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   819篇
  免费   30篇
  国内免费   21篇
化学   466篇
晶体学   4篇
力学   69篇
数学   166篇
物理学   165篇
  2023年   5篇
  2022年   22篇
  2021年   22篇
  2020年   30篇
  2019年   38篇
  2018年   35篇
  2017年   36篇
  2016年   57篇
  2015年   35篇
  2014年   59篇
  2013年   103篇
  2012年   63篇
  2011年   69篇
  2010年   59篇
  2009年   40篇
  2008年   36篇
  2007年   31篇
  2006年   23篇
  2005年   18篇
  2004年   13篇
  2003年   12篇
  2002年   11篇
  2001年   12篇
  2000年   2篇
  1998年   4篇
  1997年   1篇
  1996年   1篇
  1993年   1篇
  1992年   2篇
  1988年   2篇
  1987年   1篇
  1986年   2篇
  1985年   7篇
  1984年   5篇
  1983年   3篇
  1982年   1篇
  1979年   1篇
  1975年   1篇
  1974年   1篇
  1973年   2篇
  1972年   2篇
  1966年   1篇
  1955年   1篇
排序方式: 共有870条查询结果,搜索用时 15 毫秒
171.
In this paper, synthesis of two derivatives of noscapine and their application as organocatalysts in the asymmetric addition of diethylzinc to aromatic aldehydes is reported. The first catalyst (2) was synthesized by the reduction of lactone ring of noscapine to form the corresponding diol, and the second one (3) was prepared by tert-butyl dimethyl silylation of the primary hydroxyl group of 2. Excellent yields and high ees up to 95% were obtained by using 3 as the catalyst. To the best of our knowledge, this is the first report on the application of lactone ring opened noscapinoid compounds as organocatalysts in asymmetric reactions.  相似文献   
172.
STR analysis is commonly used in forensic and genetic studies. STRs are currently discriminated based on size, primarily by gel- and column-based approaches. Hybridization-based approaches have the potential to allow high-throughput analysis of STRs; however, development of such approaches has been limited by the difficulty in discriminating between STRs of similar length. We have recently described several innovations to enable STR analysis using an array-based hybridization approach for high- throughput STR analysis. Here we extend that approach by incorporating the array into microspheres and adding a discriminatory branch migration displacement step. This microsphere-based platform uses Luminex xMAP technology and improves the sensitivity, selectivity, and speed of the assay. We demonstrate the feasibility, speed, and reliability of the assay for STR detection by correctly analyzing two STR loci in 20 forensic DNA samples of known STR type. The multiplex, bead-based approach provides a high-throughput and more portable STR analysis.  相似文献   
173.
Ebrahimi D  Chow E  Gooding JJ  Hibbert DB 《The Analyst》2008,133(8):1090-1096
A peptide-modified electrode array with a different peptide on each electrode is compared with a single electrode modified with many peptides for the voltammetric measurement of concentrations of Cu(2+), Cd(2+) and Pb(2+) in solution. The single gold electrode was modified simultaneously with peptides Gly-Gly-His, glutathione and angiotensin I each coupled to thioctic acid, and thioctic acid itself, and the calibration of mixtures of ions was compared with previously published data from an array of four sensors each with an individual modification. Calibration at the multi-peptide single-electrode sensor was by two-way partial least squares (voltammetric current measured with variables 'sample' x 'potential') and for the electrode array by three-way NPLS1 ('sample' x 'potential' x 'electrode'). The advantage of designing experiments to yield multi-way data is demonstrated and discussed.  相似文献   
174.
Research on Chemical Intermediates - A novel series of 1,3-disubstituted 4-oxo-1,4-dihydroquinolines as antimicrobial agents were designed and synthesized. Their structures have been confirmed...  相似文献   
175.
176.
177.
We present two Penning trap experiments concerned with different aspects of the physics of extreme electromagnetic fields, the ARTEMIS experiment designed for bound-electron magnetic moment measurements in the presence of the extremely strong fields close to the nucleus of highly charged ions, and the HILITE experiment, in which well-defined ion targets are to be subjected to high-intensity laser fields.  相似文献   
178.
Poly(4-vinylpyridinium) perchlorate has been used as a supported,recyclable,environmentally-benign catalyst for the formation of acylals from aliphatic and aromatic aldehydes in good to excellent yields under solvent-free conditions.Notably,the reaction conditions were tolerant of ketones.This methodology offers several distinct advantages,including its operational simplicity and high product yield,as well as being green in terms of avoiding the use of toxic catalysts and solvents.Furthermore,the catalyst can be recovered and reused several times without any loss in its activity.  相似文献   
179.
180.
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