全文获取类型
收费全文 | 652篇 |
免费 | 30篇 |
国内免费 | 3篇 |
专业分类
化学 | 431篇 |
晶体学 | 2篇 |
力学 | 18篇 |
数学 | 121篇 |
物理学 | 113篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 14篇 |
2018年 | 5篇 |
2017年 | 12篇 |
2016年 | 20篇 |
2015年 | 24篇 |
2014年 | 32篇 |
2013年 | 35篇 |
2012年 | 51篇 |
2011年 | 54篇 |
2010年 | 33篇 |
2009年 | 36篇 |
2008年 | 32篇 |
2007年 | 19篇 |
2006年 | 30篇 |
2005年 | 25篇 |
2004年 | 27篇 |
2003年 | 19篇 |
2002年 | 23篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 15篇 |
1998年 | 13篇 |
1997年 | 14篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1972年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有685条查询结果,搜索用时 0 毫秒
51.
We consider (in two-dimensional Euclidean space) the scattering of a plane, time-harmonic acoustic wave by an inhomogeneous medium Ω with compact support and a bounded obstacle D lying completely outside of the inhomogeneous medium. We show that one may determine the shape of D and the local speed of sound in Ω from a knowledge of the asymptotic behavior of the scattered wave (i.e. the far field). This is done by considering a constrained optimization problem and employing integral equation and conformal mapping techniques. By assuming a priori that the functions which determine the shape of D and the local speed of sound in Ω lie in given compact sets, we show that the problem is stable, in the sense that the solution of the inverse scattering problem depends continuously on the far field data. 相似文献
52.
Li Chen Ling Hsiao Gerald Warnecke 《应用数学学报(英文版)》2007,23(1):9-28
This paper considers a kind of strongly coupled cross diffusion parabolic system,which can be usedas the multi-dimensional Lyumkis energy transport model in semiconductor science.The global existence andlarge time behavior are obtained for smooth solution to the initial boundary value problem.When the initialdata are a small perturbation of an isothermal stationary solution,the smooth solution of the problem under theinsulating boundary condition,converges to that stationary solution exponentially fast as time goes to infinity. 相似文献
53.
T. S. Angell R. E. Kleinman G. C. Hsiao 《Mathematical Methods in the Applied Sciences》1982,4(1):164-193
In this paper we study the application of boundary integral equation methods for the solution of the third, or Robin, boundary value problem for the exterior Helmholtz equation. In contrast to earlier work, the boundary value problem is interpreted here in a weak sense which allows data to be specified in L∞ (?D), ?D being the boundary of the exterior domain which we assume to be Lyapunov of index 1. For this exterior boundary value problem, we employ Green's theorem to derive a pair of boundary integral equations which have a unique simultaneous solution. We then show that this solution yields a solution of the original exterior boundary value problem. 相似文献
54.
We First define a continuous extension of the Laquerre polynomials and give some properties of this continuous extension. Then we define a continuous Laguerre transform for square integrable functions, give some properties of this transform and give a sampling theorem that is similar to the well known Shannon-Whittaker Sampling Theorem for Fourier transform. The inverse of this transform is also given. 相似文献
55.
56.
In this paper we consider a wavelet algorithm for the piecewise constant collocation method applied to the boundary element solution of a first kind integral equation arising in acoustic scattering. The conventional stiffness matrix is transformed into the corresponding matrix with respect to wavelet bases, and it is approximated by a compressed matrix. Finally, the stiffness matrix is multiplied by diagonal preconditioners such that the resulting matrix of the system of linear equations is well conditioned and sparse. Using this matrix, the boundary integral equation can be solved effectively. 相似文献
57.
Global Existence and Exponential Stability of Smooth Solutions to a Full Hydrodynamic Model to Semiconductors 总被引:1,自引:0,他引:1
We study a full hydrodynamic semiconductor model in multi-space dimension. The global existence of smooth solutions is established
and the exponential stability of the solutions as is investigated.
Received November 14, 2000; in revised form March 25, 2002 Published online August 5, 2002 相似文献
58.
A silicon on insulator (SOI)-based trapezoidal waveguide with a 45° reflector for noncoplanar optical interconnect is demonstrated. The proposed waveguide is fabricated on an orientation-defined (100) SOI substrate by using a single-step anisotropic wet-etching process. The optical performances of proposed waveguides are numerically and experimentally studied. Transmittance of -4.51 dB, alignment tolerance of ±20 μm, cross talk of -53 dB, and propagation loss of -0.404 dB/cm are achieved The proposed waveguide would be a basic element and suitable for the future intrachip optical interconnects. 相似文献
59.
60.
在前文工作的基础上,结合MNDO/EHMO分子轨道方法和自然杂化轨道方法,具体计算了CC键和CP键的核自旋偶合常数.计算结果表明,1JCC和1JCP主要由成键原子的轨道杂化作用和键极性这两种结构因素所决定.为从简单价键理论角度解释和计算1JCC和1JCP值提供了简便直观的方法. 相似文献