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31.
A. K. Burnham R. K. Weese A. P. Wemhoff J. L. Maienschein 《Journal of Thermal Analysis and Calorimetry》2007,89(2):407-415
Prediction of thermal explosions using chemical kinetic models dates back nearly a century. However, it has only been within
the past 25 years that kinetic models and digital computers made reliable predictions possible. Two basic approaches have
been used to derive chemical kinetic models for high explosives: [1] measurement of the reaction rate of small samples by
mass loss (thermogravimetric analysis, TG), heat release (differential scanning calorimetry, DSC), or evolved gas analysis
(mass spectrometry, infrared spectrometry, etc.) or [2] inference from larger-scale experiments measuring the critical temperature
(T
m, lowest T for self-initiation), the time to explosion as a function of temperature, and sometimes a few other results, such as temperature
profiles. Some of the basic principles of chemical kinetics involved are outlined, and major advances in these two approaches
through the years are reviewed. 相似文献
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Five squirrel monkeys were exposed for 1, 2, 4, 8, 16, 24, and 48 h to a 375--750-Hz band noise at an overall SPL of 95 dB. The TTS4.5 growth pattern for the 750-Hz test frequency was biphasic and did not reach an asymptote after 48 h of exposure. For all exposures, the mean thresholds of the five monkeys returned to within 5 dB of the preexposure mean 20 h after exposure. Recovery curves from all exposures at the 750-Hz test frequency appeared biphasic. Increasing SPL from 95 to 105 dB increased TTS4.5 by 4 dB at 750 Hz for a 1-h exposure. Recovery from the 105-dB exposure followed the same pattern as recovery from the 95-DB exposure. When compared with data collected from human subjects under similar conditions, these experiments indicate that the growth and recovery of TTS in squirrel monkeys are sufficiently similar to growth and recovery in man to justify further comparative investigation. 相似文献
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35.
Lipid-lowering effects of ethyl 2-phenacyl-3-aryl-1H-pyrrole- 4-carboxylates in rodents 总被引:3,自引:0,他引:3
Holub JM O'Toole-Colin K Getzel A Argenti A Evans MA Smith DC Dalglish GA Rifat S Wilson DL Taylor BM Miott U Glersaye J Lam KS McCranor BJ Berkowitz JD Miller RB Lukens JR Krumpe K Gupton JT Burnham BS 《Molecules (Basel, Switzerland)》2004,9(3):134-157
A series of substituted 2-phenacyl-3-phenyl-1H-pyrrole-4-carboxylates were prepared from substituted acetophenones in 6 steps. The final condensations between a chloroenal and an aminoketone were carried out under neutral conditions in parallel to yield the series listed below. Selected pyrrole derivatives proved to be potent hypolipidemic agents lowering serum triglyceride concentrations in CF-1 male mice after 14 days of I.P. administration. One agent orally lowered serum cholesterol in Sprague-Dawley male rats at 2mg/kg/day after 14 days. The agents demonstrated a lowering of mouse serum LDL- cholesterol levels and selected compounds showed an elevation of serum HDL-cholesterol levels. The cholesterol concentrations in the liver were raised while the cholesterol and triglyceride contents of the aorta were significantly lowered by the selected trisubstituted pyrrole. 相似文献
36.
Newman RS Clouse SA Burnham JL 《The Journal of the Acoustical Society of America》2001,109(3):1181-1196
The effect of talker and token variability on speech perception has engendered a great deal of research. However, most of this research has compared listener performance in multiple-talker (or variable) situations to performance in single-talker conditions. It remains unclear to what extent listeners are affected by the degree of variability within a talker, rather than simply the existence of variability (being in a multitalker environment). The present study has two goals: First, the degree of variability among speakers in their /s/ and /S/ productions was measured. Even among a relatively small pool of talkers, there was a range of speech variability: some talkers had /s/ and /S/ categories that were quite distinct from one another in terms of frication centroid and skewness, while other speakers had categories that actually overlapped one another. The second goal was to examine whether this degree of variability within a talker influenced perception. Listeners were presented with natural /s/ and /S/ tokens for identification, under ideal listening conditions, and slower response times were found for speakers whose productions were more variable than for speakers with more internal consistency in their speech. This suggests that the degree of variability, not just the existence of it, may be the more critical factor in perception. 相似文献
37.
Charles K. Bradsher Weldon S. Burnham Mary F. Zinn 《Journal of heterocyclic chemistry》1970,7(4):779-782
2-Methyl-3-(2-pyridyl)quinoline (1) with a bromomethyl ketone or ethyl bromoacetate yields 6-methyl-12-acylindolizino[1,2-c]quinolinium bromides ( 5–9 ). The acyl derivatives can be deacylated in acid yielding 6-methyl indolizino[1,2-c]quinolinium salts ( 4 ). Benzoylation of 4 yields the 12-benzoyl derivative ( 6 ). The deacylation product ( 4 ) has been synthesized from 2-acetamidophenacyl bromide ( 10 ) and 2-pyridylacetone ( 12 ). 相似文献
38.
We describe a new nematic liquid-crystal colloid system which is characterized by both charge stabilization of the particles and an interaction force. We estimate the effective charge of the particles by electrophoretic measurements and find that in such systems the director anchoring energy W is very low and the particles have little director distortion around them. The interaction force is created by producing a radial distribution of the nematic order parameter around a locally isotropic region created by ir laser heating. We theoretically describe this as being due to the induced flexoelectric polarization, the quadrupolar symmetry of which provides the required long-range force acting on charged particles. 相似文献
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