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   703801篇
  免费   78010篇
  国内免费   340篇
  2018年   6216篇
  2016年   8514篇
  2015年   11364篇
  2014年   13374篇
  2013年   18705篇
  2012年   21195篇
  2011年   21511篇
  2010年   14772篇
  2009年   13589篇
  2008年   19482篇
  2007年   20386篇
  2006年   18976篇
  2005年   18283篇
  2004年   17995篇
  2003年   17094篇
  2002年   16990篇
  2001年   32053篇
  2000年   32254篇
  1999年   25348篇
  1998年   8586篇
  1997年   9032篇
  1996年   8480篇
  1995年   7961篇
  1994年   7784篇
  1993年   7674篇
  1992年   21129篇
  1991年   20760篇
  1990年   20239篇
  1989年   19449篇
  1988年   18377篇
  1987年   17368篇
  1986年   16137篇
  1985年   15957篇
  1984年   13156篇
  1983年   11411篇
  1982年   8644篇
  1981年   7722篇
  1980年   7340篇
  1979年   12659篇
  1978年   9807篇
  1977年   8957篇
  1976年   8380篇
  1975年   9321篇
  1974年   10150篇
  1973年   9964篇
  1972年   9253篇
  1971年   8241篇
  1970年   7378篇
  1969年   7150篇
  1968年   6731篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
It has been found by gel-penetrating chromatography and quantitative 13C NMR spectroscopy that mechanochemical processing of arabinogalactan isolated from the wood of the Siberian larch changes the molecular mass distribution, monosaccharide composition, and the degree of branching of its macromolecules. This is due to the partial destruction of polysaccharide macromolecules and subsequent recombination of resulting fragments. The intensity of these processes depends on the conditions of mechanochemical processing. Based on the data of IR and 13C NMR spectra, the conclusion has been drawn that no functionalization of arabinogalactan macromolecules occurs under these conditions. The toxicopharmacological properties of mechanically processed arabinogalactan have been studied. Its acute toxicity is >5000 mg/kg.  相似文献   
92.
93.
Protein metal-binding sites.   总被引:2,自引:0,他引:2  
Metal ions have a role in a variety of important functions in proteins including protein folding, assembly, stability, conformational change, and catalysis. The presence or absence of a given metal ion is crucial to the conformation or activity of over one third of all proteins. Recent developments have been made in the understanding and design of metal-binding sites in proteins, an important and rapidly advancing area of protein engineering.  相似文献   
94.
Experiments were made on rabbit fed an atherogenic diet (0.5 g/kg cholesterol) singly for 15 and 24 h and repeatedly for 3, 9 and 30 days. At early stages of lipid metabolism distress the interrelationship was established between blood rheological disorders and microcirculatory abnormalities. The dependence of the initial reaction of some rheological characteristics on their initial level was marked.  相似文献   
95.
96.
Electron microscopy of the adrenal medulla and cortex during the intermediate period of endotoxin shock has revealed severe destructive changes in parenchymal cells. These changes are the reason for synthetic, secretory and trophic disturbances of glandular functions. Ultrastructural lesions indicate that stress exposure exceeds the adaptive capacity of cells, the majority of which are exhausted and killed.  相似文献   
97.
98.
Synthesis of prenylquinones in chloroplasts   总被引:3,自引:0,他引:3  
  相似文献   
99.
The Thom gradient model of morphogenesis poses the followinga posteriori problem: “From the observed morphology of a given natural process (effect) determine the dynamics of the process (cause)”. In this paper we consider the classicala priori problem: “Given the cause (dynamics) determine the effect (resultant morphology)”. We find that in biochemical processes the mechanisms for energy activation, energy-matter interaction and energy dissipation determine the dynamics. Furthermore there exists basic energy mechanisms which drive the equilibrium states through the elementary catastrophes of Thom. A comparison with current theories shows that our models describe open ecological food chains and their dynamical systems generalize the equations of organisation posed by M. Eigen. Work supported by a Research Associateship of the International Centre for Theoretical Physics, P.O.B. 586, Miramare, 34100 Trieste, Italy.  相似文献   
100.
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