全文获取类型
收费全文 | 5771篇 |
免费 | 527篇 |
国内免费 | 240篇 |
专业分类
化学 | 557篇 |
晶体学 | 5篇 |
力学 | 639篇 |
综合类 | 148篇 |
数学 | 4000篇 |
物理学 | 1189篇 |
出版年
2024年 | 6篇 |
2023年 | 52篇 |
2022年 | 91篇 |
2021年 | 90篇 |
2020年 | 110篇 |
2019年 | 92篇 |
2018年 | 97篇 |
2017年 | 116篇 |
2016年 | 164篇 |
2015年 | 133篇 |
2014年 | 232篇 |
2013年 | 319篇 |
2012年 | 260篇 |
2011年 | 276篇 |
2010年 | 275篇 |
2009年 | 332篇 |
2008年 | 375篇 |
2007年 | 418篇 |
2006年 | 328篇 |
2005年 | 299篇 |
2004年 | 273篇 |
2003年 | 254篇 |
2002年 | 272篇 |
2001年 | 210篇 |
2000年 | 168篇 |
1999年 | 171篇 |
1998年 | 180篇 |
1997年 | 147篇 |
1996年 | 128篇 |
1995年 | 113篇 |
1994年 | 84篇 |
1993年 | 75篇 |
1992年 | 65篇 |
1991年 | 45篇 |
1990年 | 29篇 |
1989年 | 30篇 |
1988年 | 41篇 |
1987年 | 20篇 |
1986年 | 24篇 |
1985年 | 24篇 |
1984年 | 31篇 |
1983年 | 8篇 |
1982年 | 19篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 11篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1975年 | 2篇 |
排序方式: 共有6538条查询结果,搜索用时 31 毫秒
1.
杨晓光 《应用数学学报(英文版)》1997,13(4):337-341
1.IntroductionIntillspaperweanalyzetheconvergenceonmultiplicativeiterativealgorithmsfortheIninimizationofadiffcrentiablefunctiondefinedonthepositiveorthantofR".ThealgorithmissllggestedbyEggermolltl'],andisrelatedtotheEM[2](Expextation--Maximization)algoritllnlforPositronemissiontonlography[']andimagereconstructi..14].Wecollsidertheproblenl"linf(x)s.t.x20.Themultiplicativeiterativealgorithmshavethel'orlniforj=l,2,',n,withAhdeterminedthroughalinesearch.Whilelusem[5]establishedanelegantconv… 相似文献
2.
Jinchao Xu 《应用数学学报(英文版)》2002,18(2):185-200
Abstract Some new local and parallel finite element algorithms are proposed and analyzed in this paper foreigenvalue problems.With these algorithms, the solution of an eigenvalue problem on a fine grid is reduced tothe solution of an eigenvalue problem on a relatively coarse grid together with solutions of some linear algebraicsystems on fine grid by using some local and parallel procedure.A theoretical tool for analyzing these algorithmsis some local error estimate that is also obtained in this paper for finite element approximations of eigenvectorson general shape-regular grids. 相似文献
3.
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
4.
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
5.
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
6.
7.
曾六川 《数学物理学报(A辑)》2002,22(1):99-106
该文研究Banach空间中一类强增生型变分包含解的存在性及其具误差的Ishikawa迭代程序的收敛性问题.该文结果是几位作者早期与最近的相应结果的改进和推广. 相似文献
8.
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
9.
基于FPGA并行处理的实时图像相关速度计 总被引:3,自引:1,他引:2
研究制作了一种采用高速线阵CCD的实时相关速度计,其测量数据的输出速率可达每秒一万次。针对以往光学相关测速方法的问题进行了讨论,探讨了适合FPGA并行处理的算法,制作了高速线阵CCD摄像机及其处理装置。通过实验验证了系统的可行性和可实现性。 相似文献
10.
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