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231.
Laurent Koechlin Denis Serre Paul Deba Roser Pelló Christelle Peillon Paul Duchon Ana Ines Gomez de Castro Margarita Karovska Jean-Michel Désert David Ehrenreich Guillaume Hebrard Alain Lecavelier des Etangs Roger Ferlet David Sing Alfred Vidal-Madjar 《Experimental Astronomy》2009,23(1):379-402
The Fresnel Interferometric Imager has been proposed to the European Space Agency (ESA) Cosmic Vision plan as a class L mission.
This mission addresses several themes of the CV Plan: Exoplanet study, Matter in extreme conditions, and The Universe taking shape. This paper is an abridged version of the original ESA proposal. We have removed most of the technical and financial issues,
to concentrate on the instrumental design and astrophysical missions. The instrument proposed is an ultra-lightweight telescope,
featuring a novel optical concept based on diffraction focussing. It yields high dynamic range images, while releasing constraints
on positioning and manufacturing of the main optical elements. This concept should open the way to very large apertures in
space. In this two spacecraft formation-flying instrument, one spacecraft holds the focussing element: the Fresnel interferometric
array; the other spacecraft holds the field optics, focal instrumentation, and detectors. The Fresnel array proposed here
is a 3.6 ×3.6 m square opaque foil punched with 105 to 106 void “subapertures”. Focusing is achieved with no other optical element: the shape and positioning of the subapertures (holes
in the foil) is responsible for beam combining by diffraction, and 5% to 10% of the total incident light ends up into a sharp
focus. The consequence of this high number of subapertures is high dynamic range images. In addition, as it uses only a combination
of vacuum and opaque material, this focussing method is potentially efficient over a very broad wavelength domain. The focal
length of such diffractive focussing devices is wavelength dependent. However, this can be corrected. We have tested optically
the efficiency of the chromatism correction on artificial sources (500 < λ < 750 nm): the images are diffraction limited, and the dynamic range measured on an artificial double source reaches 6.2
10 − 6. We have also validated numerical simulation algorithms for larger Fresnel interferometric arrays. These simulations yield
a dynamic range (rejection factor) close to 10 − 8 for arrays such as the 3.6 m one we propose. A dynamic range of 10 − 8 allows detection of objects at contrasts as high as than 10 − 9 in most of the field. The astrophysical applications cover many objects in the IR, visible an UV domains. Examples are presented,
taking advantage of the high angular resolution and dynamic range capabilities of this concept. 相似文献
232.
Baudouin Raoult Guillaume Aubert Marta Gutiérrez Cristina Arciniegas-Lopez Ricardo Correa 《Earth Science Informatics》2009,2(1-2):63-74
The EU funded SIMDAT project is aimed at applying generic grid technology for the solution of complex application problems in several representative fields including automotive, aerospace, pharmaceutical and meteorology. To satisfy the requirements of the World Meteorological Organization (WMO) and the WMO Information Systems (WIS), the partners in the meteorology activity within SIMDAT (ECMWF, Deutscher Wetterdienst, the UK Met office, EUMETSAT and Météo-France), have developed grid-enabled software that provides generic distributed access to distributed meteorological data repositories via web-based portals, through a series of nodes organized in a mesh network. However, granting access to such an infrastructure, especially considering its fully distributed nature, is a serious challenge and a risk to the security of the overall grid infrastructure. SIMDAT solves this problem by implementing a security model based on a decentralized fine-grained access control mechanism that federates data providers and security issues using the notion of “trust domains”. In this paper we highlight the main features of the SIMDAT grid application and describe its security model in detail. 相似文献
233.
Abdelkarim Yelles Jacques Déverchère Rabah Bracène Pierre Strzerzynski Guillaume Bertrand Thierry Winter Pascal Le Roy Hamou Djellit 《Tectonophysics》2009,475(1):98-116
The Algiers region, northern Algeria, is known to be seismically active, with recurrent large (M>6) earthquakes. Because of the lack of high-resolution bathymetry, the offshore structures remained for a long time poorly known. Thanks to a new marine data base (MARADJA 2003 cruise), the offshore part of the margin is accurately mapped, and new active and recent structures are described. West of the bay of Algiers, the margin enlarges, forming the Khayr al Din bank, interpreted as a tilted block of the passive margin born during the opening of the Algero-Provençal basin. At the slope break, a 80 km-long fault-tip Quaternary fold, namely the Khayr al Din fault, extends at the foot of the margin off NW Algiers and represents the largest active structure of the coastal area, together with the Sahel anticline. We also map for the first time a set of overlapping, en echelon active folds in the upper part of the Khayr al Din bank, located off previously known active structures on land. Most of these faults represent actually a threat for the Algiers region in terms of seismic hazard but also geological hazards, such as tsunamis, as most of them depicts significant dimensions and slip rates. The highest long-term horizontal shortening rate is found on the Khayr al Din fault and is estimated at 0.5 ± 0.1 mm/yr, with a maximal magnitude of 7.3, which provides one of the highest seismogenic potential in the region.A new tectonic framework for the Algiers region is proposed, in which the main south-dipping offshore structure, of opposite vergence relative to most thrusts on land, appears to be nowadays the main driving fault system, as also found further east in the Boumerdès (M 6.8) 2003 rupture zone. The overall apparent pop-up structure of the recent and active faults may result from a progressive migration of the plate limit from the Late Miocene, north-dipping suture zone on land, to the Quaternary, south-dipping main Khayr al Din fault at sea, suggesting a process of subduction inception. 相似文献
234.
