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631.
Sub-surface precipitation of salts in supercritical seawater 总被引:2,自引:0,他引:2
Martin Hovland Tatyana Kuznetsova† Håkon Rueslåtten‡ Bjørn Kvamme† Hans Konrad Johnsen¶ Gunnar E. Fladmark§ Andreas Hebach† 《Basin Research》2006,18(2):221-230
Extremely low solubility of typical seawater salts within certain supercritical sections of their pressure–temperature composition space is a proven experimental fact. Its consequences are often referred to as either 'shock crystallization' or 'out-salting'. Our alternative model for the formation of salt deposits hypothesizes that high temperatures and pressures characteristic for the high heat-flow zones of tectonically active basins may bring submarine brines into the out-salting regions and result in the accumulation of geological-scale salt depositions.
To confirm the laboratory observations, molecular-scale simulations (molecular dynamics) have been employed to study structural changes in a model seawater system where temperature increased from ambient to near-critical and supercritical. Fluid properties and phase transition regions extracted from the simulations were then used as input parameters for a reservoir simulator program to model out-salting in a simple hydrothermal geological system. Both numerical simulations and laboratory experiments confirm that supercritical out-salting is a viable process of geological significance for the formation and accumulation of evaporites. We suggest two regions where hydrothermally associated salts may be depositing today: Atlantis II Deep, in the Red Sea, and Lake Asale, Ethiopia. 相似文献
To confirm the laboratory observations, molecular-scale simulations (molecular dynamics) have been employed to study structural changes in a model seawater system where temperature increased from ambient to near-critical and supercritical. Fluid properties and phase transition regions extracted from the simulations were then used as input parameters for a reservoir simulator program to model out-salting in a simple hydrothermal geological system. Both numerical simulations and laboratory experiments confirm that supercritical out-salting is a viable process of geological significance for the formation and accumulation of evaporites. We suggest two regions where hydrothermally associated salts may be depositing today: Atlantis II Deep, in the Red Sea, and Lake Asale, Ethiopia. 相似文献
632.
Zhixiong Shen Barbara Mauz Andreas Lang Jan Bloemendal John Dearing 《Quaternary Geochronology》2007,2(1-4):150-154
Optically stimulated luminescence of fine silt quartz was investigated to establish chronologies for lake sediments from the British Isles. Feldspar contamination and its potential effects on equivalent dose (De) determination were examined. A new feldspar contamination test based on the thermal quenching of quartz OSL and thermal assistance of feldspar OSL identified feldspar contamination in samples being treated for 20 min in 20% hydrofluoric acid. Feldspar component monitoring based on the post-IR OSL/OSL ratio was not sufficiently sensitive to monitor a feldspar component, but is a good indicator whether a standard SAR procedure can be applied successfully, despite the presence of feldspar. Based on these results we used a modified SAR protocol including a 100 s IRSL stimulation at 50 °C before OSL readout. This protocol could overcome any malign effects of feldspar even for a feldspar bearing polymineral sub-sample. 相似文献
633.
Andreas Dittrich Annette Schulte-Rentrop Michael Marek Volker Späth 《Acta Geophysica》2007,55(1):33-46
Flow in rivers and on floodplains is complex as it is affected by several interconnected factors such as topography, sediment
transport and vegetation characteristics. The resulting processes are explained by the measure “Hartheim” planned for retention
purposes at the Upper Rhine river. On the basis of existing formulas and instruments it is demonstrated that a good estimation
of the development of the measure is possible. The proposed procedure is a useful tool for estimating morphological developments
of restored river sections. 相似文献
634.
Coupling of groundwater and surface water at Lake Willersinnweiher: Groundwater modeling and tracer studies 总被引:1,自引:0,他引:1
635.
Andreas Müller 《Earth, Moon, and Planets》1983,28(1):23-27
The morphology of a series of highland volcanoes found on the floor of the crater Palisa is similar to that of mare volcanoes. The superposition of the cones and craters indicate that this volcano complex had a complex, multiphase history of development. A blanket of relatively dark ash, which is between 4 and 13 km wide, is observed surrounding these volcanoes. 相似文献
636.
Andreas Beyer Bishwajit Chakraborty Hans Werner Schenke 《International Journal of Earth Sciences》2007,96(1):11-20
In this study multibeam angular backscatter data acquired in the eastern slope of the Porcupine Seabight are analysed. Processing
of the angular backscatter data using the ‘NRGCOR’ software was made for 29 locations comprising different geological provinces
like: carbonate mounds, buried mounds, seafloor channels, and inter-channel areas. A detailed methodology is developed to
produce a map of angle-invariant (normalized) backscatter data by correcting the local angular backscatter values. The present
paper involves detailed processing steps and related technical aspects of the normalization approach. The presented angle-invariant
backscatter map possesses 12 dB dynamic range in terms of grey scale. A clear distinction is seen between the mound dominated
northern area (Belgica province) and the Gollum channel seafloor at the southern end of the site. Qualitative analyses of
the calculated mean backscatter values i.e., grey scale levels, utilizing angle-invariant backscatter data generally indicate
backscatter values are highest (lighter grey scale) in the mound areas followed by buried mounds. The backscatter values are
lowest in the inter-channel areas (lowest grey scale level). Moderate backscatter values (medium grey level) are observed
from the Gollum and Kings channel data, and significant variability within the channel seafloor provinces. The segmentation
of the channel seafloor provinces are made based on the computed grey scale levels for further analyses based on the angular
backscatter strength. Three major parameters are utilized to classify four different seafloor provinces of the Porcupine Seabight
by employing a semi-empirical method to analyse multibeam angular backscatter data. The predicted backscatter response which
has been computed at 20° is the highest for the mound areas. The coefficient of variation (CV) of the mean backscatter response
is also the highest for the mound areas. Interestingly, the slope value of the buried mound areas are found to be the highest.
