全文获取类型
收费全文 | 436757篇 |
免费 | 4873篇 |
国内免费 | 1232篇 |
专业分类
化学 | 234256篇 |
晶体学 | 6493篇 |
力学 | 18787篇 |
综合类 | 13篇 |
数学 | 50013篇 |
物理学 | 133300篇 |
出版年
2021年 | 3786篇 |
2020年 | 4197篇 |
2019年 | 4530篇 |
2018年 | 5862篇 |
2017年 | 5756篇 |
2016年 | 8846篇 |
2015年 | 5580篇 |
2014年 | 8563篇 |
2013年 | 20227篇 |
2012年 | 15674篇 |
2011年 | 19285篇 |
2010年 | 13521篇 |
2009年 | 13370篇 |
2008年 | 17698篇 |
2007年 | 17588篇 |
2006年 | 16299篇 |
2005年 | 14610篇 |
2004年 | 13554篇 |
2003年 | 11922篇 |
2002年 | 11756篇 |
2001年 | 13447篇 |
2000年 | 10111篇 |
1999年 | 7926篇 |
1998年 | 6575篇 |
1997年 | 6320篇 |
1996年 | 6093篇 |
1995年 | 5474篇 |
1994年 | 5400篇 |
1993年 | 5204篇 |
1992年 | 5840篇 |
1991年 | 5929篇 |
1990年 | 5672篇 |
1989年 | 5474篇 |
1988年 | 5497篇 |
1987年 | 5379篇 |
1986年 | 5095篇 |
1985年 | 6566篇 |
1984年 | 6697篇 |
1983年 | 5303篇 |
1982年 | 5391篇 |
1981年 | 5370篇 |
1980年 | 4957篇 |
1979年 | 5354篇 |
1978年 | 5494篇 |
1977年 | 5388篇 |
1976年 | 5329篇 |
1975年 | 4917篇 |
1974年 | 4887篇 |
1973年 | 4881篇 |
1972年 | 3459篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
M. O. Lozinskii A. F. Shivanyuk P. S. Pel'kis 《Chemistry of Heterocyclic Compounds》1971,7(4):439-442
The exchange and cyclization of phenyliminooxalyl chloride with ammonium thiocyanate, sodium azide, aniline, amidoximes, and diphenylthiourea, and with 2-aminopyridine, 2-aminobenzothiazole, and 2-amino- and 2-mercaptobenzimidazole were studied. The cyclization products are derivatives of thiazolidine, imidazo[1,2-a]pyridine, imidazo[2,1-b]benzothiazole, imidazo[1,2-a]benzimidazole, and thiazolo[3,2-a]benzimidazole. A trimer of 1-phenyltetrazole-5-carboxylic acid was obtained when an attempt was made to convert its azide to the corresponding isocyanate.See [1] for communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 471–474, April, 1971. 相似文献
992.
V. A. Postnikov Ts. V. Kakuliya L. M. Khananashvili Yu. V. Isaev Yu. N. Novikov M. E. Vol'pin 《Russian Chemical Bulletin》1979,28(3):626-627
Conclusions The stirred reaction of graphite with molten lithium gave compounds of composition C6Li, C12Li, and C18Li, for which the identity periods and thicknesses of the filled layers were determined.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 671–672, March, 1979. 相似文献
993.
994.
995.
I. C. McNeill L. Ackerman S. N. Gupta M. Zulfiqar S. Zulfiqar 《Journal of polymer science. Part A, Polymer chemistry》1977,15(10):2381-2392
In the subambient thermal volatilization analysis (TVA) technique, degradation products initially at ?196°C are allowed to warm up to ambient temperature in a controlled manner under vacuum conditions, and volatilization from the sample tube to a trap at ?196°C is monitored by means of a Pirani gauge. The technique is discussed in relation to earlier TVA work in which volatilization from a heated polymer sample was followed. Design and operation of a subambient TVA system are described, and examples of the application of the technique to the study of the degradation products of seven polymers are considered. 相似文献
996.
997.
998.
999.
1000.
R.R. Adžić D.N. Simić A.R. Despić D.M. Dražić 《Journal of Electroanalytical Chemistry》1975,65(2):587-601
It was demonstrated that some foreign metal monolayers formed by underpotential deposition have pronounced catalytic effects on the oxidation of formic acid on platinum. The explanation of these effects was sought within the framewor of existing data on the formic acid oxidation and the underpotential deposition. It was found that the catalytic effect of foreign metal monolayers originates in the decrease of hydrogen adsorption thus preventing the formation of the main poisoning species COH. At the same time these experiments confirm the previously postulated mechanism of formation of the poisoning species involving adsorbed hydrogen. 相似文献