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排序方式: 共有116条查询结果,搜索用时 15 毫秒
91.
Braga D Cojazzi G Emiliani D Maini L Grepioni F 《Chemical communications (Cambridge, England)》2001,(21):2272-2273
Exposure of the solid zwitterion [CoIII(eta 5-C5H4CO2H)(eta 5-C5H4CO2)] to hydrated vapours of volatile acids (HCl, CF3CO2H, HBF4) or bases (NH3, NMe3, NH2Me) quantitatively produces the corresponding salts; the heterogeneous reactions are fully reversible, as the acid or base molecules can be removed by thermal treatment, regenerating the starting material. 相似文献
92.
Andrea Caneschi Fabrizia Fabrizi de Biani Lars Kloo Piero Zanello 《International journal of quantum chemistry》1999,72(1):61-71
DFT calculations were carried out in order to deduce the dependence of magnetic coupling on the structure of doubly hydroxide/alkoxide‐bridged diiron(III) dimers. The broken‐symmetry formalism was employed to calculate the magnetic exchange parameter J. The potential surfaces of the ground state display a geometrical minimum at an Fe O(H) Fe angle of 105° and FeFe distance of 3.2 Å, in good agreement with experimental values. The calculated correlation between the magnetic coupling with the geometrical structure agrees well with the experimental literature data, although always overestimated. Electrochemical measurements show that a one‐electron reduction is likely to cause dissociation into pseudooctahedral, monomeric subunits, and, consequently, no calculations were made for the reduced dimeric species. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 72: 61–71, 1999 相似文献
93.
Dario Braga Lucia Maini Fabrizia Grepioni 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》1998,110(16):2365-2366
94.
Piero Zanello Rolfe H. Herber Alexander R. Kudinov Maddalena Corsini Fabrizia Fabrizi de Biani Israel Nowik Dmitry A. Loginov Mikhail M. Vinogradov Lidia S. Shul’pina Igor A. Ivanov Anna V. Vologzhanina 《Journal of organometallic chemistry》2009,694(7-8):1161-1171
Visible light irradiation of cation [(η5-C6H7)Fe(η-C6H6)]+ (1+) in acetonitrile results in substitution of the benzene ligand giving the labile acetonitrile derivative [(η5-C6H7)Fe(MeCN)3]+ (2a+). The stable isonitrile and phosphite complexes [(η5-C6H7)FeL3]+ [L = tBuNC (2b+), P(OMe)3 (2c+), P(OEt)3 (2d+)] were obtained by reaction of 1 with L in MeCN. The structures of 2cPF6, [CpFe(η-C6H6)]PF6 (3PF6), and Cp1Fe(η-C6H6)]PF6 (4PF6) were determined by X-ray diffraction.The redox activity of the cyclohexadienyl complexes 1+, 2b+?2d+ has been investigated by electrochemical techniques and compared with that of the related cyclopentadienyl complexes 3+ and 4+. DFT calculations of the redox potentials and the respective geometrical changes were performed.Variable temperature Mössbauer (ME) spectroscopy has elucidated the relationship between structure and formal oxidation state of the iron atom in these complexes. In the case of 3+ an unexpected pair of crystallographic changes has been observed and interpreted in terms of both a second and first order phase transition. The mean-square-amplitude-of-vibration of the metal atom has been compared between the ME and X-ray data. ME measurements in a magnetic field have shown that in 4+ the quadrupole splitting is positive as it is in ferrocene. 相似文献
95.
96.
Dr. Wei Jiang Chengyi Xiao Linxiao Hao Prof. Zhaohui Wang Harald Ceymann Prof. Christoph Lambert Dr. Simone Di Motta Prof. Fabrizia Negri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(22):6764-6775
The copper‐mediated Ullmann coupling of 1,7‐dibromoperylene bisimides afforded structurally perfect singly‐linked perylene bisimide (PBI) arrays, whilst the homo‐coupling of 1,12‐dibromoperylene bisimides gave doubly‐linked and triply‐linked diperylene bisimides. The interactions of three bay‐linked diperylene bisimides that differed in their linkage (singly, doubly, and triply) were investigated in their neutral and reduced forms (mono‐anion to tetra‐anion). UV/Vis absorption and fluorescence spectroscopy revealed different degrees of interaction, which was explained by exciton coupling and conjugation effects. The electrochemical properties and spectroelectrochemistry also showed quite‐different degrees of PBI interactions in the reduced mixed‐valence species, which was apparent by the observation of CT bands. The interpretation of the experimental findings was supported by spin‐restricted and ‐unrestricted DFT and time‐dependent TD‐DFT calculations with the long‐range‐corrected CAM‐B3LYP functional. Accordingly, the degree of interaction in both the neutral and reduced forms of the bay‐linked PBIs was qualitatively in the order doubly linked<singly linked?triply linked, owing to the different degrees of twisting and flexibility between the two PBIs moieties. Only triply linked diPBI showed completely delocalized wavefunctions over the entire π‐system. 相似文献
97.
