全文获取类型
收费全文 | 279篇 |
免费 | 5篇 |
专业分类
化学 | 278篇 |
晶体学 | 1篇 |
物理学 | 5篇 |
出版年
2022年 | 2篇 |
2018年 | 4篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2013年 | 5篇 |
2012年 | 2篇 |
2011年 | 3篇 |
2010年 | 5篇 |
2009年 | 8篇 |
2008年 | 12篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 14篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 10篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1976年 | 10篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 4篇 |
1972年 | 11篇 |
1971年 | 7篇 |
1970年 | 6篇 |
1969年 | 6篇 |
1967年 | 2篇 |
1966年 | 9篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1963年 | 5篇 |
1960年 | 1篇 |
排序方式: 共有284条查询结果,搜索用时 0 毫秒
221.
V. V. Roznyatovsky N. E. Borisova M. D. Reshetova A. G. Buyanovskaya Yu. A. Ustynyuk 《Russian Chemical Bulletin》2005,54(9):2219-2223
Novel asymmetric macrocyclic Schiff bases were synthesized by the condensation of N,N′-bis(2-aminophenyl)-3,4-diphenylthiophene-2,5-dicarboxamide (1) with diformyl derivatives of phenol, furan, difurans, pyridine, pyrrole, and dipyrroles. The reaction proceeds in high yields
and without by-products in methanol in the presence of inorganic and organic acids (proton-template condensation). In the
case of monocyclic diformyl derivatives and di(5-formylfuran-2-yl) sulfide, the reaction occurs in 1,4-dioxane (templateless
synthesis). The synthesized macrocycles were characterized by elemental analysis data and NMR and mass spectra.
For Part 6, see Ref. 1.
Dedicated to Academician N. S. Zefirov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2152–2156, September, 2005. 相似文献
222.
E. S. Kotlova M. V. Pavlovskaya I. D. Grishin O. V. Semeikin N. A. Ustynyuk D. F. Grishin 《Polymer Science Series B》2011,53(3-4):108-115
The polymerization of styrene, methyl methacrylate, and vinyl chloride catalyzed by η5-cyclopentadienyl-η2-styrenedicarbonylmanganese is studied. It is shown that the cyclopentadienyl complex of manganese containing the monomer ligand (styrene) in the coordination sphere can initiate the radical polymerization of vinyl monomers in a mild temperature range. On the basis of the experimental data and the quantum-chemical simulation of the initial stages of the process, schemes describing the initiation of polymerization under the action of the complex under study and the binary initiating system containing carbon tetrachloride are advanced. In the latter case, additional acceleration of the reaction is related to the interaction of carbon tetrachloride with the triplet form of the manganese complex that yields trichloromethyl radicals initiating polymerization. 相似文献
223.
Borisova N. E. Ustynyuk Yu. A. Reshetova M. D. Aleksandrov G. G. Eremenko I. L. Moiseev I. I. 《Russian Chemical Bulletin》2004,53(2):340-345
Reactions of 2,6-bis(3-aminopropylaminocarbonyl)pyridine (1) with 4-tert-butyl-2,6-diformylphenol and 2,5-diformylpyrrole in the presence of Ba(ClO4)2 in EtOH afford barium complexes with asymmetric macrocyclic Schiff bases as soft and hard ligands. The reaction of compound 1 with Cu(OCOCMe3)2 involves closure of a tetrahydropyrimidine ring to give a mononuclear complex, which was structurally characterized by X-ray diffraction analysis. 相似文献
224.
O. V. Gusev N. A. Ustynyuk T. A. Peganova A. V. Gonchar P. V. Petrovskii K. A. Lyssenko 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):322-331
The behavior of different anilines H2NC6H4R (R = o-Me, p-Me, o-, m- and p? i Pr, p-OMe, p-CO2Et) and 2,6-Me2C6H3NH2 towards trihalophosphoranes was studied. 2,6-Me2C6H3NH2 failed to form the diaminophosphonium salt [Ph2PNH(2,6-Me2C6H3)2]Br, and the aminophosphine oxide Ph2(2,6-Me2C6H3NH)PO was the only isolated product. Both o- and p-toluidine gave the corresponding diaminophosphonium salts; however in the case of o-toluidine, the yield was low and a mixture with the respective aminophosphine oxide was observed. Anilines containing methoxy and ethoxycarbonyl groups in para-position form the diaminophosphonium salts in reasonable yields. 相似文献
225.
