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31.
We have carried out multi-station TV observations since 1994 in order to determine the orbit of the Arietid daytime meteor
stream. In 1999, one possible Arietid meteor was recorded by our simultaneous observations and its orbit was determined. In
2003, two Arietid meteors were observed from two stations of our observing site, those orbits were determined precisely, the
orbital elements were in good agreement with each other. This is the first time that determination of the precise orbit of
the Arietids has been made from optical observations. The orbit of these Arietid meteors, and comparison with the orbit obtained
from radar observations are discussed. 相似文献
32.
Temperature-influenced dynamics of small dust particles 总被引:1,自引:0,他引:1
M. Kocifaj † J. Klaka H. Horvath 《Monthly notices of the Royal Astronomical Society》2006,370(4):1876-1884
The motion of spherical dust particles under the action of gravity, electromagnetic radiation force and Lorentz force (LF) is studied theoretically for materials with temperature-dependent dielectric functions in the visible (VIS) spectral range. Even a weak variation of the optical constants with heliocentric distance may influence predominately a long-term dynamical behaviour of submicron-sized and small micron-sized dust grains. It is shown that the lifetime of carbonaceous or Si particles may change by several tens of per cent because of the temperature dependence of particle refractive indices. The orbital inclination is the most evident difference between the evolution of a dust particle with temperature-dependent optical properties and one without. While carbonaceous 2-μm-sized particles with optical constants independent of temperature may evolve in orbits with inclinations greater than an initial value, grains of the same size with variable refractive indices will be spread along orbits characterized with inclinations lower than the initial one. Here the temperature works as a separation factor for particles having slightly different temperature dependences of the optical constants. 相似文献
33.
宇宙尘物质是太阳系最原始的考古样品,比陨星更具有太阳系初始物质的特性,其整体成分更能代表太阳星云的初始丰度和同位素特征。初步综述了目前国内外对宇宙尘的探测、捕集和研究现状以及最新研究进展. 相似文献
34.
Jozef Klačka 《Earth, Moon, and Planets》1994,66(2):213-216
The action of the solar corpuscular radiation on the rotational properties of small interplanetary dust particles is investigated. It is shown that the solar wind increases the angular momentum (spin) of the particle. Analytic solutions are presented for dominant terms in which quantities of the orders (v/u)
n
,n 1, are neglected (v is the orbital velocity of dust particle around the Sun andu is the speed of the solar wind particles). 相似文献
35.
The unusually low amplitude anisotropic wave train events (LAEs) in cosmic ray intensity using the ground based Deep River
neutron monitor data has been studied during the period 1991–94. It has been observed that the phase of the diurnal anisotropy
for the majority of the LAE events remains in the co-rotational direction. However, for some of the LAE events the phase of
the diurnal anisotropy shifts towards earlier hours as compared to the annual average values. On the other hand, the amplitude
of the semi-diurnal anisotropy remains statistically the same, whereas phase shift-towards later hours; a similar trend has
also been found in case of tri-diurnal anisotropy. The high-speed solar wind streams do not play a significant role in causing
the LAE events. The occurrence of LAE is independent of the nature of the Bz component of IMF polarity.
Published in Astrofizika, Vol. 50, No. 2, pp. 313–324 (May 2007). 相似文献
36.
Xi-Zhen Zhang 《中国天文和天体物理学报》2007,7(5):712-720
Ground-based observation of Interplanetary Scintillation(IPS)is an important ap- proach of monitoring solar wind speed.We describe both the principle and method of ob- serving the solar wind speed by using the normalized cross-spectrum of simultaneous dual- frequency IPS measurement.The effects of the solar wind properties and the angular size of the scintillation source on the measurement of solar wind speed are investigated by numerical analysis.We carry out a comparison of this method with the traditional single station-single frequency method.We outline a new IPS observation system using this method now under construction at the National Astronomical Observatories,CAS(NAOC). 相似文献
37.
