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   1393883篇
  免费   25843篇
  国内免费   7778篇
化学   696877篇
晶体学   20914篇
力学   76209篇
综合类   115篇
数学   246278篇
物理学   387111篇
  2021年   13582篇
  2020年   15963篇
  2019年   16077篇
  2018年   15892篇
  2017年   14547篇
  2016年   29261篇
  2015年   21083篇
  2014年   30425篇
  2013年   74337篇
  2012年   40813篇
  2011年   40829篇
  2010年   39728篇
  2009年   41713篇
  2008年   39294篇
  2007年   36075篇
  2006年   38202篇
  2005年   33205篇
  2004年   32963篇
  2003年   30408篇
  2002年   30717篇
  2001年   29707篇
  2000年   25487篇
  1999年   22870篇
  1998年   21152篇
  1997年   21070篇
  1996年   21168篇
  1995年   19184篇
  1994年   18643篇
  1993年   18196篇
  1992年   18232篇
  1991年   18497篇
  1990年   17696篇
  1989年   17771篇
  1988年   17397篇
  1987年   17304篇
  1986年   16209篇
  1985年   22619篇
  1984年   23859篇
  1983年   20055篇
  1982年   21664篇
  1981年   20896篇
  1980年   20223篇
  1979年   20467篇
  1978年   21755篇
  1977年   21364篇
  1976年   21061篇
  1975年   19771篇
  1974年   19434篇
  1973年   19905篇
  1972年   14395篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
It has been studied how the conditions of machining and the elastic tensile stresses affect the magnetic properties of amorphous metal wires of composition Fe75Si10B15 produced by drawing from a melt. The magnetic characteristics of wires subjected to both thermal treatment and treatment with a continuous electric current of different magnitude have been investigated. The residual induction of wires is their magnetic parameter most sensitive to the conditions of treatment. The dependences of the residual induction on temperature and on the magnitude of the treating electric current are qualitatively similar. The greatest changes in residual induction are observed in the range of treating electric currents from 0.5 to 0.8 A, which can be associated with the processes of structural relaxation and crystallization occurring in the wires. The run of the dependence of the residual induction on the magnitude of tensile stresses is nonmonotonic in character and is determined by the level of internal hardening stresses of the test wires.  相似文献   
982.
It is shown that the Kapitza effect in charge-ordered layered crystals can be explained for the case of a parallelism of magnetic field and measuring current when the Landau quantization and its effect on the charge-carrier scattering are considered. There is a linear correlation between the magnetic field and longitudinal resistance under the assumption that the scattering of charge carriers by acoustic phonons is dominant, and the band-to-band transitions are suppressed. The relations for the Kapitza coefficient are derived for different degrees of electron gas degeneracy and different values of interaction resulting in layered charge ordering.  相似文献   
983.
984.
In addition to the solution of the quantum mechanical problem on the motion of a free electron in a magnetic field, given by L. D. Landau in his pioneering work, this quantum mechanical problem is solved in view of the fact that the sum of the components of the free kinetic energy of an electron along two axes is a periodic quantity varying identically within the boundaries of every Landau energy level. This periodicity is a consequence of the quantized motion of an electron in a plane normal to the direction of the external magnetic field.  相似文献   
985.
In the present paper, the mathematical expectation and variance of the number of queries in an infinite linear queue are calculated for the Poisson synchronous doubly stochastic stream of incoming queries with two intensity states.  相似文献   
986.
The problem of investigation of the amplitude and phase structure of a time-varying probing optical signal and the structure of time-varying inhomogeneities of a substance tested by this signal is considered. The analysis is concerned, in particular, with determination of the structure of signals and processes with resolution in the pico- and femtosecond range. The scheme used for the analysis is based on registration of four spatially separated spectra of the studied radiation. The spectra are formed in a four-channel scheme with a twin-wave Michelson interferometer and a spectral device. Modulators based on electrooptical crystals (perovskites) are placed in the channels. The sum spectra are formed: without modulators, with the effect of either of the modulators, and with both of them affecting the radiation. The effect of the studied substance implies either modulating the radiation (in this case it is described by multiplication) or redistributing the radiation (then it is described by convolution).  相似文献   
987.
988.
989.
990.
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