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61.
We discuss the point spread function for the Spectro instrument based on realistic effects of the time delayed integration,
transverse image motion and pixelization, but assuming rather small wave front errors. Stars brighter than 10 mag, which will
saturate the CCD, may be observed photometrically using the image wings, but the central wavelengths will be slightly shifted
towards the red.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
62.
Hanna Hadler Andreas Vött Timo Willershäuser Dennis Wilken Ruth Blankenfeldt Claus von Carnap-Bornheim Kurt Emde Peter Fischer Ulf Ickerodt Stefanie Klooß Bente Majchczack Lea Obrocki Wolfgang Rabbel 《地球表面变化过程与地形》2021,46(15):3228-3251
In ad 1362, a major storm surge drowned wide areas of cultivated medieval marshland along the north-western coast of Germany and turned them into tidal flats. This study presents a new methodological approach for the reconstruction of changing coastal landscapes developed from a study site in the Wadden Sea of North Frisia. Initially, we deciphered long-term as well as event-related short-term geomorphological changes, using a geoscientific standard approach of vibracoring, analyses of sedimentary, geochemical and microfaunal palaeoenvironmental parameters and radiocarbon dating. In a next step, Direct Push (DP)-based Cone Penetration Testing (CPT) and the Hydraulic Profiling Tool (HPT) were applied at vibracore locations to obtain in situ high-resolution stratigraphic data. In a last step, multivariate linear discriminant analysis (LDA) was successfully applied to efficiently identify different sedimentary facies (e.g., fossil marsh or tidal flat deposits) from the CPT and HPT test dataset, to map the facies' lateral distribution, also in comparison to reflection seismic measurements and test their potential to interpolate the borehole and CPT/HPT data. The training dataset acquired for the key site from coring and DP sensing finally allows an automated facies classification of CPT/HPT data obtained elsewhere within the study area. The new methodological approach allowed a detailed reconstruction of the local coastal landscape development in the interplay of natural marsh formation, medieval land reclamation and storm surge-related land losses. 相似文献
63.
Sergio-Raúl Rodríguez Claus Siebe Jean-Christophe Komorowski Michael Abrams 《Journal of Volcanology and Geothermal Research》2002,113(1-2)
The study area is located in the east part of the Trans-Mexican Volcanic Belt, in the Las Cumbres Volcanic Complex (LCVC) which lies between two large stratovolcanoes: Pico de Orizaba (5700 m a.s.l.) to the south, and Cofre de Perote (4200 m a.s.l.) to the NNE. The most conspicuous structure of the LCVC is a 4-km-diameter circular crater with a dacitic dome in the center, which constitutes the remains of a destroyed stratovolcano.The Quetzalapa Pumice (QP) was produced by a plinian eruption that was dated by the 14C method at 20 000 yr. BP. The eruptive sequence consists predominantly of pumice fall deposits and scarce intra-plinian pyroclastic flow deposits, which crop out on the west flank of the LCVC. The absence of post-plinian ignimbrite deposits is striking.The deposits are well sorted, clast-supported with reverse grading at the base, with a medium to high accessory lithics content. The maximum average thickness of the deposit in the proximal areas is about 15 m and has been divided into three members: the Basal Member (BM), 2 m thick with four submembers (BMf1, BMf2, BMf3, and BMafl), the Intermediate Member (IM), 10 m thick with two submembers (IMpf and IMaf), and the Upper Member (UM), 3 m thick with four submembers (UMpl, UMsdf, UMwaf, and UMpls).The predominant component of the fall deposits is a white, highly vesiculated pumice with 71% SiO2 content. Plagioclase is the most abundant mineral followed by 1–3-mm-long biotite phenocrysts. The accessory lithics are lavas mostly of andesitic composition. Their abundance increases toward the uppermost levels of the sequence.We calculate a minimum volume of 8.4 km3 (2.22 km3 dense rock equivalent), for the entire QP deposit. Isopach and isopleth maps show that the IM deposit has an elongated distribution with a NNE–SSW direction, whereas the UM deposit has a circular distribution.We estimate a maximum eruptive column height for the IM of 20 km. Field studies and isopach and isopleth maps indicate that the eruptive column was affected by a strong wind.Previous studies located the QP source in the Las Cumbres crater. However, based on the isopach and isopleth distribution, and the lack of pumice fall deposits inside the Las Cumbres crater, we consider that the QP emission center is located on the west flank of the LCVC, and was buried by its own pumice fall deposits. It coincides with an explosion crater called La Capilla formed during the closing phase of the QP eruption.A ‘pumice fountain’ model is proposed to explain the observed sequence of deposits. According to this model, the material was emitted through a ‘hose-type’ conduit during a monogenetic eruption of rhyolitic composition. This kind of volcanic activity is not extensively reported in the literature. 相似文献
64.
