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51.
Piero Bareschino Teresita Gravina Lucio Lirer Antonio Marzocchella Paola Petrosino Piero Salatino 《Journal of Volcanology and Geothermal Research》2007
Fluidization of pyroclastic solids has long been indicated as one key to explain the enhanced mobility of dense pyroclastic gravity currents and their associated hazard. However there is a lack of characterization of the actual pattern and extent of fluidization establishing in real pyroclastic flows and some authors still raise arguments about the relevance of fluidization to the mobility of dense pyroclastic gravity currents. The present paper addresses the fluidization of pyroclastic granular solids with a specific focus on the analysis of factors that may promote homogeneous fluidization and retard solids de-aeration and consolidation. These factors include fines content, particle polydispersity and the establishment of shear flow. 相似文献
52.
Keller P. Nicolini Katia C. Lombardi Wido H. Schreiner Irineu Mazzaro Fernando Wypych Antonio S. Mangrich 《Mineralogy and Petrology》2009,97(1-2):139-144
We report on a paramagnetic anisotropy study of three layered phyllosilicates. The mineral samples were characterized through X-ray powder diffraction (XRPD), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Based on EPR measurements of samples oriented parallel or perpendicular to the magnetic field lines, we show how the substitutional iron is transformed from Fe(II) (biotite) into Fe(III) (muscovite and kaolinite) species and from axial Fe(III) coordination sites (muscovite) to rhombic (kaolinite) sites in response to weathering. 相似文献
53.
Summary Chaco jet events (CJEs) are a subset of South American low-level jet events to the east of the Andes, characterized by enhanced
poleward penetration and by a strong impact on precipitation over southeastern South America. The present study uses the Eta
model short range weather forecasts produced operationally in the Brazilian Center for Weather Forecasts and Climate Studies
(Centro de Previs?o de Tempo e Estudos Climáticos, CPTEC) to characterize the CJEs and the related precipitation during the
1997–1998 warm season.
An enhanced diurnal cycle in precipitation with respect to that found during the warm season mean can be recognized during
CJEs in Eta/CPTEC model output, with preference for a nocturnal maximum over southern Brazil, Uruguay, and the central part
of northern Argentina, and a daytime maximum near high topography (northwestern Argentina, the Brazilian Planalto). The analysis
of thermodynamic and dynamic forcing appearing during CJEs, helps to explain the modeled precipitation cycle: the nocturnal
maximum is mostly explained by enhanced low-level convergence at night, while the diurnal one is mainly a response to radiative
warming. Boundary-layer convergence, and convective instability, present within the CJEs environment, work together to provide
both dynamic forcing and potential for convection. The simulated precipitation cycle is complemented with surface observations
of “current weather” that corroborate the main oscillations found in simulated precipitation. 相似文献
54.
Lucio Mayer Fabio Governato Monica Colpi Ben Moore Thomas R. Quinn Carlton M. Baugh 《Astrophysics and Space Science》2001,276(2-4):375-382
We study the evolution of galaxy satellites with high resolutionN-body simulations. Satellites are modelled as replicas of typical low and high surface brightness galaxies (LSBs and HSBs).
Encounters on high eccentricity orbits (as typical in hierarchical models of galaxy formation) strip LSBs of most of their
stars and tend to decrease their surface brightness. In contrast, bar instability in HSBs leads to substantial loss of angular
momentum of the stellar component and to an increase in central surface brightness. In both cases the remnant resembles a
spheroidal galaxy with an exponential surface brightness profile. A simple modelling of colour evolution and interaction-driven
star formation gives M/L ratios for the remnants that are roughly consistent with observations. These results suggest an evolutionary scenario for
the dwarf galaxies in our Local Group, faint dSphs being the descendants of LSBs and brighter dSphs/dEs being the final state
of HSB satellites.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Luca Pietranera Stefan A. Buehler Paolo G. Calisse Claudia Emde Darren Hayton Viju Oommen John Bruno Maffei Lucio Piccirillo Giampaolo Pisano Giorgio Savini T. R. Sreerekha 《Monthly notices of the Royal Astronomical Society》2007,376(2):645-650
Ice crystal clouds in the upper troposphere can generate polarization signals at the μK level. This signal can seriously affect very sensitive ground-based searches for E and B modes of cosmic microwave background polarization. In this paper, we estimate this effect within the Cℓ OVER experiment observing bands (97, 150 and 220 GHz) for the selected observing site (Llano de Chajnantor, Atacama desert, Chile). The results show that the polarization signal from the clouds can be of the order of or even bigger than the cosmic microwave background expected polarization. Climatological data suggest that this signal is fairly constant over the whole year in Antarctica. On the other hand, the stronger seasonal variability in Atacama allows for a 50 per cent of clean observations during the dry season. 相似文献
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P. Persi M. Ferrari-Toniolo A. R. Marenzi M. Busso L. Corcione G. Nicolini K. Shivanandan 《Experimental Astronomy》1994,3(1-4):171-172
We present the main characteristics of a new mid-IR camera, TIRCAM, operating at the 1.5 m Italian Infrared Telescope. 相似文献