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171.
Detailed analysis of the morphology of Bacino Bannock, a deep-sea basin filled by a hypersaline brine, shows with unusual
detail the effect on the ocean floor topography of the deformation and dissolution of a salt body under tectonic stress. Although
salt diapirism occurs in the central part of the investigated area, the major cause of basin formation is dissolution of subsurface
evaporites which creates negative relief that exceeds by about one order of magnitude the positive relief. The true shape
of the deformed salt deposit is preserved as a result of the absence of a thick post-evaporites sedimentary cover. 相似文献
172.
Ana María Sato Hugo Tickyj Eduardo Jorge Llambías Miguel Angelo Stipp Basei Pablo Diego Gonzlez 《Gondwana Research》2004,7(4):1077-1087
The Las Matras Block in Central Argentina constitutes the southernmost part of the Cuyania terrane, which was accreted to the southwestern margin of Gondwana during the Early to Mid Ordovician Famatinian orogeny. The Grenville-aged rocks of the Las Matras Block are represented by the tonalitic to trondhjemitic Las Matras pluton. A new U-Pb conventional zircon age of 1244±42 Ma confirms previous Sm-Nd and Rb-Sr isochron ages of this pluton. Mineral composition data are consistent with the tonalitic-trondhjemitic character of the pluton, and constrain its emplacement level to 1.9 to 2.6 kb. This shallow level of emplacement and the undeformed character of the pluton are distinctive features of this southernmost basement. A regional comparison indicates that the igneous-metamorphic evolution of the Grenville-aged basement rocks of the Cuyania terrane occurred over a period of more than 200 million years, with ages older than 1200 Ma up to those close to 1000 Ma. The shallowest crustal level is found in Las Matras, suggesting a southward shallowing of the exposed level of basement. The deformation and metamorphism associated with the collisional Famatinian orogeny affect both the Cuyania terrane and the adjacent western margin of Gondwana, and the Gondwana margin was also the locus of the related arc magmatism, but the compressive effects of the collision decrease in intensity toward the south. The Famatinian metamorphism and magmatism continue even further south into the Patagonia region, but the southern continuity of the Cuyania terrane into this region remains uncertain. 相似文献
173.
Marco Murru Concetta Ferrara Stefania Da Pelo Angelo Ibba 《Comptes Rendus Geoscience》2003,335(2):227-238
The Palaeocene of southern Sardinia includes a continental ferruginous sedimentation, with a high content of Al and Fe, indicative of a subhumid tropical climate. The subsequent microcodium carbonated detrital microcodium levels, containing an abundant quartzose fraction, rather suggest semiarid conditions. In SW Sardinia, the marine deposits, referred to Late Thanetian–Lower Ypresian (=Ilerdian) times, are limestones including larger foraminifers and contain significant amounts of quartz. A lower content of detrital kaolinite points a sediment source from the surrounding areas with a semiarid climate. The occurrence, at the top of this unit, of small trochospiral rotaliids and larger amount of detrital kaolinite suggests a transition to a rainy tropical climate in the adjacent areas. These limestones pass gradually to carbonate sediments characterized by large amounts of detrital kaolinite and intercalated coal layers, with pollen of tropical palms, attributed to the Late Ypresian (=Cuisian)–Early Lutetian and referred to a humid-subhumid tropical climate. 相似文献
174.
175.
Within observational accuracy, the radiation pressure 1/3aT
4 at the effective solar temperature is equal to the coronal gas pressurenkT. This suggests a radiative-gas discontinuity between optically thick and optically thin regions. Ideal transitions of this nature are studied and the applicability of this model to the Sun is explored. Further empirical corroboration is obtained if the gas pressure anomalies of Gulyaev are resolved by postulating a corrective gradient of radiation pressure possibly caused by Lyman- opacity. 相似文献
176.
177.
178.
Angelo Camerlenghi Daniela Accettella Sergio Costa Galderic Lastras Juan Acosta Miquel Canals Nigel Wardell 《International Journal of Earth Sciences》2009,98(4):735-750
We present the seafloor morphology and shallow seismic structure of the continental slope south-east of the Balearic promontory
and of the adjacent Algero-Balearic abyssal plain from multibeam and chirp sonar data. The main purpose of this research was
to identify the sediment pathways from the Balearic promontory to the Algero-Balearic deep basin from the Early Pliocene to
the Present. The morphology of the southern Balearic margin is controlled by a SW–NE structural trend, whose main expressions
are the Emile Baudot Escarpment transform fault, and a newly discovered WSW–ENE trend that affects the SW end of the escarpment
and the abyssal plain. We relate the two structural trends to right-lateral simple shear as a consequence of the Miocene westward
migration of the Gibraltar Arc. Newly discovered steep and narrow volcanic ridges were probably enabled to grow by local transtension
along the transform margin. Abyssal plain knolls and seahills relate to the subsurface deformation of early stage halokinetic
structures such as salt rollers, salt anticlines, and salt pillows. The limited thickness of the overburden and the limited
amount of deformation in the deep basin prevent the formation of more mature halokinetic structures such as diapirs, salt
walls, bulbs, and salt extrusions. The uppermost sediment cover is affected by a dense pattern of sub-vertical small throw
normal faults resulting from extensional stress induced in the overburden by subsurface salt deformation structures. Shallow
gas seismic character and the possible presence of an active polygonal fault system suggest upward fluid migration and fluid
and sediment expulsion at the seafloor through a probable mud volcano and other piercement structures. One large debris flow
deposit, named Formentera Debris Flow, has been identified on the lower slope and rise of the south Formentera margin. Based
on current observations, we hypothesize that the landslide originating the Formentera Debris Flow occurred in the Holocene,
perhaps in historical times.
相似文献
Angelo CamerlenghiEmail: |
179.
Building damage scenarios based on exploitation of Housner intensity derived from finite faults ground motion simulations 总被引:2,自引:2,他引:0
Leonardo Chiauzzi Angelo Masi Marco Mucciarelli Marco Vona Francesca Pacor Giovanna Cultrera Frantisek Gallovič Antonio Emolo 《Bulletin of Earthquake Engineering》2012,10(2):517-545
In this paper earthquake damage scenarios for residential buildings (about 4200 units) in Potenza (Southern Italy) have been
estimated adopting a novel probabilistic approach that involves complex source models, site effects, building vulnerability
assessment and damage estimation through Damage Probability Matrices. Several causative faults of single seismic events, with
magnitude up to 7, are known to be close to the town. A seismic hazard approach based on finite faults ground motion simulation
techniques has been used to identify the sources producing the maximum expected ground motion at Potenza and to generate a
set of ground motion time histories to be adopted for building damage scenarios. Additionally, site effects, evaluated in
a previous work through amplification factors of Housner intensity, have been combined with the bedrock values provided by
hazard assessment. Furthermore, a new relationship between Housner and EMS-98 macroseismic intensity has been developed. This
relationship has been used to convert the probability mass functions of Housner intensity obtained from synthetic seismograms
amplified by the site effects coefficients into probability mass function of EMS-98 intensity. Finally, the Damage Probability
Matrices have been applied to estimate the damage levels of the residential buildings located in the urban area of Potenza.
The proposed methodology returns the full probabilistic distribution of expected damage, thus avoiding average damage index
or uncertainties expressed in term of dispersion indexes. 相似文献
180.