全文获取类型
收费全文 | 298篇 |
免费 | 7篇 |
专业分类
化学 | 266篇 |
数学 | 23篇 |
物理学 | 16篇 |
出版年
2020年 | 7篇 |
2017年 | 3篇 |
2015年 | 5篇 |
2014年 | 2篇 |
2013年 | 13篇 |
2012年 | 12篇 |
2011年 | 15篇 |
2010年 | 9篇 |
2009年 | 10篇 |
2008年 | 10篇 |
2007年 | 14篇 |
2006年 | 4篇 |
2005年 | 10篇 |
2004年 | 11篇 |
2003年 | 13篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1972年 | 5篇 |
1971年 | 6篇 |
1970年 | 3篇 |
1969年 | 16篇 |
1968年 | 11篇 |
1967年 | 7篇 |
1966年 | 2篇 |
1965年 | 3篇 |
1964年 | 3篇 |
1963年 | 7篇 |
1962年 | 3篇 |
排序方式: 共有305条查询结果,搜索用时 109 毫秒
1.
2.
3.
Thomas Kappe Wolfgang Stadlbauer 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2)
Abstract Carbon suboxide has been used frequently in organic synthesis,1 especially in the synthesis of heterocyclic compounds not obtainable by other routes. Although carbon subsulfide is known for more than 80 years, until recently only a few simple derivatives such as dithiomalonamides were prepared. The reason for this situation arises from the difficulties encountered in the preparation of C3S2. We have recently described a modification of the known preparation procedures, taking advantage of commercially available glassware (Quickfitt)2. 相似文献
4.
Yuesu Chen Gabriel Glotz Dr. David Cantillo Prof. Dr. C. Oliver Kappe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(13):2973-2979
N-Demethylation of oxycodone is one of the key steps in the synthesis of important opioid antagonists like naloxone or analgesics like nalbuphine. The reaction is typically carried out using stoichiometric amounts of toxic and corrosive reagents. Herein, we present a green and scalable organophotocatalytic procedure that accomplishes the N-demethylation step using molecular oxygen as the terminal oxidant and an organic dye (rose bengal) as an effective photocatalyst. Optimization of the reaction conditions under continuous flow conditions using visible-light irradiation led to an efficient, reliable, and scalable process, producing noroxycodone hydrochloride in high isolated yield and purity after a simple workup. 相似文献
5.
Muhammad Imran Malik Bernd Trathnigg C. Oliver Kappe 《Journal of chromatography. A》2009,1216(7):1167-1173
Homopolymers and block copolymers of higher epoxides (butene oxide and hexene oxide) are synthesized using 1-alkanols and polyethylene glycol monomethyl ether (PEG-MME) 1100 as initiators by anionic ring opening polymerization in bulk. Most of the samples were synthesized with controlled microwave heating in sealed vessels. Tri- and tetrablock copolymers with different repeat units in the individual blocks are synthesized by living polymerization with addition of the next monomer after complete consumption of the previous one. The products thus obtained are characterized using size exclusion chromatography (SEC), liquid chromatography under critical conditions (LCCC) and liquid adsorption chromatography (LAC). 相似文献
6.
7.
8.
9.
10.
Ya.V. Burgart O.G. Kuzueva M.V. Pryadeina C.O. Kappe V.I. Saloutin 《Russian Journal of Organic Chemistry》2001,37(6):869-880
Hexafluoroacetylacetone reacts with urea (thiourea) to yield respectively 4,6-bis(hydroxy)-4,6-bis(trifluoromethyl)hexahydropyrimidin-2-one(thione). The dehydration of the products and also reaction of nonsymmetrical fluoroalkyl-containing 1,3-diketones with urea (thiourea) afford substituted pyrimidines. The condensation of fluorinated 3-oxoesters and 1,3-diketones with benzaldehyde and urea (thiourea) results in 5-alkoxycarbonyl(acyl)-4-hydroxy-2-oxo(thioxo)-6-phenyl-4-fluoroalkylhexahydropyrimidines that on dehydration furnish 5-alkoxycarbonyl(acyl)-2-oxo(thioxo)-4-phenyl-6-fluoroalkyltetrahydropyrimidines. Ethyl 7-nonafluorobutyl-5-phenyl-2,3-dihydrothiazolo[3,2-a]pyrimidine-6-carboxylate hydrobromide forms in reaction of dibromoethane with ethyl ether of 2-thioxo-4-phenyl-6-nonafluorobutyltetrahydropyrimidine. 相似文献