全文获取类型
收费全文 | 5497篇 |
免费 | 1332篇 |
国内免费 | 172篇 |
专业分类
化学 | 152篇 |
力学 | 550篇 |
综合类 | 71篇 |
数学 | 3886篇 |
物理学 | 2342篇 |
出版年
2024年 | 7篇 |
2023年 | 53篇 |
2022年 | 106篇 |
2021年 | 143篇 |
2020年 | 177篇 |
2019年 | 141篇 |
2018年 | 165篇 |
2017年 | 178篇 |
2016年 | 219篇 |
2015年 | 144篇 |
2014年 | 287篇 |
2013年 | 639篇 |
2012年 | 366篇 |
2011年 | 336篇 |
2010年 | 351篇 |
2009年 | 307篇 |
2008年 | 349篇 |
2007年 | 331篇 |
2006年 | 303篇 |
2005年 | 293篇 |
2004年 | 209篇 |
2003年 | 204篇 |
2002年 | 178篇 |
2001年 | 188篇 |
2000年 | 186篇 |
1999年 | 130篇 |
1998年 | 124篇 |
1997年 | 113篇 |
1996年 | 82篇 |
1995年 | 73篇 |
1994年 | 71篇 |
1993年 | 51篇 |
1992年 | 58篇 |
1991年 | 50篇 |
1990年 | 39篇 |
1989年 | 33篇 |
1988年 | 34篇 |
1987年 | 26篇 |
1986年 | 27篇 |
1985年 | 44篇 |
1984年 | 36篇 |
1983年 | 15篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 19篇 |
1976年 | 11篇 |
1972年 | 6篇 |
排序方式: 共有7001条查询结果,搜索用时 0 毫秒
31.
Consider a queueing system where customers arrive at a circle according to a homogeneous Poisson process. After choosing their positions on the circle, according to a uniform distribution, they wait for a single server who travels on the circle. The server's movement is modelled by a Brownian motion with drift. Whenever the server encounters a customer, he stops and serves this customer. The service times are independent, but arbitrarily distributed. The model generalizes the continuous cyclic polling system (the diffusion coefficient of the Brownian motion is zero in this case) and can be interpreted as a continuous version of a Markov polling system. Using Tweedie's lemma for positive recurrence of Markov chains with general state space, we show that the system is stable if and only if the traffic intensity is less than one. Moreover, we derive a stochastic decomposition result which leads to equilibrium equations for the stationary configuration of customers on the circle. Steady-state performance characteristics are determined, in particular the expected number of customers in the system as seen by a travelling server and at an arbitrary point in time. 相似文献
32.
The solvability of a class of forward-backward stochastic differential equations (SDEs for short) over an arbitrarily prescribed time duration is studied. The authors design a stochastic relaxed control problem, with both drift and difftusion all being controlled, so that the solvability problem is converted to a problem of finding the nodal set of the viscosity solution to a certain Hamilton-Jacobi-Bellman equation. This method overcomes the fatal difficulty encountered in the traditional contraction mapping approach to the existence theorem of such SDEs. 相似文献
33.
本文在文[4]的基础上讨论了双重时序AR(1)-MA(q)模型的相关结构,在不假定白噪声序列为正态的情况下,证明了安鸿志[2]关于模型的相关结构的猜想是正确的,具体地构造了AR(1)-MA(3)模型的相关结构,并与ARMA模型进行了初步的比较,给出了一些抛砖引玉的讨论. 相似文献
34.
We explicitly discuss scalar Langevin type of equations where the deterministic part is linear, but where the integrated noise source is a non-linear diffusion process exhibiting superdiffusive behavior. We calculate transient and stationary probabilities and study the possibility of noise induced transitions from a unimodal to a bimodal probability shape. Illustrations from finance and dynamical systems are given. 相似文献
35.
A. M. Chebotarev 《Mathematical Notes》1996,60(5):544-561
We prove that the Hudson-Parthasarathy equation corresponds, up to unitary equivalence, to the strong resolvent limit of Schrödinger Hamiltonians in Fock space and that the symmetric form of this equation corresponds to the weak limit of the Schrödinger Hamiltonians.Translated fromMatematicheskie Zametki, Vol. 60, No. 5, pp. 726–750, November, 1996. 相似文献
36.
In a general measure-theoretic context, it is proved that the action of a stochastic map on a pair of probability distributions can be characterized by the criterion of decreasing mixing distance. 相似文献
37.
A class of circuit-switching open queueing networks is discussed. The main result of the paper is that if extra message flows are not too intensive and the path distribution is mainly concentrated on the paths of (graph) distance 1 (nearest neighbour connections), then the network has a unique stationary working regime, no matter how large the configuration graph of the network is. Standard properties of this regime are established such as decay of correlation and continuity. 相似文献
38.
We consider the relaxation dynamics of two quantum levels coupled to a stochastic bath. We emphasize that even if the matrix elements of the fluctuating Hamiltonian are Gaussian, a second-order cumulant truncation is not exact. For various stochastic models, including the case of a spin-1/2 particle in a fluctuating magnetic field, we calculate 1/T
1, the population relaxation rate, and 1/T
2, the phase relaxation rate, up to fourth order in perturbation theory. We show that unlike the commonly accepted second-order result that 1/T
21/2T
1, when fourth-order terms are included, in some instances 1/T
2<1/2T
1. 相似文献
39.
In this paper, we establish the discrete approximation of continuous-state nonlinear branching processes in Lévy random environments by using tightness and convergence sequence in infinite dimensional product space via stochastic differential equations. Taking α-stable branching as an example, the conditions which are given to discretize continuous-state nonlinear branching processes in Lévy random environments are verified. © 2022 Chinese Academy of Sciences. All rights reserved. 相似文献
40.
形状记忆合金(SMA)是二十一世纪具有形状记忆效应的新型智能材料.针对具有非对称约束的SMA梁,本文构造了碰撞振动系统.在无碰撞和有碰撞两种情况下,利用随机平均法给出了近似解析结果.数值模拟作为验证解析结果的工具.结果表明,系统能量的概率响应曲线具有非光滑特性.当约束位置发生变化时,系统会出现随机P分岔和D分岔. 相似文献