全文获取类型
收费全文 | 171篇 |
免费 | 3篇 |
专业分类
化学 | 129篇 |
力学 | 6篇 |
数学 | 9篇 |
物理学 | 30篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 23篇 |
2012年 | 10篇 |
2011年 | 22篇 |
2010年 | 13篇 |
2009年 | 12篇 |
2008年 | 6篇 |
2007年 | 12篇 |
2006年 | 4篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1985年 | 2篇 |
排序方式: 共有174条查询结果,搜索用时 15 毫秒
11.
Haddad S Charfi-Kaddour S Nickel C Héritier M Bennaceur R 《Physical review letters》2002,89(8):087001
A model is presented for the high field phase diagram of (TMTSF)(2)ClO(4), taking into account the anion ordering, which splits the Fermi surface into two bands. For strong enough field, the largest metal spin density wave critical temperature corresponds to the N=0 phase, which originates from two intraband nesting processes. At lower temperature, the competition between these processes puts at disadvantage the N=0 phase vs the N=1 phase, which is due to interband nesting. A first order transition then takes place from the N=0 to N=1 phase. We ascribe to this effect the experimentally observed phase diagrams. 相似文献
12.
M. Triki D. Elmaghraoui S. Jaziri R. Bennaceur 《Solid State Communications》2010,150(43-44):2197-2200
Using a numerical method via the electron effective mass theory, a model of a quantum ring (QR) with a shape very close to the real one and taken from an experimental work, we investigate the electron states in a semi-conductor QR, studying the influence of the ring’s geometrical parameters on the electron spectrum and on the optical transitions. Our hetero structure evolves from a single quantum dot (QD) to a QR. We find that the one-electron ground state presents an absolute minimum when studied as a function of the ring radius. The reliability of the calculations is checked with experimental data. 相似文献
13.
From a quantum collective approach, the momentum relaxation time, through both electron-electron and electron-ion interactions, is obtained based on electron wave functions interacting with the continuum oscillations (plasma waves). The theoretical model presented gives a consistent and complete set of transport coefficients for a dense magnetized plasma. This unified scheme of long- and short-range interactions gives conductivity formulas which are free from the usual Debye length, which loses its physical meaning as an upper impact parameter for relatively high-density, coupled plasma. 相似文献
14.
Stability analysis of jointed rock slope 总被引:2,自引:0,他引:2
The stability analysis of a jointed rock slope with two sets of unfilled joints, under its own weight, is carried out directly by considering failure surfaces along some particular joints and also going through the intact rock. Simple failure mechanisms using uniform rigid rock-block motions are incorporated in the yield design kinematic approach. They yield an improvement of known results as long as the characteristics strength of the joints are weak enough. 相似文献
15.
Lelli M Gajan D Lesage A Caporini MA Vitzthum V Miéville P Héroguel F Rascón F Roussey A Thieuleux C Boualleg M Veyre L Bodenhausen G Copéret C Emsley L 《Journal of the American Chemical Society》2011,133(7):2104-2107
We demonstrate fast characterization of the distribution of surface bonding modes and interactions in a series of functionalized materials via surface-enhanced nuclear magnetic resonance spectroscopy using dynamic nuclear polarization (DNP). Surface-enhanced silicon-29 DNP NMR spectra were obtained by using incipient wetness impregnation of the sample with a solution containing a polarizing radical (TOTAPOL). We identify and compare the bonding topology of functional groups in materials obtained via a sol-gel process and in materials prepared by post-grafting reactions. Furthermore, the remarkable gain in time provided by surface-enhanced silicon-29 DNP NMR spectroscopy (typically on the order of a factor 400) allows the facile acquisition of two-dimensional correlation spectra. 相似文献
16.
The change in the activity of glucose oxidase subjected to an asymmetrical alternating current (AC) electric field is investigated via horseradish peroxidase (HRP)‐coupled bioassay. The effect of the amplitude, frequency and enzyme concentration have been shown to affect the enzyme activity towards glucose oxidation. The decrease in the enzyme activity is directly related to the change in pH and temperature of the GOx solution during AC electrolysis. The enzyme activity reduces with increasing amplitude, enzyme concentration and decreasing frequency. Results from UV‐vis, FT‐IR and UV CD spectroscopy showed that the AC treated GOx samples undergo structural modifications. 相似文献
17.
On the Reactivity of (−)‐(R)‐Carvone and (−)‐4aα,7α,7aβ‐Nepetalactone: Synthesis of New Heterocycles
Aziz El Mebtoul Mohamed Rouani Malika Chammache Houcine Bouidida Abdelkader Ilidrissi 《Helvetica chimica acta》2011,94(3):433-437
The 1,3‐dipolar cycloaddition of 4‐chlorobenzonitrile oxide to the unsaturated system of (?)‐(R)‐carvone occurred exclusively at C(8) to give a new isoxazoline derivative. This derivative reacts with NH2OH to yield a new heterocycle, observed for the first time. On the other hand, the addition of 4‐chlorobenzonitrile oxide to the unsaturated lactone (?)‐4aα,7α,7aβ‐nepetalactone gave, in a good yield, also a new heterocycle, again obtained for the first time. The terpenoid (?)‐(R)‐carvone and iridoid (?)‐4aα,7α,7aβ‐nepetalactone were isolated from Moroccan species Mentha viridis (L.) and Nepeta tuberosa (L.), respectively. The new heterocycles obtained were identified by combination of chromatographic and spectroscopic methods. 相似文献
18.
Y. Turki-Ben Ali G. Bastard R. Bennaceur 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):222
The aim of this work is to analyze theoretically the correlation energies, for neutral, positive and negative excitons and bi-excitons in the III–V nitride InxGa1−xN/GaN quantum dot; where x=17.5% denotes the indium concentration. So, we propose a model consistent with experimental observations that is small InxGa1−xN truncated pyramids with circular base lying on wetting layer, both buried into GaN matrix. The correlation energies of many-body complexes X, X−, X+ and XX are investigated as a function of the quantum dot radius rc and the intrinsic electric field. 相似文献
19.
Hassen-Chehimi Dalila Ben Kbir-Ariguib Najia Trabelsi-Ayedi Malika 《Journal of Thermal Analysis and Calorimetry》1998,53(3):871-882
A previously established equation of a stoichiometric phase liquidus curve was applied to determination of the phase diagrams
of the systems MIPO3-Pr(PO3)3 (with MI=Na, Rb, Cs or Ag).
The temperature, enthalpy and entropy of fusion were calculated for each solid phase with the exception of silver polyphosphate,
the crystallization field of which was very limited.
The enthalpy of fusion of the polyphosphate Pr(PO3)3 was determined from the DTA curve.
The melting enthalpy of Pr(PO3)3 calculated from the different binary systems was approximately equal to the measured value. The calculated temperatures and
compositions were in good agreement with those determined experimentally.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
The aim of this paper is to point out the equivalence between three notions respectively issued from recursion theory, computational complexity and finite model theory. One the one hand, the rudimentary languages are known to be characterized by the linear hierarchy. On the other hand, this complexity class can be proved to correspond to monadic second-order logic with addition. Our viewpoint sheds some new light on the close connection between these domains: We bring together the two extremal notions by providing a direct logical characterization of rudimentary languages and a representation result of second-order logic into these languages. We use natural arithmetical tools, and our proofs contain no ingredient from computational complexity. 相似文献