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141.
This paper reports the application of weights-of-evidence, artificial neural networks, and fuzzy logic spatial modeling techniques
to generate prospectivity maps for gold mineralization in the neighborhood of the Amapari Au mine, Brazil. The study area
comprises one of the last Brazilian mineral exploration frontiers. The Amapari mine is located in the Maroni-Itaicaiúnas Province,
which regionally hosts important gold, iron, manganese, chromite, diamond, bauxite, kaolinite, and cassiterite deposits. The
Amapari Au mine is characterized as of the orogenic gold deposit type. The highest gold grades are associated with highly
deformed rocks and are concentrated in sulfide-rich veins mainly composed of pyrrhotite. The data used for the generation
of gold prospectivity models include aerogeophysical and geological maps as well as the gold content of stream sediment samples.
The prospectivity maps provided by these three methods showed that the Amapari mine stands out as an area of high potential
for gold mineralization. The prospectivity maps also highlight new targets for gold exploration. These new targets were validated
by means of detailed maps of gold geochemical anomalies in soil and by fieldwork. The identified target areas exhibit good
spatial coincidence with the main soil geochemical anomalies and prospects, thus demonstrating that the delineation of exploration
targets by analysis and integration of indirect datasets in a geographic information system (GIS) is consistent with direct
prospecting. Considering that work of this nature has never been developed in the Amazonian region, this is an important example
of the applicability and functionality of geophysical data and prospectivity analysis in regions where geologic and metallogenetic
information is scarce. 相似文献
142.
This paper presents how environmental concerns emanating outside the Common Fisheries Policy (CFP) are increasingly setting the stage for EU fisheries management. This is illustrated via what is termed the exogenous entrance of environmental concerns through the implementation of directives in EU policy. More endogenous entrance of environmental concerns occurs via stakeholder participation in Regional Advisory Councils (RACs) as well as market mechanisms, such as ecolabelling and traceability. This study discusses how these latter channels of environmental concern may have become a more potent and efficient way of reaching environmental goals, outside of the primacy of the CFP. 相似文献
143.
Suspended sediment delivery from small catchments to the Bay of Biscay. What are the controlling factors? 下载免费PDF全文
The transport and yield of suspended sediment (SS) in catchments all over the world have long been topics of great interest. This paper addresses the scarcity of information on SS delivery and its environmental controls in small catchments, especially in the Atlantic region. Five steep catchments in Gipuzkoa (Basque Country) with areas between 56 and 796 km2 that drain into the Bay of Biscay were continuously monitored for precipitation, discharge and suspended sediment concentration (SSC) in their outlets from 2006 to 2013. Environmental characteristics such as elevation, slope, land‐use, soil depth and erodibility of the lithology were also calculated. The analysis included consideration of uncertainties in the SSC calibration models in the final suspended sediment yield (SSY) estimations. The total delivery of sediments from the catchments into the Bay of Biscay and its standard deviation was 272 200 ± 38 107 t yr.?1, or 151 ± 21 t km?2 yr.?1, and the SSYs ranged from 46 ± 0.48 to 217 ± 106 t km?2 yr.?1. Hydroclimatic variables and catchment areas do not explain the spatial variability found in SSY, whereas land‐use (especially non‐native plantations) and management (human impacts) appear to be the main factors that control this variability. Obtaining long‐term measurements on sediment delivery would allow for the effects of environmental and human induced changes on SS fluxes to be better detected. However, the data provided in this paper offer valuable and quantitative information that will enable decision‐makers to make more informed decisions on land management while considering the effects of the delivery of SS. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
144.
In this paper, we focus on strength properties of double porous materials having a Drucker-Prager solid phase at microscale. The porosity consists in two populations of micropores and mesopores saturated with different pressures. To this end, we consider a hollow sphere subjected to a uniform strain rate boundary conditions. For the microscale to mesoscale transition, we take advantage of available results by Maghous et al. (2009), while the meso to macro upscaling is performed by implementing a kinematical limit analysis approach using Eshelby-like trial velocity fields. This two-step homogenization procedure delivers analytical expression of the macroscopic criterion for the considered class of saturated double porous media. This generalizes and improves previous results established by Shen et al. (2014). The results are discussed in terms of the existence or not of effective stresses. Some illustrations are provided. 相似文献
145.
