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   3132篇
  免费   171篇
  国内免费   323篇
化学   66篇
力学   86篇
综合类   61篇
数学   2958篇
物理学   455篇
  2024年   5篇
  2023年   23篇
  2022年   35篇
  2021年   50篇
  2020年   64篇
  2019年   69篇
  2018年   74篇
  2017年   70篇
  2016年   82篇
  2015年   49篇
  2014年   152篇
  2013年   216篇
  2012年   127篇
  2011年   132篇
  2010年   149篇
  2009年   199篇
  2008年   225篇
  2007年   241篇
  2006年   206篇
  2005年   163篇
  2004年   127篇
  2003年   165篇
  2002年   143篇
  2001年   134篇
  2000年   116篇
  1999年   100篇
  1998年   100篇
  1997年   76篇
  1996年   64篇
  1995年   30篇
  1994年   31篇
  1993年   19篇
  1992年   19篇
  1991年   15篇
  1990年   12篇
  1989年   10篇
  1988年   16篇
  1987年   7篇
  1986年   6篇
  1985年   19篇
  1984年   10篇
  1983年   12篇
  1982年   14篇
  1981年   7篇
  1980年   6篇
  1979年   7篇
  1978年   6篇
  1976年   8篇
  1975年   6篇
  1974年   4篇
排序方式: 共有3626条查询结果,搜索用时 14 毫秒
1.
We prove the iteration lemmata, which are the key lemmata to show that extensions by Pmax variations satisfy absoluteness for Π2-statements in the structure 〈H (ω 2), ∈, NSω 1, R 〉 for some set R of reals in L (ℝ), for the following statements: (1) The cofinality of the null ideal is ℵ1. (2) There exists a good basis of the strong measure zero ideal. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
2.
本文目的在于建立确定R ̄d中Hausdorff维数dim和packing维数Dim的两个命题(定理1和定理2),进而寻求R ̄d中Hausdorff维数dim与packing维数Dim相等的条件;这使得我们能够引入分形测度的测度论定义。  相似文献   
3.
Domain adaptation aims to learn a classifier for a target domain task by using related labeled data from the source domain. Because source domain data and target domain task may be mismatched, there is an uncertainty of source domain data with respect to the target domain task. Ignoring the uncertainty may lead to models with unreliable and suboptimal classification results for the target domain task. However, most previous works focus on reducing the gap in data distribution between the source and target domains. They do not consider the uncertainty of source domain data about the target domain task and cannot apply the uncertainty to learn an adaptive classifier. Aimed at this problem, we revisit the domain adaptation from source domain data uncertainty based on evidence theory and thereby devise an adaptive classifier with the uncertainty measure. Based on evidence theory, we first design an evidence net to estimate the uncertainty of source domain data about the target domain task. Second, we design a general loss function with the uncertainty measure for the adaptive classifier and extend the loss function to support vector machine. Finally, numerical experiments on simulation datasets and real-world applications are given to comprehensively demonstrate the effectiveness of the adaptive classifier with the uncertainty measure.  相似文献   
4.
Properties of the Voronoi tessellations arising from random 2D distribution points are reported. We applied an iterative procedure to the Voronoi diagrams generated by a set of points randomly placed on the plane. The procedure implied dividing the edges of Voronoi cells into equal or random parts. The dividing points were then used to construct the following Voronoi diagram. Repeating this procedure led to a surprising effect of the positional ordering of Voronoi cells, reminiscent of the formation of lamellae and spherulites in linear semi-crystalline polymers and metallic glasses. Thus, we can conclude that by applying even a simple set of rules to a random set of seeds, we can introduce order into an initially disordered system. At the same time, the Shannon (Voronoi) entropy showed a tendency to attain values that are typical for completely random patterns; thus, the Shannon (Voronoi) entropy does not distinguish the short-range ordering. The Shannon entropy and the continuous measure of symmetry of the patterns demonstrated the distinct asymptotic behavior, while approaching the close saturation values with the increase in the number of iteration steps. The Shannon entropy grew with the number of iterations, whereas the continuous measure of symmetry of the same patterns demonstrated the opposite asymptotic behavior. The Shannon (Voronoi) entropy is not an unambiguous measure of order in the 2D patterns. The more symmetrical patterns may demonstrate the higher values of the Shannon entropy.  相似文献   
5.
In this note, we characterize the regular probability measures satisfying the Choquet-Deny convolution equation =* on Abelian topological semigroups for a given probability measure .  相似文献   
6.
In this paper, we introduce and study the signed fuzzy-valued measure and using the representation theorem of fuzzy numbers, we establish the Radon-Nikodym theorem for fuzzy-valued measurable functions with respect to fuzzy-valued measures.AMS Subject Classification (2000): 28E10, 04A72The research of this work is supposed by a grant of the education committee of Liaoning Province, China #20161049  相似文献   
7.
The goal of this paper is to provide a tool, the Global Measure Formula, that will facilitate the study of the limit set of discrete geometrically finite groups of isometries of the rank one symmetric spaces. We consider the shadow of a ball from a fixed reference point onto the boundary, and prove a formula that describes the measure of the shadow in terms of the center of the shadowed ball, generalizing a result from real hyperbolic geometry.  相似文献   
8.
An inner function I in the unit ball BnBnn is said to be weakly outer if the closed subspace I H p(B n) is weakly dense in the Hardy space Hp(B n), 0n for all n1. We also investigate inner functions I such that the subspace IHp(B n) is not weakly dense in Hp(B n).  相似文献   
9.
Let T be a homogeneous tree of homogeneity q+1. Let denote the boundary of T, consisting of all infinite geodesics b=[b 0,b 1,b 2,] beginning at the root, 0. For each b, 1, and a0 we define the approach region ,a (b) to be the set of all vertices t such that, for some j, t is a descendant of b j and the geodesic distance of t to b j is at most (–1)j+a. If >1, we view these as tangential approach regions to b with degree of tangency . We consider potentials Gf on T for which the Riesz mass f satisfies the growth condition T f p (t)q –|t|<, where p>1 and 0<<1, or p=1 and 0<1. For 11/, we show that Gf(s) has limit zero as s approaches a boundary point b within ,a (b) except for a subset E of of -dimensional Hausdorff measure 0, where H (E)=sup>0inf i q –|t i|:E a subset of the boundary points passing through t i for some i,|t i |>log q (1/).  相似文献   
10.
We discuss a possibility of deciding whether measures representing a moment sequence or realizing orthogonality of polynomials have atoms. This is done on the real line and in several variables.  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