首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1364937篇
  免费   29978篇
  国内免费   12234篇
化学   682934篇
晶体学   20773篇
力学   76456篇
综合类   420篇
数学   244569篇
物理学   381997篇
  2021年   14672篇
  2020年   17035篇
  2019年   17273篇
  2018年   14192篇
  2017年   12475篇
  2016年   29251篇
  2015年   22082篇
  2014年   31942篇
  2013年   76464篇
  2012年   40062篇
  2011年   37133篇
  2010年   39022篇
  2009年   41433篇
  2008年   35876篇
  2007年   31332篇
  2006年   36742篇
  2005年   29776篇
  2004年   30630篇
  2003年   28739篇
  2002年   29785篇
  2001年   28411篇
  2000年   24920篇
  1999年   22936篇
  1998年   21497篇
  1997年   21344篇
  1996年   21546篇
  1995年   19591篇
  1994年   18985篇
  1993年   18488篇
  1992年   18267篇
  1991年   18590篇
  1990年   17730篇
  1989年   17700篇
  1988年   17188篇
  1987年   17198篇
  1986年   16087篇
  1985年   22512篇
  1984年   23751篇
  1983年   19954篇
  1982年   21643篇
  1981年   20851篇
  1980年   20189篇
  1979年   20326篇
  1978年   21637篇
  1977年   21221篇
  1976年   20944篇
  1975年   19608篇
  1974年   19247篇
  1973年   19736篇
  1972年   14247篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
Using the method of the tensor Green’s function of the wave equation, the differential and total cross sections for the scattering of surface optical electromagnetic waves (surface plasmon polaritons) by a spherical nanoparticle into surface plasmon polaritons and light have been obtained with the inclusion of the magnetic dipole contribution. Using the example of noble metal systems, it has been shown that the magnetic dipole contribution may significantly affect the angular dependence of the differential cross sections and increase their anisotropy as the plasmon wavelength increases.  相似文献   
132.
Dielectric properties of polymer-liquid crystal mixture, having constituent polymer, poly-butyl methacrylate (PBMA) and liquid crystal, cholesteryl nonanoate, are reported as a function of frequency and temperature. The measurement has been done in a temperature range of 300-375 K and frequency range of 100 Hz-10 MHz. The dielectric permittivity and dielectric loss shows significant changes with the addition of polymer molecules in liquid crystal. The significant feature of composite formation is that the pure liquid crystal and polymer do not show dielectric relaxation in the frequency range covered, while the composite shows relaxation peak at a particular frequency. The optical transmittance of pure liquid crystal and composite has also been measured and compared.  相似文献   
133.
We report morphologic changes of metallic surfaces at the onset of ablation, starting from gentle ablation to the emergence of ablation craters. The evolution of both observed melting zones and of ablation craters therein are investigated in dependence of the ablation laser fluence for nanosecond ultraviolet laser pulses. Further, consequences of crater formation for cluster synthesis within the released atomic vapor are pointed out. PACS 52.38.Mf; 79.20.Ds; 65.40.De  相似文献   
134.
Space-time directional Lyapunov exponents are introduced. They describe the maximal velocity of propagation to the right or to the left of fronts of perturbations in a frame moving with a given velocity. The continuity of these exponents as function of the velocity and an inequality relating them to the directional entropy is proved.  相似文献   
135.
Summary The main purpose of this paper is to introduce the concepts of η-sets, ηζ-sets,η-continuity and ηζ-continuity and to obtain a decomposition of continuity.  相似文献   
136.
The paper mentioned above is a contribution of the authors to Volume 18 (2002) of this journal, see . Recently, J. Domsta pointed out to us that the proof of Theorem 4.2 in that paper contains an error. The purpose of this addendum is to present a correct argument for it.  相似文献   
137.
A test for a function to be a solution of an elliptic PDE is given in terms of extensions, as solutions, from the boundaries inside the domains belonging to an isotopic family. It generalizes a result of Ehrenpreis for spheres moved along a straight line.

  相似文献   

138.
We give sufficient conditions for Sobolev and Lipschitz functions in terms of their lower scaled-oscillation. The sharpness of these conditions is shown by examples. Our examples also show that a Stepanov-type differentiability theorem does not hold under the boundedness assumption of the lower scaled-oscillation.

  相似文献   

139.
140.
The feasibility of an 84 GHz, 500 kW, CW gyrotron for ECRH on an experimental tokamak will be presented in this paper. Mode competition and mode selection procedures are carefully investigated by considering various candidate modes and the TE10,4 mode is chosen as the operating mode. A conventional cylindrical cavity resonator with weak input and output tapers and parabolic roundings is considered for interaction studies. Self-consistent, both single mode and time-dependent, calculations are carried out and power and efficiencies are computed for a typical set of beam parameters. The results show that an output power of well over 500 kW, CW and efficiency around 40% can be reached without a depressed collector.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号