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1.
We performed polarization observations of giant radio pulses from the millisecond pulsar B1937+21. The observations were carried out in July 2002 with the 64-m Kalyazin radio telescope at a frequency of 600 MHz in two polarization channels with left-and right-hand circular polarizations (RCP and LCP). We used the S2 data acquisition system with a time resolution of 125 ns. The duration of an observing session was 20 min. We detected twelve giant radio pulses with peak flux densities higher than 1000 Jy; five and seven of these pulses appeared in the RCP and LCP channels, respectively. We found no event that exceeded the established detection threshold simultaneously in the two polarization channels. Thus, we may conclude that the detected giant pulses have a high degree of circular polarization, with the frequency of occurrence of RCP and LCP pulses being the same. 相似文献
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S. I. Mayr H. Burkhardt Yu. Popov A. Wittmann 《International Journal of Earth Sciences》2008,97(2):385-399
Internal surface, formation factor, Nuclear Magnetic Resonance (NMR)-T2 relaxation times and pore radius distributions were
measured on representative core samples for the estimation of hydraulic permeability. Permeability is estimated using various
versions of the classic Kozeny–Carman-equation (K–C) and a further development of K–C, the fractal PaRiS-model, taking into
account the internal surface. In addition to grain and pore size distribution, directly connected to permeability, internal
surface reflects the internal structure (“micro morphology”). Lithologies could be grouped with respect to differences in
internal surface. Most melt rich impact breccia lithologies exhibit large internal surfaces, while Tertiary post-impact sediments
and Cretaceous lithologies in displaced megablocks display smaller internal surfaces. Investigations with scanning electron
microscopy confirm the correlation between internal surface and micro morphology. In addition to different versions of K–C,
estimations by means of NMR, pore radius distributions and some gas permeability measurements serve for cross-checking and
calibration. In general, the different estimations from the independent methods and the measurements are in satisfactory accordance.
For Tertiary limestones and Suevites bulk with very high porosities (up to 35%) permeabilites between 10−14 and 10−16 m2 are found, whereas in lower Suevite, Cretaceous anhydrites and dolomites, bulk permeabilites are between 10−15 and 10−23 m2. 相似文献
4.
We have investigated how the latitude dependence of the solar wind velocity (SWV) influenced the cosmic-ray (CR) modulation and distribution in the heliosphere. The dependence proposed by Fry and Akasofu (1987) is used:v
SW=v
O+v
1(1-cos
n
m
, where the SWV,v
SW is a function of the heliomagnetic latitude
m
andv
0 andv
1 are constants. An estimation of the diffusion and drift terms in the transport equation is made, which shows that towards the poles the effects of the drift transfer decrease, while the diffusion terms in the equation increase due to the change of the interplanetary magnetic field (IMF) geometry. The numerical solutions of the two-dimensional (2-D) transport equation show that when the SWV changes with latitude: (1) The CR intensities away from the neutral sheet are larger for both IMF polarity periods in comparison with the case when the SWV does not change with the latitude. (2) The latitude gradients are negative during negative magnetic polarity periods. (3) The Voyager 1 and Voyager 2 long-time observations showing greater galactic CR intensities nearer the Sun at greater distances, could be explained by the proposed model. 相似文献
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Results of studying Fe(III) hydrolysis and sorption of heavy metal compounds by organic matter of bottom sediments are discussed. The rate of Fe(III) hydrolysis is found to be largely determined by the concentration of dissolved organic substances. Values of kinetic parameters are obtained for heavy metal compounds sorption under static and dynamic conditions. Calculating the solubility of Fe, Cu, Cd, Zn, and Pb sulfides allowed the assessment of the amount of metals lost by bottom sediments due to the formation of metal complexes with dissolved organic substances contained in natural waters. 相似文献
7.
Yuri D Zakharov Alexander M Popov Galina I Buryi 《中国地质大学学报(英文版)》2005,16(3):219-230
INTRODUCTION LateOlenekianandAnisianmarinedepositsin SouthPrimoryewerefirststudiedbyD.L.Ivanov,thechiefofageologicalteammakingreconnaissance workfortheconstructionofthetrans Siberianrail road.HecollectedEarlyandMiddleTriassicam monoidsonRussianIsland.Arep… 相似文献
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The structure of the interstellar plasma in the direction of the pulsar in the Crab Nebula is studied using several sets of space-VLBI observations obtained with networks of ground telescopes and the RadioAstron space antenna at 18 and 92 cm. Six observing sessions spanning two years are analyzed. Giant pulses are used to probe the cosmic plasma, making it possible to measure the scattering parameters without averaging. More than 4000 giant pulses were detected. The interferometer responses (visibility functions) on ground and ground–space baselines are analyzed. On the ground baselines, the visibility function as a function of delay is dominated by a narrow feature at zero delay with a width of δτ ~ 1/B, where B is the receiver bandwidth. This is typical for compact continuum sources. On the ground–space baselines, the visibility function contains a set of features superposed on each other and distributed within a certain interval of delays, which we identify with the scattering time for the interfering rays τ. The amplitude of the visibility function on ground baselines falls with increasing baseline; the scattering disk is partially resolved at 18 cmand fully resolved at 92 cm. Estimates of the scattering angle ? give 0.5–1.3mas at 18 cm and 14.0 mas at 92 cm. The measured values of ? and τ are compared to estimate the distance from the source to the effective scattering screen, which is found at various epochs to be located at distances from 0.33 to 0.96 of the distance from the observer to the pulsar, about 2 kpc. The screen is close to the Crab Nebula at epochs of strong scattering, confirming that scattering on inhomogeneities in the plasma in the vicinity of the nebula itself dominates at these epochs. 相似文献
10.
N. A. Nekrylov D. V. Popov P. Yu. Plechov V. D. Shcherbakov L. V. Danyushevsky O. V. Dirksen 《Petrology》2018,26(4):329-350
Late Quaternary volcanoes of Sredinny Range (Kamchatka) attract geoscientists’ attention by their unusual geochemical features and geodynamic setting. They produced volcanic rocks that are enriched relative to N-MORB in most of incompatible trace elements (except HREE), including strong enrichment in large-ion lithophile elements, and show a negative Nb–Ta anomaly, which is typical for rocks formed in supra-subduction settings. However, modern subduction of the Pacific Plate does not reach the most part of Sredinny Range, as inferred by mapping of Wadati–Benioff zone or seismic tomography. We constrain the source of parental magmas for Sredinny Range volcanic rocks by combining major and trace element geochemical data for olivine and naturally quenched olivine-hosed melt inclusions for Holocene tephra layers of the Kekuknaisky field. Composition of the most magnesian olivine (Ni > 2000 ppm, Fe/Mn ≈ 75 at Mg# ~ 84–85 mol %) and geochemical characteristics of the most primitive melts (FC3MS = 0.61 ± 0.04 (2s)) are consistent with their derivation from a pyroxenite source, while elevated LREE/HREE ratios in lavas indicate that it contained garnet. This garnet-bearing pyroxenite likely originated from the lower crust or lithospheric mantle. Its melting could have occurred due to delamination and sinking into the hotter mantle. 相似文献