全文获取类型
收费全文 | 12684篇 |
免费 | 2126篇 |
国内免费 | 889篇 |
专业分类
化学 | 1840篇 |
晶体学 | 167篇 |
力学 | 3156篇 |
综合类 | 167篇 |
数学 | 5495篇 |
物理学 | 4874篇 |
出版年
2024年 | 31篇 |
2023年 | 133篇 |
2022年 | 247篇 |
2021年 | 236篇 |
2020年 | 328篇 |
2019年 | 280篇 |
2018年 | 275篇 |
2017年 | 409篇 |
2016年 | 433篇 |
2015年 | 362篇 |
2014年 | 560篇 |
2013年 | 909篇 |
2012年 | 643篇 |
2011年 | 642篇 |
2010年 | 596篇 |
2009年 | 639篇 |
2008年 | 715篇 |
2007年 | 820篇 |
2006年 | 764篇 |
2005年 | 765篇 |
2004年 | 667篇 |
2003年 | 688篇 |
2002年 | 607篇 |
2001年 | 519篇 |
2000年 | 514篇 |
1999年 | 459篇 |
1998年 | 354篇 |
1997年 | 335篇 |
1996年 | 238篇 |
1995年 | 215篇 |
1994年 | 157篇 |
1993年 | 166篇 |
1992年 | 126篇 |
1991年 | 114篇 |
1990年 | 93篇 |
1989年 | 57篇 |
1988年 | 63篇 |
1987年 | 58篇 |
1986年 | 49篇 |
1985年 | 66篇 |
1984年 | 57篇 |
1983年 | 26篇 |
1982年 | 37篇 |
1981年 | 50篇 |
1980年 | 28篇 |
1979年 | 35篇 |
1978年 | 42篇 |
1977年 | 33篇 |
1976年 | 20篇 |
1971年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
51.
文中以强化低温固体界面间的接触导热为出发点 ,实验测定了低温环境下两种金属界面在过度加载前后的接触热导值 ,指出过度加载是一种经济有效的强化导热方法 ,对卸载过程接触热导率大于同次加载过程接触热导的“hysteresis”现象产生机理进行了分析 相似文献
52.
Jinyan Fan 《Computational Optimization and Applications》2006,34(2):215-227
In this paper, we present the new trust region method for nonlinear equations with the trust region converging to zero. The
new method preserves the global convergence of the traditional trust region methods in which the trust region radius will
be larger than a positive constant. We study the convergence rate of the new method under the local error bound condition
which is weaker than the nonsingularity. An example given by Y.X. Yuan shows that the convergence rate can not be quadratic.
Finally, some numerical results are given.
This work is supported by Chinese NSFC grants 10401023 and 10371076, Research Grants for Young Teachers of Shanghai Jiao Tong
University, and E-Institute of Computational Sciences of Shanghai Universities.
An erratum to this article is available at . 相似文献
53.
Ronald H. Nickel Igor Mikolic-Torreira Jon W. Tolle 《Computational Optimization and Applications》2006,35(1):109-126
Deployed US Navy aircraft carriers must stock a large number of spare parts to support the various types of aircraft embarked
on the ship. The sparing policy determines the spares that will be stocked on the ship to keep the embarked aircraft ready
to fly. Given a fleet of ten or more aircraft carriers and a cost of approximately 50 million dollars per carrier plus the
cost of spares maintained in warehouses in the United States, the sparing problem constitutes a significant portion of the
Navy’s resources. The objective of this work is to find a minimum-cost sparing policy that meets the readiness requirements
of the embarked aircraft. This is a very large, nonlinear, integer optimization problem. The cost function is piecewise linear
and convex while the constraint mapping is highly nonlinear. The distinguishing characteristics of this problem from an optimization
viewpoint are that a large number of decision variables are required to be integer and that the nonlinear constraint functions
are essentially “black box” functions; that is, they are very difficult (and expensive) to evaluate and their derivatives
are not available. Moreover, they are not convex. Integer programming problems with a large number of variables are difficult
to solve in general and most successful approaches to solving nonlinear integer problems have involved linear approximation
and relaxation techniques that, because of the complexity of the constraint functions, are inappropriate for attacking this
problem. We instead employ a pattern search method to each iteration of an interior point-type algorithm to solve the relaxed
version of the problem. From the solution found by the pattern search on each interior point iteration, we begin another pattern
search on the integer lattice to find a good integer solution. The best integer solution found across all interations is returned
as the optimal solution. The pattern searches are distributed across a local area network of non-dedicated, heterogeneous
computers in an office environment, thus, drastically reducing the time required to find the solution. 相似文献
54.
Successive column correction algorithms for solving sparse nonlinear systems of equations 总被引:1,自引:0,他引:1
Guangye Li 《Mathematical Programming》1989,43(1-3):187-207
This paper presents two algorithms for solving sparse nonlinear systems of equations: the CM-successive column correction algorithm and a modified CM-successive column correction algorithm. Aq-superlinear convergence theorem and anr-convergence order estimate are given for both algorithms. Some numerical results and the detailed comparisons with some previously established algorithms show that the new algorithms have some promise of being very effective in practice.This research was partially supported by contracts and grants: DOE DE-AS05-82ER1-13016, AFOSR 85-0243 at Rice University, Houston, U.S.A. and Natural Sciences and Engineering Research Council of Canada grant A-8639. 相似文献
55.
56.
在本文中,我们讨论了非线性常微分方程y"=a0|x|αy3 a1|x|βy2 α2|x|γy α3|x|δ振荡解的渐近表示.在这个方程中将α0,α,α1,β,α2,γ,α3,δ分别换成0,0,6,0,0,0,sgn(x),1就是著名的第一类Painleve方程,而将α0,α,α1,β,α2,γ,α3,δ分别换成2,0,0,0,sgn(x),1,α0,就是著名的第二类Painleve方程.当α0,α,α1,β,α2,γ,α3,δ分别换成-β/3γ,0,0,0,1/γ,1,α,0时,可用于组合KdV方程孤立子解的化简. 相似文献
57.
Howel Tong 《应用数学学报(英文版)》2002,18(2):177-184
Abstract I reflect upon the development of nonlinear time series analysis since 1990 by focusing on five majorareas of development. These areas include the interface between nonlinear time series analysis and chaos,thenonparametric/semiparametric approach,nonlinear state space modelling,financial time series and nonlinearmodelling of panels of time series. 相似文献
58.
59.
本文介绍非线性方程转化直线性方程和多元线性回归法来分析近代物理实验中塞曼效应分裂干涉圆环多处选点测量的处理过程。 相似文献
60.
The Newton filtration and d-determination of bifurcation problems related to C~0 contact equivalence
SU Dan & ZHANG Dunmu School of Mathematics Statistics Wuhan University Wuhan China 《中国科学A辑(英文版)》2006,49(5)
In this paper, from the Newton filtration's point of view, we construct the singular Riemannian metric and use the method in singular theory to study the bifurcation problems, and give the sufficient condition of d-determination of bifurcation problems with respect to C0 contact equivalence. The special cases of the main result in this paper are the results of Sun Weizhi and Zou Jiancheng. 相似文献