Impact of model simplifications on soil erosion predictions: application of the GLUE methodology to a distributed event‐based model at the hillslope scale 下载免费PDF全文
In this paper, we analyse how the performance and calibration of a distributed event‐based soil erosion model at the hillslope scale is affected by different simplifications on the parameterizations used to compute the production of suspended sediment by rainfall and runoff. Six modelling scenarios of different complexity are used to evaluate the temporal variability of the sedimentograph at the outlet of a 60 m long cultivated hillslope. The six scenarios are calibrated within the generalized likelihood uncertainty estimation framework in order to account for parameter uncertainty, and their performance is evaluated against experimental data registered during five storm events. The Nash–Sutcliffe efficiency, percent bias and coverage performance ratios show that the sedimentary response of the hillslope in terms of mass flux of eroded soil can be efficiently captured by a model structure including only two soil erodibility parameters, which control the rainfall and runoff production of suspended sediment. Increasing the number of parameters makes the calibration process more complex without increasing in a noticeable manner the predictive capability of the model. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
235.
The 1D version of the Model for Applications at Regional Scale is used to parameterize the effects of sea surface waves in
2D in a horizontally homogeneous offshore zone of the Iroise sea. Here we present the first simulation of the Iroise sea including
sea surface waves forcing, and more generally, the first study of a boundary layer including the Hasselmann force with a tidal
wave. We use a single equation turbulence closure based on a non-local diagnosis for energetic and dissipation length scales.
The turbulent energy flux at the surface due to whitecaps and the Hasselmann force induced by Stokes drift are assessed using
the whole sea surface waves spectrum given by the Wave Watch Third generation model. The ability of the parameterization to
reproduce surface currents over a period of 1 year (2007) is tested with high frequency radar using spectral and time-frequency
analysis. One problem with 1D modelling, corresponding to overestimation of current oscillating at inertial frequency is illustrated
by comparing 1D and 3D simulations. We found an overall improvement by including the Hasselmann force mainly within the bandwidth
of less than one cycle per day to one cycle per day for surface currents. Turbulence is induced by whitecaps decaying rapidly
below the ocean surface but the mixed layer below 40 m is deeper due to waves breaking on the sea surface. 相似文献
236.
Guillaume Morard Denis Andrault Nicolas Guignot Julien Siebert Gaston Garbarino Daniele Antonangeli 《Physics and Chemistry of Minerals》2011,38(10):767-776
High pressure melting behavior of three Fe-alloys containing 5 wt% Ni and (1) 10 wt% Si, (2) 15 wt% Si or (3) 12 wt% S was
investigated up to megabar pressures by in situ X-ray diffraction and laser-heated diamond anvil cell techniques. We observe
a decrease in melting temperature with increasing Si content over the entire investigated pressure range. This trend is used
to discuss the melting curve of pure Fe. Moreover, our measurements of eutectic melting in the Fe–Fe3S system show a change in slope around 50 GPa concomitant with the fcc–hcp phase transition in pure solid iron. Extrapolations
of our melting curve up to the core–mantle boundary pressure yield values of 3,600–3,750 K for the freezing temperature of
plausible outer core compositions. 相似文献
237.
Guillaume Pierre 《Geodinamica Acta》2013,26(1):45-54
RésuméLa question de la capture de la Meuse lorraine est abordée par le biais de l’étude des sables tertiaires qui jalonnent les plateaux de l’Ardenne méridionale. Toujours polygéniques, ces sables ont une histoire plus ou moins longue qui débute à l’Éocène où l’altération poussée du socle produit un épais manteau sableux. Certains gisements in situ fossilisés sont restés quasiment intacts (Régniowez) tandis que d’autres (Doisches) portent la marque de remaniements successifs (marins et/ou continentaux) qui se suivent jusqu’au Miocène sans que leur filiation avec le matériau d’origine, attestée par la nature de leurs barylites, ne se perde. Comme les sables fluviatiles miocènes (in fine) du plateau ardennais ne portent pas la signature minéralogique d’une Meuse lorraine, à l’inverse de la Traînée mosane (datée du Miocène moyen), la capture se trouve à la fois confirmée et datée. L’ancien réseau de la Meuse lorraine, quant à lui, n’a pu se mettre en place qu’après l’Oligocène, époque à laquelle un glacis incliné de l’Ardenne vers le Bassin parisien fonctionnait encore. © 2000 Éditions scientifiques et médicales Elsevier SAS 相似文献
238.
