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101.
The present work reports on the isotopic characterization of rainfall and groundwater at Mt. Vesuvius. Values of δ 18O, monthly measured on rain samples collected during the period 2002–2004 in a rain-gauge network composed of 10 stations, were compared with meteorological and DEM data. Air temperature, controlled by the local orographic structure, was identified as the main factor influencing rain isotopic composition. Another important role is played by orographic clouds, whose condensation over the top of Mt. Vesuvius is responsible for anomalously high δ 18O values recorded in rain samples from the summit area of the volcanic edifice. A spatial model of rain isotopic composition, based on a 3D distribution of temperature derived by a 1 × 1 km DEM, was implemented and used for calculating the theoretical isotopic signature of seepage, further compared with data measured in the groundwater monitoring network. The analysis evidenced the role of local meteoric recharge as the main source feeding Mt. Vesuvius aquifers. The unique exception is the Olivella drainage gallery, located on the north-eastern flank of the volcanic edifice, whose isotopic composition is slightly more positive than the one expected for its altitude, likely caused by both evaporation processes and mixing with condensed hydrothermal vapor. 相似文献
102.
Eleonora Ammannito M. Cristina De Sanctis Fabrizio Capaccioni M. Teresa Capria F. Carraro Jean‐Philippe Combe Sergio Fonte Alessandro Frigeri Steven P. Joy Andrea Longobardo Gianfranco Magni Simone Marchi Thomas B. McCord Lucy A. McFadden Harry Y. McSween Ernesto Palomba Carle M. Pieters Carol A. Polanskey Carol A. Raymond Jessica M. Sunshine Federico Tosi Francesca Zambon Christopher T. Russell 《Meteoritics & planetary science》2013,48(11):2185-2198
We present global lithological maps of the Vestan surface based on Dawn mission's Visible InfraRed (VIR) Spectrometer acquisitions with a spatial sampling of 200 m. The maps confirm the results obtained with the data set acquired by VIR with a spatial sampling of 700 m, that the reflectance spectra of Vesta's surface are dominated by pyroxene absorptions that can be interpreted within the context of the distribution of howardites, eucrites, and diogenites (HEDs). The maps also partially agree with the ground and Hubble Space Telescope observations: they confirm the background surface being an assemblage of howardite or polymict eucrite, as well as the location of a diogenitic‐rich spot; however, there is no evidence of extended olivine‐rich regions in the equatorial latitudes. Diogenite is revealed on the Rheasilvia basin floor, indicating that material of the lower crust/mantle was exposed. VIR also detected diogenites along the scarp of Matronalia Rupes, and the rims of Severina and a nearby, unnamed crater, and as ejecta of Antonia crater. The diogenite distribution is fully consistent with petrological constraints; although the mapped distribution does not provide unambiguous constraints, it favors the hypothesis of a magma ocean. 相似文献
103.
104.
Christian Circi Emiliano Ortore Federico Bunkheila Carlo Ulivieri 《Celestial Mechanics and Dynamical Astronomy》2012,114(3):215-227
The multi-sun-synchronous orbits allow cycles of observation of the same area in which solar illumination repetitively changes according to the value of the orbit elements and returns to the initial condition after a temporal interval multiple of the repetition of observation. This paper generalizes the concept of multi-sun-synchronous orbits, whose classical sun-synchronous orbits represent particular solutions, taking into consideration the elliptical case. The feasibility of using this typology of orbits, referred to as elliptical periodic multi-sun-synchronous orbits, has been investigated for the exploration of Mars and particular solutions have been selected. Such solutions considerably reduce the manoeuvre of velocity variation at the end of the interplanetary transfer with respect to the case of a target circular orbit around Mars. They are based on the use of quasi-critical inclinations in order to minimize the apsidal line motion and thus reduce orbit maintenance costs. Moreover, in the case of high eccentricities, the argument of pericentre may be set in order to obtain, around the apocentre, a condition of quasi-synchronism with the planet (the footprint of the probe on the surface presents a small shift with respect to a fixed point on the Martian surface). The low altitude of pericentre allows observation of the planet at a higher spatial resolution, while the orbit arc around the apocentre may be used to observe Mars with a wide spatial coverage in quasi-stationary conditions. This latter characteristic is useful for analysing atmospheric and meteorological phenomena and it allows for most of the orbital period a link between a rover on the surface of Mars and a probe orbiting around the planet. 相似文献
105.
