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排序方式: 共有61条查询结果,搜索用时 15 毫秒
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T.B. Settersten A. Dreizler B.D. Patterson P.E. Schrader R.L. Farrow 《Applied physics. B, Lasers and optics》2003,76(4):479-482
This study reports on photochemical interferences affecting atomic oxygen detection using two-photon laser-induced fluorescence
at 226 nm. In contrast to previous studies in which molecular oxygen was proven to be the relevant photochemical precursor
molecule in a hydrogen-fueled flame, the present investigations were carried out in a laminar diffusion flame of methane and
air. The most significant interferences were found at the fuel side of the flame in the absence of molecular oxygen, and vibrationally
excited carbon dioxide was identified as the most probable precursor molecule for the photochemical production of oxygen atoms.
Received: 11 December 2002 / Revised version: 10 March 2003 / Published online: 16 April 2003
RID="*"
ID="*"Corresponding author. Fax: +1-925/294-2595, E-mail: tbsette@sandia.gov 相似文献
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This solid state 13C NMR study confirms, for coals, and extends, for air-oxidized coals, the claim that the Bishop and Ward strong aqueous-acid coal demineralization procedure [M. Bishop, D.L. Ward, Fuel 37 (1958) 191.] does not lead to the formation of detectable levels of cross-links in the organic matrix of these materials. The study was prompted by the demonstration that polymerization accompanies strong acid demineralization in lignin, and the recognition that the chemical environment created in air-oxidized coals contains introduced reactive functionality similar to that in the lignin. In particular, both contain oxidized benzylic carbon functionality that can undergo acid-catalyzed polymerization reactions. For two coals of differing rank, no acid-induced cross-link formation has been observed in the pristine or air-oxidized coals, within the 5 parts per thousand (ppt) sensitivity of the NMR technique used in this study. 相似文献
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Fang G Shi Y Maclennan JE Clark NA Farrow MJ Walba DM 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):17482-17488
Photosensitive surfaces treated to have in-plane structural anisotropy by illumination with polarized light can be used to orient liquid crystals (LCs). Here we report a detailed study of the dynamic behavior of this process at both short and long times, comparing the ordering induced in the bare active surface with that of the LC in contact with the surface using a high-sensitivity polarimeter that enables detailed characterization of the anisotropy of the active surface. The experiments were carried out using self-assembled monolayers (SAMs) made from dimethylaminoazobenzene covalently bonded to a glass surface through a triethoxysilane terminus. This surface gives planar alignment of the liquid crystal director with an azimuthal orientation that can be controlled by the polarization of actinic light. We find a remarkable long-term collective interaction between the orientationally ordered SAM and the director field of the LC: while an azobenzene based SAM in contact with an isotropic gas or liquid relaxes to an azimuthally isotropic state in the absence of light due to thermal fluctuations, an orientationally written SAM in contact with LC in the absence of light can maintain the LC director twist permanently, that is, the SAM is capable of providing azimuthal anchoring to the LC even in the presence of a torque about the surface normal. We find that the short-time, transient LC reorientation is limited by the weak azimuthal anchoring strength of the SAM and by the LC viscosity. 相似文献
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David M. Walba Charles A. Liberko Eva Korblova Matthew Farrow Thomas E. Furtak Bruce C. Chow Daniel K. Schwartz Adam S. Freeman Kenneth Douglas Scott D. Williams Arthur F. Klittnick Noel A. Clark 《Liquid crystals》2004,31(4):481-489
A simple procedure for the preparation of octadecylsiloxane self-assembled monolayers (SAMs) on float glass substrates is described. The method utilizes commercial octadecyltriethoxysilane, OTE: n-C18H37Si(OCH2CH3)3, as the SAM precursor, with deposition accomplished in toluene solution using n-butylamine as catalyst. This synthetic approach obviates the use of the problematic trichlorosilanes typically required for the preparation of high quality SAMs, and is characterized by a wide 'process window,' utilizing off-the-shelf reagents without special handling. 相似文献
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P. Atkinson M.B. Ward S.P. Bremner D. Anderson T. Farrow G.A.C. Jones A.J. Shields D.A. Ritchie 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):21
Conventional electron-beam lithographic patterning of GaAs substrates followed by reactive-ion etching of small holes has been successfully used to control the nucleation of InAs dots. We have observed >50% single dot occupancy for holes wide and deep and show that the dot occupancy and dot size can be varied by changing the size of the holes. Luminescence from an array of these site-controlled dots has been demonstrated. Thus this use of substrate patterning is a viable technique to controllably place single dots at pre-determined positions in devices. 相似文献
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A study has been made of intimate metal-InP contacts prepared by metal beam epitaxy in ultra-high vacuum Oxygen and carbon contamination was removed from the (001)InP surface by bombardment with 500 eV Ar+ ions. On annealing to 250°C, In islands appeared on the surface and c(2×8) reconstruction was observed. Gold and silver films were found to grow epitaxially on the InP at ?40°C but the electrical properties indicate greatly reduced Schottky barrier heights and non-ideal current-voltage characteristics which may be attributed to non-stoichiometry and damage at the semiconductor surface resulting from the ion bombardment. 相似文献
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Heats of formation of rate-earth monosulfate complexes have been measured calorimetrically for the ions La3+, Sm3+, Tb3+, and Er3+, in D2O and H2O solvents. Within the limits of experimental error there is no evidence for a solvent isotope effect on the heat and entropy changes of these complexation reactions.This paper was abstracted from W.D.W.'s Ph.D. dissertation, May 1973. 相似文献