全文获取类型
收费全文 | 2795篇 |
免费 | 101篇 |
国内免费 | 74篇 |
专业分类
化学 | 194篇 |
晶体学 | 2篇 |
力学 | 143篇 |
综合类 | 27篇 |
数学 | 2289篇 |
物理学 | 315篇 |
出版年
2024年 | 2篇 |
2023年 | 24篇 |
2022年 | 37篇 |
2021年 | 43篇 |
2020年 | 34篇 |
2019年 | 33篇 |
2018年 | 30篇 |
2017年 | 33篇 |
2016年 | 48篇 |
2015年 | 40篇 |
2014年 | 82篇 |
2013年 | 122篇 |
2012年 | 97篇 |
2011年 | 107篇 |
2010年 | 116篇 |
2009年 | 176篇 |
2008年 | 206篇 |
2007年 | 234篇 |
2006年 | 165篇 |
2005年 | 138篇 |
2004年 | 118篇 |
2003年 | 117篇 |
2002年 | 115篇 |
2001年 | 87篇 |
2000年 | 83篇 |
1999年 | 77篇 |
1998年 | 89篇 |
1997年 | 60篇 |
1996年 | 61篇 |
1995年 | 40篇 |
1994年 | 44篇 |
1993年 | 43篇 |
1992年 | 30篇 |
1991年 | 26篇 |
1990年 | 20篇 |
1989年 | 20篇 |
1988年 | 27篇 |
1987年 | 13篇 |
1986年 | 17篇 |
1985年 | 17篇 |
1984年 | 23篇 |
1983年 | 4篇 |
1982年 | 15篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1975年 | 2篇 |
排序方式: 共有2970条查询结果,搜索用时 15 毫秒
1.
Fabio Schoen 《Journal of Global Optimization》1991,1(3):207-228
In this paper stochastic algorithms for global optimization are reviewed. After a brief introduction on random-search techniques, a more detailed analysis is carried out on the application of simulated annealing to continuous global optimization. The aim of such an analysis is mainly that of presenting recent papers on the subject, which have received only scarce attention in the most recent published surveys. Finally a very brief presentation of clustering techniques is given. 相似文献
2.
Vivek F. Farias 《Operations Research Letters》2006,34(2):180-190
We consider a problem of allocating limited quantities of M types of resources among N independent activities that evolve over T epochs. In each epoch, we assign to each activity a task which consumes resources, generates utility, and determines the subsequent state of the activity. We study the complexity of, and approximation algorithms for, maximizing average utility. 相似文献
3.
Dual fractional cutting plane algorithms, in which cutting planes are used to iteratively tighten a linear relaxation of an integer program,
are well-known and form the basis of the highly successful branch-and-cut method. It is rather less well-known that various primal cutting plane algorithms were developed in the 1960s, for example by Young. In a primal algorithm, the main role of the cutting
planes is to enable a feasible solution to the original problem to be improved. Research on these algorithms has been almost
non-existent.
In this paper we argue for a re-examination of these primal methods. We describe a new primal algorithm for pure 0-1 problems based on strong valid inequalities and give some encouraging computational results. Possible extensions to the case of general
mixed-integer programs are also discussed. 相似文献
4.
This paper is concerned with the implementation and testing of an algorithm for solving constrained least-squares problems. The algorithm is an adaptation to the least-squares case of sequential quadratic programming (SQP) trust-region methods for solving general constrained optimization problems. At each iteration, our local quadratic subproblem includes the use of the Gauss–Newton approximation but also encompasses a structured secant approximation along with tests of when to use this approximation. This method has been tested on a selection of standard problems. The results indicate that, for least-squares problems, the approach taken here is a viable alternative to standard general optimization methods such as the Byrd–Omojokun trust-region method and the Powell damped BFGS line search method. 相似文献
5.
