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   351篇
  免费   4篇
化学   239篇
晶体学   1篇
力学   4篇
数学   19篇
物理学   92篇
  2023年   1篇
  2022年   2篇
  2021年   6篇
  2020年   2篇
  2019年   6篇
  2018年   3篇
  2017年   3篇
  2016年   5篇
  2015年   3篇
  2014年   3篇
  2013年   16篇
  2012年   14篇
  2011年   23篇
  2010年   12篇
  2009年   10篇
  2008年   20篇
  2007年   27篇
  2006年   28篇
  2005年   19篇
  2004年   27篇
  2003年   23篇
  2002年   11篇
  2001年   9篇
  2000年   6篇
  1999年   9篇
  1998年   4篇
  1996年   5篇
  1995年   4篇
  1994年   7篇
  1993年   1篇
  1992年   2篇
  1991年   2篇
  1990年   6篇
  1989年   2篇
  1988年   2篇
  1987年   3篇
  1986年   3篇
  1985年   3篇
  1984年   3篇
  1983年   1篇
  1982年   3篇
  1981年   2篇
  1980年   4篇
  1979年   5篇
  1978年   3篇
  1977年   1篇
  1975年   1篇
排序方式: 共有355条查询结果,搜索用时 15 毫秒
1.
The motion of a moored floating body under the action of wave forces, which is influenced by fluid forces, shape of the floating body and mooring forces, should be analysed as a complex coupled motion system. Especially under severe storm conditions or resonant motion of the floating body it is necessary to consider finite amplitude motions of the waves, the floating body and the mooring lines as well as non-linear interactions of these finite amplitude motions. The problem of a floating body has been studied on the basis of linear wave theory by many researchers. However, the finite amplitude motion under a correlated motion system has rarely been taken into account. This paper presents a numerical method for calculating the finite amplitude motion when a floating body is moored by non-linear mooring lines such as chains and cables under severe storm conditions.  相似文献   
2.
3.
Normal state conductivity and superconductivity together with bulk magnetic susceptibility and magnetization measurements have been measured for two molecular charge-transfer salts: beta' '-(ET)4[(H3O)Ga(C2O4)3]G (ET = bis(ethylenedithio)tetrathiafulvalene, G = pyridine for compound I and nitrobenzene for compound II). With the exception of the included guest molecules (G) the crystal structures are almost identical. Both show minima in their electrical transport at 130 K for I and at 160 K for II, but at lower temperatures their behaviors differ markedly. The resistance of I reaches a maximum at 50 K with a further small peak at 2 K and possible superconductivity only below 2 K, whereas that of II increases continuously down to 7.5 K, where an abrupt transition to a superconducting state occurs.  相似文献   
4.
Nanocomposites consisting of conducting polyaniline and clay minerals were successfully synthesized from mechanochemically intercalated anilinium fluoride; the nanocomposites prepared by the mechanochemical intercalation method contained much more polyaniline in the clay layers than those prepared by a conventional solution method.  相似文献   
5.
Glutamate synthesis by reductive amination of 2-oxoglutarate was performed by the combination of NADH regeneration system and glutamate dehydrogenase (GluDH). The conversion of 2-oxoglutamate to glutamate was 98% after 3 h, and the turnover number of NAD+was 17.  相似文献   
6.
The density functional theory was employed to investigate Eu(III) complexes with three beta-diketonates and two phosphine oxides (complex M1: Eu(bdk)3(TPPO)2, complex M2: Eu(bdk)3(TMPO)2, and complex M3: Eu(bdk)3(TPPO)(TMPO)) deemed to be the model complexes of the fluorescence compounds for the ultraviolet LED devices we have recently developed. For each complex, two minimum energy points corresponding to two different optimized geometries (structures A and B) have been found, and the difference of the energy between two minimum energy points is found to be quite small (less than 1 kcal/mol). Vertical excitation energies and oscillator strengths for each complex at two optimized geometries have been obtained by the time-dependent density functional theory, and the character of the excited states has been investigated. For complex M3, the absorption edge is red-shifted, and the oscillator strengths are relatively large. The efficiency of intersystem crossing and energy transfer from the triplet excited state to the Eu(III) ion is considered by calculating DeltaE(ISC) (the energy difference between the first singlet excited state and the first triplet excited state) and DeltaE(ET) (the difference between the excitation energy of the complex for the first triplet excited state and the emission energy of the Eu(III) ion for 5D to 7F).  相似文献   
7.
8.
Alanine synthesis by reductive amination of pyruvate was performed by the combination of NADH regeneration system and alanine dehydrogenase (AlaDH). The conversion of pyruvate to alanine was 99% after 1 h. Leucine synthesis was also carried out by the combination of NADH regeneration system and leucine dehydrogenase (LeuDH). The conversion of 4-methyl-2-oxovalerate to leucine was 60% after 1.5 h.  相似文献   
9.
Three conducting BEDT-TTF charge-transfer salts with tris(oxalato)metallate anions have unit cells containing both[small alpha] and [small beta][double prime] donor packing motifs.  相似文献   
10.
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