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   1318786篇
  免费   29602篇
  国内免费   7676篇
化学   654736篇
晶体学   20212篇
力学   74357篇
综合类   104篇
数学   240030篇
物理学   366625篇
  2021年   13461篇
  2020年   15895篇
  2019年   16045篇
  2018年   12297篇
  2016年   27681篇
  2015年   20711篇
  2014年   30363篇
  2013年   74204篇
  2012年   36890篇
  2011年   33071篇
  2010年   36374篇
  2009年   38856篇
  2008年   32573篇
  2007年   28095篇
  2006年   34848篇
  2005年   26978篇
  2004年   28821篇
  2003年   27407篇
  2002年   28507篇
  2001年   27405篇
  2000年   24163篇
  1999年   22204篇
  1998年   20901篇
  1997年   20894篇
  1996年   21046篇
  1995年   19126篇
  1994年   18538篇
  1993年   18101篇
  1992年   17907篇
  1991年   18258篇
  1990年   17445篇
  1989年   17510篇
  1988年   17074篇
  1987年   17063篇
  1986年   15967篇
  1985年   22418篇
  1984年   23685篇
  1983年   19904篇
  1982年   21614篇
  1981年   20840篇
  1980年   20185篇
  1979年   20302篇
  1978年   21638篇
  1977年   21221篇
  1976年   20946篇
  1975年   19646篇
  1974年   19280篇
  1973年   19768篇
  1972年   14277篇
  1967年   12456篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We develop an approach to the solution of the spinless Bethe-Salpeter equation for the different-mass case. Although the calculations are developed for spinzero particles in any arbitratry spherically symmetric potential, the non-Coulombic effective power-law potential is used as a kernel to produce the spin-averaged bound states of the non-self-conjugate mesons. The analytical formulas are also applicable to the self-conjugate mesons in the equal-mass case. The flavor-independent case is investigated in this work. The calculations are carried out to the third-order correction of the energy series. Results are consistent with those obtained before.  相似文献   
992.
993.
We describe a semi-analytical numerical method for coherent isotropic scattering time-dependent radiative transfer problems in slab geometry. This numerical method is based on a combination of two classes of numerical methods: the spectral methods and the Laplace transform (LTSN) methods applied to the radiative transfer equation in the discrete ordinates (SN) formulation. The basic idea is to use the essence of the spectral methods and expand the intensity of radiation in a truncated series of Laguerre polynomials in the time variable and then solve recursively the resulting set of “time-independent” SN problems by using the LTSN method. We show some numerical experiments for a typical model problem.  相似文献   
994.
The electrical conductivity of hydrosols of ultradispersed diamonds was studied. The electromembrane method for cleaning and concentrating of ultradispersed diamonds in hydrosols was considered. The influence exerted by the concentration of the dispersed phase on the electrical characteristics of the cleaning process was analyzed. A mathematical relation making it possible to evaluate the output characteristics of the process and to determine the geometrical characteristics of the apparatus was proposed.  相似文献   
995.
We investigate the replica symmetry breaking (RSB) in a neighborhood of the instability point of the replica-symmetric solution in the axial quadrupolar glass model. We show that the solution with the first-stage RSB is stable against the subsequent RSB. Although there is no reflection symmetry, the first-stage RSB solution continuously bifurcates from the replica-symmetric one. This implies that our model does not belong to either of the two classes into which spin glasses are usually divided.  相似文献   
996.
An approximate model of a spacetime foam is presented. It is supposed that in the spacetime foam each quantum handle is like to an electric dipole and therefore the spacetime foam is similar to a dielectric. If we neglect of linear sizes of the quantum handle then it can be described with an operator containing a Grassman number and either a scalar or a spinor field. For both fields the Lagrangian is presented. For the scalar field it is the dilaton gravity + electrodynamics and the dilaton field is a dielectric permeability. The spherically symmetric solution in this case give us the screening of a bare electric charge surrounded by a polarized spacetime foam and the energy of the electric field becomes finite one. In the case of the spinor field the spherically symmetric solution give us a ball of the polarized spacetime foam filled with the confined electric field. It is shown that the full energy of the electric field in the ball can be very big.  相似文献   
997.
998.
The stress–strain state of rectangular plates with a variable thickness and constant weight is analyzed. The laws of variation in the thickness are specified to depend on parameters so that the plate weight remains constant for any of their values. To solve the problem, discrete Fourier series are used, which makes it possible to reduce a two-dimensional problem to one-dimensional. Calculation results are presented.  相似文献   
999.
The microhardness and content of carbon in electroplated gold coatings were studied as influenced by the operation time of citrate and citrate-phosphate gold-plating electrolytes. Such physicomechanical properties as porosity, microhardness, internal stress, plasticity, and microstructure of electroless-plated and electroplated nickel coatings were studied and analyzed.  相似文献   
1000.
We consider the inverse problem for the identification of the coefficient in a parabolic equation. The model is applied to describe the functioning of a hierarchical structure [1]; it is also relevant for heat-conduction theory [2]. Unique solvability of the inverse problem is proved.  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