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   6576篇
  免费   153篇
  国内免费   5篇
化学   3685篇
晶体学   31篇
力学   154篇
数学   1501篇
物理学   1363篇
  2021年   55篇
  2020年   70篇
  2019年   72篇
  2018年   151篇
  2017年   147篇
  2016年   222篇
  2015年   160篇
  2014年   217篇
  2013年   538篇
  2012年   333篇
  2011年   459篇
  2010年   249篇
  2009年   221篇
  2008年   381篇
  2007年   370篇
  2006年   345篇
  2005年   255篇
  2004年   221篇
  2003年   162篇
  2002年   158篇
  2001年   99篇
  2000年   89篇
  1999年   59篇
  1998年   53篇
  1997年   54篇
  1996年   52篇
  1995年   46篇
  1994年   33篇
  1993年   45篇
  1992年   59篇
  1991年   46篇
  1990年   57篇
  1989年   58篇
  1988年   52篇
  1987年   46篇
  1986年   44篇
  1985年   62篇
  1984年   70篇
  1983年   66篇
  1982年   61篇
  1981年   42篇
  1980年   54篇
  1979年   47篇
  1978年   73篇
  1977年   45篇
  1976年   62篇
  1975年   42篇
  1974年   50篇
  1973年   42篇
  1972年   33篇
排序方式: 共有6734条查询结果,搜索用时 442 毫秒
991.
992.
In this paper we give the complete answer to a question posed by A. Arhangel?skii and prove that the sphere SnSn is diagonal resolvable if and only if SnSn is an H  -space if and only if n∈{0,1,3,7}n{0,1,3,7}. Moreover, we prove that any upper half even dimensional QQ-sphere cannot be diagonal resolvable.  相似文献   
993.
994.
We transform a continuous Weber problem with barriers to a discrete problem by computing some efficient locations, which are considered as promising locations for a new facility. A theorem determining conditions for a location to be efficient is introduced. A method for constructing the weighted coefficients and travel costs modeled by some distance metrics, is derived. This method provides successive computation of some efficient locations. Also, we propose an algorithm for the verification of location’s efficiency. Numerical examples are provided using squared Euclidean and Manhattan distance metrics, as well as the implementation details in programming package MATHEMATICA.  相似文献   
995.
Multi body system contains finite number of rigid bodies that are placed on each axis, which do not intersect each other. Derivatives of the linear momentum and angular momentum with respect to time by use mass moment vectors and vector rotators for pole and axis, are determined. A number of theorems are defined. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
996.
We consider a mixture of N ideal, polytropic gases. Each species is described by a distribution function fi(t, x, v, I) ≥ 0, 1 ≤ i ≤ N, defined on , and its evolution is governed by a Boltzmann-type equation. In order to recover the energy law of polytropic gases, the authors of [4] proposed a kinetic model in the framework of a weighted L1 space. Another approach has been developed in [3] in the context of polyatomic gases. Following this previous lead, our model provides a L2 framework in both variables v and I, to eventually perform a mathematical study of the diffusion asymptotics, as it was done in [2] for a model without energy exchange. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
997.
Aleksandra Delić 《PAMM》2013,13(1):349-350
We investigate the convergence of difference scheme for the time-fractional differential equation with fractional derivative of an order with the coefficient at the time derivative containing Dirac delta distribution. Convergence order of is proved. A numerical example demonstrates the theoretical results. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
998.
In the setting of generalized metric spaces, so called G-metric spaced introduced by Z. Mustafa and B. Sims in 2006, some fixed point results for mappings with contractive iterate at a point and common fixed point results for infinite family of self mappings will be presented. The results are generalizations of well known results in the metric space. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
999.
In this paper, a modified approach to the multiparameter non-central Stirling numbers via differential operators, introduced by El-Desouky, and new explicit formulae of both kinds of these numbers are given. Also, some relations between these numbers and the generalized Hermite and Truesdel polynomials are obtained. Moreover, we investigate some new results for the generalized Stirling-type pair of Hsu and Shiue. Furthermore some interesting special cases, new combinatorial identities and a matrix representation are deduced.  相似文献   
1000.
Derivative free methods for solving nonlinear equations of Steffensen’s type are presented. Using two self-correcting parameters, calculated by Newton’s interpolatory polynomials of second and third degree, the order of convergence is increased from 2 to 3.56. This method is used as a corrector for a family of biparametric two-step derivative free methods with and without memory with the accelerated convergence rate up to order 7. Significant acceleration of convergence is attained without any additional function calculations, which provides very high computational efficiency of the proposed methods. Another advantage is a convenient fact that the proposed methods do not use derivatives. Numerical examples are given to demonstrate excellent convergence behavior of the proposed methods and good coincidence with theoretical results.  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