Matteo Picozzi Claus Milkereit Kevin Fleming Eser Çakti Jochen Zschau 《Journal of Seismology》2011,15(4):557-578
A seismic antenna approach based on the generalized zero-lag cross-correlation method for rapid earthquake localization is
proposed. This method is intended to be applied primarily for early warning, whenever the epicentre-to-target distances guarantee
enough lead-time, rapid response purposes, and for those circumstances when a seismogenic area is not directly accessible
with seismic stations or/and a network of instruments is concentrated within the area to be warned. The procedure we propose
aims to provide useful information for magnitude determination and shake-maps generation. Indeed, it relies only on the first
P-wave triggered arrivals from seismic stations, and is designed to work in real-time for the localization of events occurring
outside of the network, that is, under conditions that might be detrimental to standard localization approaches. The procedure
can by summarized by a few preliminary pre-seismic and real-time co-seismic steps. In the pre-seismic time-frame, for the
cases where a large and dense network exists, waiting for all stations to trigger could dramatically reduce the available
lead-time for the warning. Therefore, in such cases, the network could profitably be divided into sub-arrays, while also taking
advantage of available earthquake recordings or simulated data sets. During the co-seismic time-frame, the main operations
are: (1) individual on-site triggering by the P-wave of the seismic stations (e.g. by a STA/LTA algorithm); (2) real-time
communication of key parameters (e.g. P-wave arrival time, and signal quality) to a main centre by SMS/WLAN; (3) setup of
a pseudo data set, composed by a Gaussian function centred at the P-time, and with a bell width that can be set up proportional
to the trigger signal-to-noise ratio (SNR); (4) calculation of a coherency map for the sub-array with triggered stations (preliminary
sub-array location); and (5) stacking of coherency maps from the different sub-arrays (final location). By the stack of coherency
maps estimated by the different sub-arrays in the last step of the procedure, the epicentral area’s location may be better
constrained. This innovative approach for rapid localization was applied to both synthetic data, and real observations of
two small earthquakes that occurred in the Marmara Sea, Turkey, which were recorded by the Istanbul Earthquake Rapid Response
System. 相似文献
65.
Weighted linear combination is a multi-criteria decision analysis technique that can be used by decision-makers to select an optimal location from a collection of alternative locations. Its local form takes into account the range of attribute values within a user-defined neighbourhood in accordance with the range-sensitivity principle. This research explores locally weighted linear combination in a vector-based geographic information system. A custom application in ArcGIS 10 allows the user to select a neighbourhood definition from a standard set including contiguity, distance, and k-nearest neighbours, for which local weights are generated. A case study on vulnerability to heat-related illness in Toronto is used to illustrate the technique. The impact of local weighting on the heat vulnerability index is examined using visual analysis of the spatial patterns of heat vulnerability under the global and local approaches, as well as the sensitivity of the local approach to the selected neighbourhood definition. A trade-off analysis of the local weights is also presented. The combination of socio-demographic and environmental determinants in a locally weighted index results in patterns of heat vulnerability that could support targeted hot weather response at a micro-geographic level within urban neighbourhoods. 相似文献
66.
Claus Gebhardt Jean-Raymond Bidlot Johannes Gemmrich Susanne Lehner Andrey Pleskachevsky Wolfgang Rosenthal 《Ocean Dynamics》2016,66(6-7):839-852
This article investigates the penetration of ocean waves into the marginal ice zone (MIZ), observed by satellite, and likewise provides a basis for the future cross-validation of respective models. To this end, synthetic aperture radar images from the TerraSAR-X satellite (TS-X) and numerical simulations of the European Centre for Medium-Range Weather Forecasts (ECMWF) are used. The focus is an event of swell waves, developed during a storm passage in the Atlantic, penetrating deeply into the MIZ off the coast of Eastern Greenland in February 2013. The TS-X scene which is the basis for this investigation extends from the ice-free open ocean to solid ice. The variation of the peak wavelength is analysed and potential sources of variability are discussed. We find an increase in wavelength which is consistent with the spatial dispersion of deep water waves, even within the ice-covered region. 相似文献
67.
