全文获取类型
收费全文 | 578篇 |
免费 | 60篇 |
国内免费 | 8篇 |
专业分类
化学 | 338篇 |
晶体学 | 6篇 |
力学 | 24篇 |
综合类 | 1篇 |
数学 | 97篇 |
物理学 | 180篇 |
出版年
2023年 | 3篇 |
2022年 | 11篇 |
2021年 | 14篇 |
2020年 | 11篇 |
2019年 | 13篇 |
2018年 | 13篇 |
2017年 | 7篇 |
2016年 | 23篇 |
2015年 | 22篇 |
2014年 | 31篇 |
2013年 | 47篇 |
2012年 | 35篇 |
2011年 | 35篇 |
2010年 | 26篇 |
2009年 | 35篇 |
2008年 | 30篇 |
2007年 | 27篇 |
2006年 | 26篇 |
2005年 | 19篇 |
2004年 | 22篇 |
2003年 | 12篇 |
2002年 | 11篇 |
2001年 | 10篇 |
2000年 | 17篇 |
1999年 | 11篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 13篇 |
1995年 | 11篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 3篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有646条查询结果,搜索用时 15 毫秒
91.
本文求出了Eliashberg方程在T=Tc时的解,得到了下面的临界温度级数表示式: 其中α0(μ*),α1(μ*)等系数是μ*的函数.此式表明,Tc不仅依赖于λ,〈ω2〉和μ*,而且依赖于有效声子谱α2F(ω)的各级矩〈ω2n〉.这是区别于前人的Tc公式最重要的一点。这说明像McMillan以及Allen和Dynes的Tc公式不仅是近似的,而主要是他们没有能正确地概括出α2F(ω)对Tc的影响. 相似文献
92.
A first-order matrix differential equation in energy is used to propagate radial matrix elements arising in DWBA of relativistic electron scattering from nuclei. Given an initial set of matrix elements at some value of the energy, this equation permits the evaluation of the radial matrix elements over the complete energy transfer range. A computer code has been written for this new procedure and the virtual photon spectra accompanying electron scattering from a point nucleus is calculated as a function of photon energy for various multipoles, nuclear charges, and incident electron energies. 相似文献
93.
Perez Gutierrez RM Rosario Vargas S Martinez Martinez F Garcia Baez E Figueroa Torres G 《Natural product research》2006,20(3):305-310
Antispasmodic activity-guided fractionation together with chemical analysis led to the isolation of one novel delta-lactone named oedogonolide from Oedogonium capillare. Identification was based on spectroscopic methods. The oedogonolide produces a significant antispasmodic effect on the contractions of the rat ileum induced by acetylcholine, histamine and barium chloride. 相似文献
94.
The adsorption of anisole, 3,5-dimethylanisole, and 3,5-bis-(trifluoromethyl)-anisole on Pt(111) was studied theoretically and compared to the adsorption of benzene using relativistically corrected density functional theory. A cluster of 31 platinum atoms was used to simulate the surface. The three anisoles were found to be less strongly adsorbed than the parent molecule benzene, 3,5-bis-(trifluoromethyl)-anisole showing weakest adsorption, with an adsorption energy of only one-third that of benzene. The theoretical study was complemented by in situ ATR-IR spectroscopy of the adsorption of the anisole derivatives on a polycrystalline Pt film. The spectroscopic study indicated that the adsorption strength of the anisoles follows the same order as predicted by the calculations. In addition, catalytic hydrogenation tests showed that the propensity to aromatic ring hydrogenation can also be correlated to the mode and strength of adsorption of the anisoles. The degree of saturation followed the same order as the adsorption strength found by the calculations and indicated by spectroscopy. Although 3,5-dimethyl substitution on anisole resulted in only a partial loss of adsorption energy and reactivity toward ring hydrogenation as compared to anisole, the substitution by CF(3) groups led to a large loss of adsorption energy and complete loss of reactivity toward aromatic ring saturation. Along with the study of the substituent effect on the adsorption of aromatic molecules, the correlation between adsorption and propensity to saturation of aromatic substrates could be corroborated. 相似文献
95.
J.M. Florez Álvaro S. Núñez P. Vargas 《Journal of magnetism and magnetic materials》2010,322(22):3623-3630
We study the quenched energy-splitting (ΔE) of a single-molecule magnet (SMM) conformed by two exchange coupled giant-spins. An assessment of two nontrivial characteristics of this quenching is presented: (i) The quenching-points of a strongly exchange-coupled dimer differ from the ones of their respective giant-spin modeled SMM and such a difference can be well described by using the Solari-Kochetov extra phase; (ii) the dependence on the exchange coupling of the magnetic field values at the quenching-points when ΔE passes from monomeric to dimeric behavior. The physics behind these exchange-modified points, their relation with the ΔE-oscillations experimentally obtained by the Landau-Zener method and with the diabolical-plane of a SMM, is discussed. 相似文献
96.
José González-García María Deseada Esclapez Yolanda Vargas Hernández Verónica Sáez 《Ultrasonics》2010,50(2):318-91
Sonoelectrochemistry is undergoing a reemerging activity in the last years with an increasing number of papers appearing in a wide range of peer review journals. Applied studies which cover environmental treatments, synthesis or characterization of nanostructures, polymeric materials synthesis, analytical procedures, films preparations, membrane preparations among other interesting applications have been reviewed. The revised fundamental analyses trying to elucidate the mechanism of the interactions between the ultrasound and electrical fields, are focused on test electrochemical processes, on the use of unconventional solvents and combination with other techniques. After the review of the achievements and faults of sonoelectrochemistry, future research lines are suggested. 相似文献
97.
98.
Carlos E. Vargas Víctor Velázquez Sergio Lerma 《The European Physical Journal A - Hadrons and Nuclei》2013,49(1):1-8
Microscopic studies in heavy nuclei are very scarce due to large valence spaces involved. This computational problem can be avoided by means of the use of symmetry-based models. Ground-state, γ and β bands, and their B(E2) transition strengths in 160–168Dy isotopes, are studied in the framework of the pseudo-SU(3) model which includes the preserving symmetry Q · Q term and the symmetry-breaking Nilsson and pairing terms, systematically parametrized. Additionally, three rotor-like terms are considered, whose free parameters, fixed for all members of the chain, are used to fine tune the moment of inertia of rotational bands and the band head of γ and β bands. The model succesfully describes in a systematic way rotational features in these nuclei and allows to extrapolate toward the midshell nucleus 170Dy. The results presented show that it is possible to study a full chain of isotopes or isotones in the region with the present model. 相似文献
99.
100.
Jonas H. Muessig Melanie Thaler Rian D. Dewhurst Valerie Paprocki Jens Seufert James D. Mattock Alfredo Vargas Holger Braunschweig 《Angewandte Chemie (International ed. in English)》2019,58(13):4405-4409
The lability of B=B, B?P, and B–halide bonds is combined in the syntheses of the first diiododiborenes. In a series of reactivity tests, these diiododiborenes undergo cleavage of all six of their central bonds in different ways, leading to products of B=B hydrogenation and dihalogenation as well as halide exchange. 相似文献