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   1794篇
  免费   139篇
  国内免费   133篇
化学   655篇
晶体学   3篇
力学   22篇
综合类   9篇
数学   1215篇
物理学   162篇
  2023年   15篇
  2022年   32篇
  2021年   24篇
  2020年   38篇
  2019年   50篇
  2018年   41篇
  2017年   32篇
  2016年   54篇
  2015年   56篇
  2014年   73篇
  2013年   153篇
  2012年   60篇
  2011年   70篇
  2010年   76篇
  2009年   96篇
  2008年   123篇
  2007年   115篇
  2006年   102篇
  2005年   105篇
  2004年   77篇
  2003年   68篇
  2002年   61篇
  2001年   63篇
  2000年   50篇
  1999年   36篇
  1998年   45篇
  1997年   32篇
  1996年   23篇
  1995年   18篇
  1994年   22篇
  1993年   16篇
  1992年   10篇
  1991年   11篇
  1990年   20篇
  1989年   9篇
  1988年   5篇
  1987年   13篇
  1986年   4篇
  1985年   13篇
  1984年   11篇
  1983年   12篇
  1982年   20篇
  1981年   10篇
  1980年   17篇
  1979年   17篇
  1978年   11篇
  1977年   17篇
  1976年   22篇
  1975年   4篇
  1974年   7篇
排序方式: 共有2066条查询结果,搜索用时 15 毫秒
131.
一个择一定理及对广义凸规划的应用   总被引:7,自引:1,他引:7  
本文在实线性空间中得出了广义凸函数的择一定理 ,利用这一定理 ,我们获得广义凸规划的最优性条件  相似文献   
132.
交换群层的正合序列与同态定理   总被引:1,自引:0,他引:1  
在交换群层(简称层)中给出了层的单(满)同态核与上核的泛性定理及正合交换图的一系列结论,进而证明了交换群层的同态(同构)定理。  相似文献   
133.
134.
F. Laytimi  W. Nahm 《代数通讯》2020,48(2):783-791
Abstract

The main result of this paper is that tensor products of semiample vector bundles over compact complex manifolds are semiample. An easy proof yields the analogous result for direct sums. We also show that tensor products of semiample vector bundles with k-ample vector bundles in the sense of Sommese are k-ample. On the other hand, we show that it is not generally true that tensor products of nef and k-ample vector bundles for positive k are still k-ample. Results of Sommese on k-ampleness are consequently strengthened. As an application of our main theorem we extend to k-ample the vanishing theorem of Ein-Lazarsfeld.  相似文献   
135.
In the present paper, we consider the classical Widder transform, the Hν-transform, the Kν-transform, and the Yν-transform. Some identities involving these transforms and many others are given. By making use of these identities, a number of new Parseval-Goldstein type identities are obtained for these and other well-known integral transforms.  相似文献   
136.
We provide a characterization of the classical point-line designs PG1(n,q), where n?3, among all non-symmetric 2-(v,k,1)-designs as those with the maximal number of hyperplanes. As an application of this result, we characterize the classical quasi-symmetric designs PGn−2(n,q), where n?4, among all (not necessarily quasi-symmetric) designs with the same parameters as those having line size q+1 and all intersection numbers at least qn−4+?+q+1. Finally, we also give an explicit lower bound for the number of non-isomorphic designs having the same parameters as PG1(n,q); in particular, we obtain a new proof for the known fact that this number grows exponentially for any fixed value of q.  相似文献   
137.
Given an observation of the uniform empirical process αn, its functional increments αn(u+an⋅)−αn(u) can be viewed as a single random process, when u is distributed under the Lebesgue measure. We investigate the almost sure limit behaviour of the multivariate versions of these processes as n and an0. Under mild conditions on an, a convergence in distribution and functional limit laws are established. The proofs rely on a new extension of the usual Poissonisation tools for the local empirical process.  相似文献   
138.
We prove a theorem of existence, uniqueness, and continuous dependence for a linear hyperbolic system with Darboux-type conditions under assumptions on the coefficients, which are in a sense the most general possible. Moreover, an application of this result to an optimal control problem is given.  相似文献   
139.
We further develop a forcing notion known as Coding with Perfect Trees and show that this poset preserves, in a strong sense, definable P-points, definable tight MAD families and definable selective independent families. As a result, we obtain a model in which a=u=i=?1<2?0=?2, each of a, u, i has a Π11 witness and there is a Δ31 well-order of the reals. Note that both the complexity of the witnesses of the above combinatorial cardinal characteristics, as well as the complexity of the well-order are optimal. In addition, we show that the existence of a Δ31 well-order of the reals is consistent with c=?2 and each of the following: a=u<i, a=i<u, a<u=i, where the smaller cardinal characteristics have co-analytic witnesses.Our methods allow the preservation of only sufficiently definable witnesses, which significantly differs from other preservation results of this type.  相似文献   
140.
In [3], Poonen and Slavov recently developed a novel approach to Bertini irreducibility theorems over an arbitrary field, based on random hyperplane slicing. In this paper, we extend their work by proving an analogous bound for the dimension of the exceptional locus in the setting of linear subspaces of higher codimensions.  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