全文获取类型
收费全文 | 295篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 93篇 |
晶体学 | 3篇 |
力学 | 2篇 |
数学 | 17篇 |
物理学 | 186篇 |
出版年
2020年 | 5篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 10篇 |
2012年 | 8篇 |
2011年 | 16篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2007年 | 7篇 |
2006年 | 10篇 |
2005年 | 14篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 14篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 11篇 |
1995年 | 16篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 11篇 |
1989年 | 1篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 13篇 |
1985年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1971年 | 5篇 |
1970年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有301条查询结果,搜索用时 15 毫秒
221.
Fuchs J Cowan TE Audebert P Ruhl H Gremillet L Kemp A Allen M Blazevic A Gauthier JC Geissel M Hegelich M Karsch S Parks P Roth M Sentoku Y Stephens R Campbell EM 《Physical review letters》2003,91(25):255002
The evolution of laser-generated MeV, MA electron beams propagating through conductors and insulators has been studied by comparing measurement and modeling of the distribution of MeV protons that are sheath accelerated by the propagated electrons. We find that electron flow through metals is uniform and can be laser imprinted, whereas propagation through insulators induces spatial disruption of the fast electrons. Agreement is found with material dependent modeling. 相似文献
222.
Baton SD Santos JJ Amiranoff F Popescu H Gremillet L Koenig M Martinolli E Guilbaud O Rousseaux C Rabec Le Gloahec M Hall T Batani D Perelli E Scianitti F Cowan TE 《Physical review letters》2003,91(10):105001
The second harmonic of the laser light (2omega(0)) is observed on the rear side of thick solid targets irradiated by a laser beam at relativistic intensities. This emission is explained by the acceleration by the laser pulse in front of the target of short bunches of electrons separated by the period (or half the period) of the laser light. When reaching the rear side of the target, these electron bunches emit coherent transition radiation at 2omega(0). The observations indicate that, in our conditions, the minimum fraction of the laser energy transferred to these electron bunches is of the order of 1%. 相似文献
223.
Tregenna-Piggott PL Andres HP McIntyre GJ Best SP Wilson CC Cowan JA 《Inorganic chemistry》2003,42(4):1350-1365
Variable-temperature single-crystal neutron diffraction structures of the alums CsM(III)(SO(4))(2).12D(2)O, where M(III) = Ti, V, Mn, and Ga, are reported. Structural differences are highlighted by the titanium and manganese alums, which undergo cubic (Pathremacr;) to orthorhombic (Pbca) phase transitions at approximately 13 and approximately 156 K, respectively. The structural instability exhibited by these salts is interpreted as arising from cooperative Jahn-Teller interactions, and these measurements characterize the structural changes that result from the coupling between the electronic and vibrational states. Although the symmetry changes associated with the phase transformations are analogous for the Ti and Mn alums, the low-temperature geometries of the tervalent hexaaqua cations are markedly different. Whereas the MnO(6) framework is subject to a pronounced tetragonal elongation, changes in the Ti-O bond lengths are very modest; but significant changes in the O-Ti-O bond angles and in the disposition of the coordinated water molecules are identified. The large differences in the transition temperatures and in the low-temperature stereochemistries of the [Ti(OD(2))(6)](3+) and [Mn(OD(2))(6)](3+) cations are related to the sensitivity of the energies of the t(2g) (O(h)) and e(g) (O(h)) orbitals to the various asymmetric vibrations of the hexaaqua complex. 相似文献
224.
225.
226.
227.
R S Cowan J I Alcantara L A Whitford P J Blamey G M Clark 《The Journal of the Acoustical Society of America》1989,85(6):2593-2607
Three studies are reported on the speech perception of normally hearing and hearing-impaired adults using combinations of visual, auditory, and tactile input. In study 1, mean scores for four normally hearing subjects showed that addition of tactile information, provided through the multichannel electrotactile speech processor, to either audition alone (300-Hz low-pass-filtered speech) or lipreading plus audition resulted in significant improvements in phoneme and word discrimination scores. Information transmission analyses demonstrated the effectiveness of the tactile aid in providing cues to duration, F1 and F2 features for vowels, and manner of articulation features for consonants, especially features requiring detection and discrimination of high-frequency information. In study 2, six different cutoff frequencies were used for a low-pass-filtered auditory signal. Mean scores for vowel and consonant identification were significantly higher with the addition of tactile input to audition alone at each cutoff frequency up to 1500 Hz. The mean speechtracking rate was also significantly increased by the additional tactile input up to 1500 Hz. Study 3 examined speech discrimination of three hearing-impaired adults. Additional information available through the tactile aid was shown to improve speech discrimination scores; however, the degree of increase was inversely related to the level of residual hearing. Results indicate that the electrotactile aid may be useful for patients with little residual hearing and for the severely to profoundly hearing impaired, who could benefit from the high-frequency information presented through the tactile modality, but unavailable through hearing aids. 相似文献
228.
Aihara H Alston-Garnjost M Avery RE Barbaro-Galtieri A Barker AR Barnes AV Barnett BA Bauer DA Bengtsson pH Bintinger DL Bobbink GJ Bolognese TS Bross AD Buchanan CD Buijs A Caldwell DO Clark AR Cowan GD Crane DA Dahl OI Derby KA Eastman JJ Eberhard PH Edberg TK Eisner AM Enomoto R Erné FC Fujii T Gary JW Gorn W Hauptman JM Hofmann W Huth JE Hylen J Kamae T Kaye HS Kees KH Kenney RW Kerth LT Ko W Koda RI Kofler RR Kwong KK Lander RL Langeveld WG Layter JG Linde FL Lindsey CS Loken SC Lu A Lu XQ 《Physical review letters》1987,58(2):97-100
229.
P. C. Rice-Evans D. T. Britton B. P. Cowan 《Applied Physics A: Materials Science & Processing》1987,43(4):283-285
A cryostat system incorporating a low-energy positron beam for surface measurements down to Temperatures below 2 K is currently under construction at the Royal Holloway and Bedford New College. The positron beam has recently been brought into operation and its operating characteristics have been evaluated. Positrons from a22Na source are converted with an efficiency of =2×10–4 and transported magnetically at 1.5 V above the work function to a target at the bottom of a cryostat. The transmission of a 7 mm diameter beam is found to be constant over a range of axial field strengths from 40 to 50 G.This paper is based upon a poster presented at the International Symposium Production of Low-Energy Positrons with Accelerators and Applications (Justus-Liebig-Universität Giessen, FRG, 25–27 September, 1986) 相似文献
230.
Aihara H Alston-Garnjost M Avery RE Barbaro-Galtieri A Barker AR Barnes AV Barnett BA Bauer DA Bengtsson H Bintinger DL Bobbink GJ Bolognese TS Bross AD Buchanan CD Buijs A Caldwell DO Clark AR Cowan GD Crane DA Dahl OI Derby KA Eastman JJ Eberhard PH Edberg TK Eisner AM Enomoto R Erné FC Fujii T Gary JW Gorn W Hauptman JM Hofmann W Huth JE Hylen J Kamae T Kaye HS Kees KH Kenney RW Kerth LT Ko W Koda RI Kofler RR Kwong KK Lander RL Langeveld WG Layter JG Linde FL Lindsey CS Loken SC Lu A Lu X 《Physical review letters》1986,57(26):3245-3248