全文获取类型
收费全文 | 57658篇 |
免费 | 8422篇 |
国内免费 | 6429篇 |
专业分类
化学 | 20858篇 |
晶体学 | 1235篇 |
力学 | 12100篇 |
综合类 | 745篇 |
数学 | 16606篇 |
物理学 | 20965篇 |
出版年
2024年 | 143篇 |
2023年 | 687篇 |
2022年 | 1380篇 |
2021年 | 1428篇 |
2020年 | 1892篇 |
2019年 | 1604篇 |
2018年 | 1621篇 |
2017年 | 2118篇 |
2016年 | 2528篇 |
2015年 | 2026篇 |
2014年 | 3147篇 |
2013年 | 4580篇 |
2012年 | 3648篇 |
2011年 | 4020篇 |
2010年 | 3379篇 |
2009年 | 3726篇 |
2008年 | 3610篇 |
2007年 | 3660篇 |
2006年 | 3359篇 |
2005年 | 3042篇 |
2004年 | 2648篇 |
2003年 | 2416篇 |
2002年 | 2054篇 |
2001年 | 1766篇 |
2000年 | 1707篇 |
1999年 | 1478篇 |
1998年 | 1392篇 |
1997年 | 1156篇 |
1996年 | 977篇 |
1995年 | 839篇 |
1994年 | 785篇 |
1993年 | 628篇 |
1992年 | 613篇 |
1991年 | 451篇 |
1990年 | 359篇 |
1989年 | 291篇 |
1988年 | 247篇 |
1987年 | 178篇 |
1986年 | 134篇 |
1985年 | 155篇 |
1984年 | 140篇 |
1983年 | 67篇 |
1982年 | 101篇 |
1981年 | 61篇 |
1980年 | 42篇 |
1979年 | 58篇 |
1978年 | 41篇 |
1977年 | 39篇 |
1976年 | 16篇 |
1957年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
1.
2.
3.
Rafael López 《Annals of Global Analysis and Geometry》1997,15(3):201-210
In this paper we study constant mean curvature compact surfaces with two Jordan curves in parallel planes as boundary and we investigate the point at which the surface inherits the symmetries of its boundary. 相似文献
4.
5.
Dean A. Carlson 《Journal of Mathematical Analysis and Applications》2002,276(2):561-588
The method of equivalent variational methods, originally due to Carathéodory for free problems in the calculus of variations is extended to investigate feedback Nash equilibria for a class of n-person differential games. Both the finite-horizon and infinite-horizon cases are considered. Examples are given to illustrate the presented results. 相似文献
6.
The excitation of eigen surface waves by tubular electron beams in cylindrical discharge devices is studied. The influence of the wave‐field azimuthal structure on the excitation efficiency and nonlinear stage of the plasmabeam instability is investigated both numerically and analytically. Analytical expressions for the saturation amplitude and excitation efficiency of the wave under study are derived. They are found to agree well with results obtained by numerical modelling of the plasma‐beam interaction presented in this paper. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
7.
P.A. Ramachandran 《Numerical Methods for Partial Differential Equations》2006,22(4):831-846
Time‐dependent differential equations can be solved using the concept of method of lines (MOL) together with the boundary element (BE) representation for the spatial linear part of the equation. The BE method alleviates the need for spatial discretization and casts the problem in an integral format. Hence errors associated with the numerical approximation of the spatial derivatives are totally eliminated. An element level local cubic approximation is used for the variable at each time step to facilitate the time marching and the nonlinear terms are represented in a semi‐implicit manner by a local linearization at each time step. The accuracy of the method has been illustrated on a number of test problems of engineering significance. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2006 相似文献
8.
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
9.
从点电荷的电势计算公式出发推导出了瓣形均匀带电面在其直径处的电势分布.进一步讨论了均匀带电半球面在其底面以及均匀带电球面内部和外部的电势分布. 相似文献
10.
A. G. Bratsos 《Numerical Algorithms》2006,43(4):295-308
A three-time level finite-difference scheme based on a fourth order in time and second order in space approximation has been
proposed for the numerical solution of the nonlinear two-dimensional sine-Gordon equation. The method, which is analysed for
local truncation error and stability, leads to the solution of a nonlinear system. To avoid solving it, a predictor–corrector
scheme using as predictor a second-order explicit scheme is proposed. The procedure of the corrector has been modified by
considering as known the already evaluated corrected values instead of the predictor ones. This modified scheme has been tested
on the line and circular ring soliton and the numerical experiments have proved that there is an improvement in the accuracy
over the standard predictor–corrector implementation.
This research was co-funded by E.U. (75%) and by the Greek Government (25%). 相似文献