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   390篇
  免费   9篇
  国内免费   2篇
化学   240篇
力学   19篇
数学   38篇
物理学   104篇
  2022年   4篇
  2021年   18篇
  2020年   14篇
  2019年   20篇
  2018年   20篇
  2017年   15篇
  2016年   13篇
  2015年   16篇
  2014年   22篇
  2013年   64篇
  2012年   34篇
  2011年   32篇
  2010年   16篇
  2009年   16篇
  2008年   17篇
  2007年   14篇
  2006年   6篇
  2005年   7篇
  2004年   10篇
  2003年   7篇
  2002年   9篇
  2001年   8篇
  1999年   2篇
  1998年   1篇
  1997年   2篇
  1993年   1篇
  1992年   1篇
  1990年   1篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1983年   2篇
  1982年   1篇
  1978年   1篇
  1975年   1篇
  1936年   1篇
排序方式: 共有401条查询结果,搜索用时 500 毫秒
1.
2.
3.
This article describes our recent methods for the synthesis of substituted vinylphosphonates by reacting 1-alkynylphosphnates with group (IV) complexes. cis-Vinylphosphonates, 1,3-butadienylphosphonates, 1-(hydroxymethyl)vinylphosphonates, 2-(hydroxymethyl)vinylphosphonates, (E) 3-oxo-1-alkenylphosphonates were produced as a result of the reactions between zirconium complexes and 1-alkynylphosphonates. On the other hand, titanium complexes afford 3-aminovinylphoshonates, 1,4-bis-phosphonates, and various other di- and tri-substituted vinylphosphonates. An evaluation of access of these recently synthesized vinylphosphonates as MMP-2 inhibitors has shown that certain compounds are very potent and promising.  相似文献   
4.
5.
Abstract

This review reports the developed methods for the synthesis of polyfunctional 1,2,4-triazine systems bearing and/or containing phosphorus atoms as donor-acceptors interactions. Most of the synthetic methods depend on the interaction between an amino group of the side chain of 1,2,4-triazine with phosphorus reagents. The biological activities, i.e. their biocidal affects as antioxidants, antimicrobials, anti-inflammatory as well as molluscicidal agents against some snails are discussed.  相似文献   
6.
Single crystals of Sr4Mn2.09Cu0.91O9 have been grown by flux synthesis and the structure, closely related to the hexagonal perovskite 2H, was solved from single‐crystal X‐ray data in space group P321. The structure of Sr4Mn2CuO9 is composed of chains of face‐sharing polyhedra with a sequence of two octahedra and one trigonal prism. The octahedra are filled by Mn atoms and the Cu atoms are randomly distributed at the centres of the square faces of the trigonal prism. A stacking fault is observed within one of the two chains, which can be attributed to a shifting of the chain along the c axis.  相似文献   
7.
A number of aldehydes and ketones were prepared by oxidation of alcohol by N,N‐dichloro‐4‐methylbenzenesulfonamide under mild and neutral conditions in good to high yield in dichloromethane at room temperature.  相似文献   
8.
9.
[structure: see text] Alpha-phosphonozirconacyclopentenes or alpha-borylzirconacyclopentenes react by bromination, iodination, allylation, and propargylation to generate unique vinyl boronates and vinyl phosphonates not obtainable by other methods. The reaction proceeds in two steps, with both high regio- and stereoselectivity. With the vinyl boronates, the Zr-Csp2 bond is initially cleaved by 1 equiv of electrophile. With the phosphonates, either the Zr-Csp2 bond (allyl bromide, Br(2)) or the Zr-Csp3 bond (I(2), propargyl bromide) may be initially cleaved. The addition of a second equivalent of an electrophile results in disubstitution.  相似文献   
10.
A. Rostami  M. Noori  S. Matloub 《Optik》2013,124(24):6582-6585
In this paper, our main attempt was to reduce Total Internal Reflection (TIR) happening at Indium Tin Oxide (ITO, nito = 1.8 + 0.01i) and Glass (nglass = 1.51) interface, which is due to ITO's higher index in comparison with Glass's, that makes light guided in ITO layer, 50% of generated light in Wight Organic Light Emitting Diodes (WOLED) are trapped in ITO layer; here we tried to reduce this portion of trapped light by implying 12-fold quasi-photonic crystal to the mentioned interface. With some gentle changes in 12-fold's structure we could reduce TIR in this interface to less than 9%. Also, far field results before and after adding the structure to WOLED were studied, which represents suitability of using this structure for lighting applications.  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