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   517篇
  免费   13篇
  国内免费   1篇
化学   370篇
晶体学   2篇
力学   10篇
数学   62篇
物理学   87篇
  2022年   5篇
  2021年   15篇
  2020年   5篇
  2019年   7篇
  2018年   9篇
  2017年   5篇
  2016年   17篇
  2015年   14篇
  2014年   14篇
  2013年   22篇
  2012年   37篇
  2011年   31篇
  2010年   17篇
  2009年   16篇
  2008年   39篇
  2007年   31篇
  2006年   30篇
  2005年   22篇
  2004年   20篇
  2003年   14篇
  2002年   17篇
  2001年   12篇
  2000年   4篇
  1998年   6篇
  1996年   9篇
  1995年   3篇
  1994年   5篇
  1993年   4篇
  1992年   4篇
  1990年   7篇
  1989年   3篇
  1988年   7篇
  1987年   11篇
  1986年   5篇
  1985年   9篇
  1984年   3篇
  1983年   4篇
  1982年   4篇
  1980年   3篇
  1979年   4篇
  1978年   2篇
  1976年   2篇
  1975年   3篇
  1974年   4篇
  1972年   2篇
  1971年   2篇
  1968年   2篇
  1953年   2篇
  1907年   5篇
  1894年   2篇
排序方式: 共有531条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
5.
Oxime ethers prepared from (R)- or (S)-O-(1-phenylbutyl)hydroxylamine (ROPHy or SOPHy) are versatile intermediates for the asymmetric synthesis of a range of nitrogen containing compounds including simple amines, 1,2-aminoalcohols, alpha- and beta-amino acids, heterocyclic building blocks of natural products, piperidine alkaloids, lactams, 5- to 8-membered ring nitrogen heterocycles, imino-sugars, and chiral ferrocene based receptors.  相似文献   
6.
The room-temperature phosphorescence (r.t.p.) and fluorescence spectra of benzoquinoline isomers are investigated. The isomers can be resolved into the linear or angular subgroups on the basis of their fluorescence and r.t.p. spectra by using conventional fixed excitation. Second-derivative and synchronous scanning techniques can be combined to improve the selectivity of the r.t.p. and fluorescence methods. These simple luminescence techniques were used to estimate three benzoquinoline isomers in a coal tar fraction. Direct analysis of this complex sample allowed acridine to be estimated and upper limits to be provided for benzo(h)quinoline and phenanthridine; the presence of three other isomers was not detected. Comparative studies with data obtained by high-performance liquid chromatography are reported.  相似文献   
7.
Moody GJ  Thomas JD 《Talanta》1972,19(5):623-639
Features concerning development, response, selectivity and applications of selective ion-sensitive electrodes are reviewed. Recommendations are made concerning investigations involving the development and applications of electrodes and attention given to the manner of presenting data for publication.  相似文献   
8.
Results of ab initio and density functional theory calculations on the structure and vibrational frequencies of hypophosphite anion indicate earlier experimental assignments of the fundamental vibrational modes are correct while the recent reassignments of several modes proposed by Bickley et al. are inconsistent with the calculated results.  相似文献   
9.
The Bohlmann-Rahtz reaction has been used to prepare 2,3,6-trisubstituted pyridines suitable for use in library synthesis. The synthesis of piperidine substituted nicotinic acid derivative 9 has been optimised and carried out on a large scale to give ca. 500 g of scaffold which was used in the generation of the pyridine library 11.  相似文献   
10.
An extraction chromatographic method is described for the pre-concentration and separation of thorium, uranium, plutonium and americium in human soft tissues. Tissues such as lung and liver are oven dried at 120°C, ashed at 450°C and the ashed sample is alternately wet (HNO3/H2O2) and dry ashed, and then dissolved in 8M HCl. Because of the complex matrix and large sample samples (up to 1500 g), the actinides were preconcentrated from the tissue solution using the TRUTM resin (EIChroM) prior to elemental separation by extraction chromatography and determination of americium, plutonium, uranium and thorium by alpha spectrometry. The actinides were eluted from the preconcentration column and each actinide was individually eluted on TEVATM and TRUTM resin columns in a tandem configuration. Actinide activities were then determined by alpha spectrometry after electrodeposition from a sulfate medium. The method was validated by analyzing human tissue samples previously analyzed for americium, plutonium, uranium and thorium in the United States Transuranium and Uranium Registries (USTUR). Two National Institute of Standards and Technology (NIST) Standard Reference Materials, SRM 4351-Human Lung and SRM 4352-Human Liver were also analyzed. United States Transuranium and Uranium Registries, Washington State University, Pullman, WA, 99163, USA.  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