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2.
Trends in biomass, density and diversity of North Sea macrofauna 总被引:6,自引:2,他引:6
3.
Methane-rich fluid inclusions in skarn near the giant REE–Nb–Fe deposit at Bayan Obo, Northern China
We report fluid inclusion data for skarn, formed at the contact between Hercynian granitoids and dolomite of the Proterozoic Bayan Obo Group, in the vicinity of Bayan Obo REE–Nb–Fe deposit, Inner Mongolia, China. Three types of fluid inclusions are identified: two-phase CH4-rich, three-phase liquid–vapour–solid and two-phase aqueous inclusions. Using microthermometry and laser Raman microprobe analysis to calculate isochores for CH4-bearing inclusions, we estimate fluid trapping conditions at T=280 to 344 °C and P<1 to 2.3 kbar. Such conditions are compatible with formation of CH4 inclusions as a result of reaction between graphite in the country rocks (black slate sequence) and fluids derived from magma. The lack of carbonaceous material in the inclusions supports the hypothesis that CH4 was generated during fluid migration rather than by in situ reaction. In contrast to the skarn, and despite the fact that similar graphite-bearing slates are found in the host rocks, no CH4-bearing inclusions have been so far reported from Bayan Obo REE ores. We therefore conclude that the skarn-forming fluids in the contact aureole of the Hercynian granitoids were not involved at any stage in the formation of the Bayan Obo deposit. 相似文献
4.
Fu-yuan Wu Simon A. Wilde Guang-liang Zhang De-you Sun 《Journal of Asian Earth Sciences》2004,23(5):781
Northeastern (NE) China is a well-documented example of a collisional zone characterized by widespread post-orogenic granites and mafic–ultramafic complexes. Based on a study of the Hongqiling and Piaohechuan Cu–Ni sulfide-bearing mafic–ultramafic complexes in central Jilin province, we present geological, petrological, geochemical and geochronological data which indicates their post-orogenic origin.The Hongqiling complex comprises pyroxenite, olivine websterite, lherzolite, gabbro and leucogabbro. Zircon U–Pb SHRIMP analyses on a leucogabbro of the Hongqiling complex yield a weighted mean 206Pb–238U age of 216±5 Ma. The Piaohechuan complex is composed of gabbro, pyroxenite and dolerite, exposed as dikes. A plagioclase-bearing pyroxenite has a U–Pb zircon weighted mean 206Pb–238U age of 217±3 Ma, identical to that of the Hongqiling complex. These ages are coeval with the emplacement of A-type granites in the area, but slightly younger than the regional metamorphism (240 Ma) and syn-orogenic granitic magmatism (246±4 Ma). This suggests that these mafic–ultramafic complexes are post-orogenic in origin. The age data also indicated a short period of lithospheric stabilization of about 30 Ma after cessation of orogenic activity.Geochemical investigation indicates that the primary mafic magma was a lithospheric mantle-derived basalt resulting from the upwelling of asthenosphere due to lithospheric delamination during post-orogenic processes. The magmatic source was contaminated by a small amount of crustal material, and subsequent crystal fractionation resulted in the Cu–Ni mineralization.The widespread occurrence of mafic–ultramafic complexes in the Xing'an–Mongolian Orogenic Belt of NE China and in the Altay–Tianshan–Junggar Orogenic Belt of Northern Xinjiang indicates that mafic intrusions are an important magmatic suite that evolved during post-orogenic processes. Portions of this mafic magma could have underplated the lower crust, and served as the heat source for associated late-stage granitic magmas. 相似文献
5.
Future mineral exploration within eastern Australia will be enhanced by resolving the tectonic evolution of the Lachlan Orogen
to establish the spatial and temporal terrane distribution of the various mineral deposits. The Lachlan Orogen, from north-eastern
Tasmania through to central and eastern New South Wales, is host to a number of major mineral deposit styles—including orogenic
gold (e.g. Stawell, Ballarat, Bendigo), volcanic-hosted massive sulphide (e.g. Woodlawn, Currawong), sediment-hosted Cu–Au
(e.g. Cobar Basin deposits), porphyry Au–Cu (e.g. Cadia, Parkes, Cowal) and granite-related Sn (e.g. Ardlethan, Beechworth).
