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41.
A method for the analysis and classification of historic masonry 总被引:1,自引:1,他引:0
Antonio Borri Marco Corradi Giulio Castori Alessandro De Maria 《Bulletin of Earthquake Engineering》2015,13(9):2647-2665
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A numerical approach is presented for the ‘identification’ (or back calculation) of the earth pressure acting on embedded or retaining structures. The procedure is applicable to structures of any shape and requires a set of in situ measurements that may include displacements of points on the structure, values of concentrated forces, values of distributed loads at some locations, etc. Possible limiting values of the unknown loads, non-linear structural behaviour, varying accuracies of the input data are accounted for in the problem formulation. Depending upon the type of problem, the solution is reached by means of the unconstrained or constrained minimization of a suitably defined error function. As an example, the proposed approach is applied to the identification of the earth pressure acting on some typical geotechnical engineering structures. 相似文献
45.
Geophysical interpretation of a high-resolution seismic refraction profile in the Northern Apennines
Giancarlo Biella Roberto De Franco Martina Demartin Riccardo Barzaghi Fernando Sanso Domenico Sguerso 《地学学报》1994,6(1):45-53
A combined seismic and gravimetric interpretation in the Northern Apennines area (Italy) is presented. To the knowledge of the authors, this is one of the few attempts to apply tomographic methodology to a seismic refraction profile. This procedure, together with the classical interpretation for defining lower reflectors, led to the formulation of quite an accurate model of the upper crust. A gravity analysis was performed concurrently taking into account the seismic results at different depths which correspond to different frequency domains in the gravity signal. While the medium- and high-frequency patterns have been solved by trial-and-error, the regional trend has been modelled applying the collocation procedure to the gravity data. 相似文献
46.
Giorgio Rivalenti Maurizio Mazzucchelli Vicente Antonio Vitorio Girardi Giancarlo Cavazzini Cristina Finatti Maria Adelaide Barbieri Wilson Teixeira 《Lithos》1998,43(4):235-265
Paleoproterozoic basaltic, andesitic and rhyolitic dykes crosscut the Archaean Carajás basement. Basalts are distinguished into a high and a low TiO2 group (HTi and LTi), each group consisting of geochemically distinct NE- and NW-trending swarms. The HTi dykes are evolved transitional basalts having essentially EMORB-type geochemistry. The LTi basalts are tholeiites (NE-trending swarm) and high-Al basalts (NW-trending swarm) displaying incompatible trace elements patterns with variably negative Nb anomaly, enrichment in Rb, Ba, K (LILE) and La, Ce and Nd (LREE) and positive Sr anomaly. With respect to orogenic analogues, andesites have lower Al2O3, CaO and Ni, higher FeO, LILE, LREE, Nb, Zr and Ti and negative Sr anomaly. Rhyolites have geochemical characteristics comparable with those of A-type granites. At 1.8 Ga,
ranges from 0.700 to 0.705 in the HTi basalts and from 0.700 to 0.704 in the LTi group. Andesites define an isochron of 1874±110 Ma (Sro=0.7038±0.0010). Rhyolites from Southern and Northern Carajás define two isochrons of 1802±130 Ma (Sro=0.7062±0.0046) and 1535±82 Ga (Sro=0.7625) respectively, the younger date being interpreted as resetting of the Rb–Sr isotopic system. We propose a petrogenetic model relating LTi basalts with melting of lithospheric mantle metasomatized by acid melts derived from incipient melting of eclogites, representing in turn the subsolidus product of basaltic batches trapped in the mantle. The HTi basalts are explained by melting of the lithospheric mantle containing the complementary residual eclogite. Andesite petrogenesis is consistent with crystal fractionation from a high-Mg andesite parent derived from a mantle source more extensively metasomatized by eclogite-derived melts. Rhyolite composition is consistent with low melting degree of the basement rocks. The basalt–andesite–rhyolite dykes may represent the effects of crustal extension and arching in Carajás, which produced the anorogenic acid to intermediate magmatism (Uatumã group) and affecting a large part of the Amazon craton between 1.85 and 1.7 Ga. 相似文献
47.
Stefano Schiaparelli Giancarlo Albertelli & Riccardo Cattaneo-Vietti 《Marine Ecology》2006,27(1):44-53
Some organisms represent useful Biological Sea‐Level Indicators (Bio SLI) thanks to their constant position relative to sea level and allow the reconstruction of past sea level changes. The sessile gastropods Vermetidae are among the most used indicators, since their shells often resist time averaging and can be easily dated with 14C. However, all these vermetids have a level of precision (± 0.5–1 m), obtained from data on the Mediterranean Dendropoma petraeum (Monterosato, 1884). We found a certain degree of plasticity in this species; it can also live subtidally, not in correspondence with the main sea level, where it feeds adopting a mixed feeding strategy. Considering this variability and the almost complete lack of knowledge for other Bio SLI vermetids, it appears clear that a common value of precision cannot be maintained and the precision of other vermetid species remains to be tested. 相似文献
48.
