全文获取类型
收费全文 | 5578篇 |
免费 | 651篇 |
国内免费 | 500篇 |
专业分类
化学 | 134篇 |
晶体学 | 2篇 |
力学 | 898篇 |
综合类 | 128篇 |
数学 | 4446篇 |
物理学 | 1121篇 |
出版年
2024年 | 7篇 |
2023年 | 67篇 |
2022年 | 60篇 |
2021年 | 98篇 |
2020年 | 120篇 |
2019年 | 157篇 |
2018年 | 161篇 |
2017年 | 158篇 |
2016年 | 186篇 |
2015年 | 125篇 |
2014年 | 210篇 |
2013年 | 482篇 |
2012年 | 228篇 |
2011年 | 247篇 |
2010年 | 255篇 |
2009年 | 304篇 |
2008年 | 360篇 |
2007年 | 403篇 |
2006年 | 365篇 |
2005年 | 302篇 |
2004年 | 268篇 |
2003年 | 294篇 |
2002年 | 272篇 |
2001年 | 203篇 |
2000年 | 200篇 |
1999年 | 189篇 |
1998年 | 176篇 |
1997年 | 176篇 |
1996年 | 108篇 |
1995年 | 96篇 |
1994年 | 58篇 |
1993年 | 55篇 |
1992年 | 50篇 |
1991年 | 47篇 |
1990年 | 35篇 |
1989年 | 25篇 |
1988年 | 27篇 |
1987年 | 28篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 14篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 14篇 |
1977年 | 4篇 |
1976年 | 10篇 |
1975年 | 2篇 |
排序方式: 共有6729条查询结果,搜索用时 18 毫秒
91.
本文用另一方法证明了非对称矩阵的奇异值是处处强半光滑的,并利用这一性质给出求解逆奇异值问题的相对广义牛顿法,该方法具有Q-二阶收敛速度. 相似文献
92.
含余割核奇异积分修改的反演问题 总被引:1,自引:0,他引:1
针对含余害核奇异积分反演问题在指κ<0时一般无解的情况,本文提出并求解两种修改的反演问题,而后一种修改反演问题的提法与此前类似问题颇不相同,由于运用了推广的留数定理和Bertrand型换序公式使本问题及类似问题解法得以简化。 相似文献
93.
94.
T. Linss 《BIT Numerical Mathematics》2007,47(2):379-391
A non-monotone FEM discretization of a singularly perturbed one-dimensional reaction-diffusion problem whose solution exhibits
strong layers is considered. The method is shown to be maximum-norm stable although it is not inverse monotone. Both a priori
and a posteriori error bounds in the maximum norm are derived. The a priori result can be used to deduce uniform convergence
of various layer-adapted meshes proposed in the literature. Numerical experiments complement the theoretical results.
AMS subject classification (2000) 65L10, 65L50, 65L60 相似文献
95.
为了求解各向异性接合材料界面端部奇异性应力场,建立了一种新型杂交元模型.该模型的独特之处在于:基于有限元特征法得到的奇异性场数值特征解建立了一种新型界面端奇异单元.通过算例证明,新型杂交元模型能够利用较少的单元数获得较为精确的数值结果.当前模型应用范围广泛,能够用于复杂结构的界面端部场求解. 相似文献
96.
Consider discrete storage processes that are modulated by environmental processes. Environmental processes cause interruptions in the input and/or output processes of the discrete storage processes. Due to the difficulties encountered in the exact analysis of such discrete storage systems, often Poisson flow and/or fluid flow models with the same modulating environmental processes are proposed as approximations for these systems. The analysis of Poisson flow and fluid flow models is much easier than that of the discrete storage processes. In this paper we give sufficient conditions under which the content of the discrete storage processes can be bounded by the Poisson flow and the fluid flow models. For example, we show that Poisson flow models and the fluid flow models developed by Kosten (and by Anick, Mitra and Sondhi) can be used to bound the performance of infinite (finite) source packetized voice/data communication systems. We also show that a Poisson flow model and the fluid flow model developed by Mitra can be used to bound the buffer content of a two stage automatic transfer line. The potential use of the bounding techniques presented in this paper, of course, transcends well beyond these examples.Supported in part by NSF grant DMS-9308149. 相似文献
97.
Klaus Ziegler 《Journal of multivariate analysis》1997,62(2):233-272
Functional central limit theorems for triangular arrays of rowwise independent stochastic processes are established by a method replacing tail probabilities by expectations throughout. The main tool is a maximal inequality based on a preliminary version proved by P. Gaenssler and Th. Schlumprecht. Its essential refinement used here is achieved by an additional inequality due to M. Ledoux and M. Talagrand. The entropy condition emerging in our theorems was introduced by K. S. Alexander, whose functional central limit theorem for so-calledmeasure-like processeswill be also regained. Applications concern, in particular, so-calledrandom measure processeswhich include function-indexed empirical processes and partial-sum processes (with random or fixed locations). In this context, we obtain generalizations of results due to K. S. Alexander, M. A. Arcones, P. Gaenssler, and K. Ziegler. Further examples include nonparametric regression and intensity estimation for spatial Poisson processes. 相似文献
98.
In this note, we characterize the regular probability measures satisfying the Choquet-Deny convolution equation =* on Abelian topological semigroups for a given probability measure . 相似文献
99.
In this paper, we identify a new class of stochastic linearconvex optimal control problems, whose solution can be obtained by solving appropriate equivalent deterministic optimal control problems. The term linear-convex is meant to imply that the dynamics is linear and the cost function is convex in the state variables, linear in the control variables, and separable. Moreover, some of the coefficients in the dynamics are allowed to be random and the expectations of the control variables are allowed to be constrained. For any stochastic linear-convex problem, the equivalent deterministic problem is obtained. Furthermore, it is shown that the optimal feedback policy of the stochastic problem is affine in its current state, where the affine transformation depends explicitly on the optimal solution of the equivalent deterministic problem in a simple way. The result is illustrated by its application to a simple stochastic inventory control problem.This research was supported in part by NSERC Grant A4617, by SSHRC Grant 410-83-0888, and by an INRIA Post-Doctoral Fellowship. 相似文献
100.
Let (
t
)
t0 be a -semistable convolution semigroup of probability measures on a Lie groupG whose idempotent
0 is the Haar measure on some compact subgroupK. Then all the measures
1
are supported by theK-contraction groupC
K() of the topological automorphism ofG. We prove here the structure theoremC
K()=C()K, whereC() is the contraction group of . Then it turns out that it is sufficient to study semistable convolution semigroups on simply connected nilpotent Lie groups that have Lie algebras with a positive graduation. 相似文献