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71.
Dr. Evanildo G. Lacerda Jr. Dr. Fadhil S. Kamounah Prof. Dr. Kaline Coutinho Prof. Dr. Stephan P. A. Sauer Prof. Dr. Poul Erik Hansen Prof. Dr. Ole Hammerich 《Chemphyschem》2019,20(1):78-91
Prediction of chemical shifts in organic cations is known to be a challenge. In this article we meet this challenge for α-protonated alkylpyrroles, a class of compounds not yet studied in this context, and present a combined experimental and theoretical study of the 13C and 1H chemical shifts in three selected pyrroles. We have investigated the importance of the solvation model, basis set, and quantum chemical method with the goal of developing a simple computational protocol, which allows prediction of 13C and 1H chemical shifts with sufficient accuracy for identifying such compounds in mixtures. We find that density functional theory with the B3LYP functional is not sufficient for reproducing all 13C chemical shifts, whereas already the simplest correlated wave function model, Møller–Plesset perturbation theory (MP2), leads to almost perfect agreement with the experimental data. Treatment of solvent effects generally improves the agreement with experiment to some extent and can in most cases be accomplished by a simple polarizable continuum model. The only exception is the NH proton, which requires inclusion of explicit solvent molecules in the calculation. 相似文献
72.
73.
A. Sauer 《Fresenius' Journal of Analytical Chemistry》1873,12(1):32-36
Ohne Zusammenfassung 相似文献
74.
75.
Löffler D Uhlrich JJ Baron M Yang B Yu X Lichtenstein L Heinke L Büchner C Heyde M Shaikhutdinov S Freund HJ Włodarczyk R Sierka M Sauer J 《Physical review letters》2010,105(14):146104
Thin SiO? films were grown on a Ru(0001) single crystal and studied by photoelectron spectroscopy, infrared spectroscopy and scanning probe microscopy. The experimental results in combination with density functional theory calculations provide compelling evidence for the formation of crystalline, double-layer sheet silica weakly bound to a metal substrate. 相似文献
76.
Salzmann W Mullins T Eng J Albert M Wester R Weidemüller M Merli A Weber SM Sauer F Plewicki M Weise F Wöste L Lindinger A 《Physical review letters》2008,100(23):233003
We demonstrate the photoassociation of ultracold rubidium dimers using coherent femtosecond pulses. Starting from a cloud of ultracold rubidium atoms, electronically excited rubidium molecules are formed with shaped photoassociation pump pulses. The excited state molecules are projected with a time-delayed probe pulse onto molecular ion states which are detected in a mass spectrometer. Coherent transient oscillations of the excited state population are observed in the wings of the pump pulse, in agreement with the time-dependent solution of the Schr?dinger equation of the excitation process. 相似文献
77.
The self-consistent modification of an inhomogeneous plasma density profile near the critical layer due to the ponderomotive force of an obliquely incident p-polarized electromagnetic wave is calculated within a simple hydrodynamic plasma model. 相似文献
78.
Shuo Li J. R. Fried Jeremy Sauer John Colebrook Douglas S. Dudis 《International journal of quantum chemistry》2011,111(12):3212-3229
Quantum mechanics (QM) calculations, molecular dynamics (MD) simulations using the condensed‐phase optimized molecular potentials for atomistic simulation studies (COMPASS) force field, and the atom‐centered density matrix propagation (ADMP) approach have been used to investigate properties of phosphoric acid (PA). QM using B3LYP/6‐31++G(d,p) density functional theory were used to calculate gas‐phase proton affinities and interaction energies of PA and its derivatives. Detailed single coordinate driving, followed by quadratic synchronous transit optimization was used to determine energy barriers for different proton transfer (PT) pathways. Determined energy barrier heights in ascending order are (unit: kJ/mol): H3O+→H3PO4 (0); H4P2O7→H3PO4 (2.61); H3PO4→H2PO (5.31); H4PO→H3PO4 (~7.33); H3PO4→H4P2O7/H3PO4→H3PO4 (15.99); H4P2O7→H2O (28.61); H3PO4→H2O (47.14). The COMPASS force field was used to study condensed‐phase properties of PA. Good agreement between experimental data and MD results including density, radial distribution functions, and self‐diffusion coefficient at different temperatures provides validation of the COMPASS force field for PA. Finally, preliminary ADMP studies on a cluster of three PA molecules shows that the ADMP approach can reasonably describe the PT and self‐dissociation processes in PA. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
79.
Thieuleux C Quadrelli EA Basset JM Döbler J Sauer J 《Chemical communications (Cambridge, England)》2004,(15):1729-1731
The silica-supported Zr(iv) dihydride [(triple bond)SiO)2ZrH2] reacts quickly and completely with methane to yield [(triple bond)SiO)2ZrMe2] through the intermediate [(triple bond)SiO)2ZrHMe], while its monohydride analogue [(triple bond)SiO)3ZrH] yields the monomethylated product [(triple bond)SiO)3ZrMe] slowly and incompletely. 相似文献
80.
Yano J Sauer K Girerd JJ Yachandra VK 《Journal of the American Chemical Society》2004,126(24):7486-7495
The anisotropic g and hyperfine tensors of the Mn di-micro-oxo complex, [Mn(2)(III,IV)O(2)(phen)(4)](PF(6))(3).CH(3)CN, were derived by single-crystal EPR measurements at X- and Q-band frequencies. This is the first simulation of EPR parameters from single-crystal EPR spectra for multinuclear Mn complexes, which are of importance in several metalloenzymes; one of them is the oxygen-evolving complex in photosystem II (PS II). Single-crystal [Mn(2)(III,IV)O(2)(phen)(4)](PF(6))(3).CH(3)CN EPR spectra showed distinct resolved (55)Mn hyperfine lines in all crystal orientations, unlike single-crystal EPR spectra of other Mn(2)(III,IV) di-micro-oxo bridged complexes. We measured the EPR spectra in the crystal ab- and bc-planes, and from these spectra we obtained the EPR spectra of the complex along the unique a-, b-, and c-axes of the crystal. The crystal orientation was determined by X-ray diffraction and single-crystal EXAFS (Extended X-ray Absorption Fine Structure) measurements. In this complex, the three crystallographic axes, a, b, and c, are parallel or nearly parallel to the principal molecular axes of Mn(2)(III,IV)O(2)(phen)(4) as shown in the crystallographic data by Stebler et al. (Inorg. Chem. 1986, 25, 4743). This direct relation together with the resolved hyperfine lines significantly simplified the simulation of single-crystal spectra in the three principal directions due to the reduction of free parameters and, thus, allowed us to define the magnetic g and A tensors of the molecule with a high degree of reliability. These parameters were subsequently used to generate the solution EPR spectra at both X- and Q-bands with excellent agreement. The anisotropic g and hyperfine tensors determined by the simulation of the X- and Q-band single-crystal and solution EPR spectra are as follows: g(x) = 1.9887, g(y) = 1.9957, g(z) = 1.9775, and hyperfine coupling constants are A(III)(x) = |171| G, A(III)(y) = |176| G, A(III)(z) = |129| G, A(IV)(x) = |77| G, A(IV)(y) = |74| G, A(IV)(z) = |80| G. 相似文献