全文获取类型
收费全文 | 141篇 |
免费 | 2篇 |
国内免费 | 2篇 |
专业分类
化学 | 95篇 |
力学 | 1篇 |
数学 | 17篇 |
物理学 | 32篇 |
出版年
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 5篇 |
2012年 | 12篇 |
2011年 | 8篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 6篇 |
2007年 | 4篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 12篇 |
2003年 | 6篇 |
2002年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1966年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有145条查询结果,搜索用时 234 毫秒
1.
2.
Several studies have reported prevalence rates for voice disorders in school-aged children. Less is known, however, about such prevalence in preschoolers, and whether racial, ethnic, or cultural diversity may influence it. The presence of voice disorders in a total of 2445 African-American and European-American preschool children, 1246 males and 1199 females, from 2 to 6 years of age is reported here. Presence of a voice disorder characterized by hoarseness was identified by a three-prong approach including teacher identification, investigator screening, and parent identification. Speech-language pathologists listened individually to each child's speech as they engaged each child in play-conversation activities. A voice disorder was identified on the basis of the judgment of two speech-language pathologists. Voice disorders characterized by hoarseness were identified in 95 children or 3.9% of the total sample by the investigators. Statistical analysis revealed no significant differences for age, gender, or race. 相似文献
3.
Hiller W Brüll A Argyropoulos D Hoffmann E Pasch H 《Magnetic resonance in chemistry : MRC》2005,43(9):729-735
The application of HPLC-NMR for the analysis of a mixture of fatty alcohol ethoxylates (FAEs) is described. The use of the new generation, cryogenically cooled probes is investigated in respect of the sensitivity advantage that they provide. The FAE mixture is separated using liquid chromatography at the critical point of adsorption. The ability of the method to differentiate between the different end groups and the degree of polymerization of the mixture constituents is investigated. Both on-flow and stop-flow HPLC-NMR techniques were used together with two-dimensional NMR spectroscopy. The results are compared with those obtained by using an evaporative light scattering detector for the HPLC. 相似文献
4.
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 Cain MP Caldwell DO Clark AR Cowan GD Crane DA Dahl OI Derby KA Eastman JJ Eberhard PH 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(8):945-948
5.
Arrigo Forni Irene Moretti Adele Mucci Fabio Prati Luisa Schenetti 《Chemistry of Heterocyclic Compounds》1995,31(9):1071-1078
A confrgurational and conformational study of NH, N-acetyl- and N-sulfonylaziridine carboxylates is performed by1H ,13C,17O, and15N NMR spectroscopy. The presence of acetyl and su fonyl groups on the ring nitrogen atom seems to reduce greatly the configurational stability at nitrogen.Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1226–1234, September, 1995. 相似文献
6.
Adele Bolognese Gaetano Correale Antonio Lavecchia Vincenzo Barone 《Tetrahedron》2004,60(37):8189-8197
Reaction between quinolinquinone and thiazolidine in basic medium was investigated. 2-Arylthiazolidine-4-carboxylic acid ethyl esters undergo two different cleavages in basic medium, yielding the 1-aryl-2-azadiene and a thiolic species. In the presence of quinolinquinone, the isomeric 1-aryl-3-ethoxycarbonyl-pyridoisoquinolin-5,10-diones and 3-amino-3-ethoxycarbonyl-dihydrothienoquinolin-4,9-diones are formed by a hetero-Diels-Alder reaction and 1,4-Michael addition reaction, respectively. A mechanism for the formation of the reaction products is presented. 相似文献
7.
Angelo Fontana Adele Cutignano Antonella Giordano Anna Domènech Coll Guido Cimino 《Tetrahedron letters》2004,45(37):6847-6850
The biogenesis of aglajnes, polypropionate allomones of the cephalaspidean mollusc Bulla striata, has been investigated in vivo by feeding experiments. Incorporation of the committed precursor, [1-14C]-propionate, into aglajne-1 (1) and -3 (3) established the de novo origin of these compounds in B. striata. In the letter we also discuss briefly the ecological meaning of the origin of polypropionates in B. striata and in other cephalaspidean molluscs. 相似文献
8.
A previously developed molecular level model for lipid bilayers [G. Brannigan and F. L. H. Brown, J. Chem. Phys. 120, 1059 (2004)] is extended to allow for variations in lipid length and simulations under constant surface tension conditions. The dependence of membrane elasticity on bilayer thickness is obtained by adjusting lipid length at constant temperature and surface tension. Additionally, bilayer fluidity at various lipid lengths is quantified by analysis of a length versus temperature phase diagram at vanishing tension. Regions of solid, gel-like (hexatic) and fluid bilayer behavior are established by identification of phase boundaries. The main melting transition is found to be density driven; the melting temperature scales inversely with lipid length since thermal expansion increases with lipid aspect ratio. 相似文献
9.
A. Bolognese R. Liberatore G. Riente G. Scherillo 《Journal of heterocyclic chemistry》1988,25(4):1247-1250
The oxidation mixture of 3-hydroxykynurenine ( 1 ), treated with aqueous acetic anhydride and, subsequently, with acidic methanol, yields the 1-hydroxy-3-carbomethoxy-5-methoxy-11-(β-aspartoyl-N-acetyl-methyl ester)pyrido[3,2-a]phenoxazine ( 5 ), the 1-hydroxy-11-(β-aspartoyl-N-acetyl-methyl ester)-5.H-pyrido[3,2-a]-phenoxazin-5-one ( 6 ), the 1-methoxy-11-(β-aspartoyl-N-acetyl-methyl ester)-5H-pyrido[3,2-a]phenoxazin-5-one ( 6a ), the l,5-dimethoxy-11-(β-aspartoyl-N-acetyl-methyl ester)pyrido[3,2-a]phenoxazine ( 7 ) and the 1-methyl-1(1′-[11-(β-aspartoyl-methyl esterimino)]ethenyl)ketal-1H,5H-pyrido[3,2-a]phenoxazin-5-one ( 8 ). A probable scheme, for the compound formation, is reported. 相似文献
10.
Francesca Goldoni Dario Iarossi Adele Mucci Luisa Schenetti 《Journal of heterocyclic chemistry》1997,34(6):1801-1804
3,4′-Dibromo-2,2′-bithiophene was converted, in high yield, into the corresponding dibutoxy derivative. The 1H 13C and nmr data are discussed in comparison with those of 3,3′- and 4,4′-dibutoxy-2,2′-bithiophene in relation to regiochemistry. 相似文献