Assessment of rockfall susceptibility by integrating statistical and physically-based approaches 总被引:7,自引:1,他引:6
In Val di Fassa (Dolomites, Eastern Italian Alps) rockfalls constitute the most significant gravity-induced natural disaster that threatens both the inhabitants of the valley, who are few, and the thousands of tourists who populate the area in summer and winter.To assess rockfall susceptibility, we developed an integrated statistical and physically-based approach that aimed to predict both the susceptibility to onset and the probability that rockfalls will attain specific reaches. Through field checks and multi-temporal aerial photo-interpretation, we prepared a detailed inventory of both rockfall source areas and associated scree-slope deposits. Using an innovative technique based on GIS tools and a 3D rockfall simulation code, grid cells pertaining to the rockfall source-area polygons were classified as active or inactive, based on the state of activity of the associated scree-slope deposits. The simulation code allows one to link each source grid cell with scree deposit polygons by calculating the trajectory of each simulated launch of blocks. By means of discriminant analysis, we then identified the mix of environmental variables that best identifies grid cells with low or high susceptibility to rockfalls. Among these variables, structural setting, land use, and morphology were the most important factors that led to the initiation of rockfalls.We developed 3D simulation models of the runout distance, intensity and frequency of rockfalls, whose source grid cells corresponded either to the geomorphologically-defined source polygons (geomorphological scenario) or to study area grid cells with slope angle greater than an empirically-defined value of 37° (empirical scenario). For each scenario, we assigned to the source grid cells an either fixed or variable onset susceptibility; the latter was derived from the discriminant model group (active/inactive) membership probabilities.Comparison of these four models indicates that the geomorphological scenario with variable onset susceptibility appears to be the most realistic model. Nevertheless, political and legal issues seem to guide local administrators, who tend to select the more conservative empirically-based scenario as a land-planning tool. 相似文献
106.
Luca Ciotti Federico Marinacci 《Monthly notices of the Royal Astronomical Society》2008,387(3):1117-1125
In a previous paper, the complex-shift method has been applied to self-gravitating spherical systems, producing new analytical axisymmetric density–potential pairs. We now extend the treatment to the Miyamoto–Nagai disc and the Binney logarithmic halo, and we study the resulting axisymmetric and triaxial analytical density–potential pairs; we also show how to obtain the surface density of shifted systems from the complex shift of the surface density of the parent model. In particular, the systems obtained from Miyamoto–Nagai discs can be used to describe disc galaxies with a peanut-shaped bulge or with a central triaxial bar, depending on the direction of the shift vector. By using a constructive method that can be applied to generic axisymmetric systems, we finally show that the Miyamoto–Nagai and the Satoh discs, and the Binney logarithmic halo cannot be obtained from the complex shift of any spherical parent distribution. As a by-product of this study, we also found two new generating functions in closed form for even and odd Legendre polynomials, respectively. 相似文献
107.
Federico Carturan Mariano Angelo Zanini Carlo Pellegrino Claudio Modena 《Bulletin of Earthquake Engineering》2014,12(2):795-806
Natural threats like earthquakes, hurricanes or tsunamis have had serious impacts on communities. In the past, major earthquakes in the United States like Loma Prieta 1989, Northridge 1994, or recent events in Italy like L’Aquila 2009 or Emilia 2012 emphasized the importance of preparedness and awareness to reduce social impacts. In addition to that, earthquake damaged businesses dramatically reduced the gross regional product. Generating scenario earthquakes in a proper way is important to suitably assess the risk in bridge networks and social losses in terms of gross regional product reduction. Seismic hazard is traditionally assessed by means of probabilistic seismic hazard analysis (PSHA). Although PSHA well represents the hazard at a specific location it is not suitable for spatially distributed systems. Scenario earthquakes can overcome this problem; they represent the actual distribution of ground shaking for a spatially distributed system while being hazard consistent. In this work a methodology to generate scenario earthquakes has been proposed using a novel approach with the aim of being the basic step for investigating possible earthquake consequences in seismic areas and contributing to reduce losses. 相似文献
108.
