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91.
We present a class of exact ground states of a three-dimensional periodic Anderson model at 3/4 filling. Hopping and hybridization of d and f electrons extend over the unit cell of a general Bravais lattice. Employing novel composite operators combined with 55 matching conditions the Hamiltonian is cast into positive semidefinite form. A product wave function in position space allows one to identify stability regions of an insulating and a conducting ground state. The metallic phase is a non-Fermi liquid with one dispersing and one flat band. 相似文献
92.
Sakhabutdinova Gul’nur N. Raskil’dina Gul’nara Z. Baikova Irina P. Zlotskii Simon S. Sultanova Rimma M. 《Chemistry of Heterocyclic Compounds》2019,55(12):1222-1227
Chemistry of Heterocyclic Compounds - The reaction of substituted 1,3-oxathiolanes with diazocarbonyl compounds in the presence of Cu(OTf)2 and Rh2(OAc)4 was studied. The reaction is accompanied by... 相似文献
93.
Shakeel Sadia Gul Somia Zahoor Aqib Khan Saleha Suleman Sheikh Zeeshan Ahmed Naveed Safila Usmanghani Khan 《平面色谱法杂志一现代薄层色谱法》2015,28(5):386-390
JPC – Journal of Planar Chromatography – Modern TLC - The technological improvement in the structural elucidation of natural compounds has made it probable to generate appropriate... 相似文献
94.
95.
Magnetic and electronic structure calculations are carried out for hypothetical zinc-blende (zb) phase of FeX (X=P, As, Sb) by using the full-potential linearized augmented plane wave (FLAPW) method. For zb FeSb, the total energy has been calculated as a function of lattice constant in ferromagnetic (FM) and antiferromagnetic (AFM) states. We found that the ground state of zb FeSb is very stable with respect to compression and expansion of the unit cell. The magnetic moment of zb FeSb in the AFM state is increasing with the lattice constant. The magnetic and electronic structures calculations of FeAs (FeP) are carried out for the lattice constants of GaAs (GaP), InAs (InP), and Si. Our finding shows that AFM is the ground state for all of our calculated zb FeX compounds and do not belong to the class of zb half metallic ferromagnets. 相似文献
96.
97.
Many theoretical works discuss the magnetic properties of the strongly repulsive Hubbard model near half filling. Several authors suggest that the system which contains a few holes does not behave as a ferromagnet, unlike in the one-hole case described by Nagaoka's famous result. We discuss the finite temperature properties of finite lattices. Using an efficient Monte Carlo method magnetic and specific heat results are presented for a 10 by 10 lattice with two holes. Our results show that the magnetization increases with decreasing temperature for such a finite system. 相似文献
98.
99.
In this work, a fluid model has been applied to study HBr/Ar capacitively coupled plasma discharges that are being used for anisotropic etching process. Based on time average reaction rates, the model identify the most dominant species in HBr/Ar plasma. Our simulation results show that the neutral species like H and Br, which are the key precursors in chemical etching, have bell shape distribution while ions like HBr+, Br+ and Ar+ which plays a dominant role in the physical etching, have double humped distribution and shows peaks near electrodes. The effect of HBr/Ar mixing ratios on densities of dominant species are analyzed. The addition of Ar to HBr plasma decreases H, Br and HBr+ densities slightly while increases Br+ and Ar+ densities. It was found that the dilution of HBr by Ar results in an increase in electron density and electron temperature, which results in more ionization and dissociation. The densities and hence the fluxes of the neutrals and positive ions for etching and subsequently chemical etching versus physical etching in HBr/Ar plasmas discharge can be controlled by tuning Ar concentration in the discharge and the desire etching can be achieved. 相似文献
100.
Br-based plasmas potentially provide selective etching of Si. The characteristics of homogenous discharge in mixed gases of HBr and He are investigated numerically based on a self-consistent 2D fluid model. The model takes into account the primary processes like excitation and ionization. The reactions of radicals with radicals, neutrals with neutrals and radicals and neutrals are taken into account in HBr/He discharge and therefore can adequately represent discharge plasma. Based on simulation results of the self-consistent 2D fluid model, the dominant species for Si etching in HBr/He plasma discharge are Br, Br+, H and HBr+. The impact of frequency, voltage, electrode gap, and gas mixture ratio on the densities of these important species in HBr/He has been explored. Simulation results indicate that elevating high frequency electrode’s frequency and voltage, enhances etching species densities. Increasing the electrode gap, the densities of all plasma species decrease and vice versa. The addition of He to HBr plasma decreases Br and HBr+ densities while increases Br+ density. Densities of active species for Si etching and subsequently chemical etching versus physical sputtering in HBr/He plasma can be controlled by tuning input parameters and the desired etching can be achieved. 相似文献