Riccardo Cattaneo-Vietti Giancarlo Albertelli Giorgio Bavestrello Carlo Nike Bianchi Carlo Cerrano Mariachiara Chiantore Laura Gaggero Carla Morri Stefano Schiaparelli 《Marine Ecology》2002,23(S1):65-77
Abstract. Biomineralogy, as the complex of interactions at different levels (cell, organism, species, and community) between organisms and minerals, may play a significant role in the spatial distribution and structure of marine communities. For instance, a negative influence of quartz has been underlined on the Mediterranean benthic communities, which show a species-poorer structure in quartz-rich environments. Excluding the role of quartz, the aim of this work is to verify whether the composition of various mineralogical substrata can affect a hard-bottom benthic community. In the Ligurian Sea, the Levanto area shows an astonishing complex of substrata with different petrographic characters: in a few kilometres, sandstones, serpentinites, gabbros, and basalts occur in geometric association. Consequently, this area represents a suitable frame for this type of study. Herein, algal photophilic assemblages growing on the four mineralogical substrata show significant differences in number of species and percentage cover or abundance. This suggests a significant influence of rock mineral composition on the hard bottom community. Therefore, rock composition must be taken into account for a better understanding of the processes at the basis of hard-bottom community development and diversity. 相似文献
49.
Geomorphic features extraction from high-resolution topography: landslide crowns and bank erosion 总被引:5,自引:0,他引:5
In recent years, new remote-sensed technologies, such as airborne and terrestrial laser scanner, have improved the detail
and the quality of topographic information, providing topographical high-resolution and high-quality data over larger areas
better than other technologies. A new generation of high-resolution (≤3 m) digital terrain models (DTMs) is now available
for different areas and is widely used by researchers, offering new opportunities for the scientific community. These data
call for the development of a new generation of methodologies for an objective extraction of geomorphic features, such as
channel heads, channel networks, bank geometry, debris-flow channel, debris-flow deposits, scree slope, landslide and erosion
scars, etc. A high-resolution DTM is able to detect the divergence/convergence of areas related to unchannelized/channelized
processes with better detail than a coarse DTM. In this work, we tested the performance of new methodologies for an objective
extraction of geomorphic features related to shallow landsliding processes (landslide crowns), and bank erosion in a complex
mountainous terrain. Giving a procedure that automatically recognizes these geomorphic features can offer a strategic tool
to map natural hazard and to ease the planning and the assessment of alpine regions. The methodologies proposed are based
on the detection of thresholds derived by the statistical analysis of variability of landform curvature. The study was conducted
on an area located in the Eastern Italian Alps, where an accurate field survey on shallow landsliding, erosive channelized
processes, and a high-quality set of both terrestrial and airborne laser scanner elevation data is available. The analysis
was conducted using a high-resolution DTM and different smoothing factors for landform curvature calculation in order to test
the most suitable scale of curvature calculation for the recognition of the selected features. The results revealed that (1)
curvature calculation is strongly scale-dependent, and an appropriate scale for derivation of the local geometry has to be
selected according to the scale of the features to be detected; (2) such approach is useful to automatically detect and highlight
the location of shallow slope failures and bank erosion, and it can assist the interpreter/operator to correctly recognize
and delineate such phenomena. These results highlight opportunities but also challenges in fully automated methodologies for
geomorphic feature extraction and recognition. 相似文献
50.
Antigorite equation of state and anomalous softening at 6 GPa: an in situ single-crystal X-ray diffraction study 总被引:1,自引:0,他引:1
Fabrizio Nestola Ross J. Angel Jing Zhao Carlos J. Garrido Vicente López Sánchez-Vizcaíno Giancarlo Capitani Marcello Mellini 《Contributions to Mineralogy and Petrology》2010,160(1):33-43
The compressibility of antigorite has been determined up to 8.826(8) GPa, for the first time by single crystal X-ray diffraction in a diamond anvil cell, on a specimen from Cerro del Almirez. Fifteen pressure–volume data, up to 5.910(6) GPa, have been fit by a third-order Birch–Murnaghan equation of state, yielding V 0 = 2,914.07(23) Å3, K T0 = 62.9(4) GPa, with K′ = 6.1(2). The compression of antigorite is very anisotropic with axial compressibilities in the ratio 1.11:1.00:3.22 along a, b and c, respectively. The new equation of state leads to an estimation of the upper stability limit of antigorite that is intermediate with respect to existing values, and in better agreement with experiments. At pressures in excess of 6 GPa antigorite displays a significant volume softening that may be relevant for very cold subducting slabs. 相似文献