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71.
72.
Karl F. Nordstrom Enzo Pranzini Nancy L. Jackson Massimo Coli 《Geographical review》2008,98(2):280-300
ABSTRACT. Beach‐nourishment operations designed to replace sediment lost through erosion change the identity and meaning of coastal landscapes. Seven beaches in Tuscany, nourished with marble‐quarry waste, reveal how an industrial byproduct is naturalized by particle rounding and sorting and can become a positive symbol of human‐altered nature. The marble was placed on formerly sandy beaches, resulting in different grain size and color of sediments, beach morphology, and value for human use. The abrasion rate of marble makes the nourished beaches unsatisfactory when viewed solely as protection structures, but the rapid particle rounding and aesthetic appeal of marble increase the acceptability of the beaches for recreation. 相似文献
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75.
In order to provide the tools for uniform size determination for Mediterranean earthquakes over the last 50-year period of instrumental seismology, we have regressed the magnitude determinations for 220 earthquakes of the European-Mediterranean region over the 1977–1991 period, reported by three international centres, 11 national and regional networks and 101 individual stations and observatories, using seismic moments from the Harvard CMTs. We calibrate M(M0) regression curves for the magnitude scales commonly used for Mediterranean earthquakes (ML, MWA, mb, MS, MLH, MLV, MD, M); we also calibrate static corrections or specific regressions for individual observatories and we verify the reliability of the reports of different organizations and observatories. Our analysis shows that the teleseismic magnitudes (mb, MS) computed by international centers (ISC, NEIC) provide good measures of earthquake size, with low standard deviations (0.17–0.23), allowing one to regress stable regional calibrations with respect to the seismic moment and to correct systematic biases such as the hypocentral depth for MS and the radiation pattern for mb; while mb is commonly reputed to be an inadequate measure of earthquake size, we find that the ISC mb is still today the most precise measure to use to regress MW and M0 for earthquakes of the European-Mediterranean region; few individual observatories report teleseismic magnitudes requiring specific dynamic calibrations (BJI, MOS). Regional surface-wave magnitudes (MLV, MLH) reported in Eastern Europe generally provide reliable measures of earthquake size, with standard deviations often in the 0.25–0.35 range; the introduction of a small (±0.1–0.2) static station correction is sometimes required. While the Richter magnitude ML is the measure of earthquake size most commonly reported in the press whenever an earthquake strikes, we find that ML has not been computed in the European-Mediterranean in the last 15 years; the reported local magnitudes MWA and ML do not conform to the Richter formula and are of poor quality and little use, with few exceptions requiring ad hoc calibrations similar to the MS regression (EMSC, ATH). The duration magnitude MD used by most seismic networks confirms that its use requires accurate station calibrations and should be restricted only to events with low seismic moments. 相似文献
76.
Reconstruction of the eruptive activity on the NE sector of Stromboli volcano: timing of flank eruptions since 15 ka 总被引:1,自引:0,他引:1
Sonia Calvari Stefano Branca Rosa Anna Corsaro Emanuela De Beni Lucia Miraglia Gianluca Norini Jan Wijbrans Enzo Boschi 《Bulletin of Volcanology》2011,73(1):101-112
A multidisciplinary geological and compositional investigation allowed us to reconstruct the occurrence of flank eruptions
on the lower NE flank of Stromboli volcano since 15 ka. The oldest flank eruption recognised is Roisa, which occurred at ~15 ka
during the Vancori period, and has transitional compositional characteristics between the Vancori and Neostromboli phases.
Roisa was followed by the San Vincenzo eruption that took place at ~12 ka during the early stage of Neostromboli period. The
eruptive fissure of San Vincenzo gave rise to a large scoria cone located below the village of Stromboli, and generated a
lava flow, most of which lies below sea level. Most of the flank eruptions outside the barren Sciara del Fuoco occurred in
a short time, between ~9 and 7 ka during the Neostromboli period, when six eruptive events produced scoria cones, spatter
ramparts and lava flows. The Neostromboli products belong to a potassic series (KS), and cluster in two differently evolved
groups. After an eruptive pause of ~5,000 years, the most recent flank eruption involving the NE sector of the island occurred
during the Recent Stromboli period with the formation of the large, highly K calc-alkaline lava flow field, named San Bartolo.
