全文获取类型
收费全文 | 497篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
化学 | 394篇 |
晶体学 | 2篇 |
力学 | 7篇 |
数学 | 22篇 |
物理学 | 79篇 |
出版年
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 7篇 |
2014年 | 10篇 |
2013年 | 18篇 |
2012年 | 18篇 |
2011年 | 25篇 |
2010年 | 19篇 |
2009年 | 12篇 |
2008年 | 19篇 |
2007年 | 14篇 |
2006年 | 25篇 |
2005年 | 25篇 |
2004年 | 23篇 |
2003年 | 18篇 |
2002年 | 18篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1997年 | 5篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1990年 | 3篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1971年 | 3篇 |
1970年 | 5篇 |
1969年 | 3篇 |
1967年 | 4篇 |
排序方式: 共有504条查询结果,搜索用时 15 毫秒
1.
2.
Lyashenko G. S. Dmitriev D. V. Yazovtsev I. A. Demina M. M. Albanov A. I. Medvedeva A. S. 《Russian Journal of Organic Chemistry》2003,39(10):1497-1500
Hydrosilylation of 2-(2-propynyl)-2,3-dihydro-1,2-benzothiazol-3-one 1,1-dioxide with 1-alkynyldimethyl- and bis(1-alkynyl)methylsilanes of the general formula Me
n
HSi(C=-CR)3-n (n = 1, 2) in the presence of H2PtCl6 (Speier's catalyst) occurs in a nonregioselective but stereoselective fashion, yielding mixtures of the corresponding trans-- and -adducts. The fraction of the latter ranges from 50 to 70%, depending mainly on the substrate nature rather than on the nature of substituent at the triple bond of the reagent. 相似文献
3.
Conclusions The oxazoline method was used to synthesize the methylamides of O-(2-acetamido-2-desoxy--D-glucopyranosyl)-N-acetylserine and O-(2-acetamido-2-desoxy--D-glucopyranosyl)-N-acetylthreonine.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 697–699, March, 1975. 相似文献
4.
5.
Kiselev V. D. Iskhakova G. G. Kashaeva E. A. Shikhab M. S. Medvedeva M. D. Konovalov A. I. 《Russian Journal of General Chemistry》2003,73(12):1884-1892
The partial molar volumes of reactants and products of the [3+2] addition of C-(p-nitrophenyl)-N-phenylnitrone to maleic anhydride and of the [4+2] addition of 9,10-dimethylanthracene to the same dienophile were determined, and the reaction volumes were calculated. A new method was suggested for determining the reaction volume. The activation volumes of both reactions were calculated from the dependences of the reaction rates on the external pressure. The volume parameters of the reactions involving the reagents of close size are close. The ratios of the activation volumes to the reaction volumes are unity, which suggests a common concerted mechanism of the reactions. Factors that could be responsible for significant changes in the absolute values of the reaction volume parameters are discussed. 相似文献
6.
Conclusions Both the nucleophilic and the free radical addition of n-butyl mercaptan to acetylenic-hydroxy ketones (1,1-disubstituted derivatives of 2-pentyn-1-ol-4-one) lead to the formation of the corresponding 1,1-disubstituted derivatives of 2-butylthio-2-penten-1-ol-4-one in 41–65% yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1669–1670, July, 1973. 相似文献
7.
Darja?Rudan-Tasic Cveto?KlofutarEmail author 《Monatshefte für Chemie / Chemical Monthly》2004,135(7):773-784
Summary. The freezing temperatures of dilute aqueous solutions of some poly(oxyethylene) glycols (PEG, HO–(CH2CH2O)
n
–H, n varying from 4 to 117) were measured over a solute to solvent mass ratio from 0.0100 to 0.3900. The second and third osmotic virial coefficient (A
22 and A
222) of poly(oxyethylene) glycols in aqueous solution were determined. The molecular weight dependence of the second virial coefficient can be described by a simple relation A
22=2×10–5
M
n
1.86, and the third virial coefficient is A
222=0.038A
22
2. The activity coefficients of the solute were calculated using the Gibbs-Duhem equation as applied by Bjerrum. From the osmotic and activity coefficients the excess Gibbs energies of solution, as well as the respective partial molar functions of solute and solvent and the virial pair interaction coefficients for the excess Gibbs energies were estimated. The second and the third osmotic virial coefficients are correlated with the Mc-Millan-Mayer virial coefficients. 相似文献
8.
V. D. Kiselev M. D. Medvedeva E. A. Kashaeva M. S. Shikhaab G. G. Iskhakova A. I. Konovalov 《Russian Journal of General Chemistry》2002,72(3):432-435
From the partial molar volumes of tetracyanoethylene, trans,trans-1,4-diphenyl-1,3-butadiene, and their Diels-Alder adduct, the volumes of the reaction in a series of solvents at 25°C (cm3 mol-
1) were calculated: in dioxane, -26.4; in chloroform, -34.9; in ethyl acetate, -34.5; in acetonitrile, -4.4; in cyclohexanone, -34.0; in 1,2-dichloroethane, -31.8; in benzene, -26.9; in toluene, -24.5; in o-xylene, -21.1; and in mesitylene, -16.9. The solvent effects on the activation and reaction volumes and on the partial molar volumes of the reactants, activated complex, and adduct were discussed. 相似文献
9.
The densities of ethanol and ethanol–water mixtures were measured with a vibrating tube densimeter at 25.0, 50.0 and 75.0 °C in the pressure range from 0.10 to 40.00 MPa. Densities were correlated using an empirical model. Partial molar volumes, excess molar volumes, isothermal compressibilities, cubic expansion coefficients and internal pressures were calculated from obtained densities. This study reports the dependence of densities, partial molar volumes, excess molar volumes, isothermal compressibilities, cubic expansion coefficients and internal pressures on composition, temperature and pressure. 相似文献
10.