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11.
Glycerol is widely used as an additive to stabilize proteins in aqueous solution. We have studied the effect of up to 40 wt % glycerol on the crystallization of lysozyme from brine. As the glycerol concentration increased, progressively larger amounts of salt were needed to crystallize the protein. Like previous authors, we interpret this as evidence for glycerol changing the interaction between lysozyme molecules. We quantitatively model the interprotein interaction using a Derjaguin-Landau-Verwey-Overbeek potential. We find that the effect of glycerol can be entirely accounted for by the way it modifies the dielectric constant and refractive index of the solvent. Quantifying the interprotein interaction by the second virial coefficient, B(2), we find a universal crystallization boundary for all glycerol concentrations. 相似文献
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W. T. Flowers R. N. Haszeldine E. Henderson A. K. Lee R. D. Sedgwick 《Journal of polymer science. Part A, Polymer chemistry》1972,10(12):3489-3496
The techniques of mass spectrometry have been applied to the copolymer from tri-fluoronitrosomethane (CF3NO) and tetrafluoroethylene (C2F4). The copolymer yields spectra of a repetitive nature, typical of the repeating units in the polymer chain. Molecules with masses up to m/e 6400 can be distilled from the unfractionated polymer which is stable up to 220°C. Interpretation of the mass spectrum suggests a linear structure for the regular polymer. 相似文献
14.
Slow light in semiconductor quantum wells 总被引:2,自引:0,他引:2
Ku PC Sedgwick F Chang-Hasnain CJ Palinginis P Li T Wang H Chang SW Chuang SL 《Optics letters》2004,29(19):2291-2293
We demonstrate slow light via population oscillation in semiconductor quantum-well structures for the first time. A group velocity as low as 9600 m/s is inferred from the experimentally measured dispersive characteristics. The transparency window exhibits a bandwidth as large as 2 GHz. 相似文献
15.
R. D. Sedgwick Y. Y. Al-Sultan A. M. Abushihada 《Journal of polymer science. Part A, Polymer chemistry》1981,19(8):2007-2015
The degradation of low-density polyethylene in the presence of water as the degradative agent was studied at a temperature of 450°C and a pressure greater than 160 atm. The experimental work was conducted in an autoclave of 333-mL capacity. The products (gases, liquids, and solids) were analyzed by microanalytical methods and GC-spectroscopic techniques. The results indicate the presence of paraffins, olefines, dienes, and aromatics in the degradation products. The occurrence of aromatics in the products demonstrates the importance of this degradation procedure for obtaining these valuable materials. The present work (Part 1) is believed to be the first publication to discuss the production of aromatics from polyethylenes degradation. 相似文献
16.
Michael Arthurs Haroon Karodia Mark Sedgwick D.Antony Morton-Blake Christine J. Cardin Hans Parge 《Journal of organometallic chemistry》1985,291(2):231-251
A 1H NMR study of monosubstituted η-cyclopentadienyl-rhodium(I) complexes of type LLRh(C5H4X) and -iridium(I) complexes of type L2Ir(C5H4X) (L = ethene, LL = 1,3- or 1,5-diolefin; X = C(C6H5)3, CHO, or COOCH3) has been carried out. For complexes of both metals in which the neutral ligand is ethene or a non-conjugated diolefin the NMR spectra of the cyclopentadienyl protons are unusual in that H(2), H(5) resonate to high field either at room temperature or below.The corresponding NMR spectra for the cyclopentadienyl ring protons of complexes where the neutral ligand is a conjugated diene are, with one exception, normal.A single crystal X-ray structural analysis of (η4-2,4-dimethylpenta-1,4-diene)(η5-formylcyclopentadienyl)rhodium(I) (which exhibits an abnormal 1H NMR spectrum) reveals substantial localisation of electron density in the C(3)C(4) Cp ring bond (1.283(33) Å) which may be consistent with a contribution from an ‘allyl-ene’ rotamer to the ring—metal bonding scheme. An extended Hückel calculation with self consistent charge iteration was performed on this complex.The results predict a greater Mulliken overlap population for the C(3)C(4) bond in the cyclopentadienyl ring and show that the localisation is dependent on both the Cp ring substituent and the nature of the diolefin. The mass spectral fragmentation patterns of some representative diene complexes of iridium(I) and rhodium(I) are presented. 相似文献
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自由曲面光学透镜注射成型误差因素研究 总被引:1,自引:1,他引:0
自由曲面光学透镜注射成型误差对其光学性能将产生直接影响。注射成型过程中,注射工艺参数组合的优劣,直接影响成型误差的大小。为了获得高精密度的光学元件,就热塑性塑料的注射温度、模具温度、注射压力、保压压力及保压时间等主要工艺参数,对注射成型误差的影响进行综合研究,并且进行了实验验证。研究结果表明:适当提高注射温度与模具温度,同时采用高压注射、高压保压以及快速保压工艺,可显著降低注塑工件的体积收缩率,显著提高面形精密度,其光学表面面形误差小于0.1μm。可为注射工艺设计提供合理的依据。 相似文献
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Jiří Matoušek Eric Sedgwick Martin Tancer Uli Wagner 《Israel Journal of Mathematics》2016,212(1):37-79
We consider two systems (α1, …, αm) and (β1, …,βn) of simple curves drawn on a compact two-dimensional surface M with boundary. 相似文献