98.
Fumagalli A Ulivieri P Costa M Crispu O Della Pergola R Fabrizi de Biani F Laschi F Zanello P Macchi P Sironi A 《Inorganic chemistry》2004,43(6):2125-2131
The redox aptitude of the dinitrido anion [Co10N2(CO)19]4- has been tested from both chemical and electrochemical points of view, together with its reactivity toward CO that induces disproportionation. In any case, through a remarkable overlapping of intermediate steps, the new anion [Co11N2(CO)21]3- (4) is eventually obtained. A detailed study of the pathways to 4 allowed the identification of three labile intermediates by their characteristic IR spectra as well as their electrochemical and paramagnetic properties. The unprecedented structure of trianion 4 has been studied in details in two different crystalline salts. 相似文献
99.
Braga D Polito M Giaffreda SL Grepioni F 《Dalton transactions (Cambridge, England : 2003)》2005,(16):2766-2773
The synthesis and structural characterization of the hexafluorophosphate salts of the substituted bis-amido molecular complexes [Co(III)(eta5-C5H4CONHC4H3N2)2]+ (1), [Co(III)(eta5-C5H4CONHCH2C5H4N)2]+ (2), [Co(III)(eta5-C5H4CON(C5H4N)2)2]+ (3), and of the amido-carboxyl complexes [Co(III)(eta5-C5H4CON(C5H4N)2)(eta5-C5H4COOH)]+ (4), and [Co(III)(eta5-C5H4CONHC2N3(C5H4N)2)(eta5-C5H4COOH)]+ (5) are reported. The pyridyl and pyrazine substituted amido ligands on the sandwich cores have been chosen because they allow both coordination to metal centres and participation in hydrogen bonding. The hydrogen bonding interactions established by the family of complexes in the solid state has been investigated. The utilization of complex 5 for the preparation of the complex of complexes[Cd(NO3)2{Co(III)(eta5-C5H4CONHC2N3(C5H4N)(C5H4NH))(eta5-C5H4COOH)}2]6+ (6) is reported as a first example of the potential of the substituted mono-and bis-amides as ligands. The isolation and structural characterization of the carbonyl chloride cation [Co(III)(eta5-C5H4COCl)2]+ (7) as its tetrachloro cobaltate anion salt is also described. 相似文献
100.
Giacomo Bondietti Gianfranco Suardi Renzo Ros Raymond Roulet Fabrizia Grepioni Dario Braga 《Helvetica chimica acta》1993,76(8):2913-2925
The synthesis of [Ir2Rh2(CO)12] ( 1 ) by the literature method gives a mixture 1 /[IrRh3(CO)12] which cannot be separated using chromatography. The reaction of [Ir(CO)4]? with 1 mol-equiv. of [Rh(CO)2(THF)2]+ in THF gives pure 1 in 61% yield. Crystals of 1 are highly disordered, unlike those of its derivative [Ir2Rh2(CO)5(μ2-CO)3(norbornadiene)2] which were analysed using X-ray diffraction. The ground-state geometry of 1 in solution has three edge-bridging CO's on the basal IrRh2 face of the metal tetrahedron. Time averaging of CO's takes place above 230 K. The CO site exchange of lowest activation energy is due to one synchronous change of basal face, as shown by 2D- and VT-13C-NMR. Substitution of CO by X? in 1 takes place at a Rh-atom giving [Ir2Rh2(CO)8(μ2-CO)3X]? (X = Br, I). Substitution by bidentate ligands gives [Ir2Rh2(CO)7(μ2-CO)3(η4-L)] (L = norbornadiene, cycloocta-1,5-diene) where the ligand L is chelating a Rh-atom of the basal IrRh2 face. Carbonyl substitution by tridentate ligands gives [Ir2Rh2(CO)6(μ2-CO)3(μ3-L)] (L = 1,3,5-trithiane, tripod) with L capping the triangular basal face of the metal tetrahedron. Carbonyl scrambling is also observed in these substituted derivatives of 1 and is mainly due to the rotation of three terminal CO's about a local C3 axis on the apical Ir-atom. 相似文献