全文获取类型
收费全文 | 159篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 11篇 |
地球物理 | 41篇 |
地质学 | 61篇 |
海洋学 | 18篇 |
天文学 | 26篇 |
综合类 | 1篇 |
自然地理 | 7篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2016年 | 9篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 21篇 |
2012年 | 2篇 |
2011年 | 15篇 |
2010年 | 7篇 |
2009年 | 8篇 |
2008年 | 10篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 7篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1976年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有167条查询结果,搜索用时 421 毫秒
141.
Hao Gao Seyed Ali Ghoreishian Amiri Signe Kjelstrup Gustav Grimstad Benoit Loranger Elena Scibilia 《国际地质力学数值与分析法杂志》2023,47(1):82-105
This paper presents a fully coupled thermo-hydro-mechanical (THM) model which simulates frost heave in fully saturated soils. The model is able to simulate the formation and growth of multiple distinct ice lenses. The basic equations of the system were derived using the continuum theory of mixtures, nonequilibrium thermodynamics, and fracture mechanics, considering skeleton deformation, water flow and heat transport. Central to this model is the coupled transport of mass due to the temperature gradient across the frozen fringe, which acts as the main driving force of the phenomenon. The model is formulated in terms of measurable physical properties and thus no ad hoc parametrization is required. In an ice-lens-free state, the system is solved as a continuum using the finite element method (FEM). It is then locally treated as a discontinuous system upon the formation of ice lens, by enriching the elements carrying the embedded ice lens(es) using the extended finite element method (X-FEM). The accuracy and efficiency of the proposed model has been verified using several laboratory tests on Devon silt samples at different overburden pressures and thermal boundary conditions. Shut-off pressures have been also estimated and compared with the experimental results. 相似文献
142.
143.
Alexandre Pryet James Ramm Jean-Paul Chilès Esben Auken Benoit Deffontaines Sophie Violette 《Journal of Applied Geophysics》2011,75(2):277-283
We develop a technique allowing 3D gridding of large sets of 1D resistivity models obtained after inversion of extensive airborne EM surveys. The method is based on the assumption of a layered-earth model. 2D kriging is used for interpolation of geophysical model parameters and their corresponding uncertainties. The 3D grid is created from the interpolated data, its structure accurately follows the geophysical model, providing a lightweight file for a good rendering. Propagation of errors is tracked through the quantification of uncertainties from both inversion and interpolation procedures. The 3D grid is exported to a portable standard, which allows flexible visualization and volumetric computations, and improves interpretation. The method is validated and illustrated by a case-study on Santa Cruz Island, in the Galapagos Archipelago. 相似文献
144.
Berit Legler Howard D. Johnson Gary J. Hampson Benoit Y.G. Massart Chris A‐L. Jackson Matthew D. Jackson Ahmed El‐Barkooky Rodmar Ravnas 《Sedimentology》2013,60(5):1313-1356
Existing facies models of tide‐dominated deltas largely omit fine‐grained, mud‐rich successions. Sedimentary facies and sequence stratigraphic analysis of the exceptionally well‐preserved Late Eocene Dir Abu Lifa Member (Western Desert, Egypt) aims to bridge this gap. The succession was deposited in a structurally controlled, shallow, macrotidal embayment and deposition was supplemented by fluvial processes but lacked wave influence. The succession contains two stacked, progradational parasequence sets bounded by regionally extensive flooding surfaces. Within this succession two main genetic elements are identified: non‐channelized tidal bars and tidal channels. Non‐channelized tidal bars comprise coarsening‐upward sandbodies, including large, downcurrent‐dipping accretion surfaces, sometimes capped by palaeosols indicating emergence. Tidal channels are preserved as single‐storey and multilateral bodies filled by: (i) laterally migrating, elongate tidal bars (inclined heterolithic strata, 5 to 25 m thick); (ii) forward‐facing lobate bars (sigmoidal heterolithic strata, up to 10 m thick); (iii) side bars displaying oblique to vertical accretion (4 to 7 m thick); or (iv) vertically‐accreting mud (1 to 4 m thick). Palaeocurrent data show that channels were swept by bidirectional tidal currents and typically were mutually evasive. Along‐strike variability defines a similar large‐scale architecture in both parasequence sets: a deeply scoured channel belt characterized by widespread inclined heterolithic strata is eroded from the parasequence‐set top, and flanked by stacked, non‐channelized tidal bars and smaller channelized bodies. The tide‐dominated delta is characterized by: (i) the regressive stratigraphic context; (ii) net‐progradational stratigraphic architecture within the succession; (iii) the absence of upward deepening trends and tidal ravinement surfaces; and (iv) architectural relations that demonstrate contemporaneous tidal distributary channel infill and tidal bar accretion at the delta front. The detailed facies analysis of this fine‐grained, tide‐dominated deltaic succession expands the range of depositional models available for the evaluation of ancient tidal successions, which are currently biased towards transgressive, valley‐confined estuarine and coarser grained deltaic depositional systems. 相似文献
145.
