全文获取类型
收费全文 | 64篇 |
免费 | 0篇 |
专业分类
化学 | 24篇 |
数学 | 23篇 |
物理学 | 17篇 |
出版年
2019年 | 1篇 |
2018年 | 2篇 |
2016年 | 4篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 3篇 |
2011年 | 6篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 2篇 |
2005年 | 4篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2001年 | 1篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有64条查询结果,搜索用时 15 毫秒
1.
2.
Moldovan L Melinte S Bayot V Papadakis SJ De Poortere EP Shayegan M 《Physical review letters》2000,85(20):4369-4372
We report very low temperature ( T) thermopower and resistivity ( rho) measurements on variable-density, two-dimensional hole systems confined to GaAs quantum wells. As the hole density is lowered from 1.49x10(11) cm(-2) to 0.14x10(11) cm(-2), the system crosses from an insulating ( drho / dT less, similar0) to a metallic regime ( drho / dT>0) and finally displays insulating behavior ( drho / dT<0). Diffusion thermopower shows a striking sign reversal in a narrow range of density in the metallic regime, suggesting a qualitative change in the conduction or the scattering mechanism. 相似文献
3.
Rahul S. Pawar Erich Grundel Eugene Mazzola Kevin D. White Alexander J. Krynitsky Jeanne I. Rader 《Journal of separation science》2010,33(2):200-205
Enantioseparation of the pyrrolizidine alkaloid isomers intermedine and lycopsamine, isolated from Symphytum uplandicum, is discussed. The separatory power of two immobilized carbohydrate‐based chiral HPLC columns, Chiralpak IA and IC, in different chromatographic conditions is compared. The study demonstrated the importance of solvent and column selection while developing such chiral HPLC separation methods. The baseline HPLC separation of the two alkaloid isomers in preparatory scale is reported for the first time. The optimized separations were achieved on a Chiralpak IA column with mobile phases of ACN/methanol (80:20) and methanol/methyl‐t‐butyl ether (90:10), both containing 0.1% diethylamine. 相似文献
4.
Fabio D’Agostino Elvira Oliveri Emanuela Bagnato Francesca Falco Salvatore Mazzola Mario Sprovieri 《Analytica chimica acta》2014
The aim of this work was to develop a new method to determine the mercury (Hg) concentrations in phosphate rock using a dedicated analytical instrument (the DMA80 Tricell by Milestone) that employs an integrated sequence of thermal decomposition followed by catalyst conversion, amalgamation and atomic absorption spectrophotometry. However, this instrument underestimates Hg concentrations when phosphorite and apatite rocks are investigated with a classic thermal decomposition treatment that complies with US EPA method 7473. 相似文献
5.
McCrane MP Weinert EE Lin Y Mazzola EP Lam YF Scholl PF Rokita SE 《Organic letters》2011,13(5):1186-1189
Selective oxidation by bis[(trifluoroacetoxy)iodo]benzene (BTI) provides an effective trap for quenching adducts formed reversibly between dC and an ortho-quinone methide (QM) under physiological conditions. A model adduct generated by 4-methyl-o-QM and 2'-deoxycytidine is rapidly converted by intramolecular cyclization and loss of aromaticity to a characteristic product for quantifying QM alkylation. However, BTI induces a surprising rearrangement driven by overoxidation of a derivative lacking an alkyl substituent at the 4-position of the QM. 相似文献
6.
Phosphorus–nitrogen rotation barriers have been determined by low temperature NMR methods in a variety of compounds of the type RP(X)NR2′. The observed activation parameters are concentration and solvent independent. Increasing the bulk of substituents on nitrogen increases the barrier. Phosphonamidous fluorides (X = F) have lower barriers than the corresponding chlorides (X = Cl). Increasing the bulk of substituents on phosphorus decreases the barrier. 相似文献
7.
8.
9.
Riassunto Il punto di partenza di questo lavoro è l'interpretazione delle topologie di Grothendieck nel linguaggio dei sistemi relazionali
(cfr. [5]); ciò permette uno studio aritmetico di tali topologie. Attraverso nuove tecniche, qui introdotte, si ottengono
risultati non privi di interesse, tra i quali una caratterizzazione degli spazi topologici noetheriani, ed ulteriori strutture
topologiche di tipo locale (siti tangenti), per le quali vengono dimostrate numerose proprietà. Vengono, infine, date alcune
applicazioni alla teoria degli schemi, utilizzando il funtore inviluppo affine.
Summary The starting point of this paper is the interpretation of Grothendieck's topologies in the language of relational systems (cfr. [5]); this permits an arithmetical study of these topologies. By applying new techniques introduced here, we have achieved interesting results. These include a new characterization of Noetherian topological spaces, and further topological structures of local type (tangent sites) for which we have shown numerous properties. Finally, we have used the affine-envelope functor to illustrate some applications to the theory of schemes.相似文献
10.