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41.
Marcela Cichowolski Beatriz G. Waisfeld Norberto E. Vaccari Larisa Marengo 《Geological Journal》2015,50(6):764-782
A single confidently dated species of cephalopod is so far known in the Tremadocian of the southern Central Andean Basin (NW Argentina and southern Bolivia). This species belongs to the Eothinoceratidae and has a strong affinity mainly with Avalonia. During the Floian, a notable increase in diversity took place, with the appearance of a variety of families represented by several genera, in particular, within the Family Eothinoceratidae. In addition to the previously described species from southern Bolivia, we evaluate the other records of that family from the Central Andean Basin, and propose the following new taxa: Saloceras sikus sp. nov., Saloceras quena sp. nov., Mutveiceras gen. nov., and Mutveiceras cienagaensis sp. nov. We also describe Margaritoceras diploide, Margaritoceras sp., and Mutveiceras sp. From a palaeogeographic perspective, the cephalopod fauna shows affinities mainly with those of England, Wales, and the Montagne Noire (cold water Gondwana and peri‐Gondwana). As with other cephalopod faunas of mid to high palaeolatitudes, eothinoceratids occur along with other cephalopods forming assemblages of low morphological diversity. We interpret the forms described here as demersal with a subvertical poise, but capable of making rapid buoyancy changes, living in a wide spectrum of shallow offshore to shoreface settings. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
42.
Luca Caricchi Anne Pommier Mattia Pistone Jonathan Castro Alain Burgisser Diego Perugini 《Bulletin of Volcanology》2011,73(9):1245-1257
Experiments have been performed to determine the effect of deformation on degassing of bubble-bearing melts. Cylindrical specimens
of phonolitic composition, initial water content of 1.5 wt.% and 2 vol.% bubbles, have been deformed in simple-shear (torsional
configuration) in an internally heated Paterson-type pressure vessel at temperatures of 798–848 K, 100–180 MPa confining pressure
and different final strains. Micro-structural analyses of the samples before and after deformation have been performed in
two and three dimensions using optical microscopy, a nanotomography machine and synchrotron tomography. The water content
of the glasses before and after deformation has been measured using Fourier Transform Infrared Spectroscopy (FTIR). In samples
strained up to a total of γ ∼ 2 the bubbles record accurately the total strain, whereas at higher strains (γ ∼ 10) the bubbles
become very flattened and elongate in the direction of shear. The residual water content of the glasses remains constant up
to a strain of γ ∼ 2 and then decreases to about 0.2 wt.% at γ ∼ 10. Results show that strain enhances bubble coalescence
and degassing even at low bubble volume-fractions. Noticeably, deformation produced a strongly water under-saturated melt.
This suggests that degassing may occur at great depths in the volcanic conduit and may force the magma to become super-cooled
early during ascent to the Earth’s surface potentially contributing to the genesis of obsidian. 相似文献
43.
R. J. Ivison T. R. Greve J. S. Dunlop J. A. Peacock E. Egami Ian Smail E. Ibar E. van Kampen I. Aretxaga T. Babbedge A. D. Biggs A. W. Blain S. C. Chapman D. L. Clements K. Coppin D. Farrah M. Halpern D. H. Hughes M. J. Jarvis T. Jenness J. R. Jones A. M. J. Mortier S. Oliver C. Papovich P. G. Pérez-González A. Pope S. Rawlings G. H. Rieke M. Rowan-Robinson R. S. Savage D. Scott M. Seigar S. Serjeant C. Simpson J. A. Stevens M. Vaccari J. Wagg C. J. Willott 《Monthly notices of the Royal Astronomical Society》2007,380(1):199-228
44.
Michael Rowan-Robinson Tom Babbedge Seb Oliver Markos Trichas Stefano Berta Carol Lonsdale Gene Smith David Shupe Jason Surace Stephane Arnouts Olivier Ilbert Olivier Le Févre Alejandro Afonso-Luis Ismael Perez-Fournon Evanthia Hatziminaoglou Mari Polletta Duncan Farrah Mattia Vaccari 《Monthly notices of the Royal Astronomical Society》2008,386(2):697-714
45.
A new dyke intrusion style for the Mount Etna May 2008 eruption modelled through continuous tilt and GPS data 总被引:2,自引:0,他引:2
M. Aloisi A. Bonaccorso F. Cannavò S. Gambino M. Mattia G. Puglisi E. Boschi 《地学学报》2009,21(4):316-321
After a recharge phase that began in 2007, on 13 May 2008, a new eruption started on Mt. Etna volcano. The final intrusion was very fast, accompanied by a violent seismic swarm and marked by ground deformation recorded at permanent tilt and GPS stations. The violence of the eruptive event generated concern that the eruptive fissures might propagate downslope towards populated areas. The ground deformation modelling explains both the mechanism of the intrusion as well as the attempt of the dyke to propagate in the shallower part of the northern sector of the volcano. We show that the 2008 intrusion was characterized by a mechanism, which is new and different to the ones modelled in previous eruptions, following the path of the central conduit in the first part of the intrusion (below 1.6 km) and then breaking off towards the east in the last shallow part. 相似文献
46.
