全文获取类型
收费全文 | 2946篇 |
免费 | 404篇 |
国内免费 | 214篇 |
专业分类
化学 | 334篇 |
晶体学 | 34篇 |
力学 | 398篇 |
综合类 | 43篇 |
数学 | 1743篇 |
物理学 | 1012篇 |
出版年
2024年 | 3篇 |
2023年 | 29篇 |
2022年 | 27篇 |
2021年 | 67篇 |
2020年 | 60篇 |
2019年 | 98篇 |
2018年 | 95篇 |
2017年 | 94篇 |
2016年 | 87篇 |
2015年 | 90篇 |
2014年 | 147篇 |
2013年 | 339篇 |
2012年 | 144篇 |
2011年 | 181篇 |
2010年 | 159篇 |
2009年 | 202篇 |
2008年 | 198篇 |
2007年 | 202篇 |
2006年 | 173篇 |
2005年 | 160篇 |
2004年 | 129篇 |
2003年 | 150篇 |
2002年 | 132篇 |
2001年 | 109篇 |
2000年 | 84篇 |
1999年 | 62篇 |
1998年 | 62篇 |
1997年 | 56篇 |
1996年 | 49篇 |
1995年 | 29篇 |
1994年 | 30篇 |
1993年 | 13篇 |
1992年 | 23篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 2篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1957年 | 2篇 |
1936年 | 1篇 |
排序方式: 共有3564条查询结果,搜索用时 46 毫秒
31.
32.
The validity of the local thermal equilibrium assumption in the transient forced convection channel flow is investigated analytically. Closed form expressions are presented for the temperatures of the fluid and solid domains and for the criterion which insures the validity of the local thermal equilibrium assumption. It is found that four dimensionless parameters control the local thermal equilibrium assumption. These parameters are the porosity , the volumetric Biot number Bi, the dimensionless channel length max and the solid to fluid total thermal capacity ratio C
R. The qualitative and quantitative aspects of the effects of these four parameters on the channel thermal equilibrium relaxation time are investigated. 相似文献
33.
Based on an analysis of second-order hydrodynamic forces induced by coupling of first-order wave potentials, second-order hydroelastic equations are established and solved in the frequency domain. The responses of a very large floating structure in multidirectional irregular waves are studied. The characteristics of the difference and sum frequency coordinates are discussed in detail; peaks can be found at the difference and sum frequencies close to the wet resonant frequencies of each mode. We present and analyze the maximum vertical displacement of different points as well as the time history of the vertical displacements of selected points. The differences of the combined (the summation of the linear and non-linear responses) and linear displacements of the selected points are calculated. Our results demonstrate that non-linear fluid forces influence the total responses of the referenced floating structure. 相似文献
34.
The paper presents a semi‐implicit algorithm for solving an unsteady fluid–structure interaction problem. The algorithm for solving numerically the fluid–structure interaction problems was obtained by combining the backward Euler scheme with a semi‐implicit treatment of the convection term for the Navier–Stokes equations and an implicit centered scheme for the structure equations. The structure is governed either by the linear elasticity or by the non‐linear St Venant–Kirchhoff elasticity models. At each time step, the position of the interface is predicted in an explicit way. Then, an optimization problem must be solved, such that the continuity of the velocity as well as the continuity of the stress hold at the interface. During the Broyden, Fletcher, Goldforb, Shano (BFGS) iterations for solving the optimization problem, the fluid mesh does not move, which reduces the computational effort. The term ‘semi‐implicit’ used for the fully algorithm means that the interface position is computed explicitly, while the displacement of the structure, velocity and the pressure of the fluid are computed implicitly. Numerical results are presented. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
35.
单层平面索网幕墙结构的风振响应分析及实用抗风设计方法 总被引:2,自引:0,他引:2
单层平面索网玻璃幕墙结构是广泛应用于大型公共建筑中的一种新型结构形式,由于其具有柔性大、质量轻、阻尼小、自振频率低的特点,属风敏感结构。由于单索幕墙具有较高的几何非线性,本文采用基于随机振动理论的模态叠加频域方法进行了单索幕墙结构的风振响应分析。将模态叠加频域方法的计算结果和非线性时程分析方法的精确计算结果进行了比较,证明了该方法的准确性。并且本文通过分析各阶模态对单索幕墙结构风振响应的贡献,得到脉动风荷载下结构的振动以第一阶模态为主的结论。根据该结论本文采用频域方法推导了单索幕墙结构的位移均方差和索内力均方差的实用计算公式,同时考虑单索幕墙的结构特点提出了基于结构响应的单索幕墙结构实用抗风设计方法。 相似文献
36.
37.
时域边界元法分析撞水响应 总被引:6,自引:1,他引:6
基于势流理论,考虑流场的可压缩性,首先利用积分变换导得了势流问题的一个动力学倒易定理,在此基础上,进而求得问题对应的时空边界积分方程,然后通过对边界和时间轴同时离散,建立了一组有递推形式的时间边界元方程最后结合液面条件和物体运动方程耦全求解得到了刚体的撞水响应。 相似文献
38.
The usual time domain Boundary Element Method (BEM) contains fundamentalsolutions which are convoluted with time-dependent boundary data andintegrated over the boundary surface. Here, a new approach for theevaluation of the convolution integrals, the so-called OperationalQuadrature Methods developed by Lubich, is presented. In thisformulation, the convolution integral is numerically approximated by aquadrature formula whose weights are determined using the Laplacetransform of the fundamental solution and a linear multisep method. Tostudy the behaviour of the method, the numerical convolution of afundamental solution with a unit step function is compared with theanalytical result. Then, a time domain Boundary Element formulationapplying the Operational Quadrature Methods is derived. For thisformulation only the fundamental solutions in Laplace domain arenecessary. The properties of the new formulation are studied with anumerical example. 相似文献
39.
In a previous article the authors introduced a Lagrange multiplier based fictitious domain method. Their goal in the present article is to apply a generalization of the above method to: (i) the numerical simulation of the motion of neutrally buoyant particles in a three-dimensional Poiseuille flow; (ii) study – via direct numerical simulations – the migration of neutrally buoyant balls in the tube Poiseuille flow of an incompressible Newtonian viscous fluid. Simulations made with one and several particles show that, as expected, the Segré–Silberberg effect takes place. To cite this article: T.-W. Pan, R. Glowinski, C. R. Mecanique 333 (2005). 相似文献
40.
V. T. Golovchan 《International Applied Mechanics》2006,42(1):84-89
An algorithm for solving plane boundary-value problems of elasticity for a rectangular domain is expounded. The algorithm
is based on a complex-valued representation of the general solution to the differential equations of the plane problem and
on the use of Lagrange polynomials to satisfy the boundary conditions. The algorithm can quite easily be implemented in a
computer program. This is probably the simplest way of solving boundary-value problems of this class
__________
Translated from Prikladnaya Mekhanika, Vol. 42, No. 1, pp. 97–102, January 2006. 相似文献