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631.
A new, passive, vibroprotective device of the rolling‐pendulum tuned mass damper type is presented that, relying on a proper three‐dimensional guiding surface, can simultaneously control the response of the supporting structure in two mutually orthogonal horizontal directions. Unlike existing examples of ball vibration absorbers, mounted on spherical recesses and effective for axial‐symmetrical structures, the new device is bidirectionally tuneable, by virtue of the optimum shape of the rolling cavity, to both fundamental structural modes, even when the corresponding natural frequencies are different, in such a case recurring to an innovative non‐axial‐symmetrical rolling guide. Based on Appell's non‐holonomic mechanics, a non‐linear dynamic model is first derived for the bidirectional absorber mounted on a 1‐storey 3‐degrees‐of‐freedom linear structure translating under the effect of both imparted base motion and applied dynamic forces. A laboratory‐scaled prototype of the device is then tested to experimentally demonstrate the bidirectional tuning capability and to validate the mathematical model. The design procedure and the seismic performance of the absorber are finally exemplified through numerical simulation. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
632.
Salvatore Alparone Andrea Cannata Salvatore Gambino Stefano Gresta Vincenzo Milluzzo Placido Montalto 《Bulletin of Volcanology》2010,72(7):803-816
We investigated the relationship between volcano-seismic events, recorded at La Fossa crater of Vulcano (Aeolian Islands,
Italy) during 2004-2006, and the dynamics of the hydrothermal system. During the period of study, three episodes of increasing
numbers of volcano-seismic events took place at the same time as geothermal and geochemical anomalies were observed. These
geothermal and geochemical anomalies have been interpreted as resulting from an increasing deep magmatic component of the
hydrothermal fluids. Three classes of seismic events (long period, high frequency and monochromatic events), characterised
by different spectral content and various similarity of the waveforms, have been recognised. These events, clustered mainly
below La Fossa crater area at depths of 0.5–1.1 km b.s.l., were space-distributed according to the classes. Based on their
features, we can infer that such events at Vulcano are related to two different source mechanisms: (1) fracturing processes
of rocks and (2) resonance of cracks (or conduits) filled with hydrothermal fluid. In the light of these source mechanisms,
the increase in the number of events, at the same time as geochemical and geothermal anomalies were observed, was interpreted
as the result of an increasing magmatic component of the hydrothermal fluids, implying an increase of their flux. Indeed,
such variation caused an increase of both the pore pressure within the rocks of the volcanic system and the amount of ascending
fluids. Increased pore pressures gave rise to fracturing processes, while the increased fluid flux favoured resonance and
vibration processes in cracks and conduits. Finally, a gradual temporal variation of the waveform of the hybrid events (one
of the subclasses of long period events) was observed, likely caused by heating and drying of the hydrothermal system. 相似文献
633.
Caldera eruptions are among the most hazardous of natural phenomena. Many calderas around the world are active and are characterised
by recurrent uplift and subsidence periods due to the dynamics of their magma reservoirs. These periods of unrest are, in
some cases, accompanied by eruptions. At Campi Flegrei caldera (CFc), which is an area characterised by very high volcanic
risk, the recurrence of this behaviour has stimulated the study of the rock rheology around the magma chamber, in order to
estimate the likelihood of an eruption. This study considers different scenarios of shallow crustal behaviour, taking into
account the earlier models of CFc ground deformation and caldera eruptions, and including recent geophysical investigations
of the area. A semi-quantitative evaluation of the different factors that lead to magma storage or to its eruption (such as
magma chamber size, wall-rock viscosity, temperature, and regional tectonic strain rate) is reported here for elastic and
viscoelastic conditions. Considering the large magmatic sources of the CFc ignimbrite eruptions (400–2,000 km3) and a wall-rock viscosity between 1018 and 1020 Pa s, the conditions for eruptive failure are difficult to attain. Smaller source dimensions (a few cubic kilometres) promote
the condition for fracture (eruption) rather than for the flow of wall rock. We also analyse the influence of the regional
extensional stress regime on magma storage and eruptions, and the thermal stress as a possible source of caldera uplift. The
present study also emphasises the difficulty of distinguishing eruption and non-eruption scenarios at CFc, since an unambiguous
model that accounts for the rock rheology, magma-source dimensions and locations and regional stress field influences is still
lacking. 相似文献
634.
