全文获取类型
收费全文 | 560篇 |
免费 | 16篇 |
国内免费 | 17篇 |
专业分类
化学 | 11篇 |
力学 | 30篇 |
数学 | 508篇 |
物理学 | 44篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 9篇 |
2020年 | 9篇 |
2019年 | 17篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 13篇 |
2015年 | 10篇 |
2014年 | 24篇 |
2013年 | 57篇 |
2012年 | 33篇 |
2011年 | 39篇 |
2010年 | 32篇 |
2009年 | 41篇 |
2008年 | 41篇 |
2007年 | 38篇 |
2006年 | 24篇 |
2005年 | 20篇 |
2004年 | 22篇 |
2003年 | 19篇 |
2002年 | 16篇 |
2001年 | 9篇 |
2000年 | 11篇 |
1999年 | 11篇 |
1998年 | 17篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 10篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有593条查询结果,搜索用时 15 毫秒
101.
《Optimization》2012,61(1):53-63
In this article, following the idea used by Göpfert et al . [A. Göpfert, Chr. Tammer and C. Zalinescu (2000). On the vectorial Ekeland's variational principle and minimal points in product spaces. Nonlinear Analysis, Theory, Methods & Applications , 39 , 909-922] to derive an Ekeland's variational principle for vector-valued functions, we derive a new variant of Ekeland's variational principle for set-valued maps. Finally, we apply this variational principle to obtain an approximate necessary optimality condition for a class of set-valued optimization problems. 相似文献
102.
ABSTRACTThe purpose of these notes is to generalize and extend a challenging geometry problem from a mathematics competition. The notes also contain solution sketches pertaining to the problems discussed. 相似文献
103.
Hans-Jörg SchützRainer Kolisch 《European Journal of Operational Research》2012,218(1):239-250
We consider a problem where different classes of customers can book different types of service in advance and the service company has to respond immediately to the booking request confirming or rejecting it. The objective of the service company is to maximize profit made of class-type specific revenues, refunds for cancellations or no-shows as well as cost of overtime. For the calculation of the latter, information on the underlying appointment schedule is required. In contrast to most models in the literature we assume that the service time of clients is stochastic and that clients might be unpunctual. Throughout the paper we will relate the problem to capacity allocation in radiology services. The problem is modeled as a continuous-time Markov decision process and solved using simulation-based approximate dynamic programming (ADP) combined with a discrete event simulation of the service period. We employ an adapted heuristic ADP algorithm from the literature and investigate on the benefits of applying ADP to this type of problem. First, we study a simplified problem with deterministic service times and punctual arrival of clients and compare the solution from the ADP algorithm to the optimal solution. We find that the heuristic ADP algorithm performs very well in terms of objective function value, solution time, and memory requirements. Second, we study the problem with stochastic service times and unpunctuality. It is then shown that the resulting policy constitutes a large improvement over an “optimal” policy that is deduced using restrictive, simplifying assumptions. 相似文献
104.
In the controlled ovarian hyperstimulation (COH) treatment, clinicians monitor the patients’ physiological responses to gonadotropin administration to tradeoff between pregnancy probability and ovarian hyperstimulation syndrome (OHSS). We formulate the dosage control problem in the COH treatment as a stochastic dynamic program and design approximate dynamic programming (ADP) algorithms to overcome the well-known curses of dimensionality in Markov decision processes (MDP). Our numerical experiments indicate that the piecewise linear (PWL) approximation ADP algorithms can obtain policies that are very close to the one obtained by the MDP benchmark with significantly less solution time. 相似文献
105.
C. Pruett 《Theoretical and Computational Fluid Dynamics》2008,22(3-4):275-304
Large-eddy simulation (LES) has relied almost exclusively on spatial filtering to separate resolved and unresolved scales.
For many reasons, temporal filtering may be more natural, particularly for flows of engineering interest. The paper develops
the theory of temporal LES (TLES) and provides a demonstration of the concept by simulations of viscous Burger’s flow and
incompressible plane-channel flow. The latter is accomplished by adapting the approximate deconvolution model (ADM) of Stolz
and Adams (Phys. Fluids 11:1699, 1999) to causal, time-domain filtering. The temporal variant of the ADM is termed the TADM.
相似文献
106.
Approximate solutions for optimization problems become of interest if the ‘true’ optimum cannot be found: this may happen for the simple reason that an optimum does not exist or because of the ‘bounded rationality’ (or bounded accuracy) of the optimizer. This paper characterizes several approximate solutions by means of consistency and additional requirements. In particular we consider invariance properties. We prove that, where the domain contains optimization problems without maximum, there is no non-trivial consistent solution satisfying non-emptiness, translation and multiplication invariance. Moreover, we show that the class of ‘satisficing’ solutions is obtained, if the invariance axioms are replaced with Chernoff’s Choice Axiom. 相似文献
107.
In this paper, we establish three iteration methods to compute solutions for a class of (weakly) singular two-point boundary value problems (xy′)′=f(x,y), where x(0,1) and <2. We obtain the sufficient conditions for existence of a unique solution on
. Finally, we given some numerical examples. 相似文献
108.
M. W. Smiley 《Journal of Dynamics and Differential Equations》1995,7(2):237-262
The existence of a nonautonomous approximate inertial manifold is shown for problems of the formu + Au + N(t,u)=0, in whichA is a self-adjoint operator with compact resolvent in a Hilbert spaceH. The operatorN(t, u) = G(u) + F(t, u) is nonlinear withG a monotone gradient that is locally Lipschitz fromD(A
1/2) intoH, andF:+×HH a Lipschitz perturbation that is Hölder continuous int. Weak solutions are shown to be uniformly locally Hölder continuous intoD(A) with equicontinuity in families of solutions with ¦u(0)¦ r.A priori estimates of ¦Au(t)¦ are also verified and used in a skew-product flow to show there is a global attractor whose component elements form a equicontinuous family of solutions. 相似文献
109.
In this paper, we consider the non-autonomous semilinear impulsive differential equations with state-dependent delay. The approximate controllability results of the first-order systems are obtained in a separable reflexive Banach space, which has a uniformly convex dual. In order to establish sufficient conditions of the approximate controllability of such a system, we have used the theory of linear evolution systems, properties of the resolvent operator and Schauder’s fixed point theorem. Finally, we provide two concrete examples to validate our results. 相似文献
110.
THE SOLVABILITY CONDITIONS FOR INVERSE EIGENVALUE PROBLEM OF ANTI-BISYMMETRIC MATRICES 总被引:3,自引:0,他引:3
Dong-xiu Xie 《计算数学(英文版)》2002,(3)
AbstractThis paper is mainly concerned with solving the following two problems: Problem I. Given X Cnxm, A = diag( 1, 2, ..... , m) Cmxm . Find A ABSRnxn such thatAX = XAwhere ABSRnxn is the set of all real n x n anti-bisymmetric matrices. Problem II. Given A RnXn. Find A SE such thatwhere || || is Frobenius norm, and SE denotes the solution set of Problem I.The necessary and sufficient conditions for the solvability of Problem I have been studied. The general form of SB has been given. For Problem II the expression of the solution has been provided. 相似文献