全文获取类型
收费全文 | 16400篇 |
免费 | 1364篇 |
国内免费 | 785篇 |
专业分类
化学 | 312篇 |
晶体学 | 9篇 |
力学 | 2278篇 |
综合类 | 111篇 |
数学 | 12910篇 |
物理学 | 2929篇 |
出版年
2024年 | 34篇 |
2023年 | 176篇 |
2022年 | 141篇 |
2021年 | 245篇 |
2020年 | 467篇 |
2019年 | 452篇 |
2018年 | 460篇 |
2017年 | 445篇 |
2016年 | 436篇 |
2015年 | 394篇 |
2014年 | 699篇 |
2013年 | 1788篇 |
2012年 | 638篇 |
2011年 | 956篇 |
2010年 | 769篇 |
2009年 | 1071篇 |
2008年 | 1033篇 |
2007年 | 957篇 |
2006年 | 882篇 |
2005年 | 677篇 |
2004年 | 620篇 |
2003年 | 616篇 |
2002年 | 610篇 |
2001年 | 485篇 |
2000年 | 493篇 |
1999年 | 446篇 |
1998年 | 374篇 |
1997年 | 352篇 |
1996年 | 263篇 |
1995年 | 181篇 |
1994年 | 170篇 |
1993年 | 140篇 |
1992年 | 104篇 |
1991年 | 91篇 |
1990年 | 79篇 |
1989年 | 60篇 |
1988年 | 46篇 |
1987年 | 48篇 |
1986年 | 37篇 |
1985年 | 65篇 |
1984年 | 101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
51.
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
52.
研究了Banach空间中非线性混合型微分-积分方程初值问题u′=f(t,u,Tu,Su),u(0)=x0的整体解,完全没有要求f的任何增性,利用Mnch不动点定理和比较结果得到了初值问题整体解的存在性和唯一解,并且给出了一致收敛于唯一解的迭代序列,改进推广和统一了已有的许多结果. 相似文献
53.
Some new oscillation criteria are established for a second order neutral delay differential equations. These results improve oscillation results of Y.V. Rogo-vchenko for the retarded delay differential equations. The relevance of our theorems is illustrated with two carefully selected examples. 相似文献
54.
Volker John 《国际流体数值方法杂志》2004,44(7):777-788
This paper presents a numerical study of a two‐dimensional time‐dependent flow around a cylinder. Its main objective is to provide accurate reference values for the maximal drag and lift coefficient at the cylinder and for the pressure difference between the front and the back of the cylinder at the final time. In addition, the accuracy of these values obtained with different time stepping schemes and different finite element methods is studied. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
55.
对于超细长弹性杆静力学的Kirchhoff方程,用动力学的概念和方法研究其常值特解 和稳定性问题.计算了Kirchhoff方程相对固定坐标系、截面主轴坐标系以及中心线Frenet 坐标系的常值特解,进行了Kirchhoff动力学比拟,用一次近似理论分别讨论了它们的Lyapu nov稳定性,导出了若干稳定性判据,并在参数平面上绘出了稳定域.
关键词:
超细长弹性杆
Kirchhoff方程
常值特解
Lyapunov稳定性 相似文献
56.
Quan Sen JIU Department of Mathematics Capital Normal University Beijing P.R.China Cheng HE Institute of Applied Mathematics Academy of Mathematics System Sciences Chinese Academy of Sciences Beijing P.R.China 《应用数学学报(英文版)》2004,(4)
In this paper we are interested in the sufficient conditions which guarantee the regularityof solutions of 3-D ideal magnetohydrodynamic equations in the arbitrary time interval [0,T].Fivesufficient conditions are given.Our results are motivated by two main ideas:one is to control theaccumulation of vorticity alone;the other is to generalize the corresponding geometric conditions of3-D Euler equations to 3-D ideal magnetohydrodynamic equations. 相似文献
57.
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
58.
Continuous dependence on a modelling parameter is established for solutions of a problem for a complex Ginzburg–Landau equation. A homogenizing boundary condition is also used to discuss the continuous dependence results. We derive a priori estimates that indicate that solutions depend continuously on a parameter in the governing differential equation. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
59.
Parabolic Capacity and Soft Measures for Nonlinear Equations 总被引:2,自引:0,他引:2
We first introduce, using a functional approach, the notion of capacity related to the parabolic p-Laplace operator. Then we prove a decomposition theorem for measures (in space and time) that do not charge the sets of null capacity. We apply this result to prove existence and uniqueness of renormalized solutions for nonlinear parabolic initial boundary-value problems with such measures as right-hand side. 相似文献
60.
通过对非饱和土非线性本构方程和场方程的线性化,推导出了非饱和土的线性本构方程和场方程,把线性方程表示为与Biot饱和多孔介质方程相似的形式;证明了Darcy定律对非饱和土的适用性;说明了Biot饱和多孔介质方程是这些线性方程的特征。所有这些都表明用混合理论处理非饱和土本构问题的正确性。 相似文献