全文获取类型
收费全文 | 981篇 |
免费 | 38篇 |
国内免费 | 53篇 |
专业分类
化学 | 23篇 |
力学 | 50篇 |
综合类 | 7篇 |
数学 | 913篇 |
物理学 | 79篇 |
出版年
2023年 | 13篇 |
2022年 | 8篇 |
2021年 | 9篇 |
2020年 | 20篇 |
2019年 | 28篇 |
2018年 | 26篇 |
2017年 | 22篇 |
2016年 | 26篇 |
2015年 | 10篇 |
2014年 | 41篇 |
2013年 | 61篇 |
2012年 | 38篇 |
2011年 | 34篇 |
2010年 | 40篇 |
2009年 | 66篇 |
2008年 | 60篇 |
2007年 | 77篇 |
2006年 | 57篇 |
2005年 | 45篇 |
2004年 | 34篇 |
2003年 | 38篇 |
2002年 | 37篇 |
2001年 | 24篇 |
2000年 | 36篇 |
1999年 | 24篇 |
1998年 | 20篇 |
1997年 | 28篇 |
1996年 | 19篇 |
1995年 | 20篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 15篇 |
1984年 | 4篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 1篇 |
1971年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有1072条查询结果,搜索用时 15 毫秒
101.
经典Lucas-Fibonacci数列的上、下界公式研究 总被引:2,自引:0,他引:2
本文在研究van der Waerden数的过程中,在把van der Waerden数的问题转化成关于线性不等式组解数问题的基础上,发现局部不等式组的解数S_p与经典Lucas- Fibonacci序列有关,同时在此基础上给出了经典Lucas-Fibonacci序列S_p的一个上、下界公式. 相似文献
102.
In this paper we derive upper and lower bounds on the homogenized energy density functional corresponding to degenerated p-Poisson equations. Moreover, we give some non-trivial examples where the bounds are tight and thus can be used as good approximations of the homogenized properties. We even present some cases where the bounds coincide and also compare them with some numerical results. 相似文献
103.
Christian Jansson 《Journal of Global Optimization》2004,28(1):121-137
In this paper, we consider the computation of a rigorous lower error bound for the optimal value of convex optimization problems. A discussion of large-scale problems, degenerate problems, and quadratic programming problems is included. It is allowed that parameters, whichdefine the convex constraints and the convex objective functions, may be uncertain and may vary between given lower and upper bounds. The error bound is verified for the family of convex optimization problems which correspond to these uncertainties. It can be used to perform a rigorous sensitivity analysis in convex programming, provided the width of the uncertainties is not too large. Branch and bound algorithms can be made reliable by using such rigorous lower bounds. 相似文献
104.
A framework for positive dependence 总被引:4,自引:3,他引:1
George Kimeldorf Allan R. Sampson 《Annals of the Institute of Statistical Mathematics》1989,41(1):31-45
This paper presents, for bivariate distributions, a unified framework for studying and relating three basic concepts of positive dependence. These three concepts are positive dependence orderings, positive dependence properties and measures of positive dependence. The latter two concepts are formally defined and their properties discussed. Interrelationships among these three concepts are given, and numerous examples are presented.Supported by the National Science Foundation under Grant DMS-8301361.Supported by the Air Force Office of Scientific Research under Contract 84-0113. Reproduction in whole or part is permitted for any purpose of the United States Government. 相似文献
105.
This paper studies the local convergence properties of the control parameterization Ritz method in which the control variable is approximated over a finite-dimensional subspace. The nonlinear free-endpoint optimal control problem is considered, and error bounds are derived for both the cost functional and state-control convergence. Explicit error bounds are obtained for the particular case of approximations over spline spaces. On specializing the general results to the linear-quadratic regulator problem, global convergence results are obtained. Computational results supporting the theoretically derived error bounds are presented.This research was supported by the University Grants Committee of New Zealand. 相似文献
106.
D.R. Jensen 《Journal of multivariate analysis》1997,60(2):188-202
Distribution-free results beyond Gauss-Markov theory are found under weak assumptions regarding the errors. Symmetry, unimodality, and location-scale families are studied in estimation; nonstandard versions of Gauss–Markov results are given; and distribution-free confidence sets are tightened under symmetry and unimodality of errors. Normal-theory approximate tests are seen to exhibit monotone power in certain classes of symmetric unimodal errors. 相似文献
107.
We develop a new framework for location of competitive facilities by introducing non-constant expenditure functions into spatial interaction location models. This framework allows us to capture two key effects – market expansion and cannibalization – within the same model.We develop algorithmic approaches for finding optimal or near-optimal solutions for several models that arise from choosing a specific form of the expenditure functions. 相似文献
108.
109.
用三次B样条函数配点法,求得在矩形波冲击下具有立方非线性产品包装的冲击谱。讨论了软、硬非线性及外界激励幅值对产品损坏边界的影响。提出用损坏边界曲面来描述非线性产品包装的安全区域,并作出了相应的损坏边界曲面. 相似文献
110.
We consider theM/M/c queue, where customers transfer to a critical state when their queueing (sojourn) time exceeds a random time. Lower and upper bounds for the distribution of the number of critical jobs are derived from two modifications of the original system. The two modified systems can be efficiently solved. Numerical calculations indicate the power of the approach. 相似文献