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   314812篇
  免费   3763篇
  国内免费   1091篇
化学   170962篇
晶体学   4463篇
力学   13031篇
综合类   7篇
数学   36291篇
物理学   94912篇
  2020年   1983篇
  2019年   1958篇
  2018年   1967篇
  2017年   1877篇
  2016年   3870篇
  2015年   3238篇
  2014年   4433篇
  2013年   14005篇
  2012年   10751篇
  2011年   13384篇
  2010年   8283篇
  2009年   8266篇
  2008年   12356篇
  2007年   12594篇
  2006年   12226篇
  2005年   11166篇
  2004年   10050篇
  2003年   8859篇
  2002年   8714篇
  2001年   10116篇
  2000年   7722篇
  1999年   6121篇
  1998年   4902篇
  1997年   4739篇
  1996年   4777篇
  1995年   4369篇
  1994年   4119篇
  1993年   3948篇
  1992年   4441篇
  1991年   4299篇
  1990年   4017篇
  1989年   3835篇
  1988年   4127篇
  1987年   3789篇
  1986年   3688篇
  1985年   5324篇
  1984年   5412篇
  1983年   4382篇
  1982年   4757篇
  1981年   4799篇
  1980年   4551篇
  1979年   4673篇
  1978年   4675篇
  1977年   4654篇
  1976年   4600篇
  1975年   4519篇
  1974年   4364篇
  1973年   4532篇
  1972年   2573篇
  1971年   1881篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Sauer, Shelah, Vapnik and Chervonenkis proved that if a set system on n vertices contains many sets, then the set system has full trace on a large set. Although the restriction on the size of the groundset cannot be lifted, Frankl and Pach found a trace structure that is guaranteed to occur in uniform set systems even if we do not bound the size of the groundset. In this note we shall give three sequences of structures such that every set system consisting of sufficiently many sets contains at least one of these structures with many sets.  相似文献   
92.
Using the theory of noncommutative symmetric functions, we introduce the higher order peak algebras (Sym(N))N≥1, a sequence of graded Hopf algebras which contain the descent algebra and the usual peak algebra as initial cases (N=1 and N=2). We compute their Hilbert series, introduce and study several combinatorial bases, and establish various algebraic identities related to the multisection of formal power series with noncommutative coefficients. Received November 19, 2004  相似文献   
93.
Summary This paper presents some applications of cyclic voltammetry at the interface of two immiscible electrolyte solutions by means of an experimental set-up described in a former publication. When using special sample preparation good results are obtained for the determination of iodide and quinine in pharmaceutical products as well as for the determination of quinine in tonic water and dodecylsulfate in a tooth-salt.

Herrn Prof. Dr. Günther Tölg zum 60. Geburtstag gewidmet  相似文献   
94.
To further evaluate the causality between endogenous pyrogen (EP)-induced fever and cyclic adenosine-3',5'-monophosphate (cyclic AMP) level, the effects of sodium salicylate (SS) on the febrile response and increased levels of cyclic AMP in both cerebrospinal fluid (c.s.f.) and plasma during EP-induced fever in rabbits were observed. The results suggest that cyclic AMP is probably involved in the central mediation of EP-induced fever and that increased concentration of cyclic AMP in c.s.f. associated with EP-induced fever is not the result of temperature elevation but appears to be caused by the increased synthesis in the central nervous system. In addition it is confirmed that blood is impossibly a contributory source of increased cyclic AMP in c.s.f. during EP fever, and that SS may act subsequent to the increase in cyclic AMP.  相似文献   
95.
The variational approach based on the covariant quantization method for the curved Einstein space is applied.  相似文献   
96.
The precision of intensity modulated fiber optic sensor systems mainly is restricted by the attenuation characteristics of the analog fiber optical data link. Special encoding and referencing schemes are used to overcome this data link dependence. In this paper encoding and referencing principles for optical sensors are outlined and compared. Especially the two wavelengths referencing and the optical delay line processing techniques are discussed in more detail and results are presented.  相似文献   
97.
98.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive projections in Dedekind complete vector lattices and f-algebras. AMS Classification: 47B65, 46A40, 06F25  相似文献   
99.
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