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1.
Robert van Geldern Peter Schulte Michael Mader Alfons Baier Johannes A.C. Barth Tobias R. Juhlke Kern Lee 《水文研究》2018,32(7):891-903
Karst areas and their catchments pose a great challenge for protection because fast conduit flow results in low natural attenuation of anthropogenic contaminants. Studies of the hydrochemistry of karst sources and river solutes are an important tool for securing and managing water resources. A study of the geochemical downriver evolution of the Wiesent River and its tributaries, located in a typical karst terrain, revealed unexpected downstream decreases of nitrate with maximum mean values of 30 mg/L at the source to minimum values of 18 mg/L near the river mouth. This trend persisted over the length of the river even though increased agricultural activities are evident in the downstream section of the catchment. This pattern is caused by fertilizer inputs via diffusive and fast conduits flow from karst lithology in the upstream area that may have reached the river's source even from beyond the hydrological catchment boundaries. Further downstream, these influences became diluted by tributary inputs that drain subcatchments dominated by claystone and sandstone lithologies that increased potassium and sulphate concentrations. Our findings indicate that bedrock geology remains the dominant control on the major ion chemistry of the Wiesent River and that agricultural influences are strongest near the headwaters despite increased land use further downstream, due to long‐term storage and accumulation in karst aquifers. This feature may not be unique to the Wiesent River system, as carbonates cover significant portions of the Earth's surface and subsequent work in other river systems could establish whether such patterns are ubiquitous worldwide. 相似文献
2.
Alicja Wudarska Ewa Saby Michael Wiedenbeck Jaime D. Barnes Magali Bonifacie Neil C. Sturchio Grard Bardoux Frdric Couffignal Johannes Glodny Linnea Heraty Timm John Christof Kusebauch Sathish Mayanna Franziska D. H. Wilke Ewa Deput 《Geostandards and Geoanalytical Research》2021,45(1):121-142
Here we report on a set of six apatite reference materials (chlorapatites MGMH#133648, TUBAF#38 and fluorapatites MGMH#128441A, TUBAF#37, 40, 50) which we have characterised for their chlorine isotope ratios; these RMs span a range of Cl mass fractions within the apatite Ca10(PO4)6(F,Cl,OH)2 solid solution series. Numerous apatite specimens, obtained from mineralogical collections, were initially screened for 37Cl/35Cl homogeneity using SIMS followed by δ37Cl characterisation by gas source mass spectrometry using both dual‐inlet and continuous‐flow modes. We also report major and key trace element compositions as determined by EPMA. The repeatability of our SIMS results was better than ± 0.10‰ (1s) for the five samples with > 0.5 % m/m Cl and ± 0.19‰ (1s) for the low Cl abundance material (0.27% m/m). We also observed a small, but significant crystal orientation effect of 0.38‰ between the mean 37Cl/35Cl ratios measured on three oriented apatite fragments. Furthermore, the results of GS‐IRMS analyses show small but systematic offset of δ37ClSMOC values between the three laboratories. Nonetheless, all studied samples have comparable chlorine isotope compositions, with mean 103δ37ClSMOC values between +0.09 and +0.42 and in all cases with 1s ≤ ± 0.25. 相似文献
3.
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5.
Mohammad J. Tourian Johannes Riegger Nico Sneeuw Balaji Devaraju 《Studia Geophysica et Geodaetica》2011,55(4):627-640
Gravity measurements within the Gravity Recovery and Climate Experiment (GRACE) provide a direct measure of monthly changes
in mass over the Earth’s land masses. As such changes in mass mainly correspond to water storage changes, these measurements
allow to close the continental water balance on large spatial scales and on a monthly time scale within the respective error
bounds. When quantifying uncertainties, positive and negative peaks are detected in GRACE aggregated monthly time series (from
different data providers) that do not correspond to hydrological or hydro-meteorological signals. These peaks must be interpreted
as outliers, which carry the danger of signal degradation. In this paper an algorithm is developed to identify outliers and
replace them with hydrologically plausible values. The algorithm is based on a statistical approach in which hydrological
and hydro-meteorological signals are used to control the algorithm. The procedure of outlier detection is verified by evaluating
catchment based aggregated GRACE monthly signals with ground truth from hydrology and hydro-meteorological signals. The results
show improvement in the correlation of GRACE versus hydrometeorological and hydrological signals in most catchments. Also,
the noise level is significantly reduced over 255 largest catchments. 相似文献
6.
Cross-correlation analysis was applied to events in the 2003 Lefkada Island, Greece, sequence in order to identify clusters
of seismicity within the extensive aftershock sequence along a fault zone of approximately 100 km length. Data from the small-aperture
TRISAR array, covering the first 2 days of aftershock activity, were used. Array-based waveform correlation has a great advantage
over single channel correlation analysis in that the validity of waveform matches with relatively low correlation coefficients
can be examined by checking the alignment of correlation traces on the different channels. The length of the fault zone leads
inevitably to a great diversity in the waveforms, although a small number of clusters of very similar events emerge from the
TRISAR data. Events which the correlation analysis had placed within the same cluster were listed in the ISC Bulletin with
separations of up to tens of kilometres. This made it necessary to check the validity of the TRISAR clusters by applying the
same procedure independently to the three-component stations of the National Seismographic Network of the National Observatory
of Athens, located at local to regional distances from the aftershock area. Results suggest that array-based waveform correlation
provides a robust tool both for identifying event clusters within large aftershock areas and for identifying situations in
which bulletin event location estimates need re-evaluation. 相似文献
7.
