全文获取类型
收费全文 | 358篇 |
免费 | 4篇 |
国内免费 | 7篇 |
专业分类
化学 | 354篇 |
晶体学 | 1篇 |
综合类 | 1篇 |
物理学 | 13篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 11篇 |
2016年 | 6篇 |
2014年 | 16篇 |
2013年 | 68篇 |
2012年 | 12篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 20篇 |
2008年 | 24篇 |
2007年 | 20篇 |
2006年 | 14篇 |
2005年 | 8篇 |
2004年 | 23篇 |
2003年 | 21篇 |
2002年 | 18篇 |
2001年 | 8篇 |
2000年 | 12篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 8篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有369条查询结果,搜索用时 7 毫秒
61.
Sanz D Claramunt RM Saini A Kumar V Aggarwal R Singh SP Alkorta I Elguero J 《Magnetic resonance in chemistry : MRC》2007,45(6):513-517
Multinuclear magnetic resonance spectroscopy together with GIAO-DFT calculations allowed establishment of the structure of the products obtained by condensation of 3(5)-amino-4-phenyl-1H-pyrazole and beta-dicarbonyl compounds bearing a trifluoromethyl group. They are 3-phenyl-5-(R)-7-trifluoromethylpyrazolo[1,5-a]pyrimidines. 相似文献
62.
63.
Albert Lévai 《Monatshefte für Chemie / Chemical Monthly》1991,122(8-9):691-695
Summary Reactions of 3-arylidenechromanones (1 – 4) and -1-thiochromanones (5 – 8) with thiourea gave thiazines (9 – 16) under acidic and pyrimidine derivatives (17 – 21) under alkaline reaction conditions
Kondensierte Heterocyclen, VI: Umsetzungen von 3-Arylidenchromanonen und-1-thiochromanonen mit Thioharnstoff
Zusammenfassung Die Umsetzung von 3-Arylidenchromanonen1 – 4 und -1-thiochromanonen5 – 8 mit Thioharnstoff liefert unter sauren Bedingungen die Thiazine9 – 16 und in basischem Milieu die Pyrimidine17 – 21.相似文献
64.
Biswajita Baruah 《Tetrahedron letters》2009,50(2):243-245
5-Formyl-6-tertiaryamino uracils 3 prepared from 6-chloro-5-formyl uracil derivative 1 react with barbituric acids 4 in the presence of base catalyst to afford a novel class of spirosubstituted pyrido[2,3-d]pyrimidines 5 via 1,6-electro-cyclisation in excellent yields. 相似文献
65.
Rodrigues LM Sivasubramanian A Pinto EM Oliveira-Campos AM Seijas JA Vázquez-Tato MP 《Magnetic resonance in chemistry : MRC》2009,47(1):84-86
A series of 21 substituted pyrazolo[3,4-d]pyrimidines-4-amines were studied by (1)H and (13)C NMR. The application of two-dimensional techniques, HMQC and HMBC, allowed the complete assignment of the spectra for all the compounds. 相似文献
66.
Reaction of 2-alkylthio-6-aminopyrimidin-4(3H)-ones with ethyl bromopyruvate to give ethyl 2-alkyl-thio-4-aminofuro[2,3-d]pyrimidine-5-carboxylates has been shown to proceed under neutral or acidic conditions. The obtained furo[2,3-d]pyrimidines underwent further cyclocondensation reaction with ethyl bromopyruvate to afford diethyl 5-alkylthiofuro[3,2-e]imidazo[1,2-c]pyrimidine-2,9-dicarboxy-lates.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 440–443, March, 2009. 相似文献
67.
Brough P Pécaut J Rassat A Rey P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(19):5134-5141
The chemistry of 2,2,4,4-substituted pentane derivatives has been investigated with the aim of providing a flexible and versatile synthetic route to pyrimidinyl nitronyl nitroxides, in which the bis-N-oxy fragment is incorporated in a six-membered ring. The synthesis of 2,4-diamino-2,4-dimethylpentane and 2,4-bis(hydroxylamino)-2,4-dimethylpentane, convenient precursors of these nitroxides, is described and full characterization of a series of pyrimidinyl nitronyl nitroxides is reported, along with a preliminary study of their coordination properties. 相似文献
68.
O. G. Kuzueva Ya. V. Burgart V. I. Saloutin O. N. Chupakhin 《Chemistry of Heterocyclic Compounds》2001,37(9):1130-1135
4,5-Bis(hydroxy)-4-trifluoromethyl-6-(fluoroalkyl)hexahydropyrimidin-2-ones (thiones) have been obtained for the first time by the reaction of ureas (thioureas) with di(fluoroalkyl)-substituted 1,3-diketones and tetraols, the dehydration of which gave 2-hydroxy(mercapto)-4-trifluoromethyl-6-(fluoroalkyl)pyrimidines. 相似文献
69.
E. Suloeva M. Yure E. Gudriniece S. Belyakov M. Petrova I. Kalnite 《Chemistry of Heterocyclic Compounds》2001,37(3):329-337
Syntheses are reported for a series of 2-alkylamino-6-phenyl-4-trifluoromethylpyridines. The reaction of 3-cyano-2-(hydroxyalkylamino)-6-phenyl-4-trifluoromethylpyridines with thionyl chloride gave the corresponding 2-(chloroalkylamino)pyridines, 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydro-imidazo[1,2-a]pyridines, and 9-cyano-6-phenyl-8-trifluoromethyl-2,3,4-trihydropyrido[1,2-a]-pyrimidines. X-ray diffraction structural analysis was used to study 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridine. 相似文献
70.
LI Zhi-li 《高等学校化学研究》2000,16(4):334-340
IntroductionThe intramolecular function group interaction plays an important role in gas--phase ionmolecular reactions and the fragmentation reactions of its product ionsLI--12]. The fragmenta..non reactions of the odd--electron ions of benzoic acid[13], phenylacetyleneL"], phenylsulfide[15], nitrobenzene[16j, methoxybenzaldehyde["] and acetophenone["J obviously show theOrtho effect. The fragmentation properties of the protonated molecules and the adduct ions ofo, m, p- meth oxy - ac etop he… 相似文献