However, the channel seafloor of moderate backscatter response presents the lowest slope and CV values. A critical examination
of the inter-channel areas indicates less variability within the estimated three parameters. Financial support of this study
was granted by the European Commission Fifth Framework Project GEOMOUND (contract no. EVK3-CT-1999-00016). 相似文献
637.
Sebastian Wagner Martin Widmann Julie Jones Torsten Haberzettl Andreas Lücke Christoph Mayr Christian Ohlendorf Frank Schäbitz Bernd Zolitschka 《Climate Dynamics》2007,29(4):333-355
This study investigates the atmospheric circulation in transient climate simulations with a coupled atmosphere–ocean general
circulation model (GCM) for the mid-Holocene (MH) period 7–4.5 ka BP driven with combinations of orbital, solar and greenhouse
gas forcings. The focus is on southern South America. Statistical downscaling models are derived from observational data and
applied to the simulations to estimate precipitation in south-eastern Patagonia during the MH. These estimates are compared
with lake level estimates for Laguna Potrok Aike (LPA) from sediments. Relative to pre-industrial conditions (i.e. 1550–1850),
which show extraordinarily high lake levels, the proxy-based reconstructed lake levels during the MH are lower. The downscaled
simulated circulation differences indicate higher LPA precipitation during the MH from March to August, higher annual means,
and reduced precipitation from September to February. Thus the reconstructed lower LPA lake levels can not be explained solely
by the simulated precipitation changes. Possible reasons for this discrepancy are discussed. Based on proxy data from southern
South America hypotheses have also been proposed on the latitudinal position of the southern hemispheric westerlies (SHWs).
In agreement with some of these hypotheses our simulations show an increased seasonal cycle of the latitudinal position of
the SHWs during the MH, which can be explained by the orbital forcing. The simulations also show stronger SHWs over southern
Patagonia during austral summer and weaker SHWs during winter. The downscaling model associates weaker SHWs with increased
precipitation in the LPA region. However, this relationship is only moderate, and therefore the downscaling model does not
support the assumption of a strong link between mean SHWs and precipitation over south-eastern Patagonia, which is the basis
of many proxy-based hypotheses about the SHWs. 相似文献
638.
Martin Piringer Sylvain Joffre Alexander Baklanov Andreas Christen Marco Deserti Koen De Ridder Stefan Emeis Patrice Mestayer Maria Tombrou Douglas Middleton Kathrin Baumann-Stanzer Aggeliki Dandou Ari Karppinen Jerzy Burzynski 《Boundary-Layer Meteorology》2007,124(1):3-24
The specific problems of determining and simulating the surface energy balance (SEB) and the mixing height (MH) over urban
areas are examined. The SEB and MH are critical components of algorithms and numerical models for the urban boundary layer,
though the constituent parts of the SEB and the MH are not routinely measured by national weather services. Parameterisations
are thus needed in applications. In this investigation, several recently developed algorithms and models for estimating the
SEB and MH were applied to new datasets and assessed. Results are discussed in terms of the need for spatial resolution and
the parameters needed to describe the urban atmosphere. Limitations of models are identified and recommendations for further
development and observations are given. Having identified gaps in knowledge, key findings from new urban experiments and numerical
modelling for the SEB and MH are given. The diurnal cycle for the SEB is significantly different from rural conditions—urban
heat storage is needed in urban parameterisations. The urban MH is increased over the rural MH, as shown by several numerical
schemes and careful sodar analyses. This work has been carried out within the COST-715 Action “Meteorology applied to urban
air pollution problems (1998–2004). COST 715 reached a consensus proposing representatively sited measurements of meteorological
parameters and turbulent fluxes above roof-tops, and recognised that such data are needed to improve numerical models of the
urban surface processes. 相似文献
639.
Hofmann Mandy Voigt Thomas Bittner Lucas Gärtner Andreas Zieger Johannes Linnemann Ulf 《International Journal of Earth Sciences》2018,107(3):913-932
International Journal of Earth Sciences - The Saxonian–Bohemian Cretaceous Basin (Elbsandsteingebirge, E Germany and Czech Republic, Elbtal Group) comprises Upper Cretaceous sedimentary rocks... 相似文献
640.
Linnemann Ulf Pidal Agustín Pieren Hofmann Mandy Drost Kerstin Quesada Cecilio Gerdes Axel Marko Linda Gärtner Andreas Zieger Johannes Ulrich Jens Krause Rita Vickers-Rich Patricia Horak Jana 《International Journal of Earth Sciences》2018,107(3):885-911
International Journal of Earth Sciences - In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such... 相似文献