全文获取类型
收费全文 | 398765篇 |
免费 | 3497篇 |
国内免费 | 1335篇 |
专业分类
化学 | 201645篇 |
晶体学 | 6605篇 |
力学 | 18736篇 |
综合类 | 5篇 |
数学 | 46024篇 |
物理学 | 130582篇 |
出版年
2020年 | 3261篇 |
2019年 | 3698篇 |
2018年 | 4907篇 |
2017年 | 4755篇 |
2016年 | 6972篇 |
2015年 | 4339篇 |
2014年 | 7000篇 |
2013年 | 17670篇 |
2012年 | 13456篇 |
2011年 | 16494篇 |
2010年 | 11547篇 |
2009年 | 11374篇 |
2008年 | 15019篇 |
2007年 | 15163篇 |
2006年 | 14379篇 |
2005年 | 12990篇 |
2004年 | 12042篇 |
2003年 | 10678篇 |
2002年 | 10487篇 |
2001年 | 12011篇 |
2000年 | 9266篇 |
1999年 | 7295篇 |
1998年 | 5966篇 |
1997年 | 5887篇 |
1996年 | 5553篇 |
1995年 | 5090篇 |
1994年 | 4942篇 |
1993年 | 4925篇 |
1992年 | 5320篇 |
1991年 | 5432篇 |
1990年 | 5174篇 |
1989年 | 4956篇 |
1988年 | 5099篇 |
1987年 | 4948篇 |
1986年 | 4637篇 |
1985年 | 6236篇 |
1984年 | 6609篇 |
1983年 | 5384篇 |
1982年 | 5734篇 |
1981年 | 5634篇 |
1980年 | 5383篇 |
1979年 | 5572篇 |
1978年 | 5740篇 |
1977年 | 5706篇 |
1976年 | 5807篇 |
1975年 | 5364篇 |
1974年 | 5331篇 |
1973年 | 5538篇 |
1972年 | 3718篇 |
1971年 | 3031篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
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
993.
994.
995.
A. Zh. Zhakaeva T. Yu. Orlova V. I. Zdanovich V. N. Setkina D. N. Kursanov 《Russian Chemical Bulletin》1977,26(1):202-203
Conclusions The pyridinium cyclopentadienylidechromium(molybdenum) tricarbonyl complexes were synthesized and a study was made of their IR, NMR, and mass spectra.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 227–228, January, 1977.The authors express their gratitude to N. I. Vasyukova and G. A. Panosyan for taking the mass and NMR spectra. 相似文献
996.
Ohne Zusammenfassung 相似文献
997.
S. S. Mochalov T. P. Surikova Yu. S. Shabarov 《Chemistry of Heterocyclic Compounds》1976,12(10):1106-1109
The cyclization of 2-nitroso-4-nitropropiophenone under the influence of hydrogen chloride proceeds in a more complex manner than in the cases previously described for other 4-substituted-2-nitrosopropiophenones: three, rather than two, haloanthranils are formed, and their formation is accompanied simultaneously by a number of redox transformations. This fact is explained by a decrease in the ability of the carbonyl group in the investigated ketone to undergo protonation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1334–1337, October, 1976. 相似文献
998.
999.
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
1000.
N. S. Magomedova A. N. Sobolev V. K. Belskii A. M. Koroteev M. P. Koroteev É. E. Nifantiev 《Journal of Structural Chemistry》1994,34(4):627-633
The structures of dioxaphosphepane (I) and dioxaphosphecane (II) salts prepared by hydrolysis of the corresponding bicyclophosphates have been compared. In both cases, hydrolysis occurs with breaking of the P–O bond of the fragment at the secondary carbon atom of bicyclophosphate. In phosphocycles I and II, the endocyclic bond angles O–P–O are 104.2 and 104.9°, and the exocyclic ones are 117.7 and 118.6°, respectively. Conformations of the anions in I and II differ substantially: for I it is a twist conformationC1TC4, and for II a distorted armchair. The data obtained are compared with those found earlier for similar molecules.Moscow State Pedagogical University. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 4, pp. 154–160, July–August, 1993.Translated by T. Yudanova 相似文献