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   344篇
  免费   22篇
  国内免费   28篇
化学   48篇
力学   25篇
综合类   4篇
数学   233篇
物理学   84篇
  2023年   4篇
  2022年   4篇
  2021年   7篇
  2020年   4篇
  2019年   6篇
  2018年   8篇
  2017年   5篇
  2016年   9篇
  2015年   8篇
  2014年   11篇
  2013年   29篇
  2012年   10篇
  2011年   18篇
  2010年   9篇
  2009年   25篇
  2008年   24篇
  2007年   18篇
  2006年   17篇
  2005年   26篇
  2004年   17篇
  2003年   21篇
  2002年   13篇
  2001年   9篇
  2000年   5篇
  1999年   11篇
  1998年   11篇
  1997年   10篇
  1996年   9篇
  1995年   7篇
  1994年   1篇
  1993年   3篇
  1992年   4篇
  1991年   1篇
  1990年   1篇
  1989年   2篇
  1988年   3篇
  1986年   3篇
  1985年   2篇
  1984年   3篇
  1982年   1篇
  1981年   2篇
  1979年   3篇
  1978年   4篇
  1977年   2篇
  1976年   4篇
排序方式: 共有394条查询结果,搜索用时 328 毫秒
41.
本文给出了二阶完全对称张量间V(2)中可分元素的坐标间齐次关系,特别地,这种齐次关系可以由行列式表示出来。并由此得到了V(2)中可分元素的一个等价条件。  相似文献   
42.
对出现于公式Πn≥11/(1+dn/n!)=(1-t)e中的整数d给出了精确估计  相似文献   
43.
A model is developed for multivariate distributions which have nearly the same marginals, up to shift and scale. This model, based on “interpolation” of characteristic functions, gives a new notion of “correlation”. It allows straightforward nonparametric estimation of the common marginal distribution, which avoids the “curse of dimensionality” present when nonparametically estimating the full multivariate distribution. The method is illustrated with environmental monitoring network data, where multivariate modelling with common marginals is often appropriate.  相似文献   
44.
Let p, q be arbitrary parameter sets, and let H be a Hilbert space. We say that x = (xi)i?q, xi ? H, is a bounded operator-forming vector (?HFq) if the Gram matrixx, x〉 = [(xi, xj)]i?q,j?q is the matrix of a bounded (necessarily ≥ 0) operator on lq2, the Hilbert space of square-summable complex-valued functions on q. Let A be p × q, i.e., let A be a linear operator from lq2 to lp2. Then exists a linear operator ǎ from (the Banach space) HFq to HFp on D(A) = {x:x ? HFq, A〈x, x〉12 is p × q bounded on lq2} such that y = ǎx satisfies yj?σ(x) = {space spanned by the xi}, 〈y, x〉 = Ax, x〉 and 〈y, y〉 = A〈x, x〉12(A〈x, x〉12)1. This is a generalization of our earlier [J. Multivariate Anal.4 (1974), 166–209; 6 (1976), 538–571] results for the case of a spectral measure concentrated on one point. We apply these tools to investigate q-variate wide-sense Markov processes.  相似文献   
45.
We study the properties of finite ergodic Markov Chains whose transition probability matrix P is singular. The results establish bounds on the convergence time of Pm to a matrix where all the rows are equal to the stationary distribution of P. The results suggest a simple rule for identifying the singular matrices which do not have a finite convergence time. We next study finite convergence to the stationary distribution independent of the initial distribution. The results establish the connection between the convergence time and the order of the minimal polynomial of the transition probability matrix. A queuing problem and a maintenance Markovian decision problem which possess the property of rapid convergence are presented.  相似文献   
46.
An approach to highly enhance the compression efficiency of the integral images by applying the Karhunen-Loeve transform (KLT) algorithm to the motion-compensated sub-images is proposed. The sub-images transformed from the elemental images picked-up from the three-dimensional (3D) object might represent the different perspectives of the object. Thus, the similarity among the sub-images gets better than that among the elemental images, so that an improvement of compression efficiency of the sub-images could be obtained. However, motion vectors occurred among the sub-images might result in an additional increase of image data to be compressed. Accordingly, in this paper, motion vectors have been estimated and compensated in all sub-image in advance. Then the KLT algorithm was applied to these motion-compensated sub-images for compression. It is shown from some experimental results that compression efficiency of the proposed method has been improved up to 24.44%, 40.62%, respectively, on the average compared to that of the conventional KLT compression method and that of the JPEG.  相似文献   
47.
Hongbo Zhang 《代数通讯》2018,46(2):780-791
A ring R is said to have the finitely generated cancellation property provided that the module isomorphism RB?RC implies B?C for any finitely generated R-modules B and C. It is proved that R has this property is equivalent to the existence of the cancellation matrices over R. Moreover, the structure of such matrices is investigated and finite weakly stable rings are characterized in terms of their cancellation matrices.  相似文献   
48.
In this note we introduce some new constructions of dual spaces of operators, which are, of course, at the same time, operator spaces in the sense of Pisier (2003) [12]. We exemplify the utility of these constructs by establishing, in this more general setting, a curious and little known result from the theory of dual algebras, namely from Chevreau and Pearcy (1991) [11].  相似文献   
49.
向量组线性相关性的教学方法与技巧   总被引:1,自引:0,他引:1  
向量组线性相关性是线性代数教学中的一项重要内容.由于概念比较抽象、定理难以理解,因此一直是线性代数教学环节中的一项难点.通过对向量组线性相关性的定义以及判断方法进行了形象的描述,建立向量组线性相关性与矩阵、线性方程组之间的关系,有利于学生理解向量组线性相关性的真正内涵与简便求解方法.  相似文献   
50.
Shushi Harashita 《代数通讯》2013,41(4):1282-1290
In this article, for a noncommutative ring A with some rich structure, we define a ring of Witt vectors with coefficients in A, which is noncommutative unless A is commutative.  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