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91.
J. Kurzyk W. Wójcik J. Spałek 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(3):385-398
The method used earlier for analysis of correlated nanoscopic systems is extended to infinite (periodic) s-band-like systems
described by the Hubbard model. The optimized single-particle Wannier wave functions contained in the parameters of the extended
Hubbard model (in the nearest-neghbor hopping (-t), in the magnitude of the intraatomic interaction U, and in other parameters) are determined explicitly in the correlated state for the electronic systems of various symmetries
and dimensions: Hubbard chain, square and triangular planar lattices, and the three cubic lattices (SC, BCC, FCC). In effect,
the evolution of the electronic properties as a function of interatomic distance R is obtained. The model parameters in most
cases do not scale linearly with the lattice spacing and hence, their solution as a function of microscopic parameters reflects
only qualitatively the system evolution. Also, the atomic energy changes with R and therefore should be included in the model
analysis. The solutions in one dimension (D = 1) can be analyzed both rigorously (by making use of the Lieb–Wu solution) and compared with the approximate Gutzwiller
treatments. In higher dimensions (D = 2 and 3) only the latter approach is possible to implement within the scheme. The renormalized single particle wave functions
are almost independent of the choice of the scheme selected to diagonalize the Hamiltonian in the Fock space in D = 1 case.
For dimensions D > 1 the qualitative behavior is independent of the structure considered. The wave-function size increases
above the Mott-Hubbard localization threshold and gradually reaches the atomic limit value. The method can be extended to
other approximation schemes, as stressed at the end. 相似文献
92.
We employ density functional theory with Hubbard U correction or hybrid functionals to study the series of magnetic 3d metal trifluorides MF3 (M = Ti-Ni). Experimental lattice parameters are reproduced with an error margin of 0.5%–4.3%. Cooperative Jahn–Teller distortions are reproduced for MnF3, but also found in TiF3 and CoF3 at smaller levels compared to MnF3. Trends in electronic structure with respect to positions of the d bands are linked to the magnetic properties where M = Ti-Cr are weak magnetic Mott–Hubbard insulators, M = Fe-Ni are strong magnetic charge-transfer insulators and MnF3 falls in between. Our work contributes to the characterization of the relatively unknown NiF3, since FeF3 and CoF3 have similar electronic and magnetic properties. However, NiF3 does not show a Jahn–Teller distortion as present in CoF3. © 2019 Wiley Periodicals, Inc. 相似文献
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96.
《International journal of quantum chemistry》2018,118(6)
A new evolutionary algorithm for stochastic configuration interaction (CI) method designed as an affordable approximation to full configuration interaction (FCI) has been described here. The key components of the algorithm are initiation, propagation, and termination steps taking inspiration from the genetic algorithm. The propagation step is performed with cloning (retention of a Slater determinant without change), mutation (single excitation/de‐excitation), and crossover (exchange of α and β strings between two Slater determinants) and termination is selection of few Slater determinants based on certain fitness function (measure of importance of a determinant in the CI space) and rejection of the rest. We find that the absolute value of the CI coefficients is a suitable fitness function when combined with a fixed selection scheme. We have tested its accuracy in 1D Hubbard problem and ground state potential energy surface (PES) has also been constructed for symmetric bond breaking of water molecule, where the errors are found to be around 10 mEh with low non‐parallelity error, when retaining only a small fraction of the total number of Slater determinants in the final population. This shows that this method has the ability to capture both static and dynamic correlation. Performance and convergence properties of the algorithm are also tested for N2 triple bond breaking problem. The algorithm opens up a promising way for stochastic sampling of the important determinants in the full Hilbert space. 相似文献
97.
T. Ishikawa S. Yamashita Y. Nakazawa A. Kawamoto M. Oguni 《Journal of Thermal Analysis and Calorimetry》2008,92(2):435-438
Thermodynamic investigation of an organic superconductor κ-(BEDT-TTF)2Ag(CN)2H2O in which the BEDT-TTF dimers are arranged in the κ-type structure in the donor layers is performed by the relaxation calorimetric
technique at low temperatures and under magnetic fields. A thermal anomaly related to the superconductive phase transition
was observed at 5 K. The existence of residual γ* in the superconductive state is about 18% of the normal state γ value, which is larger than those of κ-(BEDT-TTF)2Cu(NCS)2, and κ-(BEDT-TTF)2Cu[N(CN)2]Br salt. The lattice heat capacity reflected on the β-term in the low-temperature heat capacity was found to be affected
by the cooling rate. The disorder produced in the network structure constructed by hydrogen bond in the insulating layer is
considered to give low-energy phonon excitations reflected in the heat capacity. 相似文献
98.
基于CASSCF参考函数的块相关耦合簇方法对烷烃中单键解离势能面研究 总被引:1,自引:0,他引:1
用以完全活化空间自洽场(CASSCF)波函数为参考波函数的块相关耦合簇(BCCC)方法(简称CAS-BCCC)研究了烷烃(甲烷和乙烷)中的单键解离过程的势能面(PES). 与其它理论方法比较的结果表明, 该方法可以对所研究的整个解离势能面给出定量准确的描述. 相似文献
99.
Prof. Dr. Mingoo Jin Satsuki Matsuura Hikaru Yamamoto Prof. Dr. Motohiro Mizuno Prof. Dr. Hajime Ito 《European journal of organic chemistry》2023,26(12):e202201468
We report multidynamic molecular rotations in crystals using a concave-shape N-heterocyclic carbene (NHC) binuclear Au(I) complex rotor bearing pyrazine and tetrahydrofuran (THF) molecules as multicomponent rotators. Single-crystal X-ray diffraction (XRD) measurements revealed that two THF molecules are located near the central pyrazine encapsulated by two bulky NHC ligands. From 2H solid-state NMR analysis, it was observed that the pyrazine rotated in a 2-fold site exchange with a 180° rotational angle and a 31 kJ mol−1 energy barrier, while the THF molecules showed a 23°-38° libration with a lower energy barrier (14 kJ mol−1). Interestingly, the pyrazine rotation was accelerated when the THF molecules rotated in fast site exchange with a large angle of libration, suggesting that the rotators exhibit multidynamics in a correlated manner. 相似文献
100.
V. Balédent 《高压研究》2016,36(3):371-380
ABSTRACTWe report here on the application of Resonant Inelastic X-ray Scattering (RIXS) in correlated electrons systems under pressure. Thanks to its bulk sensitivity and superior resolving power, RIXS appears as a powerful spectroscopic technique to unravel the local electronic and magnetic properties of materials at extreme conditions. The method is illustrated in vanadium-oxides- and Fe-based superconductors at high pressure. 相似文献