全文获取类型
收费全文 | 7248篇 |
免费 | 1016篇 |
国内免费 | 218篇 |
专业分类
化学 | 388篇 |
晶体学 | 73篇 |
力学 | 2729篇 |
综合类 | 125篇 |
数学 | 2085篇 |
物理学 | 3082篇 |
出版年
2024年 | 6篇 |
2023年 | 64篇 |
2022年 | 126篇 |
2021年 | 175篇 |
2020年 | 200篇 |
2019年 | 148篇 |
2018年 | 151篇 |
2017年 | 212篇 |
2016年 | 208篇 |
2015年 | 201篇 |
2014年 | 294篇 |
2013年 | 451篇 |
2012年 | 377篇 |
2011年 | 440篇 |
2010年 | 338篇 |
2009年 | 391篇 |
2008年 | 433篇 |
2007年 | 460篇 |
2006年 | 486篇 |
2005年 | 421篇 |
2004年 | 324篇 |
2003年 | 346篇 |
2002年 | 315篇 |
2001年 | 291篇 |
2000年 | 237篇 |
1999年 | 220篇 |
1998年 | 181篇 |
1997年 | 159篇 |
1996年 | 113篇 |
1995年 | 113篇 |
1994年 | 102篇 |
1993年 | 79篇 |
1992年 | 73篇 |
1991年 | 56篇 |
1990年 | 52篇 |
1989年 | 24篇 |
1988年 | 19篇 |
1987年 | 28篇 |
1986年 | 24篇 |
1985年 | 24篇 |
1984年 | 19篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 13篇 |
1977年 | 10篇 |
1976年 | 17篇 |
1957年 | 4篇 |
排序方式: 共有8482条查询结果,搜索用时 46 毫秒
31.
ZHANG WenlingDepartment of Mathematics Physics National Natural Science Foundation of China Beijing China 《中国科学A辑(英文版)》2004,(6)
We use qualitative analysis and numerical simulation to study peaked traveling wave solutions of CH-γ and CH equations. General expressions of peakon and periodic cusp wave solutions are obtained. Some previous results become our special cases. 相似文献
32.
Solving large scale linear systems efficiently plays an important role in a petroleum reservoir simulator, and the key part is how to choose an effective parallel preconditioner. Properly choosing a good preconditioner has been beyond the pure algebraic field. An integrated preconditioner should include such components as physical background, characteristics of PDE mathematical model, nonlinear solving method, linear 相似文献
33.
We derive a test problem for evaluating the ability of time-steppingmethods to preserve the statistical properties of systems inmolecular dynamics. We consider a family of deterministic systemsconsisting of a finite number of particles interacting on acompact interval. The particles are given random initial conditionsand interact through instantaneous energy- and momentum-conservingcollisions. As the number of particles, the particle density,and the mean particle speed go to infinity, the trajectory ofa tracer particle is shown to converge to a stationary Gaussianstochastic process. We approximate this system by one describedby a system of ordinary differential equations and provide numericalevidence that it converges to the same stochastic process. Wesimulate the latter system with a variety of numerical integrators,including the symplectic Euler method, a fourth-order Runge-Kuttamethod, and an energyconserving step-and-project method. Weassess the methods' ability to recapture the system's limitingstatistics and observe that symplectic Euler performs significantlybetter than the others for comparable computational expense. 相似文献
34.
John A. Ekaterinaris 《国际流体数值方法杂志》2004,45(11):1187-1207
A high‐order accurate, finite‐difference method for the numerical solution of incompressible flows is presented. This method is based on the artificial compressibility formulation of the incompressible Navier–Stokes equations. Fourth‐ or sixth‐order accurate discretizations of the metric terms and the convective fluxes are obtained using compact, centred schemes. The viscous terms are also discretized using fourth‐order accurate, centred finite differences. Implicit time marching is performed for both steady‐state and time‐accurate numerical solutions. High‐order, spectral‐type, low‐pass, compact filters are used to regularize the numerical solution and remove spurious modes arising from unresolved scales, non‐linearities, and inaccuracies in the application of boundary conditions. The accuracy and efficiency of the proposed method is demonstrated for test problems. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
35.
The process of single liquid drop impact on thin liquid surface is numerically simulated with moving particle semi‐implicit method. The mathematical model involves gravity, viscosity and surface tension. The model is validated by the simulation of the experimental cases. It is found that the dynamic processes after impact are sensitive to the liquid pool depth and the initial drop velocity. In the cases that the initial drop velocity is low, the drop will be merged with the liquid pool and no big splash is seen. If the initial drop velocity is high enough, the dynamic process depends on the liquid depth. If the liquid film is very thin, a bowl‐shaped thin crown is formed immediately after the impact. The total crown subsequently expands outward and breaks into many tiny droplets. When the thickness of the liquid film increases, the direction of the liquid crown becomes normal to the surface and the crown propagates outward. It is also found that the radius of the crown is described by a square function of time: rC = [c(t ? t0)]0.5. When the liquid film is thick enough, a crown and a deep cavity inside it are formed shortly after the impact. The bottom of the cavity is initially oblate and then the base grows downward to form a sharp corner and subsequently the corner moves downward. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
36.
37.
M. A. Efendiev J. Fuhrmann S. V. Zelik 《Mathematical Methods in the Applied Sciences》2004,27(8):907-930
For the Boussinesq approximation of the equations of coupled heat and fluid flow in a porous medium we show that the corresponding system of partial differential equations possesses a global attractor. We give lower and upper bounds of the Hausdorff dimension of the attractor depending on a physical parameter of the system, namely the Rayleigh number of the flow. Numerical experiments confirm the theoretical findings and raise new questions on the structure of the solutions of the system. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
38.
晶体微观结构是晶体材料在特定物理条件下其多个能量极小平衔态在空间形成的某种微尺度的规则分布.几何非线性的连续介质力学理论可以用能量极小化原理来解释晶体微观结构的形成,并用Young测度来刻画平衡态各变体在空间的概率分布.定性的理解与定量地分析和计算晶体材料的微观结构对于发展和改进高级晶体功能材料,如形状记忆合金、铁电体、磁至伸缩材料等,有重要的意义.本文回顾了近年来晶体微观结构数值计算方面的最新进展.介绍了计算晶体微观结构的几种数值方法及有关的数值分析结果。 相似文献
39.
An efficient way of obtaining travelling waves in a periodic fluid system is described and tested. We search for steady states in a reference frame travelling at the wave phase velocity using a first‐order pseudospectral semi‐implicit time scheme adapted to carry out the Newton's iterations. The method is compared to a standard Newton–Raphson solver and is shown to be highly efficient in performing this task, even when high‐resolution grids are used. This method is well suited to three‐dimensional calculations in cylindrical or spherical geometries. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
40.