Alan W. McConnachie David R. Patton Sara L. Ellison Luc Simard 《Monthly notices of the Royal Astronomical Society》2009,395(1):255-268
We present the largest publicly available catalogue of compact groups (CGs) of galaxies identified using the original selection criteria of Hickson, selected from the Sixth Data Release of the Sloan Digital Sky Survey (SDSS DR6). We identify 2297 CGs down to a limiting magnitude of r = 18 (∼0.24 groups deg−2 ), and 74 791 CGs down to a limiting magnitude of r = 21 (∼6.7 groups deg−2 ). This represents 0.9 per cent of all galaxies in the SDSS DR6 at these magnitude levels. Contamination due to gross photometric errors has been removed from the bright sample of groups, and we estimate it is present in the large sample at the 14 per cent level. Spectroscopic information is available for 4131 galaxies in the bright catalogue (43 per cent completeness), and we find that the median redshift of these groups is z med = 0.09 . The median line-of-sight (LOS) velocity dispersion within the CGs from the bright catalogue is σLOS ≃ 230 km s−1 , and their typical intergalactic separations are of the order of 50–100 kpc. We show that the fraction of groups with interloping galaxies identified as members is in good agreement with the predictions from our previous study of a mock galaxy catalogue, and we demonstrate how to select CGs such that the interloper fraction is well defined and minimized. This observational data set is ideal for large statistical studies of CGs, the role of environment on galaxy evolution and the effect of galaxy interactions in determining galaxy morphology. 相似文献
146.
147.
Fluvial flood risk in Europe in present and future climates 总被引:2,自引:0,他引:2
Luc Feyen Rutger Dankers Katalin Bódis Peter Salamon José I. Barredo 《Climatic change》2012,112(1):47-62
In this work we evaluate the implications of climate change for future fluvial flood risk in Europe, considering climate developments
under the SRES A2 (high emission) and B2 (low emission) scenario. We define flood risk as the product of flood probability
(or hazard), exposure of capital and population, and vulnerability to the effect of flooding. From the European flood hazard
simulations of Dankers and Feyen (J Geophys Res 114:D16108. doi:, 2009) discharges with return periods of 2, 5, 10, 20, 50, 100, 250 and 500 years were extracted and converted into flood inundation
extents and depths using a planar approximation approach. Flood inundation extents and depths were transformed into direct
monetary damage using country specific flood depth-damage functions and land use information. Population exposure was assessed
by overlaying the flood inundation information with data on population density. By linearly interpolating damages and population
exposed between the different return periods, we constructed damage and population exposure probability functions under present
and future climate. From the latter expected annual damages (EAD) and expected annual population exposed (EAP) were calculated.
To account for flood protection the damage and population exposure probability functions were truncated at design return periods
based on the country GDP/capita. Results indicate that flood damages are projected to rise across much of Western Europe.
Decreases in flood damage are consistently projected for north-eastern parts of Europe. For EU27 as a whole, current EAD of
approximately €6.4 billion is projected to amount to €14–21.5 billion (in constant prices of 2006) by the end of this century,
depending on the scenario. The number of people affected by flooding is projected to rise by approximately 250,000 to 400,000.
Notwithstanding these numbers are subject to uncertainty, they provide an indication of potential future developments in flood
risk in a changing climate. 相似文献
148.
The water availability relies primarily on precipitation whose spatial and temporal variability depends on meteorological and topographic attributes. Water becomes a precious natural resource, especially in semiarid areas. Generally, decisions on water resources are made on the whole watershed, but the variability of precipitation is related to topography. The work was aimed at quantifying the spatial variability of annual precipitation for a 40-year-long time series in the Macta basin (Algeria) by using a geostatistical approach and to detect the temporal stability of dry areas. To assess if annual precipitation variability could depend upon the elevation, the study area was divided into five geographical units (polygons) based on elevation and polygon kriging was applied. For each hydrologic year, the standardized relative difference of precipitation (SRDP) was evaluated and dry areas identified. The temporal stability of SRDP with elevation was assessed using the Spearman rank coefficient. Geostatistical approach showed different variability structures of annual precipitation over the considered period. Results highlighted differences in SRDP within the geographical units located at different elevation and the non-stability of dry periods with time within the same polygon. A remarkable dry tendency was assessed in the northern polygon, while the polygons at higher elevations were dominated by temporal instability. The spatio-temporal non-stability of dry areas might be attributed to the change in general atmospheric circulation in North Africa over the last decades and to the nonlinear interaction among precipitation and orography. The identification of dry areas can help decision-makers to plan management and conservation programs in Algeria. 相似文献
149.
150.