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   87386篇
  免费   669篇
  国内免费   377篇
化学   30213篇
晶体学   882篇
力学   7047篇
数学   33586篇
物理学   16704篇
  2023年   65篇
  2022年   93篇
  2021年   129篇
  2020年   197篇
  2019年   200篇
  2018年   10631篇
  2017年   10426篇
  2016年   6394篇
  2015年   1156篇
  2014年   665篇
  2013年   1173篇
  2012年   4403篇
  2011年   11136篇
  2010年   6026篇
  2009年   6334篇
  2008年   7171篇
  2007年   9284篇
  2006年   748篇
  2005年   1840篇
  2004年   1941篇
  2003年   2318篇
  2002年   1281篇
  2001年   358篇
  2000年   390篇
  1999年   243篇
  1998年   264篇
  1997年   203篇
  1996年   279篇
  1995年   177篇
  1994年   126篇
  1993年   145篇
  1992年   99篇
  1991年   98篇
  1990年   80篇
  1989年   98篇
  1988年   82篇
  1987年   91篇
  1986年   84篇
  1985年   118篇
  1984年   101篇
  1983年   71篇
  1982年   102篇
  1981年   96篇
  1980年   107篇
  1979年   100篇
  1978年   81篇
  1977年   62篇
  1976年   81篇
  1975年   63篇
  1973年   64篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
This work studies the Soret and Dufour effects on the double-diffusive free convection over a downward-pointing vertical truncated cone with variable wall heat and mass fluxes in fluid-saturated porous media. A coordinate transformation is used to derive the nondimensional boundary-layer governing equations, and the obtained nonsimilar equations are then solved by the cubic spline collocation method. Results for local surface temperature and the local surface concentration are presented as functions of Soret parameters, Dufour parameters, power-law exponents, buoyancy ratios, and Lewis numbers. Results show that increasing the Dufour parameter tends to increase the local surface temperature, while it tends to decrease the local surface concentration. An increase in the Soret number leads to a decrease in the local surface temperature for buoyancy assisting flows, while it leads to an increase in the local surface temperature for buoyancy opposing flows. Increasing the Soret number tends to increase the local surface concentration. Moreover, the local surface temperature and the local surface concentration of the truncated cones with higher power-law exponents are lower than those with lower exponents.  相似文献   
92.
The effects of temperature-dependent viscosity, gravity modulation and thermo-mechanical anisotropies on heat transport in a low-porosity medium are studied using the Ginzburg–Landau model. The effect of gravity modulation is to decrease the Nusselt number, Nu and variable viscosity leads to increase in Nu. The thermo-mechanical anisotropies have opposite effect on Nu with thermal anisotropy decreasing the heat transport.  相似文献   
93.
The solution of cylindrical problems is addressed. A series solution is considered of the biharmonic equation, in which the series terms of the stress function Φ are expressions based upon Legendre polynomials and logarithmically singular functions. An explicit form of a polynomial supplementing each logarithmically singular part of the series solution is obtained.  相似文献   
94.
We consider the flow of a viscous incompressible fluid in a pipe when the boundary is a deformable shell of Naghdi type. We prove that the corresponding system of partial differential equations has a solution when the deformation of the shell is smooth and small enough. We propose an algorithm that uncouples the unknowns and prove its convergence.  相似文献   
95.
We apply the recently improved version of the 0–1 test for chaos to real experimental time series of laser droplet generation process. In particular two marginal regimes of dripping are considered: spontaneous and forced dripping. The outcomes of the test reveal that both spontaneous and forced dripping time series can be characterized as chaotic, which coincides with the previous analysis based on nonlinear time series analysis.  相似文献   
96.
97.
98.
99.
We report on two sensitive tests of lepton universality carried out by the 4 LEP experiments at the Z0 pole. From measurements of the τ polarization in e+ e?τ + τ ?, the ratios of the vector and axial vector coupling constants of the electron and the tau lepton to the weak neutral current are obtained to beg v e /g a e =0.066±0.015 andg V τ /g A τ =0.070±0.009 respectively. From measurement of the τ lifetime and the τ leptonic branching ratios, the ratio of the coupling constants describing weak leptonic decays of the τ and the μ is measured to beG τ /G μ =0.996±0.008.  相似文献   
100.
Pran Nath  R Arnowitt 《Pramana》1993,41(1):283-301
A review is given of the StandardSU(5) supergravity model. This model has passed an important check regarding unification of the electro-weak and the strong couplings using high precision LEP data. It is shown that for a significant domain of the parameter space the model also satisfies constraints on the SUSY spectrum from CDF and LEP, as well as proton stability and cosmological relic density constraints.  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