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61.
AbstractMulti-stakeholder sustainability certification schemes have become a favorite instrument for applying good governance, though studies indicate their inefficiency at the producer level. In this study, we used a mixed-method approach to first, map the institutional context of independent oil-palm smallholders in rural Sumatra while, second, reflecting upon the impact of the Smallholder Standard proposed by the Roundtable on Sustainable Palm Oil on smallholder management practices. We hold that non-recognition of micro-scale perspectives within governance processes may partially explain noncompliance with certification principles among smallholders. The Smallholder Standard appears unable to mitigate challenges important for smallholders, who in turn cannot properly comply with it, due to problems including weather instability and high management costs. We suggest that certification schemes need to work on some overlooked but essential preconditions of good governance, namely gaining micro-level visibility and acceptance. 相似文献
62.
Using Multitemporal Remote Sensing Imagery and Inundation Measures to Improve Land Change Estimates in Coastal Wetlands 总被引:1,自引:0,他引:1
Remote sensing imagery can be an invaluable resource to quantify land change in coastal wetlands. Obtaining an accurate measure
of land change can, however, be complicated by differences in fluvial and tidal inundation experienced when the imagery is
captured. This study classified Landsat imagery from two wetland areas in coastal Louisiana from 1983 to 2010 into categories
of land and water. Tide height, river level, and date were used as independent variables in a multiple regression model to
predict land area in the Wax Lake Delta (WLD) and compare those estimates with an adjacent marsh area lacking direct fluvial
inputs. Coefficients of determination from regressions using both measures of water level along with date as predictor variables
of land extent in the WLD, were higher than those obtained using the current methodology which only uses date to predict land
change. Land change trend estimates were also improved when the data were divided by time period. Water level corrected land
gain in the WLD from 1983 to 2010 was 1 km2 year−1, while rates in the adjacent marsh remained roughly constant. This approach of isolating environmental variability due to
changing water levels improves estimates of actual land change in a dynamic system, so that other processes that may control
delta development such as hurricanes, floods, and sediment delivery, may be further investigated. 相似文献
63.
Fadi Chaaban Hanan Darwishe Barbara Louche Yvonne Battiau-Queney Eric Masson Jamal El Khattabi Erick Carlier 《Environmental Earth Sciences》2012,65(1):183-193
The use of geographic information system (GIS) minimizes the effort and improves the efficiency of numerical models. The GIS
provides a platform for high capacity collection, management, manipulation, analysis, modeling and display of spatial data.
The conceptual model is created using GIS objects including points, arcs and polygons so that it can accurately represent
real world condition. According to the research problem, the geographical model is based on Hypergraph Based Data Structure
method, and a conceptual data model has been created from which a physical data model was elaborated in ArcGIS9.3 platform.
The groundwater modeling system (GMS) provides a powerful tool for hydrodynamics modeling and it is able to solve complex
problems such as the groundwater flow and seawater intrusion. The sand-dune system of Hardelot-Plage (North of France) suffers
from a lack of well-developed foredune. This problem is linked to the almost constant saturation of beach sand which is the
potential source of dune nourishment. In the south of Hardelot, the coastline is slowly, but constantly retreating. To remedy
this situation, a coupling between a GIS and GMS was adopted, in order to find the possible scenarios which could lower the
piezometric surface in the concerned area and allow dune nourishment again. The GMS used supports the Modflow-2000 code. A
direct approach to designing Modflow finite difference model is tedious and less intuitive, specifically for complex boundary
and initial conditions. Therefore, a Modflow model can be developed either using a grid or conceptual model approach. The
preparation of input data modeling is tedious and takes a long time. The model created in GMS was calibrated against the historical
and observed water level data for 1995–2006. Then a hydrodispersive model (MT3d code in GMS) was launched for evaluating sea-water
intrusion. The model was run to generate groundwater and salt concentration scenario during pumping tests. 相似文献
64.
