全文获取类型
收费全文 | 11209篇 |
免费 | 810篇 |
国内免费 | 379篇 |
专业分类
化学 | 1695篇 |
晶体学 | 33篇 |
力学 | 1241篇 |
综合类 | 163篇 |
数学 | 7303篇 |
物理学 | 1963篇 |
出版年
2024年 | 22篇 |
2023年 | 122篇 |
2022年 | 359篇 |
2021年 | 361篇 |
2020年 | 231篇 |
2019年 | 260篇 |
2018年 | 275篇 |
2017年 | 366篇 |
2016年 | 359篇 |
2015年 | 280篇 |
2014年 | 518篇 |
2013年 | 711篇 |
2012年 | 683篇 |
2011年 | 540篇 |
2010年 | 497篇 |
2009年 | 639篇 |
2008年 | 640篇 |
2007年 | 669篇 |
2006年 | 571篇 |
2005年 | 480篇 |
2004年 | 378篇 |
2003年 | 357篇 |
2002年 | 336篇 |
2001年 | 300篇 |
2000年 | 300篇 |
1999年 | 239篇 |
1998年 | 236篇 |
1997年 | 229篇 |
1996年 | 157篇 |
1995年 | 182篇 |
1994年 | 154篇 |
1993年 | 128篇 |
1992年 | 124篇 |
1991年 | 91篇 |
1990年 | 82篇 |
1989年 | 66篇 |
1988年 | 53篇 |
1987年 | 48篇 |
1986年 | 40篇 |
1985年 | 59篇 |
1984年 | 52篇 |
1983年 | 19篇 |
1982年 | 24篇 |
1981年 | 22篇 |
1980年 | 17篇 |
1979年 | 32篇 |
1978年 | 21篇 |
1977年 | 30篇 |
1976年 | 19篇 |
1974年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Grigor'ev S. A. Kalinnikov A. A. Porembskii V. I. Baranov I. E. Borisova E. V. Fateev V. N. 《Russian Journal of Electrochemistry》2004,40(11):1188-1192
A two-dimensional mathematical model for the transport of reactants in a fuel cell with a solid polymer electrolyte is developed. The model is used for analyzing spatial distributions of the concentration of reactants and current density over the cell. The effect of the catalytic-layer activity, reactant speed, bipolar-plate geometry, thickness and porosity of current collector and/or gas-diffusion sublayer, and the reaction mixture composition on the fuel cell efficiency is estimated theoretically and experimentally. 相似文献
32.
We introduce extensions of the Mangasarian-Fromovitz and Abadie constraint qualifications to nonsmooth optimization problems with feasibility given by means of lower-level sets. We do not assume directional differentiability, but only upper semicontinuity of the defining functions. By deriving and reviewing primal first-order optimality conditions for nonsmooth problems, we motivate the formulations of the constraint qualifications. Then, we study their interrelation, and we show how they are related to the Slater condition for nonsmooth convex problems, to nonsmooth reverse-convex problems, to the stability of parametric feasible set mappings, and to alternative theorems for the derivation of dual first-order optimality conditions.In the literature on general semi-infinite programming problems, a number of formally different extensions of the Mangasarian-Fromovitz constraint qualification have been introduced recently under different structural assumptions. We show that all these extensions are unified by the constraint qualification presented here. 相似文献
33.
By extracting combinatorial structures in well-solved nonlinear combinatorial optimization problems, Murota (1996,1998) introduced the concepts of M-convexity and L-convexity to functions defined over the integer lattice. Recently, Murota–Shioura (2000, 2001) extended these concepts to polyhedral convex functions and quadratic functions in continuous variables. In this paper, we consider a further extension to more general convex functions defined over the real space, and provide a proof for the conjugacy relationship between general M-convex and L-convex functions.Mathematics Subject Classification (1991): 90C10, 90C25, 90C27, 90C35This work is supported by Grant-in-Aid of the Ministry of Education, Culture, Sports, Science and Technology of Japan 相似文献
34.
Many real problems can be modelled as robust shortest path problems on interval digraphs, where intervals represent uncertainty about real costs and a robust path is not too far from the shortest path for each possible configuration of the arc costs.A branch and bound algorithm for this problem is presented. 相似文献
35.
Robust linear optimization under general norms 总被引:1,自引:0,他引:1
We explicitly characterize the robust counterpart of a linear programming problem with uncertainty set described by an arbitrary norm. Our approach encompasses several approaches from the literature and provides guarantees for constraint violation under probabilistic models that allow arbitrary dependencies in the distribution of the uncertain coefficients. 相似文献
36.
Asaf Levin 《Operations Research Letters》2004,32(6):530-534
Consider the following problem: given a ground set and two minimization objectives of the same type find a subset from a given subset-class that minimizes the first objective subject to a budget constraint on the second objective. Using Megiddo's parametric method we improve an earlier weakly polynomial time algorithm. 相似文献
37.
Alvim Adriana C.F. Ribeiro Celso C. Glover Fred Aloise Dario J. 《Journal of Heuristics》2004,10(2):205-229
We propose in this work a hybrid improvement procedure for the bin packing problem. This heuristic has several features: the use of lower bounding strategies; the generation of initial solutions by reference to the dual min-max problem; the use of load redistribution based on dominance, differencing, and unbalancing; and the inclusion of an improvement process utilizing tabu search. Encouraging results have been obtained for a very wide range of benchmark instances, illustrating the robustness of the algorithm. The hybrid improvement procedure compares favourably with all other heuristics in the literature. It improved the best known solutions for many of the benchmark instances and found the largest number of optimal solutions with respect to the other available approximate algorithms. 相似文献
38.
单调优化是指目标函数与约束函数均为单调函数的全局优化问题.本文提出一种新的凸化变换方法把单调函数化为凸函数,进而把单调优化问题化为等价的凸极大或凹极小问题,然后采用Hoffman的外逼近方法来求得问题的全局最优解.我们把这种凸化方法同Tuy的Polyblock外逼近方法作了比较,通过数值比较可以看出本文提出的凸化的方法在收敛速度上明显优于Polyblock方法. 相似文献
39.
40.
Gabriele Bonanno 《Journal of Global Optimization》1998,12(1):101-104
In this note we introduce a suitable class of functionals, including the class of integral functionals, and prove that any (strict) local minimum of a functional of this class, defined on a decomposable space, is a (strict) global minimum. So, the recent result obtained by Giner in [1] is specified and extended. 相似文献