全文获取类型
收费全文 | 70篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
化学 | 28篇 |
数学 | 11篇 |
物理学 | 32篇 |
出版年
2013年 | 2篇 |
2012年 | 6篇 |
2011年 | 4篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 3篇 |
2005年 | 5篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有71条查询结果,搜索用时 15 毫秒
31.
32.
The two sodium aryloxide complexes [{(4-R-C6H4ONa)6 x (dioxane)3}infinity], where R = Et (1) or F (2), have been prepared and found to form three-dimensional cubic networks in the solid state. Each structure is similarly composed of dioxane-connected Na6O6 aggregates that act as octahedral nodes in directing the assembly process. Although the localized metrical parameters within the hexameric cages are similar to each other, as well as to those of the molecular analogue [(4-F-C6H4ONa)6 x (THF)8] (3), the gross architectures show significant variations. In particular, the smaller complex 2 ensures effective filling of space through transannular Na-F interaggregate interactions, resulting in substantial compression of the cubic framework. 相似文献
33.
MacDougall DJ Kennedy AR Noll BC Henderson KW 《Dalton transactions (Cambridge, England : 2003)》2005,(12):2084-2091
The alpha,alpha'-stabilized carbanion complexes [(PhSO2)2CHLi.THF]1, [(PhSO2)2CHNa.THF]2 and [(PhSO2)2CHK]3 were prepared by the direct deprotonation of bis(phenylsulfonyl)methane I in THF with one molar equivalent of MeLi, BuNa and BnK respectively. The geminal dianionic complexes [(PhSO2)2CLi2.THF]4, [(PhSO2)2CNa2.0.55THF]5 and [(PhSO2)2CK2]6 were similarly prepared by the reaction of I with two molar equivalents of MeLi, BuNa and BnK respectively in THF. NMR and MS solution studies of 1-3 are consistent with the formation of charge-separated species in DMSO media. Solutions studies of 4-6, in conjunction with trapping experiments, indicate that the dianions deprotonate DMSO and regenerate the monoanions 1-3. Crystallographic analysis of 1 revealed a 1D chain polymer in which the metal centers are chelated by the bis(sulfonyl) ligands and connect to neighboring units through Li-O(S) interactions. An unexpected feature of 1 is that the polymeric chains are homochiral, since the chelating ligands of the backbone adopt the same relative configuration. Also, the phenyl substituents of each chelate in 1 are oriented in a cisoid manner. The sodium derivative 2 adopts a related solid-state structure, where enantiomeric pairs of chains combine to give a 1D ribbon motif. The lithium bis(phenylsulfonyl)imides [(PhSO2)2NLi.THF]9 and [(PhSO2)2NLi.Pyr2]10 were also prepared and structurally characterized. In the solid state 9 has a similar connectivity to that found for 1 but with heterochiral chains. In comparison, the more highly solvated complex 10 forms a 1D polymeric arrangement without chelation of the ligands and with the phenyl substituents oriented in a transoid fashion. 相似文献
34.
It has been proved by L. Sweet that the octahedron functional equation implies the cube functional equation in all dimensionsn1. In this note we give an elementary proof of this theorem. 相似文献
35.
Albert Prodan Herman J.P. van Midden Sao turm Rok
itko Erik Zupani
J. Craig Bennett Robert MacDougall Pawel Starowicz 《Solid State Sciences》2009,11(9):1556-1561
High-resolution transmission electron microscopy (HRTEM), resistivity measurements and electronic band structure calculations performed by means of the extended Hückel tight-binding method are presented for the quasi one-dimensional compounds AxNb3Te4 (A = In, Tl, Zn, Ag, Hg). HRTEM and electron diffraction performed on pure Nb3Te4 at room- and liquid nitrogen temperatures, reveal both the basic structure and the low-temperature charge-density waves (CDWs) modulation. Resistivity vs. temperature plots show characteristic CDW anomalies, dependent on the type and concentration of the atoms, intercalated into the large hexagonal tunnels of the host structure. It is shown that intercalation of Tl and In results in a flattening of the corresponding Fermi surfaces and that CDW formation is largely dependent on the coincidence between the Fermi level EF and a small peak in the density of states spectrum, mainly developed from the Nb dz2 orbitals. This peak is positioned in a minimum between the filled and empty states of the spectrum and tends to split into a doublet as a consequence of intercalation. 相似文献
36.
Hill MS MacDougall DJ Mahon MF 《Dalton transactions (Cambridge, England : 2003)》2010,39(46):11129-11131
Reaction of pyridine with well defined magnesium hydride species results in heterocycle dearomatisation by a hydride transfer which occurs with the formation of magnesium compounds containing 1,2- and 1,4-dihydropyridide anions as the respective kinetic and thermodynamic products. 相似文献
37.
David G. Winkler Kerrie L. Faia Jonathan P. DiNitto Janid A. Ali Kerry F. White Erin E. Brophy Melissa M. Pink Jennifer L. Proctor Jennifer Lussier Christian M. Martin Jennifer G. Hoyt Bonnie Tillotson Erin L. Murphy Alice R. Lim Brian D. Thomas John R. MacDougall Pingda Ren Yi Liu Jeffery L. Kutok 《Chemistry & biology》2013,20(11):1364-1374
38.
39.
Pt, Ru and Pt/Ru nano-particles, synthesized in ethylene glycol solutions, are studied using infrared (IR) spectroscopy and high resolution transmission electron microscopy (HRTEM). The synthesis method allows the control of the mono- and bi-metallic catalyst particle sizes between 1 and 5.5 nm. The IR spectra of CO adsorbed (COads) on the Pt, Ru and bi-metallic Pt/Ru colloids are recorded as a function of the particle size. The stretching frequency of COads depends on the particle size and composition. Strong IR bands due to the stretching vibration of COads are observed between 2010 and 2050 cm−1 for the Pt nano-particles, while two IR bands between 2030 and 2060 cm−1 for linear bonded COads, and at lower wavenumbers between 1950 and 1980 cm−1 for bridged bonded COads, are found for the Ru particles. The IR spectra for the Pt/Ru nano-sized catalyst particles show complex behaviour. For the larger particles (>2 ± 0.5 nm), two IR bands representative of COads on Ru and Pt-Ru alloy phases, are observed in the range of 1970-2050 cm−1. A decrease in the particle size results in the appearance of a third band at ∼2020 cm−1, indicative of COads on Pt. The relative intensity of the band for COads on the Pt-Ru alloy vs. the Pt phase decreases with decreasing particle size. These results suggest that Ru is partially dissolved in the Pt lattice for the larger Pt/Ru nano-particles and that a separate Ru phase is also present. A Pt-Ru alloy and Ru phase is observed for all Pt/Ru particles prepared in this work. However, a decrease in particle size results in a decrease of the number of Pt and Ru atoms in the Pt-Ru alloy phase, as they are increasingly present as single Pt and Ru phases. 相似文献
40.