Thierry Appourchaux Raymond Burston Yanbei Chen Michael Cruise Hansjörg Dittus Bernard Foulon Patrick Gill Laurent Gizon Hugh Klein Sergei Klioner Sergei Kopeikin Hans Krüger Claus Lämmerzahl Alberto Lobo Xinlian Luo Helen Margolis Wei-Tou Ni Antonio Pulido Patón Qiuhe Peng Achim Peters Ernst Rasel Albrecht Rüdiger Étienne Samain Hanns Selig Diana Shaul Timothy Sumner Stephan Theil Pierre Touboul Slava Turyshev Haitao Wang Li Wang Linqing Wen Andreas Wicht Ji Wu Xiaomin Zhang Cheng Zhao 《Experimental Astronomy》2009,23(2):491-527
ASTROD I is a planned interplanetary space mission with multiple goals. The primary aims are: to test general relativity with
an improvement in sensitivity of over three orders of magnitude, improving our understanding of gravity and aiding the development
of a new quantum gravity theory; to measure key solar system parameters with increased accuracy, advancing solar physics and
our knowledge of the solar system; and to measure the time rate of change of the gravitational constant with an order of magnitude
improvement and the anomalous Pioneer acceleration, thereby probing dark matter and dark energy gravitationally. It is an
international project, with major contributions from Europe and China and is envisaged as the first in a series of ASTROD
missions. ASTROD I will consist of one spacecraft carrying a telescope, four lasers, two event timers and a clock. Two-way,
two-wavelength laser pulse ranging will be used between the spacecraft in a solar orbit and deep space laser stations on Earth,
to achieve the ASTROD I goals. A second mission, ASTROD (ASTROD II) is envisaged as a three-spacecraft mission which would
test General Relativity to 1 ppb, enable detection of solar g-modes, measure the solar Lense–Thirring effect to 10 ppm, and
probe gravitational waves at frequencies below the LISA bandwidth. In the third phase (ASTROD III or Super-ASTROD), larger
orbits could be implemented to map the outer solar system and to probe primordial gravitational-waves at frequencies below
the ASTROD II bandwidth.
相似文献
Wei-Tou NiEmail: |
68.
Wind-Direction Effects on Urban-Type Flows 总被引:2,自引:2,他引:0
Jean Claus O. Coceal T. Glyn Thomas S. Branford S. E. Belcher Ian P. Castro 《Boundary-Layer Meteorology》2012,142(2):265-287
Practically all extant work on flows over obstacle arrays, whether laboratory experiments or numerical modelling, is for cases
where the oncoming wind is normal to salient faces of the obstacles. In the field, however, this is rarely the case. Here,
simulations of flows at various directions over arrays of cubes representing typical urban canopy regions are presented and
discussed. The computations are of both direct numerical simulation and large-eddy simulation type. Attention is concentrated
on the differences in the mean flow within the canopy region arising from the different wind directions and the consequent
effects on global properties such as the total surface drag, which can change very significantly—by up to a factor of three
in some circumstances. It is shown that for a given Reynolds number the typical viscous forces are generally a rather larger
fraction of the pressure forces (principally the drag) for non-normal than for normal wind directions and that, dependent
on the surface morphology, the average flow direction deep within the canopy can be largely independent of the oncoming wind
direction. Even for regular arrays of regular obstacles, a wind direction not normal to the obstacle faces can in general
generate a lateral lift force (in the direction normal to the oncoming flow). The results demonstrate this and it is shown
how computations in a finite domain with the oncoming flow generated by an appropriate forcing term (e.g. a pressure gradient)
then lead inevitably to an oncoming wind direction aloft that is not aligned with the forcing term vector. 相似文献
69.
70.
Werner Conrad Karel Diviš Claus Elstner Rezensent Z. Šimon 《Studia Geophysica et Geodaetica》1979,23(2):114-121
Summary Results of gravity measurements performed in 1977 along a WE-profile situated in the GDR area are discussed. Systematic influences caused by the variations of the hydrologic conditions in the local regions of the observation points reach 100 nm s–2. From the results of the yearly repeated gravity measurements (1970/77) a mean yearly gravity variation of about 20 nm s–2 a–1 was calculated for the sedimentary eastern part of the profile. 相似文献