Evolutionary algorithms are applied as problem-independent optimization algorithms. They are quite efficient in many situations. However, it is difficult to analyze even the behavior of simple variants of evolutionary algorithms like the (1+1) EA on rather simple functions. Nevertheless, only the analysis of the expected run time and the success probability within a given number of steps can guide the choice of the free parameters of the algorithms. Here static (1+1) EAs with a fixed mutation probability are compared with dynamic (1+1) EAs with a simple schedule for the variation of the mutation probability. The dynamic variant is first analyzed for functions typically chosen as example-functions for evolutionary algorithms. Afterwards, it is shown that it can be essential to choose the suitable variant of the (1+1) EA. More precisely, functions are presented where each static (1+1) EA has exponential expected run time while the dynamic variant has polynomial expected run time. For other functions it is shown that the dynamic (1+1) EA has exponential expected run time while a static (1+1) EA with a good choice of the mutation probability has polynomial run time with overwhelming probability. 相似文献
6.
The Boltzmann distribution used in the steady-state analysis of the simulated annealing algorithm gives rise to several scale invariant properties. Scale invariance is first presented in the context of parallel independent processors and then extended to an abstract form based on lumping states together to form new aggregate states. These lumped or aggregate states possess all of the mathematical characteristics, forms and relationships of states (solutions) in the original problem in both first and second moments. These scale invariance properties therefore permit new ways of relating objective function values, conditional expectation values, stationary probabilities, rates of change of stationary probabilities and conditional variances. Such properties therefore provide potential applications in analysis, statistical inference and optimization. Directions for future research that take advantage of scale invariance are also discussed. 相似文献
7.
A Modified Quasi-Newton Method for Structured Optimization with Partial Information on the Hessian 总被引:2,自引:0,他引:2
This paper develops a modified quasi-Newton method for structured unconstrained optimization with partial information on the
Hessian, based on a better approximation to the Hessian in current search direction. The new approximation is decided by both
function values and gradients at the last two iterations unlike the original one which only uses the gradients at the last
two iterations. The modified method owns local and superlinear convergence. Numerical experiments show that the proposed method
is encouraging comparing with the methods proposed in [4] for structured unconstrained optimization
Presented at the 6th International Conference on Optimization: Techniques and Applications, Ballarat, Australia, December
9–11, 2004 相似文献
8.
Tor Schoenmeyr David Yu Zhang 《Journal of Algorithms in Cognition, Informatics and Logic》2005,57(2):130-139
The string matching with mismatches problem requires finding the Hamming distance between a pattern P of length m and every length m substring of text T with length n. Fischer and Paterson's FFT-based algorithm solves the problem without error in O(σnlogm), where σ is the size of the alphabet Σ [SIAM–AMS Proc. 7 (1973) 113–125]. However, this in the worst case reduces to O(nmlogm). Atallah, Chyzak and Dumas used the idea of randomly mapping the letters of the alphabet to complex roots of unity to estimate the score vector in time O(nlogm) [Algorithmica 29 (2001) 468–486]. We show that the algorithm's score variance can be substantially lowered by using a bijective mapping, and specifically to zero in the case of binary and ternary alphabets. This result is extended via alphabet remappings to deterministically solve the string matching with mismatches problem with a constant factor of 2 improvement over Fischer–Paterson's method. 相似文献
9.
We consider the problem of minimizing an SC1 function subject to inequality constraints. We propose a local algorithm whose distinguishing features are that: (a) a fast convergence rate is achieved under reasonable assumptions that do not include strict complementarity at the solution; (b) the solution of only linear systems is required at each iteration; (c) all the points generated are feasible. After analyzing a basic Newton algorithm, we propose some variants aimed at reducing the computational costs and, in particular, we consider a quasi-Newton version of the algorithm. 相似文献
10.
On the Application of the Auxiliary Problem Principle 总被引:6,自引:0,他引:6
The auxiliary problem principle (APP) derives from a general theory on decomposition-coordination methods establishing a comprehensive framework for both one-level and two-level methods. In this paper, the results of the two-level methods of APP are specialized for an efficient application to some engineering problems. 相似文献