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21.
A stirring bar type agitation system has been designed and characterized for the accelerating rate calorimeter (ARC). The device allows stirring of the contents of a standard ARC sample container at stirring rates of up to 500 rev. min?1, depending on sample viscosity. Experiments on a well-characterized thermal decomposition reaction, such as that of di-t-butyl peroxide, indicate that the device does not degrade the measurement of the energy of reaction, ΔEv, the Arrhenius activation energy, Ea, or the pre-exponential factor, A.The utility of this stirring apparatus is demonstrated by examining the runaway data of a suspension polymerization. The results indicate that a polymerization “kill” agent can be successfully used for that particular reaction. 相似文献
22.
Wei‐Lie Xiao Dr. Chun Lei Jie Ren Tou‐Gen Liao Jian‐Xin Pu Charles U. Pittman Jr. Prof. Yang Lu Prof. Yong‐Tang Zheng Prof. Hua‐Jie Zhu Prof. Han‐Dong Sun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(36):11584-11592
Rubrifloradilactone C ( 4 ), a novel bioactive nortriterpenoid, along with four other nortriterpenoids ( 1 – 3 , 5 ) were isolated from Schisandra rubriflora. The structure of 4 was determined by extensive NMR spectral analysis, computational evidence by using the GIAO method at the B3LYP/6–311++G(2d,p)//B3LYP/6–31G(d) levels, and X‐ray analysis. DFT at the B3LYP/6–311+G(d,p) level was selected to clarify the key mechanistic steps in the formation of 1 and 4 through transition‐state (TS) investigations. The effect of enzymes on the TS barriers was considered by using the polarized continuum model. Other possible products based on the new mechanism were predicted. 相似文献
23.
James C. Tou 《Journal of polymer science. Part A, Polymer chemistry》1984,22(12):3851-3864
Thermogravimetric-mass spectrometric (TG/MS) and differential scanning calorimetric (DSC) techniques were used in the characterization of oxidative and nonoxidative degradation reactions of a highly crosslinked divinylbenzene/styrene copolymer. When the copolymer was subjected to a temperature-programmed air environment, four exothermic reactions were detected. The initial small exothermic reaction, starting at ca. 125°C and reaching its maximum at ca. 180°C, was presumed to result from the decomposition of peroxides. The second exothermic reaction, which overlapped with the initial one and peaked at ca. 270°C, was attributed to oxidation with a significant amount of oxygen uptake and liberation of some gaseous products such as CO2, styrene, benzaldehyde, ethylstyrene, and ethylbenzaldehyde. The strongest exothermic reaction took place at ca. 290–380°C and had its peak at ca. 360°C. Associated with this reaction was the generation of many gaseous pyrolysates, as given above. The exothermic reaction continued at a relatively constant rate from ca. 380°C to the maximum temperature of the experiment (500°C) with the release of only one gaseous product (CO2). The initial exothermic reaction can be eliminated by controlled thermal decomposition of peroxides; therefore, a more thermally stable polymer can be obtained. Exothermic reactions, starting at ca. 170°C, were observed. Pyrolytic reactions in an inert gas were also studied. 相似文献
24.
We report magnetic susceptibility measurements on a layered superconductor Li0.48(THF)0.3HfNCl having Tc approximately 26 K. The present study revealed that (a) the Fermi level density of states is small, N*(EF) approximately 0.25 states/(eV spin f.u.), (b) mass enhancement is negligible, gamma; approximately 1, (c) electron-phonon coupling is weak, lambda(ep)<1, (d) exchange enhancement is negligible, 1/(1+F(a)0) approximately 1, and (e) electronic density parameter is large, r(2D)s approximately 10.3 (i.e., low-carrier density). It is difficult to explain the origin of the high Tc in terms of the conventional phonon (BCS) mechanism of superconductivity. 相似文献
25.
