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   391511篇
  免费   4492篇
  国内免费   1767篇
化学   195624篇
晶体学   5184篇
力学   19632篇
综合类   27篇
数学   66889篇
物理学   110414篇
  2020年   2120篇
  2019年   2055篇
  2018年   12084篇
  2017年   11872篇
  2016年   9766篇
  2015年   4169篇
  2014年   4849篇
  2013年   14474篇
  2012年   14553篇
  2011年   23444篇
  2010年   13741篇
  2009年   14072篇
  2008年   18684篇
  2007年   20882篇
  2006年   12557篇
  2005年   12487篇
  2004年   11565篇
  2003年   10808篇
  2002年   9729篇
  2001年   10393篇
  2000年   8046篇
  1999年   6317篇
  1998年   5130篇
  1997年   4917篇
  1996年   5057篇
  1995年   4559篇
  1994年   4253篇
  1993年   4101篇
  1992年   4546篇
  1991年   4402篇
  1990年   4095篇
  1989年   3929篇
  1988年   4219篇
  1987年   3872篇
  1986年   3771篇
  1985年   5397篇
  1984年   5475篇
  1983年   4435篇
  1982年   4806篇
  1981年   4839篇
  1980年   4608篇
  1979年   4714篇
  1978年   4711篇
  1977年   4678篇
  1976年   4625篇
  1975年   4538篇
  1974年   4372篇
  1973年   4554篇
  1972年   2589篇
  1971年   1887篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
We show that there are close relations between extremal problems in dual Brunn-Minkowski theory and isotropic-type properties for some Borel measures on the sphere. The methods we use allow us to obtain similar results in the context of Firey-Brunn-Minkowski theory. We also study reverse inequalities for dual mixed volumes which are related with classical positions, such as ?-position or isotropic position.  相似文献   
102.
103.
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   
104.
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   
105.
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   
106.
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   
107.
The variational approach based on the covariant quantization method for the curved Einstein space is applied.  相似文献   
108.
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   
109.
110.
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   
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