全文获取类型
收费全文 | 211篇 |
免费 | 10篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 11篇 |
地球物理 | 79篇 |
地质学 | 92篇 |
海洋学 | 3篇 |
天文学 | 25篇 |
自然地理 | 14篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 12篇 |
2017年 | 11篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 6篇 |
2013年 | 13篇 |
2012年 | 8篇 |
2011年 | 16篇 |
2010年 | 17篇 |
2009年 | 8篇 |
2008年 | 10篇 |
2007年 | 14篇 |
2006年 | 8篇 |
2005年 | 1篇 |
2004年 | 9篇 |
2003年 | 3篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 5篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1990年 | 2篇 |
1987年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1968年 | 1篇 |
1965年 | 1篇 |
1940年 | 1篇 |
1925年 | 1篇 |
排序方式: 共有226条查询结果,搜索用时 31 毫秒
81.
AbstractDiorites and granitoids that intruded the Upper Austroalpine units of the central Alps during the Permian display map-pable tectonic imprints and metamorphic transformations that were acquired during the Alpine tectonometamorphic cycle. Superposed heterogeneous deformations interacted with metamorphic re-equilibration stages and created a range of textural types that reflect local deformation gradients: coronitic transformations textures, normally foliated S-tectonites and mylonitic foliations. The three textural types are distinguished on maps recording foliation trajectories of successive deformation phases, which are correlated to the evolution of metamorphic assemblages. Tectonic deformation of Alpine age is represented by three generations of ductile syn-metamorphic structures. The mineral assemblages stable during the first Alpine deformation phase (D1) are AmpII + P1II + white mica, + Zo/Czo + Grt + Qtz ± Mg-Ch1 ± Ilm in metadiorites and P1II + white micaI + Zo/Czo + Grt + AmpII + Qtz ± Ilm/Ttn in metagranitoids; the successive foliations D2a and D2b are defined by greenschist facies minerals. Thermobarometric estimates allow T = 500–600 °C and P = 1.1 ± 0.2 GPa conditions to be determined during D1 and T ≤ 350 °C and P ≤ 0.5 GPa during D2. Relict igneous minerals in metadiorites allow to determine intrusive conditions of T = 879 ± 110 °C and P = 0.4–0.7 GPa. Radiometric ages and P/T ratio of Alpine PmaxTPmax suggest that the inferred P-T-d-t path may represent the thermal state of the initial Alpine subduction stages. © 2000 Éditions scientifiques et médicales Elsevier SAS 相似文献
82.
Thomas Monecke Sven Petersen Mark D. Hannington Marco Anzidei Alessandra Esposito Guido Giordano Dieter Garbe-Sch?nberg Nico Augustin Bernd Melchert Mike Hocking 《Bulletin of Volcanology》2012,74(9):1937-1944
Explosions of hot water, steam, and gas are common periodic events of subaerial geothermal systems. These highly destructive events may cause loss of life and substantial damage to infrastructure, especially in densely populated areas and where geothermal systems are actively exploited for energy. We report on the occurrence of a large number of explosion craters associated with the offshore venting of gas and thermal waters at the volcanic island of Panarea, Italy, demonstrating that violent explosions similar to those observed on land also are common in the shallow submarine environment. With diameters ranging from 5 to over 100?m, the observed circular seafloor depressions record a history of major gas explosions caused by frequent perturbation of the submarine geothermal system over the past 10,000?years. Estimates of the total gas flux indicate that the Panarea geothermal system released over 70?Mt of CO2 over this period of time, suggesting that CO2 venting at submerged arc volcanoes contributes significantly to the global atmospheric budget of this greenhouse gas. The findings at Panarea highlight that shallow submarine gas explosions represent a previously unrecognized volcanic hazard around populated volcanic islands that needs to be taken into account in the development of risk management strategies. 相似文献
83.
