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   1811篇
  免费   68篇
  国内免费   5篇
化学   1235篇
晶体学   8篇
力学   27篇
数学   152篇
物理学   462篇
  2023年   12篇
  2022年   42篇
  2021年   44篇
  2020年   33篇
  2019年   24篇
  2018年   19篇
  2017年   20篇
  2016年   55篇
  2015年   46篇
  2014年   46篇
  2013年   96篇
  2012年   88篇
  2011年   120篇
  2010年   76篇
  2009年   65篇
  2008年   121篇
  2007年   114篇
  2006年   112篇
  2005年   98篇
  2004年   63篇
  2003年   51篇
  2002年   52篇
  2001年   23篇
  2000年   29篇
  1999年   22篇
  1998年   20篇
  1997年   24篇
  1996年   30篇
  1995年   14篇
  1994年   23篇
  1993年   17篇
  1992年   25篇
  1991年   20篇
  1990年   22篇
  1989年   21篇
  1988年   19篇
  1987年   20篇
  1986年   15篇
  1985年   18篇
  1984年   18篇
  1983年   8篇
  1982年   14篇
  1981年   11篇
  1979年   6篇
  1978年   8篇
  1977年   12篇
  1976年   5篇
  1975年   5篇
  1974年   5篇
  1973年   5篇
排序方式: 共有1884条查询结果,搜索用时 15 毫秒
81.
82.
Samples obtained as a result of the valleriite synthesis process under different conditions (temperature and proportion Cu:Fe:Mg in the initial mixture) were investigated by 57Fe M?ssbauer spectroscopy with attraction data of X-ray diffraction. Parameters of hyperfine interactions for valleriite were determined and crystal chemical identification of 57Fe subspectra was carried out. It was found that valleriite was formed in samples synthesized at 150°C and 180°C and not formed in samples synthesized at 250°C.  相似文献   
83.
84.
Abstract

Bola-amphiphiles having two aza-18-crown-6 ether rings attached by a covalent spacer (O—O) and an analogous tris (macrocycle) (O—O—O) have been prepared and their cation complexation behavior has been assessed by fast atom bombardment and collisionally activated dissociation tandem mass spectrometry; the key finding is that two cations may simultaneously be complexed by a two- or three-crown system and that this complexation may also involve an anion.  相似文献   
85.
The multicomponent assembly of pharmaceutically relevant N‐aryl‐oxazolidinones through the direct insertion of carbon dioxide into readily available anilines and dibromoalkanes is described. The addition of catalytic amounts of an organosuperbase such as Barton's base enables this transformation to proceed with high yields and exquisite substrate functional‐group tolerance under ambient CO2 pressure and mild temperature. This report also provides the first proof‐of‐principle for the single‐operation synthesis of elusive seven‐membered ring cyclic urethanes.  相似文献   
86.
87.
Integrative sol–gel chemistry based strategies allow, through the strong coupling between materials chemistry and advanced processing, the fabrication of functional inorganic and hybrid materials. The following article will highlight some of the main accomplishments performed during the last years in the design of nano- and multi-scale structured materials shaped as thin films, powders and monoliths with additional functionalities and outstanding properties in several fields of application such as optics, catalysis and nanomedicine. In particular we discuss the key role played by the adapted liquid processing of sol–gel based solution. We will describe some technologies (including dip coating, spray drying, droplet-microfluidics, ink-jet and foaming) in which a high degree of control in term of liquid shaping/evaporation/manipulation is required in order to achieve specific functionalities.  相似文献   
88.
89.
90.
This study describes our development of a microfluidic reaction scheme for the synthesis of fused indoline ring systems found in several bioactive compounds. We have utilized a continuous-flow microfluidic reactor for the reaction of hydrazines with latent aldehydes through the interrupted Fischer indolization reaction to form fused indoline and azaindoline products. We have identified optimal conditions and evaluated the scope of this microfluidic reaction using various hydrazine and latent aldehyde surrogates. This green chemistry approach can be of general utility to rapidly produce indoline scaffolds and intermediates in a continuous manner.  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