slight red-shift of the absorption band to 580 nm, whereas sodium taurocholate, Triton X-100 and cetyltrimethylammonium bromide did not favour the appearance of the blue form. The effect of SDS was found to be consistent with a localized conformational change that moves away the counter-ion of the protonated Schiff base.  相似文献   
119.
120.
Herein, we disclose the discovery and optimization of 2-piperidin-4-yl-acetamide derivatives as MCH-R1 antagonists. Structural investigation of piperidin-4-yl-amide and piperidin-4-yl-ureas identified 2-piperidin-4-yl-acetamide-based MCH-R1 antagonists with outstanding in vivo efficacy but flawed with high affinity towards the hERG potassium channel. While existing hERG SAR information was employed to discover highly potent MCH-R1 antagonists with minimized hERG inhibition, additional hurdles prevented their subsequent clinical exploration.  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