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   262916篇
  免费   3829篇
  国内免费   505篇
化学   145616篇
晶体学   3387篇
力学   11020篇
综合类   7篇
数学   29864篇
物理学   77356篇
  2021年   2228篇
  2020年   2571篇
  2019年   2769篇
  2018年   3826篇
  2017年   3730篇
  2016年   5732篇
  2015年   3719篇
  2014年   5211篇
  2013年   11854篇
  2012年   10486篇
  2011年   12158篇
  2010年   8378篇
  2009年   8078篇
  2008年   10915篇
  2007年   10849篇
  2006年   10115篇
  2005年   9295篇
  2004年   8273篇
  2003年   7207篇
  2002年   7088篇
  2001年   6936篇
  2000年   5309篇
  1999年   4064篇
  1998年   3555篇
  1997年   3408篇
  1996年   3192篇
  1995年   2872篇
  1994年   2914篇
  1993年   2766篇
  1992年   3091篇
  1991年   3202篇
  1990年   2967篇
  1989年   2995篇
  1988年   2805篇
  1987年   2646篇
  1986年   2520篇
  1985年   3308篇
  1984年   3463篇
  1983年   2860篇
  1982年   3112篇
  1981年   2884篇
  1980年   2765篇
  1979年   2946篇
  1978年   3215篇
  1977年   3057篇
  1976年   3062篇
  1975年   2911篇
  1974年   2982篇
  1973年   2940篇
  1972年   1952篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
Rotational temperature and nitrogen number density are measured in the shock wave/boundary layer interaction region in the vicinity of a two-dimensional compression corner disposed in a low pressure, 55 K, Mach 10 hypersonic air flow. Spatially-resolved data are recorded using a nonlinear optical technique named dual-line coherent anti-Stokes Raman scattering (DLCARS). Averaged temperature and density profiles are compared with those predicted by a Navier-Stokes solver. Good agreement is found.  相似文献   
994.
The theory of many-body systems constitutes one of the most complex part of quantum mechanics. Closed results are not readily available and approximations become extremely involved. It is, therefore, of considerable interest that the quantization of certain simple collective motions of particles can describe the energies of atoms, nuclei and particle models rather well. We describe here the most elementary examples of such structures.Dedicated to H. Walther, a great scientist and who demonstrated among many other things the regular shapes of atomic particles, the subject of this essay  相似文献   
995.
996.
Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 313–314, March–April, 1995. Original article submitted November 7, 1994.  相似文献   
997.
The free groups of exponent eight are shown to differ from thoseof sufficiently large exponent in the nature of their finitesubgroups.  相似文献   
998.
The conventional and photothermally modulated (PM) ferromagnetic resonance (FMR) of magnetostatic modes (MSM) in yttrium iron garnet (YIG) films have been investigated as a function of temperature. Approaching the ferrimagnetic transition at T c=560 K a strong enhancement of the PM-FMR signal amplitude is observed which is accompanied by a change of the signal shape. The observations are discussed in the framework of a model that takes into account the temperature derivatives of those quantities that contribute to the high-frequency susceptibility. At temperatures still below T c a paramagnetic line emerges. The MSM disappear in a state of finite magnetization which is explained on the basis of damping of the MSM being important in the vicinity of the magnetic phase transition. Additionally, frequency and power dependent measurements are presented and the imaging ability of PM-FMR is demonstrated.  相似文献   
999.
The current status of the R & D activities is presented on electron beam processing of polymers being carried out at TRCRE. Topics included are sterilization of medical products, graft polymers for selective separation or absorbents and curing of liquid prepolymer-monomer systems.  相似文献   
1000.
Studies show that branching the side chains of hexakis(acoyloxy)-benzenes (HAB) and -cyclohexanes (HAChx) does not modify the structure of the discotic mesophase formed. Shear fields appear to act on entire columns, not on individual discs, thereby causing alignment of columns in the shear direction. X-ray diffraction patterns of samples at temperatures between 30°C and 40°C above the clearing temperature provide evidence for the presence of mesophase order.  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