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   568787篇
  免费   5903篇
  国内免费   1616篇
化学   274581篇
晶体学   7992篇
力学   29153篇
综合类   13篇
数学   95975篇
物理学   168592篇
  2021年   3770篇
  2020年   4208篇
  2019年   4541篇
  2018年   20257篇
  2017年   20529篇
  2016年   16484篇
  2015年   6863篇
  2014年   8907篇
  2013年   20586篇
  2012年   21583篇
  2011年   36013篇
  2010年   23115篇
  2009年   23384篇
  2008年   30544篇
  2007年   34459篇
  2006年   16659篇
  2005年   20784篇
  2004年   17374篇
  2003年   16159篇
  2002年   13710篇
  2001年   13774篇
  2000年   10575篇
  1999年   8096篇
  1998年   6778篇
  1997年   6482篇
  1996年   6388篇
  1995年   5670篇
  1994年   5547篇
  1993年   5376篇
  1992年   5953篇
  1991年   6066篇
  1990年   5779篇
  1989年   5606篇
  1988年   5641篇
  1987年   5512篇
  1986年   5213篇
  1985年   6711篇
  1984年   6853篇
  1983年   5444篇
  1982年   5530篇
  1981年   5497篇
  1980年   5115篇
  1979年   5507篇
  1978年   5647篇
  1977年   5450篇
  1976年   5422篇
  1975年   5000篇
  1974年   4955篇
  1973年   5001篇
  1972年   3517篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
The motion of the front of crystallization and the growth of a film at the surface of a plate are analyzed in the case of a laminar and in the case of a turbulent flow mode. Conditions are determined under which there occurs a transition from a matt inhomogeneous structure to a transparent homogeneous structure of ice. It is shown that, for a film to be steadily preserved at the plate surface, the film thickness must be larger than a critical equilibrium-thickness value h b.c, in which case a transparent homogeneous structure of ice is formed. Otherwise, the film at the plate surface is unstable and disappears in the course of time. The icing of aircrafts is the most important application of the results obtained in this study.  相似文献   
972.
The cross section of absorption of electromagnetic radiation by a fine spherical metal particle is calculated. The influence of the skin effect on the absorption cross-section is estimated for an arbitrary ratio between the free path and size of the particle. The results of this work are compared with those obtained earlier in the framework of classical electrodynamics. It is shown that taking into account the kinetic effects modifies essentially the known data for the skin effect in a spherical particle.  相似文献   
973.
The establishment of the steady-state dopant profile in a medium with a time-variable diffusion coefficient is considered within the approach proposed previously for estimating mass-and heat-transfer time characteristics. It is shown that the time it takes for the equilibrium concentration to set in may be increased or decreased by appropriately choosing the law of variation of the diffusion coefficient.  相似文献   
974.
Technical Physics - An analytical expression for the generatrix of the shape of a nonlinearly vibrating charged drop of a perfect incompressible conducting fluid immersed in an ideal incompressible...  相似文献   
975.
A theory of a planar disk-shaped RF plasma source under anomalous skin effect conditions is developed. In the absence of an external magnetic field, such conditions are satisfied for transverse electromagnetic waves with phase velocities below the electron thermal velocity, and, in the presence of this field, they are satisfied for electron cyclotron waves with frequencies corresponding to the resonant absorption line. For each of these cases, the RF field power deposited in a plasma with given parameters is determined and the equivalent plasma resistance is calculated.  相似文献   
976.
The special features of the structure and phase composition of nanocrystalline zirconia-based powders subjected to shock-wave treatment are studied. The investigations show that zirconia with small amounts of yttria and/or alumina is in nanocrystalline and quasi-amorphous states representing a nonequilibrium solid solution of ZrO2 (Y, Al) and that an increase in the monoclinic phase abundance is associated with a reduction in the critical size of tetragonal crystallites due to an accumulation of lattice microdistortions. The monoclinic phase in powders with yttria and alumina additions is not formed even with shock compression at pressures up to 20 GPa. This is attributed to the fact that the resultant lattice microdistortion level is inadequate to destabilize the nanocrystalline tetragonal phase. Relaxation of microdistortions on annealing causes the critical size of tetragonal crystallites to increase. As this takes place, the monoclinic phase is converted into the tetragonal one.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 61–70, September, 2004.  相似文献   
977.
The mass spectrum of a coupled state is analytically determined. The mechanism of production of a constituent mass of particles forming a coupled state is explained. The change of the coupled state and constituent particle component masses attendant to changes of the coupling constant is analyzed. The mass spectrum of a two-gluon glueball is determined with allowance for spin-orbital and spin-spin interactions.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 33–41, December, 2004.  相似文献   
978.
979.
980.
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