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   1380611篇
  免费   29682篇
  国内免费   7809篇
化学   696639篇
晶体学   20474篇
力学   75684篇
综合类   106篇
数学   244411篇
物理学   380788篇
  2021年   13576篇
  2020年   15973篇
  2019年   16107篇
  2018年   14037篇
  2016年   28566篇
  2015年   20943篇
  2014年   30533篇
  2013年   74502篇
  2012年   40281篇
  2011年   39285篇
  2010年   38529篇
  2009年   40480篇
  2008年   37742篇
  2007年   33876篇
  2006年   38470篇
  2005年   31543篇
  2004年   32183篇
  2003年   29917篇
  2002年   30670篇
  2001年   30771篇
  2000年   26153篇
  1999年   23151篇
  1998年   21262篇
  1997年   21148篇
  1996年   21218篇
  1995年   19273篇
  1994年   18724篇
  1993年   18307篇
  1992年   18573篇
  1991年   18787篇
  1990年   18010篇
  1989年   18042篇
  1988年   17647篇
  1987年   17570篇
  1986年   16524篇
  1985年   22878篇
  1984年   23983篇
  1983年   20103篇
  1982年   21722篇
  1981年   20962篇
  1980年   20289篇
  1979年   20601篇
  1978年   21807篇
  1977年   21423篇
  1976年   21134篇
  1975年   19845篇
  1974年   19497篇
  1973年   19907篇
  1972年   14426篇
  1967年   12654篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Erosion and sediments transport processes have a great impact on industrial structures and on water quality. Despite its limitations, the Saint‐Venant‐Exner system is still (and for sure for some years) widely used in industrial codes to model the bedload sediment transport. In practice, its numerical resolution is mostly handled by a splitting technique that allows a weak coupling between hydraulic and morphodynamic distinct softwares but may suffer from important stability issues. In recent works, many authors proposed alternative methods based on a strong coupling that cure this problem but are not so trivial to implement in an industrial context. In this work, we then pursue 2 objectives. First, we propose a very simple scheme based on an approximate Riemann solver, respecting the strong coupling framework, and we demonstrate its stability and accuracy through a number of numerical test cases. However, second, we reinterpret our scheme as a splitting technique and we extend the purpose to propose what should be the minimal coupling that ensures the stability of the global numerical process in industrial codes, at least, when dealing with collocated finite volume method. The resulting splitting method is, up to our knowledge, the only one for which stability properties are fully demonstrated.  相似文献   
122.
123.
124.
125.
126.
In this study, the functional interaction of HPLW peptide with VEGFR2 (Vascular Endothelial Growth Factor Receptor 2) was determined by using fast 15N‐edited NMR spectroscopic experiments. To this aim, 15N uniformly labelled HPLW has been added to Porcine Aortic Endothelial Cells. The acquisition of isotope‐edited NMR spectroscopic experiments, including 15N relaxation measurements, allowed a precise characterization of the in‐cell HPLW epitope recognized by VEGFR2.  相似文献   
127.
128.
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   
129.
130.
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