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   1411231篇
  免费   29778篇
  国内免费   7831篇
化学   717223篇
晶体学   20567篇
力学   76236篇
综合类   108篇
数学   246397篇
物理学   388309篇
  2021年   13611篇
  2020年   16001篇
  2019年   16139篇
  2018年   14390篇
  2016年   28826篇
  2015年   21046篇
  2014年   30621篇
  2013年   74738篇
  2012年   41715篇
  2011年   41587篇
  2010年   39213篇
  2009年   40918篇
  2008年   39728篇
  2007年   36187篇
  2006年   40279篇
  2005年   33482篇
  2004年   33816篇
  2003年   31214篇
  2002年   31841篇
  2001年   32744篇
  2000年   27385篇
  1999年   23734篇
  1998年   21539篇
  1997年   21374篇
  1996年   21339篇
  1995年   19362篇
  1994年   18834篇
  1993年   18420篇
  1992年   18978篇
  1991年   19133篇
  1990年   18391篇
  1989年   18384篇
  1988年   17984篇
  1987年   17867篇
  1986年   16860篇
  1985年   23190篇
  1984年   24215篇
  1983年   20260篇
  1982年   21823篇
  1981年   21066篇
  1980年   20385篇
  1979年   20847篇
  1978年   21946篇
  1977年   21642篇
  1976年   21375篇
  1975年   20126篇
  1974年   19777篇
  1973年   20192篇
  1972年   14691篇
  1967年   12917篇
排序方式: 共有10000条查询结果,搜索用时 0 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