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91.
Maurizio Righetti 《Acta Geophysica》2008,56(3):801-823
The paper addresses the problem of the resistance due to vegetation in an open channel flow, characterized by partially and
fully submerged vegetation formed by colonies of bushes. The flow is characterized by significant spatial variations of velocity
between vertical profiles that make the traditional approach based on time averaging of turbulent fluctuations inconvenient.
A more useful procedure, based on time and spatial averaging (Double-Averaging Method) is applied for the flow field analysis
and characterization. The vertical distribution of mean velocity and turbulent stresses at different spatial locations has
been measured with a 3D Acoustic Doppler Velocimeter (ADV) for two different vegetation densities where fully submerged real
bushes (salix pentandra) have been used. Velocity measurements were completed together with the measurements of drag exerted
on the flow by bushes at different flow depths. The analysis of velocity measurements allows depicting the fundamental characteristics
of both the mean flow field and turbulence. The experimental data show that the contribution of form-induced stresses to the
momentum balance cannot be neglected. The mean velocity profiles and the spatially averaged turbulent intensity profiles allow
inferring that the vegetation density is a driving parameter for the development of a mixing layer at the canopy top in the
case of submerged vegetation. Moreover, the net upward turbulent momentum flux, evaluated with the methodology proposed by
Lu and Willmarth (1973), appears to be damped for increased vegetation density; this finding can rationally explain the reduction
of the suspended sediment transport capacity typically observed in free surface flows over a vegetated bed. 相似文献
92.
Linah Mohamed Ben Calderhead Maurizio Filippone Mike Christie Mark Girolami 《Computational Geosciences》2012,16(2):423-436
This paper presents the application of a population Markov Chain Monte Carlo (MCMC) technique to generate history-matched
models. The technique has been developed and successfully adopted in challenging domains such as computational biology but
has not yet seen application in reservoir modelling. In population MCMC, multiple Markov chains are run on a set of response
surfaces that form a bridge from the prior to posterior. These response surfaces are formed from the product of the prior
with the likelihood raised to a varying power less than one. The chains exchange positions, with the probability of a swap
being governed by a standard Metropolis accept/reject step, which allows for large steps to be taken with high probability.
We show results of Population MCMC on the IC Fault Model—a simple three-parameter model that is known to have a highly irregular
misfit surface and hence be difficult to match. Our results show that population MCMC is able to generate samples from the
complex, multi-modal posterior probability distribution of the IC Fault model very effectively. By comparison, previous results
from stochastic sampling algorithms often focus on only part of the region of high posterior probability depending on algorithm
settings and starting points. 相似文献
93.
Andrea Bollati Sveva Corrado Maurizio Marino 《International Journal of Earth Sciences》2012,101(4):1011-1031
The western Lucretili Mts. in the central Apennines (Latium, Italy) have been recently re-mapped in great detail and are the subject of combined stratigraphic, sedimentological and structural investigations. In this paper, we present a new stratigraphic interpretation of the Jurassic paleogeography of western Lucretili Mts., where a rift-derived intrabasinal paleo-high of the Alpine Tethys has been identified for the first time by means of facies analysis and biostratigraphic dating. Recognised facies associations, combined with dated stratigraphic sections, allow to define the morphology of the structural paleo-high and to identify the associated gravity-driven deposits (olistoliths) accumulated in the surrounding basin. Furthermore, we investigated the modes of interaction between Jurassic extensional structures and the subsequent contractional patterns developed during the Tertiary mountain building. In detail, the role played during Apennines tectonics by the paleo-escarpments bounding the paleo-high and by the surrounding olistoliths has been analysed. The paleo-escarpments either acted as focussing features for ENE-directed frontal thrust ramp localisation and were offset with small shortening amounts or reactivated as NNE striking high angle transpressional faults or preserved the original geometries as a result of variable orientation of paleo-escarpments with respect to the Neogene compressive stress field (with ENE oriented sigma1). Newly formed ENE striking tear faults connect these either inherited or neo-formed discontinuities. This complex stratigraphic and structural pattern is substantially different from the previous interpretations of this portion of the central Apennines based on a hypothesised layer-cake stratigraphy deformed by neo-formed Neogene thrusts. This contribution strengthens the importance of integrating facies analyses and structural investigations to detect the influence of pre-orogenic structures on compressive structural patterns, in an area where commercial seismic lines are not available and cannot help in reconstructing the subsurface geometries. 相似文献
94.
