全文获取类型
收费全文 | 9879篇 |
免费 | 730篇 |
国内免费 | 276篇 |
专业分类
化学 | 1318篇 |
晶体学 | 31篇 |
力学 | 1098篇 |
综合类 | 151篇 |
数学 | 6767篇 |
物理学 | 1520篇 |
出版年
2024年 | 22篇 |
2023年 | 103篇 |
2022年 | 334篇 |
2021年 | 335篇 |
2020年 | 208篇 |
2019年 | 223篇 |
2018年 | 246篇 |
2017年 | 328篇 |
2016年 | 312篇 |
2015年 | 230篇 |
2014年 | 457篇 |
2013年 | 555篇 |
2012年 | 616篇 |
2011年 | 475篇 |
2010年 | 446篇 |
2009年 | 553篇 |
2008年 | 551篇 |
2007年 | 600篇 |
2006年 | 488篇 |
2005年 | 433篇 |
2004年 | 337篇 |
2003年 | 318篇 |
2002年 | 290篇 |
2001年 | 268篇 |
2000年 | 263篇 |
1999年 | 193篇 |
1998年 | 213篇 |
1997年 | 196篇 |
1996年 | 137篇 |
1995年 | 161篇 |
1994年 | 133篇 |
1993年 | 111篇 |
1992年 | 101篇 |
1991年 | 86篇 |
1990年 | 75篇 |
1989年 | 61篇 |
1988年 | 48篇 |
1987年 | 40篇 |
1986年 | 38篇 |
1985年 | 54篇 |
1984年 | 51篇 |
1983年 | 15篇 |
1982年 | 22篇 |
1981年 | 22篇 |
1980年 | 17篇 |
1979年 | 32篇 |
1978年 | 20篇 |
1977年 | 29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 31 毫秒
51.
Suthep?SuantaiEmail author Chanan?Sudsukh 《Southeast Asian Bulletin of Mathematics》2003,26(4):637-650
In this paper, we give the matrix characterizations from any normal vector-valued FK-space containing ø(X) into scalar-valued sequence space c(q) and by applying this result, we also obtain necessary and sufficient conditions for infinite matrices mapping the sequence spaces
, and Fr(X,p) into the space c(q), where p = (pk) and q = (qk) are bounded sequences of positive real numbers and r ≥ 0.AMS Subject Classification (2000): 46A45. 相似文献
52.
We address the problem of finding the worst possible traffic a
user of a telecommunications network can send.
We take worst to mean having the highest effective
bandwidth, a concept that arises in the Large Deviation theory of
queueing networks.
The traffic is assumed to be stationary and to satisfy leaky bucket
constraints, which represent the a priori knowledge the network
operator has concerning the traffic.
Firstly, we show that this optimization problem may be reduced to an
optimization over periodic traffic sources.
Then, using convexity methods, we show that the realizations of a
worst case source must have the following properties:
at each instant the transmission rate must be either zero,
the peak rate, or the leaky bucket rate; it may only be the latter when
the leaky bucket is empty or full;
each burst of activity must either start with the leaky
bucket empty or end with it full. 相似文献
53.
Victor A. Kovtunenko 《Mathematical Methods in the Applied Sciences》2003,26(5):359-374
The 3D‐elasticity model of a solid with a plane crack under the stress‐free boundary conditions at the crack is considered. We investigate variations of a solution and of energy functionals with respect to perturbations of the crack front in the plane. The corresponding expansions at least up to the second‐order terms are obtained. The strong derivatives of the solution are constructed as an iterative solution of the same elasticity problem with specified right‐hand sides. Using the expansion of the potential and surface energy, we consider an approximate quadratic form for local shape optimization of the crack front defined by the Griffith criterion. To specify its properties, a procedure of discrete optimization is proposed, which reduces to a matrix variational inequality. At least for a small load we prove its solvability and find a quasi‐static model of the crack growth depending on the loading parameter. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
54.
