全文获取类型
收费全文 | 17742篇 |
免费 | 478篇 |
国内免费 | 286篇 |
专业分类
化学 | 6957篇 |
晶体学 | 391篇 |
力学 | 1072篇 |
综合类 | 46篇 |
数学 | 1637篇 |
物理学 | 8403篇 |
出版年
2023年 | 98篇 |
2022年 | 250篇 |
2021年 | 216篇 |
2020年 | 143篇 |
2019年 | 185篇 |
2018年 | 272篇 |
2017年 | 217篇 |
2016年 | 358篇 |
2015年 | 265篇 |
2014年 | 416篇 |
2013年 | 800篇 |
2012年 | 1020篇 |
2011年 | 1279篇 |
2010年 | 919篇 |
2009年 | 914篇 |
2008年 | 1018篇 |
2007年 | 1000篇 |
2006年 | 1027篇 |
2005年 | 849篇 |
2004年 | 746篇 |
2003年 | 582篇 |
2002年 | 546篇 |
2001年 | 977篇 |
2000年 | 656篇 |
1999年 | 551篇 |
1998年 | 378篇 |
1997年 | 383篇 |
1996年 | 294篇 |
1995年 | 252篇 |
1994年 | 232篇 |
1993年 | 184篇 |
1992年 | 194篇 |
1991年 | 172篇 |
1990年 | 178篇 |
1989年 | 137篇 |
1988年 | 107篇 |
1987年 | 95篇 |
1986年 | 90篇 |
1985年 | 85篇 |
1984年 | 60篇 |
1983年 | 40篇 |
1982年 | 29篇 |
1981年 | 30篇 |
1979年 | 20篇 |
1978年 | 21篇 |
1977年 | 20篇 |
1976年 | 28篇 |
1975年 | 28篇 |
1974年 | 23篇 |
1973年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
61. IntroductionLet P be a submanifold of an n-dimensional riemannian manifold AI. Expressions fOrthe kth integrated mean curvatures, M^P(t), (i. e. the integral of tho kth mcan curvature,k = 0, 1,' l n -- l), of a tubular hypersurface P of radius t about P, in terms of theRiemann curvature tensor of P. are calculated when AI is Euclidean or a rank one symmetricspace[5'13"1. Moreover, when P is a closed convex hypersurface of thc n-dimensional spaceof constant curvature A', Santal6 has… 相似文献
942.
In this article we have studied the nonlinear interaction between ellipticity and dissipation in a set of model equations (1.1) and established the relation between this interaction and chaos. In addition to theoretical investigations, extensive numerical simulations with these equations have been made, and different routes to chaos have been found. The numerical studies have revealed the chaotic nature of the solutions. 相似文献
943.
Global and superlinear convergence of the smoothing Newton method and its application to general box constrained variational inequalities 总被引:23,自引:0,他引:23
The smoothing Newton method for solving a system of nonsmooth equations , which may arise from the nonlinear complementarity problem, the variational inequality problem or other problems, can be regarded as a variant of the smoothing method. At the th step, the nonsmooth function is approximated by a smooth function , and the derivative of at is used as the Newton iterative matrix. The merits of smoothing methods and smoothing Newton methods are global convergence and convenience in handling. In this paper, we show that the smoothing Newton method is also superlinearly convergent if is semismooth at the solution and satisfies a Jacobian consistency property. We show that most common smooth functions, such as the Gabriel-Moré function, have this property. As an application, we show that for box constrained variational inequalities if the involved function is -uniform, the iteration sequence generated by the smoothing Newton method will converge to the unique solution of the problem globally and superlinearly (quadratically).
944.
随机变量序列加权和的强收敛性 总被引:12,自引:0,他引:12
本文讨论了一般随机变量序列加权和的强收敛性.作为推论,得到一类鞅差序列加权和的收敛定理和若干经典的独立随机变量序列的强大数定律;已有的若干结论是本文结果的特例. 相似文献
945.
金淦 《Annals of Differential Equations》1998,(4)
1IntroductionStabilityintermsoftwomeasures,thisconceptenableustounifyava-rietyofstabilityconceptsandtoofferageneralandunifiedframeworkforinvestigationofstabilitytheory.AndtheoriginalLiapunovtheoremshavebeenextended,generalizedandweakenedinvariousaspects[3… 相似文献
946.
Optimal Control of a Stochastic Assembly Production Line 总被引:1,自引:0,他引:1
The system under consideration comprises n workstations in parallel and one assembly workstation. The workstations are either reliable or unreliable and the product demand is random. The n different type parts are processed first in the parallel workstations and then are joined in the assembly workstation. By minimizing the expected discounted cost, it is shown that the optimal control policy is of the bang–bang type and can be described by a set of switching manifolds. The structural properties of the optimal policy, such as monotonicity and asymptotic behavior, are investigated. These structural properties are very useful to find the optimal policy in large-size systems. Three numerical examples are given to demonstrate the results. 相似文献
947.
Meixner polynomials m
n
(x;β,c) form a postive-definite orthogonal system on the positive real line x > 0 with respect to a distribution step function whose jumps are Unlike classical orthogonal polynomials, they do not satisfy a second-order linear differential equation. In this paper,
we derive two infinite asymptotic expansions for m
n
(nα;β,c) as . One holds uniformly for , and the other holds uniformly for , where a and b are two small positive quantities. Both expansions involve the parabolic cylinder function and its derivative. Our results
include all five asymptotic formulas recently given by W. M. Y. Goh as special cases.
April 16, 1996. Date revised: October 30, 1996. 相似文献
948.
本文讨论半马氏环境连续时间马氏决策过程中的平均准则.首先讨论了半马氏报酬过程中的逼近问题,进而讨论平均目标函数逼近问题。 相似文献
949.
950.
本文通过张量在T-乘积下的T-Moore-Penrose逆、T-Drazin逆以及T-corenilpotent分解定理,引入三阶F-square(正面方的)张量在T-乘积下的T-DMP逆与TCMP逆的定义,同时给出它们的若干刻画和性质.最后将三阶张量的Cayley-Hamilton定理推广到张量的T-Drazin逆与T-DMP逆上,并给出例子进行验证. 相似文献