Leszek Pazderski Jaromír Toušek Jerzy Sitkowski Lech Kozerski Edward Szłyk 《Magnetic resonance in chemistry : MRC》2009,47(8):658-665
1H, 13C and 15N nuclear magnetic resonance studies of gold(III), palladium(II) and platinum(II) chloride complexes with phenylpyridines (PPY: 4‐phenylpyridine, 4ppy; 3‐phenylpyridine, 3ppy; and 2‐phenylpyridine, 2ppy) having the general formulae [Au(PPY)Cl3], trans‐/cis‐[Pd(PPY)2Cl2] and trans‐/cis‐[Pt(PPY)2Cl2] were performed and the respective chemical shifts (δ, δ and δ) reported. 1H, 13C and 15N coordination shifts (i.e. differences between chemical shifts of the same atom in the complex and ligand molecules: , , ) were discussed in relation to the type of the central atom (Au(III), Pd(II) and Pt(II)), geometry (trans‐/cis‐) and the position of a phenyl group in the pyridine ring system. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
26.
Tou T.Y. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1995,23(5):870-873
The technique of multislit streak photography was applied to investigate the plasma focus in the steady-state rundown phase. This enabled the axial and radial positions, and the rundown velocity of the current-carrying plasma sheath to be measured simultaneously. From these measurements, the radial profile of the plasma sheath in the plasma focus tube could be reconstructed and the plasma current was calculated. These calculated currents represented about 70% of the total circuit current flowing out of the capacitor bank, and these agreed with earlier results which were obtained via computer simulations of the measured voltage and current waveforms 相似文献
27.
Tou T.Y. Seow W.S. Siew W.O. Beak K.W. Chen Y.H. Low K.S. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1993,21(6):696-700
The air breakdown times of second spark formation, geometrically in series with trigatron switching, are studied and compared to that of a triggered spark gap. Despite a large breakdown jitter of ⩾1 μs in the trigatron, the latter is not observed to affect the electrical closure times of the series-connected second spark gap, which is triggered largely as a result of their direct electrical and optical coupling. While most of the multistage spark gaps are designed for fast and precision switching of high voltages, the air breakdown times of the second spark formation find a number of useful applications, particularly in achieving uniform glow discharge in pulsed gas lasers 相似文献
28.
Yutaka Maniwa Hirokazu Sakamoto Hideki Tou Yuji Aoki Hideyuki Sato Fumihiko Shimizu 《Molecular Crystals and Liquid Crystals》2013,570(2):497-502
Abstract NMR spectra of 29Si and 137Ba in silicon clathrate compounds, NaxBaySi46, NaxSi136 and Ba8 T xSi46 (where T = Au, Ag, and Cu) are reported. We found that the local density of states at the Fermi level increases with rising superconducting transition temperature. The silicon Sl site was suggested to hybridize with Ba-orbital in the superconducting clathrate and has a large local density of states. 相似文献
29.
Physical vapor processes using glow plasma discharge are widely employed in microelectronic industry. In particular magnetron sputtering is a major technique employed for the coating of thin films. This paper addresses the influence of direct current (DC) plasma magnetron sputtering parameters on the material characteristics of polycrystalline copper (Cu) thin films coated on silicon substrates. The influence of the sputtering parameters including DC plasma power and argon working gas pressure on the electrical and structural properties of the thin Cu films was investigated by means of surface profilometer, four-point probe and atomic force microscopy. 相似文献
30.
Kwek K.H. Tou T.Y. Lee S. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1990,18(5):826-830
The current carrying plasma sheath in a 12-kJ plasma focus is studied in the axial run-down phase by means of the Schlieren technique. Subnanosecond ultraviolet light pulses from a preionized, transversely excited, atmospheric nitrogen laser provide sufficiently fine temporal and spatial resolution for such investigation where the propagation speed of the current sheath is of the order of 10 cm/μs. It is observed that the current sheath grows thicker if it is driven at speeds beyond an optimum value of about 8 cm/μs (when the neutron yield is maximum). The thickening of the sheath is seen as an effect of the ratio of the specific heats. At the speed of 11 cm/μs, the effect of the temperature gradient at the electrode surface broadens the sheath further. Slow driving speeds are observed to result in an inefficient and leaky position 相似文献