Lucia Luzi Sara Lovati Ezio D’Alema Simone Marzorati Domenico Di Giacomo Salomon Hailemikael Ettore Cardarelli Michele Cercato Gerarda Di Filippo Giuliano Milana Giuseppe Di Giulio Mario Rainone Patrizio Torrese Patrizio Signanini Gabriele Scarascia Mugnozza Stefano Rivellino Antonella Gorini 《Bulletin of Earthquake Engineering》2010,8(5):1189-1207
Geological, geophysical and geotechnical investigations, for the characterization of the strong-motion recording sites managed by the Italian Civil Protection, have been carried out in the framework of the project “Italian strong-motion database in the period 1972–2004”. The project aimed at creating an updated database of strong-motion data acquired in Italy by different institutions in the time span 1972–2004, and at improving the quality of disseminated data. This article illustrates the state of the recording site characterization before the beginning of the project, explains the criteria adopted to select the sites where geophysical/geotechnical investigation have been performed and describes the results of the promoted field surveys. 相似文献
635.
Paolo Mazzetti Giuseppe Puglisi Luca D’Auria Roberto Roncella Danilo Reitano Riccardo Merenda Stefano Nativi 《Earth Science Informatics》2017,10(4):443-455
This paper presents the Virtual Research Environment (VRE) enabling two European GEO Geohazard Supersites in Italy. According to GEO (Group on Earth Observation) vision, Geohazard Supersites provide access to spaceborne and in-situ geophysical data and models for selected sites prone to natural hazards –noticeably, earthquakes and volcano eruptions. The VRE was implemented in the framework of the Mediterranean Supersite Volcanoes (MED-SUV) project, funded by the European Commission. MED-SUV realized one of the European supersite demonstrators covering the two Permanent Supersites selected in Italy: Mt. Etna and Campi Flegrei/Vesuvius. The MED-SUV VRE provides advanced services for heterogeneous data and information management and sharing. MED-SUV started identifying the main supersite requirements including: the interoperability with existing data/information supply systems, the support of policy-based access control, the access to processing capabilities provided by external platforms, the management resources for publishing and sharing new products, the integration with significant global systems such as GEOSS and EPOS. MED-SUV adopted a System of Systems (SoS) approach to address interoperability with the identified heterogeneous systems supplying data and information. The SoS approach is based on a brokering architecture, where a specialized component (i.e the MED-SUV Broker: MSB) connects the existing and next-coming data sources leaving them autonomous. MSB carries out all the necessary mediation and harmonization tasks exposing standard interfaces enabling the interconnection with external systems like GEOSS and EPOS. In addition, MSB is accessible via a JavaScript library implementing Web APIs to facilitate the development of Web and mobile applications. 相似文献
636.
Teresa Salvatici Stefano Morelli Veronica Pazzi William Frodella Riccardo Fanti 《山地科学学报》2017,14(4):636-648
On 4th November 2010, a debris flow detached from a large debris cover accumulated above the lowermost portion of the Rotolon landslide (Vicentine Pre-Alps, NE Italy) and channelized in the valley below within the Rotolon Creek riverbed. Such event evolved into a highly mobile and sudden debris flow, damaging some hydraulic works and putting at high risk four villages located along the creek banks. A monitoring campaign was carried out by means of a ground based radar interferometer (GB-InSAR) to evaluate any residual displacement risk in the affected area and in the undisturbed neighbouring materials. Moreover, starting from the current slope condition, a landslide runout numerical modelling was performed by means of DAN-3D code to assess the impacted areas, flow velocity, and deposit distribution of the simulated events. The rheological parameters necessary for an accurate modelling were obtained through the back analysis of the 2010 debris flow event. Back analysis was calibrated with all of the available terrain data coming from field surveys and ancillary documents, such as topographic, geomorphological and geological maps, with pre- and post-event LiDAR derived DTMs, and with orthophotos. Finally, to identify new possible future debris flow source areas as input data for the new modelling, all the obtained terrain data were reanalysed and integrated with the GB-InSAR displacement maps; consequently, new simulations were made to forecast future events. The results show that the integration of the selected modelling technique with ancillary data and radar displacement maps can be a very useful tool for managing problems related to debris flow events in the examined area. 相似文献
637.
