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81.
Y. Nishiyama 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(4):547-554
To investigate the influence of electronic interaction on the metal-insulator transition (MIT), we consider the Aubry-André
(or Harper) model which describes a quasiperiodic one-dimensional quantum system of non-interacting electrons and exhibits
an MIT. For a two-particle system, we study the effect of a Hubbard interaction on the transition by means of the transfer-matrix
method and finite-size scaling. In agreement with previous studies we find that the interaction localizes some states in the
otherwise metallic phase of the system. Nevertheless, the MIT remains unaffected by the interaction. For a long-range interaction,
many more states become localized for sufficiently large interaction strength and the MIT appears to shift towards smaller
quasiperiodic potential strength.
Received 17 August 1998 相似文献
82.
Based on vertex configurations in the Ammann–Beenker tiling, we propose an algorithm for aggregation of square and rhombus tiles to generate an octagonal quasilattice, which mimics the growth process of a two-dimensional quasicrystal. Local matching rules with configuration selection are used to guide the way that tiles are joined to a cluster and form Ammann lines according to a generalized Fibonacci sequence. Our results reveal that vertex configuration selection can improve the performance of the algorithm, which provides an approach for growing a perfect octagonal quasiperiodic structure. 相似文献
83.
准晶是一种拥有长程序但不具有周期性结构的一种物质.实验上通过将玻色-爱因斯坦凝聚体(BEC)放置在一个由四个光学腔组成的系统中,通过四个腔中激光照射在凝聚体上从而得到具有八重旋转对称性的准晶.本文结合虚时演化方法和分步傅里叶法从理论上得到了八重准晶体.我们通过这种方法可以实现更为复杂的晶体结构,从而为将来探索新物质提供了可能. 相似文献
84.
A. Ghosh S. N. Karmakar 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(4):575-582
We present an exact real-space renormalization group (RSRG) scheme for the electronic Green's functions of one-dimensional
tight-binding systems having both nearest-neighbor and next-nearest-neighbor hopping integrals, and determine the electronic
density of states for the quasiperiodic Fibonacci chain. This RSRG method also gives the Lyapunov exponents for the eigenstates.
The Lyapunov exponents and the analysis of the flow pattern of hopping integrals under renormalization provide information
about the nature of the eigenstates. Next we develop a transfer matrix formalism for this generalized tight-binding system, which enables us to determine the wave function amplitudes.
Interestingly, we observe that like the nearest-neighbor tight-binding Fibonacci chain, the present generalized tight-binding
system also have critical eigenstates, Cantor-set energy spectrum and highly fragmented density of states. It indicates that
these exotic physical properties are really the characteristics of the underlying quasiperiodic structure.
Received 5 April 1999 相似文献
85.
The cohesive energy of the Al–Mn Mackay icosahedron (MI) was estimated for different variants of chemical order, using pair-bonding energies. This problem is related to the nucleation of i-AlMn phase in sequentially deposited thin films. The chemically ordered MI comes out as the thermodynamically most stable configuration. The role of kinetic factors during deposition is also discussed. 相似文献
86.
Yu.S. Ponosov 《Journal of Non》2011,357(3):1235-1238
We present the first Raman investigation of icosahedral quasicrystals. Broad structured bands in the energy range up to ~500 cm− 1 have been observed in a series of AlCuFe, AlPdMn and AlPdRe systems. Original information on the vibrational density of states g(ω) was obtained for AlPdRe; for AlCuFe and AlPdMn estimated g(ω) shows a good agreement with the previous neutron results, but demonstrates finer structure. Strong increase in the parameter of electron-vibrational coupling for the low-energy vibrations and its correlation with changes in electronic conductivity has been observed in the series from AlCuFe to AlPdRe. This suggests the increase of the degree of localization for these vibrational excitations and involved electronic states. 相似文献
87.
R. Teghil L. DAlessio A. Santagata M. Zaccagnino D. Ferro D. J. Sordelet 《Applied Surface Science》2003,210(3-4):307-317
A Nd:glass laser with pulse duration of 250 fs and 1.3 ps has been used to evaporate a Al65Cu23Fe12 quasicrystalline target. The gaseous phase obtained from the ablation process has been characterised by several techniques such as emission spectroscopy, quadrupole mass spectrometry and ICCD imaging, used to study the plume composition, energy and morphology. The results show that the ablation processes in the short-pulse regimes are very different to the nanosecond one. In particular the plume angular distribution shows a characteristic high cosine exponent and the composition is completely stoichiometric and independent from the laser fluence. Furthermore the mass spectra indicate the presence of clusters, both neutral and ionised and the emission from the target suggest a rapid thermalisation leading to the melting of the surface. To clarify the ablation process some films have been deposited, on oriented silicon, at different experimental conditions and analysed by scanning electron microscopy, atomic force microscopy, energy dispersive X-ray analysis and X-ray diffraction. The analyses show the presence of nanostructured films retaining the target stoichiometry but consisting of different crystalline and non crystalline phases. In particular the nanostructure supports the hypothesis of the melting of the target during the ablation and a mechanism of material ejection is proposed for both picosecond and femtosecond regimes. 相似文献
88.
Paolo Maria Mariano 《Physics letters. A》2010,375(2):80-83
It is proven that magnetizable quasicrystals undergoing large deformations admit elastic ground states characterized by a net of linear topological defects for the magnetic spin field. 相似文献
89.
Electron microscopic and differential scanning calorimetric (DSC) studies have been performed to investigate the phase transitions
in the rapidly solidified Al6CuMg4 alloy system. We present evidence, for the first time, that anendothermic quasicrystalline to crystalline transition occurs in this system around 340°C. This is an unexpected feature—for conventional
wisdom would lead one to expect exothermic behaviour as was seen in Al86Mn14—and points to the fact that stability of certain quasicrystalline phases may be much larger than hitherto expected. Some
comments on the recently reported large quasicrystal for the Al6CuLi3 system are also made in the light of our observation. 相似文献
90.
C. Ghosh 《Surface science》2006,600(10):2220-2230
Scanning tunneling microscopy experiments have previously revealed the formation of pseudomorphic starfish-shaped islands during the initial stages of Al deposition on 5-fold icosohedral Al-Cu-Fe quasicrystal surfaces. To simulate this process, we first identify appropriate 5-fold surface terminations of Al-Cu-Fe from a model for bulk structure, and construct associated potential energy surfaces for the binding of Al adatoms on these terminations. We then identify a ‘disordered-bond-network’ (DBN) connecting neighboring local adsorption sites for Al on Al-Cu-Fe, and determine site binding energies as well as activation barriers for Al adatom hopping between neighboring sites. Al-Al adsorbate interactions, which stabilize islands, are also prescribed. Then, within the framework of a DBN lattice-gas model, we simulate the deposition and diffusion of Al on Al-Cu-Fe. We explore the competition between starfish and incomplete starfish ensembles of sites (which provide traps in the form of deep potential energy wells for diffusing Al) and isolated trap sites, with regard to the heterogeneous nucleation and aggregation of Al into islands. 相似文献