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61.
Davide Lenaz Vadim S. Kamenetsky Anthony J. Crawford Francesco Princivalle 《Contributions to Mineralogy and Petrology》2000,139(6):748-758
Detrital spinel is a widespread heavy mineral in sandstones from the Maastrichtian–Middle Eocene sedimentary basins in the
SE Alps. Chemistry of detrital spinels from the Claut/Clauzetto and Julian Basins (N Italy and NW Slovenia) is used to constrain
petrological and geochemical affinities and tectonic provenance of the source rocks. In addition, we have analysed melt inclusion
compositions in the detrital volcanic spinels to better constrain the nature of their parental magmas. This is the first study
of melt inclusions in detrital spinels. Two principal compositional groups of detrital spinels are recognised based on their
TiO2 and Fe2+/Fe3+; one derived from peridotites, the other from basaltic volcanics. Peridotitic spinels are more abundant and have TiO2 < 0.2 wt% and high Cr/Cr + Al (40–90), characteristic of suprasubduction zone harzburgites. Significant chemical variations
among volcanic spinels (TiO2 up to 3 wt%, Al2O3 12–44 wt%) suggest multiple sources, with geochemically distinct characteristics, including MORB-type and backarc basin basalts,
subduction-related magmas and tholeiites produced during early continental rifting. Compositions of homogenised melt inclusions
in spinels with TiO2 > 0.2 better distinguish the differences between the compositions of their host spinels and help to further clarify the geodynamic
provenance of extrusive source rocks. Several compositional groups of melt inclusions have been recognised and represent diverse
magmatism of marginal basins, including MORB- and subduction-related geochemical types, as well as magmas characteristic of
early continental rifting. These results, combined with the data on regional ophiolitic complexes and tectonic reconstructions
favour the Internal Dinarides of Yugoslavia as a possible source area for the SE Alps sediments.
Received: 20 January 2000 / Accepted: 25 April 2000 相似文献
62.
Gabriele Ghisellini Davide Lazzati Annalisa Celotti Martin J. Rees 《Monthly notices of the Royal Astronomical Society》2000,316(4):L45-L49
Recently several studies have jointly analysed data from different cosmological probes with the motivation of estimating cosmological parameters. Here we generalize this procedure to allow freedom in the relative weights of various probes. This is done by including in the joint χ 2 function a set of 'hyper-parameters', which are dealt with using Bayesian considerations. The resulting algorithm, which assumes uniform priors on the log of the hyper-parameters, is very simple: instead of minimizing (where is per data set j ) we propose to minimize (where N j is the number of data points per data set j ). We illustrate the method by estimating the Hubble constant H 0 from different sets of recent cosmic microwave background (CMB) experiments (including Saskatoon, Python V, MSAM1, TOCO and Boomerang ). The approach can be generalized for combinations of cosmic probes, and for other priors on the hyper-parameters. 相似文献
63.
We present some algebraic and numerical simulations of the stable boundary layer. We also discuss the problem of the existence
of a critical Richardson number (Ri), beyond which the turbulence is suppressed. We compare the results of a second-order algebraic model with those of a third-order
numerical model and, to this purpose, numerical simulations of a wind-tunnel flow, which is characterized by various Richardson
numbers, were performed. As far as the second-order model is concerned, solutions, for the Richardson number greater than
any critical value, can be obtained by modifying the time scales of the second-order equation pressure correlation terms in
order to account for a buoyancy damping factor. We show that using a third-order model allows the same results (no critical
Richardson number) to be obtained without modifications to the time scales. It is suggested that the non-locality, accounted
for by the third-order moments, could allow the turbulence to persist also for Ri > 1. 相似文献
64.
Gerardo Herrera Davide Notti Juan Carlos Garc��a-Davalillo Oscar Mora Geraint Cooksley M��nica S��nchez Alain Arnaud Michele Crosetto 《Landslides》2011,8(2):195-206
This paper describes the use of the Stable Point Network technique, a Persistent Scatterer Interferometry SAR technique, for
the analysis of the Portalet landslide area (Central Pyrenees, Spain). For this purpose, different SAR datasets acquired by
ERS-1, ERS-2, ENVISAT and TerraSAR-X satellites have been analysed. The use of different SAR images acquired by satellite
radar sensors operating at different microwave lengths has allowed for a comparative assessment and illustration of the advantages
and disadvantages of these satellites for landslide detection and monitoring. In the introduction, differential interferometry
and the study area are briefly described. Then the specifics of the SPN processing and the results of the different datasets
are described and compared. In Analysis of the results: the Portalet landslide area, the Portalet landslide area is introduced
and the radar displacement measurements are analysed with available geo-information data. Additionally, X-band measurements
are compared with those gathered by a ground-based SAR for a previous project. Finally, the most relevant conclusions of this
work are discussed. 相似文献
65.
