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71.
Understanding the formation and the development of salt structures is very important especially because they are of significant economical interest for hydrocarbon trapping and for long-term storage of radioactive waste and energy reserves. Generally, the activity of normal faults developed in extensional regimes is considered the most efficient mechanism for salt diapirs. The results of analogue models reported in this paper suggest a new triggering mechanism for the rise of salt structures during basin inversion. This mechanism relates the localization of ductile diapirs to early normal faults only after their inversion during later shortening. In this case, diapiric growth is related to the strong dip-slip reactivation component along the fault extruding the silicone-simulating salt upward. Some natural cases, in which the timing and the mechanism of diapiric growth is not clear, can be re-interpreted in the light of these analogue model results. 相似文献
72.
The design and the management of pump-and-treat (PAT) remediation systems for contaminated aquifers under uncertain hydrogeological settings and parameters often involve decisions that trade off cost optimality against reliability. Both design objectives can be improved by planning site characterization programs that reduce subsurface parameter uncertainty. However, the cost for subsurface investigation often weighs heavily upon the budget of the remedial action and must thus be taken into account in the trade-off analysis. In this paper, we develop a stochastic data-worth framework with the purpose of estimating the economic opportunity of subsurface investigation programs. Since the spatial distribution of hydraulic conductivity is most often the major source of uncertainty, we focus on the direct sampling of hydraulic conductivity at prescribed locations of the aquifer. The data worth of hydraulic conductivity measurements is estimated from the reduction of the overall management cost ensuing from the reduction in parameter uncertainty obtained from sampling. The overall cost is estimated as the expected value of the cost of installing and operating the PAT system plus penalties incurred due to violations of cleanup goals and constraints. The crucial point of the data-worth framework is represented by the so-called pre-posterior analysis. Here, the tradeoff between decreasing overall costs and increasing site-investigation budgets is assessed to determine a management strategy proposed on the basis of the information available at the start of remediation. The goal of the pre-posterior analysis is to indicate whether the proposed management strategy should be implemented as is, or re-designed on the basis of additional data collected with a particular site-investigation program. The study indicates that the value of information is ultimately related to the estimates of cleanup target violations and decision makers’ degree of risk-aversion. 相似文献
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75.
Salvatore de Lorenzo Elisabetta Giampiccolo Carmen Martinez-Arevalo Domenico Patanè Annalisa Romeo 《Journal of Volcanology and Geothermal Research》2010,189(3-4):247-256
A crucial point in the analysis of tectonic earthquakes occurring in a volcanic area is the inference of the orientation of the structures along which the ruptures occur. These structures represent zones of weakness which could favor the migration of melt toward the surface and the assessment of their geometry is a fundamental step toward efficient evaluation of volcanic risk. We analyzed a high-quality dataset of 171 low-magnitude, tectonic earthquakes that occurred at Mt. Etna during the 2002–2003 eruption. We applied a recently developed technique aimed at inferring the source parameters (source size, dip and strike fault) and the intrinsic quality factor Qp of P waves from the inversion of rise times. The technique is based on numerically calibrated relationships among the rise time of first P waves and the source parameters for a circular crack rupturing at a constant velocity. For the most of the events the directivity source effect did not allow us to constrain the fault plane orientation. For a subset of 45 events with well constrained focal mechanisms we were able to constrain the “true” fault plane orientation. The level of resolution of the fault planes was assessed through a non linear analysis based on the random deviates technique. The significance of the retrieved fault plane solutions and the fit of the assumed source model to data were assessed through a χ-square test. Most of the retrieved fault plane solutions agree with the geometrical trend of known surface faults. The inferred source parameters and Qp are in agreement with the results of previous studies. 相似文献
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77.
Thi Minh Hue Le Marcelo Sánchez Domenico Gallipoli Simon Wheeler 《Geomechanics and Geoengineering》2015,10(2):95-108
Spatial variability of soil materials has long been recognised as an important factor influencing the reliability of geo-structures. This study stochastically investigates the influence of spatial variability of shear strength on the stability of heterogeneous slopes, focusing on the auto-correlation function, auto-correlation distance and cross-correlation between soil parameters. The finite element method is merged with the random field theory to probabilistically evaluate factor of safety and probability of failure via Monte-Carlo simulations. The simulation procedure is explained in detail with suggestions on improving efficiency of the Monte-Carlo process. A simple procedure to create cross-correlation between random variables, which allows direct comparison of the influence of each strength variable, is discussed. The results show that the auto-correlation distance and cross-correlation can significantly influence slope stability, while the choice of auto-correlation function only has a minor effect. An equation relating the probability of failure with the auto-correlation distance is suggested in light of the analyses performed in this work and other results from the literature. 相似文献
78.
