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191.
Tahsini L Kotani H Lee YM Cho J Nam W Karlin KD Fukuzumi S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(4):1084-1093
The four-electron reduction of dioxygen by decamethylferrocene (Fc*) to water is efficiently catalyzed by a binuclear copper(II) complex (1) and a mononuclear copper(II) complex (2) in the presence of trifluoroacetic acid in acetone at 298 K. Fast electron transfer from Fc* to 1 and 2 affords the corresponding Cu(I) complexes, which react at low temperature (193 K) with dioxygen to afford the η(2):η(2)-peroxo dicopper(II) (3) and bis-μ-oxo dicopper(III) (4) intermediates, respectively. The rate constants for electron transfer from Fc* and octamethylferrocene (Me(8)Fc) to 1 as well as electron transfer from Fc* and Me(8)Fc to 3 were determined at various temperatures, leading to activation enthalpies and entropies. The activation entropies of electron transfer from Fc* and Me(8)Fc to 1 were determined to be close to zero, as expected for outer-sphere electron-transfer reactions without formation of any intermediates. For electron transfer from Fc* and Me(8)Fc to 3, the activation entropies were also found to be close to zero. Such agreement indicates that the η(2):η(2)-peroxo complex (3) is directly reduced by Fc* rather than via the conversion to the corresponding bis-μ-oxo complex, followed by the electron-transfer reduction by Fc* leading to the four-electron reduction of dioxygen to water. The bis-μ-oxo species (4) is reduced by Fc* with a much faster rate than the η(2):η(2)-peroxo complex (3), but this also leads to the four-electron reduction of dioxygen to water. 相似文献
192.
Daniel E. Diaz David A. Quist Austin E. Herzog Andrew W. Schaefer Ioannis Kipouros Mayukh Bhadra Edward I. Solomon Kenneth D. Karlin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(49):17736-17740
The dioxygen reactivity of a series of TMPA‐based copper(I) complexes (TMPA=tris(2‐pyridylmethyl)amine), with and without secondary‐coordination‐sphere hydrogen‐bonding moieties, was studied at ?135 °C in 2‐methyltetrahydrofuran (MeTHF). Kinetic stabilization of the H‐bonded [( TMPA)CuII(O2.?)]+ cupric superoxide species was achieved, and they were characterized by resonance Raman (rR) spectroscopy. The structures and physical properties of [( TMPA)CuII(N3?)]+ azido analogues were compared, and the O2.? reactivity of ligand–CuI complexes when an H‐bonding moiety is replaced by a methyl group was contrasted. A drastic enhancement in the reactivity of the cupric superoxide towards phenolic substrates as well as oxidation of substrates possessing moderate C?H bond‐dissociation energies is observed, correlating with the number and strength of the H‐bonding groups. 相似文献
193.
Zhang CX Liang HC Kim EI Shearer J Helton ME Kim E Kaderli S Incarvito CD Zuberbühler AD Rheingold AL Karlin KD 《Journal of the American Chemical Society》2003,125(3):634-635
Copper(I)-dioxygen adducts are important in biological and industrial processes. For the first time we explore the relationship between ligand electronics, CuI-O2 adduct formation and exogenous substrate reactivity. The copper(I) complexes [CuI(R-MePY2)]+ (1R, where R = Cl, H, MeO, Me2N) were prepared; where R-MePY2 are 4-pyridyl substituted bis[2-(2-pyridyl)ethyl]methylamine chelates. Both the redox potential of 1R (ranging from E1/2 = -270 mV for 1Cl to -440 mV for 1MeN vs FeCp2/FeCp2+) and nuCO of the CO adducts of 1R (ranging from 2093 cm-1 for 1Cl-CO to 2075 cm-1 for 1Me2N-CO) display modest but expected systematic shifts. Dioxygen readily reacts with 1H, 1MeO, and 1Me2N, forming the side-on peroxo-CuII2 complexes [{CuII(R-MePY2)}2(O2)]2+ (2R, also containing some bis-mu-oxo-CuIII2 isomer), but there is no reaction with 1Cl. Stopped-flow studies in dichloromethane show that the formation of 2Me2N from dioxygen and 1Me2N proceeds with a k = 8.2(6) x 104 M-2 s-1 (183 K, DeltaH = -20.3(6) kJ mol-1, DeltaS = -219(3) J mol-1 K-1). Solutions of 2R readily oxidize exogenous substrates (9,10-dihydroanthracene --> anthracene, tetrahydrofuran (THF) --> 2-hydroxytetrahydrofuran (THF-OH), N,N-dimethylaniline --> N-methylaniline and formaldehyde, benzyl alcohol --> benzaldehyde, benzhydrol --> benzophenone, and methanol --> formaldehyde), forming the bis-mu-hydroxo-CuII2 complexes [{CuII(R-MePY2)(OH)}2]2+ (3R). Product yields increase as the R-group is made more electron-donating, and in some cases are quantitative with 2Me2N. Pseudo-first-order rate constants for THF and methanol oxidation reactions demonstrate a remarkable R-group dependence, again favoring the strongest ligand donor (i.e., R = Me2N). For THF oxidation to THF-OH a nearly 1500-fold increase in reaction rate is observed (kobs = 2(1) x 10-5 s-1 for 2H to 3(1) x 10-2 s-1 for 2Me2N), while methanol oxidation to formaldehyde exhibits an approximately 2000-fold increase (kobs = 5(1) x 10-5 s-1 for 2H to 1(1) x 10-1 s-1 for 2Me2N). 相似文献
194.
Mechanistic Insight into the Nitric Oxide Dioxygenation Reaction of Nonheme Iron(III)–Superoxo and Manganese(IV)–Peroxo Complexes 下载免费PDF全文
Dr. Seungwoo Hong Dr. Pankaj Kumar Dr. Kyung‐Bin Cho Dr. Yong‐Min Lee Prof. Dr. Kenneth D. Karlin Prof. Dr. Wonwoo Nam 《Angewandte Chemie (International ed. in English)》2016,55(40):12403-12407
Reactions of nonheme FeIII–superoxo and MnIV–peroxo complexes bearing a common tetraamido macrocyclic ligand (TAML), namely [(TAML)FeIII(O2)]2? and [(TAML)MnIV(O2)]2?, with nitric oxide (NO) afford the FeIII–NO3 complex [(TAML)FeIII(NO3)]2? and the MnV–oxo complex [(TAML)MnV(O)]? plus NO2?, respectively. Mechanistic studies, including density functional theory (DFT) calculations, reveal that MIII–peroxynitrite (M=Fe and Mn) species, generated in the reactions of [(TAML)FeIII(O2)]2? and [(TAML)MnIV(O2)]2? with NO, are converted into MIV(O) and .NO2 species through O?O bond homolysis of the peroxynitrite ligand. Then, a rebound of FeIV(O) with .NO2 affords [(TAML)FeIII(NO3)]2?, whereas electron transfer from MnIV(O) to .NO2 yields [(TAML)MnV(O)]? plus NO2?. 相似文献