全文获取类型
收费全文 | 2655篇 |
免费 | 22篇 |
国内免费 | 22篇 |
专业分类
化学 | 1481篇 |
晶体学 | 9篇 |
力学 | 69篇 |
数学 | 560篇 |
物理学 | 580篇 |
出版年
2020年 | 16篇 |
2016年 | 16篇 |
2015年 | 20篇 |
2014年 | 25篇 |
2013年 | 104篇 |
2012年 | 95篇 |
2011年 | 109篇 |
2010年 | 72篇 |
2009年 | 72篇 |
2008年 | 98篇 |
2007年 | 123篇 |
2006年 | 118篇 |
2005年 | 112篇 |
2004年 | 95篇 |
2003年 | 80篇 |
2002年 | 80篇 |
2001年 | 50篇 |
2000年 | 43篇 |
1999年 | 40篇 |
1998年 | 31篇 |
1997年 | 37篇 |
1996年 | 63篇 |
1995年 | 61篇 |
1994年 | 55篇 |
1993年 | 35篇 |
1992年 | 42篇 |
1991年 | 30篇 |
1990年 | 39篇 |
1989年 | 33篇 |
1988年 | 32篇 |
1987年 | 31篇 |
1986年 | 38篇 |
1985年 | 40篇 |
1984年 | 38篇 |
1983年 | 31篇 |
1982年 | 32篇 |
1981年 | 60篇 |
1980年 | 43篇 |
1979年 | 36篇 |
1978年 | 35篇 |
1977年 | 52篇 |
1976年 | 45篇 |
1975年 | 51篇 |
1974年 | 41篇 |
1973年 | 46篇 |
1972年 | 26篇 |
1971年 | 16篇 |
1970年 | 15篇 |
1969年 | 16篇 |
1968年 | 29篇 |
排序方式: 共有2699条查询结果,搜索用时 15 毫秒
41.
David A. Edwards 《International Journal of Theoretical Physics》1981,20(7):503-517
In this paper we explore the mathematical foundations of quantum field theory. From the mathematical point of view, quantum field theory involves several revolutions in structure just as severe as, if not more than, the revolutionary change involved in the move from classical to quantum mechanics. Ordinary quantum mechanics is based upon real-valued observables which are not all compatible. We will see that the proper mathematical understanding of Fermi fields involves a new concept of probability theory, the graded probability space. This new concept also yields new points of view concerning ergodic theorems in statistical mechanics. 相似文献
42.
Alex Edwards 《The Journal of the Operational Research Society》1994,45(12):1467-1467
43.
There are essentially two schools of thought regarding the function of decision support systems. One is that the main purpose is to support the decision-maker in whatever style of decision-making he or she wishes. The other is that the support, while suiting the decision-maker's individual style, must also be based on an appropriate theoretical paradigm. The work with students of decision support systems reported here suggests that the latter, normative, view is not one which comes naturally to many of the students, even when working on an example where it seemed relatively easy to incorporate. Other conclusions are also presented, relating to the choice of software for decision support system development, the process of teaching about decision support systems, and group formation. 相似文献
44.
Keiichi Ohno Hiroatsu Matsuura Don McNaughton Harold W. Kroto 《Journal of Molecular Spectroscopy》1985,111(2):415-424
The infrared spectra of 1-phosphapropyne, CH3CP, and its perdeuteride, CD3CP, have been measured in the gaseous and solid states. The QK branches of perpendicular bands have been analyzed in terms of the usual quadratic expression in K. Fermi resonances were identified for the ν1, ν2 + ν3, 2ν3, 2ν60; and ν5, 2ν3 + ν8 band systems of CH3CP and the ν1, 2ν3, 2ν60; ν6, ν7 + ν8; and ν7, 3ν81 band systems of CD3CP. The xy Coriolis interaction was also identified between the ν3 and ν6 bands of the two species. All the fundamentals were assigned and the normal coordinate treatment was carried out along with the Coriolis constants, ζz. 相似文献
45.
Exciton states and optical properties in wurtzite (WZ) InGaN/GaN quantum well (QW) are investigated theoretically, considering finite barrier width and built-in electric field effects. Numerical results show that when the barrier width increases, the ground-state exciton binding energy, the interband transition energy and the integrated absorption probability increase first and then they are insensitive to the variation of the barrier width. For any barrier width, the ground-state exciton binding energy and the integrated absorption probability have a maximum when the well width is 1 nm; moreover, the integrated absorption probability goes to zero when the well width is larger than 6 nm. In addition, the competition effects between the built-in electric field and quantum confinement are also investigated in the WZ InGaN/GaN QW. 相似文献
46.