Francesco Di Benedetto Francesco D’Acapito Fabio Capacci Gabriele Fornaciai Massimo Innocenti Giordano Montegrossi Werner Oberhauser Luca A. Pardi Maurizio Romanelli 《Physics and Chemistry of Minerals》2014,41(3):215-225
We investigated the speciation of Fe in bulk and in suspended respirable quartz dusts coming from ceramic and iron-casting industrial processes via X-ray absorption spectroscopy, with the aim of contributing to a better understanding of the variability of crystalline silica toxicity. Four different bulk industrial quartz powders, nominally pure quartz samples with Fe contents below 200 ppm, and three respirable dusts filters were selected. Fe speciation was determined in all samples through a coupled study of the X-ray absorption near-edge structure and extended X-ray absorption fine structure regions, operating at the Fe–K edge. Fe speciation revealed common features at the beginning of the different production processes, whereas significant differences were observed on both respirable dusts and bulk dusts exiting from the production process. Namely, a common pollution of the raw quartz dusts by elemental Fe was evidenced and attributed to residuals of the industrial production of quartz materials. Moreover, the respirable samples indicated that reactivity occurs after the suspension of the powders in air. The gravitational selection during the particle suspension consistently allowed us to clearly discriminate between suspended and bulk dusts. On the basis of the obtained results, we provide an apparent spectroscopic discrimination between the raw materials used in the considered industrial processes, and those that are effectively inhaled by workers. In particular, an amorphous FeIII oxide, with an unsaturated coordination sphere, can be related to silica reactivity (and health consequences). 相似文献
95.
Tommaso Giovanardi Maurizio Mazzucchelli Alberto Zanetti Antonio Langone Massimo Tiepolo Anna Cipriani 《Central European Journal of Geosciences》2014,6(4):588-613
Phlogopite-bearing lithologies are the main constituent of the Phlogopite-Peridotite unit of the Finero sequence and the result of pervasive migration of metasomatizing melts/fluids. Conversely, the presence of phlogopite within the associated Finero Mafic Complex, a mafic-ultramafic pluton intruded into the metamorphic basement of the Adria plate, is mentioned in literature as rare. Recent detailed fieldwork has evidenced the presence of two distinct phlogopite-rich ultramafic lithologies within the Amphibole-Peridotite unit of the Finero Mafic Complex, where phlogopite is always associated with amphibole. Field and petrographic features of these occurrences, as well as major- and trace-element mineral chemistry, are here presented to i) place constraints on the nature of the parent melt from which they have been generated and ii) to address their relationship with the other lithologies of the Finero Complex. We find that these rocks were formed by late melt migrations along shear zones under high-T conditions. The geochemical affinity of these lithologies is different to the tholeiitic-transitional affinity reported in literature for the Finero Mafic Complex. The enrichment in LREE, Th, U and Sr of the associated amphibole possibly suggests that these phlogopite-bearing lithologies are genetically related to the metasomatic events that have affected the Finero mantle massif. 相似文献
96.
