全文获取类型
收费全文 | 7795篇 |
免费 | 335篇 |
国内免费 | 226篇 |
专业分类
化学 | 644篇 |
晶体学 | 10篇 |
力学 | 1808篇 |
综合类 | 12篇 |
数学 | 3166篇 |
物理学 | 1640篇 |
无线电 | 1076篇 |
出版年
2024年 | 17篇 |
2023年 | 119篇 |
2022年 | 117篇 |
2021年 | 121篇 |
2020年 | 184篇 |
2019年 | 124篇 |
2018年 | 128篇 |
2017年 | 161篇 |
2016年 | 192篇 |
2015年 | 206篇 |
2014年 | 404篇 |
2013年 | 739篇 |
2012年 | 338篇 |
2011年 | 552篇 |
2010年 | 480篇 |
2009年 | 540篇 |
2008年 | 448篇 |
2007年 | 431篇 |
2006年 | 367篇 |
2005年 | 280篇 |
2004年 | 273篇 |
2003年 | 243篇 |
2002年 | 193篇 |
2001年 | 159篇 |
2000年 | 134篇 |
1999年 | 142篇 |
1998年 | 159篇 |
1997年 | 118篇 |
1996年 | 122篇 |
1995年 | 81篇 |
1994年 | 107篇 |
1993年 | 91篇 |
1992年 | 93篇 |
1991年 | 77篇 |
1990年 | 60篇 |
1989年 | 48篇 |
1988年 | 46篇 |
1987年 | 50篇 |
1986年 | 20篇 |
1985年 | 48篇 |
1984年 | 49篇 |
1983年 | 25篇 |
1982年 | 19篇 |
1981年 | 17篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 10篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1968年 | 1篇 |
排序方式: 共有8356条查询结果,搜索用时 15 毫秒
21.
22.
Y.-D Feng Y.-S. Wang Z.-M. Zhang 《Archive of Applied Mechanics (Ingenieur Archiv)》2003,73(5-6):337-347
Summary A 2D time-domain Boundary Element Method (BEM) is applied to solve the problem of transient scattering of plane waves by an inclusion with a unilateral smooth contact interface. The incident wave is assumed strong enough so that localized separations take place along the interface. The present problem is indeed a nonlinear boundary value problem since the mixed boundary conditions involve unknown intervals (separation and contact regions). In order to determine the unknown intervals, an iterative technique is developed. As an example, we consider the scattering of plane waves by the cross section of a circular cylinder embedded in an infinite solid. Numerical results for the near field solutions are presented. The distortion of the response waves and the variation of the interface states are discussed.
The financial support by the China National Natural Science Foundation under Grant No. 19872001 and No. 59878004 is gratefully acknowledged. The second author is also grateful to the support of the National Science Fund for Distinguished Young Scholars under Grant No. 10025211. 相似文献
23.
In this paper we compute the number of curves of genus 2 defined over a finite field k of odd characteristic up to isomorphisms defined over k; the even characteristic case is treated in an ongoing work (G. Cardona, E. Nart, J. Pujolàs, Curves of genus 2 over field of even characteristic, 2003, submitted for publication). To this end, we first give a parametrization of all points in
, the moduli variety that classifies genus 2 curves up to isomorphism, defined over an arbitrary perfect field (of zero or odd characteristic) and corresponding to curves with non-trivial reduced group of automorphisms; we also give an explicit representative defined over that field for each of these points. Then, we use cohomological methods to compute the number of k-isomorphism classes for each point in
. 相似文献
24.
FD—TD在分析FSS中的应用 总被引:3,自引:0,他引:3
本文讨论了用FD TD分析FSS的有关问题,提出了一种适合于在任意入射角情况下分析FSS的有效吸收边界条件,分别以单层、双层FSS为例进行了计算.数值结果和矢量模式法、谱域法的结果非常一致. 相似文献
25.
LIKAITAI HEYINNIAN XIANGYIMIN 《高校应用数学学报(英文版)》1994,9(1):11-30
This paper deals with the inertial manifold and the approximate inertial manifold concepts of the Navier-Stokes equations with nonhomogeneous boundary conditions and inertial algorithm. Furtheremore, we provide the error estimates of the approximate solutions of the Navier-Stokes Equations. 相似文献
26.
唐元洪 《固体电子学研究与进展》1997,17(4):329-332
提出了用空间电荷限制电流(SCLC)法测量非晶硅材料的有效隙态密度的新方法,并且报告了用4061A型半导体综合测试仪测量有效隙态密度的结果。测量结果发现与用低频电容法所得结果相符。 相似文献
27.
本文考察了以微波等离子体炬(MPT)为光源,电热钽丝环进样时,溶液中共存元素对发射信号的影响。 相似文献
28.
分离变量法与等腰直角三角形波导的边值问题 总被引:4,自引:0,他引:4
根据叠加原理,讨论等腰直角三角形波导边值问题的IE波解和TM波解,纠正有关文献中的错误解法,指出分离变量法的适用条件。 相似文献
29.
N.P. Somasiri W.K. Toh X. Chen I.D. Robertson A.A. Rezazadeh 《International Journal of Infrared and Millimeter Waves》2002,23(12):1777-1785
This paper describes numerical modelling of a dual band multi-layered microstrip patch antenna operating at 35GHz on an in-house semi-insulating GaAs substrate. The simulated and measured resonant frequencies at both lower and upper resonant frequencies will be compared to check the accuracy of the different numerical modelling techniques. 相似文献
30.
Tom Kennedy 《Journal of statistical physics》1990,59(1-2):195-220
A fixed-point equation on an infinite-dimensional space is proposed as an alternative to the usual definition of the infinite-volume limit in discrete lattice spin systems in the high-temperature phase. It is argued heuristically that the free energy and correlation functions one obtains by solving this equation agree with the usual definitions of these quantities. A theorem is then proved that says that if a certain finite-volume condition is satisfied, then this fixed-point equation has a solution and the resulting free energy is analytic in the parameters in the Hamiltonian. For particular values of the temperature this finite-volume condition may be checked with the help of a computer. The two-dimensional Ising model is considered as a test case, and it is shown that the finite-volume condition is satisfied for0.77
critical. 相似文献