全文获取类型
收费全文 | 13848篇 |
免费 | 2014篇 |
国内免费 | 577篇 |
专业分类
化学 | 1989篇 |
晶体学 | 79篇 |
力学 | 1762篇 |
综合类 | 236篇 |
数学 | 7023篇 |
物理学 | 5350篇 |
出版年
2024年 | 46篇 |
2023年 | 141篇 |
2022年 | 454篇 |
2021年 | 469篇 |
2020年 | 327篇 |
2019年 | 348篇 |
2018年 | 366篇 |
2017年 | 504篇 |
2016年 | 512篇 |
2015年 | 423篇 |
2014年 | 818篇 |
2013年 | 834篇 |
2012年 | 895篇 |
2011年 | 775篇 |
2010年 | 687篇 |
2009年 | 801篇 |
2008年 | 813篇 |
2007年 | 858篇 |
2006年 | 752篇 |
2005年 | 661篇 |
2004年 | 519篇 |
2003年 | 486篇 |
2002年 | 442篇 |
2001年 | 434篇 |
2000年 | 395篇 |
1999年 | 309篇 |
1998年 | 316篇 |
1997年 | 285篇 |
1996年 | 223篇 |
1995年 | 231篇 |
1994年 | 188篇 |
1993年 | 143篇 |
1992年 | 139篇 |
1991年 | 131篇 |
1990年 | 98篇 |
1989年 | 79篇 |
1988年 | 67篇 |
1987年 | 60篇 |
1986年 | 50篇 |
1985年 | 62篇 |
1984年 | 61篇 |
1983年 | 19篇 |
1982年 | 29篇 |
1981年 | 31篇 |
1980年 | 25篇 |
1979年 | 34篇 |
1978年 | 22篇 |
1977年 | 32篇 |
1976年 | 18篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
C. Bogani M. G. Gasparo A. Papini 《Journal of Optimization Theory and Applications》2007,134(1):47-59
We propose a pattern search method to solve a classical nonsmooth optimization problem. In a deep analogy with pattern search
methods for linear constrained optimization, the set of search directions at each iteration is defined in such a way that
it conforms to the local geometry of the set of points of nondifferentiability near the current iterate. This is crucial to
ensure convergence. The approach presented here can be extended to wider classes of nonsmooth optimization problems. Numerical
experiments seem to be encouraging.
This work was supported by M.U.R.S.T., Rome, Italy. 相似文献
42.
Protein Conformation of a Lattice Model Using Tabu Search 总被引:1,自引:0,他引:1
We apply tabu search techniques to the problem of determining the optimal configuration of a chain of protein sequences on a cubic lattice. The problem under study is difficult to solve because of the large number of possible conformations and enormous amount of computations required. Tabu search is an iterative heuristic procedure which has been shown to be a remarkably effective method for solving combinatorial optimization problems. In this paper, an algorithm is designed for the cubic lattice model using tabu search. The algorithm has been tested on a chain of 27 monomers. Computational results show that our method outperforms previously reported approaches for the same model. 相似文献
43.
44.
Charles Blair 《Mathematical Programming》1995,71(2):127-136
We identify a class of formulas computable in polynomial time such that the functions defined by these formulas are precisely the value functions of mixed-integer programs with rational constraint coefficients. 相似文献
45.
Q.J. Zhu 《Journal of Mathematical Analysis and Applications》2007,326(1):708-720
Investment systems are studied using a framework that emphasize their profiles (the cumulative probability distribution on all the possible percentage gains of trades) and their log return functions (the expected average return per trade in logarithmic scale as a function of the investment size in terms of the percentage of the available capital). The efficiency index for an investment system, defined as the maximum of the log return function, is proposed as a measure to compare investment systems for their intrinsic merit. This efficiency index can be viewed as a generalization of Shannon's information rate for a communication channel. Applications are illustrated. 相似文献
46.
首先将无线传感器网络的路由问题转化成求解最小Steiner树问题,然后给出了求解无线传感器网络路由的蚁群优化算法,并对算法的收敛性进行了证明.最后对找到最优解后信息素值的变化进行了分析.即在限制信息素取值的条件下,当迭代次数充分大时,该算法能以任意接近于1的概率找到最优解,并且当最优解找到后,最优树边上的信息素单调增加,而最优解以外边上的信息素在有限步达到最小值. 相似文献
47.
E. Hernández L. Rodríguez-Marín 《Journal of Optimization Theory and Applications》2007,134(1):119-134
In this paper, we study optimization problems where the objective function and the binding constraints are set-valued maps
and the solutions are defined by means of set-relations among all the images sets (Kuroiwa, D. in Takahashi, W., Tanaka, T.
(eds.) Nonlinear analysis and convex analysis, pp. 221–228, 1999). We introduce a new dual problem, establish some duality theorems and obtain a Lagrangian multiplier rule of nonlinear type
under convexity assumptions. A necessary condition and a sufficient condition for the existence of saddle points are given.
The authors thank the two referees for valuable comments and suggestions on early versions of the paper. The research of the
first author was partially supported by Ministerio de Educación y Ciencia (Spain) Project MTM2006-02629 and by Junta de Castilla
y León (Spain) Project VA027B06. 相似文献
48.
Madhu V. Nayakkankuppam 《Mathematical Programming》2007,109(2-3):477-504
We describe an approach to the parallel and distributed solution of large-scale, block structured semidefinite programs using
the spectral bundle method. Various elements of this approach (such as data distribution, an implicitly restarted Lanczos
method tailored to handle block diagonal structure, a mixed polyhedral-semidefinite subdifferential model, and other aspects
related to parallelism) are combined in an implementation called LAMBDA, which delivers faster solution times than previously
possible, and acceptable parallel scalability on sufficiently large problems.
This work was supported in part by NSF grants DMS-0215373 and DMS-0238008. 相似文献
49.
Peter Francis Guangming Zhang Karen Smilowitz 《European Journal of Operational Research》2007,180(3):1045-1059
This paper presents modeling and solution method improvements for the Multi-Resource Routing Problem (MRRP) with flexible tasks. The MRRP with flexible tasks is used to model routing and scheduling problems for intermodal drayage operations in which two resources (tractors and trailers) perform tasks to transport loaded and empty equipment. Tasks may be either well defined, in which both the origin and the destination of a movement are given, or flexible, in which the origin or the destination is chosen by the model. This paper proposes methods to effectively manage the number of options considered for flexible tasks (either feasible origins for a known destination or feasible destinations for a known origin). This modeling change generates sufficient options to allow for low-cost solutions while maintaining reasonable computational effort. We also propose a new solution method that uses randomized route generation. Computational results from test cases show that these changes improve the quality of solutions by at least 5% in the test cases as compared to methods from previous studies. 相似文献
50.
B. Ivorra A. M. Ramos B. Mohammadi 《Journal of Optimization Theory and Applications》2007,135(3):549-561
This paper has two objectives. We introduce a new global optimization algorithm reformulating optimization problems in terms
of boundary-value problems. Then, we apply this algorithm to a pointwise control problem of the viscous Burgers equation,
where the control weight coefficient is progressively decreased. The results are compared with those obtained with a genetic
algorithm and an LM-BFGS algorithm in order to check the efficiency of our method and the necessity of using global optimization
techniques. 相似文献