Larissa N. Ikryannikova Leila Yu. Ustynyuk Alexander N. Tikhonov 《Magnetic resonance in chemistry : MRC》2010,48(5):337-349
An explicit DFT modeling of water surroundings on the electron paramagnetic resonance properties of 4‐amino‐2,2,6,6‐tetramethyl‐piperidine‐N‐oxyl (TA) has been performed. A stepwise hydration of TA is accompanied with certain changes in geometrical parameters (bond lengths and angles) and redistribution of partial electric charges in TA. An aqueous cluster of 45 water molecules can be considered as an appropriate model for a complete aqueous shell around TA, although most of the structural and electronic characteristics of TA already converge at about 10 water molecules. Water surroundings induce an increase in electron spin density on the nitrogen atom of the nitroxide fragment due to stabilization of the polar resonance structure > N+?? O? at the expense of less polar structure > N? O?. The water‐induced rise of the isotropic splitting constant aiso, calculated from the contact term of the hyperfine interaction, comprises Δaiso(ρN2) = 2.2–2.5 G, which is typical of experimental value for TA. There are two contributions to the solvent effect on the aiso(ρN2) value: the redistribution of spin density in the nitroxide fragment (polarity effect) and water‐induced distortions of TA geometry. Microscopic variations in a hydrogen‐bonded water network cause noticeable fluctuations of the splitting constant aiso(ρN2). Calculations of the atomic spin density (σN2) allowed us to compute the splitting constant from the relationship aiso(σN2) = QσN2, where Q = 36.2 G. A practical advantage of using this relationship is that it gives ‘smoothed’ values of the splitting constant, which are sensitive to the environment polarity but remain tolerant to microscopic fluctuations of the hydrogen‐bonded water network around a spin‐label molecule. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
226.
The reactions of 2,5-diformylpyrrole (1) and 2,6-diformylpyridine (2) with propane-1,3-diamine afforded new macrocyclic Schiff"s bases 5 and 6, respectively. Their structures were established by NMR spectroscopy and mass spectrometry. Binuclear copper(ii) and nickel(ii) complexes with ligand 5 were synthesized. Pentadentate Schiff"s base, viz., 2,6-bis[(2-aminophenylimino)methyl]pyridine, was prepared by demetallation of its complex with Cd(ClO4)2 using Na2S. In solutions, the latter Schiff"s base is quantitatively transformed into 2,6-bis(benzoimidazolyl)pyridine under the action of atmospheric oxygen or other mild oxidizing agents. 相似文献
227.
A DFT study of ethylene polymerization by zirconocene catalysts was carried out. Stationary points corresponding to intermediates
and transition states were located on the potential energy surface of the [Cp2ZrC2H5]++C2H4 model system. Three possible reaction mechanisms involving the formation of β-agostic complexes were considered. The energy
and thermodynamic characteristics for different reaction pathways were calculated. Corresponding activation energies lie in
the range 3.9–6.8 kcal mol−1.
Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1168–1177, July, 2000. 相似文献
228.
229.
230.
Complexes of Uranyl Nitrate with 2,6‐Pyridinedicarboxamides: Synthesis,Crystal Structure,and DFT Study 下载免费PDF全文
Mikhail Alyapyshev Vasiliy Babain Lyudmila Tkachenko Vladislav Gurzhiy Andrey Zolotarev Yuriy Ustynyuk Igor Gloriozov Alexander Lumpov Dmitriy Dar'in Alena Paulenova 《无机化学与普通化学杂志》2017,643(9):585-592
Two complexes of uranyl nitrate with N,N,N′,N′‐tetrabutyl‐2,6‐pyridinedicarboxamide (TBuDPA) and N,N′‐diethyl‐N,N′‐diphenyl‐2,6‐pyridinedicarboxamide (EtPhDPA) were synthesized and studied. The complex of tetraalkyl‐2,6‐pyridinedicarboxamide with metal nitrate was synthesized for the first time. XRD analysis revealed the different type of complexation: a 1:1 metal:ligand complex for EtPhDPA and complex with polymeric structure for TBuDPA. The quantum chemical calculations (DFT) confirm that both ligands form the most stable complexes that match the minimal values pre‐organization energy of the ligands. 相似文献