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   443篇
  免费   15篇
  国内免费   93篇
化学   31篇
晶体学   4篇
力学   8篇
综合类   14篇
数学   476篇
物理学   18篇
  2023年   4篇
  2022年   5篇
  2021年   4篇
  2020年   9篇
  2019年   6篇
  2018年   8篇
  2017年   11篇
  2016年   9篇
  2015年   5篇
  2014年   15篇
  2013年   28篇
  2012年   13篇
  2011年   19篇
  2010年   17篇
  2009年   23篇
  2008年   40篇
  2007年   36篇
  2006年   41篇
  2005年   25篇
  2004年   32篇
  2003年   31篇
  2002年   24篇
  2001年   21篇
  2000年   14篇
  1999年   21篇
  1998年   20篇
  1997年   22篇
  1996年   14篇
  1995年   2篇
  1994年   11篇
  1993年   3篇
  1992年   2篇
  1991年   2篇
  1990年   4篇
  1989年   2篇
  1985年   5篇
  1984年   1篇
  1982年   1篇
  1974年   1篇
排序方式: 共有551条查询结果,搜索用时 31 毫秒
81.
MORPHIC MODULES     
《代数通讯》2013,41(8):2629-2647
A module M is called morphic if M/M α ? ker(α) for all endomorphisms α in end(M), and a ring R is called a left morphic ring if RR is a morphic module. We consider the open question when the matrix ring Mn(R) is left morphic by relating it to when Rn is morphic as a left R-module. More generally, we investigate when M being morphic implies that end(M) is left morphic, and conversely. Finally, we relate the morphic condition to internal cancellation in the module.  相似文献   
82.
In 1955 N. Kuiper and J. Nash proved that given a C embeddingF of a C Riemannian n -manifold (M,g) in E n+1 which is short in the sense that the metric induced by F is less thang, there is a C 1 isometric embedding which is arbitrarily C 0-close to F. We extend the Nash--Kuiper result for compact M to the case of deformations. In other words, we prove that given a continuous family of short C embeddings ( ) of a compact Riemannian n-manifold M , there is an isometric deformation through C 1 embeddings which is C 0 -close to F. With more assumptions which are typically met in practice, this result is shown to hold in the more difficult case where F(s) is short for s>0 andF(0) is isometric. We use this to prove that if a C convex hypersurface is sufficiently close to being planar in an average sense (e.g. an oblate spheroid in E 3 with axis ratio more than , then it admits an isometric deformation which increases the enclosed volume.  相似文献   
83.
The antisymmetry of proton configurations was studied for the hexagonal water rings with different conformations. The change in the direction of all hydrogen bonds was used as an additional symmetry operation. The ring configuration energies were calculated using the intermolecular interaction potentials. For different ring conformations, the relationships between antisymmetry and energy were analyzed and compared.  相似文献   
84.
超格的商结构   总被引:1,自引:0,他引:1  
通过引入超格的强闭集、上半补超格、数量上界单位元等概念,引出超格上的等价关系.构造数量上界单位集,在此基础上进一步研究超格的一些性质.商代数结构定理的建立对于完善超格的商结构具有实际意义.  相似文献   
85.
本文我们决定了一类Block型李代数$\BB$在同构意义下的分类和中心扩张, 其中$q$是一个非零复数. 我们的结果推广了以前的一些结果.  相似文献   
86.
87.
The molecular structure of conformational isomorphs given by X-ray diffraction for racemic and enantiomeric atenolol were optimized at the HF/6-31G* level of theory and the infrared spectra of the structure were calculated. These spectra are used to characterize the differences between the various atenolol conformers. The spectra of the (R,S)- and S-atenolol solid forms were recorded and the bands corresponding to the functional groups identified with the aid of the calculated spectra, fitting analysis, temperature effect and H/D isotopic exchange. Particular attention was paid to the stretch vibration modes of the functional groups present in the atenolol.  相似文献   
88.
Suppose is an infinite-dimensional operator space and is a positive integer. We prove that for every there exists an operator space such that the formal identity map is a complete isomorphism, is an isometry, and . This provides a non-commutative counterpart to a recent result of W. Johnson and E. Odell.

  相似文献   

89.
Let be a surjective operator between two uniform algebras with . We show that if satisfies the peripheral multiplicativity condition for all , where is the peripheral spectrum of , then is an isometric algebra isomorphism from onto . One of the consequences of this result is that any surjective, unital, and multiplicative operator that preserves the peripheral ranges of algebra elements is an isometric algebra isomorphism. We describe also the structure of general, not necessarily unital, surjective and peripherally multiplicative operators between uniform algebras.

  相似文献   

90.
To any ordered set with a universally maximal element, a semigroup of its transformations with some natural properties that defines the ordered set up to an isomorphism is assigned. The system of such transformation semigroups is proved to be the minimal element in the set of all defining systems of transformation semigroups with respect to the following ordering: one system precedes another if for each ordered set from the class in question, the semigroup of its transformation belonging to the first system is contained in the semigroup of its transformation from the second system. Translated fromMatematicheskie Zametki, Vol. 66, No. 1, pp. 112–119, July, 1999.  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