全文获取类型
收费全文 | 1047篇 |
免费 | 5篇 |
专业分类
化学 | 663篇 |
晶体学 | 8篇 |
力学 | 12篇 |
数学 | 69篇 |
物理学 | 300篇 |
出版年
2022年 | 9篇 |
2021年 | 18篇 |
2020年 | 22篇 |
2019年 | 19篇 |
2018年 | 25篇 |
2017年 | 29篇 |
2016年 | 37篇 |
2015年 | 16篇 |
2014年 | 25篇 |
2013年 | 58篇 |
2012年 | 28篇 |
2011年 | 44篇 |
2010年 | 43篇 |
2009年 | 34篇 |
2008年 | 38篇 |
2007年 | 37篇 |
2006年 | 39篇 |
2005年 | 30篇 |
2004年 | 37篇 |
2003年 | 22篇 |
2002年 | 33篇 |
2001年 | 34篇 |
2000年 | 17篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 14篇 |
1994年 | 10篇 |
1992年 | 8篇 |
1991年 | 18篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 18篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1975年 | 14篇 |
1974年 | 19篇 |
1973年 | 14篇 |
1972年 | 17篇 |
1971年 | 9篇 |
1970年 | 7篇 |
1967年 | 8篇 |
排序方式: 共有1052条查询结果,搜索用时 31 毫秒
11.
N. N. Lobanov I. S. Popova N. U. Venskovskii 《Russian Journal of Inorganic Chemistry》2006,51(6):960-963
The crystal-chemical properties of lanthanide oxobromotungstates of composition LnWO4Br (Ln = Eu, Gd, Dy, Er, Yb) are studied. The crystal system and space group for the oxobromotungstates are determined. The unit cell parameters are refined. The parameters a, b, c, and V of the LnWO4Br compounds are studied as functions of the atomic number of the lanthanide. Analytical equations are derived to predict unit cell parameters for unsynthesized lanthanide oxobromotungstates of the class in question. 相似文献
12.
G. N. Dorofeenko Yu. P. Andreichikov É. A. Zvezdina V. A. Bren' G. E. Trukhan V. V. Derbenev A. N. Popova 《Chemistry of Heterocyclic Compounds》1974,10(10):1177-1181
The pyridinium ring as a substituent in aniline is an electron acceptor, the effect of which is comparable to the effect of NO2 and N(CH3)2 groups. Correlation of the reactivities with the basicities of the amino groups is not observed in the investigated reactions of N-(aminophenyl)pyridinium perchlorates with some electrophilic reagents, inasmuch as steric factors apparently play a greater role. 相似文献
13.
B. L. Tumanskii A. A. Kadyrov O. A. Popova L. T. Lantseva N. N. Bubnov S. P. Solodovnikov K. N. Makarov 《Russian Chemical Bulletin》1991,40(5):903-907
The EPR method was used to study the structure of spin adducts of silyl and phosphonyl radicals with higher internal perfluoroalkenes. The capacity for spin adducts to split off hydrogen atoms is determined by the degree of steric screening of the free radical center. The preparative photochemical reaction of hydrosilanes and dialkyl phosphites with perfluoro-4-methylpent-2-ene leads to regiospecific hydrosilylation and hydrophosphorylation products with yields up to 80%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1018–1023, May, 1991. 相似文献
14.
15.
I. Pelant M. N. Popova J. Hála M. AmbroŽ V. Lhotská K. Vacek 《Czechoslovak Journal of Physics》1987,37(10):1183-1197
Dependence of two-photon absorption (TPA) rate on the state of polarization of a laser beam is investigated in the low-temperature orthorhombic modification of Hg2Cl2 crystals. Theoretical calculations of the dependence of TPA rate on the direction of polarization vector of the beam are performed for centrosymmetric points, Y, Z, T, R andS of the Brillouin zone. The domain structure of real crystals is taken into consideration and it is shown that periodicity of the polarization dependence may indicate whether TPA is due to transitions either at, Y, Z, T orR, S points. The polarization dependence of TPA cannot, however, distinguish between points inside these two groups. Comparison of theory with a low-temperature (T 8·5 K) experimental curve of polarization dependence is discussed. It is shown that the experiment can be explained in main features by a model of noninteracting oriented linear dipoles. Further, on the basis of TPA measurements, a simple energy band structure of Hg2Cl2 is proposed regarding Hg2Cl2 crystal as a linear chain of molecules.The authors express thanks to Dr. . Barta for supplying the Hg2Cl2 crystals, Dr. Z. Bryknar for critical comments and Dr. B. Velický for stimulating discussion. We thank also Dr. V. Kohlová for assistance during measurement. 相似文献
16.
Spectrophotometric investigation of the reaction of eriochrome cyanin RC and magnesium and aluminium
The reaction of magnesium or aluminium ions with Eriochrome Cyanin RC in alkaline medium leads to formation of a complex of type ML. The molar absorptivities of the complexes are 1.90 +/- 0.14 x 10(3)1. mole(-1).cm(-1) at 570 nm for the magnesium complex and 3.87 +/- 0.04 x 10(4) at 555 nm for the aluminium complex. The conditional stability constants of the complexes were determined at various pH values, and hence the overall formation constants, which were found to be log beta(111) = 8.65 +/- 0.06 for MgOHL, log beta(121) = 22.29 +/- 0.05 for AlH(2)L, log beta(111) = 18.25 +/- 0.14 for AlHL, and log beta(101) = 13.66 +/- 0.01 for AlL. 相似文献
17.
Z. Popova R. Dimitrova Chr Dimitrova G. Wendt 《Reaction Kinetics and Catalysis Letters》1989,39(1):27-32
Temperature programmed reduction (TPR) has been used to study the redox behavior of Ni(II) ions in nickel sodium mordenite (NiNaM) and decationated nickel mordenite (NiHM). The TPR profiles suggest that Ni(II) ions occupy nonequivalent sites with different cooridination states in the mordenite. The reducibility of Ni(II) depends strongly on the zeolite acidity.
() NiII NiNaM NiHM. . .相似文献
18.
TPD data indicate that N2O is desorbed from Ru and -Al2O3 without decomposition in one step and from Ru/Al2O3 in two steps with simultaneous decomposition to nitrogen and oxygen.
, N2O Ru -Al2O3 , Ru/Al2O3— .相似文献
19.
Ya. I. Korenman N. N. Popova T. A. Kuchmenko S. M. Suleimanov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(12):1993-1998
The effect of the morphology of polymer films on the distribution of volatile C1–C4 carboxylic acids in the sorbent-gas system is discussed. The efficiency of sorption of vapors of formic, acetic, propionic, and butyric acids on films of polyethylene glycol esters of various structures formed on the electrodes of a piezoquartz resonator by means of static evaporation of a drop and immersion of the resonator into a sorbent solution is evaluated. 相似文献
20.
É. A. Zvezdina O. M. Golyanskaya I. M. Andreeva A. N. Popova E. A. Medyantseva G. N. Dorofeenko 《Chemistry of Heterocyclic Compounds》1982,18(4):340-343
2-Substituted 3,5,7-triaryl-1,2-oxazepinium perchlorates were obtained by the reaction of 2,4,6-triarylpyrylium salts in dimethylformamide with nitrones and N-arylhydroxylamines. The products are the first representatives of seven-membered cations with eight electrons.See [1] for Communication 9.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 457–460, April, 1982. 相似文献