全文获取类型
收费全文 | 4098篇 |
免费 | 505篇 |
国内免费 | 193篇 |
专业分类
化学 | 972篇 |
晶体学 | 20篇 |
力学 | 1323篇 |
综合类 | 22篇 |
数学 | 775篇 |
物理学 | 1684篇 |
出版年
2024年 | 6篇 |
2023年 | 31篇 |
2022年 | 73篇 |
2021年 | 69篇 |
2020年 | 110篇 |
2019年 | 93篇 |
2018年 | 93篇 |
2017年 | 109篇 |
2016年 | 122篇 |
2015年 | 95篇 |
2014年 | 173篇 |
2013年 | 318篇 |
2012年 | 168篇 |
2011年 | 223篇 |
2010年 | 200篇 |
2009年 | 267篇 |
2008年 | 280篇 |
2007年 | 282篇 |
2006年 | 249篇 |
2005年 | 217篇 |
2004年 | 213篇 |
2003年 | 178篇 |
2002年 | 171篇 |
2001年 | 122篇 |
2000年 | 97篇 |
1999年 | 84篇 |
1998年 | 93篇 |
1997年 | 98篇 |
1996年 | 90篇 |
1995年 | 60篇 |
1994年 | 65篇 |
1993年 | 60篇 |
1992年 | 59篇 |
1991年 | 40篇 |
1990年 | 32篇 |
1989年 | 19篇 |
1988年 | 30篇 |
1987年 | 24篇 |
1986年 | 13篇 |
1985年 | 16篇 |
1984年 | 16篇 |
1983年 | 4篇 |
1982年 | 17篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有4796条查询结果,搜索用时 15 毫秒
11.
W. Hufenbach R. Böhm A. Langkamp L. Kroll T. Ritschel 《Mechanics of Composite Materials》2006,42(2):151-162
The basic damage and failure models of multiaxially reinforced composites with a thermoplastic matrix are presented and verified.
Within the framework of continuum damage mechanics, a phenomenological model is introduced, where the damage is defined as
a change in the elasticity tensor. For damage identification, a specific ultrasonic device was developed. A combination of
an immersion set-up and a contact coupling device formed a system for an efficient determination of stiffness-tensor components
from convenient sets of velocity measurements. Linked to a tensile machine, it allowed us to measure the anisotropic damage
of the new materials group caused by tensile loading.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 2, pp. 221–234, March–April, 2006. 相似文献
12.
用FDTD方法计算了二维正方晶胞各向异性碲圆柱光子晶体的点缺陷模.为了得到TE,TM模式在完全禁带中具有相同共振频率的缺陷模,对中心点缺陷半径Rd以及中心附近对称位置的点缺陷半径Rn做了一系列微调.计算表明,TM模对于Rn的变化不敏感,而TE模随着Rn的改变出现了明显的规则的移动趋势.通过计算分析,发现对应于f=0.4的背景(R=0.3568a),当Rd=0.55a,Rn=0.26a时在完全禁带中TE和TM的缺陷模具有相同的共振频率ω0=0.2466ωe(其中ωe=2πca,a为晶格常数)
关键词:
时域有限差分法
光子晶体
缺陷模
各向异性 相似文献
13.
Arup Baksi Bidyut Kumar Roy Rasajit Kumar Bera 《Mathematical and Computer Modelling》2006,44(11-12):1069-1079
The fundamental equations of the problems of generalized thermoelasticity with one relaxation parameter including heat sources in infinite rotating magneto-thermo-viscoelastic media have been derived in the form of a vector matrix differential equation in the Laplace transform domain for a one dimensional problem. These equations have been solved by the eigenvalue approach to determine deformations, stress, and temperature. The results have been compared to those available in the existing literature. The graphs have been drawn to show the effect of rotation in the medium. 相似文献
14.
Christodoulos Athanasiadis Nikolaos Berketis 《Mathematical Methods in the Applied Sciences》2006,29(1):27-48
A spherical electromagnetic wave propagating in a chiral medium is scattered by a bounded chiral obstacle which can have any of the usual properties. Reciprocity and general scattering theorems, relating the scattered fields due to scattering of waves from a point source put in any two different locations are established. Applying the general scattering theorem for appropriate locations and polarizations of the point source we prove an associated forward scattering theorem. Mixed scattering relations, relating the scattered fields due to a plane wave and the far‐field patterns due to a spherical wave, are also established. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
15.
The paper deals with the stress, displacement, pore and fissure pressures fields induced by the drilling and/or the pressurization of a vertical borehole in a formation of water-saturated porous media with double porosity. The solution includes the boundary condition of non-hydrostatic in situ state of stress. The solid skeleton is assumed to behave as a linearly poroelastic material with compressible constituents. The analytical solution is derived in Laplace’s space and transformed to the time domain using a numerical inversion technique. The histories of pore and fissure pressures are illustrated to show the influence of permeabilities of the pore and fissure systems. 相似文献
16.
Jin Cheng Ching-Lung Lin Gen Nakamura 《Proceedings of the American Mathematical Society》2005,133(8):2359-2367
In this paper we prove the following kind of unique continuation property. That is, the zero on each geodesic of the solution in a real analytic hypersurface for second order anisotropic hyperbolic systems with real analytic coefficients can be continued along this curve.
17.
18.
Deák L. Bottyán L. Major M. Nagy D. L. Spiering H. Szilágyi E. Tanczikó F. 《Hyperfine Interactions》2002,144(1-4):45-52
Hyperfine Interactions - Synchrotron Mössbauer Reflectometry (SMR), the grazing incidence nuclear resonant scattering of synchrotron radiation, can be applied to perform depth-selective phase... 相似文献
19.
Reaction diffusion systems on cylindrical domains with terms that vary rapidly and periodically in the unbounded direction can be analyzed by averaging techniques. Here, using iterated normal form transformations and Gevrey regularity of bounded solutions, we prove a result on exponential averaging for such systems, i.e., we show that traveling wave solutions can be described by a spatially homogenous equation and exponentially small remainders. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
20.
An optical element constructed by stacking a set of binary-phase grating sheets can simulate the functions of optically recorded volume gratings. Our electromagnetic numerical study also shows that if one of the grating sheets is replaced by another one with different grating period, power spectrum of the diffracted wave changes completely with extra diffraction orders. This property will claim strong advantage in security document applications. Analysis of alignment error reveals interesting phenomena concerning to how misalignment affects diffraction efficiency. 相似文献