全文获取类型
收费全文 | 12766篇 |
免费 | 1209篇 |
国内免费 | 542篇 |
专业分类
化学 | 1471篇 |
晶体学 | 32篇 |
力学 | 1341篇 |
综合类 | 241篇 |
数学 | 9718篇 |
物理学 | 1714篇 |
出版年
2024年 | 29篇 |
2023年 | 131篇 |
2022年 | 255篇 |
2021年 | 387篇 |
2020年 | 295篇 |
2019年 | 310篇 |
2018年 | 354篇 |
2017年 | 473篇 |
2016年 | 453篇 |
2015年 | 315篇 |
2014年 | 585篇 |
2013年 | 847篇 |
2012年 | 743篇 |
2011年 | 630篇 |
2010年 | 579篇 |
2009年 | 706篇 |
2008年 | 719篇 |
2007年 | 806篇 |
2006年 | 676篇 |
2005年 | 582篇 |
2004年 | 468篇 |
2003年 | 472篇 |
2002年 | 439篇 |
2001年 | 401篇 |
2000年 | 371篇 |
1999年 | 296篇 |
1998年 | 297篇 |
1997年 | 267篇 |
1996年 | 192篇 |
1995年 | 208篇 |
1994年 | 166篇 |
1993年 | 138篇 |
1992年 | 126篇 |
1991年 | 106篇 |
1990年 | 92篇 |
1989年 | 70篇 |
1988年 | 60篇 |
1987年 | 46篇 |
1986年 | 43篇 |
1985年 | 66篇 |
1984年 | 64篇 |
1983年 | 17篇 |
1982年 | 32篇 |
1981年 | 29篇 |
1980年 | 35篇 |
1979年 | 39篇 |
1978年 | 24篇 |
1977年 | 36篇 |
1976年 | 19篇 |
1957年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
111.
Discrete global descent method for discrete global optimization and nonlinear integer programming 总被引:2,自引:0,他引:2
A novel method, entitled the discrete global descent method, is developed in this paper to solve discrete global optimization
problems and nonlinear integer programming problems. This method moves from one discrete minimizer of the objective function
f to another better one at each iteration with the help of an auxiliary function, entitled the discrete global descent function.
The discrete global descent function guarantees that its discrete minimizers coincide with the better discrete minimizers
of f under some standard assumptions. This property also ensures that a better discrete minimizer of f can be found by some classical local search methods. Numerical experiments on several test problems with up to 100 integer
variables and up to 1.38 × 10104 feasible points have demonstrated the applicability and efficiency of the proposed method. 相似文献
112.
文章建立一个随机内生增长模型来阐明主要政策参数对经济增长与社会福利的影响.若对生产函数、效用函数、偏好及随机干扰作一些特殊的假设,我们证明了主要政策参数的均衡值能被模型参数唯一决定.进一步我们还得到了期望增长率与储蓄的清晰解.文章的最后,我们证明了政府支出直接影响个体决策者的决策:即提高经济增长率将减少福利;反之,增加福利将减少增长率. 相似文献
113.
In this note we show that many classes of global optimization problems can be treated most satisfactorily by classical optimization theory and conventional algorithms. We focus on the class of problems involving the minimization of the product of several convex functions on a convex set which was studied recently by Kunoet al. [3]. It is shown that these problems are typical composite concave programming problems and thus can be handled elegantly by c-programming [4]–[8] and its techniques. 相似文献
114.
章志飞 《浙江大学学报(理学版)》2003,30(6):609-611
利用Besov空间的热核刻画及压缩映射原理,研究半线性热方程ut-△u=u|u|a的初值问题,得到了当初值u0∈Lp0(Rn)且||u0||(B·)p-n (1/p0-1/p),∞(Rn)(p0=na/2,p>p0)充分小时,整体解的存在性及在一定条件下解的惟一性. 相似文献
115.
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
116.
Adam B. Levy 《Mathematical Programming》2007,110(3):615-639
Numerical methods for solving constrained optimization problems need to incorporate the constraints in a manner that satisfies
essentially competing interests; the incorporation needs to be simple enough that the solution method is tractable, yet complex
enough to ensure the validity of the ultimate solution. We introduce a framework for constraint incorporation that identifies
a minimal acceptable level of complexity and defines two basic types of constraint incorporation which (with combinations)
cover nearly all popular numerical methods for constrained optimization, including trust region methods, penalty methods,
barrier methods, penalty-multiplier methods, and sequential quadratic programming methods. The broad application of our framework
relies on addition and chain rules for constraint incorporation which we develop here. 相似文献
117.
Iasson Karafyllis 《Journal of Mathematical Analysis and Applications》2007,328(2):876-899
A system-theoretic framework is proposed, which allows the study of hybrid uncertain systems, which do not satisfy the so-called “semigroup property.” Characterizations of the notion of robust global asymptotic output stability (RGAOS) are given. Based on the provided characterizations, the qualitative behavior of hybrid systems obtained by time-discretization of systems of ordinary differential equations with a globally asymptotically stable equilibrium point, is studied. 相似文献
118.
Ansgar Jüngel 《Mathematische Nachrichten》1997,185(1):85-110
A multi-dimensional transient drift-diffusion model for (at most) three charged particles, consisting of the continuity equations for the concentrations of the species and the Poisson equation for the electric potential, is considered. The diffusion terms depend on the concentrations. Such a system arises in electrophoretic modeling of three species (neutrally, positively and negatively charged) and in semiconductor theory for two species (positively charged holes and negatively charged electrons). Diffusion terms of degenerate type are also possible in semiconductor modeling. For the initial boundary value problem with mixed Dirichlet - Neumann boundary conditions and general reaction rates, a global existence result is proved. Uniqueness of solutions follows in the Dirichlet boundary case if the diffusion terms are uniformly parabolic or if the initial and boundary densities are strictly positive. Finally, we prove that solutions exist which are positive uniformly in time and globally bounded if the reaction rates satisfy appropriate growth conditions. 相似文献
119.
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
120.