Confirming regional 1 cm differential geoid accuracy from airborne gravimetry: the Geoid Slope Validation Survey of 2011 总被引:3,自引:3,他引:0
Dru A. Smith Simon A. Holmes Xiaopeng Li Sébastien Guillaume Yan Ming Wang Beat Bürki Daniel R. Roman Theresa M. Damiani 《Journal of Geodesy》2013,87(10-12):885-907
A terrestrial survey, called the Geoid Slope Validation Survey of 2011 (GSVS11), encompassing leveling, GPS, astrogeodetic deflections of the vertical (DOV) and surface gravity was performed in the United States. The general purpose of that survey was to evaluate the current accuracy of gravimetric geoid models, and also to determine the impact of introducing new airborne gravity data from the ‘Gravity for the Redefinition of the American Vertical Datum’ (GRAV-D) project. More specifically, the GSVS11 survey was performed to determine whether or not the GRAV-D airborne gravimetry, flown at 11 km altitude, can reduce differential geoid error to below 1 cm in a low, flat gravimetrically uncomplicated region. GSVS11 comprises a 325 km traverse from Austin to Rockport in Southern Texas, and includes 218 GPS stations ( $\sigma _{\Delta h }= 0.4$ cm over any distance from 0.4 to 325 km) co-located with first-order spirit leveled orthometric heights ( $\sigma _{\Delta H }= 1.3$ cm end-to-end), including new surface gravimetry, and 216 astronomically determined vertical deflections $(\sigma _{\mathrm{DOV}}= 0.1^{\prime \prime })$ . The terrestrial survey data were compared in various ways to specific geoid models, including analysis of RMS residuals between all pairs of points on the line, direct comparison of DOVs to geoid slopes, and a harmonic analysis of the differences between the terrestrial data and various geoid models. These comparisons of the terrestrial survey data with specific geoid models showed conclusively that, in this type of region (low, flat) the geoid models computed using existing terrestrial gravity, combined with digital elevation models (DEMs) and GRACE and GOCE data, differential geoid accuracy of 1 to 3 cm (1 $\sigma )$ over distances from 0.4 to 325 km were currently being achieved. However, the addition of a contemporaneous airborne gravity data set, flown at 11 km altitude, brought the estimated differential geoid accuracy down to 1 cm over nearly all distances from 0.4 to 325 km. 相似文献
239.
Kristin Stock Vera Karasova Anne Robertson Guillaume Roger Mark Small Mohamed Bishr Jens Ortmann Tim Stojanovic Femke Reitsma Lukasz Korczynski Boyan Brodaric Zoe Gardner 《Transactions in GIS》2013,17(4):612-639
Current approaches to the discovery of scientific resources (publications, data sets and web services) are dominated by keyword search. These approaches do not allow scientists to search on the deeper semantics of scientific resources, or to discover resources on the basis of the scientific approaches taken. This article evaluates a user interface that allows users to discover scientific resources through structured knowledge in the form of ontologies describing the domain and the scientific knowledge inherent within the scientific resource, and also through informal user tags. These combined capabilities provide scientists with new and powerful options for resource discovery. A qualitative user evaluation explored how scientists felt about the approach for resource discovery in the context of their scientific work. The study showed that marine scientists were enthusiastic about the capabilities of such an approach and appreciated the ability to browse the visual structure of the knowledge and query on scientific method but, overall, preferred the use of tags over ontologies. The exploratory nature of the user study was used to identify future directions for such improvements. 相似文献
240.
Wei Yang Marc Jolivet Guillaume Dupont‐Nivet Zhaojie Guo Zhicheng Zhang Chaodong Wu 《Basin Research》2013,25(2):219-240
The tectonic evolution of the Tian Shan, as for most ranges in continental Asia is dominated by north‐south compression since the Cenozoic India‐Asia collision. However, precollision governing tectonic processes remain enigmatic. An excellent record is provided by thick Palaeozoic – Cenozoic lacustrine to fluvial depositional sequences that are well preserved in the southern margin of the Junggar Basin and exposed along a foreland basin associated to the Late Cenozoic rejuvenation of the Tian Shan ranges. U/Pb (LA‐ICP‐MS) dating of detrital zircons from 14 sandstone samples from a continuous series ranging in age from latest Palaeozoic to Quaternary is used to investigate changes in sediment provenance through time and to correlate them with major tectonic phases in the range. Samples were systematically collected along two nearby sections in the foreland basin. The results show that the detrital zircons are mostly magmatic in origin, with some minor input from metamorphic zircons. The U‐Pb detrital zircon ages range widely from 127 to 2856 Ma and can be divided into four main groups: 127–197 (sub‐peak at 159 Ma), 250–379 (sub‐peak at 318 Ma), 381–538 (sub‐peak at 406 Ma) and 543–2856 Ma (sub‐peak at 912 Ma). These groups indicate that the zircons were largely derived from the Tian Shan area to the south since a Late Carboniferous basin initiation. The provenance and basin‐range pattern evolution of the southern margin of Junggar Basin can be generally divided into four stages: (1) Late Carboniferous – Early Triassic basin evolution in a half‐graben or post‐orogenic extensional context; (2) From Middle Triassic to Upper Jurassic times, the southern Junggar became a passively subsiding basin until (3) being inverted during Lower Cretaceous – Palaeogene; (4) During the Neogene, a piedmont developed along the northern margin of the North Tian Shan block and Junggar Basin became a true foreland basin. 相似文献