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91.
The paper presents advances in the discrete element modelling of underground excavation processes extending modelling possibilities
as well as increasing computational efficiency. Efficient numerical models have been obtained using techniques of parallel
computing and coupling the discrete element method with finite element method. The discrete element algorithm has been applied
to simulation of different excavation processes, using different tools, TBMs and roadheaders. Numerical examples of tunnelling
process are included in the paper, showing results in the form of rock failure, damage in the material, cutting forces and
tool wear. Efficiency of the code for solving large scale geomechanical problems is also shown. 相似文献
92.
Benthic Community and Sediment Types: A Structural Analysis 总被引:2,自引:0,他引:2
Eugenio Fresi Maria Cristina Gambi Silvano Focardi Roberto Bargagli Franco Baldi Lucia Falciai 《Marine Ecology》1983,4(2):101-121
Abstract. The distribution of the macrobenthic community, in relation to various physical and chemical characteristics of the sediment, was studied along the coast of Southern Tuscany (Central Tyrrhenian) in an area under the influence of the Ombrone River outflow.
The zonation of the benthos was found to be primarily under the control of a gradient of water movement, as is reflected by variations in the sediment structure from the coast to the open sea. This correlation is somehow influenced by secondary gradients such as the degree of mixing of the sediment and the deposition of terrigenous materials along the river plume. 相似文献
The zonation of the benthos was found to be primarily under the control of a gradient of water movement, as is reflected by variations in the sediment structure from the coast to the open sea. This correlation is somehow influenced by secondary gradients such as the degree of mixing of the sediment and the deposition of terrigenous materials along the river plume. 相似文献
93.
Rita Colognola Pietro Masturzo Giovanni Fulvio Russo Mlchele Scardi Daniele Vlnci Eugenio Fresi 《Marine Ecology》1986,7(3):265-285
Abstract. Two forms of Rissoa auriscalpium were found in Posidonia oceanica beds around the Island of Ischia (Gulf of Naples). In order to investigate their taxonomical value and to quantify the discriminating features found, the radular, conchometric, genetic, and ecological features of the two forms were analyzed. Ecological observations showed that the distribution of the two forms is strongly correlated with hydrodynamic factors. 相似文献
94.
Wang Liang Zhang Xue Zaniboni Filippo Oñate Eugenio Tinti Stefano 《Mathematical Geosciences》2021,53(1):81-103
Mathematical Geosciences - Notwithstanding its complexity in terms of numerical implementation and limitations in coping with problems involving extreme deformation, the finite element method (FEM)... 相似文献
95.
At Mt. Etna volcano, the emission of plagioclase megacryst-bearing lavas, known locally as “cicirara”, has occurred rarely
and generally in association with unusual volcanological phenomena. In this work, we interpret the magma chamber processes
and the structural features of the plumbing system that led to the production of these peculiar volcanic rocks, based on a
detailed study of plagioclase megacrysts, including their oscillatory zoning, sieve textures, and fluid inclusions. Patchy
zoning suggests limited ascent in the deep levels of the plumbing system, based on the plagioclase nucleation threshold and
the volatile saturation depth. At intermediate, water-undersaturated levels of the plumbing system ascent is faster, as indicated
by crystals with coarse sieve textures. Storage at shallow, water-saturated levels (less than 6 km deep) is associated with
oscillatory zoning with very small changes in An. Slightly larger An variations coupled with different wavelengths provide
evidence of convection of crystals across distinct zones of the chamber. Stripes of melt inclusions formed at steps of magma
ascent and volatile loss, whereas layers of fluid inclusions may be related to episodes of volatile flushing into the magma
chamber. In contrast, strongly sieve-textured envelopes with An increase and constant FeO may be related to mixing with more
volatile-rich magmas of similar composition. We interpret the repeated occurrence of “cicirara” lavas as evidence that the
shallow portion of the plumbing system underwent a progressive coalescence of a complex network of dykes and sills in response
to increasing rates of magma supply from depth. Major magma withdrawals from this larger reservoir may be linked to episodes
of summit instability associated with major caldera collapses. 相似文献
96.
