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   3675篇
  免费   339篇
  国内免费   218篇
化学   659篇
晶体学   15篇
力学   368篇
综合类   166篇
数学   1837篇
物理学   1187篇
  2025年   26篇
  2024年   102篇
  2023年   92篇
  2022年   211篇
  2021年   251篇
  2020年   176篇
  2019年   140篇
  2018年   99篇
  2017年   139篇
  2016年   164篇
  2015年   115篇
  2014年   192篇
  2013年   178篇
  2012年   177篇
  2011年   177篇
  2010年   156篇
  2009年   186篇
  2008年   197篇
  2007年   181篇
  2006年   176篇
  2005年   133篇
  2004年   98篇
  2003年   101篇
  2002年   88篇
  2001年   86篇
  2000年   82篇
  1999年   74篇
  1998年   75篇
  1997年   57篇
  1996年   57篇
  1995年   40篇
  1994年   21篇
  1993年   19篇
  1992年   23篇
  1991年   24篇
  1990年   16篇
  1989年   13篇
  1988年   9篇
  1987年   4篇
  1986年   6篇
  1985年   14篇
  1984年   10篇
  1983年   9篇
  1982年   9篇
  1981年   4篇
  1980年   7篇
  1979年   6篇
  1978年   4篇
  1977年   3篇
  1936年   1篇
排序方式: 共有4232条查询结果,搜索用时 0 毫秒
71.
It is defined the locally order convexity of an ordered uniform space and an ordered topological group and is investigated its relation to the existence of minimum points of denumerable, complete lower bounded sets.  相似文献   
72.
Connections between uniform exponential expansiveness and complete admissibility of the pair are studied. A discrete version for a theorem due to Van Minh, Räbiger and Schnaubelt is presented. Equivalent characterizations of Perron type for uniform exponential expansiveness of evolution families in terms of complete admissibility are given.  相似文献   
73.
We study the isoperimetric problem for product probability measures with respect to the uniform enlargement. We construct several examples of measures for which the isoperimetric function of coincides with the one of the infinite product . This completes earlier works by Bobkov and Houdré.  相似文献   
74.
A mixed boundary value problem for a singularly perturbed reaction-diffusion equation in a square is considered. A Neumann condition is specified on one side of the square, and a Dirichlet condition is set on the other three. It is assumed that the coefficient of the equation, its right-hand side, and the boundary values of the desired solution or its normal derivative on the sides of the square are smooth enough to ensure the required smoothness of the solution in a closed domain outside the neighborhoods of the corner points. No compatibility conditions are assumed to hold at the corner points. Under these assumptions, the desired solution in the entire closed domain is of limited smoothness: it belongs only to the Hölder class C μ, where μ ∈ (0, 1) is arbitrary. In the domain, a nonuniform rectangular mesh is introduced that is refined in the boundary domain and depends on a small parameter. The numerical solution to the problem is based on the classical five-point approximation of the equation and a four-point approximation of the Neumann boundary condition. A mesh refinement rule is described under which the approximate solution converges to the exact one uniformly with respect to the small parameter in the L h norm. The convergence rate is O(N ?2ln2 N), where N is the number of mesh nodes in each coordinate direction. The parameter-uniform convergence of difference schemes for mixed problems without compatibility conditions at corner points was not previously analyzed.  相似文献   
75.
We examine a single machine scheduling problem with random processing times and deadline. Given a set of independent jobs having specified initiation costs and terminal revenues, the objective is to select a subset of the jobs and sequence the selected jobs such that the expected profit is maximized. The job selection aspect considered by us marks a clear departure from the pure sequencing focus found in the traditional scheduling literature. In this paper, we assume an exponentially distributed deadline and do not allow preemption. Even under these conditions, the selection and sequencing problem remains quite difficult (unlike its pure sequencing counterpart); we in fact conjecture that the problem is NP-hard. However, we show that the problem can be efficiently solved as long as the cost parameter is agreeable or an approximate solution is acceptable. To this end, we describe several solution properties, present dynamic programming algorithms (one of which exhibits a pseudo-polynomial time worst-case complexity), and propose a fully-polynomial time approximation scheme. In addition, we study a number of special cases which can be solved in polynomial time. Finally, we summarize our work and discuss an extension where the jobs are precedence related.  相似文献   
76.
对于复域中满足某种条件的Jordan区域D和函数f∈B(D),证明了基于Fejer点的高阶Fejer插值多项式一致收敛于对应的函数f(z)于D上.本文中的这些定理推广了某些已知的结果.  相似文献   
77.
葛仁福 《大学数学》2011,27(4):179-181
利用函数列和函数一致连续的有关性质,得到了函数列一致收敛新的判别法.  相似文献   
78.
79.
针对初始排污权总量分配的实际问题,基于统一价格拍卖的思想提出了一种具有激励性的可变总量的分配方法,分别给出了排污企业对称和排污企业非对称两种情形下的线性均衡报价策略,并证明了该方法的可行性和有效性,从而为建设排污权分配和交易制度提供了理论依据和方法参考.  相似文献   
80.
In this paper, we give several results of learning errors for linear programming support vector regression. The corresponding theorems are proved in the reproducing kernel Hilbert space. With the covering number, the approximation property and the capacity of the reproducing kernel Hilbert space are measured. The obtained result (Theorem 2.1) shows that the learning error can be controlled by the sample error and regularization error. The mentioned sample error is summarized by the errors of learning regression function and regularizing function in the reproducing kernel Hilbert space. After estimating the generalization error of learning regression function (Theorem 2.2), the upper bound (Theorem 2.3) of the regularized learning algorithm associated with linear programming support vector regression is estimated.  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