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101.
Barth Alexander Troupin Charles Reyes Emma Alvera-Azcárate Aida Beckers Jean-Marie Tintoré Joaquín 《Ocean Dynamics》2021,71(3):293-308
Ocean Dynamics - DIVAnd (Data-Interpolating Variational Analysis, in n-dimensions) is a tool to interpolate observations on a regular grid using the variational inverse method. We have extended... 相似文献
102.
Comparison between satellite and in situ sea surface temperature data in the Western Mediterranean Sea 总被引:1,自引:1,他引:0
Aida Alvera-Azcárate Charles Troupin Alexander Barth Jean-Marie Beckers 《Ocean Dynamics》2011,61(6):767-778
A comparison between in situ and satellite sea surface temperature (SST) is presented for the Western Mediterranean Sea during
1999. Several international databases are used to extract in situ data (World Ocean Database, MEDAR/Medatlas, Coriolis Data
Center, International Council for the Exploration of the Sea and International Comprehensive Ocean-Atmosphere Data Set). The
in situ data are classified into different platforms or sensors (conductivity–temperature–depth, expendable bathythermographs,
drifters, bottles, and ships), in order to assess the relative accuracy of these type of data with respect to Advanced Very
High Resolution Radiometer SST satellite data. It is shown that the results of the error assessment vary with the sensor type,
the depth of the in situ measurements, and the database used. Ship data are the most heterogeneous data set, and therefore
present the largest differences with respect to in situ data. A cold bias is detected in drifter data. The differences between
satellite and in situ data are not normally distributed. However, several analysis techniques, as merging and data assimilation,
usually require Gaussian-distributed errors. The statistics obtained during this study will be used in future work to merge
the in situ and satellite data sets into one unique estimation of the SST. 相似文献
103.
K. Abraham A. Hofmann S.F. Foley D. Cardinal C. Harris M.G. Barth L. André 《Earth and Planetary Science Letters》2011,301(1-2):222-230
Silica alteration zones and cherts are a conspicuous feature of Archaean greenstone belts worldwide and provide evidence of extensive mobilisation of silica in the marine environment of the early Earth. In order to understand the process(es) of silicification we measured the silicon and oxygen isotope composition of sections of variably silicified basalts and overlying bedded cherts from the Theespruit, Hooggenoeg and Kromberg Formations of the Barberton Greenstone Belt, South Africa.The δ30Si and δ18O values of bulk rock increase with increasing amount of silicification from unsilicified basalts (?0.64‰ < δ30Si < ?0.01‰ and + 8.6‰ < δ18O < + 11.9‰) to silicified basalts (δ30Si and δ18O values as high as + 0.81‰ and + 15.6‰, respectively). Cherts generally have positive isotope ratios (+ 0.21‰ < δ30Si < + 1.05‰ and + 10.9 < δ18O < + 17.1), except two cherts, which have negative δ30Si values, but high δ18O (up to + 19.5‰).The pronounced positive correlations between δ30Si, δ18O and SiO2 imply that the isotope variation is driven by the silicification process which coevally introduced both 18O and 30Si into the basalts. The oxygen isotope variation in the basalts from about 8.6‰ to 15.6‰ is likely to represent temperature-dependent isotope fractionation during alteration. Our proposed model for the observed silicon isotope variation relies on a temperature-controlled basalt dissolution vs. silica deposition process. 相似文献
104.
The stable water isotopes, 2H and 18O, can be useful environmental tracers for quantifying snow contributions to streams and aquifers, but characterizing the isotopic signatures of bulk snowpacks is challenging because they can be highly variable across the catchment landscape. In this study, we investigate one major source of isotopic heterogeneity in snowpacks: the influence of canopy cover. We measured amounts and isotopic compositions of bulk snowpack, throughfall, and open precipitation during seven campaigns in mid-winter 2018 along forest-grassland transects at three different elevations (1196, 1297, and 1434 m above sea level) in a pre-Alpine catchment in Switzerland. Snowpack storages under forest canopies were 67 to 93% less than in adjacent open grasslands. On average, the water isotope ratios were higher in the snowpacks under forest canopy than in open grasslands (by 13.4 ‰ in δ2H and 2.3 ‰ in δ18O). This isotopic difference mirrored the higher isotope values in throughfall compared with open snowfall (by 13.5 ‰ in δ2H and 2.2 ‰ in δ18O). Although this may suggest that most of the isotopic differences in snowpacks under forests versus in open grasslands were attributable to canopy interception effects, the temporal evolution of snowpack isotope ratios indicated preferential effluxes of lighter isotopes as energy inputs increased and the snowpack ripened and melted. Understanding these effects of forest canopy on bulk snowpack snow water equivalent and isotopic composition are useful when using isotopes to infer snowmelt processes in landscapes with varying forest cover. 相似文献
105.
Andreas Barth 《Journal of Seismology》2014,18(3):605-615
On February 12, 2013 the Democratic People’s Republic of Korea (DPRK) carried out an announced nuclear test, which was the third after tests conducted in 2006 and 2009. An important task in discriminating a man-made explosion and a natural tectonic earthquake is the analysis of seismic waveforms. To determine the isotropic and non-isotropic characteristics of the detonation source, I invert long-period seismic data for the full seismic moment tensor to match the observed seismic signals by synthetic waveforms based on a 3D Earth model. Here, I show that the inversion of long-period seismic data of the 2013 test reveals a clear explosive (isotropic) component combined with a significant release of shear energy by the double-couple part of the moment tensor. While the isotropic part of the nuclear test in 2009 was similar to that in 2013, the double-couple part was lower by a factor of 0.55 compared to the explosion in 2013. Moreover, the ratio of the isotropic seismic moments of the 2013 and 2009 nuclear tests is 1.4?±?0.1 and lower than published estimations of the yield ratio, which indicates the importance of considering the release of shear energy. The determined orientation of the double-couple fault plane is parallel to the dominating geologic fault structures NNE-SSW to NE-SW, but the calculated normal faulting mechanism does not correspond to the general tectonic strike-slip regime. Thus, explanations for the enhanced release of shear energy might be induced dip-slip motion pre-stressed by the previous test or near source damaging effects due to a changed containment of the nuclear explosion. 相似文献
106.
