全文获取类型
收费全文 | 16369篇 |
免费 | 1301篇 |
国内免费 | 781篇 |
专业分类
化学 | 305篇 |
晶体学 | 8篇 |
力学 | 2254篇 |
综合类 | 107篇 |
数学 | 12817篇 |
物理学 | 2960篇 |
出版年
2024年 | 37篇 |
2023年 | 176篇 |
2022年 | 135篇 |
2021年 | 240篇 |
2020年 | 454篇 |
2019年 | 450篇 |
2018年 | 452篇 |
2017年 | 440篇 |
2016年 | 425篇 |
2015年 | 396篇 |
2014年 | 696篇 |
2013年 | 1795篇 |
2012年 | 628篇 |
2011年 | 944篇 |
2010年 | 768篇 |
2009年 | 1066篇 |
2008年 | 1036篇 |
2007年 | 957篇 |
2006年 | 883篇 |
2005年 | 675篇 |
2004年 | 618篇 |
2003年 | 611篇 |
2002年 | 606篇 |
2001年 | 484篇 |
2000年 | 491篇 |
1999年 | 442篇 |
1998年 | 371篇 |
1997年 | 351篇 |
1996年 | 262篇 |
1995年 | 179篇 |
1994年 | 168篇 |
1993年 | 139篇 |
1992年 | 103篇 |
1991年 | 91篇 |
1990年 | 79篇 |
1989年 | 60篇 |
1988年 | 46篇 |
1987年 | 48篇 |
1986年 | 38篇 |
1985年 | 64篇 |
1984年 | 100篇 |
1983年 | 50篇 |
1982年 | 64篇 |
1981年 | 64篇 |
1980年 | 58篇 |
1979年 | 56篇 |
1978年 | 54篇 |
1977年 | 33篇 |
1976年 | 27篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Erosion and sediments transport processes have a great impact on industrial structures and on water quality. Despite its limitations, the Saint‐Venant‐Exner system is still (and for sure for some years) widely used in industrial codes to model the bedload sediment transport. In practice, its numerical resolution is mostly handled by a splitting technique that allows a weak coupling between hydraulic and morphodynamic distinct softwares but may suffer from important stability issues. In recent works, many authors proposed alternative methods based on a strong coupling that cure this problem but are not so trivial to implement in an industrial context. In this work, we then pursue 2 objectives. First, we propose a very simple scheme based on an approximate Riemann solver, respecting the strong coupling framework, and we demonstrate its stability and accuracy through a number of numerical test cases. However, second, we reinterpret our scheme as a splitting technique and we extend the purpose to propose what should be the minimal coupling that ensures the stability of the global numerical process in industrial codes, at least, when dealing with collocated finite volume method. The resulting splitting method is, up to our knowledge, the only one for which stability properties are fully demonstrated. 相似文献
2.
3.
4.
In this paper, we propose a sufficient and necessary condition for the boundedness of all the solutions for the equation with the critical situation that on g and p, where , is periodic and is bounded. 相似文献
5.
6.
7.
We discuss an error estimation procedure for the global error of collocation schemes applied to solve singular boundary value problems with a singularity of the first kind. This a posteriori estimate of the global error was proposed by Stetter in 1978 and is based on the idea of Defect Correction, originally due to Zadunaisky. Here, we present a new, carefully designed modification of this error estimate which not only results in less computational work but also appears to perform satisfactorily for singular problems. We give a full analytical justification for the asymptotical correctness of the error estimate when it is applied to a general nonlinear regular problem. For the singular case, we are presently only able to provide computational evidence for the full convergence order, the related analysis is still work in progress. This global estimate is the basis for a grid selection routine in which the grid is modified with the aim to equidistribute the global error. This procedure yields meshes suitable for an efficient numerical solution. Most importantly, we observe that the grid is refined in a way reflecting only the behavior of the solution and remains unaffected by the unsmooth direction field close to the singular point. 相似文献
8.
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
9.
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
10.