全文获取类型
收费全文 | 58篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 2篇 |
地球物理 | 4篇 |
地质学 | 37篇 |
海洋学 | 2篇 |
天文学 | 8篇 |
自然地理 | 5篇 |
出版年
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2012年 | 4篇 |
2011年 | 6篇 |
2010年 | 2篇 |
2009年 | 5篇 |
2008年 | 4篇 |
2007年 | 2篇 |
2006年 | 5篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1994年 | 2篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有60条查询结果,搜索用时 31 毫秒
51.
52.
Stephanie Koch Henning Schroeder Matthias Haeckel Christian Berndt Joerg Bialas Cord Papenberg Dirk Klaeschen Andreia Plaza-Faverola 《Geo-Marine Letters》2016,36(3):187-196
This study presents 2D seismic reflection data, seismic velocity analysis, as well as geochemical and isotopic porewater compositions from Opouawe Bank on New Zealand’s Hikurangi subduction margin, providing evidence for essentially pure methane gas seepage. The combination of geochemical information and seismic reflection images is an effective way to investigate the nature of gas migration beneath the seafloor, and to distinguish between water advection and gas ascent. The maximum source depth of the methane that migrates to the seep sites on Opouawe Bank is 1,500–2,100 m below seafloor, generated by low-temperature degradation of organic matter via microbial CO2 reduction. Seismic velocity analysis enabled identifying a zone of gas accumulation underneath the base of gas hydrate stability (BGHS) below the bank. Besides structurally controlled gas migration along conduits, gas migration also takes place along dipping strata across the BGHS. Gas migration on Opouawe Bank is influenced by anticlinal focusing and by several focusing levels within the gas hydrate stability zone. 相似文献
53.
54.
SLAWEK TULACZYK BARCLAY KAMB HERMANN F. ENGELHARDT 《Boreas: An International Journal of Quaternary Research》2001,30(2):101-114
Preconsolidation stress recorded in subglacial sediments provides important information about subglacial effective stresses. It is commonly used to reconstruct past effective stresses from sediments left after ice retreat. In this article, we use properties of sub‐ice‐stream till samples to estimate effective stresses beneath a modern West Antarctic ice stream. Two previous estimates of sub‐ice‐stream effective stress were derived for the Upstream B (UpB) area of Ice Stream B from shear wave velocities (50 ± 40 kPa, Blankenship et al 1987) and borehole water level measurements (63 ± 24 kPa, Engelhardt & Kamb 1997). However, geotechnical tests performed on samples of the UpB till have shown that if subjected to effective stress of 50–63 kPa this till would have significantly lower porosity (?0.32–0.35) and higher strength (?‐22–28 kPa) than it apparently has in situ (?0.4 and ?2kPa). We derive new estimates of sub‐ice‐stream effective stress using: (1) Casagrande's construction applied to the results of six confined uniaxial tests, and (2) a combination of void‐ratio data for 51 till samples and 3 experimentally constrained equations describing compressibility of the UpB till under normal consolidation, overconsolidation and in the critical state. Casagrande's method yields an upper bound on effective stress of 25 kPa for four till samples and values of 13, and 4.4kPa for two other samples. The void‐ratio approach gives 11.7 ± 2.6 (normal consolidation), 18.3 ± 4.4 (overconsolidation) and 2.0 ± 0.8 kPa (critical state). These new, lower estimates of effective stress are consistent with the low till strength that has been independently measured and inferred from recent theoretical ice‐stream models. Our interpretation of data on till void ratio in terms of sub‐ice‐stream effective stress means that we can qualitatively evaluate the nature of the vertical distribution of this stress in the UpB till layer. We infer that in the sampled top 3 m of till the effective‐stress distribution is non‐hydrostatic, probably close to lithostatic. The results may be useful in future modeling of ice‐stream behavior and may aid efforts to delineate paleo‐ice streams based on their geologic record. 相似文献
55.
Abstract— We analyzed the compositional profiles of coexisting orthopyroxenes and spinels in six diogenite samples from the Antarctic meteorite collection and used the data to constrain their thermal histories. The closure temperatures of Fe2+‐Mg exchange between spinel and orthopyroxene in these samples vary between ~630 and 830 °C. However, those in other diogenite samples, for which the compositional data are available in the literature, extend up to ~1125 °C. This wide range of closure temperatures suggests repeated excavation of the diogenites from their original sites over a long time interval during cooling. The orthopyroxene grains were found to be homogeneous in composition while two of the relatively large spinel grains in the samples Elephant Moraine (EET) 87530 and Thiel Mountains (TIL) 82410 showed compositional zoning near the rim. Modeling of the spinel zoning in TIL 82410 suggests that it developed during cooling under a regolith or ejecta blanket, possibly at a depth of ~80–120 m, and that the spinel composition was homogeneous at ~900 °C. A nonlinear cooling model in which the cooling rate is given by ηT(K)2, with η = 5.8 times 10?3 K?1Ma?1, leads to simulated retrograde zoning profile in spinel which match the observed profile in TIL 82410 very well. 相似文献
56.
57.
Salt and ice crystallisation in porous sandstones 总被引:1,自引:0,他引:1
Salt and ice crystallisation in the pore spaces causes major physical damage to natural building stones. The damaging effect
of these processes can be traced back to physically induced stress inside of the rock while crystallizing. The increasing
scientific research done during the past century has shown that there are numerous parameters that have an influence on the
weathering resulting from these processes. However, the working mechanisms of the stress development within the rock and its
material dependency are still subject to discussion. This article gives an overview of salt and ice weathering. Additionally,
laboratory results of various sandstones examined are presented. Salt crystallisation tests and freeze/thaw tests were done
to obtain information about how crystallisation weathering depends on material characteristics such as pore space, water transportation,
and mechanical features. Simultaneous measuring of the length alternating during the salt and ice crystallisation has revealed
detailed information on the development of crystal in the pore spaces as well as the development of stress. These findings
can help to understand the damaging mechanisms. 相似文献
58.