William J. Chaplin Andrew M. Dumbill Yvonne P. Elsworth George R. Isaak Clive P. McLeod Brek A. Miller Roger New Balázs Pintér 《Solar physics》2004,220(2):307-316
The Birmingham Solar-Oscillations Network (BiSON) has acquired high-precision solar mean magnetic field (SMMF) data on a 40-s
cadence for a decade. We present attempts to compare such data from recent years with the occurrence of coronal mass ejections
(CMEs) as recorded by LASCO, using correlation techniques applied to measurements from different BiSON instruments to maximise
the sensitivity to CME-related SMMF responses. SMMF measurements were recorded at the time of occurrence of several hundred
CMEs. No CME event shows a convincing response in our SMMF data at short periods setting a threshold amplitude of 12 mG. By
averaging data sets we are able to set lower thresholds, which depend somewhat on the distribution of response strengths.
A brief summary of the very first results of this study is also given in Chaplin et al. 相似文献
65.
66.
The interest in numerical simulation of cascading processes involving mass movements and lakes has recently risen strongly, especially as the formation of new lakes in high-mountain areas as a consequence of glacier recession can be observed all over the world. These lakes are often located close to potentially unstable slopes and therewith prone to impacts from mass movements, which may cause the lake to burst out and endanger settlements further downvalley. The need for hazard assessment of such cascading processes is continuously rising, which demands methodological development of coupled numerical simulations. Our study takes up on the need for systematic analysis of the effect of assumptions taken in the simulation of the process chain and the propagation of the corresponding uncertainties on the simulation results. We complemented the research of Adv Geosci 35:145-155, 2014 carried out at Lake 513 in the Cordillera Blanca, Peru, by focusing on the aspects of (a) ice-avalanche scenario development and of (b) analysis of uncertainty propagation in the coupled numerical simulation of the process chain of an impact wave triggered by a rock/ice avalanche. The analysis of variance of the dimension of the overtopping wave was based on 54 coupled simulation runs, applying RAMMS and IBER for simulation of the ice avalanche and the impact wave, respectively. The results indicate (a) location and magnitude of potential ice-avalanche events, and further showed (b) that the momentum transfer between an avalanche and the impact wave seems to be reliably representable in coupled numerical simulations. The assessed parameters—initial avalanche volume, friction calibration, mass entrainment and transformation of the data between the models—was decisive of whether the wave overtopped or not. The overtopping time and height directly characterize the overtopping wave, while the overtopping volume and the discharge describe the overtopping hydrograph as a consequence of the run-up rather than the wave. The largest uncertainties inherent in the simulation of the impact wave emerge from avalanche-scenario definition rather than from coupling of the models. These findings are of relevance also to subsequent outburst flow simulation and contribute to advance numerical simulation of the entire process chain, which might also be applied to mass movements other than rock/ice avalanches. 相似文献
67.
Oceanographic controls on shallow‐water temperate carbonate sedimentation: Spencer Gulf,South Australia 下载免费PDF全文
Laura G. O'Connell Noel P. James Mark Doubell John F. Middleton John Luick David R. Currie Yvonne Bone 《Sedimentology》2016,63(1):105-135
Spencer Gulf is a large (ca 22 000 km2), shallow (<60 m water depth) embayment with active heterozoan carbonate sedimentation. Gulf waters are metahaline (salinities 39 to 47‰) and warm‐temperate (ca 12 to ?28°C) with inverse estuarine circulation. The integrated approach of facies analysis paired with high‐resolution, monthly oceanographic data sets is used to pinpoint controls on sedimentation patterns with more confidence than heretofore possible for temperate systems. Biofragments – mainly bivalves, benthic foraminifera, bryozoans, coralline algae and echinoids – accumulate in five benthic environments: luxuriant seagrass meadows, patchy seagrass sand flats, rhodolith pavements, open gravel/sand plains and muddy seafloors. The biotic diversity of Spencer Gulf is remarkably high, considering the elevated seawater salinities. Echinoids and coralline algae (traditionally considered stenohaline organisms) are ubiquitous. Euphotic zone depth is interpreted as the primary control on environmental distribution, whereas seawater salinity, temperature, hydrodynamics and nutrient availability are viewed as secondary controls. Luxuriant seagrass meadows with carbonate muddy sands dominate brightly lit seafloors where waters have relatively low nutrient concentrations (ca 0 to 1 mg Chl‐a m?3). Low‐diversity bivalve‐dominated deposits occur in meadows with highest seawater salinities and temperatures (43 to 47‰, up to 28°C). Patchy seagrass sand flats cover less‐illuminated seafloors. Open gravel/sand plains contain coarse bivalve–bryozoan sediments, interpreted as subphotic deposits, in waters with near normal marine salinities and moderate trophic resources (0·5 to 1·6 mg Chl‐a m?3) to support diverse suspension feeders. Rhodolith pavements (coralline algal gravels) form where seagrass growth is arrested, either because of decreased water clarity due to elevated nutrients and associated phytoplankton growth (0·6 to 2 mg Chl‐a m?3), or bottom waters that are too energetic for seagrasses (currents up to 2 m sec?1). Muddy seafloors occur in low‐energy areas below the euphotic zone. The relationships between oceanographic influences and depositional patterns outlined in Spencer Gulf are valuable for environmental interpretations of other recent and ancient (particularly Neogene) high‐salinity and temperate carbonate systems worldwide. 相似文献
68.
Acid mine drainage (AMD) is treated at several points in the Lausitz lignite mine district (Saxony, Germany) in treatment
plants. The remaining alkaline low density sludge (LDS) was deposited in acidic mining lakes without having an impact on the
lake water quality. Batch experiments show that alkalinity can be raised using LDS from acid mine drainage treatment plants
together with CO2. Batch experiments were conducted using lake water and deposited LDS from the mining lake Spreetal-Nordost with varying concentrations
of CO2. Also the duration of gas contact as well as the LDS–water ratio was changed in the batch experiments. The gas contact time
and the partial pressure of CO2 are the relevant parameters controlling the alkalinity in the lake water at the end of the experiments. The Ca and Mg concentrations
of the pore water are relevant for higher pH values. Therefore, dissolved CO2 can form bicarbonate or carbonate complexes, thus alkalinity rises. A second factor for alkalinity gain is the calcite content
of the sludge, because CO2 triggers the dissolution of carbonates. Therefore, unused calcite in the sludge can raise the alkalinity more effectively
by the application of carbon dioxide. Furthermore, it was shown that remobilization of trace elements will not affect the
water quality. 相似文献
69.
Nico Mölg Christian Huggel Thilo Herold Florian Storck Simon Allen Wilfried Haeberli Yvonne Schaub Daniel Odermatt 《地球表面变化过程与地形》2021,46(13):2551-2564
Retreating glaciers give way to new landscapes with lakes as an important element. In this study, we combined available data on lake outlines with historical orthoimagery and glacier outlines for six time periods since the end of the Little Ice Age (LIA; ~1850). We generated a glacial lake inventory for modern times (2016) and traced the evolution of glacial lakes that formed in the deglaciated area since the LIA. In this deglaciated area, a total of 1192 lakes formed over the period of almost 170 years, 987 of them still in existence in 2016. Their total water surface in 2016 was 6.22 ± 0.25 km2. The largest lakes are > 0.4 km2 (40 ha) in size, while the majority (> 90%) are smaller than 0.01 km2. Annual increase rates in area and number peaked in 1946–1973, decreased towards the end of the 20th century, and reached a new high in the latest period 2006–2016. For a period of 43 years (1973–2016), we compared modelled overdeepenings from previous studies to actual lake genesis. For a better prioritization of formation probability, we included glacier-morphological criteria such as glacier width and visible crevassing. About 40% of the modelled overdeepened area actually got covered by lakes. The inclusion of morphological aspects clearly aided in defining a lake formation probability to be linked to each modelled overdeepening. Additional morphological variables, namely dam material and type, surface runoff, and freeboard, were compiled for a subset of larger and ice-contact lakes in 2016, constituting a basis for future hazard assessment. 相似文献
70.