全文获取类型
收费全文 | 1352篇 |
免费 | 5篇 |
专业分类
化学 | 763篇 |
晶体学 | 13篇 |
力学 | 53篇 |
数学 | 88篇 |
物理学 | 440篇 |
出版年
2021年 | 28篇 |
2020年 | 24篇 |
2019年 | 32篇 |
2018年 | 46篇 |
2017年 | 43篇 |
2016年 | 52篇 |
2015年 | 24篇 |
2014年 | 54篇 |
2013年 | 73篇 |
2012年 | 64篇 |
2011年 | 49篇 |
2010年 | 63篇 |
2009年 | 44篇 |
2008年 | 47篇 |
2007年 | 58篇 |
2006年 | 48篇 |
2005年 | 30篇 |
2004年 | 39篇 |
2003年 | 30篇 |
2002年 | 38篇 |
2001年 | 29篇 |
2000年 | 20篇 |
1999年 | 13篇 |
1998年 | 10篇 |
1997年 | 9篇 |
1996年 | 14篇 |
1993年 | 9篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1976年 | 10篇 |
1975年 | 11篇 |
1974年 | 13篇 |
1973年 | 17篇 |
1972年 | 13篇 |
1971年 | 17篇 |
1970年 | 10篇 |
1969年 | 11篇 |
1968年 | 16篇 |
1967年 | 14篇 |
1966年 | 12篇 |
1965年 | 10篇 |
1964年 | 13篇 |
1963年 | 9篇 |
1960年 | 11篇 |
1959年 | 9篇 |
排序方式: 共有1357条查询结果,搜索用时 312 毫秒
11.
12.
Mironov YV Yarovoi SS Naumov DY Kozlova SG Ikorsky VN Kremer RK Simon A Fedorov VE 《The journal of physical chemistry. B》2005,109(50):23804-23807
The novel vanadium thiobromide, V4S9Br4, with a square-planar metal cluster core was synthesized and characterized by single-crystal X-ray diffraction, measurements of magnetic properties and the heat capacity, and DFT calculations of the electronic structure. At the room temperature, the compound displays paramagnetic properties with an independent spin on each V atom and with a weak exchange constant (J approximately 10 cm(-1)). The paramagnetic state is transformed into a low-spin state (AF-type ordering) at low temperatures. This change is accompanied by a heat-capacity anomaly. The observed magnetic and heat-capacity anomalies can be explained by the thermal excitation of electrons on the closely spaced molecular energy levels in the presence of the Jahn-Teller effect. 相似文献
13.
14.
The results of a kinetic study of model reactions between substituted phenols and bromobenzene in the presence of potassium carbonate and the copper(I) chloride–8-hydroxyquinoline catalytic complex in N,N-dimethylformamide are presented. The reactions were found to obey a first-order rate law. Both orbital and charge interactions should be taken into account in a consideration of the effect of the structural characteristics of reactants on the rate of reaction. The kinetics of substitution of the phenoxide anion for an aromatically bound halogen atom in activated and nonactivated systems with the formation of practically valuable aryl ethers were comparatively studied. The results presented provide an opportunity to distinguish the common features and regularities of activated and nonactivated aromatic substitution in the test systems. 相似文献
15.
V. F. Mironov E. N. Varaksina A. A. Shtyrlina A. T. Gubaidullin N. M. Azancheev R. S. Musin I. A. Litvinov A. I. Konovalov 《Russian Journal of General Chemistry》2006,76(3):391-411
It was shown for the first time that 3-chloro-, 3-bromo-, and 3-iodopropynes can react with 2,2,2-trichloro-, 2,2,2-trichloro-5-methyl-, and 5,6-dibromo-2,2,2-trichloro-1,3,2λ5-benzodioxaphospholes to give derivatives of 4-(halomethyl)-2-chloro-2H-1,2λ5-benzoxaphosphinin-2-ones. The reaction involves nonselective chlorination of the phenylene substituent in different positions, and the resulting isomer ratio is temperature-dependent. In the reactions of 3-bromo-and 3-iodopropynes with 2,2,2-trichloro-1,3,2λ5-benzo-dioxaphosphole, a side process takes place, viz. nucleophilic substitution of bromine and iodine with chlorine. The structure of some of the prepared 4-(chloromethyl)-1,2-benzoxaphosphinines was studied by means of X-ray diffraction. 相似文献
16.
