全文获取类型
收费全文 | 28709篇 |
免费 | 2681篇 |
国内免费 | 1638篇 |
专业分类
化学 | 2223篇 |
晶体学 | 39篇 |
力学 | 3264篇 |
综合类 | 359篇 |
数学 | 21012篇 |
物理学 | 6131篇 |
出版年
2024年 | 69篇 |
2023年 | 278篇 |
2022年 | 326篇 |
2021年 | 466篇 |
2020年 | 757篇 |
2019年 | 779篇 |
2018年 | 732篇 |
2017年 | 802篇 |
2016年 | 832篇 |
2015年 | 694篇 |
2014年 | 1186篇 |
2013年 | 2713篇 |
2012年 | 1219篇 |
2011年 | 1527篇 |
2010年 | 1284篇 |
2009年 | 1735篇 |
2008年 | 1723篇 |
2007年 | 1759篇 |
2006年 | 1606篇 |
2005年 | 1296篇 |
2004年 | 1199篇 |
2003年 | 1183篇 |
2002年 | 1182篇 |
2001年 | 957篇 |
2000年 | 1000篇 |
1999年 | 866篇 |
1998年 | 735篇 |
1997年 | 653篇 |
1996年 | 495篇 |
1995年 | 334篇 |
1994年 | 341篇 |
1993年 | 241篇 |
1992年 | 240篇 |
1991年 | 199篇 |
1990年 | 171篇 |
1989年 | 130篇 |
1988年 | 120篇 |
1987年 | 97篇 |
1986年 | 85篇 |
1985年 | 122篇 |
1984年 | 169篇 |
1983年 | 81篇 |
1982年 | 105篇 |
1981年 | 116篇 |
1980年 | 93篇 |
1979年 | 83篇 |
1978年 | 77篇 |
1977年 | 51篇 |
1976年 | 48篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Jong Uhn Kim 《Transactions of the American Mathematical Society》2002,354(3):1117-1135
In this paper we discuss an initial-boundary value problem for a stochastic nonlinear equation arising in one-dimensional viscoelasticity. We propose to use a new direct method to obtain a solution. This method is expected to be applicable to a broad class of nonlinear stochastic partial differential equations.
12.
13.
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.
14.
A simple scheme is developed for treatment of vertical bed topography in shallow water flows. The effect of the vertical step on flows is modelled with the shallow water equations including local energy loss terms. The bed elevation is denoted with zb‐ for the left and zb+ for the right values at each grid point, hence exactly representing a discontinuity in the bed topography. The surface gradient method (SGM) is generalized to reconstruct water depths at cell interfaces involving a vertical step so that the fluxes at the cell interfaces can accurately be calculated with a Riemann solver. The scheme is verified by predicting a surge crossing a step, a tidal flow over a step and dam‐break flows on wet/dry beds. The results have shown good agreements compared with analytical solutions and available experimental data. The scheme is efficient, robust, and may be used for practical flow calculations. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
15.
We analyze diffusion from a periodic array of hemispherical droplets through a membrane. We find that the multiple sources do not interact strongly, even when the droplets are closely spaced, so that the flux through the membrane appears nearly additive. 相似文献
16.
A. V. Bobylev 《Journal of statistical physics》2006,124(2-4):371-399
It is well-known that the classical Chapman-Enskog procedure does not work at the level of Burnett equations (the next step after the Navier-Stokes equations). Roughly speaking, the reason is that the solutions of higher equations of hydrodynamics (Burnett's, etc.) become unstable with respect to short-wave perturbations. This problem was recently attacked by several authors who proposed different ways to deal with it. We present in this paper one of possible alternatives. First we deduce a criterion for hyperbolicity of Burnett equations for the general molecular model and show that this criterion is not fulfilled in most typical cases. Then we discuss in more detail the problem of truncation of the Chapman-Enskog expansion and show that the way of truncation is not unique. The general idea of changes of coordinates (based on analogy with the theory of dynamical systems) leads finally to nonlinear Hyperbolic Burnett Equations (HBEs) without using any information beyond the classical Burnett equations. It is proved that HBEs satisfy the linearized H-theorem. The linear version of the problem is studied in more detail, the complete Chapman-Enskog expansion is given for the linear case. A simplified proof of the Slemrod identity for Burnett coefficients is also given. 相似文献
17.
18.
给出2005年全国部分高校研究生数学建模竞赛D题的研究背景,对参赛论文作了简要评注,并提供了一种参考解答. 相似文献
19.
We obtain upper bounds for the tail distribution of the first nonnegative sum of a random walk and for the moments of the overshoot over an arbitrary nonnegative level if the expectation of jumps is positive and close to zero. In addition, we find an estimate for the expectation of the first ladder epoch. 相似文献
20.
Summary Considered here are model equations for weakly nonlinear and dispersive long waves, which feature general forms of dispersion and pure power nonlinearity. Two variants of such equations are introduced, one of Korteweg-de Vries type and one of regularized long-wave type. It is proven that solutions of the pure initial-value problem for these two types of model equations are the same, to within the order of accuracy attributable to either, on the long time scale during which nonlinear and dispersive effects may accumulate to make an order-one relative difference to the wave profiles.This research was supported in part by the National Science Foundation. A considerable portion of the project was completed while the first author was resident at the Institute for Mathematics and Its Applications, University of Minnesota. 相似文献