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   33881篇
  免费   1280篇
  国内免费   1198篇
化学   9003篇
晶体学   1055篇
力学   600篇
综合类   159篇
数学   16930篇
物理学   5476篇
无线电   3136篇
  2023年   138篇
  2022年   294篇
  2021年   341篇
  2020年   416篇
  2019年   661篇
  2018年   688篇
  2017年   588篇
  2016年   678篇
  2015年   609篇
  2014年   1130篇
  2013年   2109篇
  2012年   1034篇
  2011年   2348篇
  2010年   2008篇
  2009年   2157篇
  2008年   2157篇
  2007年   2199篇
  2006年   1815篇
  2005年   1624篇
  2004年   1607篇
  2003年   1361篇
  2002年   1230篇
  2001年   873篇
  2000年   826篇
  1999年   714篇
  1998年   662篇
  1997年   545篇
  1996年   622篇
  1995年   553篇
  1994年   560篇
  1993年   428篇
  1992年   408篇
  1991年   267篇
  1990年   253篇
  1989年   251篇
  1988年   170篇
  1987年   205篇
  1986年   150篇
  1985年   225篇
  1984年   165篇
  1983年   83篇
  1982年   132篇
  1981年   166篇
  1980年   159篇
  1979年   130篇
  1978年   161篇
  1977年   144篇
  1976年   128篇
  1974年   57篇
  1973年   50篇
排序方式: 共有10000条查询结果,搜索用时 712 毫秒
111.
唐西林  刘仲奎 《数学杂志》1997,17(3):397-403
本文利用逆半群上的同余扩张,讨论了一类逆半群的亚直可约性,并刻划了这类逆半群的幂等元集的特征。  相似文献   
112.
For an arbitrary rational matrix function, not necessarily analytic at infinity, the existence of a right canonical Wiener-Hopf factorization is characterized in terms of a left canonical Wiener-Hopf factorization. Formulas for the factors in a right factorization are given in terms of the formulas for the factors in a given left factorization. All formulas are based on a special representation of a rational matrix function involving a quintet of matrices.  相似文献   
113.
Summary. We present a simple proof, based on modified logarithmic Sobolev inequalities, of Talagrand’s concentration inequality for the exponential distribution. We actually observe that every measure satisfying a Poincaré inequality shares the same concentration phenomenon. We also discuss exponential integrability under Poincaré inequalities and its consequence to sharp diameter upper bounds on spectral gaps. Received: 10 June 1996 / In revised form: 9 August 1996  相似文献   
114.
The paper deals with two closely related questions about the Bergman space of the unit disk. First, we investigate a special class of invariant subspaces of the Bergman space, namely, invariant subspaces induced by certain Hankel operators. We show that such spaces always have the co-dimension 1 or 2 property; and we determine exactly when such a space has the co-dimension 1 property. Second, we introduce the notion of inner spaces in the Bergman space and give several characterizations of when an inner space is maximal.Research supported by the National Science Foundation  相似文献   
115.
We consider the question of factorizability in tensor product spaces, and argue that the correlations associated with entangled states are even more problematic in the general case involving any tensor product of Hilbert spaces, than in the Einstein, Podolsky, and Rosen case with only two [1].  相似文献   
116.
An effective residual interaction between particles and holes for shell model calculations around 208Pb, derived from the interaction between free nucleons, is compared with the measured properties of proton-hole neutron states in 208Tl and the interaction between proton holes is adjusted to newly measured level energies in 206Hg. These interaction elements are particularly relevant for neutron-rich nuclei. The adjustment of two mixing elements reproduces the known γ-decay data in 208Tl. Received: 2 April 2002 / Accepted: 2 May 2002  相似文献   
117.
本对PN结反向物理特性,应用电子技术和计算机技术实现了对实验过程的控制和效据处理。  相似文献   
118.
A self-avoiding polygon (SAP) on a graph is an elementary cycle. Counting SAPs on the hypercubic lattice ℤ d withd≥2, is a well-known unsolved problem, which is studied both for its combinatorial and probabilistic interest and its connections with statistical mechanics. Of course, polygons on ℤ d are defined up to a translation, and the relevant statistic is their perimeter. A SAP on ℤ d is said to beconvex if its perimeter is “minimal”, that is, is exactly twice the sum of the side lengths of the smallest hyper-rectangle containing it. In 1984, Delest and Viennot enumerated convex SAPs on the square lattice [6], but no result was available in a higher dimension. We present an elementar approach to enumerate convex SAPs in any dimension. We first obtain a new proof of Delest and Viennot's result, which explains combinatorially the form of the generating function. We then compute the generating function for convex SAPs on the cubic lattice. In a dimension larger than 3, the details of the calculations become very cumbersome. However, our method suggests that the generating function for convex SAPs on ℤ d is always a quotient ofdifferentiably finite power series.  相似文献   
119.
120.
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