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   2770篇
  免费   38篇
  国内免费   6篇
化学   1974篇
晶体学   8篇
力学   44篇
综合类   1篇
数学   460篇
物理学   327篇
  2016年   32篇
  2015年   30篇
  2014年   34篇
  2013年   98篇
  2012年   76篇
  2011年   71篇
  2010年   49篇
  2009年   46篇
  2008年   76篇
  2007年   93篇
  2006年   72篇
  2005年   69篇
  2004年   58篇
  2003年   62篇
  2002年   49篇
  2001年   28篇
  2000年   26篇
  1999年   28篇
  1998年   25篇
  1997年   30篇
  1996年   25篇
  1995年   27篇
  1994年   42篇
  1993年   29篇
  1992年   20篇
  1991年   30篇
  1990年   29篇
  1989年   36篇
  1988年   31篇
  1987年   37篇
  1986年   31篇
  1985年   48篇
  1984年   56篇
  1983年   26篇
  1982年   52篇
  1981年   49篇
  1980年   41篇
  1979年   36篇
  1978年   62篇
  1977年   61篇
  1976年   43篇
  1975年   38篇
  1974年   34篇
  1973年   46篇
  1972年   30篇
  1971年   46篇
  1970年   30篇
  1969年   20篇
  1966年   24篇
  1923年   18篇
排序方式: 共有2814条查询结果,搜索用时 140 毫秒
1.
Embedding endohdedral metallofullerenes (EMFs) into electron donor–acceptor systems is still a challenging task owing to their limited quantities and their still largely unexplored chemical properties. In this study, we have performed a 1,3‐dipolar cycloaddition reaction of a corrole‐based precursor with Sc3N@C80 to regioselectively form a [5,6]‐adduct ( 1 ). The successful attachment of the corrole moiety was confirmed by mass spectrometry. In the electronic ground state, absorption spectra suggest sizeable electronic communications between the electron acceptor and the electron donor. Moreover, the addition pattern occurring at a [5,6]‐bond junction is firmly proven by NMR spectroscopy and electrochemical investigations performed with 1 . In the electronically excited state, which is probed in photophysical assays with 1 , a fast electron‐transfer yields the radical ion pair state consisting of the one‐electron‐reduced Sc3N@C80 and of the one‐electron‐oxidized corrole upon its exclusive photoexcitation. As such, our results shed new light on the practical work utilizing EMFs as building blocks in photovoltaics.  相似文献   
2.
Infrared (IR) spectroscopy of chemisorbed C60 on Ag (111), Au (110) and Cu (100) reveals that a non-IR-active mode becomes active upon adsorption, and that its frequency shifts proportionally with the charge transferred from the metal to the molecule by about 5 cm-1 per electron. The temperature dependence of the frequency and the width of this IR feature have also been followed for C60/Cu (100) and were found to agree well with a weak anharmonic coupling (dephasing) to a low-frequency mode, which we suggest to be the frustrated translational mode of the adsorbed molecules. Additionally, the adsorption is accompanied by a broadband reflectance change, which is interpreted as due to the scattering of conduction electrons of the metal surface by the adsorbate. The reflectance change allows determination of the friction coefficient of the C60 molecules, which results in rather small values (∼2×109 s-1 for Ag and Au, and ∼1.6×109 s-1for Cu), consistent with a marked metallic character of the adsorbed molecules. Pre-dosing of alkali atoms onto the metal substrates drastically changes the IR spectra recorded during subsequent C60 deposition: anti-absorption bands, as well as an increase of the broadband reflectance, occur and are interpreted as due to strong electron–phonon coupling with induced surface states. Received: 6 June 2001 / Accepted: 23 October 2001 / Published online: 3 April 2002  相似文献   
3.
4.
5.
6.
7.
8.
Sufficient conditions which guarantee that certain linear integro-differential equation cannot have a positive solution are established.  相似文献   
9.
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