The IVS Intensive sessions are single-baseline, 1-h VLBI sessions carried out everyday in order to determine Universal Time
(UT1). We investigate different possibilities to improve the results of such sessions. We do this investigation by extracting
2-h single-baseline sessions from the CONT08 data set. These are analysed like normal Intensives, and the results are compared
to the results of the analysis of the full CONT08 data set. We find that tropospheric asymmetry is the major error source
for the single-baseline sessions. It is possible to improve the accuracy of the estimated UT1 either by using accurate a priori
tropospheric gradients or by estimating gradients in the data analysis. 相似文献
8.
Claire Granier Bertrand Bessagnet Tami Bond Ariela D��Angiola Hugo Denier van der Gon Gregory J. Frost Angelika Heil Johannes W. Kaiser Stefan Kinne Zbigniew Klimont Silvia Kloster Jean-Fran?ois Lamarque Catherine Liousse Toshihiko Masui Frederik Meleux Aude Mieville Toshimasa Ohara Jean-Christophe Raut Keywan Riahi Martin G. Schultz Steven J. Smith Allison Thompson John van Aardenne Guido R. van der Werf Detlef P. van Vuuren 《Climatic change》2011,109(1-2):163-190
Several different inventories of global and regional anthropogenic and biomass burning emissions are assessed for the 1980?C2010 period. The species considered in this study are carbon monoxide, nitrogen oxides, sulfur dioxide and black carbon. The inventories considered include the ACCMIP historical emissions developed in support of the simulations for the IPCC AR5 assessment. Emissions for 2005 and 2010 from the Representative Concentration Pathways (RCPs) are also included. Large discrepancies between the global and regional emissions are identified, which shows that there is still no consensus on the best estimates for surface emissions of atmospheric compounds. At the global scale, anthropogenic emissions of CO, NOx and SO2 show the best agreement for most years, although agreement does not necessarily mean that uncertainty is low. The agreement is low for BC emissions, particularly in the period prior to 2000. The best consensus is for NOx emissions for all periods and all regions, except for China, where emissions in 1980 and 1990 need to be better defined. Emissions of CO need better quantification in the USA and India for all periods; in Central Europe, the evolution of emissions during the past two decades needs to be better determined. The agreement between the different SO2 emissions datasets is rather good for the USA, but better quantification is needed elsewhere, particularly for Central Europe, India and China. The comparisons performed in this study show that the use of RCP8.5 for the extension of the ACCMIP inventory beyond 2000 is reasonable, until more global or regional estimates become available. Concerning biomass burning emissions, most inventories agree within 50?C80%, depending on the year and season. The large differences between biomass burning inventories are due to differences in the estimates of burned areas from the different available products, as well as in the amount of biomass burned. 相似文献
9.
This paper identifies a critical systematic error in greenhouse gas accounting in renewable biomass systems. While CO2 emissions from renewable biomass energy systems are generally considered to have a net impact of 0, no similar adjustment
is made for carbon-based products of incomplete combustion, such as methane, in renewable systems. This results in an under-
or overestimation of the impact of CH4 by 12.3% and CO by ∼478% in renewable systems. This error is propagated both in scientific studies and in carbon accounting
policies. We advocate first for full-carbon accounting of biomass-derived emissions, but also provide adjusted global warming
impacts for emissions from proven renewable systems. 相似文献
10.
The simulation of Arctic clouds and their influence on the winter surface temperature in present-day climate in the CMIP3 multi-model dataset 总被引:1,自引:1,他引:0
We investigate the influence of clouds on the surface energy budget and surface temperature in the sea-ice covered parts of the ocean north of the Arctic circle in present-day climate in nine global climate models participating in the Coupled Model Intercomparison Project phase 3, CMIP3. Monthly mean simulated surface skin temperature, radiative fluxes and cloud parameters are evaluated using retrievals from the extended AVHHR Polar Pathfinder (APP-x) product. We analyzed the annual cycle but the main focus is on the winter, in which large parts of the region experience polar night. We find a smaller across-model spread as well as better agreement with observations during summer than during winter in the simulated climatological annual cycles of total cloudiness and surface skin temperature. The across-model spread in liquid and ice water paths is substantial during the whole year. These results qualitatively agree with earlier studies on the present-day Arctic climate in GCMs. The climatological ensemble model mean annual cycle of surface cloud forcing shows good agreement with observations in summer. However, during winter the insulating effect of clouds tends to be underestimated in models. During winter, most of the models as well as the observations show higher monthly mean total cloud fractions, associated with larger positive surface cloud forcing. Most models also show good correlation between the surface cloud forcing and the vertically integrated ice and liquid cloud condensate. The wintertime ensemble model mean total cloud fraction (69%) shows excellent agreement with observations. The across-model spread in the winter mean cloudiness is substantial (36?C94%) however and several models significantly underestimate the cloud liquid water content. If the two models not showing any relationship between cloudiness and surface cloud forcing are disregarded, a tentative across-model relation exists, in such a way that models that simulate large winter mean cloudiness also show larger surface cloud forcing. Even though the across-model spread in wintertime surface cloud forcing is large, no clear relation to the surface temperature is found. This indicates that other processes, not explicitly cloud related, are important for the simulated across-model spread in surface temperature. 相似文献