全文获取类型
收费全文 | 128篇 |
免费 | 0篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 5篇 |
地球物理 | 17篇 |
地质学 | 24篇 |
海洋学 | 9篇 |
天文学 | 67篇 |
综合类 | 2篇 |
自然地理 | 3篇 |
出版年
2021年 | 3篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 6篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 3篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2009年 | 3篇 |
2008年 | 6篇 |
2007年 | 9篇 |
2006年 | 10篇 |
2005年 | 10篇 |
2004年 | 6篇 |
2003年 | 12篇 |
2002年 | 7篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 2篇 |
排序方式: 共有128条查询结果,搜索用时 31 毫秒
81.
Boron isotopic variations in fumarolic condensates and thermal waters from Vulcano Island, Italy: Implications for evolution of volcanic fluids 总被引:1,自引:0,他引:1
Temporal variation in the isotopic composition of boron has been monitored in fumarolic condensates collected over an extended time period (1970-1996) from La Fossa crater, Volcano Island. We also report comparative boron isotopic data for representative Vulcano lavas and for shallow hydrologic samples (seawater, wells, thermal springs) from the north flank of La Fossa. Combined with concurrent chemical and isotopic (δ18O, δD) data for the fumaroles, these results indicate that the fumarolic fluids record mixing relations between three distinct fluid end members: (1) a dominantly magmatic fluid (EM1); (2) a mixture of modified seawater with magmatic fluid (EM2); and (3) an aqueous fluid produced from seawater by extensive wall-rock reaction, evaporation, and boiling (AF). Differences between the latter two end members are most clearly accentuated on the basis of the boron isotopic data. Long-term compositional variations for crater fumaroles were dominated by EM1-AF mixing between 1979-88, with progressive decrease in EM1 contribution with time, and by EM2-AF mixing between 1988-96. The exact spatial distribution of these fluid reservoirs remains unclear, but all must have been present throughout the monitoring period to account for the observed variations. Moreover, the combined B-O-H data seem to preclude important contributions from shallow meteoric reservoirs. Marked short-term variations in δ11B closely coincide with episodes of local seismicity, which presumably triggered reorganization of hydrothermal circulation patterns; gradual variations over periods up to 3-4 years are associated with relatively low seismicity during which fluid circulation was likely influenced by effects of mineral precipitation on permeability of the hydrologic system. 相似文献
82.
Mercury concentrations in fish, faeces and exhaled air were investigated in order to evaluate total mercury exposure through the gut in captive bottlenose dolphin and excretion via intestine and pulmonary routes. Results showed that faeces account for elimination of 34-48% of dietary mercury; while only 0.9-1.2% of alimentary mercury is eliminated through exhaled air. The remaining 51.2-65.3% of ingested mercury, ranging approximately between 266 and 339 microg per day, is retained within the organism. The complexation of mercury with selenium, forming insoluble tiemannite granules, is discussed as an important mechanism, complementary to excretion, by which odontocetes are able to cope with elevated alimentary exposure to mercury. 相似文献
83.
Both the 34 value and the total S content of products from Vulture Volcano, Italy are mainly controlled by the separation of S gases, predominantly SO2, from high f
O2magmas containing S predominantly as SO
2-
4
. The addition of evaporites to such magmas appears to be a relatively uncommon and limited phenomenon. The total S content of the most primitive product of Vulture Volcano (5600 mg/kg) is very high. The high 34S value of 4 indicates an origin through the partial melting of a mantle containing high S, enriched in 34S of unknown origin. 相似文献
84.
Nineteen samples of granites, orthogneisses and paragneisses from the High Himalaya basement nappe(s) of the Mount Everest region have been dated by the Rb/Sr method. The post-metamorphic tourmaline leucogranites of the upper Imja Drangka (Nuptse, Lhotse Glacier) have high initial Sr87/Sr86 characteristic of an anatectic origin from crustal material. A whole-rock isochron age of 52 m. y. (Early Eocene) has been obtained for the samples from the granite body of Lhotse Glacier; apparently Sr isotopic homogenization was not reached throughout the much larger Nuptse granite. The granite precursor of the migmatitic orthogneisses from the upper Dudh Kosi valley has an age of 550 ± 16 m. y. (whole rock isochron) and a high initial Sr87/Sr86 ratio indicating its origin from an older basement complex. The Rb/Sr data on paragneisses from the south face of Lhotse do not define an isochron, possibly reflecting isotopic hetero-geneity in the sedimentary protoliths and incomplete homogenization during a late Precambrian metamorphism. All the mineral ages fall in the time span from 15 to 17 m. y. They represent cooling ages reflecting a regional phase of major uplift in the Middle Miocene and post-dating the peak of the Himalayan metamorphism which the data from the Mt. Everest region place in pre-Eocene times. 相似文献
85.
Franco Barberi Fabrizio Innocenti Giorgio Ferrara Jörg Keller Letterio Villari 《Earth and Planetary Science Letters》1974,21(3):269-276
The Eolian arc is located at the boundary between the converging African and European plates. Its volcanism is characterized by a marked evolution in a restricted time (less than 1 my). A progressive transition is observed from typical calc-alkaline series toward shoshonitic rocks produced by past and present activity (Vulcano and Stromboli). By comparison with circum-Pacific island arcs, the evolution of Eolian volcanism can be related to a rapid deepening of the Benioff zone. The occurrence of shoshonitic rocks and the continental nature of the crust on both sides of the plate boundary suggest that the Eolian arc is in a senile stage of evolution. Petrology and Sr isotopic data indicate a probable mantle source for Eolian volcanism. 相似文献
86.
