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101.
This paper presents a geological–structural study of some Neogene hinterland basins of the Northern Apennines, located on the Tyrrhenian side of the chain. These basins developed on the already delineated thrust-fold belt from middle–late Tortonian times. Their evolution has been commonly referred to an extensional tectonic regime, related to the opening of the Tyrrhenian Sea. New data have allowed us to hypothesize a different tectonic evolution for the chain, where compressive tectonics plays a major role both in the external and in the hinterland area. In this frame, the hinterland area located west of a major outcropping crustal thrust (Mid-Tuscany Metamorphic Ridge) has been the target of a geological–structural investigation. The field mapping and structural analysis has been focused on the syntectonic sediments of the Radicondoli–Volterra basin as well as on adjoining minor basins. These basins commonly display a synclinal structure and are generally located in between basement culminations, probably corresponding to thrust anticlines. Sediments of the hinterland basins have been affected by compressive deformation and regional unconformities separate stratigraphic units due to the activity of basement thrusts. In the study area, normal faulting either accommodates the thrusting processes or post-dates compressive deformation. A chronology of faulting and a six-stage evolution of this area are presented, providing further insights for the Neogene tectonic evolution of the Northern Apennines. Copyright © 1998 John Wiley & Sons, Ltd. 相似文献
102.
Giovanna Giorgetti Peter Tropper Eric J. Essene Donald R. Peacor 《Contributions to Mineralogy and Petrology》2000,138(4):326-336
Coexisting muscovite and paragonite have been observed in an eclogite from the Sesia–Lanzo Zone (Western Alps, Italy). The
P-T conditions of this eclogite reached 570–650 °C and 19–21 kbar and the rocks show several stages of mineral growth during
their retrograde path, ranging from the subsequent lower-P eclogite facies to the blueschist facies and then the greenschist facies. Muscovite and paragonite are very common in these
rocks and show two texturally different occurrences indicating equilibrium and non-equilibrium states between them. In one
mode of occurrence they coexist in equilibrium in the lower-P eclogite facies. In the same rock muscovite ± albite also replaced paragonite during a greenschist-facies overprint, as evidenced
by unique across – (001) layer boundaries. The chemical compositions of the lower-P eclogite-facies micas plot astride the muscovite – paragonite solvus, whereas the compositions of the greenschist-facies
micas lie outside the solvus and indicate disequilibrium. The TEM observations of the textural relations of the greenschist-facies
micas imply structural coherency between paragonite and muscovite along the layers, but there is a sharp discontinuity in
the composition of the octahedral and tetrahedral sheets across the phase boundary. We propose that muscovite formed through
a dissolution and recrystallization process, since no gradual variations toward the muscovite – paragonite interfaces occur
and no intermediate, homogeneous Na-K phase has been observed. Because a solid-state diffusion mechanism is highly unlikely
at these low temperatures (300–500 °C), especially with respect to octahedral and tetrahedral sites, it is assumed that H2O plays an important role in this process. The across-layer boundaries are inferred to be characteristic of such non-equilibrium
replacement processes. The characterization of these intergrowths is crucial to avoiding erroneous assumptions regarding composition
and therefore about the state of equilibrium between both micas, which in turn may lead to misinterpretations of thermometric
results.
Received: 3 February 1999 / Accepted: 19 October 1999 相似文献
103.
104.
Alessandra Borghi Daniela Carrion Giovanna Sona 《Geophysical Journal International》2007,171(2):539-549
An up to date determination of a high-resolution geoid requires the use of best available databases concerning digital terrain model (DTM), bathymetry, global geopotential model and gravity field. The occasion to revisit methods to validate and merge different data sets has been created by a new project for the determination of a new European Geoid.
Since the computation of the latest European geoid and quasi-geoid model (EGG97), significant new or improved data sets have become available, such as new global geopotential models from CHAMP and GRACE missions, new national and global DTMs and new or upgraded gravity data sets.
In the context of the new European Gravity and Geoid Project (EGGP), within the IAG Commission 2, some data validation tests have been performed in the Italian zone.