Maria Luce Frezzotti Simona Ferrando Maurizio Petrelli Andrea Perucchi 《Geochimica et cosmochimica acta》2010,74(10):3023-3039
Petrological and geochemical study of volatile bearing phases (fluid inclusions, amphibole, and nominally anhydrous minerals) in a spinel lherzolite xenolith suite from Quaternary lavas at Injibara (Lake Tana region, Ethiopian plateau) shows compelling evidence for metasomatism in the lithospheric mantle in a region of mantle upwelling and continental flood basalts. The xenolith suite consists of deformed (i.e., protogranular to porphyroclastic texture) Cl-rich pargasite lherzolites, metasomatized (LILE and Pb enrichment in clinopyroxene and amphibole) at T ? 1000 °C. Lherzolites contain chlorine-rich H2O-CO2 fluid inclusions, but no melt inclusions. Fluid inclusions are preserved only in orthopyroxene, while in olivine, they underwent extensive interaction with the host mineral. The metasomatic fluid composition is estimated: XCO2 = 0.64, XH2O = 0.33, XNa = 0.006, XMg = 0.006, XCl = 0.018, (salinity = 14-10 NaCl eq. wt.%, aH2O = 0.2, Cl = 4-5 mol.%). Fluid isochores correspond to trapping pressures of 1.4-1.5 GPa or 50-54 km depth (at T = 950 °C). Synchrotron sourced micro-infrared mapping (ELECTRA, Trieste) shows gradients for H2O-distribution in nominally anhydrous minerals, with considerable enrichment at grain boundaries, along intragranular microfractures, and around fluid inclusions. Total water amounts in lherzolites are variable from about 150 up to 400 ppm. Calculated trace-element pattern of metasomatic fluid phases, combined with distribution and amount of H2O in nominally anhydrous minerals, delineate a metasomatic Cl- and LILE-rich fluid phase heterogeneously distributed in the continental lithosphere. Present data suggest that Cl-rich aqueous fluids were important metasomatic agents beneath the Ethiopian plateau, locally forming a source of high water content in the peridotite, which may be easily melted. High Cl, LILE, and Pb in metasomatic fluid phases suggest the contribution of recycled altered oceanic lithosphere component in their source. 相似文献
97.
The effects of a number of inorganic anions (F−, HCO3
−, B(OH)4−, Cl−, I−) and of the siderophore DFO-B on the release of As from volcanic rocks were investigated in batch experiments. While previously
reported field and laboratory data support a role of inorganic anions on As mobilization into aquifers, the role of siderophores
on As-induced mobilization was less investigated. Fluoride, bicarbonate and DFO-B have shown a significant influence on the
release of As from the rocks. Lava was mostly affected among the investigated rocks at pH 6 and 20°C by releasing 4% of its
initial As content in the presence of 0.01 M F−and 10% in the presence of 500 μM DFO-B. The effect of fluoride was larger at pH 6 than at pH 8.5 for all the rocks. In the
case of DFO-B, there was also a larger effect at pH 6 compared to pH 8 for the various rocks except tuff. Bicarbonate played
a role under alkaline conditions while its effect was negligible at pH 6. Anion exchange processes in the presence of fluoride
and bicarbonate and complexation processes in the presence of the siderophore DFO-B appear to be the major processes responsible
for the release of arsenic from the rocks. The siderophore DFO-B plays mainly an indirect role on the As release by complexing
Al, Fe and Mn, thus favoring the dissolution of the rocks and the consequent release of As bound to surface Al, Fe and Mn
oxy-hydroxides. These findings suggest that ionic interactions with fluoride, bicarbonate and siderophore may be a further
triggering factor in the mobilization of As from aquifer rocks. 相似文献
98.
