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1.
着重讨论了网络用户经济效益的内涵以及用户的投入量和产出量,并提出了评价网络用户经济效益的指标体系,包括成本降低率,成本利润增长率、产品开发时间约率、市场占有增长率等系列指标。  相似文献   
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成都及附近地区旅游气候资源研究   总被引:9,自引:0,他引:9  
通过对成都及附近等7个地区多年气候资源及人体舒适指数进行分级比较,得出了7个地区的人体舒适指数的时间分布特征及对当地旅游的影响。  相似文献   
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In this study, heavy metal contents of samples from Gumusler creek in Turkey were studied and the metal contamination characteristics were investigated. In this respect, considering the pollutant sites in the area, systematic sediment samples were collected in a zone starting from the manifestation part of the water to the entrance of the Karasu creek in Gumusler town. Samples were taken from lower section of the river bed at 30 stations along Gumusler creek, 13 km in length and their heavy metal contents were analyzed with XRF Spectrometer. Correlation coefficients, element coefitic coefficient correlation, dendogram hierarchical cluster, model summary and Annova analysis statistical methods were applied to data. Strong positive correlations were determined for some elements which are believed to have possibly the same origin. In addition, mineralizations in the area are thought to cause variation in metal contents. Results of chemical analysis show that soil limit values and clark values were exceeded. The heavy metal accumulation in the creek is believed to be derived from non-operated Sb-Hg-W and Fe quarries.  相似文献   
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Due to their balneotherapeutic features, the organic-rich sediments in Makirina Cove are an important source of healing mud. An environmental geochemistry approach using normalization techniques was applied to evaluate the anthropogenic contribution of trace metals to sediments used as healing mud. Sediment geochemistry was found to be associated with land-use change and storm events, as well as with proximity of a road with heavy traffic in the summer months. Local valley topography preferentially channels lithogenic and pollutant transport to the cove. Concentrations and distribution of trace metals indicate lithogenic (Ni, Cr, Co) and anthropogenic (Pb, Cu, Zn and Se) contributions to the sediments. The calculation of enrichment factors indicates a moderate (EFs between 2–3.5) input of anthropogenic Cu and Pb in surficial sediments to a depth of 10 cm. Patients using the Makirina Cove sediments as healing mud could be to some extent exposed to enhanced uptake of metals from anthropogenic sources via dermal contact.  相似文献   
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Despite threats emanating from the influence of climate and non-climate forcing on the barrier island coastal region of southwestern Nigeria, the extent of the coastal erosion is poorly understood. We report evidence of coastal erosion and sediment accumulation in the region over a 34-year period (1973–2017), using Landsat imagery at intervals of approximately six years. Landsat image corrections and various water-extraction algorithms were used to systematically delineate coastal erosion and accumulation in the area. The region was subdivided into western and eastern subregions separated by Lagos Harbour. In the west, erosion took place during the periods 1973–1979, 1979–1984, 1990–1999 and 2005–2011, whereas in the east, erosion occurred during 1973–1979, 1990–1999 and 1999–2005. Coastal sediment accumulation occurred in the east during 1979–1984, 1984–1990, 2005–2011 and 2011–2017, whereas gains in the west occurred during 1984–1990, 1999–2005 and 2011–2017. The study revealed substantial net erosion of 1 228.1 ha in the region as a whole, over the full period. Sediment accumulation accompanying the coastal erosion appears to be linked to longshore drift. Erosion between 1973 and 2011 was probably attributable to climate change (storms and tidal conditions), longshore drift, the inflow and outflow of water at Lagos Harbour, coastal morphology and, possibly, human impacts. However, the coastal changes between 2011 and 2017 were more obviously associated with human activities, such as development of the Eko Atlantic construction project. Coastal surveillance, together with the use of environmentally sensitive protective measures, could possibly help to reduce coastal erosion in the region. Careful coastal management practices, including artificial nourishing and the installation of resilient structures (e.g. seawalls), should be undertaken to protect human settlements that are already at risk from sea-level rise.  相似文献   
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近年来,由于工农业和沿海养殖业的发展,我国近海污染逐年加重,赤潮发生频次增加。因此,监测近海污染和赤潮发生预报方法研究势在必行。本文用NOAA/AVHRR数据,分析近海水域污染状况,并探索赤潮发生的预报方法。  相似文献   
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张国祥 《海洋与湖沼》1992,23(5):517-526
于1985—1988年对前额间银鱼生物学特性、资源变动状况及其原因进行了现场和社会调查。调查表明,前颌间银鱼资源变动的原因是南、西区和吴淞口三大污染源对其生态环境严重污染;同时还有多年持续过捕超过其再增殖能力。为此,提出治理污染,恢复前颌间银鱼的生活环境及保护繁殖亲体的对策和建议。  相似文献   
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