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21.
Historical trends in Florida temperature and precipitation 总被引:1,自引:0,他引:1
Michelle M. Irizarry‐Ortiz Jayantha Obeysekera Joseph Park Paul Trimble Jenifer Barnes Winifred Park‐Said Erik Gadzinski 《水文研究》2013,27(16):2225-2246
Because of its low topographic relief, unique hydrology, and the large interannual variability of precipitation, Florida is especially vulnerable to climate change. In this paper, we investigate a comprehensive collection of climate metrics to study historical trends in both averages and extremes of precipitation and temperature in the state. The data investigated consist of long‐term records (1892–2008) of precipitation and raw (unadjusted) temperature at 32 stations distributed throughout the state. To evaluate trends in climate metrics, we use an iterative pre‐whitening method, which aims to separate positive autocorrelation from trend present in time series. Results show a general decrease in wet season precipitation, most evident for the month of May and possibly tied to a delayed onset of the wet season. In contrast, there seems to be an increase in the number of wet days during the dry season, especially during November through January. We found that the number of dog days (above 26.7 °C) during the year and during the wet season has increased at many locations. For the post‐1950 period, a widespread decrease in the daily temperature range (DTR) is observed mainly because of increased daily minimum temperature (Tmin). Although we did not attempt to formally attribute these trends to natural versus anthropogenic causes, we find that the urban heat island effect is at least partially responsible for the increase in Tmin and its corresponding decrease in DTR at urbanized stations compared with nearby rural stations. In the future, a formal trend attribution study should be conducted for the region. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
22.
Monitoring of wastewater percolation in unsaturated sandy soil using geoelectrical measurements at Gabal el Asfar farm,northeast Cairo,Egypt 总被引:5,自引:5,他引:0
Khaled M. Said Gemail 《Environmental Earth Sciences》2012,66(3):749-761
The use of wastewater for irrigation in sandy soil increases the pollution risk of the soil and may infiltrate to the shallow
groundwater aquifer. In such environment, some important parameters need to be obtained for monitoring the wastewater in the
unsaturated zone over the aquifer. These parameters include clay content, heterogeneities of the upper soils, depth to the
aquifer and the variations of groundwater quality. In the present work, the efficiency of DC resistivity method in forms of
1-D and 2-D measurements was studied for wastewater monitoring in the Gabal el Asfar farm, northeast of Cairo, Egypt. Forty-one
Schlumberger soundings (VES) were performed then followed by three pole-dipole 2-D profiles along some considered regions
within the area. The resistivity measurements were integrated with the boreholes, hydrogeological and hydrochemical (surface
and groundwater samples) information to draw a clear picture for the subsurface conditions. The obtained results were presented
as cross sections and 3-D visualization to trace the clay intercalations within the unsaturated zone. In addition, a vulnerability
map was created using the obtained results from 1-D Schlumberger survey and confirmed with the 2-D resistivity profiling.
The obtained results have shown that the 2-D resistivity imaging technique is a powerful tool for mapping the small-scale
variability within the unsaturated zone and the wastewater infiltration. However, limitations of resistivity techniques were
observed in the area with limited resistivity contrast such as thin clay layers with brackish water background. Under that
condition, the measured pattern of resistivity distributions depends on the applied electrode array, electrode spacing and
using the available geological information during the inversion process. 相似文献
23.
Effect of the combination of lime and natural pozzolana on the compaction and strength of soft clayey soils: a preliminary study 总被引:1,自引:0,他引:1
Soft soil stabilization has been practised for quite some time by mixing additives, such as cement, lime and fly ash to the soil to increase its strength. However, there is a lack of investigations on the use of natural pozzolana alone or combined with lime for ground improvement applications. An experimental programme was undertaken to study the effect of using lime, natural pozzolana or a combination of both on the geotechnical characteristics of soft soils. Lime or natural pozzolana was added to soft soils at ranges of 0?C10% and 0?C20%, respectively. In addition, combinations of lime?Cnatural pozzolana were added to soft soils at the same ranges. Test specimens were subjected to compaction tests, shear tests and unconfined compression tests. Specimens were cured for 1, 7, 28 and 90?days, after which they were tested for unconfined compression tests. Based on the favourable results obtained, it can be concluded that the soft soils can be successfully stabilized by the combined action of lime and natural pozzolana. Since natural pozzolana is much cheaper than lime, the addition of natural pozzolana in lime?Csoil mix may particularly become attractive and can result in cost reduction of construction. 相似文献
24.