We present new geochemical analyses of minerals and whole rocks for a suite of mafic rocks from the crustal section of the
Othris Ophiolite in central Greece. The mafic rocks form three chemically distinct groups. Group 1 is characterized by N-MORB-type
basalt and basaltic andesite with Na- and Ti-rich clinopyroxenes. These rocks show mild LREE depletion and no HFSE anomalies,
consistent with moderate degrees (~15%) of anhydrous partial melting of depleted mantle followed by 30–50% crystal fractionation.
Group 2 is represented by E-MORB-type basalt with clinopyroxenes with higher Ti contents than Group 1 basalts. Group 2 basalts
also have higher concentrations of incompatible trace elements with slightly lower HREE contents than Group 1 basalts. These
chemical features can be explained by ~10% partial melting of an enriched mantle source. Group 3 includes high MgO cumulates
with Na- and Ti-poor clinopyroxene, forsteritic olivine, and Cr-rich spinel. The cumulates show strong depletion of HFSE,
low HREE contents, and LREE enrichments. These rocks may have formed by olivine accumulation from boninitic magmas. The petrogenesis
of the N-MORB-type basalts and basaltic andesites is in excellent agreement with the melting conditions inferred from the
MOR-type peridotites in Othris. The occurrence of both N- and E-MORB-type lavas suggests that the mantle generating the lavas
of the Othris Ophiolite must have been heterogeneous on a comparatively fine scale. Furthermore, the inferred parental magmas
of the SSZ-type cumulates are broadly complementary to the SSZ-type peridotites found in Othris. These results suggest that
the crustal section may be genetically related to the mantle section. In the Othris Ophiolite mafic rocks recording magmatic
processes characteristic both of mid-ocean ridges and subduction zones occur within close spatial association. These observations
are consistent with the formation of the Othris Ophiolite in the upper plate of a newly created intra-oceanic subduction zone.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
107.
Modelling groundwater over-extraction in the southern Jordan Valley with scarce data 总被引:1,自引:0,他引:1
To deal with the challenge of groundwater over-extraction in arid and semi-arid environments, it is necessary to establish management strategies based on the knowledge of hydrogeological conditions, which can be difficult in places where hydrogeological data are dispersed, scarce or present potential misinformation. Groundwater levels in the southern Jordan Valley (Jordan) have decreased drastically in the last three decades, caused by over-extraction of groundwater for irrigation purposes. This study presents a local, two-dimensional and transient numerical groundwater model, using MODFLOW, to characterise the groundwater system and the water balance in the southern Jordan Valley. Furthermore, scenarios are simulated regarding hydrological conditions and management options, like extension of arable land and closure of illegal wells, influencing the projection of groundwater extraction. A limited dataset, literature values, field surveys, and the ‘crop water-requirement method’ are combined to determine boundary conditions, aquifer parameters, and sources and sinks. The model results show good agreement between predicted and observed values; groundwater-level contours agree with the conceptual model and expected flow direction, and, in terms of water balance, flow volumes are in accordance with literature values. Average annual water consumption for irrigation is estimated to be 29 million m3 and simulation results show that a reduction of groundwater pumping by 40% could recover groundwater heads, reducing the water taken from storage. This study presents an example of how to develop a local numerical groundwater model to support management strategies under the condition of data scarcity. 相似文献
108.
Analysis of 18 observations of the limb intensity profile of the CO Cameron bands in the Martian airglow shows that the equivalent subsolar zenith intensity, ICAM, is related to the Ottawa 10.7 cm radio flux index, F10.7, by the expression ICAM = 0.062(74 + F10.7)kR, with a correlation coefficient of 0.80. Comparison of averaged limb intensities of the CO2+ doublet and the Cameron bands on four favorable occasions is consistent with the intensities being directly proportional, in the ratio 0.24:1. The mean of 18 Cameron band topside scale heights is 17.8 km, corresponding to an exospheric temperature of 325°K, and the largest and smallest values observed differ by 9.5 km. These observations are in accord with theoretical predictions within the uncertainties in the latter. However, the solar EUV flux used in these predictions is a factor of at least two too weak to produce the electron densities measured by the S-band occultation experiment. 相似文献
109.
Edward G. Patton Kenneth J. Davis Mary C. Barth Peter P. Sullivan 《Boundary-Layer Meteorology》2001,100(1):91-129
A large-eddy simulation is modified to include multiple scalars emitted by a plant canopy. Each of these scalars is subjected to varying rates of chemical loss. Presented is a detailed comparison between conservedspecies and species undergoing first- and second-order chemical loss.Profiles of mean mixing ratio, mixing-ratio variance and vertical mixing-ratio flux reveal the influence of chemical reactivity. Distribution of thescalar source through the depth of the canopy is shown to locally reducethe reaction rate for second-order species. Transport efficiencies, diffusioncoefficients, and mean source heights also exhibit chemical dependencies.Budgets of mixing-ratio variance and flux elucidate the mechanisms throughwhich chemistry modifies each. Instantaneous fields show the existence ofintermittently occurring coherent structures that are thought to enhancespecies segregation. 相似文献
110.