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   2386篇
  免费   164篇
  国内免费   148篇
化学   45篇
晶体学   4篇
力学   131篇
综合类   34篇
数学   2273篇
物理学   211篇
  2024年   2篇
  2023年   18篇
  2022年   29篇
  2021年   47篇
  2020年   44篇
  2019年   58篇
  2018年   51篇
  2017年   54篇
  2016年   64篇
  2015年   47篇
  2014年   91篇
  2013年   200篇
  2012年   106篇
  2011年   84篇
  2010年   80篇
  2009年   121篇
  2008年   106篇
  2007年   136篇
  2006年   110篇
  2005年   110篇
  2004年   103篇
  2003年   101篇
  2002年   121篇
  2001年   71篇
  2000年   92篇
  1999年   81篇
  1998年   70篇
  1997年   61篇
  1996年   45篇
  1995年   42篇
  1994年   42篇
  1993年   40篇
  1992年   36篇
  1991年   31篇
  1990年   29篇
  1989年   22篇
  1988年   15篇
  1987年   10篇
  1986年   21篇
  1985年   15篇
  1984年   22篇
  1983年   11篇
  1982年   11篇
  1981年   13篇
  1980年   5篇
  1979年   8篇
  1978年   6篇
  1977年   7篇
  1976年   4篇
  1973年   2篇
排序方式: 共有2698条查询结果,搜索用时 15 毫秒
991.
设D=n∏i=1p_i(n∈Z~+),p_i≡5(mod6)(i=1,2,…,n)为彼此不相同的奇素数,q≡1(mod6)为奇素数,运用Pell方程的解的性质、同余式、平方剩余、递归序列等给出了丢番图方程x~3±1=6qDy~2仅有平凡解的三个充分条件.  相似文献   
992.
We furnish an upper bound for the moment of negative eigenvalues for a relativistic Schrödinger operator defined in a proper subspace of square-integrable functions.  相似文献   
993.
994.
Presenting the structure equation of a hom-Lie algebra 𝔤, as the vanishing of the self commutator of a coderivation of some associative comultiplication, we define up to homotopy hom-Lie algebras, which yields the general hom-Lie algebra cohomology with value in a module. If the hom-Lie algebra is quadratic, using the Pinczon bracket on skew symmetric multilinear forms on 𝔤, we express this theory in the space of forms. If the hom-Lie algebra is symmetric, it is possible to associate to each module a quadratic hom-Lie algebra and describe the cohomology with value in the module.  相似文献   
995.
Let be a metric measure space of homogeneous type and L be a one‐to‐one operator of type ω on for ω ∈[0, π /2). In this article, under the assumptions that L has a bounded H ‐functional calculus on and satisfies (p L , q L ) off‐diagonal estimates on balls, where p L ∈[1, 2) and q L ∈(2, ], the authors establish a characterization of the Sobolev space , defined via L α /2, of order α ∈(0, 2] for p ∈(p L , q L ) by means of a quadratic function S α , L . As an application, the authors show that for the degenerate elliptic operator L w : =? w  ? 1div(A ?) and the Schrödinger type operator with a ∈(0, ) on the weighted Euclidean space with A being real symmetric, if n ?3, with q ∈[1, 2], , p ∈(1, ) and with , then, for all , , where the implicit equivalent positive constants are independent of f , denotes the class of Muckenhoupt weights, the reverse Hölder class, and D (L w ) and the domains of L w and , respectively. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
996.
997.
We use computational linear algebra and commutative algebra to study spaces of relations satisfied by quadrilinear operations. The relations are analogues of associativity in the sense that they are quadratic (every term involves two operations) and nonsymmetric (every term involves the identity permutation of the arguments). We focus on determining those quadratic relations whose cubic consequences have minimal or maximal rank. We approach these problems from the point of view of the theory of algebraic operads.  相似文献   
998.
圆锥规划是一类重要的非对称锥优化问题.基于一个光滑函数,将圆锥规划的最优性条件转化成一个非线性方程组,然后给出求解圆锥规划的光滑牛顿法.该算法只需求解一个线性方程组和进行一次线搜索.运用欧几里得约当代数理论,证明该算法具有全局和局部二阶收敛性.最后数值结果表明算法的有效性.  相似文献   
999.
Let X(t), , be a centered real-valued stationary Gaussian process with spectral density f(λ). The paper considers a question concerning asymptotic distribution of Toeplitz type quadratic functional Q T of the process X(t), generated by an integrable even function g(λ). Sufficient conditions in terms of f(λ) and g(λ) ensuring central limit theorems for standard normalized quadratic functionals Q T are obtained, extending the results of Fox and Taqqu (Prob. Theory Relat. Fields 74: 213–240, 1987), Avram (Prob. Theory Relat. Fields 79:37–45, 1988), Giraitis and Surgailis (Prob. Theory Relat. Fields 86: 87–104, 1990), Ginovian and Sahakian (Theory Prob. Appl. 49:612–628, 2004) for discrete time processes.   相似文献   
1000.
For current sequential quadratic programming (SQP) type algorithms, there exist two problems: (i) in order to obtain a search direction, one must solve one or more quadratic programming subproblems per iteration, and the computation amount of this algorithm is very large. So they are not suitable for the large-scale problems; (ii) the SQP algorithms require that the related quadratic programming subproblems be solvable per iteration, but it is difficult to be satisfied. By using ε-active set procedure with a special penalty function as the merit function, a new algorithm of sequential systems of linear equations for general nonlinear optimization problems with arbitrary initial point is presented. This new algorithm only needs to solve three systems of linear equations having the same coefficient matrix per iteration, and has global convergence and local superlinear convergence. To some extent, the new algorithm can overcome the shortcomings of the SQP algorithms mentioned above. Project partly supported by the National Natural Science Foundation of China and Tianyuan Foundation of China.  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