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   672031篇
  免费   5653篇
  国内免费   1965篇
化学   340673篇
晶体学   10033篇
力学   33414篇
综合类   18篇
数学   87782篇
物理学   207729篇
  2021年   5849篇
  2020年   6409篇
  2019年   7289篇
  2018年   9708篇
  2017年   9751篇
  2016年   13620篇
  2015年   7639篇
  2014年   12703篇
  2013年   30031篇
  2012年   22917篇
  2011年   27515篇
  2010年   20255篇
  2009年   20205篇
  2008年   25718篇
  2007年   25654篇
  2006年   23545篇
  2005年   21130篇
  2004年   19595篇
  2003年   17566篇
  2002年   17481篇
  2001年   18861篇
  2000年   14583篇
  1999年   11425篇
  1998年   9805篇
  1997年   9592篇
  1996年   9055篇
  1995年   8209篇
  1994年   8178篇
  1993年   7986篇
  1992年   8465篇
  1991年   8934篇
  1990年   8516篇
  1989年   8384篇
  1988年   8258篇
  1987年   8023篇
  1986年   7614篇
  1985年   9942篇
  1984年   10397篇
  1983年   8613篇
  1982年   9015篇
  1981年   8601篇
  1980年   8210篇
  1979年   8734篇
  1978年   8991篇
  1977年   8870篇
  1976年   8850篇
  1975年   8366篇
  1974年   8254篇
  1973年   8554篇
  1972年   6204篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
The dependence of the energy characteristics on an adiabatically slowly increasing external force is determined analytically for an anharmonic oscillator. The analytical results are confirmed by a numerical calculation. The nature of the force dependences of the energy characteristics are determined and discussed. Fiz. Tverd. Tela (St. Petersburg) 39, 153–157 (January 1997)  相似文献   
122.
Mass distributions of fragments in the low-energy fission of nuclei from 187Ir to 213At have been analysed. This analysis has shown that shell effects in symmetric-mode fragment mass yields from the fission of pre-actinide nuclei could be described if one assumes the existence of two strongly deformed neutron shells in the arising fragments with neutron numbers N1 ≈ 52 and N2 ≈ 68. A new method has been proposed for quantitatively describing the mass distributions of the symmetric fission mode for pre-actinides with A ≈ 180–220.  相似文献   
123.
Flowing and static gas-phase samples of HNO3 in O2 and N2 were analyzed by long-path ultraviolet/visible (UV/VIS) spectroscopy to reveal the presence of both NO2 and NO3, the concentrations of which were calculated using differential absorption cross sections. NO2 is produced predominantly by the heterogeneous decomposition of HNO3, whereas NO3 is generated in the gas phase by the thermal decomposition of N2O5, a product of the self-disproportionation of liquid HNO3. © 1993 John Wiley & Sons, Inc.  相似文献   
124.
125.
It is shown that the exact solution of the problem of convective heat exchange in a low-Prandtl-number fluid flow (Pr ? 1) can be obtained for a two-dimensional body of arbitrary shape provided that the conformal mapping relating the body contour with a circle is known. By way of example, the Joukowsky airfoil is considered.  相似文献   
126.
A class of Hamiltonian dynamic systems integrated by the variable separation method is considered. The integration for this class is the inversion of an Abel mapping on hyperelliptic curves. We prove that the derivative of the Abel mapping is the Stäckel matrix, which determines a diagonal Riemannian metric and curvilinear orthogonal coordinate systems in a flat space. Lax representations with the spectral parameter are constructed. The corresponding classicalr-matrices are dynamic. It is shown how the class of pointwise canonical transformations can be naturally generalized using the Abel integral reduction theory.  相似文献   
127.
A model kinetic equation is constructed for the transport of a massless Bose gas. This equation is applied to solve the boundary value problem for the transport of radiation in the half-space occupied by a dispersive medium that is in local thermal equilibrium with the radiation. It is shown that the difference in temperature between the dispersive medium and the incident radiation substantially depends on the character of the scattering properties of the particles in the medium. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 111, No. 3, pp. 462–472, June, 1997.  相似文献   
128.
129.
The gauge compensation fields induced by the differential operators of the Stueckelberg-Schrödinger equation are discussed, as well as the relation between these fields and the standard Maxwell fields; An action is constructed and the second quantization of the fields carried out using a constraint procedure. The properties of the second quantized matter fields are discussed.  相似文献   
130.
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