全文获取类型
收费全文 | 29212篇 |
免费 | 3621篇 |
国内免费 | 1685篇 |
专业分类
化学 | 4893篇 |
晶体学 | 68篇 |
力学 | 4784篇 |
综合类 | 231篇 |
数学 | 14711篇 |
物理学 | 9831篇 |
出版年
2024年 | 62篇 |
2023年 | 429篇 |
2022年 | 383篇 |
2021年 | 541篇 |
2020年 | 840篇 |
2019年 | 746篇 |
2018年 | 759篇 |
2017年 | 809篇 |
2016年 | 819篇 |
2015年 | 752篇 |
2014年 | 1339篇 |
2013年 | 2555篇 |
2012年 | 1379篇 |
2011年 | 1887篇 |
2010年 | 1537篇 |
2009年 | 1940篇 |
2008年 | 1888篇 |
2007年 | 1876篇 |
2006年 | 1672篇 |
2005年 | 1475篇 |
2004年 | 1346篇 |
2003年 | 1232篇 |
2002年 | 1065篇 |
2001年 | 918篇 |
2000年 | 864篇 |
1999年 | 745篇 |
1998年 | 681篇 |
1997年 | 631篇 |
1996年 | 483篇 |
1995年 | 377篇 |
1994年 | 318篇 |
1993年 | 293篇 |
1992年 | 233篇 |
1991年 | 216篇 |
1990年 | 170篇 |
1989年 | 149篇 |
1988年 | 119篇 |
1987年 | 108篇 |
1986年 | 70篇 |
1985年 | 100篇 |
1984年 | 128篇 |
1983年 | 67篇 |
1982年 | 100篇 |
1981年 | 84篇 |
1980年 | 69篇 |
1979年 | 68篇 |
1978年 | 60篇 |
1977年 | 39篇 |
1976年 | 30篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
21.
22.
The zero dissipation limit of the one-dimensional non-isentropic micropolar equations is studied in this paper. If the given rarefaction wave which connects to vacuum at one side, a sequence of solution to the micropolar equations can be constructed which converge to the above rarefaction wave with vacuum as the viscosity and the heat conduction coefficient tend to zero. Moreover, the uniform convergence rate is obtained. The key point in our analysis is how to control the degeneracies in the vacuum region in the zero dissipation limit process. 相似文献
23.
24.
《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2020,37(2):417-456
We study the energy-critical nonlinear wave equation in the presence of an inverse-square potential in dimensions three and four. In the defocussing case, we prove that arbitrary initial data in the energy space lead to global solutions that scatter. In the focusing case, we prove scattering below the ground state threshold. 相似文献
25.
In this paper, we consider a viscoelastic wave equation of variable coefficients in the presence of past history with nonlinear damping and delay in the internal feedback and dynamic boundary conditions. Under suitable assumptions, we establish an explicit and general decay rate result without imposing restrictive assumption on the behavior of the relaxation function at infinity by Riemannian geometry method and Lyapunov functional method. 相似文献
26.
27.
28.
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
29.
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
30.
Second-order random wave solutions for interfacial internal waves in N-layer density-stratified fluid
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper studies the random internal wave equations describing the density interface displacements and the velocity potentials of N-layer stratified fluid contained between two rigid walls at the top and bottom. The density interface displacements and the velocity potentials were solved to the second-order by an expansion approach used by Longuet-Higgins (1963) and Dean (1979) in the study of random surface waves and by Song (2004) in the study of second- order random wave solutions for internal waves in a two-layer fluid. The obtained results indicate that the first-order solutions are a linear superposition of many wave components with different amplitudes, wave numbers and frequencies, and that the amplitudes of first-order wave components with the same wave numbers and frequencies between the adjacent density interfaces are modulated by each other. They also show that the second-order solutions consist of two parts: the first one is the first-order solutions, and the second one is the solutions of the second-order asymptotic equations, which describe the second-order nonlinear modification and the second-order wave-wave interactions not only among the wave components on same density interfaces but also among the wave components between the adjacent density interfaces. Both the first-order and second-order solutions depend on the density and depth of each layer. It is also deduced that the results of the present work include those derived by Song (2004) for second-order random wave solutions for internal waves in a two-layer fluid as a particular case. 相似文献