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1.
铸造锌铝合金稀土变质机理的电子理论研究   总被引:13,自引:3,他引:10       下载免费PDF全文
刘贵立  李荣德 《物理学报》2003,52(9):2264-2267
根据分子动力学理论建立了液态锌铝合金ZA27的模型,结合计算机编程构造出了ZA27合金α 相与液相共存时的原子结构模型,利用递归方法计算了稀土固溶于晶粒内和富集于结晶前沿 时的电子结构.由此得出:稀土处于相界区比在晶内更稳定,从而解释了稀土在α相内溶解 度很小,结晶时富集于结晶前沿液体中的事实;稀土处于液态和晶态的结构能差相对于铝较 大解释了稀土在相界前的富集使α晶枝产生熔断、游离、增殖的观点.原子间的键级积分计 算也表明,稀土处于结晶前沿液体中与铝相比不容易结晶到晶体表面,起到阻碍晶粒长大, 细化晶粒的作用,这就从电子层次解释了稀土的变质机理.  相似文献
2.
大尺度相干结构的光学特性研究   总被引:3,自引:1,他引:2  
根据大气近地面层对流湍池的实验结果,提出了一种用于描述大尺度相干结构的立体模型——椭球结构模型。计算并分析了该大尺度相干结构对光传输波前相位结构函数的影响,且和小尺度湍流结构作了比较。对于相同的参数,光线平行于间断面时造成的影响大于垂直于间断面;一般情况下,影响都很小;但当光线平行穿过具有三角波模型结构的间断面时可能产生较大的影响。  相似文献
3.
Thick skin in neutron/proton-rich sodium isotopes   总被引:2,自引:0,他引:2  
Nucleon (both neutron and proton) density distributions of the chain of sodium isotopes are calculated using a semi-phenomenological model of nuclear density which incorporates correctly the asymptotic behaviour and the behaviour near the centre. The experimental charge root-mean-square radii and the single neutron and proton separation energies, required as input, are used. The calculated interaction cross-sections using these densities in the Glauber model agree well with the experiment. The calculated neutron rms radii r n and the nuclear skin thickness ( r n - r p) closely agree with the corresponding experimental values and also are consistent with the Relativistic Hartree-Bogoliubov (RHB) calculations. Received: 24 April 2001 / Accepted: 28 June 2001  相似文献
4.
铁基纳米晶合金介观结构的等效RLC并联模型   总被引:2,自引:0,他引:2       下载免费PDF全文
根据实验研究成果提出纳米晶合金软磁性能受其介观结构影响的观点,建立了Fe基纳米晶合金的球状介观结构模型,分别求出只有交变磁场或交变磁场和静磁场作用时纳米晶粒球的频率函数——D函数.分析表明,两种D函数都是复变函数,其实部Re(D)为纳米晶电感性质和电容性质的反映,虚部Im(D)为纳米晶电阻性质的反映,据此建立了Fe基纳米晶合金介观结构的等效RLC并联模型.由该模型求得合金产生极值巨磁电阻的条件为νextGMI=νRe(D)=0,决定因素有μ,σ,ω,R和Hex及微观磁结构.  相似文献
5.
Rational maps, monopoles and skyrmions   总被引:1,自引:0,他引:1  
We discuss the similarities between BPS monopoles and skyrmions, and point to an underlying connection in terms of rational maps between Riemann spheres. This involves the introduction of a new ansatz for Skyrme fields. We use this to construct good approximations to several known skyrmions, including all the minimal energy configurations up to baryon number nine, and some new solutions such as a baryon number seventeen Skyrme field with the truncated icosahedron structure of a buckyball.

The new approach is also used to understand the low-lying vibrational modes of skyrmions, which are required for quantization. Along the way we discover an interesting Morse function on the space of rational maps which may be of use in understanding the Sen forms on the monopole moduli spaces.  相似文献

6.
原子模型势理论中径向微分算符矩阵元的计算   总被引:1,自引:1,他引:0  
本文推广[7,8]的工作,导出了多电子原子模型势理论中含径向微分算符的矩阵元通式,可直接用于以“速度”及“加速度”形式跃迁振子强度计算。  相似文献
7.
Advances in NMR instrumentation and pulse sequence design have resulted in easier acquisition of Residual Dipolar Coupling (RDC) data. However, computational and theoretical analysis of this type of data has continued to challenge the international community of investigators because of their complexity and rich information content. Contemporary use of RDC data has required a-priori assignment, which significantly increases the overall cost of structural analysis. This article introduces a novel algorithm that utilizes unassigned RDC data acquired from multiple alignment media (nD-RDC, n  3) for simultaneous extraction of the relative order tensor matrices and reconstruction of the interacting vectors in space.Estimation of the relative order tensors and reconstruction of the interacting vectors can be invaluable in a number of endeavors. An example application has been presented where the reconstructed vectors have been used to quantify the fitness of a template protein structure to the unknown protein structure. This work has other important direct applications such as verification of the novelty of an unknown protein and validation of the accuracy of an available protein structure model in drug design. More importantly, the presented work has the potential to bridge the gap between experimental and computational methods of structure determination.  相似文献
8.
The neutron-deficient nucleus 68As was populated at high spin in two experiments using the reaction 40Ca(32S, 3pn) at beam energies of 105 and 95 MeV. A self-supporting and a gold-backed, highly enriched 40Ca target were used. Gamma rays were detected with the EUROBALL array, combined with the charged-particle detector array EUCLIDES and the Neutron Wall. The 68As level scheme was considerably extended, especially at negative parity and many previous spin-parity assignments were confirmed or rejected. The total-Routhian-surface (TRS) calculations find shape coexistence and softness for the negative- and positive-parity states, respectively.  相似文献
9.
High-spin states in 123Cs, populated via the 100Mo ( 28Si, p4n) fusion-evaporation reaction at E lab = 130 MeV, have been investigated employing in-beam γ-ray spectroscopic techniques. Rotational bands, built on πg 7/2, πg 9/2 and the unique-parity πh 11/2 orbitals, have been extended and evolve into bands involving rotationally aligned ν(h 11/2)2 and π(h 11/2)2 quasiparticles. A three-quasiparticle band based on the high-K πh 11/2 ⊗ νg 7/2 ⊗ νh 11/2 configuration has also been observed. Total Routhian Surface (TRS) calculations have been used to predict the nuclear shape parameters ( β2, β4, γ) for the various assigned configurations. The assigned configurations have been discussed in the framework of a microscopic theory based on the deformed Hartree-Fock (HF) and angular-momentum projection techniques.  相似文献
10.
Excited states in 100Tc have been studied using the 96Zr( 7Li, 3n) reaction at a beam energy of 27 MeV. In the present work, evidence has been found for a second I = 1 band decaying via several stretched dipole transitions to the previously known I = 1 negative-parity band. Comparison of these data with those in neighbouring nuclei and also against recently reported criteria for chiral bands in nuclei, suggests that the two structures can be interpreted as chiral partners. Core quasi-particle coupling model calculations show reasonable agreement with the data and generally support the chiral interpretation of the states.  相似文献
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