全文获取类型
收费全文 | 1010篇 |
免费 | 68篇 |
国内免费 | 35篇 |
专业分类
化学 | 49篇 |
晶体学 | 1篇 |
力学 | 656篇 |
综合类 | 8篇 |
数学 | 148篇 |
物理学 | 251篇 |
出版年
2023年 | 2篇 |
2022年 | 10篇 |
2021年 | 14篇 |
2020年 | 31篇 |
2019年 | 19篇 |
2018年 | 21篇 |
2017年 | 22篇 |
2016年 | 42篇 |
2015年 | 45篇 |
2014年 | 54篇 |
2013年 | 69篇 |
2012年 | 55篇 |
2011年 | 55篇 |
2010年 | 45篇 |
2009年 | 69篇 |
2008年 | 72篇 |
2007年 | 54篇 |
2006年 | 50篇 |
2005年 | 50篇 |
2004年 | 38篇 |
2003年 | 28篇 |
2002年 | 37篇 |
2001年 | 24篇 |
2000年 | 19篇 |
1999年 | 27篇 |
1998年 | 21篇 |
1997年 | 26篇 |
1996年 | 13篇 |
1995年 | 11篇 |
1994年 | 15篇 |
1993年 | 25篇 |
1992年 | 9篇 |
1991年 | 11篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1970年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1113条查询结果,搜索用时 15 毫秒
51.
The unsteady incompressible Navier-Stokes equations have been accurately solved for the laminar flow past a circular cylinder in the Reynolds number range 50–200. A direct elliptic solver called the SEVP is used to rapidly advance the streamfunction in time, facilitating the overall convergence to the fully periodic or quasi-steady state. A new integral-series method is developed for the far-field streamfunction condition on a finite two-dimensional computational domain. The use of fourth-order Hermitian relations for the convection terms in the conservation-form vorticity transport equation has also contributed to the good comparison of the present results with the earlier experimental data. The vortex-shedding patterns visualized by the experimentalist are numerically reproduced here in the given Reynolds number range. Discussions that may be helpful in interpreting the behaviour of the shedding frequency are presented in the main text. 相似文献
52.
J. Hoffman 《国际流体数值方法杂志》2009,59(11):1241-1258
General Galerkin (G2) is a new computational method for turbulent flow, where a stabilized Galerkin finite element method is used to compute approximate weak solutions to the Navier–Stokes equations directly, without any filtering of the equations as in a standard approach to turbulence simulation, such as large eddy simulation, and thus no Reynolds stresses are introduced, which need modelling. In this paper, G2 is used to compute the drag coefficient cD for the flow past a circular cylinder at Reynolds number Re=3900, for which the flow is turbulent. It is found that it is possible to approximate cD to an accuracy of a few percent, corresponding to the accuracy in experimental results for this problem, using less than 105 mesh points, which makes the simulations possible using a standard PC. The mesh is adaptively refined until a stopping criterion is reached with respect to the error in a chosen output of interest, which in this paper is cD. Both the stopping criterion and the mesh‐refinement strategy are based on a posteriori error estimates, in the form of a space–time integral of residuals times derivatives of the solution of a dual problem, linearized at the approximate solution, and with data coupling to the output of interest. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
53.
Raimundas Vidunas Nico M. Temme 《Journal of Mathematical Analysis and Applications》2002,269(1):317-331
Computer algebra algorithms are developed for evaluating the coefficients in Airy-type asymptotic expansions that are obtained from integrals with a large parameter. The coefficients are defined from recursive schemes obtained from integration by parts. An application is given for the Weber parabolic cylinder function. 相似文献
54.
55.
F. Y. Wang 《Journal of Optimization Theory and Applications》1995,84(3):635-652
Optimum design of vibrating cantilevers is a classical problem widely used in the literature and textbooks in structural optimization. The problem, originally formulated and solved by Karihalloo and Niordson (Ref. 5), was to find the optimal beam shape that will maximize the fundamental vibration frequency of a cantilever. Upon reexamination of the problem, it has been found that the original analysis and solution procedure can be simplified and improved substantially. Specifically, the time-consuming inner loop devised for solving the Lagrange multiplier in the original work has been proved to be tolally unnecessary and thus should not be considered in the problem solution. This conclusion has led to a new set of simplified equations for the construction of iteration schemes. New asymptotic expressions for the optimum design solution have been obtained and verified by numerical results. Numerical analysis has shown a significant improvement in convergence rate by the proposed new procedure. Also some obvious numerical errors in the original paper have been identified and corrected.This work was suppoted in part by the University of Arizona Foundation and the Office of the Vice President for Research. The author is grateful to the reviewers for their valuable comments. 相似文献
56.
The three-dimensional transition of the wake flow behind a circular cylinder is studied in detail by direct numerical simulations using 3D incompressible N-S equations for Reynolds number ranging from 200 to 300. New features and vortex dynamics of the 3D transition of the wake are found and investigated. At Re = 200, the flow pattern is characterized by mode A instability. However, the spanwise characteristic length of the cylinder determines the transition features. Particularly for the specific spanwise charac- 相似文献
57.
L. O. Grigor’eva 《International Applied Mechanics》2007,43(3):303-308
The paper proposes a method to solve the problem of vibrations of a radially polarized piezoelectric cylinder subject to nonstationary
electric excitation. The dynamic electromechanical state of the cylinder is analyzed. The time-dependences of electric and
mechanical characteristics are plotted. The distribution of these characteristics over the cross section of a short cylinder
is examined. The region of end disturbances in a long cylinder is identified
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 3, pp. 73–79, March 2007. 相似文献
58.
The plane problem of steady-state small oscillations of a horizontal cylinder located at the interface between two fluids of different densities and indefinite depth is considered in the linear formulation. Boundary integral equations for the surface source distribution are derived. The behavior of the distributed singularities at points of intersection of the body contour and the interface is investigated. The problem of oscillations of a circular cylinder is solved by the multipole expansion method. The apparent mass and damping coefficients of the radiation problem and the reflection coefficient of the problem of scattering of an impinging wave by a floating body are calculated. 相似文献
59.
An asymptotic process for evaluating the frequencies of free axisymmetric vibrations of transversely isotropic hollow cylinders is proposed. This process is developed in detail for a cylinder with hinge-supported ends and free lateral surfaces. The approaches which make it possible to construct algorithms for identifying their natural frequencies within the given interval are tested on model problems. The results from the Kirchhoff-Love and Ambartsumyan theories are compared with those from the 3D elasticity theory. In the first term of an asymptotic expansion, two frequencies coinciding with those obtained using the applied shell theory are found and a countable set of frequencies absent in this theory is determined. 相似文献
60.
本文由横观各向同性的弹性力学方程出发,研究有限长圆柱体的自由振动问题。利用文献「1」的通解,将位移分量和应力分量分别表达成傅里叶-塞尔级数和双曲-贝塞尔级数的形式。通过边界条件和级数的正交关系,得到关于有限长圆柱自由振动频率的特征方程。利用数值方法求解特征根,从而得到圆柱体三维振动的自振频率。 相似文献