Emplacement mechanism of gravity flows inferred from high resolution Lidar data: The 1944 Somma–Vesuvius lava flow (Italy) 总被引:1,自引:1,他引:0
A Digital Terrain Model derived from high resolution Lidar data allows the determination of the morphometric and physical parameters of a lava flow erupted from the Somma–Vesuvius volcano in 1944. The downstream variation of morphometric parameters including slope, aspect, relative relief, thickness, width, and cross sectional area is analyzed, and the changes in viscosity, velocity and flow rate are estimated. The aims of the analyses are to recognize different flow surfaces, to reconstruct the flow kinematics, and to obtain information on the mechanism of emplacement. The results indicate that the 1944 lava flow can be divided in three sectors: a near vent sector (NVS) characterized by a toe-like surface, an intermediate sector (IS) with an ‘a’ātype brittle surface, and a distal sector (DS) with a sheet-like ductile surface. Lateral leveés and channels do not occur in NVS, whereas they are well developed in IS. In DS, leveés increase with an increasing distance from the vent. Fold-like surfaces occur in NVS and DS, reflecting local shortening processes due to a decrease in the slope of the substratum and overflows from the main channel. IS and DS emplaced between March 18 and 21, 1944, whereas NVS emplaced on March 19 and partly covered IS. The morphometric and physical parameters indicate that IS moved in a ‘tube’-like regime, whereas DS emplaced in a 'mobile crust' regime. The IS to DS transition is marked by an increase in velocity and the flow rate, and by a decrease in thickness, width, cross sectional area, and viscosity. This transition is due to an abrupt increase in the slope of the substratum. The estimated velocity values are in good agreement with the measurements during the 1944 eruption. The analysis used here may be extended to other lava flows. Some gravity flows (debris/mud flows, floods, and avalanches) have rheological properties and shapes similar to those of lavas, and the same process-form relationships may apply to these flows. The approach used here may be therefore useful for evaluating hazards from various gravity currents. 相似文献
84.
With this study, we analyzed two long-term precipitation time series recorded at Alpe Devero and Domodossola (Italian Western Alps) for two periods (1916–2010 and 1872–2010, respectively). The aims of the study were: to create the first precipitation time series covering more than 50?years for Alpe Devero, to extend and update the precipitation time series for Domodossola, to detect changes by means of trend analysis on the precipitation time series. After an accurate analysis of the metadata and the measurements recorded at each station, a trend analysis was performed on both datasets. The results showed a statistically significant decline in winter, summer, and annual precipitation at Alpe Devero and a nonsignificant decrease in seasonal and annual precipitation at Domodossola. Covering more than 90?years, the long-term precipitation time series at Alpe Devero and Domodossola represent unique data sets for this sector of Italian Western Alps. Continuing updating of the data could provide a useful resource for climate change studies in this area and, within a wider perspective, in Alpine regions. 相似文献
85.
86.
87.
M. Iole Spalla Davide Zanoni Guido Gosso Michele Zucali 《International Journal of Earth Sciences》2009,98(1):203-226
The volcano–clastic sequence of Trompia Valley, which caps the Tre Valli Bresciane Variscan basement (TVB), comprises the
Dosso dei Galli Conglomerate (DGC), the oldest deposit containing up to metre-sized metamorphic pebbles. This Lower Permian
formation of the Trompia Basin was fed by the erosion products of the Variscan chain. We used microstructural and mineral
chemical data on metamorphic pebbles of the DGC to infer a quantitative tectono-thermal evolution of the eroded pre-Permian
basement and to compare them with those of TVB and the surrounding Southalpine basement units (tectono-metamorphic units = TMUs).
Metapelitic and metaintrusive pebbles record a polyphase metamorphism with two metamorphic re-equilibrations: the first under
epidote amphibolite facies (M1, ) and the second under greenschist facies (M2) conditions. Rock types and metamorphic data largely match those of TVB basement
unit. The structural and metamorphic records in the pebbles are pre-Permian, and the conglomerate matrix is non-metamorphic.
The DGC deposition age (283 ± 1–280.5 ± 2 Ma) constrains the minimal exhumation age of its basement source. The lack of staurolite
bearing assemblages in metamorphic pebbles suggests that the DGC basement source was already exhumed to shallow structural
levels (greenschist facies conditions) before the thermal equilibration consequent upon continental crust thickening induced
by the Variscan collision. 相似文献
88.
89.
Guido Giordano 《Bulletin of Volcanology》1998,60(1):10-26
The Quaternary White Trachytic Tuffs Formation from Roccamonfina Volcano (southern Italy) comprises four non-welded, trachytic,
pyroclastic sequences bounded by paleosols, each of which corresponds to small- to intermediate-volume explosive eruptions
from central vents. From oldest to youngest they are: White Trachytic Tuff (WTT) Cupa, WTT Aulpi, WTT S. Clemente, and WTT
Galluccio. The WTT Galluccio eruption was the largest and emplaced ∼ 4 km3 of magma. The internal stratigraphy of all four WTT eruptive units is a complex association of fallout, surge, and pyroclastic
flow deposits. Each eruptive unit is organized into two facies associations, Facies Association A below Facies Association
B. The emplacement of the two facies associations may have been separated by short time breaks allowing for limited reworking
and erosion. Facies Association A consists of interbedded fallout deposits, surge deposits, and subordinate ignimbrites. This
facies association involved the eruption of the most evolved trachytic magma, and pumice clasts are white and well vesiculated.
