全文获取类型
收费全文 | 449篇 |
免费 | 2篇 |
专业分类
化学 | 184篇 |
晶体学 | 2篇 |
力学 | 14篇 |
数学 | 21篇 |
物理学 | 230篇 |
出版年
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 11篇 |
2013年 | 25篇 |
2012年 | 11篇 |
2011年 | 17篇 |
2010年 | 11篇 |
2009年 | 16篇 |
2008年 | 10篇 |
2007年 | 16篇 |
2006年 | 11篇 |
2005年 | 15篇 |
2004年 | 10篇 |
2003年 | 4篇 |
2002年 | 13篇 |
2001年 | 12篇 |
2000年 | 8篇 |
1999年 | 15篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 10篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 13篇 |
1976年 | 12篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1968年 | 4篇 |
排序方式: 共有451条查询结果,搜索用时 15 毫秒
341.
We investigated the kinetics of autophobic dewetting, caused by differences in entropy, of a polymer melt slipping on a monolayer of end-grafted identical molecules (polymer brush). From simultaneous measures of the dewetted distance and the width of the resulting rim, we obtained in real time and quantitatively the slippage length and the contact angle, a measure of the "incompatibility" between identical molecules. Furthermore, we could directly relate a decrease in the slippage length in the course of the experiments at elevated temperatures to temporal or permanent attachment of polymers from the melt to the brush. 相似文献
342.
Khanna I. K. Bhagavan V. Srinivasa Singh M. N. 《Mathematical Physics, Analysis and Geometry》2000,3(3):287-303
In this paper, the generating relations for a set of hypergeometric functions ,,,m
(x) are obtained by using the representation of the Lie group SL(2,C) giving a suitable interpretation to the index m in order to derive the elements of Lie algebra. The principle interest in our results lies in the fact that a number of special cases would inevitably yield too many new and known results of the theory of special functions, namely the Laguerre, even and odd generalized Hermite, Meixner, Gottlieb, and Krawtchouk polynomials. 相似文献
343.
Chaudhary Ankita Khanna Garima Chopra Haritma Gaba Ritu 《Research on Chemical Intermediates》2022,48(5):2267-2278
A simple, efficient, and eco-friendly protocol for the synthesis of 1,3-oxazine derivatives, viz. 7-aryl-7,8-dihydro-6H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-e][1,3]oxazines and 3-aryl-3,4-dihydro-2H- naphtho[2,3-e][1,3]oxazine-5,10-diones, involving one-pot multicomponent condensation reaction of various amines and formaldehyde with sesamol/2-hydroxy-1,4-naphthoquinone, respectively, catalyzed by a choline chloride–oxalic acid deep eutectic solvent has been developed. The method offers several advantages, including mild reaction conditions, simple operating procedure, recyclable and biodegradable catalyst, short reaction times, and excellent yields of the target products.
相似文献344.
A set of density dependent nucleon-nucleon (N-N) interactions has been examined in nuclear matter calculations by varying
spin-isospin contributions. Two sets of potentials have been considered. One having a density dependentσ-function type short range part followed by one term long range Gaussian part while the other having a density dependentσ-function part followed by two Gaussian terms. The strength parameters of the potential have been fitted to the saturation
properties of nuclear matter, i.e. binding energy per particle of 15.5 MeV atk
F=1.35 fm−1. Several sets of these two potentials have been generated by varying the strength parameterM of Majorana exchange operatorP
M. It is seen thatM indirectly controls the spin, iso-spin contribution to the interaction potential and thus affects the nuclear matter properties
such as compressibility and symmetry energy considerably, while variation of these quantities with the range parameterμ for givenM is moderate at lowM values while at higherM values it is quite large. 相似文献
345.
346.
The spectrum of chlorine excited in the presence of argon has been photographed with a 21-ft. grating spectrograph in the first order. Two band systems in the region 2600–2390 Å and 2365–2239 Å are observed which appear to be respectively analogous to the 2950–2670 Å and 2660–2590 Å systems of bromine reported earlier by Venkateswarlu and Verma. The wavelengths and the wavenumbers of all the bands in the system 2600–2390 Å are given. The vibrational scheme along with the corresponding Franck-Condon parabola is also given. The analysis suggests that the lower state of the system is the 3π(O u +_ state established by Elliott at 17658 cm.?1 and that the upper state is at 67773 cm.?1 The vibrational constants obtained arew 0′ = 246·6 cm.?1,w 0′x 0′ = 0·615 cm.?1,w 0″ = 255·2 cm.?1,w 0″x 0″ = 5·5 cm.?1,w 0″y 0″ = ?0·0155 cm.?1 andw 0″z 0″ = 0·00115 cm.?1 相似文献
347.
Density functional theory can envisage a vast assortment of molecular possessions such as molecular structures, vibrational frequencies, molecular energies, ionization energies, polar, electric and magnetic properties etc. The efficacy of this method relies on the study of electronic parameters to categorize the reactive sites to comprehend the plausible action of these scaffolds. Further it also facilitates the correlation between the structural characteristics of drug and their inhibition efficiency against infectious microorganisms. In light of the above facts, we have studied the structural parameters such as energy (total), variation of electron density over highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), charge distribution, absolute electronegativity (χ), softness/hardness (σ/ɳ) and fraction of electron transfer (ΔN) of some previously synthesized heterocycles. 相似文献
348.
Maysonnave J Jukam N Ibrahim MS Maussang K Madéo J Cavalié P Dean P Khanna SP Steenson DP Linfield EH Davies AG Tignon J Dhillon SS 《Optics letters》2012,37(4):731-733
We used a terahertz (THz) quantum cascade laser (QCL) as an integrated injection seeded source and amplifier for THz time-domain spectroscopy. A THz input pulse is generated inside a QCL by illuminating the laser facet with a near-IR pulse from a femtosecond laser and amplified using gain switching. The THz output from the QCL is found to saturate upon increasing the amplitude of the THz input power, which indicates that the QCL is operating in an injection seeded regime. 相似文献
349.
F.C. Khanna A.P.C. Malbouisson J.M.C. Malbouisson A.E. Santana 《Annals of Physics》2009,324(9):1931-1952
Using a representation for Lie groups closely associated with thermal problems, we derive the algebraic rules of the real-time formalism for thermal quantum field theories, the so-called thermo-field dynamics (TFD), including the tilde conjugation rules for interacting fields. These thermo-group representations provide a unified view of different approaches for finite-temperature quantum fields in terms of a symmetry group. On these grounds, a path integral formalism is constructed, using Bogoliubov transformations, for bosons, fermions and non-abelian gauge fields. The generalization of the results for quantum fields in topology is addressed. 相似文献
350.
Relations among the magnetic moments of charmed and uncharmed baryons are derived in the framework of SU(4) and SU(8) symmetries.
The SU(3) resultμ (Σ
o)=−μ(Λ) is not present in SU(4), but is obtained in SU(8). Higher order effects are further considered to improve the situation. 相似文献