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   584806篇
  免费   4987篇
  国内免费   1740篇
化学   287711篇
晶体学   8938篇
力学   28584篇
综合类   9篇
数学   81595篇
物理学   184696篇
  2021年   4255篇
  2020年   4583篇
  2019年   5243篇
  2018年   12824篇
  2017年   13396篇
  2016年   12900篇
  2015年   6664篇
  2014年   9845篇
  2013年   24430篇
  2012年   21234篇
  2011年   30893篇
  2010年   20885篇
  2009年   20753篇
  2008年   27373篇
  2007年   29840篇
  2006年   18447篇
  2005年   21160篇
  2004年   17440篇
  2003年   15769篇
  2002年   14292篇
  2001年   15590篇
  2000年   11866篇
  1999年   9147篇
  1998年   7644篇
  1997年   7556篇
  1996年   7188篇
  1995年   6392篇
  1994年   6202篇
  1993年   6201篇
  1992年   6725篇
  1991年   6912篇
  1990年   6624篇
  1989年   6519篇
  1988年   6353篇
  1987年   6377篇
  1986年   6061篇
  1985年   7920篇
  1984年   8116篇
  1983年   6687篇
  1982年   7072篇
  1981年   6735篇
  1980年   6601篇
  1979年   6864篇
  1978年   7126篇
  1977年   6885篇
  1976年   7066篇
  1975年   6479篇
  1974年   6559篇
  1973年   6845篇
  1972年   4604篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
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   
72.
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   
73.
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   
74.
75.
We give a coring version for the duality theorem for actions and coactions of a finitely generated projective Hopf algebra. We also provide a coring analogue for a theorem of H.-J. Schneider, which generalizes and unifies the duality theorem for finite Hopf algebras and its refinements. This paper was written while the first author visited the Mathematics Departments of Syracuse University and California State University Dominguez Hills. He would like to thank both departments for their hospitality.  相似文献   
76.
77.
The mass power spectrum for a Universe dominated by the Chaplygin gas is evaluated numerically from scales of the order of the Hubble horizon to 100 Mpc. The results are compared with a pure baryonic Universe and a cosmological constant model. In all three cases, the spectrum increases with k, the wavenumber of the perturbations. The slope of the spectrum is higher for the baryonic model and smaller for the cosmological constant model, the Chaplygin gas interpolating these two models. The results are analyzed in terms of the sound velocity of the Chaplygin gas and the moment the Universe begins to accelerate.  相似文献   
78.
In the study of the behaviors of barriers in an enclosed field, one should take into account such phenomena as sound energy reflection, absorption, scattering and diffraction. Therefore, the study is much more difficult than that in free field. In this paper, sound barriers are classified into four kinds according to their size, number and shape. Each kind of barriers is modelled by a corresponding method based on a computer program—SOFIS. The program combines the ray-tracing technique and statistical method. The impulse response and some acoustical parameters such as sound pressure level at different positions can be calculated by the program, no matter there are a certain kind of barriers in the field or the field is empty. The ray-tracing program and the algorithms for various barriers are validated by the comparison between measurement and prediction of the reverberation room and the anechoic room of the Northwestern Polytechnic University.  相似文献   
79.
80.
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