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   16747篇
  免费   2056篇
  国内免费   4810篇
化学   18652篇
晶体学   419篇
力学   485篇
综合类   161篇
数学   1670篇
物理学   2226篇
  2024年   9篇
  2023年   165篇
  2022年   192篇
  2021年   420篇
  2020年   619篇
  2019年   459篇
  2018年   488篇
  2017年   526篇
  2016年   702篇
  2015年   664篇
  2014年   911篇
  2013年   1453篇
  2012年   1709篇
  2011年   1034篇
  2010年   861篇
  2009年   1041篇
  2008年   1194篇
  2007年   1248篇
  2006年   1151篇
  2005年   1132篇
  2004年   1017篇
  2003年   942篇
  2002年   704篇
  2001年   574篇
  2000年   539篇
  1999年   518篇
  1998年   436篇
  1997年   422篇
  1996年   364篇
  1995年   377篇
  1994年   323篇
  1993年   229篇
  1992年   293篇
  1991年   208篇
  1990年   169篇
  1989年   123篇
  1988年   91篇
  1987年   65篇
  1986年   68篇
  1985年   53篇
  1984年   36篇
  1983年   19篇
  1982年   24篇
  1981年   10篇
  1980年   7篇
  1979年   3篇
  1978年   4篇
  1977年   5篇
  1972年   2篇
  1936年   2篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
41.
The problems involved in identifying and quantifying labile interactions considered to influence complex compound structures are highlighted through the assessment of four different families of metal complexes for which extensive crystallographic data are available. Modification of the charge distribution within a ligand molecule as a result of coordination is one factor with a number of ramifications. A detailed analysis of evidence for both intra- and inter-molecular attractions in dimethylsulfoxide complexes of metal perchlorates is used to provide a basis for the consideration of weak interactions between complex ions involving forces including phenyl-group attractions, hydrogen bonding and cavity inclusion.  相似文献   
42.
Introduction In the previous studies on the oxidation reaction,peroxydisulfate was widely used as an oxidizingagent.1-5 One of the advantages of this oxidant lies in itsstability in a wide range of pH values. The reaction be-tween Fe(CN)5L3- (L=N-aromatic heterocyclic li-gands) and S2O8 2- has been proved to proceed throughan outer-sphere electron transfer mechanism.5 For a re-action [(Eq. (1)] to be under an outer-sphere mechanismthe steps involved are the formation of a reactant …  相似文献   
43.
For the Na I2 collision system, theoretical study is performed on the QCISD(T) level by using ab initio method. The ab initio potential energy surfaces are got and on them the long-lived complexes are found and optimized. These results verify the crossed molecule beam experimental phenomenon and the detailed geometry structures are given for the first time. The role of the complexes in the reaction path is also described in detail.  相似文献   
44.
As photosensitizer for solar cell, a new ruthenium (Ⅱ) complex with four ester groups had been synthesized, in which a phenol substituted by {[(2-hydroxy-5-tert-butylbenzyl)(pyridyl-2-methyl)amino]methyl} is covalently linked to ruthenium (Ⅱ) tris-bipyridine. The structures of the new compounds were confirmed by NMR and ESI-MS spectra. The electrochemical and photochemical properties were also studied.  相似文献   
45.
Continuous dependence on a modelling parameter is established for solutions of a problem for a complex Ginzburg–Landau equation. A homogenizing boundary condition is also used to discuss the continuous dependence results. We derive a priori estimates that indicate that solutions depend continuously on a parameter in the governing differential equation. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
46.
The association of complex formation with static quenching in CT systems was investigated. Evaluation of the data made evident that the inner filter effect must be allowed for. Time-resolved and temperature-dependent stationary measurements of fluorescence led to the separation of dynamic and static quenching components. The static quenching constant is discussed with respect to the equilibrium constant of complex formation determined by absorption spectroscopy.  相似文献   
47.
Fullerene deuteride was obtained by the reaction of deuterium with solid palladium fulleride C60Pd4.9 under fairly mild conditions. The compound was identified by FD-MS, UV-Vis and IR spectroscopies, and TLC.Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 483–484, February, 1996  相似文献   
48.
The benefits of using nanoparticle-modified electrodes are exemplified through the electrochemical detection of protons and/or hydrogen. It is shown that a palladium-nanoparticle-modified boron-doped diamond allows voltammetric information relating to the relative roles played by the surface and the bulk metal to be obtained for the proton-hydrogen system at palladium surfaces which is not accessible using palladium macroelectrodes or microelectrodes.  相似文献   
49.
在可交换四元数空间中的双曲方程的特征边值问题   总被引:1,自引:0,他引:1  
杨丕文  李曼荔  杨硕 《数学学报》2007,50(6):1249-125
讨论了一阶和二阶双曲复方程的特征边值问题.对其中两种线性方程,分别在不同的情况下获得通解和可解条件.而对于拟线性的二阶双曲复方程,证明了解的存在性和唯一性.  相似文献   
50.
Palladium(II) complexes with N,N‐bis(diphenylphosphino)aniline ligands catalyse the Heck reaction between styrene and aryl bromides, affording stilbenes in good yield. The structures of two of the complexes used as pre‐catalysts have been determined by single‐crystal X‐ray diffraction. Copyright © 2007 John Wiley & Sons, Ltd.  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