The grain size coarsens upward in Facies Association A, with upward increases of dune bedform wavelengths and a decrease in
the proportion of fine ash. These trends could reflect an increase in eruption column height from the onset of the eruption
and possibly also in mass eruption rate. Facies Association B comprises massive ignimbrites that are progressively richer
in lithic clast content. This association involved the eruption of more mafic magma, and pumice clasts are gray and poorly
vesiculated. Facies Association B is interpreted to record the climax of the eruption. Phreatomagmatic deposits occur at different
stratigraphic levels in the four WTT and have different facies characteristics. The deposits reflect the style and degree
of magma–water interaction and the local hydrogeology. Very fine-grained, lithic-poor phreatomagmatic surge deposits found
at the base of WTT Cupa and WTT Galluccio could record the interaction of the erupting magma with a lake that occupied the
Roccamonfina summit depression. Renewed magma–water interaction later in the WTT Galluccio eruption is indicated by fine grained,
lithic-bearing phreatomagmatic fall and surge deposits occurring at the top of Facies Association A. They could be interpreted
to reflect shifts of the magma fragmentation level to highly transmissive, regional aquifers located beneath the Roccamonfina
edifice, possibly heralding a caldera collapse event.
Received: 26 August 1996 / Accepted: 27 February 1998 相似文献
90.
Dirk?Sachse Jens?Radke Reinhard?Gaupp Lorenz?Schwark Guido?Lüniger Gerd?GleixnerEmail author 《International Journal of Earth Sciences》2004,93(4):554-564
For the first time 18O and 13C values from carbonates and D values of individual n-alkanes were used to reconstruct palaeohydrological conditions in a lagoon at the southern margin of the Central European Zechstein Basin (CEZB). A 12-m core covering the complete Ca2 interval and adjacent anhydrites (A1 and A2) was analyzed for 18O and 13C values of dolomitized carbonates and D values of individual n-alkanes. 18Ocarb values (+2 to +5 vs. VPDB) were strongly influenced by evaporation and temporal freshwater input into the lagoon. The 13Ccarb values (–1 to +4 vs. VPDB) were controlled mainly by changes in primary production. Both isotopic ratios show an inverse relationship throughout most of the core, contradicting diagenetic alteration, since 13Ccarb values are not altered significantly during dolomitization. Assuming a temperature range of 35–40 °C in the lagoon, 18Ocarb values of +2.5 to +8 (vs. VSMOW) for the lagoonal water can be reconstructed. The lagoon may have desiccated twice during the Ca2 interval, as indicated by very high 18Ocarb and low 13Ccarb values, coinciding with increasing amount of anhydrite in the analyzed sample. These events seem to reflect not just local but a regional intra-Ca2 cyclicity. Measured D values of the short-chain n-alkanes, namely n-C16 and n-C18 which are widely used as indicators for photosynthetic bacterial and algal input, reflect the isotopic composition of the lagoonal water. Assuming constant fractionation during incorporation of hydrogen into lipids of –160, an average D value of +70 (vs. VSMOW) can be reconstructed for the lagoonal water, accounting for very arid conditions. The long-chain n-alkanes n-C27, n-C28, n-C29 and n-C30, thought to be derived from the leaf waxes of terrestrial higher plants, were shown to be depleted in D relative to the short-chain alkanes, therefore indicating a different hydrogen source. Terrestrial plants in arid areas mainly use water supplied by precipitation. By using a smaller fractionation of –120 due to evaporation processes in the leaves, reconstructed values vary between –74 and –9 (vs. VSMOW). These values are not indicating extremely arid conditions, implying that the long-chain n-alkanes were transported trough wind and/or rivers into the lagoon at the Zechstein Sea coast. Dwater values, reconstructed using the n-C16 alkane and 18O water values, independently reconstructed on the same sample using the temperature dependant fractionation for dolomites are good agreement and suggest high amounts of evaporation affecting the coastal lagoon. Altogether, our results indicate that hydrogen isotopic ratios of n-alkanes give information on their origin and are a useful proxy for palaeoclimatic reconstruction. 相似文献