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131.
G. Milana R. M. Azzara E. Bertrand P. Bordoni F. Cara R. Cogliano G. Cultrera G. Di Giulio A.M. Duval A. Fodarella S. Marcucci S. Pucillo J. R��gnier G. Riccio 《Bulletin of Earthquake Engineering》2011,9(3):741-759
After the 2009 April 6th Mw 6.3 L??Aquila earthquake (Central Italy) the Italian Civil Defense Department promoted the microzoning study in the ten zones in the epicentral area that suffered major damage. In this paper we present the activities and the results concerning a temporary seismic network installed in the historical L??Aquila city center indicated as ??macroarea 1?? in the microzoning project. Seismic data were collected to investigate the amplification effects in the city and to support the microzoning activities in verifying both geological profiles and 1D numerical modeling of the seismic response of the city. The conventional spectral approaches using both microtremor and earthquake data allowed to determine the fundamental resonance frequencies and the amplification factors within the city respectively. The spatial variability of these quantities can be related to the geological and geomorphologic characteristics of the investigated area. A comparison between the network data and the data recorded by the two strong motion instruments installed in the city was also made. This allows verifying the relative response of the accelerometric stations that recorded in the city the major events of the sequence. 相似文献
132.
Over the last three decades, many regional studies in mountain ranges under temperate climate revealed that it is possible to discriminate debris-flow and fluvial fans from morphometric indicators measured at the scale of the catchment and the fan itself. The most commonly used indicators are the Melton index (R), a normalized index of the gravitational energy of the catchment, and the fan slope (S). A wide range of thresholds have been proposed for discriminating purpose, but these are generally based on a small population of catchments and may be highly influenced by ambiguous fans included in the data set. A database of 620 upland catchments from several mountain ranges under temperate climate was compiled from the literature to propose robust discriminant morphometric thresholds for debris-flow versus fluvial responses. Linear discriminant analysis (LDA) and logistic regression (LR) were performed using the whole data set, and a leave-one-out cross-validation was used to evaluate performances of the models. Sensitivity and specificity scores obtained for LDA and LR were 0.96 and 0.73, and 0.95 and 0.75, respectively. It is also shown that the channel slope above which debris-flow is observed decreases with the gravitational energy of the catchment. Limitations of the morphometric discrimination are discussed. 相似文献
133.
A. Scharf M. R. Handy S. Favaro S. M. Schmid A. Bertrand 《International Journal of Earth Sciences》2013,102(6):1627-1654
The Tauern Window exposes a Paleogene nappe stack consisting of highly metamorphosed oceanic (Alpine Tethys) and continental (distal European margin) thrust sheets. In the eastern part of this window, this nappe stack (Eastern Tauern Subdome, ETD) is bounded by a Neogene system of shear (the Katschberg Shear Zone System, KSZS) that accommodated orogen-parallel stretching, orogen-normal shortening, and exhumation with respect to the structurally overlying Austroalpine units (Adriatic margin). The KSZS comprises a ≤5-km-thick belt of retrograde mylonite, the central segment of which is a southeast-dipping, low-angle extensional shear zone with a brittle overprint (Katschberg Normal Fault, KNF). At the northern and southern ends of this central segment, the KSZS loses its brittle overprint and swings around both corners of the ETD to become subvertical, dextral, and sinistral strike-slip faults. The latter represent stretching faults whose displacements decrease westward to near zero. The kinematic continuity of top-east to top-southeast ductile shearing along the central, low-angle extensional part of the KSZS with strike-slip shearing along its steep ends, combined with maximum tectonic omission of nappes of the ETD in the footwall of the KNF, indicates that north–south shortening, orogen-parallel stretching, and normal faulting were coeval. Stratigraphic and radiometric ages constrain exhumation of the folded nappe complex in the footwall of the KSZS to have begun at 23–21 Ma, leading to rapid cooling between 21 and 16 Ma. This exhumation involved a combination of tectonic unroofing by extensional shearing, upright folding, and erosional denudation. The contribution of tectonic unroofing is greatest along the central segment of the KSZS and decreases westward to the central part of the Tauern Window. The KSZS formed in response to the indentation of wedge-shaped blocks of semi-rigid Austroalpine basement located in front of the South-Alpine indenter that was part of the Adriatic microplate. Northward motion of this indenter along the sinistral Giudicarie Belt offsets the Periadriatic Fault and triggered rapid exhumation of orogenic crust within the entire Tauern Window. Exhumation involved strike-slip and normal faulting that accommodated about 100 km of orogen-parallel extension and was contemporaneous with about 30 km of orogen-perpendicular, north–south shortening of the ETD. Extension of the Pannonian Basin related to roll-back subduction in the Carpathians began at 20 Ma, but did not affect the Eastern Alps before about 17 Ma. The effect of this extension was to reduce the lateral resistance to eastward crustal flow away from the zone of greatest thickening in the Tauern Window area. Therefore, we propose that roll-back subduction temporarily enhanced rather than triggered exhumation and orogen-parallel motion in the Eastern Alps. Lateral extrusion and orogen-parallel extension in the Eastern Alps have continued from 12 to 10 Ma to the present and are driven by northward push of Adria. 相似文献
134.