The Karhunen–Loéve (K–L) method is used to interpret dynamic response data obtained from shaking table and pseudodynamic tests conducted on civil engineering structures subjected to earthquake loading. It is shown how the K–L method can be used to monitor on‐line, or a posteriori, the structural response of non‐linear dynamical systems. Results from these analyses make it possible to quantitatively verify the number and participation factors of non‐linear modes and how they correspond to physical behaviour of the structure. Comments are made regarding the use of this technique in various fields including numerical calculations, experiments and control. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
97.
Coupled use of carbon isotopes and noble gas isotopes in the Potiguar basin (Brazil): Fluids migration and mantle influence 总被引:1,自引:0,他引:1
We used the carbon isotope ratios of hydrocarbons and CO2, and the proportions of noble gas isotopes of associated gases from several geological provinces of the Potiguar Basin (Brazil) for gas/source rock correlation, and to determine maturity, post-genetic processes (migration, leakage, biodegradation), and to assess the possible interactions between hydrocarbons and surrounding waters. Barriers of permeability at the basin scale, the amount of water interacting with the accumulated hydrocarbons, proportion of meteoric water, and contamination of the fluids by the mantle were quantified for the distinct petroleum systems defined in this basin. 相似文献
98.
Late Cenozoic brittle deformation in the Southern Patagonian Andes: Record of plate coupling/decoupling during variable subduction?
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Vanesa Barberón Christian Sue Matías Ghiglione Gonzalo Ronda Eugenio Aragón 《地学学报》2018,30(4):296-309
The Andes of southern Patagonia experienced a Miocene shift towards faster and higher angle subduction followed by the approach and collision of the Chile oceanic ridge. We present a kinematic study characterizing palaeostress fields computed from brittle tectonics to better constrain upper crustal deformation during this complex scenario. Although previous studies already suggested variable kinematics, it is striking that in a long‐lasting subduction environment, the computed palaeostress tensors are mostly strike‐slip (55%), while 35% are extensional, and only 10% compressive which are concentrated along a main frontal thrust. Cross‐cutting relationships and synsedimentary deformation indicate that a long‐lived strike‐slip regime was punctuated by a lower Miocene extensional event in the foreland before the main compressional event. The results are discussed in contrasting geodynamic models of plate coupling/decoupling versus direction and rate of convergence of the subducting plate, to explain the main mechanisms that control back‐arc deformation. 相似文献
99.
Aguiar Eva Mourre Baptiste Juza Mélanie Reyes Emma Hernández-Lasheras Jaime Cutolo Eugenio Mason Evan Tintoré Joaquín 《Ocean Dynamics》2020,70(2):273-288
Ocean Dynamics - In numerical ocean modeling, dynamical downscaling is the approach consisting in generating high-resolution regional simulations exploiting the information from coarser resolution... 相似文献
100.
Anabella Medina Machín Javier Marcello Antonio I. Hernández-Cordero Javier Martín Abasolo Francisco Eugenio 《地理信息系统科学与遥感》2019,56(2):210-232
Vegetation mapping is a priority when managing natural protected areas. In this context, very high resolution satellite remote sensing data can be fundamental in providing accurate vegetation cartography at species level. In this work, a complete processing methodology has been developed and validated in a complex vulnerable coastal-dune ecosystem. Specifically, the analysis has been carried out using WorldView-2 imagery, which offers spatial and spectral resolutions. A thorough assessment of 5 atmospheric correction models has been performed using real reflectance measures from a field radiometry campaign. To select the classification methodology, different strategies have been evaluated, including additional spectral (23 vegetation indices) and spatial (4 texture parameters) information to the multispectral bands. Likewise, the application of linear unmixing techniques has been tested and abundance maps of each plant species have been generated using the library of spectral signatures recorded during the campaign. After the analysis conducted, a new methodology has been proposed based on the use of the 6S atmospheric model and the Support Vector Machine classification algorithm applied to a combination of different spectral and spatial input data. Specifically, an overall accuracy of 88,03% was achieved combining the corrected multispectral bands plus a vegetation index (MSAVI2) and texture information (variance of the first principal component). Furthermore, the methodology has been validated by photointerpretation and 3 plant species achieve significant accuracy: Tamarix canariensis (94,9%), Juncus acutus (85,7%) and Launaea arborescens (62,4%). Finally, the classified procedure comparing maps for different seasons has also shown robustness to changes in the phenological state of the vegetation. 相似文献