全文获取类型
收费全文 | 399篇 |
免费 | 11篇 |
国内免费 | 12篇 |
专业分类
化学 | 46篇 |
晶体学 | 1篇 |
数学 | 19篇 |
物理学 | 356篇 |
出版年
2023年 | 6篇 |
2022年 | 3篇 |
2021年 | 1篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 35篇 |
2012年 | 18篇 |
2011年 | 50篇 |
2010年 | 37篇 |
2009年 | 40篇 |
2008年 | 30篇 |
2007年 | 20篇 |
2006年 | 18篇 |
2005年 | 5篇 |
2004年 | 8篇 |
2003年 | 9篇 |
2002年 | 29篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1979年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有422条查询结果,搜索用时 31 毫秒
21.
22.
Esmeralda Lizet Martinez Piñeiro Roberto Escudero Lauro Bucio 《Solid State Communications》2011,151(6):425-429
NiBi3 polycrystals were synthesized via a solid state method. X-ray diffraction analysis shows that the main phase present in the sample corresponds to NiBi3 in a weight fraction of 96.82 % according to the refinement of the crystalline structure. SEM - EDS and XPS analysis reveal a homogeneous composition of NiBi3, without Ni traces. The powder superconducting samples were studied by performing magnetic measurements. The superconducting transition temperature and critical magnetic fields were determined as , Oe and Oe. The superconducting parameters were , , and κ=5.136. Isothermal measurements below the transition temperature show an anomalous behavior. Above the superconducting transition the compound presents ferromagnetic characteristics up to 750 K, well above the Ni Curie temperature. 相似文献
23.
The movement of vortices in superconductors due to an applied current can induce a loss of perfect conductivity. Experimental observations show that material impurities can effectively prevent vortices from moving. In this paper, we provide numerical studies to investigate vortex pinning and critical currents through the use of an optimal control approach applied to a variant of the time-dependent Ginzburg-Landau model that can account for normal inclusions. The effects that the size and boundary of the sample and the number, size, shape, orientation, and location of the inclusion sites have on the critical current and vortex lattices are studied. In particular, the optimal control approach is used to determine the optimal properties of the impurities so as to maximize the critical current, i.e., the largest current that can pass through a superconductor without resistance. 相似文献
24.
Neutron scattering has been used to measure the charge and spin structure in the YBa2Cu3O6+x superconductors. Incommensurate static charge ordering is found at low doping levels while only charge fluctuations are found at higher doping. The spin structure is complex with both a commensurate resonance and incommensurate structure observed at low temperatures. The scattering results are used to construct a phase diagram for stripes in the YBa2Cu3O6+x system. 相似文献
25.
E.W. Carlson D. OrgadS.A. Kivelson V.J. Emery 《Journal of Physics and Chemistry of Solids》2002,63(12):2213-2218
Although structurally the high temperature superconductors are quasi-two-dimensional, there is both theoretical and experimental evidence of a substantial range of temperatures in which ‘stripe’ correlations make the electronic structure locally quasi-one-dimensional. We consider an array of Josephson coupled, spin gapped one dimensional electron gases as a model of the high temperature superconductors. For temperatures above Tc, this system exhibits electron fractionalization, yielding a single particle spectral response which is sharp as a function of momentum, but broad as a function of energy. For temperatures below the spin gap but above Tc, there are enhanced one-dimensional superconducting fluctuations and pseudogap phenomena. Pair tunneling induces a crossover to three-dimensional physics as Tc is approached. Below Tc, solitons are confined in multiplets with quantum numbers which are simply related to the electron, and a coherent piece of the single particle spectral function appears. The weight of this coherent piece vanishes in the neighborhood of Tc in proportion to a positive power of the interchain superfluid density. This behavior is highly reminiscent of recent ARPES measurements on the high temperature superconductors. 相似文献
26.
We examine the possible electron-phonon spectra that produce both Tc=39 K and an isotope coefficient β=0.32±0.01, with Eliashberg theory. We assess the viability of the conventional electron-phonon mechanism in light of these results, compared with ab initio calculations of the electron-phonon spectrum. Comparisons are made with similar considerations for low Tc materials. 相似文献
27.
We construct a family of spin chain Hamiltonians, which have the affine quantum group symmetry
. Their eigenvalues coincide with the eigenvalues of the usual spin chain Hamiltonians, but have the degeneracy of levels, corresponding to the affine
. The space of states of these spin chains is formed by the tensor product of the fully reducible representations of the quantum group.
The fermionic representations of the constructed spin chain Hamiltonians show that we have obtained new extensions of the Hubbard Hamiltonians. All of them are integrable and have the affine quantum group symmetry. The exact ground state of such type of model is presented, exhibiting superconducting behavior via the η-pairing mechanism. 相似文献
28.
The crystallographic and electronic structures of compounds related to parkerite (Bi2Ni3S2) are investigated with respect to the recently reported occurrence (Bi2Pd3Se2) and absence (Bi2Pd3S2) of superconductivity. Similarities and differences of the crystal structures are discussed within the series of solid solutions Bi2Pd3S2−xSex from powder and single crystal diffraction data. From crystal structure refinements, the question of different structures and settings of parkerite is discussed. Similar and different 2D and 3D partial Pd-Ch (Ch=S, Se) structures are related to half antiperovskite ordering schemes. To investigate the relation of low dimensional structures and the occurrence of superconductivity, electronic structures are analyzed by scalar-relativistic DFT calculations, including site projected DOS, ECOV and Fermi surfaces. 相似文献
29.
Among heavy-fermion (HF) superconductors, CeCoIn 5 exhibits a record high value of T c =2.3 K at ambient pressure [1]. CeCoIn 5 belongs to a new class of HF-superconductors that crystallize in the tetragonal HoCoGa 5 -structure. This structure can be regarded as alternating layers of CeIn 3 and CoIn 2 . Bulk CeIn 3 undergoes a transition from an antiferromagnetic (AFM) state at ambient pressure ( T N =10.2 K) to a superconducting state with very low T C =0.15 K at a critical pressure p c =2.8 GPa [2] at which long range magnetic order vanishes. It is, therefore, regarded as a possible candidate for magnetically mediated superconductivity (SC). We report on measurements of the heat capacity of CeCoIn 5 at hydrostatic pressures p h 1.5 GPa. While T c increases with increasing pressure, the effective mass of the quasi-particles m eff decreases, as indicated by the ratio C / T | T c . As a working hypothesis based on theories of a nearly antiferromagnetic Fermi-liquid (NAFFL), this may be interpreted as the stabilization of the superconducting state by an increase of the characteristic spin fluctuation temperature T_{SF} (T_{SF}\propto k_F^2/m_{\rm eff}). 相似文献
30.
Lattice dynamics and electron-phonon coupling are calculated for non-magnetic hcp iron at 100 GPa by a first-principles linear response full-potential LMTO method. Superconducting transition temperature is estimated to be less than 0.5 K. For ferromagnetic bcc iron lattice dynamical calculations are performed for 9.8 GPa as well as for ambient pressure. The results of calculation reproduce well the pressure dependence of phonon dispersion curves observed by neutron scattering measurements. 相似文献