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   265521篇
  免费   3039篇
  国内免费   814篇
化学   135503篇
晶体学   4149篇
力学   11450篇
综合类   1篇
数学   31194篇
物理学   87077篇
  2020年   2214篇
  2019年   2333篇
  2018年   3091篇
  2017年   3020篇
  2016年   4781篇
  2015年   3129篇
  2014年   4805篇
  2013年   11885篇
  2012年   8923篇
  2011年   11078篇
  2010年   7559篇
  2009年   7350篇
  2008年   10326篇
  2007年   10273篇
  2006年   9650篇
  2005年   8700篇
  2004年   7862篇
  2003年   6894篇
  2002年   6808篇
  2001年   7661篇
  2000年   5899篇
  1999年   4617篇
  1998年   3891篇
  1997年   3801篇
  1996年   3733篇
  1995年   3394篇
  1994年   3368篇
  1993年   3535篇
  1992年   3545篇
  1991年   3624篇
  1990年   3397篇
  1989年   3301篇
  1988年   3350篇
  1987年   3230篇
  1986年   3048篇
  1985年   4216篇
  1984年   4401篇
  1983年   3555篇
  1982年   3762篇
  1981年   3697篇
  1980年   3574篇
  1979年   3638篇
  1978年   3768篇
  1977年   3673篇
  1976年   3722篇
  1975年   3408篇
  1974年   3411篇
  1973年   3454篇
  1972年   2352篇
  1971年   1970篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
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   
53.
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   
54.
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   
55.
Modeling and numerical simulations of the convective flows induced by the vibration of the monocrystal during crystal growth have been performed for two configurations simulating the Cz and FZ methods. This permitted to emphasize the role of different vibrational mechanisms in the formation of the average flows. It is shown that an appropriate combination of these mechanisms can be used to counteract the usual convective flows (buoyancy- and/or thermocapillary-driven) inherent to crystal growth processes from the liquid phase. While vibrational convection is rather complex due to these identified mechanisms, the new modeling used in the present paper opens up very promising perspectives to efficiently control heat and mass transfer during real industrial applications of crystal growth from the liquid phase.  相似文献   
56.
57.
58.
The relationship between the complex dielectric permittivity tensor of a polar nematic liquid crystal and the autocorrelation matrix for the permanent dipole moment of a molecule is obtained. The theory is applicable to the whole frequency range which characterizes orientational relaxation in liquid crystals (up to ∼ 5 THz). The models of rotational diffusion and extended rotational diffusion in a mean field nematic potential are used to evaluate the dielectric absorption and dispersion in nematics.  相似文献   
59.
60.
We report on the shape transition from InAs quantum dashes to quantum dots (QDs) on lattice-matched GaInAsP on InP(3 1 1)A substrates. InAs quantum dashes develop during chemical-beam epitaxy of 3.2 monolayers InAs, which transform into round InAs QDs by introducing a growth interruption without arsenic flux after InAs deposition. The shape transition is solely attributed to surface properties, i.e., increase of the surface energy and symmetry under arsenic deficient conditions. The round QD shape is maintained during subsequent GaInAsP overgrowth because the reversed shape transition from dot to dash is kinetically hindered by the decreased ad-atom diffusion under arsenic flux.  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