The trend of eruptive fissures since 15 ka ranges from N30°E to N55°E, and corresponds to the magma intrusions radiating from
the main feeding system of the volcano. 相似文献
77.
Enzo Martinelli Francesco Perri Carmen Sguazzo Ciro Faella 《Bulletin of Earthquake Engineering》2016,14(6):1695-1720
This work reports the results of an experimental programme aimed at investigating the in-plane behaviour of clay-brick masonry walls externally strengthened by carbon fiber reinforced polymer (CFRP) strips. Particularly, four different geometrical layouts were considered for the CFRP strips, though keeping unchanged the quantity of composites employed in each wall. Firstly, a preliminary experimental work was carried out on samples of the constitutive materials for quantifying their key mechanical properties and evaluating the bond behaviour of FRP strips on the masonry substrates. Then, eleven cyclic shear-compression tests were performed to observe the response of strengthened walls and the influence of the strengthening layouts under investigation. The proposed experimental report is intended as a contribution to the current state of knowledge about the behaviour of FRP-strengthened masonry walls: it is available to assess the accuracy and possibly improve the predictive capacity of design-oriented capacity models. Finally, the comparison of the reported experimental results with the predictions obtained by applying the analytical relationships proposed by a recently issued guideline for FRP strengthening of masonry structures is proposed. 相似文献
78.
Alessandro Fornaciai Boris Behncke Massimiliano Favalli Marco Neri Simone Tarquini Enzo Boschi 《Bulletin of Volcanology》2010,72(10):1209-1222
The 2001 and 2002–2003 flank eruptions on Mount Etna (Italy) were characterized by intense explosive activity which led to
the formation of two large monogenetic scoria cones (one from each eruption) on the upper southern flank of the volcano. Continuous
monitoring of Etna, especially during flank eruptions, has provided detailed information on the growth of these cones. They
differ in genesis, shape, and size. A set of high resolution (1 m) digital elevation models (DEMs) derived from light detection
and ranging (LIDAR) data collected during four different surveys (2004, 2005, 2006, and 2007) has been used to map morphology
and to extract the morphometric parameters of the scoria cones. By comparing LIDAR-derived DEMs with a pre-eruption (1998)
10 m DEM, the volume of the two scoria cones was calculated for the first time. Comparison of the LIDAR-derived DEMs revealed
in unprecedented detail morphological changes during scoria cone degradation. In particular, the morphologically more exposed
and structurally weaker 2002–2003 cone was eroded rapidly during the first few years after its emplacement mainly due to gravitational
instability of slopes and wind erosion. 相似文献
79.
Francesco Mulargia Stefano Tinti Enzo Boschi 《Journal of Volcanology and Geothermal Research》1985,23(3-4)
A singularly complete record exists for the eruptive activity of Etna volcano. The time series of occurrence of flank eruptions in the period 1600–1980, in which the record is presumably complete, is found to follow a stationary Poisson process. A revision of the available data shows that eruption durations are rather well correlated with the estimates of the volume of lava flows. This implies that the magnitude of an eruption can be defined directly by its duration. Extreme value statistics are then applied to the time series, using duration as a dependent variable. The probability of occurrence of a very long (300 days) eruption is greater than 50% only in time intervals of the order of 50 years. The correlation found between duration and total output also allows estimation of the probability of occurrence of a major event which exceeds a given duration and total flow of lava. The composite probabilities do not differ considerably from the pure ones. Paralleling a well established application to seismic events, extreme value theory can be profitably used in volcanic risk estimates, provided that appropriate account is also taken of all other variables. 相似文献
80.
The aim of this paper is to provide some constrains on the time behavior of earthquake generation mechanism, through the usage of a non-parametric statistics that leads up to the empirical estimation of the hazard function. The results indicate that the most characterizing temporal feature for large (M 7.0+) worldwide shallow earthquake occurrence is a clustering lasting few years, indicating that the probability of earthquake occurrence is higher immediately after the occurrence of an event. After that, the process becomes almost time independent, as in a Poisson process. Remarkably, this time clustering is very similar to what previously found for different spatio-magnitude windows, and it does not seem to depend on the tectonic style of the region. This may support the hypothesis of an universal law for earthquake occurrence. 相似文献