Using In Situ Trace-Element Determinations to Monitor Partial-Melting Processes in Metabasites 总被引:4,自引:0,他引:4
Peak metamorphism (800850°C, 810 kbar) inthe Harts Range Meta-Igneous Complex (Harts Range, central Australia)was associated with localized partial melting by the reactionhornblende + plagioclase + quartz + H2O = garnet + clinopyroxene+ titanite + melt. In situ trace-element determinations of prograde,peak and retrograde minerals in migmatitic metabasites and associatedtonalitic melts using laser-ablation ICPMS has allowedmonitoring of a range of partial-melting processes (melting,melt segregation and back-reaction between crystallizing meltand restitic minerals). Mass balance calculations indicate thattitanite is a major carrier of trace elements such as Ti, Nb,Ta, Sm, U and Th, and therefore may be an important accessoryphase to control the redistribution of these elements duringthe partial melting of amphibolites. Titanite preferentiallyincorporates Ta over Nb and, hence, residual titanite mightassist in the formation of melts with high Nb/Ta. The fact thatsingle minerals record different rare earth element (REE) patterns,from prograde to peak to retrograde conditions, demonstratesthat REE diffusion is not significant up to 800°C. Therefore,trace-element analysis in minerals can be a powerful tool toinvestigate high-grade metamorphic processes beyond the limitsgiven by major elements. KEY WORDS: Harts Range; laser-ablation ICPMS; metabasites; partial melting; trace elements 相似文献
59.
Cooling History and Exhumation of Lower-Crustal Granulite and Upper Mantle (Malenco, Eastern Central Alps) 总被引:8,自引:5,他引:3
The Braccia gabbro of Val Malenco, Italian Alps, intruded 275My ago during Early Permian lithospheric extension. The intrusiontook place along the crustmantle transition zone andcaused granulite metamorphism of lower-crustal and upper-mantlerocks. The magmatic crystallization of the gabbro was outlastedby ductile deformation, which is also observed in the otherrocks of the crustmantle transition. Two stages of retrogrademetamorphism followed. Mineral parageneses in garnetkyanitegneiss, metagabbro, and metaperidotite record a first stageof near-isobaric cooling under anhydrous conditions. The stabilizedcrustmantle transition then persisted over a period ofabout 50 My into the Late Triassic. Exhumation of the crustmantlecomplex began with the onset of continental rifting during EarlyJurassic. This stage of retrograde metamorphism is recordedby near-isothermal decompression and partial hydration of thegranulitic mineral assemblages. The whole crust-to-mantle complexwas then exposed in the Tethyan ocean near its Adriatic margin.The magmatic assemblage of the Braccia gabbro formed at 11·2GPa and 11501250°C. Microstructures show that thegabbroic rocks evolved from olivine gabbros through spinel togarnet granulite whereas the peridotites recrystallized withinthe spinel peridotite field and the pelitic granulites remainedin the stability field of kyanite. Such an evolution is characteristicof isobaric cooling after magmatic underplating. Granuliticmineral assemblages record cooling from 850°C to 650°Cwith decompression to 0·8 ± 0·1 GPa, anddP/dT < 相似文献
60.
Prof. C. B. Gregor Prof. Dr. Alan E. M. Nairn Dr. Joerg F. W. Negendank 《International Journal of Earth Sciences》1975,64(1):948-958
A sampling of Plio-Pleistocene and Upper Cretaceous basalts in SE Sicily yielded the following informationAssuming that the Cretaceous direction is reversed, the confidence oval for the virtual pole overlaps that for the Cretaceous pole of Africa determined from the Mlanje Syenite byMcElhinny et al. If SE Sicily was attached to Africa when these Upper Cretaceous lavas erupted, this result implies that extensive relative movement between the two is not likely to have occurred subsequently.
Zusammenfassung Die Aufsammlung und Untersuchung plio-pleistozäner und oberkretazischer Basalte in SE-Sizilien ergab die folgende paläomagnetische InformationUnter der Annahme einer inversen kretazischen Feld-Richtung überlappt der Konfidenzkreis des virtuellen Pols den kretazischen magnetischen Pol für Afrika, der vonMcElhinny et al. an den Gesteinen des Mlanje Syenites bestimmt wurde.Wenn SE-Sizilien zur Zeit der Extrusion dieser oberkretazischen Laven an Afrika angeheftet war, dann besagt dieses Ergebnis, da\ eine extensive relative Bewegung zwischen diesen beiden schwerlich nacheinander stattgefunden hat.
Résumé La compilation et l'analyse de basaltes d'âge plio-pleistocène et crétacique supérieur dans la SE-Sicile fournit l'information paléomagnétique suivanteDans l'acceptation d'un champ inversé au Crétacique, le cercle de confidence du pÔle virtuel recouvre le pÔle magnétique crétacique pour l'Afrique, tel queMcElhinny et al. l'ont déduit des roches de la Syénite de Mlanje. Si l'on rattache le SE de la Sicile à l'Afrique au moment de l'éruption de ces laves du Crétacique supérieur, ce résultat signifie qu'il est peu probable qu'un mouvement relatif extensif ait eu lieu entre les deux.
- - , , Elhinny . Mlanje Syenites. - «» , , - .相似文献