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1.
《Astroparticle Physics》2002,16(4):183-386
Frequency distributions of local muon densities in high-energy extensive air showers (EAS) are presented as signature of the primary cosmic ray energy spectrum in the knee region. Together with the gross shower variables like shower core position, angle of incidence, and the shower sizes, the KASCADE experiment is able to measure local muon densities for two different muon energy thresholds. The spectra have been reconstructed for various core distances, as well as for particular subsamples, classified on the basis of the shower size ratio Nμ/Ne. The measured density spectra of the total sample exhibit clear kinks reflecting the knee of the primary energy spectrum. While relatively sharp changes of the slopes are observed in the spectrum of EAS with small values of the shower size ratio, no such feature is detected at EAS of large Nμ/Ne ratio in the energy range of 1–10 PeV. Comparing the spectra for various thresholds and core distances with detailed Monte Carlo simulations the validity of EAS simulations is discussed. 相似文献
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A large sample of summertime data from the McGill Radar Weather Observatory was analyzed to determine the variation with altitude
of the horizontal extent of individual rainshowers. For echoes defined by a reflectivity factor of 39 dBz (equivalent to a
rainfall rate of about 10 mm/h) it was found that the mean area of the total population of echoes decreases linearly with
altitude from approximately 20 km2 at 2 km to 11 km2 at 8 km. Subsets of the total population were investigated, consisting of only the echoes penetrating the altitudes of 6,
7, and 8 km. On the average these relatively tall echoes are much greater in horizontal extent than the total population.
Whereas the sizes of the total population of echoes at any altitude are distributed approximately exponentially in terms of
the square root of area, the sizes of the “survivors” that extend to high altitudes may be described by the gamma distribution
with a mean value decreasing approximately linearly with height above 3 km and a dispersion of 0.55. Some characteristics
are also reported for echoes defined by reflectivities of 31 dBz and 47 dBz. Estimates are given of the fraction of the total
area in a horizontal plane that contains echoes in each of these categories. 相似文献
6.
John Shaw Mimi J. Hill Steven J. Openshaw 《Earth and Planetary Science Letters》2001,190(3-4):103-109
The new microwave palaeointensity technique has been used to investigate samples from the Martian meteorite Nakhla. This technique is a promising new way to obtain absolute palaeointensity information regarding the ancient Martian magnetic field as recorded by the Martian meteorites. Assuming that a part of the magnetic remanence is of thermal origin and originating on Mars the two samples studied yield estimates of 4 μT for the Martian magnetic field at 1.35 Ga. 相似文献
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The
Monte Carlo program is used to predict the distributions of the muons which originate from primary cosmic gamma rays and reach sea level. The main result is the angular distribution of muons produced by vertical gamma rays which is necessary to predict the inherent angular resolution of any instrument utilizing muons to infer properties of gamma ray primaries. Furthermore, various physical effects are discussed which affect these distributions in differing proportions. 相似文献
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Shinsuke Abe Noboru Ebizuka Hideyuki Murayama Katsuhito Ohtsuka Satoru Sugimoto Masa-yuki Yamamoto Hajime Yano Jun-ichi Watanabe Jiří Borovička 《Earth, Moon, and Planets》2004,95(1-4):265-277
Spectra of persistent meteor trains were observed at wavelength between 300 and 930 nm. Two obtained train spectra during
the 1998 and 2001 Leonid meteor showers are reported here. During the 1998 Leonids, one train was detected by a photographic
camera with a spectrograph covering 370–640 nm region. On the other hand, during the 2001 Leonids, video observations were
carried out using image intensified cameras in ultraviolet (UV), visible and near infrared (near-IR) wavelengths. Temperatures
in persistent trains have been measured by atmospheric O2 A(0,1) band at the wavelength near 864.5 nm. From a video spectrum obtained just 7 s after parent fireball’s flare, a rotational
temperature of 250 K at altitude of 88.0±0.5 km was estimated. We can say that the cooling time scale of train strongly depends
on the initial mass of its fireball at least for Leonids. Based on cooling constant calculated from our results, we estimated
a temperature of ∼
∼130 K as a final exothermic temperature at early stage of persistent trains. 相似文献
10.
M. D. Campbell-Brown 《Earth, Moon, and Planets》2004,95(1-4):297-301
The Arietid meteor shower is one of the strongest of the year. The origin of this daytime shower is unknown; the orbit is
therefore of great interest, since an accurate orbit distribution is needed to integrate the shower backward in time to test
associations with comets or asteroids. The orbital parameters of the Arietid shower as a function of time, with errors, have
been generated using 415 radar orbits gathered at the CMOR facility in Tavistock, Canada. 相似文献