Spatiotemporal drought variability in northwestern Africa over the last nine centuries 总被引:3,自引:1,他引:2
Ramzi Touchan Kevin J. Anchukaitis David M. Meko Mohamed Sabir Said Attalah Ali Aloui 《Climate Dynamics》2011,37(1-2):237-252
Changes in precipitation patterns and the frequency and duration of drought are likely to be the feature of anthropogenic climate change that will have the most direct and most immediate consequences for human populations. The latest generation of state-of-the-art climate models project future widespread drying in the subtropics. Here, we reconstruct spatially-complete gridded Palmer drought severity index values back to A.D. 1179 over Morocco, Algeria, and Tunisia. The reconstructions provide long-term context for northwest African hydroclimatology, revealing large-scale regional droughts prior to the sixteenth century, as well as more heterogeneous patterns in sixteenth, eighteenth, and twentieth century. Over the most recent decades a shift toward dry conditions over the region is observed, which is consistent with general circulation model projections of greenhouse gas forced enhanced regional subtropical drought. 相似文献
25.
New historical data from primary sources, allow us to revisit the Djidjelli earthquakes of 21 and 22 August 1856 (I0 VIII, IX respectively). These two large seismic events are among the most significant events that have affected the North
African coast. They have caused extensive damage and generated a tsunami that propagated at several harbours of the western
Mediterranean Sea. The effects of each earthquake are analysed from all documentary source materials, emphasising the confrontation
of observations and data for an accurate reconstruction of the macroseismic field of both events. The method used provides
a more precise way to determine the characteristics of the Djidjelli earthquakes. 相似文献
26.
Analysis of Mississippian coral assemblages from the Khenifra region of Central Morocco together with data from foraminiferal/algal microfossils has established new age dating of 5 localities within the Azrou–Khenifra Basin: Souk El Had and Sidi Lamine, where corals occur mainly in biostromes protected by oolitic shoals, Tabainout, where corals have been recorded in different environments related to microbial mounds, Alhajra Almatkouba, where corals occur in biostromal reworked beds and Tiouinine, where corals occur in a well structured, fringing reef. This study demonstrates the presence of richer more diverse coral assemblages than previously recorded, in a variety of environmental settings. These coral assemblages strengthen correlations with the Adarouch area in the NE part of the Azrou–Khenifra Basin. It is emphasised that in the upper Viséan there are close similarities with rugose coral assemblages in other parts of the Western Palaeotethys including North Africa, SW Spain and NW Europe, and that all belong to the same biogeographic province. 相似文献
27.
Elsayed Said Mohamed 《Arabian Journal of Geosciences》2013,6(12):4647-4659
This study aims to use spatial analyses and a geographic information system (GIS) to assess the environmental sensitivity for desertification in the north Sinai Peninsula, Egypt. Based on the Mediterranean Desertification and Land Use (MEDALUS) approach and the characteristics of the study area, a regional model was developed using GIS. Five main indicators of desertification including soil, climate, erosion, plant cover, and management were considered for estimating the environmental sensitivity to desertification. A spatial analyst extension Arc-GIS 10 software was used for matching the thematic layers and assessing the desertification index, of which the map of environmentally sensitive areas of the north Sinai Peninsula is produced. The obtained data reveals that 65 % of north Sinai is characterized by very severe sensitivity to desertification while the low sensitive one exhibits only 1.2 %. The moderately sensitive area occupies approximately 23 % of the study area. ETM+ and SPOT images are recommended to monitor sensitivity. The MEDALUS model was developed under the Egyptians to assess desertification sensitivity. 相似文献
28.
Assia Benchouk Mounir Derfouf Nabil Abou-Bekr Said Taibi 《Arabian Journal of Geosciences》2013,6(12):4565-4573
This paper presents an experimental study carried out on some clayey soils of Tlemcen region situated in the North West of Algeria. The characterization of the volumetric behavior under the effect of suction is studied on drying–wetting paths which highlight the correspondence between void ratio, degree of saturation, and water content versus suction. The initial conditions of studied material are in slurry form and compacted at different initial water contents. For the slurry form, correlations are derived to predict parameters characterizing the drying path. 相似文献
29.
Natural Hazards - The Murree region in Pakistan is frequently affected by landslides and causes damages to lands, houses, life lines and even loss of livestock and human life. We have attempted in... 相似文献