Danilo Cavallaro Carmelo Monaco Alina Polonia Attilio Sulli Agata Di Stefano 《Natural Hazards》2017,86(2):233-251
In order to unravel the tectonic evolution of the north-central sector of the Sicily Channel (Central Mediterranean), a seismo-stratigraphic analysis of single- and multi-channel seismic reflection profiles has been carried out. This allowed to identify, between 20 and 50 km offshore the central-southern coast of Sicily, a ~80-km-long deformation belt, characterized by a set of WNW–ESE to NW–SE fault segments showing a poly-phasic activity. Within this belt, we observed: i) Miocene normal faults reactivated during Zanclean–Piacenzian time by dextral strike-slip motion, as a consequence of the Africa–Europe convergence; ii) releasing and restraining bend geometries forming well-developed pull-apart basins and compressive structures. In the central and western sectors of the belt, we identified local transpressional reactivations of Piacenzian time, attested by well-defined compressive features like push-up structures and fault-bend anticlines. The reconstruction of timing and style of tectonic deformation suggest a strike-slip reactivation of inherited normal faults and the local subsequent positive tectonic inversion, often documented along oblique thrust ramps. This pattern represents a key for an improved knowledge of the structural style of foreland fold-and-thrust belts propagating in a preexisting extensional domain. With regard to active tectonics and seismic hazards, recent GPS data and local seismicity events suggest that this deformation process could be still active and accomplished through deep-buried structures; moreover, several normal faults showing moderate displacements have been identified on top of the Madrepore Bank and Malta High, offsetting the Late Quaternary deposits. Finally, inside the northern part of the Gela Basin, multiple slope failures, originated during Pleistocene by the further advancing of the Gela Nappe, reveal tectonically induced potential instability processes. 相似文献
638.
Results from visual sightings of large floating debris are presented, taken in the Ligurian Sea, a sub-basin of the north-western Mediterranean Sea which belongs to the recently stated "Cetacean Sanctuary". Data have been collected during three oceanographic cruises, during the summer of 1997 and 2000. Results for the 1997 data suggest a debris density of the order of 15-25 objects km(-2), while for the 2000 data, a lower density of the order of 3-1.5 objects km(-2) is found. The difference between the two results appears statistically significant using simple tests. Possible reasons for the observed variability are discussed, including meteorological forcing, marine currents and debris input variability. 相似文献
639.
Algorithms for GPS operation indoors and downtown 总被引:6,自引:0,他引:6
Nainesh Agarwal Julien Basch Paul Beckmann Piyush Bharti Scott Bloebaum Stefano Casadei Andrew Chou Per Enge Wungkum Fong Neesha Hathi Wallace Mann Anant Sahai Jesse Stone John Tsitsiklis Benjamin Van Roy 《GPS Solutions》2002,6(3):149-160
The proliferation of mobile devices and the emergence of wireless location-based services has generated consumer demand for
availability of GPS in urban and indoor environments. This demand calls for enhanced GPS algorithms that accommodate high
degrees of signal attenuation and multipath effects unique to the "urban channel." This paper overviews the market for location-based
services and discusses algorithmic innovations that address challenges posed by urban environments.
Electronic Publication 相似文献
640.
EDELWEISS Collaboration P. Di Stefano L. Berg B. Chambon M. Chapellier J. Chaumont G. Chardin P. Charvin M. De Jsus D. Drain L. Dumoulin P. Forget P. Garoche J. Gascon C. Goldbach D. L'Hte J. Mallet J. Mangin S. Marnieros L. Miramonti L. Mosca X-F. Navick G. Nollez P. Pari S. Pcourt E. Simon L. Stab J-P. Torre R. Tourbot D. Yvon 《Astroparticle Physics》2001,14(4):1425
The discrimination capabilities of a 70 g heat and ionization Ge bolometer are studied. This first prototype has been used by the EDELWEISS dark matter experiment, installed in the Laboratoire Souterrain de Modane, for direct detection of WIMPs. Gamma and neutron calibrations demonstrate that this type of detector is able to reject more than 99.6% of the background while retaining 95% of the signal, provided that the background events distribution is not biased towards the surface of the Ge crystal. However, the 1.17 kg day of data taken in a relatively important radioactive environment show an extra population slightly overlapping the signal. This background is likely due to interactions of low energy photons or electrons near the surface of the crystal, and is somewhat reduced by applying a higher charge-collecting inverse bias voltage (−6 V instead of −2 V) to the Ge diode. Despite this contamination, more than 98% of the background can be rejected while retaining 50% of the signal. This yields a conservative upper limit of 0.7 event day−1 kg−1 keVrecoil−1 at 90% confidence level in the 15–45 keV recoil energy interval; the present sensitivity appears to be limited by the fast ambient neutrons. Upgrades in progress on the installation are summarized. 相似文献