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1.
The synthesis of the alkaloid jamtine and the antidepressant paroxetine have been addressed by a strategy involving asymmetric desymmetrisation of prochiral imides by a chiral lithium amide base. A short reaction sequence, starting with a cyclohexane fused succinimide, led to the structures originally reported for the alkaloid jamtine and its derived N-oxide. The structures synthesised are shown not to correspond with those originally reported. A second sequence involves desymmetrisation of a 4-arylglutarimide, and provides a short enantioselective synthesis of the drug substance paroxetine. 相似文献
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Cyclisation of the title compounds leads to mixtures of the expected 4H-cyclopental[b]pyrrol-4-ones (1), the corresponding 6-ones (3) by a single rearrangement, and the cyclopenta[c]pyrrol-4-ones (4) by a double rearrangement, the proportions depending upon the substituents.The 1H NMR spectra of 2-methyl-4H-cyctopenta[b]thiophen-6-one (3f) shows 6J long range coupling, but this is absent in the corresponding pyrroles (3c,d). The 13C spectra of 1 and 3 cannot be interpreted on the basis of substituent chemical shifts in pyrroles and thiophens, and are clearly -CH = CH-X (X = NMe, NPh, S) bridged derivatives of cyclopent-2-enone. 相似文献
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An eco‐epidemiological predator–prey model where predators distinguish between susceptible and infected prey 下载免费PDF全文
David Greenhalgh Qamar J. A. Khan Joseph S. Pettigrew 《Mathematical Methods in the Applied Sciences》2017,40(1):146-166
A predator–prey model with disease amongst the prey and ratio‐dependent functional response for both infected and susceptible prey is proposed and its features analysed. This work is based on previous mathematical models to analyse the important ecosystem of the Salton Sea in Southern California and New Mexico where birds (particularly pelicans) prey on fish (particularly tilapia). The dynamics of the system around each of the ecologically meaningful equilibria are presented. Natural disease control is considered before studying the impact of the disease in the absence of predators and the interaction of predators and healthy prey and the disease effects on predators in the absence of healthy prey. Our theoretical results are confirmed by numerical simulation. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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F. Liu K.J. Daun V. Beyer G.J. Smallwood D.A. Greenhalgh 《Applied physics. B, Lasers and optics》2007,87(1):179-191
Laser-induced incandescence (LII) of nanoparticles at low pressures has received some attention in recent years as a particle
sizing technique or a technique for inferring the mean value of the absorption function of the particle material. In this
paper, we are concerned with some fundamental issues in the theory of LII with particular attention paid to those encountered
at very low pressures. The commonly adopted Rayleigh approximation for particle laser energy absorption and subsequent thermal
emission is critically evaluated against the Mie solution in the range of size parameter relevant to LII. The Rayleigh approximation
can cause significant error in particle laser energy absorption rate, especially when shorter wavelengths are used, and potentially
in the particle temperature inferred from the two-color LII. We also demonstrate that claims that low-pressure LII can be
used for particle sizing are flawed, due to the use of an incorrect expression for radiation heat loss rate from the particles
in this regime, and unjustified neglect of particle sublimation heat loss. Using the currently best available carbon sublimation
rate expression and physical parameters, the relative importance of heat conduction, thermal radiation, and sublimation heat
loss from an isolated carbon particle was investigated for different ambient pressures, particle temperatures and particle
diameters. To ensure particle radiation heat loss is dominant over conduction and sublimation the ambient pressure and the
particle temperature should be kept respectively lower than 10-4 atm and below about 2800 K. Under these conditions the effective temperature of a particle ensemble containing non-aggregated
polydisperse primary particles to the power of -4 is proportional to the mean value of the particle absorption function, provided
the particles are in the Rayleigh regime in the near infrared. The effect of aggregation on particle absorption and emission
is briefly discussed.
PACS 44.10.+i; 44.40.+a; 61.46Df 相似文献
7.
A new asymmetric approach to the erythrinan alkaloid system is described, which involves chiral base desymmetrisation of a ring fused imide and a 6-exo-trig radical cyclisation as the key steps. 相似文献
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D.A. Greenhalgh F.M. Porter S.A. Barton 《Journal of Quantitative Spectroscopy & Radiative Transfer》1985,34(1):95-99
A simple phenomenological model for predicting high-temperature linewidths is described. The rotationally inelastic relaxation time is calculated by using a polynomial inverse-energy-gap model. From this time, the linewidths may be calculated and ambient pressure linewidths may then be used to determine the polynomial coefficients and predict high-temperature linewidths. A detailed comparison with known nitrogen linewidths is given. The relaxation rates obtainable from the model may also be used to calculate pressure-narrowing effects for vibrational Q branches. 相似文献