C. H. Mandrini M. S. Nakwacki G. Attrill L. van Driel-Gesztelyi P. Démoulin S. Dasso H. Elliott 《Solar physics》2007,244(1-2):25-43
Coronal dimmings are often present on both sides of erupting magnetic configurations. It has been suggested that dimmings
mark the location of the footpoints of ejected flux ropes and, thus, their magnetic flux can be used as a proxy for the flux
involved in the ejection. If so, this quantity can be compared to the flux in the associated interplanetary magnetic cloud
to find clues about the origin of the ejected flux rope. In the context of this physical interpretation, we analyze the event,
flare, and coronal mass ejection (CME) that occurred in active region 10486 on 28 October 2003. The CME on this day is associated
with large-scale dimmings, located on either side of the main flaring region. We combine SOHO/Extreme Ultraviolet Imaging
Telescope data and Michelson Doppler Imager magnetic maps to identify and measure the flux in the dimming regions. We model
the associated cloud and compute its magnetic flux using in situ observations from the Magnetometer Instrument and the Solar Wind Electron Proton Alpha Monitor aboard the Advance Composition Explorer. We find that the magnetic fluxes of the dimmings and magnetic cloud are incompatible, in contrast to what has been found
in previous studies. We conclude that, in certain cases, especially in large-scale events and eruptions that occur in regions
that are not isolated from other flux concentrations, the interpretation of dimmings requires a deeper analysis of the global
magnetic configuration, since at least a fraction of the dimmed regions is formed by reconnection between the erupting field
and the surrounding magnetic structures. 相似文献
38.
George J. Flynn 《Earth, Moon, and Planets》2004,95(1-4):361-374
Meteorites, generally 1 cm or larger in size that are believed to sample asteroids, and interplanetary dust particles (IDPs),
generally 5–50 μm in size that are believed to sample both asteroids and comets, span the size range of the meteors. Thus,
the physical properties of the meteorites and the IDPs are likely to constrain the properties of the meteors and their parent
bodies. Measurements of the density, porosity, longitudinal and transverse speeds of sound, elastic modulus, and bulk modulus,
as well as imaging of the internal structure by Computed Microtomography indicate that unweathered samples of chondritic meteorites
are more porous and have lower sound velocities than compact terrestrial rocks. In general, the IDPs are even more porous
than the chondritic meteorites. The impact energy per unit target mass required to produce a barely catastrophic disruption
(Q
*
D) for anhydrous ordinary chondrite meteorites is twice that for terrestrial basalt or glass, indicating that collisional disruption
of anhydrous meteorites requires more energy than for a compact basalt. These results indicate that most stone meteors are
likely to be weak, porous objects, and that the parent bodies of the anhydrous stone meteorites are likely to be more difficult
to disrupt than compact terrestrial basalt. 相似文献
39.
We present the results of a study of meteoroid bulk densities determined from meteor head echoes observed by radar. Meteor
observations were made using the Advanced Research Projects Agency Long-Range Tracking And Instrumentation Radar (ALTAIR).
ALTAIR is particularly well suited to the detection of meteor head echoes, being capable of detecting upwards of 1000 meteor
head echoes per hour. Data were collected for 19 beam pointings and are comprised of approximately 70 min. of VHF observations.
During these observations the ALTAIR beam was directed largely at the north apex sporadic source. Densities are calculated
using the classical physical theory of meteors. Meteoroid masses are determined by applying a full wave scattering theory
to the observed radar cross-section. Observed meteoroids are predominantly in the 10−10 to 10−6 kg mass range. We find that the vast majority of meteoroid densities are consistent with low density, highly porous objects
as would be expected from cometary sources. The median calculated bulk density was found to be 900 kg/m3. The orbital distribution of this population of meteoroids was found to be highly inclined. 相似文献
40.
Carey Lisse 《Earth, Moon, and Planets》2002,90(1-4):497-506
We present the results of an ongoing optical/thermal infraredphotometric imaging survey of thedust mass loss and nuclear size
ofcomets. We find an evolution with time of the kind of dust emittedfrom a comet's surface. Our results indicate that the
mass loss ratefrom the short period comets alone is enough to supply the interplanetary dust (IPD) complexagainst losses.
We conclude that the nature of the IPD cloud haschanged over time, with small particles dominating early, and largerparticles
dominating in the present era. The rate of destruction of short period (SP)comets due to sublimation mass loss is found to
be low compared to therate of surface mantle formation, but fast compared to the rate of their dynamical removal from the
inner solar system. 相似文献