全文获取类型
收费全文 | 11796篇 |
免费 | 1572篇 |
国内免费 | 873篇 |
专业分类
化学 | 3730篇 |
晶体学 | 58篇 |
力学 | 971篇 |
综合类 | 83篇 |
数学 | 3889篇 |
物理学 | 5510篇 |
出版年
2024年 | 14篇 |
2023年 | 109篇 |
2022年 | 232篇 |
2021年 | 303篇 |
2020年 | 365篇 |
2019年 | 345篇 |
2018年 | 337篇 |
2017年 | 360篇 |
2016年 | 452篇 |
2015年 | 352篇 |
2014年 | 578篇 |
2013年 | 1139篇 |
2012年 | 669篇 |
2011年 | 758篇 |
2010年 | 595篇 |
2009年 | 685篇 |
2008年 | 690篇 |
2007年 | 759篇 |
2006年 | 655篇 |
2005年 | 556篇 |
2004年 | 451篇 |
2003年 | 432篇 |
2002年 | 432篇 |
2001年 | 364篇 |
2000年 | 371篇 |
1999年 | 260篇 |
1998年 | 255篇 |
1997年 | 208篇 |
1996年 | 161篇 |
1995年 | 169篇 |
1994年 | 140篇 |
1993年 | 144篇 |
1992年 | 118篇 |
1991年 | 100篇 |
1990年 | 83篇 |
1989年 | 63篇 |
1988年 | 62篇 |
1987年 | 47篇 |
1986年 | 49篇 |
1985年 | 75篇 |
1984年 | 66篇 |
1983年 | 28篇 |
1982年 | 42篇 |
1981年 | 27篇 |
1980年 | 23篇 |
1979年 | 22篇 |
1978年 | 19篇 |
1977年 | 23篇 |
1976年 | 16篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
41.
随机交通均衡配流模型及其等价的变分不等式问题 总被引:7,自引:0,他引:7
本文讨论了交通网络系统的随机用户均衡原理的数学表述问题.在路段出行成本是流量的单调函数的较弱条件下,对具有固定需求和弹性需求的模式,首次证明了随机均衡配流模型可表示为一个变分不等式问题,同时也说明了该变分不等式问题与相应的互补问题以及一个凸规划问题之间的等价关系. 相似文献
42.
M/G/1非空竭服务休假排队系统随机分解的简化算法 总被引:2,自引:0,他引:2
本文根据M/G/1非空竭服务休假排队系统稳态队长随机分解的结构特征提出一种统一算法,该方法简洁高效,避免了再生循环方法繁杂的运算。运用该方法得出的结果与已知的用再生循环方法得出的结论一致。并且修正了Levy(1989)关于Bernoulli闸门服务休假排队系统随机分解的一个错误。 相似文献
43.
44.
We introduce here some Itô calculus for non-continuous Dirichlet processes. Such calculus extends what was known for continuous Dirichlet processes or for semimartingales. In particular we prove that non-continuous Dirichlet processes are stable under C
1 transformation. 相似文献
45.
46.
The Sample Average Approximation Method Applied to Stochastic Routing Problems: A Computational Study 总被引:1,自引:0,他引:1
Bram Verweij Shabbir Ahmed Anton J. Kleywegt George Nemhauser Alexander Shapiro 《Computational Optimization and Applications》2003,24(2-3):289-333
The sample average approximation (SAA) method is an approach for solving stochastic optimization problems by using Monte Carlo simulation. In this technique the expected objective function of the stochastic problem is approximated by a sample average estimate derived from a random sample. The resulting sample average approximating problem is then solved by deterministic optimization techniques. The process is repeated with different samples to obtain candidate solutions along with statistical estimates of their optimality gaps.We present a detailed computational study of the application of the SAA method to solve three classes of stochastic routing problems. These stochastic problems involve an extremely large number of scenarios and first-stage integer variables. For each of the three problem classes, we use decomposition and branch-and-cut to solve the approximating problem within the SAA scheme. Our computational results indicate that the proposed method is successful in solving problems with up to 21694 scenarios to within an estimated 1.0% of optimality. Furthermore, a surprising observation is that the number of optimality cuts required to solve the approximating problem to optimality does not significantly increase with the size of the sample. Therefore, the observed computation times needed to find optimal solutions to the approximating problems grow only linearly with the sample size. As a result, we are able to find provably near-optimal solutions to these difficult stochastic programs using only a moderate amount of computation time. 相似文献
47.
48.
K. Kubilius 《Acta Appl Math》2003,78(1-3):233-242
We consider the integral equation driven by a standard Brownian motion and by a fractional Brownian motion. Sufficient conditions under which the equation has a weak solution are obtained. 相似文献
49.
50.
A. Debussche 《Journal de Mathématiques Pures et Appliquées》1998,77(10):967-988
The notion of random attractor for a dissipative stochastic dynamical system has recently been introduced. It generalizes the concept of global attractor in the deterministic theory. It has been shown that many stochastic dynamical systems associated to a dissipative partial differential equation perturbed by noise do possess a random attractor. In this paper, we prove that, as in the case of the deterministic attractor, the Hausdorff dimension of the random attractor can be estimated by using global Lyapunov exponents. The result is obtained under very natural assumptions. As an application, we consider a stochastic reaction-diffusion equation and show that its random attractor has finite Hausdorff dimension. 相似文献