全文获取类型
收费全文 | 177篇 |
免费 | 18篇 |
国内免费 | 8篇 |
专业分类
化学 | 25篇 |
数学 | 7篇 |
物理学 | 171篇 |
出版年
2021年 | 3篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 13篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 3篇 |
2009年 | 14篇 |
2008年 | 23篇 |
2007年 | 16篇 |
2006年 | 20篇 |
2005年 | 8篇 |
2004年 | 4篇 |
2003年 | 17篇 |
2002年 | 13篇 |
2001年 | 13篇 |
2000年 | 15篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1988年 | 1篇 |
1978年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有203条查询结果,搜索用时 15 毫秒
11.
J. A. H. Coaquira H. R. Rechenberg C. Marquina M. R. Ibarra A. M. Benito W. Maser E. Muñoz M. T. Martínez 《Hyperfine Interactions》2001,134(1):103-108
Iron particles encaged in carbon nanocapsules have been produced by the Krätschmer–Huffmann carbon-arc discharge method. Soot, collarette and cathode samples have been characterized by Mössbauer spectroscopy and magnetic measurements in the temperature range 4.2–300 K. Different iron phases and iron-carbon solid solutions have been detected in our samples. The Einstein model has been used to evaluate the coupling constant between the particles and their environment, yielding values of the order 1–10 N/m. Irreversibilities observed at ZFC and FC curves for soot samples would suggest the presence of superparamagnetism only if the particles presented a blocking temperature above 300 K. 相似文献
12.
The present paper focuses on the renormalization effects of the band gaps in the electronic band structure of the elemental semiconductors traced to zero-point vibrations. Electron-phonon interaction and volume changes (in combination with anharmonicity) are the underlying microscopic mechanisms, both dependent on M−1/2, M being the average isotopic mass. Thus isotopically controlled crystals offer an extraordinary opportunity to test the theoretical predictions with a variety of spectroscopic techniques. The paper discusses the theoretical predictions and their experimental verifications, exploiting derivative and photoluminescence spectroscopy. Illustrative examples on Si and Ge, drawn from the investigations of the authors, are presented. 相似文献
13.
C. Grimaldi L. Pietronero M. Scattoni 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(2):247-255
In the theory of nonadiabatic superconductivity several features are governed by the electron-phonon vertex correction which
has a complex structure both in momentum and frequency. We derive a physical interpretation of such nonadiabatic effects that
permits to link them to specific material properties. We show how the nonadiabatic vertex correction can be decomposed into
two terms with different physical origins. In particular, the first term describes the lattice polarization induced by the
electrons and it is essentially a single-electron process whereas the second term is governed by the particle-hole excitations
due to the exchange part of the phonon-mediated electron-electron interaction. We show that by weakening the influence of
the exchange interaction the vertex takes mostly positive values giving rise to an enhanced effective coupling in the scattering
with phonons. This weakening of the exchange interaction can be obtained by lowering the density of the electrons, or by considering
only long-ranged (small q) electron-phonon couplings.
Received 23 November 1998 and Received in final form 22 January 1999 相似文献
14.
J.-J. Shi B.C. Sanders S.-H. Pan 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(1):113-119
We calculate the electron-phonon scattering rate for an asymmetric double barrier resonant tunneling structure based on dielectric
continuum theory, including all phonon modes, and show that interface phonons contribute much more to the scattering rate
than do bulk-like LO phonons for incident energies which are approximately within an order of magnitude of the Fermi energy.
The maximum scattering rate occurs for incident electron energies near the quantum well resonance. Subband nonparabolicity
has a significant influence on electron-phonon scattering in these structures. We show that the relaxation time is comparable
to the dwell time of electrons in the quantum well for a typical resonant tunneling structure.
Received: 23 December 1997 / Revised: 24 March 1998 / Accepted: 9 March 1998 相似文献
15.
16.
R. Abd-Shukor 《Solid State Communications》2007,142(10):587-590
The electron-phonon coupling constant in two-dimensional cuprate high temperature superconductors has been determined by the ultrasonic method. The electron-phonon coupling constant in the Van Hove scenario was found to increase with transition temperature Tc. is in the range of 0.025-0.060 which is 10-100 times smaller than the conventional three-dimensional Bardeen-Cooper-Schrieffer coupling constant. The characteristic Debye temperature θD does not correlate with Tc. These findings show that the interplay between the Debye frequency and electron-phonon coupling in the two-dimensional system and their variations have a combined effect in governing the transition temperature. 相似文献
17.
In a photorefractive liquid crystal light valve, acting as a Kerr-like nonlinear optical medium, we show the appearance of optical patterns induced by a single mirror feedback. The spatial wavelength of the patterns scales with the distance between the mirror and the valve and the contrast of the patterns decreases for decreasing this distance. We use these properties to setup a new optical scheme for the measurement of the spatial resolution of the nonlinear device. 相似文献
18.
Chen Yijiang 《Applied physics. B, Lasers and optics》1988,45(1):21-25
Picosecond pump and probe experiments were carried out on fully oriented transpolyacetylene. Exciting the sample at 527 nm, photoinduced bleaching and absorption were observed at 527 nm and 1054 nm, respectively. The measurements give an upper limit of 2 ps for the relaxation time of the photogenerated 0.5 eV hot carriers to the band edges. The evaluation of the measured optical processes strongly suggests the conclusion that photoinduced structural distortions of the polyacetylene chain result in observable transient decrease of the interband absorption. This may be ascribed to the reduction of the density of electronic states and to that of the interband transition matrix element of the momentum operator. 相似文献
19.
对He,Ne,Ar,Kr和Xe原子体系中电子在动量空间的性质进行了系统的理论计算研究.采用自洽场HFR方法计算了坐标空间He,Ne,Kr和Xe原子体系单电子径向波函数,动量空间的单电子波函数由坐标空间原子体系单电子径向波函数通过运用傅立叶变换计算得到.在冲量近似条件下,进一步计算研究了这些原子的单电子动量密度分布和原子体系总的Compton轮廓.计算结果与已有的实验实验值和其他文献的理论计算结果比较表明,本文计算的结果是准确的. 相似文献
20.