全文获取类型
收费全文 | 23353篇 |
免费 | 2362篇 |
国内免费 | 1265篇 |
专业分类
化学 | 2321篇 |
晶体学 | 74篇 |
力学 | 6244篇 |
综合类 | 307篇 |
数学 | 13409篇 |
物理学 | 4625篇 |
出版年
2024年 | 22篇 |
2023年 | 259篇 |
2022年 | 375篇 |
2021年 | 573篇 |
2020年 | 605篇 |
2019年 | 554篇 |
2018年 | 648篇 |
2017年 | 796篇 |
2016年 | 803篇 |
2015年 | 639篇 |
2014年 | 1258篇 |
2013年 | 1644篇 |
2012年 | 1286篇 |
2011年 | 1232篇 |
2010年 | 1131篇 |
2009年 | 1299篇 |
2008年 | 1315篇 |
2007年 | 1368篇 |
2006年 | 1215篇 |
2005年 | 1191篇 |
2004年 | 989篇 |
2003年 | 929篇 |
2002年 | 839篇 |
2001年 | 776篇 |
2000年 | 710篇 |
1999年 | 613篇 |
1998年 | 611篇 |
1997年 | 517篇 |
1996年 | 392篇 |
1995年 | 359篇 |
1994年 | 300篇 |
1993年 | 226篇 |
1992年 | 232篇 |
1991年 | 201篇 |
1990年 | 167篇 |
1989年 | 113篇 |
1988年 | 96篇 |
1987年 | 90篇 |
1986年 | 80篇 |
1985年 | 94篇 |
1984年 | 84篇 |
1983年 | 43篇 |
1982年 | 45篇 |
1981年 | 38篇 |
1980年 | 31篇 |
1979年 | 42篇 |
1978年 | 27篇 |
1977年 | 35篇 |
1976年 | 23篇 |
1971年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Lisa Lorentzen 《Numerical Algorithms》1995,10(1):69-111
Over the last 20 years a large number of algorithms has been published to improve the speed and domain of convergence of continued fractions. In this survey we show that these algorithms are strongly related. Actually, they essentially boil down to two main principles.We also prove some results on asymptotic expansions of tail values of limit periodic continued fractions.Dedicated to Luigi Gatteschi on his seventieth birthdayThis research was partially supported by The Norwegian Research Council and by the HMC project ROLLS, under contract CHRX-CT93-0416. 相似文献
22.
固体力学有限元体系的结构拓扑变化理论 总被引:2,自引:1,他引:1
本文是文[1]的继续.文[1]提出了杆件系统的结构拓扑变化理论和拓扑变化法本文将这一理论和方法推进到连续体有限元体系;且在此基础上揭示出有限元体系的一个新性质,称为基本位移之梯度的正交性定理,从而给出一套设计敏度的显式表达式,可直接用于计算. 相似文献
23.
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
24.
We investigate the replica symmetry breaking (RSB) in a neighborhood of the instability point of the replica-symmetric solution in the axial quadrupolar glass model. We show that the solution with the first-stage RSB is stable against the subsequent RSB. Although there is no reflection symmetry, the first-stage RSB solution continuously bifurcates from the replica-symmetric one. This implies that our model does not belong to either of the two classes into which spin glasses are usually divided. 相似文献
25.
26.
Well-Posedness by Perturbations of Variational Problems 总被引:3,自引:0,他引:3
Lemaire B. Ould Ahmed Salem C. Revalski J. P. 《Journal of Optimization Theory and Applications》2002,115(2):345-368
In this paper, we consider the extension of the notion of well-posedness by perturbations, introduced by Zolezzi for optimization problems, to other related variational problems like inclusion problems and fixed-point problems. Then, we study the conditions under which there is equivalence of the well-posedness in the above sense between different problems. Relations with the so-called diagonal well-posedness are also given. Finally, an application to staircase iteration methods is presented. 相似文献
27.
This paper presents an adaptive memory-based method for solving the Capacitated Vehicle Routing Problem (CVRP), called BoneRoute. The CVRP deals with the problem of finding the optimal sequence of deliveries conducted by a fleet of homogeneous vehicles, based at one depot, to serve a set of customers. The computational performance of the BoneRoute was found to be very efficient, producing high quality solutions over two sets of well known case studies examined. 相似文献
28.
利用量子力学中的密度矩阵算符理论导出了P schl-Teller势阱中的线性与三阶非线性光学折射率的解析表达式。P schl-Teller势阱中有两个可调参数κ和λ,势阱的形状及其非对称性会随势阱参数的取值不同而明显不同,从而其线性与非线性光学折射率变化的大小也会随势阱参数和入射光强的变化而呈规律性的变化。文章以典型的GaAs/AlGaAs势阱为例作了数值计算,数值计算结果表明,势阱的形状和入射光强对光学折射率有着重要的影响。 相似文献
29.
Based on the vectorial Rayleigh–Sommerfeld diffraction integrals, analytical expressions for the transversal and axial field distribution of plane waves propagating through a thin lens followed by a small circular aperture are derived and used to study the focusing and diffraction properties of plane waves. Some special cases of our general result are discussed, and illustrative numerical calculation results are given. It is found that the vectorial nonparaxial approach should be applied if the aperture dimension is comparable with the wavelength or the focusing is strong. 相似文献
30.
In this paper, we will propose algorithms for calculating a minimal ellipsoid circumscribing a polytope defined by a system
of linear inequalities. If we know all vertices of the polytope and its cardinality is not very large, we can solve the problem
in an efficient manner by a number of existent algorithms. However, when the polytope is defined by linear inequalities, these
algorithms may not work since the cardinality of vertices may be huge. Based on a fact that vertices determining an ellipsoid
are only a fraction of these vertices, we propose algorithms which iteratively calculate an ellipsoid which covers a subset
of vertices. Numerical experiment shows that these algorithms perform well for polytopes of dimension up to seven. 相似文献