Benoit Cushman-Roisin 《地球物理与天体物理流体动力学》2013,107(1-2):35-59
Abstract A new model of convection and mixing is presented. The fluid is envisioned as being composed of two buoyant interacting fluids, called thermals and anti-thermals. In the context of the Boussinesq approximation, pairs of governing equations are derived for thermals and anti-thermals. Each pair meets an Invariance Principle as a consequence of the reciprocity in the roles played by thermals and anti-thermals. Each pair is transformed into an average equation for which interaction terms cancel and another very simple equation linking the two fluid properties. An important parameter of the model is the fraction, f, of area occupied by thermals to the total area. A dynamic saturation equilibrium between thermals and antithermals is assumed. This implies a constant values of f throughout the system. The set of equations is written in terms of mean values and root-mean-square fluctuations, in keeping with equations of turbulence theories. The final set consists of four coupled non-linear differential equations. The model neglects dissipation and can be applied to any convective situations where molecular viscosity and diffusivity may be neglected. Applications of the model to mixed-layer deepening and penetrative convection are presented in subsequent papers. 相似文献
146.
The barotropic instability is traditionally viewed as an initial-value problem wherein wave perturbations of a laterally sheared flow in a homogeneous uniformly rotating fluid that temporally grows into vortices. The vortices are capable of mixing fluid on the continental shelf with fluid above the continental slope and adjacent deep-sea region. However, the instability can also be viewed as a boundary-value problem. For example, a laterally sheared coastal flow is perturbed at some location, creating perturbations that grow spatially downstream. This process leads to a time periodic flow that exhibits instability in space. This article first examines the linear barotropic instability problem with real frequency and complex wavenumber. It is shown that there exists a frequency band within which a spatially growing wave is present. It is then postulated that far downstream the spatially unstable flow emerges into a chain of identically axisymmetric vortices. Conservation of mass, momentum and energy fluxes are applied to determine the diameter, spacing and the speed of translation of the vortices. 相似文献
147.
Abstract— Two groups of chondrules in the Murchison CM chondrite, which have previously been identified on the basis of FeO in the chondrule grains, are readily identified from cathodoluminescence (CL) and belong to those of the ordinary chondrite group A and B chondrules of Sears et al. (1992a). All chondrules are surrounded by fine-grained rims containing forsterite with bright red CL, but on group A chondrules an outer thin rim grades into a much thicker rim, with a lower density of forsterite grains, which in turn grades into the central chondrule. Group B chondrules have only the thin outer rim with a high density of small forsterite grains. This is the first time an unequivocal correlation has been observed between chondrule rim thickness and the composition of the object on which the rim is located. We suggest that while all objects in the meteorite (group B chondrules, refractory inclusions, mineral and chondrule fragments, clasts) acquired a very thin rim during processing in a wet regolith, the thick rims on group A chondrules were formed by aqueous alteration of precursor metal- and sulfide-rich rims which are a characteristic of group A chondrules in ordinary chondrites. 相似文献
148.