Each of these mineral deposit styles is a sensitive and diagnostic indicator of the prevalent tectonic environment during
their formation. In this review, we briefly summarise the deposit- to large-scale factors that define the diverse metallogenic
evolution of the Lachlan Orogen. This overview is intended to “set the scene” for subsequent specialist papers published in
this thematic issue on the metallogeny and tectonics of the Lachlan Orogen in south-east Australia. 相似文献
6.
7.
Vernikovskaya A. E. Vernikovsky V. A. Matushkin N. Yu. Kadilnikov P. I. Metelkin D. V. Li Z.-X. Wilde S. A. Romanova I. V. Bogdanov E. A. 《Doklady Earth Sciences》2019,489(1):1285-1288
Doklady Earth Sciences - An Ediacaran complex of dike rocks has been identified for the first time in the Yenisei Ridge orogen. These igneous rocks are represented by basic, intermediate and acidic... 相似文献
8.
Tectonothermal history of the basement rocks in the western zone of the North China Craton and its tectonic implications 总被引:47,自引:0,他引:47
The basement of the North China Craton can be divided into the eastern, central and western zones, based on lithological, structural, metamorphic and geochronological data. The western zone comprises two different petrotectonic units: Archaean tonalitic–trondhjemitic–granodioritic (TTG) grey gneisses and metamorphic mafic rocks, and Palaeoproterozoic khondalite series. The former is characterized by isobaric cooling (IBC)-type anticlockwise P–T paths in the north-northwestern part of the zone and near-isothermal decompression (ITD)-type clockwise P–T paths in the eastern part, adjacent to the central zone. On the other hand, the tectonothermal evolution of Palaeoproterozoic khondalite series rocks is characterized exclusively by nearly isothermal decompression following the peak of metamorphism and then cooling, defining clockwise P–T paths. The Archaean TTG gneisses and associated mafic rocks with anticlockwise metamorphic P–T paths reflects an origin related to underplating and intrusion of mantle-derived magmas which may be derived from mantle plumes. They represent a late Archaean continental block in the western part of the North China Craton. The Palaeoproterozoic khondalite series rocks represent passive continental margin deposits. They were metamorphosed and deformed in the late Palaeoproterozoic during the amalgamation of the western continental block with another continental block in the east part of the North China Craton. The ITD-type clockwise P–T–t paths of the Palaeoproterozoic khondalite series rocks record the tectonothermal histories of the collision of the western and eastern continental blocks which resulted in the final assembly of the North China Craton at c. 1800 Ma. 相似文献
9.
Pounding of adjacent superstructure segments in elevated bridges during severe earthquakes can result in significant structural damage. The aim of this paper is to analyse several methods of reduction of the negative effects of collisions induced by the seismic wave propagation effect. The analysis is conducted on a detailed three‐dimensional structural component model of an isolated highway bridge. The results show that the influence of pounding on the structural response is significant in the longitudinal direction of the bridge and significantly depends on the gap size between superstructure segments. The smallest response can be obtained for very small gap sizes and for gap sizes large enough to prevent pounding. Further analysis indicates that the bridge behaviour can be effectively improved by placing hard rubber bumpers between segments and by stiff linking the segments one with another. The experimental results show that, for the practical application of such connectors, shock transmission units can be used. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
10.
Thomas M. Kreuzer Martina Wilde Birgit Terhorst Bodo Damm 《Earth Science Informatics》2017,10(4):507-515
Landslide research requires consistent and widespread data. Many countries within the European Union have national landslide inventories to fulfill these demands for their respective research. However, those inventories were usually not intended to provide the technical basis for automated process and risk analyses during their design phase. The ongoing development of Germany’s national landslide database offers the opportunity to do this differently. This paper introduces a landslide inventory system called WISL suitable for data handling as well as for novel automated process and risk analyses on a national scale. WISL is designated to form the technical infrastructure for a German national database. Its core consists of an open source relational database management system (PostgreSQL), standardized input and registration methods as well as integrated analyses modules, which avoid large data movement and allow for rapid risk analyses. We present proof-of-concept results of endangered infrastructure related to automated risk mappings based on topography and proximity of active landslides. The use of open source software and the application of a standardized input and data acquisition system for experts, coupled with custom analysis modules, constitutes a step toward automated risk maps by a mere ‘button-press’. Future developments for the inventory lie in the field of refining and inventing analysis modules and collecting data, for which WISL provides a firm technical base. 相似文献