Ugo Chiocchini Fabio Castaldi Maurizio Barbieri Valeria Eulilli 《Hydrogeology Journal》2010,18(6):1319-1341
The stratigraphic and structural setting of the Cimini Mountains and Viterbo area of Italy has been reconstructed. The architecture of the tectonic edifice, below the Pleistocene Cimino and Vicano volcanic districts cover, is characterized by the Mesozoic–Cenozoic Tuscan Nappe and the similar Umbria-Marche Succession; both are capped by the overthrusted Ligurian Late Cretaceous–Eocene Tolfa Flysch. A shallow unconfined volcanic aquifer is separated, by a thick aquiclude, from the deep confined carbonate aquifer consisting of the Tuscan Nappe and the Umbria-Marche Succession. The volcanic aquifer hosts cold waters, whilst the carbonate aquifer hosts hot sulphate–alkaline earth waters that emerge in the thermal area of Viterbo with a temperature of 30–60°C. The recharge area of cold waters is located in the Cimini Mountains. Thermal waters of the Viterbo hot springs are derived from a circuit of waters that emerge along the River Nera near Narni (about 34 km ENE of Viterbo), with a high salinity, a temperature of 16–18°C, a sulphate–alkaline earth composition, and a discharge of 13 m3/sec, whose recharge area is located in the central pre-Apennines reliefs. 相似文献
99.
Discharge areas of carbonate fractured and karstified aquifers are a sensitive system of great interest, where frequently groundwater resources are tapped for drinking water supply. In geological settings affected by recent and/or active tectonics, mixing between fresh water coming from recharge areas and groundwater from deeper circuits, influenced by raising fluids, influences hydrogeochemistry. Surveys on major ions, trace elements and stable isotopes have been performed in the San Vittorino Plain (Central Italy), where the major source of drinking water for Rome is located (Peschiera Springs, mean discharge 18 m3 s?1, half of them tapped). Results of 21 springs revealed different contribution from recharge areas and deep flow paths, by increasing salinity and ion content, with particular references to Ca2+, HCO3 ? and SO4 2?. Three main groups, respectively, related to fresh waters from recharge areas, groundwater from deep contribution and a mixing group between them, have been identified. Water stable isotopes allow to identify the common origin from rainfall and a very steady contribution with seasons and year, due to the huge extent of recharge area (>1000 km2). Saturation Indexes gave insight on the contribution of deep fluids, mainly CO2 and H2S, which turned groundwater to undersaturated conditions, facilitating rock dissolution. By PHREEQC software, the mixing between two considered end-members has been simulated, evaluating about 25% of deep contribution in the basal springs of San Vittorino Plain. Chemistry of Peschiera spring reveals a very limited percentage of deep flow paths (10%), which can lead to slight hydrochemistry changes even in possible drought conditions, when discharge can decrease until 15 m3 s?1. 相似文献
100.
Marcella Leonardi Filippo Azzaro Maurizio Azzaro Gabriella Caruso Monique Mancuso Luis Salvador Monticelli Giovana Maimone Rosabruna La Ferla Francesco Raffa & Renata Zaccone 《Marine Ecology》2009,30(S1):33-42
In the framework of the VECTOR DIVCOST Project, a 2-year investigation was started in 2006, with the aim of testing the sensibility of microbial parameters to environmental changes and of assessing whether they can provide information about functional changes in the carbon cycle. The investigation was performed in the surface waters of two small brackish ponds (Ganzirri and Faro), located in the Cape Peloro transitional area (Sicily, Italy). The seasonal changes in both the microbial compartment [bacterioplankton, vibrios, exoenzymatic hydrolysis of proteins and polysaccharides, bacterial secondary production (HBP) and community respiration] and the trophic state of suspended matter [total suspended matter (TSM), particulate organic carbon (POC), particulate organic nitrogen (PON), C/N] were analysed in relation to the hydrological characteristics [temperature, salinity, oxygen, fluorescence, NH4 , NO2 , NO3 , PO4 ]. Despite marked differences in the nutritional input and the diversification in both carbon budget and trophic level, the two ponds show similar trends in many of the investigated factors, hardly influenced by seasonal variations. Temporally coupled trends were observed for some parameters (enzyme activities, vibrios abundances, respiratory activity), whereas others (POC, PON, heterotrophic bacterial production, bacterioplankton) showed a seasonal shift between the two lakes. The different behaviour found for the some biotic parameters suggests that their response to environmental conditions may be modulated differently between the two lakes, which, despite their spatial proximity and reciprocal connection, do not always show contemporaneous functional processes. 相似文献