全文获取类型
收费全文 | 14460篇 |
免费 | 977篇 |
国内免费 | 810篇 |
专业分类
化学 | 206篇 |
晶体学 | 2篇 |
力学 | 1442篇 |
综合类 | 166篇 |
数学 | 13345篇 |
物理学 | 1086篇 |
出版年
2024年 | 30篇 |
2023年 | 142篇 |
2022年 | 165篇 |
2021年 | 202篇 |
2020年 | 316篇 |
2019年 | 325篇 |
2018年 | 379篇 |
2017年 | 385篇 |
2016年 | 377篇 |
2015年 | 276篇 |
2014年 | 611篇 |
2013年 | 1152篇 |
2012年 | 651篇 |
2011年 | 766篇 |
2010年 | 679篇 |
2009年 | 941篇 |
2008年 | 988篇 |
2007年 | 1020篇 |
2006年 | 898篇 |
2005年 | 698篇 |
2004年 | 600篇 |
2003年 | 668篇 |
2002年 | 575篇 |
2001年 | 433篇 |
2000年 | 444篇 |
1999年 | 393篇 |
1998年 | 363篇 |
1997年 | 324篇 |
1996年 | 248篇 |
1995年 | 204篇 |
1994年 | 138篇 |
1993年 | 119篇 |
1992年 | 120篇 |
1991年 | 104篇 |
1990年 | 79篇 |
1989年 | 38篇 |
1988年 | 41篇 |
1987年 | 38篇 |
1986年 | 41篇 |
1985年 | 54篇 |
1984年 | 53篇 |
1983年 | 28篇 |
1982年 | 28篇 |
1981年 | 25篇 |
1980年 | 18篇 |
1979年 | 21篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1976年 | 9篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
161.
W. Brüggemann K. Fischer H. Jahnke 《Journal of Mathematical Modelling and Algorithms》2003,2(2):153-169
In Part I of this study, we suggest to identify an operations research (OR) problem with the equivalence class of models describing the problem and enhance the standard computer-science theory of computational complexity to be applicable to this situation of an often model-based OR context. The Discrete Lot-sizing and Scheduling Problem (DLSP) is analysed here in detail to demonstrate the difficulties which can arise if these aspects are neglected and to illustrate the new theoretical concept. In addition, a new minimal model is introduced for the DLSP which makes this problem eventually amenable to a rigorous analysis of its computational complexity. 相似文献
162.
An initial boundary value problem for the dynamic system of anisotropic elasticity in a half space is studied in the paper. A novel method of finding an exact solution of this problem for a special polynomial form of initial data and inhomogeneous term of the system is described. On the base of this method the simulation of elastic waves in different homogeneous anisotropic half spaces is implemented. 相似文献
163.
一类特殊二维0-1规划的广义指派模型求解 总被引:2,自引:2,他引:0
二维0-1整数规划模型应用广泛,对广义指派问题的研究,解决了一些二维0-1整数规划问题.但有些实际问题具有特殊上限约束,目前还没有对应的方法.针对该实际情形,本文建立了相应的数学模型,利用对指派模型的推广,求得问题最优解,从理论上解决了这一类特殊约束二维0-1整数规划的最优解求取问题.并通过算例说明了方法的使用. 相似文献
164.
本针对P0函数互补问题,给出了一种微方程方法,并且证明了P0函数互补问题的解是微分方程系统的渐进稳定平衡点。在适当的假设条件下,证明了所给出的算法具有二次收敛速度。几个数值例子表明了该算法的有效性。 相似文献
165.
§ 1 IntroductionConsiderthefollowingnonlinearoptimizationproblem :minimizef(x)subjecttoC(x) =0 , a≤x≤b ,( 1 .1 )wheref(x) :Rn→R ,C(x) =(c1(x) ,c2 (x) ,...,cm(x) ) T:Rn→Rm aretwicecontinuouslydifferentiable,m≤n ,a ,b∈Rn.Trustregionalgorithmsareveryeffectiveforsolvingnonlinearoptimi… 相似文献
166.
Manufacturing cell formation using similarity coefficients and a parallel genetic TSP algorithm: Formulation and comparison 总被引:2,自引:0,他引:2
J. BalakrishnanP. D. Jog 《Mathematical and Computer Modelling》1995,21(12):61-73
Many algorithms have been proposed to form manufacturing cells from component routings. However, many of these do not have the capability of solving large problems. We propose a procedure using similarity coefficients and a parallel genetic implementation of a TSP algorithm that is capable of solving large problems of up to 1000 parts and 1000 machines. In addition, we also compare our procedure with many existing procedures using nine well-known problems from the literature.
The results show that the proposed procedure compares well with the existing procedures and should be useful to practitioners and researchers. 相似文献
167.
This note outlines an algorithm for solving the complex ‘matrix Procrustes problem’. This is a least‐squares approximation over the cone of positive semi‐definite Hermitian matrices, which has a number of applications in the areas of Optimization, Signal Processing and Control. The work generalizes the method of Allwright (SIAM J. Control Optim. 1988; 26 (3):537–556), who obtained a numerical solution to the real‐valued version of the problem. It is shown that, subject to an appropriate rank assumption, the complex problem can be formulated in a real setting using a matrix‐dilation technique, for which the method of Allwright is applicable. However, this transformation results in an over‐parametrization of the problem and, therefore, convergence to the optimal solution is slow. Here, an alternative algorithm is developed for solving the complex problem, which exploits fully the special structure of the dilated matrix. The advantages of the modified algorithm are demonstrated via a numerical example. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
168.
The main goal of this paper is to compute the Figure-eight solutions for the planar Newtonian 3-body problem with equal masses by finding the critical points of the functional associated with the motion equations of 3-body in plane R2. The algorithm adopted here is the steepest descent method, which is simple but very valid for our problem. 相似文献
169.
In this paper, the notion of gap functions is extended from scalar case to vector one. Then, gap functions and generalized
functions for several kinds of vector equilibrium problems are shown. As an application, the dual problem of a class of optimization
problems with a system of vector equilibrium constraints (in short, OP) is established, the concavity of the dual function,
the weak duality of (OP) and the saddle point sufficient condition are derived by using generalized gap functions.
This work was supported by the National Natural Science Foundation of China (10671135) and the Applied Research Project of
Sichuan Province (05JY029-009-1). 相似文献
170.
Alexander J. Zaslavski 《Journal of Mathematical Analysis and Applications》2007,335(2):962-973
The Tonelli existence theorem in the calculus of variations and its subsequent modifications were established for integrands f which satisfy convexity and growth conditions. In this paper we consider a large class of optimal control problems which is identified with a complete metric space of integrands without convexity assumptions and show that for a generic integrand the corresponding optimal control problem possesses a unique solution and this solution is Lipschitzian. 相似文献