Helen C. Brown Richard D. Bowen Howell G. M. Edwards Dennis W. Farwell 《Journal of Raman spectroscopy : JRS》2007,38(12):1586-1594
The Raman spectra of 3‐(pent‐1‐enyl) methyl ether (3‐methoxypent‐1‐ene) and four deuterium‐labelled analogues are reported and discussed. Correlations between specific structural features and the associated Raman bands are developed, with a view to enhancing the analytical application of Raman spectroscopy in investigating materials containing an alkenyl group. Particular attention is given to developing means of distinguishing the methyl group attached to the carbon skeleton from that of the methoxy group, to maximize the analytical utility of the signals associated with ν(sp2 CH), ν(sp2 CH2) and ν(CC) stretching vibrations, and to interpreting in more detail certain δ(sp2 CH) and δ(sp2 CH2) vibrations of the atoms of the double bond. These results establish a definitive spectroscopic protocol for differentiating a methoxy group from a methyl substituent attached directly to a carbon atom in unsaturated ethers. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
47.
Lenize F. Maia Vanessa E. de Oliveira Maria E. R. Oliveira Felipe D. Reis Beatriz G. Fleury Howell G. M. Edwards Luiz F. C. de Oliveira 《Journal of Raman spectroscopy : JRS》2013,44(4):560-566
Polyenic pigments in octocorals have been investigated by Raman spectroscopy using laser excitation at 532, 785 and 1064 nm. The spectral features suggest the structural nature of carotenoids from Phyllogorgia dilatata, Leptogorgia punicea, Muricea atlantica, Carijoa riisei and conjugated polyenals from L. punicea, L. setacea, Muricea flamma and Renilla muelleri. The observed vibrational bands at ca. 1540–1520 ν1(C=C), 1159 ν2(C–C) and 1005 cm−1 ρ3(C–CH3) were assigned to carotenoids, whereas the identification of non‐methylated conjugated polyenals have been proposed due to two major Raman bands at ca. 1500 and 1120 cm‐1, assigned to ν(C=C) and ν(C–C), respectively. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
48.
49.
Achterberg A Ackermann M Adams J Ahrens J Andeen K Atlee DW Bahcall JN Bai X Baret B Bartelt M Barwick SW Bay R Beattie K Becka T Becker JK Becker KH Berghaus P Berley D Bernardini E Bertrand D Besson DZ Blaufuss E Boersma DJ Bohm C Bolmont J Böser S Botner O Bouchta A Braun J Burgess C Burgess T Castermans T Chirkin D Christy B Clem J Cowen DF D'Agostino MV Davour A Day CT De Clercq C Demirörs L Descamps F Desiati P Deyoung T Diaz-Velez JC Dreyer J Dumm JP Duvoort MR Edwards WR Ehrlich R 《Physical review letters》2006,97(22):221101
On 27 December 2004, a giant gamma flare from the Soft Gamma-Ray Repeater 1806-20 saturated many satellite gamma-ray detectors, being the brightest transient event ever observed in the Galaxy. AMANDA-II was used to search for down-going muons indicative of high-energy gammas and/or neutrinos from this object. The data revealed no significant signal, so upper limits (at 90% C.L.) on the normalization constant were set: 0.05(0.5) TeV-1 m;{-2} s;{-1} for gamma=-1.47 (-2) in the gamma flux and 0.4(6.1) TeV-1 m;{-2} s;{-1} for gamma=-1.47 (-2) in the high-energy neutrino flux. 相似文献
50.
Scaling level-spacing distribution functions in the bulk of the spectrum in random matrix models ofN×N hermitian matrices and then going to the limitN leads to the Fredholm determinant of thesine kernel sin(x–y)/(x–y). Similarly a scaling limit at the edge of the spectrum leads to theAiry kernel [Ai(x)Ai(y)–Ai(x)Ai(y)]/(x–y). In this paper we derive analogues for this Airy kernel of the following properties of the sine kernel: the completely integrable system of P.D.E.'s found by Jimbo, Miwa, Môri, and Sato; the expression, in the case of a single interval, of the Fredholm determinant in terms of a Painlevé transcendent; the existence of a commuting differential operator; and the fact that this operator can be used in the derivation of asymptotics, for generaln, of the probability that an interval contains preciselyn eigenvalues. 相似文献