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   1160篇
  免费   14篇
  国内免费   8篇
化学   850篇
晶体学   10篇
力学   9篇
数学   67篇
物理学   246篇
  2022年   6篇
  2021年   8篇
  2020年   8篇
  2019年   11篇
  2018年   13篇
  2016年   12篇
  2015年   12篇
  2014年   17篇
  2013年   36篇
  2012年   46篇
  2011年   47篇
  2010年   32篇
  2009年   30篇
  2008年   54篇
  2007年   51篇
  2006年   67篇
  2005年   63篇
  2004年   50篇
  2003年   50篇
  2002年   36篇
  2001年   20篇
  2000年   19篇
  1999年   8篇
  1998年   24篇
  1997年   14篇
  1996年   15篇
  1995年   16篇
  1994年   10篇
  1993年   9篇
  1992年   18篇
  1991年   20篇
  1990年   10篇
  1989年   9篇
  1988年   14篇
  1987年   10篇
  1986年   22篇
  1985年   33篇
  1984年   28篇
  1983年   15篇
  1982年   18篇
  1981年   21篇
  1980年   31篇
  1979年   24篇
  1978年   18篇
  1977年   11篇
  1976年   10篇
  1975年   10篇
  1974年   18篇
  1973年   10篇
  1964年   6篇
排序方式: 共有1182条查询结果,搜索用时 250 毫秒
991.
992.
993.
The electrostatic potential in a gravitational field is estimated up to the order ofe 2 G 2 in the framework of the conventional quantum field theory. It is shown that the electrostatic potential is different from the classical one. We find that this discrepancy is attributable to the process in which a particle emits three massless ones which are absorbed by three other particles.  相似文献   
994.
995.
Pyrimido[5,4-g]pteridine N-oxide (1) oxidizes efficiently benzene, toluene, and anisole under UV irradiation to give the corresponding phenol derivatives 4, though the easiness of the reaction significantly depends upon the nature of the substituents on the benzene ring.  相似文献   
996.
The quadratic force constants of the five possible conformers of allylamine were calculated by an ab initio MC method. The infrared spectra of this molecule in the gas phase were remeasured and analyzed on the basis of the calculated vibrational frequencies. A potential energy surface with respect to the skeletal torsions was also calculated. The relative abundances of the S+G+, ST, CT, CG, and S+G? conformers, predicted to be 44:32:16:7:1 at room temperature, are consistent with the experimental data.  相似文献   
997.
998.
Unequal intensities of the Λ-doublet components were observed in the CH(A2Δ-X2Π) emission following the multiphoton dissociation of (CH3)2CO, (CH3)2S and CH3NO2 by an ArF laser (193 nm). The power dependence of the emission intensity was estimated to be cubic (3.1±0.2) when the laser power was below ≈ 8×1017 photons cm?2 pulse?1. The Λ-doublet populations depended on the rotational quantum number N′ and the preferred level changed at N′ = 20. A similar behavior was observed for the CD(A2Δ) from (CD3)2CO. Rotational distributions show bimodal behavior, having a hump around N′ = 13 in CH(A2Δ) and N′ = 11 in CD(A2Δ). These trends indicate that the CH(A2Δ) is produced through multiple processes where stepwise mechanisms are operative via either CH2 or CH3, or both radicals as intermediates.  相似文献   
999.
The function of a hologram computer-aided design tool which the authors have developed are extended to handle both designing and analyzing holograms illuminated by a two or three-dimensional white-light image. The ability to search for an optimum image plane is also now possible. HOE lenses illuminated by multiple point-sources and by a point-source with a certain spectral bandwidth are designed and analyzed using the extended functions. Accuracy and usefulness of the functions are demonstrated from the results of the design and analysis.  相似文献   
1000.
The infrared absorption of poly(ethylene glycol) was measured in the molten state. Characteristic bands of the molten state were identified. Normal vibrations and frequency distributions were treated for various conformation models with CH2CH2O repeat units. The infrared absorption peaks of the molten state closely correspond to the frequency distribution peaks of the TGT conformation with gauche O? CH2? CH2? O groups, although infrared bands due to trans O? CH2? CH2? O groups are also observed. Vibrational assignments of the infrared bands and Raman lines were made on the basis of potential energy distributions.  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