全文获取类型
收费全文 | 15086篇 |
免费 | 1122篇 |
国内免费 | 772篇 |
专业分类
化学 | 1520篇 |
晶体学 | 22篇 |
力学 | 880篇 |
综合类 | 218篇 |
数学 | 12318篇 |
物理学 | 2022篇 |
出版年
2024年 | 18篇 |
2023年 | 82篇 |
2022年 | 136篇 |
2021年 | 214篇 |
2020年 | 225篇 |
2019年 | 261篇 |
2018年 | 264篇 |
2017年 | 361篇 |
2016年 | 388篇 |
2015年 | 284篇 |
2014年 | 646篇 |
2013年 | 955篇 |
2012年 | 810篇 |
2011年 | 692篇 |
2010年 | 674篇 |
2009年 | 883篇 |
2008年 | 958篇 |
2007年 | 1012篇 |
2006年 | 797篇 |
2005年 | 733篇 |
2004年 | 599篇 |
2003年 | 544篇 |
2002年 | 577篇 |
2001年 | 517篇 |
2000年 | 492篇 |
1999年 | 455篇 |
1998年 | 369篇 |
1997年 | 333篇 |
1996年 | 329篇 |
1995年 | 298篇 |
1994年 | 220篇 |
1993年 | 206篇 |
1992年 | 203篇 |
1991年 | 180篇 |
1990年 | 139篇 |
1989年 | 106篇 |
1988年 | 113篇 |
1987年 | 91篇 |
1986年 | 106篇 |
1985年 | 136篇 |
1984年 | 109篇 |
1983年 | 34篇 |
1982年 | 69篇 |
1981年 | 54篇 |
1980年 | 50篇 |
1979年 | 47篇 |
1978年 | 58篇 |
1977年 | 60篇 |
1976年 | 34篇 |
1974年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The objective of this paper is to analyze under what well-known operations the class of quasipolyhedral convex functions,
which can be regarded as an extension of that of polyhedral convex functions, is closed. The operations that will be considered
are those that preserve polyhedral convexity, such that the image and the inverse image under linear transformations, right
scalar multiplication (including the case where λ=0+) and pointwise addition.
相似文献
102.
A. A. Maleev 《Computational Mathematics and Mathematical Physics》2006,46(12):2031-2039
Stationary and nonstationary Jacobi-like iterative processes for solving systems of linear algebraic equations are examined. For a system whose coefficient matrix A is an H-matrix, it is shown that the convergence rate of any Jacobi-like process is at least as high as that of the point Jacobi method as applied to a system with 〈A〉 as the coefficient matrix, where 〈A〉 is a comparison matrix of A. 相似文献
103.
Ivan Kojadinovic 《4OR: A Quarterly Journal of Operations Research》2007,5(2):117-142
The application of multi-attribute utility theory based on the Choquet integral requires the prior identification of a capacity
if the utility scale is unipolar, or of a bi-capacity if the utility scale is bipolar. In order to implement a minimum distance
principle for capacity or bi-capacity approximation or identification, quadratic distances between capacities and bi-capacities
are studied. The proposed approach, consisting in solving a strictly convex quadratic program, has been implemented within
the GNU R kappalab package for capacity and nonadditive integral manipulation. Its application is illustrated on two examples.
相似文献
104.
Valentin Brimkov 《Discrete Applied Mathematics》2007,155(14):1812-1825
We consider the problem of computing the Lovász theta function for circulant graphs Cn,J of degree four with n vertices and chord length J, 2?J?n. We present an algorithm that takes O(J) operations if J is an odd number, and O(n/J) operations if J is even. On the considered class of graphs our algorithm strongly outperforms the known algorithms for theta function computation. We also provide explicit formulas for the important special cases J=2 and J=3. 相似文献
105.
G.J. Zalmai Qing-hong Zhang 《应用数学学报(英文版)》2007,23(2):217-234
In this paper,we discuss a large number of sets of global parametric sufficient optimality condi-tions under various gcneralized (η,ρ)-invexity assumptions for a semi-infinite minmax fractional programmingproblem. 相似文献
106.
Vicky Mak 《Operations Research Letters》2007,35(1):36-44
This paper, using the Unconstrained Shape Matrix Optimization Problem as a test bed, we investigate various aspects of variable aggregation and disaggregation for a class of integer programs that contains binary expansion. We present theoretical and numerical results, and propose an iterative algorithm for exact solutions. 相似文献
107.
108.
Patrizio Frosini 《Geometriae Dedicata》2004,108(1):105-110
In this paper we prove that for every real-valued Morse function φ on a smooth closed manifold ℳ and every neighborhood U of its critical points a suitable Riemannian metric μ
U
exists such that φ is linear outside
U 相似文献
109.
This paper develops a theory for the global solution of nonconvex optimization problems with parameter-embedded linear dynamic systems. A quite general problem formulation is introduced and a solution is shown to exists. A convexity theory for integrals is then developed to construct convex relaxations for utilization in a branch-and-bound framework to calculate a global minimum. Interval analysis is employed to generate bounds on the state variables implied by the bounds on the embedded parameters. These bounds, along with basic integration theory, are used to prove convergence of the branch-and-bound algorithm to the global minimum of the optimization problem. The implementation of the algorithm is then considered and several numerical case studies are examined thoroughly 相似文献
110.
Mixed integer programming (MIP) models are extensively usedto aid strategic and tactical decision making in many businesssectors. Solving MIP models is a computationally intensive processand there is a need to develop solution approaches that enablelarger models to be solved within acceptable timeframes. Inthis paper, we describe the implementation of a two-stage parallelbranch and bound (PB & B) algorithm for MIP. In stage 1of the algorithm, a multiple heuristic search is implementedin which a number of alternative search trees are investigatedusing a forest search in the hope of finding a good solutionquickly. In stage 2, the search is reorganized so that the branchesof a chosen tree are investigated in parallel. A new heuristicis introduced, based on a best projection criterion, which evaluatesalternative B & B trees in order to choose one for investigationin stage 2 of the algorithm. The heuristic also serves as away of implementing a quality load balancing scheme for stage2 of the algorithm. The results of experimental investigationsare reported for a range of models taken from the MIPLIB libraryof benchmark problems. 相似文献