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253.
A review of shell structure for spherical and a variety of deformed nuclei is presented. The microscopic-macroscopic method of Strutinsky is used to calculate potential energy surfaces with the pure harmonic oscillator and the modified harmonic oscillator. New sets of “magic numbers” for a variety of different prolate, oblate and axially asymmetric shapes are generated. Experimental evidence for the special stability caused by these shell effects is presented with special emphasis on the lightest and heaviest nuclei where the effects are most pronounced. The radial diffuseness parameter is treated as a Strutinsky variable and its significance in extrapolating into the superheavy region considered. The calculation of shell effects for high spin states is also reviewed. 相似文献
254.
A large change in the surface and interface potential of Pd-films on SiO2 is observed at a constant ratio between hydrogen and oxygen pressure in the ambient. This observation, which is most probably due to a competition between hydrogen and oxygen for the same dissociative adsorption sites, is described in this communication. Furthermore the potential measurements indicate the presence of another type of hydrogen adsorption sites on the oxygen covered surface. 相似文献
255.
H. Bladh J. Johnsson J. Rissler H. Abdulhamid N.-E. Olofsson M. Sanati J. Pagels P.-E. Bengtsson 《Applied physics. B, Lasers and optics》2011,104(2):331-341
Laser-induced incandescence (LII) is a versatile technique for quantitative soot measurements in flames and exhausts. When
used for particle sizing, the time-resolved signals are analysed as these will show a decay rate dependent on the soot particle
size. Such an analysis has traditionally been based on the assumption of isolated primary particles. However, soot particles
in flames and exhausts are usually aggregated, which implies loss of surface area, less heat conduction and hence errors in
estimated particle sizes. In this work we present an experimental investigation aiming to quantify this effect. A soot generator,
based on a propane diffusion flame, was used to produce a stable soot stream and the soot was characterised by transmission
electron microscopy (TEM), a scanning mobility particle sizer (SMPS) and an aerosol particle mass analyzer coupled in series
after a differential mobility analyzer (DMA-APM). Despite nearly identical primary particle size distributions for three selected
operating conditions, LII measurements resulted in signal decays with significant differences in decay rate. However, the
three cases were found to have quite different levels of aggregation as shown both in TEM images and mobility size distributions,
and the results agree qualitatively with the expected effect of diminished heat conduction from aggregated particles resulting
in longer LII signal decays. In an attempt to explain the differences quantitatively, the LII signal dependence on aggregation
was modelled using a heat and mass transfer model for LII given the primary particle and aggregate size distribution data
as input. Quantitative agreement was not reached and reasons for this discrepancy are discussed. 相似文献
256.
Jan E. Åman Stefan Åminneborg Ingemar Bengtsson Narit Pidokrajt 《General Relativity and Gravitation》2008,40(12):2557-2567
In 3+1 dimensions there are anti-de Sitter quotients which are black holes with toroidal event horizons. By analytic continuation
of the Schwarzschild-anti-de Sitter solution (and appropriate identifications) one finds two one parameter families of spacetimes
that contain these quotient black holes. One of these families consists of B-metrics (“bubbles of nothing”), the other of
black hole spacetimes. All of them have vanishing conserved charges.
I. Bengtsson was supported by VR. 相似文献
257.
“The laser-induced incandescence (LII) signal is proportional to soot volume fraction” is an often used statement in scientific
papers, and it has – within experimental uncertainties – been validated in comparisons with other diagnostic techniques in
several investigations. In 1984 it was shown theoretically in a paper by Melton that there is a deviation from this statement
in that the presence of larger particles leads to some overestimation of soot volume fractions. In the present paper we present
a detailed theoretical investigation of how the soot particle size influences the relationship between LII signal and soot
volume fraction for different experimental conditions. Several parameters have been varied; detection wavelength, time and
delay of detection gate, ambient gas temperature and pressure, laser fluence, level of aggregation and spatial profile. Based
on these results we are able, firstly, to understand how experimental conditions should be chosen in order to minimize the
errors introduced when assuming a linear dependence between the signal and volume fraction and secondly, to obtain knowledge
on how to use this information to obtain more accurate soot volume fraction data if the particle size is known.
PACS 42.62.-b; 44.40.+a; 61.46.Df; 78.70.-g; 65.80.+n 相似文献