A major late Paleozoic depocentre, the Sverdrup Basin, Canadian High Arctic, has been largely left out of the latest Permian extinction debate, as early workers presumed Middle to Late Permian strata were absent. Basin-scale sequence-stratigraphic and chemostratigraphic correlations indicate Late Permian strata are only missing on the basin margins, where they were removed by sub-Triassic erosion, whereas continuous deposition is recorded in the basin centre. The varying degree of sub-Triassic erosion has significant impact on the carbon-isotope record across the Latest Permian Extinction event, where both the apparent rate and magnitude of carbon-isotope shift vary as a function of basin position. The intrabasin variability in apparent δ13Corg shift across the event is equivalent to that observed globally. In contrast to the abrupt isotope shifts recorded on the basin margin, similar to many records reported globally, the basin centre section shows a systematic shift associated with the Latest Permian Extinction. The Earth likely underwent a prolonged period of increasing environmental stress leading up to the event. 相似文献
149.
Determination of Trace Element Mass Fractions in Ultramafic Rocks by HR‐ICP‐MS: A Combined Approach Using a Direct Digestion/Dilution Method and Preconcentration by Coprecipitation 下载免费PDF全文
Mathieu Rospabé Mathieu Benoit Frédéric Candaudap 《Geostandards and Geoanalytical Research》2018,42(1):115-129
A procedure is described for the determination of thirty‐seven minor and trace elements (LILE, REE, HFSE, U, Th, Pb, transition elements and Ga) in ultramafic rocks. After Tm addition and acid sample digestion, compositions were determined both following a direct digestion/dilution method (without element separation) and after a preconcentration procedure using a double coprecipitation process. Four ultramafic reference materials were investigated to test and validate our procedure (UB‐N, MGL‐GAS [GeoPT12], JP‐1 and DTS‐2B). Results obtained following the preconcentration procedure are in good agreement with previously published work on REE, HFSE, U, Th, Pb and some of the transition elements (Sc, Ti, V). This procedure has two major advantages: (a) it avoids any matrix effect resulting from the high Mg content of peridotite, and (b) it allows the preconcentration of a larger trace element set than with previous methods. Other elements (LILE, other transition elements Cr, Mn, Co, Ni, Cu, Zn, as well as Ga) were not fully coprecipitated with the preconcentration method and could only be accurately determined through the direct digestion/dilution method. 相似文献
150.
Hydrous partial melting in the sheeted dike complex at fast spreading ridges: experimental and natural observations 总被引:5,自引:1,他引:4
Lydéric France Juergen Koepke Benoit Ildefonse Sarah B. Cichy Fabien Deschamps 《Contributions to Mineralogy and Petrology》2010,160(5):683-704
In ophiolites and in present-day oceanic crust formed at fast spreading ridges, oceanic plagiogranites are commonly observed
at, or close to the base of the sheeted dike complex. They can be produced either by differentiation of mafic melts, or by
hydrous partial melting of the hydrothermally altered sheeted dikes. In addition, the hydrothermally altered base of the sheeted
dike complex, which is often infiltrated by plagiogranitic veins, is usually recrystallized into granoblastic dikes that are
commonly interpreted as a result of prograde granulitic metamorphism. To test the anatectic origin of oceanic plagiogranites,
we performed melting experiments on a natural hydrothermally altered dike, under conditions that match those prevailing at
the base of the sheeted dike complex. All generated melts are water saturated, transitional between tholeiitic and calc-alkaline,
and match the compositions of oceanic plagiogranites observed close to the base of the sheeted dike complex. Newly crystallized
clinopyroxene and plagioclase have compositions that are characteristic of the same minerals in granoblastic dikes. Published
silicic melt compositions obtained in classical MORB fractionation experiments also broadly match the compositions of oceanic
plagiogranites; however, the compositions of the coexisting experimental minerals significantly deviate from those of the
granoblastic dikes. Our results demonstrate that hydrous partial melting is a likely common process in the root zone of the
sheeted dike complex, starting at temperatures exceeding 850°C. The newly formed melt can either crystallize to form oceanic
plagiogranites or may be recycled within the melt lens resulting in hybridized and contaminated MORB melts. It represents
the main MORB crustal contamination process. The residue after the partial melting event is represented by the granoblastic
dikes. Our results support a model with a dynamic melt lens that has the potential to trigger hydrous partial melting reactions
in the previously hydrothermally altered sheeted dikes. A new thermometer using the Al content of clinopyroxene is also elaborated. 相似文献