全文获取类型
收费全文 | 26161篇 |
免费 | 2149篇 |
国内免费 | 1397篇 |
专业分类
化学 | 1904篇 |
晶体学 | 34篇 |
力学 | 2861篇 |
综合类 | 220篇 |
数学 | 19974篇 |
物理学 | 4714篇 |
出版年
2024年 | 37篇 |
2023年 | 246篇 |
2022年 | 223篇 |
2021年 | 382篇 |
2020年 | 692篇 |
2019年 | 727篇 |
2018年 | 680篇 |
2017年 | 684篇 |
2016年 | 718篇 |
2015年 | 625篇 |
2014年 | 1169篇 |
2013年 | 2734篇 |
2012年 | 1145篇 |
2011年 | 1480篇 |
2010年 | 1287篇 |
2009年 | 1705篇 |
2008年 | 1654篇 |
2007年 | 1673篇 |
2006年 | 1454篇 |
2005年 | 1114篇 |
2004年 | 1043篇 |
2003年 | 987篇 |
2002年 | 979篇 |
2001年 | 773篇 |
2000年 | 793篇 |
1999年 | 716篇 |
1998年 | 605篇 |
1997年 | 560篇 |
1996年 | 383篇 |
1995年 | 302篇 |
1994年 | 281篇 |
1993年 | 211篇 |
1992年 | 190篇 |
1991年 | 145篇 |
1990年 | 139篇 |
1989年 | 95篇 |
1988年 | 81篇 |
1987年 | 74篇 |
1986年 | 67篇 |
1985年 | 94篇 |
1984年 | 131篇 |
1983年 | 61篇 |
1982年 | 95篇 |
1981年 | 96篇 |
1980年 | 87篇 |
1979年 | 75篇 |
1978年 | 69篇 |
1977年 | 51篇 |
1976年 | 41篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
21.
Summary This paper is concerned with the problem of developing numerical integration algorithms for differential equations that, when
viewed as equations in some Euclidean space, naturally evolve on some embedded submanifold. It is desired to construct algorithms
whose iterates also evolve on the same manifold. These algorithms can therefore be viewed as integrating ordinary differential
equations on manifolds. The basic method “decouples” the computation of flows on the submanifold from the numerical integration
process. It is shown that two classes of single-step and multistep algorithms can be posed and analyzed theoretically, using
the concept of “freezing” the coefficients of differential operators obtained from the defining vector field. Explicit third-order
algorithms are derived, with additional equations augmenting those of their classical counterparts, obtained from “obstructions”
defined by nonvanishing Lie brackets. 相似文献
22.
In circuit-switched networks call streams are characterized by their mean and peakedness (two-moment method). The GI/M/C/0 system is used to model a single link, where the GI-stream is determined by fitting moments appropriately. For the moments of the overflow traffic of a GI/M/C/0 system there are efficient numerical algorithms available. However, for the moments of the freed carried traffic, defined as the moments of a virtual link of infinite capacity to which the process of calls accepted by the link (carried arrival process) is virtually directed and where the virtual calls get fresh exponential i.i.d. holding times, only complex numerical algorithms are available. This is the reason why the concept of the freed carried traffic is not used. The main result of this paper is a numerically stable and efficient algorithm for computing the moments of freed carried traffic, in particular an explicit formula for its peakedness. This result offers a unified handling of both overflow and carried traffics in networks. Furthermore, some refined characteristics for the overflow and freed carried streams are derived. 相似文献
23.
24.
Lin Surong 《Annals of Differential Equations》2006,22(4):517-523
The singularly perturbed boundary value problem for nonlinear higher order ordinary differential equation involving two small parameters has been considered. Under appropriate assumptions, for the three cases:ε/μ2→0(μ→0),μ2/ε→0 (ε→0) andε=μ2, the uniformly valid asymptotic solution is obtained by using the expansion method of two small parameters and the theory of differential inequality. 相似文献
25.
Abstract
In this note, we consider a Frémond model of shape memory alloys. Let us imagine a piece of a shape memory alloy which is
fixed on one part of its boundary, and assume that forcing terms, e.g., heat sources and external stress on the remaining
part of its boundary, converge to some time-independent functions, in appropriate senses, as time goes to infinity. Under
the above assumption, we shall discuss the asymptotic stability for the dynamical system from the viewpoint of the global
attractor. More precisely, we generalize the paper [12] dealing with the one-dimensional case. First, we show the existence
of the global attractor for the limiting autonomous dynamical system; then we characterize the asymptotic stability for the
non-autonomous case by the limiting global attractor.
* Project supported by the MIUR-COFIN 2004 research program on “Mathematical Modelling and Analysis of Free Boundary Problems”. 相似文献
26.
Albo Carlos Cavalheiro 《Applications of Mathematics》2006,51(6):619-628
In the paper we study the equation L
u
= f, where L is a degenerate elliptic operator, with Neumann boundary condition in a bounded open set μ. We prove existence and uniqueness
of solutions in the space H(μ) for the Neumann problem. 相似文献
27.
Wei Gengping~ Shen Jianhua~ 《高校应用数学学报(英文版)》2006,21(3):320-326
This paper studies the nonautonomous nonlinear system of difference equationsΔx(n)=A(n)x(n)+f(n,x(n)),n∈Z,(*) where x(n)∈R~N,A(n)=(a_(ij)(n))N×N is an N×N matrix,with a-(ij)∈C(R,R) for i,j= 1,2,3,...,N,and f=(f_1,f_2,...,f_N)~T∈C(R×R~N,R~N),satisfying A(t+ω)=A(t),f(t+ω,z)=f(t,z) for any t∈R,(t,z)∈R×R~N andωis a positive integer.Sufficient conditions for the existence ofω-periodic solutions to equations (*) are obtained. 相似文献
28.
29.
Volker Elling. 《Mathematics of Computation》2006,75(256):1721-1733
A particular case of initial data for the two-dimensional Euler equations is studied numerically. The results show that the Godunov method does not always converge to the physical solution, at least not on feasible grids. Moreover, they suggest that entropy solutions (in the weak entropy inequality sense) are not well posed.
30.