In the area 19°× 17° wide, covering Italy, three kinds of tests have been performed: comparison among different DTMs in order to choose the best one to be used; comparisons in terms of geoid computation in some coastal areas, to evaluate bathymetry effects, and the validation of the EIGEN-CG01C and EIGEN-CG03C new global models up to degree and order 360.
These preliminary tests lead to the choice of SRTM DTM (integrated in no-data holes), with an added bathymetry derived by the Italian 1:25 000 official cartography near the coasts and the NOAA bathymetry in high seas. The validation of the new global models and the comparison with EGM96 model show that, in terms of geoid computation, the EGM96 yields better results. Moreover, the validation of new available land gravity data and the cross-validation of two sets of gravity data on sea have been completed. 相似文献
Since the computation of the latest European geoid and quasi-geoid model (EGG97), significant new or improved data sets have become available, such as new global geopotential models from CHAMP and GRACE missions, new national and global DTMs and new or upgraded gravity data sets.
In the context of the new European Gravity and Geoid Project (EGGP), within the IAG Commission 2, some data validation tests have been performed in the Italian zone.
In the area 19°× 17° wide, covering Italy, three kinds of tests have been performed: comparison among different DTMs in order to choose the best one to be used; comparisons in terms of geoid computation in some coastal areas, to evaluate bathymetry effects, and the validation of the EIGEN-CG01C and EIGEN-CG03C new global models up to degree and order 360.
These preliminary tests lead to the choice of SRTM DTM (integrated in no-data holes), with an added bathymetry derived by the Italian 1:25 000 official cartography near the coasts and the NOAA bathymetry in high seas. The validation of the new global models and the comparison with EGM96 model show that, in terms of geoid computation, the EGM96 yields better results. Moreover, the validation of new available land gravity data and the cross-validation of two sets of gravity data on sea have been completed. 相似文献
105.
Zeolites from the most important volcanoclastic deposits of Italy include: (1) phillipsite and heulandite from the cinerite
of the central northern Apennines; (2) chabazite and phillipsite from the phonolitic tephritic ignimbrite with black pumices;
(3) phillipsite from the “tufo lionato” of Vulcano Laziale; (4) chabazite and phillipsite from the Campanian ignimbrite; (5)
phillipsite from the Neapolitan yellow tuff; and (6) chabazite and phillipsite from the pyroclastics of Monte Vulture. Compared
with sedimentary phillipsites and chabazites described in the literature, the chabazites and phillipsites studied here have
lower Si/Al ratios and higher K contents. These chemical peculiarities are correlated with both the K-rich vesuvitic-leucititic,
latitic-phonolitic, and potassic alkali-trachytic chemistry of the ash from which they were derived and, very likely, with
the character of the hydrologically open system environment in which they formed. The zeolite of the heulandite-clinoptilolite
group from the cinerite of the central northern Apennines is classified as a true heulandite on the basis of its chemical
composition and thermal behavior. 相似文献
106.
The recharge processes have been evaluated for two karst massifs of southern Italy, the Mt Terminio and Mt Cervialto, characterized by wide endorheic areas. The annual mean recharge has been estimated by Geographic Information System (GIS) tools, from regression of annual mean values of different ground‐elevated rain gauges and thermometers. The recharge has been distinguished for endorheic areas and the other areas of spring catchment, and the ratio between the output spring and input rainfall has been also estimated (recharge coefficient). The annual recharge has been used to calibrate a daily scale model, which allows to estimate the amount of effective rainfall, which is retained as soil moisture; the amount reaching the water table (recharge s.s.); and the amount of rainfall, which develops the runoff and leaves the catchment. All these amounts vary through the hydrological year, in function of soil moisture deficit and daily rainfall intensity. The model allows estimating the recharge conditions through the hydrological year, and it is a useful tool for water management. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
107.
108.