Campi Flegrei is a Holocene volcanic area in the Campanian Plain (Southern Italy) within the Apennine Chain, a neogenic thrust belt built up since the Middle Miocene. The volcanic complex consists of a c. 12-km-diameter caldera containing several monogenetic volcanoes, the youngest of which (Monte Nuovo) erupted in 1538. Since at least Roman times, the area has also been affected by slow vertical movements (bradiseismic activity). Between 1982 and 1985, this slow motion was interrupted by a period of more rapid displacement which caused a maximum uplift of 180 cm in the town of Pozzuoli. To model the local stress field associated with the uplift, the Angelier inversion technique has been applied using the focal mechanisms of forty-nine earthquakes which occurred between April 1982 and December 1984. The results show that doming coupled with a regional extensional strain can account for the seismic phenomena that affected the area. 相似文献
87.
During two expeditions in the Danakil depression (Ethiopia), water samples were collected from: (a) hot springs in Dallol, Salt Plain, in the north of the depression; (b) cold and hot springs around Lake Giulietti; and c) Lake Giulietti.The isotopic results indicate: the water from Dallol hot springs is enriched in18O by isotopic exchange with the rocks as has been observed in many other geothermal areas of the world; b) the isotopic composition of the Lake Giulietti water changes with depth, probably as a consequence of a seasonal stratification; c) the springs in the Lake Giulietti region contain waters which result from the mixing of local meteoric water with a brine, or with lake waters. 相似文献
88.
A. M. Caredda A. Cristini C. Ferrara M. F. Lobina M. Baroli 《Environmental Geology》1999,38(2):91-100
We have studied sediments of the Piscinas beach (SW Sardinia, Italy), which is supplied by two streams that wash mine dumps
of abandoned lead and zinc mines at Montevecchio and Ingurtosu, situated inland from the supply basin of the beach itself.
A study of the texture, mineralogy and geochemistry of the sediments was conducted for the purpose of assessing the possible
influence of the mine waste on the composition of the sediments, looking for any anomalous enrichments in heavy metals. Furthermore,
to evaluate and quantify metal release into the sea, samples of Posidonia oceanica, a bioaccumulator marine plant, were also examined. The results indicate that the distribution of heavy metals in the foreshore
sediments is particularly affected by the contribution of the streams, while in the shoreface the distribution is affected
by the currents that disperse the sediments both out to sea and southwards. The metal contents of the Posidonia oceanica are correlated with the different stages of activity of the mines.
Received: 28 January 1998 · Accepted: 22 April 1998 相似文献
89.
S. Bianchi A. Ferrara J. I. Davies P. B. Alton 《Monthly notices of the Royal Astronomical Society》2000,311(3):601-610
We present Monte Carlo radiative-transfer simulations for spiral galaxies modelled as a stellar disc and a two-phase clumpy dust distribution. We divide the volume occupied by the dust into a three-dimensional grid and assign each cell a clump or smooth medium status. Cell dimension, clump dust mass and spatial distribution are derived from the observed properties of giant molecular clouds and molecular gas in the Galaxy. We produce models for several values of the optical depth and fraction of the interstellar medium residing in clumps. As a general result, clumpy models are less opaque than the corresponding homogeneous models. For the adopted parameters, the increase in the fraction of energy that escapes the disc is moderate, resulting in surface-brightness profiles that are less than one magnitude brighter than those of the homogeneous models. The effects of clumping are larger for edge-on views of the disc. This is in contrast with previous preliminary results for clumping in the literature. We show how differences arise from the different parametrization and clump distribution adopted. We also consider models in which a fraction of the stellar radiation is emitted within the clumps. In this case, galaxies are less transparent than in the case when only dust is clumped. The opacity can be even higher than in the homogeneous case, depending on the fraction of embedded stellar emission. We point out the implications of the results for the determination of the opacity and dust mass of spiral galaxies. 相似文献
90.
Marialuce Bruscoli rea Ferrara Roberto Fabbri Benedetta Ciardi 《Monthly notices of the Royal Astronomical Society》2000,318(4):1068-1072
We calculate the secondary anisotropies in the cosmic microwave background (CMB) produced by inhomogeneous reionization from simulations in which the effects of radiative and stellar feedback effects on galaxy formation have been included. This allows us to determine self-consistently the beginning ( z i ≈30), the duration ( δz ≈20) and the (non-linear) evolution of the reionization process for a critical density cold dark matter (CDM) model. In addition, from the simulated spatial distribution of ionized regions, we are able to calculate the evolution of the two-point ionization correlation function, C χ , and obtain the power spectrum of the anisotropies, C ℓ , in the range 5000<ℓ<106 . The power spectrum has a broad maximum around ℓ≈30 000, where it reaches the value 2×10−12 . We also show that the ionization correlation function C χ is not Gaussian, but at separation angles θ ≲10−4 rad it can be approximated by a modified Lorentzian shape; at larger separations an anticorrelation signal is predicted for both C χ and C ( θ ). Detection of signals as above will be possible with future millimetre-wavelength interferometers like the Atacama Large Millimeter Array (ALMA) , which appears as an optimum instrument to search for signatures of inhomogeneous reionization. 相似文献