Mario Mattia Marco Aloisi Giuseppe Di Grazia Salvatore Gambino Mimmo Palano Valentina Bruno 《Journal of Volcanology and Geothermal Research》2008
In this work, we report the results of an integrated approach using both seismological and geodetic data provided by the INGV-CT (Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania) Stromboli volcano monitoring systems, in order to improve the knowledge of its plumbing system. In particular, we investigated the relationships between the June 1999 seismic swarm, occurring in the area of Stromboli, and the possible activation of the NE–SW oriented volcano-tectonic structure. We analyzed this seismic swarm proposing new locations and a morphological analysis of the waveforms. This approach allowed us to demonstrate that there are relationships between the tectonic activity near Stromboli and the rising of magma. This evidence supports the hypothesis that during the 1999 swarm an intrusive process started from a crustal level where earthquakes were located (about 10–15 km b.s.l.). 相似文献
47.
Deterministic Seismic Zoning of Eastern Cuba 总被引:1,自引:0,他引:1
—A deterministic seismic zoning of Cuba is performed by modelling, with modal summation, the complete P-SV and SH waves fields generated by point-source earthquakes buried in flat-layered anelastic media. The results of the computation, performed for periods greater than 1 second, are presented in two sets of maps of maximum displacement (d max), maximum velocity (v max) and design ground acceleration (DGA), obtained by using two different criteria in the definition of the input magnitude: (1) values reported in the earthquake catalogue (M obs) and (2) values determined from seismotectonic considerations (M max). A comparison with the results of a previous probabilistic seismic zoning is made to test the possibility of making intensity — ground motion conversion with the aid of log-linear regressions. 相似文献
48.
I. Waddington S. J. Oliver T. S. R. Babbedge F. Fang D. Farrah A. Franceschini E. A. Gonzalez-Solares C. J. Lonsdale G. Rodighiero M. Rowan-Robinson D. L. Shupe J. A. Surace M. Vaccari C. K. Xu 《Monthly notices of the Royal Astronomical Society》2007,381(4):1437-1449
We investigate the clustering of galaxies selected in the 3.6 μm band of the Spitzer Wide-area Infrared Extragalactic (SWIRE) legacy survey. The angular two-point correlation function is calculated for 11 samples with flux limits of S 3.6 ≥ 4–400 μJy, over an 8 deg2 field. The angular clustering strength is measured at >5σ significance at all flux limits, with amplitudes of A = (0.49–29) × 10−3 at 1°, for a power-law model, A θ−0.8 . We estimate the redshift distributions of the samples using phenomological models, simulations and photometric redshifts, and so derive the spatial correlation lengths. We compare our results with the Galaxies In Cosmological Simulations (GalICS) models of galaxy evolution and with parametrized models of clustering evolution. The GalICS simulations are consistent with our angular correlation functions, but fail to match the spatial clustering inferred from the phenomological models or the photometric redshifts. We find that the uncertainties in the redshift distributions of our samples dominate the statistical errors in our estimates of the spatial clustering. At low redshifts (median z ≤ 0.5), the comoving correlation length is approximately constant, r 0 = 6.1 ± 0.5 h −1 Mpc, and then decreases with increasing redshift to a value of 2.9 ± 0.3 h −1 Mpc for the faintest sample, for which the median redshift is z ∼ 1. We suggest that this trend can be attributed to a decrease in the average galaxy and halo mass in the fainter flux-limited samples, corresponding to changes in the relative numbers of early- and late-type galaxies. However, we cannot rule out strong evolution of the correlation length over 0.5 < z < 1 . 相似文献
49.
Deterministic Earthquake Scenarios for the City of Sofia 总被引:3,自引:0,他引:3
S. Slavov I. Paskaleva M. Kouteva F. Vaccari G. F. Panza 《Pure and Applied Geophysics》2004,161(5-6):1221-1237
— The city of Sofia is exposed to a high seismic risk. Macroseismic intensities in the range of VIII – X (MSK) can be expected in the city. The earthquakes that can influence the hazard in Sofia originate either beneath the city or are caused by seismic sources located within a radius of 40 km. The city of Sofia is also prone to the remote Vrancea seismic zone in Romania, and particularly vulnerable are the long-period elements of the built environment. The high seismic risk and the lack of instrumental recordings of the regional seismicity make the use of appropriate credible earthquake scenarios and ground-motion modelling approaches for defining the seismic input for the city of Sofia necessary. Complete synthetic seismic signals, due to several earthquake scenarios, were computed along chosen geological profiles crossing the city, applying a hybrid technique, which combines the modal summation technique and finite differences. The modelling takes into account simultaneously the geotechnical properties of the site, the position and geometry of the seismic source and the mechanical properties of the propagation medium. Acceleration, velocity and displacement time histories and related quantities of earthquake engineering interest (e.g., response spectra, ground-motion amplification along the profiles) have been supplied. The approach applied in this study allows us to obtain the definition of the seismic input at low cost, exploiting large quantities of existing data (e.g. geotechnical, geological, seismological). It may be efficiently used to estimate the ground motion for the purposes of microzonation, urban planning, retrofitting or insurance of the built environment, etc. 相似文献
50.