全文获取类型
收费全文 | 12594篇 |
免费 | 1173篇 |
国内免费 | 1118篇 |
专业分类
化学 | 3077篇 |
晶体学 | 98篇 |
力学 | 764篇 |
综合类 | 298篇 |
数学 | 7012篇 |
物理学 | 3636篇 |
出版年
2024年 | 13篇 |
2023年 | 104篇 |
2022年 | 269篇 |
2021年 | 331篇 |
2020年 | 355篇 |
2019年 | 339篇 |
2018年 | 339篇 |
2017年 | 378篇 |
2016年 | 507篇 |
2015年 | 362篇 |
2014年 | 654篇 |
2013年 | 970篇 |
2012年 | 607篇 |
2011年 | 680篇 |
2010年 | 561篇 |
2009年 | 744篇 |
2008年 | 810篇 |
2007年 | 841篇 |
2006年 | 730篇 |
2005年 | 610篇 |
2004年 | 547篇 |
2003年 | 544篇 |
2002年 | 467篇 |
2001年 | 419篇 |
2000年 | 385篇 |
1999年 | 310篇 |
1998年 | 289篇 |
1997年 | 248篇 |
1996年 | 232篇 |
1995年 | 161篇 |
1994年 | 162篇 |
1993年 | 103篇 |
1992年 | 90篇 |
1991年 | 81篇 |
1990年 | 65篇 |
1989年 | 66篇 |
1988年 | 62篇 |
1987年 | 45篇 |
1986年 | 40篇 |
1985年 | 66篇 |
1984年 | 46篇 |
1983年 | 26篇 |
1982年 | 44篇 |
1981年 | 29篇 |
1980年 | 20篇 |
1979年 | 30篇 |
1978年 | 21篇 |
1977年 | 28篇 |
1976年 | 27篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Consider a regular diffusion process X with finite speed measure m. Denote the normalized speed measure by μ. We prove that the uniform law of large numbers
holds if the class
has an envelope function that is μ-integrable, or if
is bounded in L
p(μ) for some p>1. In contrast with uniform laws of large numbers for i.i.d. random variables, we do not need conditions on the ‘size’ of
the class
in terms of bracketing or covering numbers. The result is a consequence of a number of asymptotic properties of diffusion
local time that we derive. We apply our abstract results to improve consistency results for the local time estimator (LTE)
and to prove consistency for a class of simple M-estimators.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
52.
Consider a single-server queue with a Poisson arrival process and exponential processing times in which each customer independently reneges after an exponentially distributed amount of time. We establish that this system can be approximated by either a reflected Ornstein–Uhlenbeck process or a reflected affine diffusion when the arrival rate exceeds or is close to the processing rate and the reneging rate is close to 0. We further compare the quality of the steady-state distribution approximations suggested by each diffusion. 相似文献
53.
In this paper, we study the stability conditions of the MMAP[K]/G[K]/1/LCFS preemptive repeat queue. We introduce an embedded Markov chain of matrix M/G/1 type with a tree structure and identify conditions for the Markov chain to be ergodic. First, we present three conventional methods for the stability problem of the queueing system of interest. These methods are either computationally demanding or do not provide accurate information for system stability. Then we introduce a novel approach that develops two linear programs whose solutions provide sufficient conditions for stability or instability of the queueing system. The new approach is numerically efficient. The advantages and disadvantages of the methods introduced in this paper are analyzed both theoretically and numerically. 相似文献
54.
The authors establish the Hilbertian invariance principle for the empirical process of a stationary Markov process, by extending the forward-backward martingale decomposition of Lyons-Meyer-Zheng to the Hilbert space valued additive functionals associated with general non-reversible Markov processes. 相似文献
55.
The representation of additive functionals and local times for jump Markov processes are obtained,The results of uniformly functional moderate deviation and their applications to birth-death processes are also presented. 相似文献
56.
Using non-linear connection of Finsler manifold M, the existence of local coordinates which is normalized at a point x is proved, and the Laplace operator A on 1-form of M is defined by non-linear connection and its curvature tensor. After proving the maximum principle theorem of Hopf-Bochner on M, the Bochner type vanishing theorem of Killing vectors and harmonic 1-form are obtained. 相似文献
57.
A.B.El-Rayes AbdEl-MoneimA.Mohamed HamdyM.AbouGabal 《数学物理学报(B辑英文版)》2003,23(3):321-327
A target is assumed to move according to a Brownian motion on the real line. The searcher starts from the origin and moves in the two directions from the starting point.The object is to detect the target. The purpose of this paper is to find the conditions under which the expected value of the first meeting time of the searcher and the target is finite,and to show the existence of a search plan which made this expected value minimum. 相似文献
58.
Yeh Lam 《应用数学学报(英文版)》2003,19(3):405-416
Geometric process (GP) was introduced by Lam[4,5], it is defined as a stochastic process {Xn, n = 1, 2,…} for which there exists a real number a > 0, such that {an-1 Xn, n = 1,2, …} forms a renewal process (RP). In this paper, we study some limit theorems in GP. We first derive the Wald equation for GP and then obtain the limit theorems of the age, residual life and the total life at t for a GP. A general limit theorem for Sn with a > 1 is also studied. Furthermore, we make a comparison between GP and RP, including the comparison of their limit distributions of the age, residual life and the total life at t. 相似文献
59.
In this paper, we show that if is an n-dimensional subspace of L(V) such that every nonzero transformation of has rank greater than or equal to 2n−1 then is algebraically reflexive. If is an n-dimensional subspace of B(H) such that every nonzero transformation of has rank greater than or equal to 2n−1 then is hyperreflexive. We also consider how to construct some new hyperreflexive subspaces. 相似文献
60.
Howard Jacobowitz Gerardo Mendoza 《Transactions of the American Mathematical Society》2003,355(10):4201-4222
We study embeddings of complex vector bundles, especially line bundles, in the complexification of the tangent bundle of a manifold. The aim is to understand implications of properties of interest in partial differential equations.