Domenico Pileggi David Rossi Enrico Lunedei Dario Albarello 《Bulletin of Earthquake Engineering》2011,9(6):1839-1854
The problem of seismic characterization of rock-mass or stiff-soil outcrops by the use of passive seismic prospecting techniques
is discussed. Difficulties in the application of this kind of procedure in the presence of rugged morphology, high surface
wave velocities and low ambient vibration powers, typical of stiff-soil/rock-mass sites are examined. A methodology to face
these problems is here proposed, which is based on the strict synergy of detailed geologic surveys and application of robust
seismic prospecting techniques, jointly considering single-station and multi-station tools. The application of this approach
for the characterization of a number of sites belonging to the Italian Accelerometric Network is described, focusing on two
representative case histories. 相似文献
79.
Sebastiano Imposa Francesco Barone Domenico Bella Massimo Cristaldi Stefano Gresta 《Environmental Earth Sciences》2011,64(7):1777-1786
A “standard procedure” to characterize the seismic hazard of a given area was proposed. It is based on a multidisciplinary
approach implying: (1) the knowledge of the seismic history of the area; (2) detailed geological surveys; (3)seismic noise
measurements; (4) simulations of earthquake scenarios. The downtown of Acireale, a typical baroque town located on Eastern
Sicily, was chosen as the “test area”. A catalog of the local seismogenic faults (able to generate earthquakes in historical
times) has been compiled, as well as a seismic catalog for the effects of both local and regional earthquakes. The analysis
of both catalogs allowed us to make the following conclusions: (1) the most important seismogenic faults affecting the Acireale
municipality do not affect the downtown, while the related local earthquakes attenuate their energy (and intensity) in short
(few km) distances; (2) the highest seismic intensity (degree X) experienced in Acireale downtown was caused by the 1693 regional earthquake; (3) over the last 140 years, the downtown has
experienced the highest intensity value of VII only once, while six times the intensity was VI. On the whole, this implies
a moderate seismic hazard. The estimation of the seismic hazard has been also approached by the experimental method of recording
seismic noise. Measurements have been performed at seven different sites, where drills gave detailed information on the shallow
subsurface geology to obtain HV (horizontal/vertical) spectral ratios. On the whole, the highest site amplification factor
was moderate (about 7). A further investigation based on synthetic seismograms (and spectra) produced by simulating two given
earthquake scenarios was also performed. The two scenarios are, respectively, representative of the largest expected earthquake
in the area (the 1693 shock) and of a moderate (magnitude ca. 5.5) local earthquake (as the 1818 one). Moderate to strong
locally expected accelerations were evidenced. 相似文献
80.
Andrea Cattaneo Andrea Rossotti Giorgio Pasquarè Anna Somigliana Domenico M. Cavallo 《Environmental Earth Sciences》2011,63(4):861-871
Since Etrurian age, the Viterbo Province (Central Italy) is famous for its ancient towns carved out of local ignimbrite deposits
which geologically represent the sedimentation of pumice-rich, volcano-related pyroclastic flows. Almost the entire study
area is geologically characterized by a thick succession of ignimbrites, tephra fallouts and lava flow deposits locally subjected
to zeolitization. Among zeolites, fibrous erionite represents a well-known health hazard and so this work aims at locating
and quantifying the presence of fibrous zeolites in volcanic deposits of the Viterbo area, suggesting at the same time a standard
operational procedure useful in other areas showing the same possible hazard. 41 samples collected in the Viterbo area were
analyzed by X-ray powder diffraction, optical and electron microscopy. Fibrous zeolites were detected in five samples and
quantified in amounts ranging from 0.35 to 1.66% vol. They generally occur in tetragonal or orthorhombic prismatic habit and
showed chemical composition mainly consistent with K-phillipsite. Fibrous zeolites occurred with aspect ratios (mean = 6.3),
comparable or lower than those of erionite fibers reported in previous studies and mean diameters >3 μm. 相似文献