We characterize the seismic response of Lake Vostok, an Antarctic subglacial lake located at nearly 4 km depth below the ice sheet. This study is relevant for the determination of the location and morphology of subglacial lakes. The characterization requires the design of a methodology based on rock physics and numerical modelling of wave propagation. The methodology involves rock-physics models of the shallow layer (firn), the ice sheet and the lake sediments, numerical simulation of synthetic seismograms, ray tracing, τ–p transforms, and AVA analysis, based on the theoretical reflection coefficients. The modelled reflection seismograms show a set of straight events (refractions through the firn and top-ice layer) and the two reflection events associated with the top and bottom of the lake. Theoretical AVA analysis of these reflections indicates that, at near offsets, the PP-wave anomaly is negative for the ice/water interface and constant for the water/sediment interface. This behaviour is shown by AVA analysis of the synthetic data set. This study shows that subglacial lakes can be identified by using seismic methods. Moreover, the methodology provides a tool for designing suitable seismic surveys. 相似文献
66.
67.
68.
Notti Davide Wrzesniak Aleksandra Dematteis Niccolò Lollino Piernicola Fazio Nunzio Luciano Zucca Francesco Giordan Daniele 《Landslides》2021,18(7):2341-2365
Landslides - In November 2016, an extreme rainfall event affected the Ligurian Alps (NW Italy). Consequently, several landslides and debris flows occurred in the upper Tanarello stream basin. In... 相似文献
69.
DInSAR analysis of ALOS PALSAR images for the assessment of very slow landslides: the Tena Valley case study 总被引:2,自引:2,他引:0
Juan Carlos García-Davalillo Gerardo Herrera Davide Notti Tazio Strozzi Inmaculada Álvarez-Fernández 《Landslides》2014,11(2):225-246
In this work we analyse the performance of advanced land observing satellite (ALOS) phased array type L-band syntetic aperture radar (PALSAR) images for mapping and monitoring of very slow landslides using conventional differential interferometry in the Tena Valley (Central Pyrenees, Spain). These results are compared with those retrieved in previous works where multi-band advanced differential interferometric synthetic aperture radar (DInSAR) analysis was performed for the same area using PSI techniques. The study area is largely underlain by slates (ca. 80 %) where large deep-seated very slow earth flows are dominant. The results reveal that DInSAR analysis is able to measure displacements of landslides with a greater spatial coverage than PSI analysis, but for a lower amount of them (nine against 51). Overall, the combination of the DInSAR and multi-band PSI analysis permitted to map and monitor 68 % of the landslides in Tena Valley. From this amount, 63 landslides are considered as active. The main advantage of DInSAR with respect to PSI analysis is the capability to detect faster movements (up to 145 cm?year?1) derived from the 46 days interferograms. That is the case of Sextas and La Selva landslides where an acceleration of the moving mass was measured after intense rainfall periods producing major damages to linear infrastructures. The combination of measured displacement from ALOS interferograms, with the observed damages on the A-136 road, was useful to assess the potential damage that could cause these slow movements. In general, it is demonstrated that even though PSI analysis provides a better performance in terms of landslide mapping, L-band DInSAR analysis provides an added value for landslide hazard assessment through radar remote sensing. For this reason it is necessary to encourage the launch of new satellite missions similar to ALOS PALSAR that could operate with shorter revisiting time periods. 相似文献
70.
Davide?LenazEmail author Jacob?Adetunji Hugh?Rollinson 《Contributions to Mineralogy and Petrology》2014,167(1):958
We present the results of a comparative study in which we have measured Fe3+/ΣFe ratios in chromites from mantle chromitites in the Oman ophiolite using Mössbauer spectroscopy and single-crystal X-ray diffraction. We have compared these results with ratios calculated from mineral stoichiometry and find that mineral stoichiometry calculations do not accurately reflect the measured Fe3+/ΣFe ratios. We have identified three groups of samples. The majority preserve Fe3+/ΣFe ratios which are thought to be magmatic, whereas a few samples are highly oxidized and have high Fe3+/ΣFe ratios. There is also a group of partially oxidized samples. The oxidized chromites show anomalously low cell edge (a 0) values and their oxygen positional parameters among the lowest ever found for chromites. Site occupancy calculations show that some chromites are non-stoichiometric and contain vacancies in their structure randomly distributed between both the T and M sites. The field relationships suggest that the oxidation of the magmatic chromitites took place in association with a ductile shear zone in mantle harzburgites. Primary magmatic Fe3+/ΣFe ratios measured for the Oman mantle chromitites are between 0.193–0.285 (X-ray data) and 0.164–0.270 (Mössbauer data) and preserve a range of Fe3+/ΣFe ratios which we propose is real and reflects differences in the composition of the magmas parental to the chromitites. The range of values extends from those MORB melts (0.16 ± 0.1) to those for arc basalts (0.22–0.28). 相似文献