Guidelines on the use of inverse velocity method as a tool for setting alarm thresholds and forecasting landslides and structure collapses 总被引:4,自引:4,他引:0
Tommaso Carlà Emanuele Intrieri Federico Di Traglia Teresa Nolesini Giovanni Gigli Nicola Casagli 《Landslides》2017,14(2):517-534
Predicting the time of failure is a topic of major concern in the field of geological risk management. Several approaches, based on the analysis of displacement monitoring data, have been proposed in recent years to deal with the issue. Among these, the inverse velocity method surely demonstrated its effectiveness in anticipating the time of collapse of rock slopes displaying accelerating trends of deformation rate. However, inferring suitable linear trend lines and deducing reliable failure predictions from inverse velocity plots are processes that may be hampered by the noise present in the measurements; data smoothing is therefore a very important phase of inverse velocity analyses. In this study, different filters are tested on velocity time series from four case studies of geomechanical failure in order to improve, in retrospect, the reliability of failure predictions: Specifically, three major landslides and the collapse of an historical city wall in Italy have been examined. The effects of noise on the interpretation of inverse velocity graphs are also assessed. General guidelines to conveniently perform data smoothing, in relation to the specific characteristics of the acceleration phase, are deduced. Finally, with the aim of improving the practical use of the method and supporting the definition of emergency response plans, some standard procedures to automatically setup failure alarm levels are proposed. The thresholds which separate the alarm levels would be established without needing a long period of neither reference historical data nor calibration on past failure events. 相似文献
109.
Vittorio Di Federico Marco Pinelli Rita Ugarelli 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(7):1067-1076
An understanding of the interplay between non-Newtonian effects in porous media flow and field-scale domain heterogeneity
is of great importance in several engineering and geological applications. Here we present a simplified approach to the derivation
of an effective permeability for flow of a purely viscous power–law fluid with flow behavior index n in a randomly heterogeneous porous domain subject to a uniform pressure gradient. A standard form of the flow law generalizing
the Darcy’s law to non-Newtonian fluids is adopted, with the permeability coefficient being the only source of randomness.
The natural logarithm of the permeability is considered a spatially homogeneous and correlated Gaussian random field. Under
the ergodic hypothesis, an effective permeability is first derived for two limit 1-D flow geometries: flow parallel to permeability
variation (serial-type layers), and flow transverse to permeability variation (parallel-type layers). The effective permeability
of a 2-D or 3-D isotropic domain is conjectured to be a power average of 1-D results, generalizing results valid for Newtonian
fluids under the validity of Darcy’s law; the conjecture is validated comparing our results with previous literature findings.
The conjecture is then extended, allowing the exponents of the power averaging to be functions of the flow behavior index.
For Newtonian flow, novel expressions for the effective permeability reduce to those derived in the past. The effective permeability
is shown to be a function of flow dimensionality, domain heterogeneity, and flow behavior index. The impact of heterogeneity
is significant, especially for shear-thinning fluids with a low flow behavior index, which tend to exhibit channeling behavior. 相似文献
110.
Gianluca Vignaroli Claudio Faccenna Federico Rossetti 《International Journal of Earth Sciences》2009,98(5):1077-1093
Geological mapping coupled with structural investigations carried out in the Voltri Massif (eastern Ligurian Alps, Italy)
provide new data for the interpretation of the tectonic context controlling main fabric development during exhumation of its
high-pressure core. The Voltri Massif is here interpreted as a c. 30 km-long eclogite-bearing, asymmetric dome formed by the
progressive verticalisation of the regional, second-phase mylonitic foliation developed during retrogressive greenschist metamorphic
conditions. In this light, the exhumation history is driven by a ductile-to-brittle extensional process, operating through
low-angle, top-to-the-W multiple detachment systems. A Late Eocene–Early Oligocene age for this extensional episode is proposed
on the basis of structural correlations, stratigraphic and radiometric constraints. In this scenario, the Voltri Massif is
interpreted as an extensional domain developed to accommodate the Late Eocene–Early Oligocene arching of the Western Alps–Northern
Apennines orogenic system. 相似文献