The seismological study of recent seismic crises near Oleron Island confirms the coexistence of an extensional deformation and a transtensive regime in the Atlantic margin of France, which is different from the general western European stress field corresponding to a strike-slip regime. We argue that the switch of the principal stress axes σ1/σ2 in a NW–SE vertical plane is linked with the existence of crustal heterogeneities. Events of magnitude larger than 5 sometimes occur along the Atlantic margin of France, such as the 7 September 1972 (ML = 5.2) earthquake near Oleron island and the 30 September 2002 (ML = 5.7) Hennebont event in Brittany. To test the mechanism of local strain localization, we model the deformation of the hypocentral area of the Hennebont earthquake using a 3D thermo-mechanical finite element code. We conclude that the occurrence of moderate earthquakes located in limited parts of the Hercynian shear zones (as the often reactivated swarms near Oleron) could be due to local reactivation of pre-existing faults. These sporadic seismic ruptures are favoured by stress concentration due to rheological heterogeneities. 相似文献
135.
This paper uses the OECD’s global recursive-dynamic general equilibrium model ENVLinkages to examine the mid-term economic consequences and the optimal energy supply mix adjustments of a simultaneous implementation of i) a progressive fossil fuel subsidy reform in emerging and developing economies and ii) a progressive phase out of nuclear energy, mostly affecting OECD countries, China and Russia. The analysis is then transposed in the context of climate change mitigation to depict the corresponding implications for CO2 emissions, to assess the interactions between the two energy policies, and to derive how the associated costs are affected by the different policies. The phase-out scenario projects a nuclear capacity halved by 2035 as compared to the Baseline, corresponding to $120 billion losses in value-added of the nuclear industry for that year. The nuclear phase-out leaves GDP and real household consumption marginally affected in energy importing countries. A multilateral subsidy reform is more likely to affect international fossil fuel prices and alter patterns of global energy use. The fossil fuel subsidy reform, when implemented together with nuclear phase-out, more than offsets negative consequences on household consumption but still leads to a decrease in global CO2 emissions. The combined policies help save the equivalent of current energy consumption in the Middle East. Combining a climate policy, an effective fossil fuel subsidy reform, even with a lower nuclear share in the power mix, brings about multiple benefits to OECD countries which reduce their energy bill and achieve large climate change mitigation at lower cost. 相似文献
136.
Alberto Araneda Patricia Jana Carolina Ortega Fernando Torrejón Sébastien Bertrand Patricia Vargas Nathalie Fagel Denisse Alvarez Alejandra Stehr Roberto Urrutia 《Journal of Paleolimnology》2013,50(1):41-56
Patagonia is commonly seen as an exceptionally pristine area because of its wildlife and practically unpolluted waters. However, during the twentieth century the burning of natural forests was one of the most important human activities in Northern Chilean Patagonia. Some estimations indicate that three million hectares were burned during the first three decades of the century. Hence the objective of this study was to evaluate the impacts of the historical fires in Lake Burgos (45º42′S) and Lake Thompson (45º38′S) in Chilean Patagonia. The impact was measured by evaluating chironomid assemblage since they are sensitive enough to be used as an indicator of aquatic ecosystem health. Fires have a direct and drastic effect on a lake watershed but also indirectly affect a lake ecosystem, changing sedimentation patterns or increasing nutrient inputs. In the studied lakes the periods with higher prevalence of fires were identified by charcoal analysis, while organic matter and magnetic susceptibility allowed the confirmation of pre-fire and post-fire periods. The chironomid composition was evaluated through a PCA and an analysis of similarity (ANOSIM) to test the significance among periods while a Detrended Correspondence Analysis was applied to the chironomid assemblage downcore to assess compositional structure and taxa turnover. In Lake Burgos the ANOSIM test indicated significant differences between the pre-fire and fire periods (p < 0.05), while in Lake Thompson differences were not significant. However, in Lake Thompson the PCA clearly separated the pre-fire from the fire period but not the fire from the post-fire periods. In both lakes chironomid composition changed in relation to the period of higher prevalence of fires, which in turn implies catchment changes, pollution, and other anthropogenic impacts. Particularly a marked change in mesotrophic/eutrophic taxa was detected, reflecting an increase in nutrient input due to deforestation. Our findings point out that the lacustrine ecosystems are still affected by the impact of fires and the subsequent increase in nutrient supply that occurred almost 50 years ago. No sign of reverting to pre-disturbance conditions was observed, which makes these lakes highly sensitive to current human-induced impacts. 相似文献
137.
