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   1326篇
  免费   40篇
  国内免费   2篇
化学   1033篇
晶体学   13篇
力学   23篇
数学   36篇
物理学   263篇
  2023年   10篇
  2021年   11篇
  2020年   19篇
  2019年   16篇
  2018年   12篇
  2017年   11篇
  2016年   24篇
  2015年   31篇
  2014年   39篇
  2013年   54篇
  2012年   79篇
  2011年   90篇
  2010年   43篇
  2009年   40篇
  2008年   93篇
  2007年   61篇
  2006年   69篇
  2005年   57篇
  2004年   52篇
  2003年   41篇
  2002年   40篇
  2001年   33篇
  2000年   20篇
  1999年   12篇
  1998年   10篇
  1997年   6篇
  1996年   10篇
  1995年   8篇
  1994年   12篇
  1993年   17篇
  1992年   18篇
  1991年   21篇
  1990年   12篇
  1989年   12篇
  1988年   20篇
  1987年   29篇
  1986年   13篇
  1985年   25篇
  1984年   19篇
  1983年   11篇
  1982年   25篇
  1981年   20篇
  1980年   15篇
  1979年   16篇
  1978年   9篇
  1977年   16篇
  1976年   6篇
  1975年   10篇
  1974年   12篇
  1973年   7篇
排序方式: 共有1368条查询结果,搜索用时 984 毫秒
1.
We report the recent development on the SUSY calculations with the help of GRACE system. GRACE/SUSY/1LOOP is the computer code which can generate Feynman diagrams in the MSSM automatically and compute one-loop amplitudes in the numerical way. We present new results of various two-body decay widths and chargino pair production at ILC (international linear collider) at one-loop level.   相似文献   
2.
3.
The pentafluorobenzenethiyl radical is an efficient hydrogen abstractor from an activated methylene or methine group and bis(pentafluorophenyl) disulfide is an efficient electron acceptor from the resulting radical intermediate. Thus benzyl-OTBS ether was easily converted into the corresponding pinacol, and 2-phenyl-1,3-dioxanes are converted into the monobenzoates of diols.  相似文献   
4.
A new cyclobutene-fused 1,6-methano[10]annulene was synthesized by pyrolysis of the sulfone and sulfinate adducts of 3,4-bis(methylene)-1,6-methano[10]annulene and its physical and chemical properties were disclosed.  相似文献   
5.
Reactions of pyrrolidine with 2 equiv of aldehydes without any catalyst in a pressurized vessel at 140–200 °C yielded 1,3-disubstituted pyrroles. -Branched aldehydes gave fairly good yields of the corresponding products by this method, which provides a facile non-oxidative procedure for synthesizing 1,3-dialkylpyrroles from inexpensive pyrrolidine and aldehydes.  相似文献   
6.
Ciguatoxin C-CTX-1 was isolated as a principal causative toxin of ciguatera seafood poisoning in the Caribbean Sea, and is structurally classified as a ladder-shaped polycyclic ether. In this Letter, we report the synthesis of the tricyclic LMN-ring system of C-CTX-1. SmI2-mediated reductive cyclization efficiently constructed the seven-membered M-ring with the axially oriented 1,3-dimethyl structure.  相似文献   
7.
Three Pt-based catalysts prepared in different radiolytic conditions and supported on graphite powder were packed into a carbon paste electrode configuration. They were compared to each other, to the commercial (Pt) deposited on activated carbon powder (Johnson Matthey) and to pure Vulcan XC-72 for their respective abilities toward the hydrogen evolution reaction (HER). The Tafel parameters were determined for all these electrodes. From the I–V curves and their quantitative treatment, the following order of activity emerged unambiguously and reads: (PtCO)2 (fcc structure) > (PtCO)1 (Chini cluster) > (Pt)neat > (Pt)JM (Johnson Matthey) ≫ (Vulcan XC-72). As expected, all the Pt-loaded electrodes were more efficient than Vulcan XC-72. The classification appears to be linked with the mean nanoparticle size, and for comparable sizes, with the surface morphology of the materials. The results and the stability of the electrodes suggest that the small particle sizes and the good dispersity on the carbon support were maintained during the HER.  相似文献   
8.
9.
10.
The demetalation process of 10 multi-iron Wells-Dawson polyoxometalates is studied by cyclic voltammetry and controlled potential coulometry. Eight sandwich-type complexes (alphaalphaalphaalpha-Na(16)[(NaOH(2))(2)(Fe(III))(2)(X(2)W(15)O(56))(2)], alphaalphabetaalpha-Na(14)[(NaOH(2))(Fe(III)OH(2))(Fe(III))(2)(X(2)W(15)O(56))(2)], alphabetabetaalpha-Na(12)[(Fe(III)OH(2))(2)(Fe(III))(2)(X(2)W(15)O(56))(2)], and alphabetabetaalpha-Na(14)[(Mn(II)OH(2))(2)(Fe(III))(2)(X(2)W(15)O(56))(2)] (where X = P(V) or As(V))) and two monomeric complexes (alpha-Na(11)[(P(2)(Fe(III)Cl)(2)(Fe(III)OH(2))W(15)O(59))] and alpha-Na(11)[(As(2)(Fe(III)Cl)(2)Fe(III)OH(2))W(15)O(59))]) were selected for this study. All 10 complexes show Fe(III) waves which are well-separated from the redox activity of the W(VI) centers. At room temperature and under mild conditions, iron release from the complexes is observed upon reduction of the Fe(III) centers. This release is controlled by the ionic strength of the medium, the nature and concentration of the anions present in the supporting electrolyte, and by the pH of the solution. This behavior parallels those described for most siderophores which depend on the same parameters.  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