N. K. Ostrovskaya A. F. Mironov R. P. Evstigneeva N. A. Preobrazhenskii 《Chemistry of Heterocyclic Compounds》1969,5(4):470-473
A method is proposed for the synthesis of porphyrins based on the cyclization of a tetrapyrrole system with methyl and formyl groups at the ends of the molecule. The synthesis of mesoporphyrin IX and diacetyldeuteroporphyrin IX has been effected. 相似文献
17.
Mironov V. F. Ivkova G. A. Burnaeva L. M. Konovalova I. V. Musin R. Z. 《Russian Journal of General Chemistry》2003,73(9):1367-1370
The reaction of pyruvonitrile with 2-tetrafluoropropoxy-5,6-benzo-1,3,2-dioxaphosphorinan-4-one results mainly in the enlargement of the starting heteroring to form 4-cyano-4-methyl-2-tetrafluoropropoxy-6,7-benzo-1,3,25-dioxaphosphepin-5-one 2-oxide as a mixture of two diastereomers (14:1) along with minor amounts of 3-cyano-3-methyl-2-tetrafluoropropoxy-6,7-benzo-1,4,25-dioxaphosphepin-5-one 2-oxide. 相似文献
18.
G. F. Khudorozhko L. G. Bulusheva L. N. Mazalov V. E. Fedorov I. P. Asanov É. A. Kravtsova G. K. Parygina Yu. V. Mironov 《Journal of Structural Chemistry》1996,37(4):626-632
An X-ray amorphous phase of molybdenum tetrasulfide with the analytical formula MoS4 has been sythesized. Quantum chemical modeling of the suggested local structure of MoS4 and EHT calculation of the electronic structure of the basic (Mo2S4)4+ fragment are reported. The electronic structure of molybdenum tetrasulfide and its lithium intercalates was investigated
by X-ray emission and X-ray photoelectron spectroscopy. It is shown that the change in the electronic structure of the starting
molybdenum tetrasulfide to four lithium atoms per formula unit in the intercalate may be considered in the rigid band model.
Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 4, pp. 727–734, July–August, 1996.
Translated by L. Smolina 相似文献
19.
Andrei N. Kozyrev Andrei F. Mironov Jorge Davila Anthony Harriman 《Journal of heterocyclic chemistry》1988,25(3):885-889
The synthesis and characterisation of a C6 hydrocarbon linked porphyrin dimer and its zinc complex is described. From fluorescence quantum yields and excited singlet and triplet state lifetimes, recorded for the dimers and the corresponding monomer species, it is suggested that the dimeric porphyrins exist in solution in open and closed conformations. The open conformations retain photophysical properties similar to those of the relevant monomeric species but the closed conformations do not fluoresce. 相似文献
20.
A.G. Volkov M.I. Gugeshashvili A.F. Mironov L.I. Boguslavsky 《Journal of Electroanalytical Chemistry》1982,141(5):551-558
The redox reaction between the ferric complex of hydrophobic porphyrin and sodium dithionite in two different phases occurring at the interface between two immiscible liquids has been investigated by Volta potential measurements and spectroscopy. The reduction of the ferric complex of hydrophobic porphyrin adsorbed at the interface was found to be accompanied by a potential shift in the negative direction and to depend significantly on the nature of the anion and the ionic strength of the supporting electrolyte. Specifically adsorbed halogen anions inhibited the redox reaction in the sequence: Cl?, Br?, I?. Depending on pH, the ferric complex of hydrophobic porphyrin exists in the uncharged (FeP-O-PFe) form or in the cation FeP+ form. The interaction between the ferric complex hydrophobic porphyrin and water has also been investigated. 相似文献