Abdulaziz S. Alidi 《Applied Mathematical Modelling》1992,16(12):645-651
The improper handling and disposal of hazardous wastes cause threats to human health and the environment. One reason for the improper handling and disposal of these wastes is that not much consideration is usually given to the logistical aspects of hazardous waste systems. In this paper an integer goal programming model is developed that takes into consideration the multiple goals and needs of many groups involved in managing and planning hazardous waste systems. The model can easily be implemented and can be used to address many of the issues related to facility location, recycling, treatment, and disposal of hazardous wastes. 相似文献
55.
This paper presents an algorithm and the supporting theory for solving a class of nonlinear multiple criteria optimization problems using Zionts—Wallenius type of interaction. The Zionts—Wallenius method, as extended in this paper, can be used for solving multiple criteria problems with concave objective and (implicit) value functions and convex feasible regions. Modifications of the method to handle nonconvex feasible regions and general nonlinear objective functions are also discussed.This research was supported, in part, by a Faculty Research Development Award and by a Council of 100 Research Grant from Arizona State University (Roy), and by a grant from Y. Jahnsson Foundation, Finland (Wallenius). The research was performed while the second author was a Visiting Professor at Arizona State University. 相似文献
56.
In this paper we propose a recursive quadratic programming algorithm for nonlinear programming problems with inequality constraints that uses as merit function a differentiable exact penalty function. The algorithm incorporates an automatic adjustment rule for the selection of the penalty parameter and makes use of an Armijo-type line search procedure that avoids the need to evaluate second order derivatives of the problem functions. We prove that the algorithm possesses global and superlinear convergence properties. Numerical results are reported. 相似文献
57.
A. Zochowski 《Journal of Optimization Theory and Applications》1992,73(2):387-407
A method for computing the sensitivities of functionals depending on the solutions of elliptic equations defined over variable domains is presented. It is based on the material derivative approach and allows the uniform treatment of both singular and nonsingular cases. The novelty consists in defining the vector field connected with the domain transformation as the solution of an auxiliary elliptic equation. Such a choice does not restrict the range of admissible goal functionals and has many advantages from the numerical point of view. It allows one also to consider singular domain variations. 相似文献
58.
A. Žilinskas 《Journal of Global Optimization》1992,2(2):145-153
A review of statistical models for global optimization is presented. Rationality of the search for a global minimum is formulated axiomatically and the features of the corresponding algorithm are derived from the axioms. Furthermore the results of some applications of the proposed algorithm are presented and the perspectives of the approach are discussed. 相似文献
59.
Unconstrained and constrained global optimization of polynomial functions in one variable 总被引:1,自引:0,他引:1
In Floudas and Visweswaran (1990), a new global optimization algorithm (GOP) was proposed for solving constrained nonconvex problems involving quadratic and polynomial functions in the objective function and/or constraints. In this paper, the application of this algorithm to the special case of polynomial functions of one variable is discussed. The special nature of polynomial functions enables considerable simplification of the GOP algorithm. The primal problem is shown to reduce to a simple function evaluation, while the relaxed dual problem is equivalent to the simultaneous solution of two linear equations in two variables. In addition, the one-to-one correspondence between the x and y variables in the problem enables the iterative improvement of the bounds used in the relaxed dual problem. The simplified approach is illustrated through a simple example that shows the significant improvement in the underestimating function obtained from the application of the modified algorithm. The application of the algorithm to several unconstrained and constrained polynomial function problems is demonstrated. 相似文献
60.
基于增广Lagrange函数的RQP方法 总被引:3,自引:0,他引:3
Recursive quadratic programming is a family of techniques developd by Bartholomew-Biggs and other authors for solving nonlinear programming problems.This paperdescribes a new method for constrained optimization which obtains its search di-rections from a quadratic programming subproblem based on the well-known aug-mented Lagrangian function.It avoids the penalty parameter to tend to infinity.We employ the Fletcher‘s exact penalty function as a merit function and the use of an approximate directional derivative of the function that avoids the need toevaluate the second order derivatives of the problem functions.We prove that thealgorithm possesses global and superlinear convergence properties.At the sametime, numerical results are reported. 相似文献