Donghua Zhao Bertrand Cordier Patrick Sizun Bobing Wu Yongwei Dong Stéphane Schanne Liming Song Jiangtao Liu 《Experimental Astronomy》2012,34(3):705-728
SVOM (Space-based multi-band astronomical Variable Object Monitor) is a future Chinese-French satellite mission which is dedicated to Gamma-Ray Burst (GRB) studies. Its anti-solar pointing strategy makes the Earth cross the field of view of its payload every orbit. In this paper, we present the variations of the gamma-ray background of the two high energy instruments aboard SVOM, the Gamma-Ray Monitor (GRM) and ECLAIRs, as a function of the Earth position. We conclude with an estimate of the Earth influence on their sensitivity and their GRB detection capability. 相似文献
138.
Jérome Salichon Carine Kohrs-Sansorny Etienne Bertrand Françoise Courboulex 《Journal of Seismology》2010,14(3):523-541
The southern Alps–Ligurian basin junction is one of the most seismically active zone of the western Europe. A constant microseismicity
and moderate size events (3.5 < M < 5) are regularly recorded. The last reported historical event took place in February 1887
and reached an estimated magnitude between 6 and 6.5, causing human losses and extensive damages (intensity X, Medvedev–Sponheuer–Karnik).
Such an event, occurring nowadays, could have critical consequences given the high density of population living on the French
and Italian Riviera. We study the case of an offshore Mw 6.3 earthquake located at the place where two moderate size events
(Mw 4.5) occurred recently and where a morphotectonic feature has been detected by a bathymetric survey. We used a stochastic
empirical Green’s functions (EGFs) summation method to produce a population of realistic accelerograms on rock and soil sites
in the city of Nice. The ground motion simulations are calibrated on a rock site with a set of ground motion prediction equations
(GMPEs) in order to estimate a reasonable stress-drop ratio between the February 25th, 2001, Mw 4.5, event taken as an EGF
and the target earthquake. Our results show that the combination of the GMPEs and EGF techniques is an interesting tool for
site-specific strong ground motion estimation. 相似文献
139.
Øyvind Breivik Arthur A. Allen Christophe Maisondieu Jens-Christian Roth Bertrand Forest 《Ocean Dynamics》2012,62(5):741-752
The leeway of 20-ft containers in typical distress conditions is established through field experiments in a Norwegian fjord
and in open-ocean conditions off the coast of France with a wind speed ranging from calm to 14 m s−1. The experimental setup is described in detail, and certain recommendations were given for experiments on objects of this
size. The results are compared with the leeway of a scaled-down container before the full set of measured leeway characteristics
are compared with a semianalytical model of immersed containers. Our results are broadly consistent with the semianalytical
model, but the model is found to be sensitive to choice of drag coefficient and makes no estimate of the crosswind leeway
of containers. We extend the results from the semianalytical immersion model by extrapolating the observed leeway divergence
and estimates of the experimental uncertainty to various realistic immersion levels. The sensitivity of these leeway estimates
at different immersion levels are tested using a stochastic trajectory model. Search areas are found to be sensitive to the
exact immersion levels, the choice of drag coefficient, and somewhat less sensitive to the inclusion of leeway divergence.
We further compare the search areas, thus, found with a range of trajectories estimated using the semianalytical model with
only perturbations to the immersion level. We find that the search areas calculated without estimates of crosswind leeway
and its uncertainty will grossly underestimate the rate of expansion of the search areas. We recommend that stochastic trajectory
models of container drift should account for these uncertainties by generating search areas for different immersion levels
and with the uncertainties in crosswind and downwind leeway reported from our field experiments. 相似文献
140.
Nicolas Reul Severine Fournier Jaqueline Boutin Olga Hernandez Christophe Maes Bertrand Chapron Gaël Alory Yves Quilfen Joseph Tenerelli Simmon Morisset Yann Kerr Susanne Mecklenburg Steven Delwart 《Surveys in Geophysics》2014,35(3):681-722
While it is well known that the ocean is one of the most important component of the climate system, with a heat capacity 1,100 times greater than the atmosphere, the ocean is also the primary reservoir for freshwater transport to the atmosphere and largest component of the global water cycle. Two new satellite sensors, the ESA Soil Moisture and Ocean Salinity (SMOS) and the NASA Aquarius SAC-D missions, are now providing the first space-borne measurements of the sea surface salinity (SSS). In this paper, we present examples demonstrating how SMOS-derived SSS data are being used to better characterize key land–ocean and atmosphere–ocean interaction processes that occur within the marine hydrological cycle. In particular, SMOS with its ocean mapping capability provides observations across the world’s largest tropical ocean fresh pool regions, and we discuss from intraseasonal to interannual precipitation impacts as well as large-scale river runoff from the Amazon–Orinoco and Congo rivers and its offshore advection. Synergistic multi-satellite analyses of these new surface salinity data sets combined with sea surface temperature, dynamical height and currents from altimetry, surface wind, ocean color, rainfall estimates, and in situ observations are shown to yield new freshwater budget insight. Finally, SSS observations from the SMOS and Aquarius/SAC-D sensors are combined to examine the response of the upper ocean to tropical cyclone passage including the potential role that a freshwater-induced upper ocean barrier layer may play in modulating surface cooling and enthalpy flux in tropical cyclone track regions. 相似文献