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   110005篇
  免费   6128篇
  国内免费   4183篇
化学   47168篇
晶体学   1112篇
力学   8447篇
综合类   217篇
数学   35500篇
物理学   27872篇
  2024年   98篇
  2023年   693篇
  2022年   1242篇
  2021年   1354篇
  2020年   1339篇
  2019年   1425篇
  2018年   11381篇
  2017年   11086篇
  2016年   7596篇
  2015年   2471篇
  2014年   2273篇
  2013年   2834篇
  2012年   6747篇
  2011年   13357篇
  2010年   7647篇
  2009年   7963篇
  2008年   8638篇
  2007年   10495篇
  2006年   1980篇
  2005年   2714篇
  2004年   2640篇
  2003年   2801篇
  2002年   1923篇
  2001年   955篇
  2000年   873篇
  1999年   857篇
  1998年   717篇
  1997年   656篇
  1996年   683篇
  1995年   532篇
  1994年   431篇
  1993年   464篇
  1992年   298篇
  1991年   318篇
  1990年   260篇
  1989年   237篇
  1988年   214篇
  1987年   169篇
  1986年   160篇
  1985年   147篇
  1984年   127篇
  1983年   84篇
  1982年   97篇
  1981年   72篇
  1980年   75篇
  1979年   61篇
  1978年   53篇
  1973年   43篇
  1914年   45篇
  1909年   41篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
This paper deals with the solvability of boundary value problems for singular integral equations of the form (i)-(ii).By an algebraic method we reduce the problem (i)-(ii) to a system of linear algebraic equations which gives all solutions in a closed form.AMS Subject Classification: 47G05, 45GO5, 45E05  相似文献   
992.
In this paper, we first derive the representation theorem of onto isometric mappings in the unit spheres of l p (Г) (@#@(p >) 1,p ≠ 2 type spaces, and then we conclude that such mappings can be extended to the whole space as real linear isometries by using the previous result of the author.  相似文献   
993.
Empirical likelihood for partial linear models   总被引:2,自引:0,他引:2  
In this paper the empirical likelihood method due to Owen (1988,Biometrika,75, 237–249) is applied to partial linear random models. A nonparametric version of Wilks' theorem is derived. The theorem is then used to construct confidence regions of the parameter vector in the partial linear models, which has correct asymptotic coverage. A simulation study is conducted to compare the empirical likelihood and normal approximation based method. Research supported by NNSF of China and a grant to the first author for his excellent Ph.D. dissertation work in China. Research supported by Hong Kong RGC CERG No. HKUST6162/97P.  相似文献   
994.
 This article describes the almost sure infinite volume asymptotics of the ground state energy of random Schr?dinger operators with scaled Gibbsian potentials. The random potential is obtained by distributing soft obstacles according to an infinite volume grand canonical tempered Gibbs measure with a superstable pair interaction. There is no restriction on the strength of the pair interaction: it may be taken, e.g., at a critical point. The potential is scaled with the box size in a critical way, i.e. the scale is determined by the typical size of large deviations in the Gibbsian cloud. The almost sure infinite volume asymptotics of the ground state energy is described in terms of two equivalent deterministic variational principles involving only thermodynamic quantities. The qualitative behaviour of the ground state energy asymptotics is analysed: Depending on the dimension and on the H?lder exponents of the free energy density, it is identified which cases lead to a phase transition of the asymptotic behaviour of the ground state energy. Received: 24 June 2002 / Revised version: 17 February 2003 Published online: 12 May 2003 Mathematics Subject Classification (2000): Primary 82B44; Secondary 60K35 Key words or phrases: Gibbs measure – H?lder exponents – Random Schr?dinger operator – Ground state – Large deviations  相似文献   
995.
In [4], assuming among others subadditivity and submultiplicavity of a function ψ: [0, ∞)→[0, ∞), the authors proved a Hyers-Ulam type stability theorem for “ψ-additive” mappings of a normed space into a normed space. In this note we show that the assumed conditions of the function ψ imply that ψ=0 and, consequently, every “ψ-additive” mapping must be additive  相似文献   
996.
We establish a mean square estimate on the weight aspect for symmetric square L-functions at every point on the critical line. Received: 15 February 2002  相似文献   
997.
In this paper, we present an explicit calculation of the heat kernel, fundamental solution and Schwartz kernel of the resolvent for the Heisenberg Laplacian using Wiener path integrals and their realizations via the Trotter product formula. This also gives another derivation of mehler’s formula.  相似文献   
998.
In this paper we shall give a topological representation for Hilbert algebras that extend the topological representation given by A. Diego in [4]. For implicative semilattices this representation gives a full duality. We shall also consider the representation for Boolean ring.  相似文献   
999.
This paper deals with the cost benefit analysis of series systems with warm standby components. The time-to-repair and the time-to-failure for each of the primary and warm standby components is assumed to have the negative exponential distribution. We develop the explicit expressions for the mean time-to-failure, MTTF, and the steady-state availability, A T () for three configurations and perform a comparative analysis. Under the cost/benefit (C/B) criterion, comparisons are made based on assumed numerical values given to the distribution parameters, and to the cost of the components. The configurations are ranked based on: MTTF, A T (), and C/B where B is either MTTF or A T ().  相似文献   
1000.
 In this paper, the negative gradient flow for the L 2-integral of Ricci curvature on a 3-manifold is considered. It is not known whether the solution to this fourth order geometric evolution equation exists, and whether it will develop singularities in finite time. Based on the trick of De Turck and the idea of Hamilton on the flow of Ricci curvature, the local existence on any compact Riemannian manifold is obtained. In addition, the conditions for the occurences of singularities in finite time during the evolution and the asymptotic behavior of the flow on a 3-manifold are discussed. Received: 22 April 2002 / Revised version: 5 January 2003 Published online: 24 April 2003 This work is partially supported by the Foundations of NNSF of China, the Foundation for University Key Teacher by MEC and Shanghai Priority Academic Discipline.  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