Stress drop estimates of moderate-magnitude earthquakes in the Umbria–Marche region, in the northern Apennines, exhibit a large scatter. For the two M w 5.7 and 6.0 main shocks of 26 September 1997 near Colfiorito, several papers resulted in stress drop estimates of 20 MPa, but values as low as 2–3 MPa were proposed as well. Also for the largest aftershocks (M w > 4), estimates spread from < 1 MPa up to values ten times larger. We have critically revisited methods and data used in the literature. We have specifically faced the trade-off between source and propagation effects, as we believe that it is responsible for a part of the large scatter. To keep this trade-off under control, we have applied a methodology that combines the best fit of both source spectra after Empirical Green’s Function (EGF) deconvolution and observed ground motion spectra, finding that the results of the two different data sets converge independently at the same solution. We have used ground motions observed in the Colfiorito basin, where an accelerograph and a co-located seismological broad-band station recorded three clusters of earthquakes in a broad magnitude interval (1.7 ≤ M w ≤ 6.0). We have found that the mainshock–aftershock sequences result in stress drops of 2–5 MPa at M w ≥ 5.6, with an average tendency to decrease at smaller magnitudes where stress drop variability increases. These findings confirm the source scaling recently assessed through Empirical Green’s Function deconvolution for another well-monitored seismic sequence of normal-faulting earthquakes, which struck the city of L’Aquila in the central Apennines in April 2009. The similar scaling law of the two areas suggests common mechanisms of stress release for the shallow normal faults in the Apennines. The propensity of smaller earthquakes to increase in variability, with a tendency toward smaller stress drops, may reflect an effect of fault strength heterogeneities for smaller size ruptures. 相似文献
109.
Building damage scenarios based on exploitation of Housner intensity derived from finite faults ground motion simulations 总被引:2,自引:2,他引:0
Leonardo Chiauzzi Angelo Masi Marco Mucciarelli Marco Vona Francesca Pacor Giovanna Cultrera Frantisek Gallovič Antonio Emolo 《Bulletin of Earthquake Engineering》2012,10(2):517-545
In this paper earthquake damage scenarios for residential buildings (about 4200 units) in Potenza (Southern Italy) have been
estimated adopting a novel probabilistic approach that involves complex source models, site effects, building vulnerability
assessment and damage estimation through Damage Probability Matrices. Several causative faults of single seismic events, with
magnitude up to 7, are known to be close to the town. A seismic hazard approach based on finite faults ground motion simulation
techniques has been used to identify the sources producing the maximum expected ground motion at Potenza and to generate a
set of ground motion time histories to be adopted for building damage scenarios. Additionally, site effects, evaluated in
a previous work through amplification factors of Housner intensity, have been combined with the bedrock values provided by
hazard assessment. Furthermore, a new relationship between Housner and EMS-98 macroseismic intensity has been developed. This
relationship has been used to convert the probability mass functions of Housner intensity obtained from synthetic seismograms
amplified by the site effects coefficients into probability mass function of EMS-98 intensity. Finally, the Damage Probability
Matrices have been applied to estimate the damage levels of the residential buildings located in the urban area of Potenza.
The proposed methodology returns the full probabilistic distribution of expected damage, thus avoiding average damage index
or uncertainties expressed in term of dispersion indexes. 相似文献
110.
Cristina Ingarao Giovanna Lanciani Carmen Verri Tommaso Pagliani 《Marine pollution bulletin》2009,58(4):596-600
Prorocentrum lima (Ehrenberg) Dodge has been found for the first time during the summer of 2007 inside Ortona harbor and along the coast of the Abruzzo region, a slightly eutrophic area influenced by runoff from a nearby river. The investigations were conducted in two harbors and at six coastal sampling stations. Samplings were conducted using a phytoplankton net and with a pump. Average P. lima cellular concentrations were 3.2 × 104 cells L−1. Other well-known toxic and potentially toxic phytoplankton species have been considered. The number of toxic cells from net samples were higher than the numbers of toxic cell samples collected without the net. Occurrences of P. lima with abiotic factors revealed that temperature was positively correlated with P. lima abundance (p = 0.01), while salinity was highly negatively correlated with P. lima presence (p = 0.001). The total phytoplankton community was studied. 相似文献