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91.
F.J. López-Rodríguez 《哲学杂志》2013,93(21):2977-2988
We study the energy spectrum for the problem of graphene's carriers under perpendicular incidence of electromagnetic waves. To obtain the spectrum, we solve the Dirac equation under such a field. Then a generalized Mathieu equation is obtained. The limiting cases of strong and weak fields, as well as long and short wavelengths, are analyzed. The energy spectrum is obtained numerically by using the Whittaker method, and a perturbation method is used to obtain the analytical separatrix curve between allowed and forbidden states. The energy spectrum presents bands, and a gap at the Fermi energy. The gap is linear on the electromagnetic wave intensity. 相似文献
92.
Wei-Long Zhang Chen-Sheng Lin Ye-Yu Li Hao Zhang Wen-Dan Cheng 《Journal of solid state chemistry》2010,183(5):1108-1113
Two members of MIII2BP3O12 borophosphates, namely Fe2BP3O12 and In2BP3O12, were synthesized by the solid-state method and characterized by the X-ray single crystal diffraction, the powder diffraction and the electron microscopy. They both crystallize in the hexagonal system, space group P6(3)/m (no. 176) and feature 3D architectures, build up of the M2O9 units and B(PO4)3 groups via sharing the corners; however, they are not isomorphic for the different crystallographically distinct atomic positions. Optical property measurements of both compounds and magnetic susceptibility measurements of Fe2BP3O12 also have been performed. Moreover, in order to gain further insights into the relationship between physical properties and band structure of the MIII2BP3O12 borophosphates, theoretical calculations based on density functional theory (DFT) were performed using the total-energy code CASTEP. 相似文献
93.
S. Ben Rejeb A. Bhouri M. Debbichi J.-L. Lazzari M. Said 《Superlattices and Microstructures》2011,50(4):277-288
Reliable and precise knowledge about the strain and composition effects on the band structure properties is crucial for the optimization of InGaN based heterostructures for electronic and optoelectronic device applications. AlInGaN as quaternary barrier material permits to control the band gap and the lattice constant independently. Using the model solid theory and the multi-band k.p interaction model, we investigate the composition effects on band offsets and band structure for pseudomorphic Ga1−xInxN/AlzInyGa1−y−zN (0 0 1) heterointerfaces having zinc-blende structure. The results show that both conduction and valence band states are strongly modified while varying In and Al contents in the well and barrier materials. Furthermore, it is found that using AlInGaN as the barrier material allows the design of heterostructures including InGaN wells with tensile, zero or compressive strain. Such results give new insights for III-nitride compounds based applications and especially may guide the design of white-light emission diodes. 相似文献
94.
S. BachaA. Bechiri F. BenmakhloufH. Allouache N. Bouarissa 《Physica B: Condensed Matter》2011,406(10):2021-2024
The investigation of optoelectronic properties of zinc-blende InPxSb1−x, semiconducting alloys by pseudopotential calculations is studied. The scheme uses the local empirical pseudopotential method, which involves the disorder effect into the virtual crystal approximation by introducing an effective potential disorder. Various quantities for the alloy of interest are calculated. The obtained results show a reasonable agreement with the available experimental data. Special attention has also been given to the compositional dependence of these studied quantities. 相似文献
95.
A. Montorsi 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):419-422
We investigate under which circumstances extended Hubbard models, including bond-charge, exchange, and pair-hopping terms,
are invariant under gl
(2,1) superalgebra. This happens for a two-parameter Hamiltonian which includes as particular cases the t
-
J, the EKS and the one-parameter BGLZ Hamiltonians, all integrable in one dimension. We show that the two parameter Hamiltonian
can be recasted as the sum of the BGLZ Hamiltonian plus the graded permutation operator of electronic states on neighbouring
sites. The integrability of the corresponding one-dimensional model is discussed.
Received: 17 February 1998 / Received in final form: 6 March 1998 / Accepted: 17 April 1998 相似文献
96.
Experimental evidence proving the unique stabilization of the 6s orbital in platinum and gold is presented. The conclusions are drawn from the chemical reactivities, of both elements, as well as from structural and spectroscopic features of selected compounds. In particular, the opening of a band gap in transparent CsAu and Cs2Pt, backed by band structure calculations, are regarded conclusive indications of Au− and Pt2− to exist as closed shell species in these compounds. 相似文献
97.
The diamagnetic susceptibility (DMS) of quasi-two-dimensional graphites (QTDGs) and multiwall carbon nanotubes (MWCNs) was measured at 4–950 K. The DMS of these carbons was explained by means of the band model of QTDG. The high average DMS value of QTDGs and MWCNs is associated with DMS normal to graphene sheets: the orbital diamagnetism of 2D conduction carriers. The DMS values along the sheets and nanotubes axes are close to the atomic one, i.e. they are 2 orders of magnitude less than those normal to the sheets and to MWCNs axes. 相似文献
98.
Photonic crystal structures (PCs) of tetragonal lattice type are introduced and studied. They feature complete three-dimensional (3D) photonic bandgaps (PBGs). The PC design is based on two systems of ordered, parallel pores being perpendicular to each other. For increasing pore radii, the pore systems interpenetrate and an inverted woodpile geometry arises. The size of the 3D bandgaps depends on the ratio of the cell parameters Lx, Ly, and Lz, the pore radii and the refractive index of the dielectric material. If realized as a silicon/air structure, the maximum 3D gap is larger than 25%. A possible fabrication route for the near-infrared is based on 2D macroporous silicon where perpendicular pores are drilled, e.g., by focused-ion-beam etching. The dispersion behaviour of the PCs is theoretically analysed (band structures, density-of-states), systematically varying all relevant parameters. The optimization of the PBG sizes as well as a possible tunability of the PBG energies are discussed. 相似文献
99.
李春霞 《原子与分子物理学报》2007,24(5):1060-1064
基于密度泛函理论(DFT)的第一性原理方法(DMOL3程序),在广义梯度近似(GGA)下,计算了中小尺寸II~VI族(CdS)n和(CdTe)n团簇的基态结构、最高占据轨道(HOMO)和最低未占据轨道(LUMO)的能隙、结合能等,比较了(CdS)n和(CdTe)n两种团簇的基态结构,能隙与结合能随尺寸变化关系的差异等. 相似文献
100.
For group III-nitrides with wurtzite structure the presence of fixed polarization interface charges yields new challenges in order to understand and control Schottky barrier heights, band offsets and 2D confinement in heterostructure FETs. In this short review experimental results obtained by in situ photoemission spectroscopy on MBE AlGaN/GaN heterostructures grown on 6H–SiC are discussed, with emphasis on the presence and interplay of surface electronic states. Schrödinger–Poisson calculations are performed to get the complete band scheme at the selected heterojunctions. Results on the polarity dependence of Pt/GaN Schottky barrier values from the literature are also discussed. 相似文献