首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   710篇
  免费   35篇
  国内免费   55篇
安全科学   15篇
废物处理   4篇
环保管理   242篇
综合类   238篇
基础理论   147篇
污染及防治   45篇
评价与监测   40篇
社会与环境   56篇
灾害及防治   13篇
  2024年   3篇
  2023年   7篇
  2022年   15篇
  2021年   17篇
  2020年   14篇
  2019年   18篇
  2018年   19篇
  2017年   23篇
  2016年   28篇
  2015年   33篇
  2014年   29篇
  2013年   33篇
  2012年   28篇
  2011年   57篇
  2010年   36篇
  2009年   58篇
  2008年   52篇
  2007年   54篇
  2006年   44篇
  2005年   34篇
  2004年   26篇
  2003年   22篇
  2002年   23篇
  2001年   24篇
  2000年   12篇
  1999年   21篇
  1998年   3篇
  1997年   10篇
  1996年   3篇
  1995年   8篇
  1994年   5篇
  1993年   2篇
  1992年   6篇
  1991年   4篇
  1990年   7篇
  1988年   3篇
  1986年   4篇
  1984年   1篇
  1982年   1篇
  1981年   2篇
  1980年   6篇
  1979年   3篇
  1978年   2篇
排序方式: 共有800条查询结果,搜索用时 15 毫秒
431.
The aim of the study was to assess the impacts of quarrying activities on the environment and livelihood of people in the Border II sub-location. Primary data was collected through questionnaires, Key Informant Interviews, Focus Group Discussion, laboratory analysis and observations. Whereas, secondary data was obtained from Landsat satellite images, journals, articles, books and reports. The acquired data were analyzed using excel and Arc GIS; and presented into tables and figures. The Land use/cover change analysis from the satellite images of the area showed that quarry lands have increased by 5.2 Ha (0.26%). Quarrying activities in the area were perceived to have both positive and negative impacts on the livelihood of people and the environment. Some of the most serious environmental problems were; dust pollution (82%), noise (76%), land degradation (74%), vegetation loss (60%) and vibration (52%). Whereas, negative socioeconomic impacts were; building cracks (54%), injuries (36%), school dropouts (35%), roads damages (33%), child labor (31%) and crop effects (30%). Moreover, 45% of the area residents and 44% of the quarry workers have experienced health problems related to quarrying activities. Nevertheless, there was a significant relationship between quarrying activities and the environmental as well as human health problems in the area (p<0.05). The positive impacts identified are; employment, roads improvement, security, CSR, building materials, business opportunities, among others. To mitigate the negative impacts, the quarry operators should develop and implement an Environmental and Social management Plan, including fair compensation of the project which affect a person, relocation of near homes, environmental pollution control, public participation, scaling down blasting activities, and strict policies compliance and enforcement.  相似文献   
432.
基于TM影像的桂林市植被覆盖时空动态监测与分析   总被引:1,自引:0,他引:1  
以西部地区中等规模城市——桂林市为例,利用1991、2006年两期TM卫星影像数据,在对原始数据预处理的基础上,提取归一化植被指数(NDVI)。依据混合像元二分模型,生成桂林市所辖5城区的两期植被覆盖度监测分类图像,对区域植被覆盖状况进行时空动态变化分析。结果表明,1991年~2006年间,城市植被覆盖区面积总体呈现下降趋势;在划分的3类植被覆盖类型中,低植被覆盖区面积减少幅度最为明显,中、高植被覆盖区面积有不同程度增长;低植被覆盖区主要分布在城市建成区与一些村镇外围区域,中、高植被覆盖区集中分布在城市远郊地带。此外,随着城市化的迅速发展,城乡各类建设用地面积不断增加,城市边缘地带的绿色植被正逐步被人工景观所取代。  相似文献   
433.
土地利用/覆被变化对陆地碳循环影响显著.文章基于实地采集的土壤、植物样品的测试数据和1989、2004两年8月陆地卫星TM遥感影像数据,采用生态系统类型法分析吉林省通榆县1989-2004年耕地、林地、草地、盐碱地、沙地等11 种地类之间土地利用变化对土地生态系统有机碳库的影响.计算结果表明1989-2004年通榆县土地生态系统有机碳库共损失了3.18 TgC(1Tg=106t),年均损失约为0.265 Tgc.其中,湿地、草地有机碳库分别损失5.54 TgC和3.71 TgC,盐碱地面积的增加导致有机碳库损失4.75 TgC.林地面积增加和沙地面积减少分别使有机碳库增加了4.58 TgC和3.75 TgC.研究区总体上为一个碳失汇,草地退化、湿地萎缩、土地沙化和盐碱化造成了有机碳库的碳损失,而植树造林、草地植被的恢复和重建等活动则可以显著增加土壤有机碳储量.该研究对于评估自然环境与人为活动影响下,特别是大规模土地整治与生态修复对土壤有机碳的增汇潜力和固碳效应的影响具有重要的理论意义和应用价值.  相似文献   
434.
Natural gas development using hydraulic fracturing has many potential environmental impacts, but among the most certain is the land disturbance required to build the well pads and other infrastructure required to drill and extract the gas. We used the Soil and Water Assessment Tool (SWAT) model to investigate how natural gas development could impact streamflow and sediment, total nitrogen (TN), and total phosphorous (TP) loadings in the upper Delaware River Basin (DRB), a relatively undeveloped watershed of 7,950 km2 that lies above the Marcellus Shale formation. If gas development was permitted, our projections show the DRB could experience development of over 600 well pads to extract natural gas at build out, which, with supporting infrastructure (roads, gathering pipelines), could convert over 5,000 ha from existing land uses in the study area. In subbasins with development activity we found sediment, TN, and TP yields could increase by an average of 15, 0.08, and 0.03 kg/ha/yr, respectively (an increase of 2, 3, and 15%, respectively) for each one percent of subbasin land area converted into natural gas infrastructure. At the study area outlet on the Delaware River at Port Jervis, New York, we found increases in the annual average streamflow and sediment, nitrogen, and phosphorus loads of up to 0.01, 0.2, 0.2, and 1%, respectively, for a rapid development year, and 0.08, 1.3, 2.0, and 11%, respectively, for the full development scenario. Editor's note : This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series.  相似文献   
435.
Unprecedented rates of human-induced changes in land use and land cover (LULC) at local and regional scales lead to alterations of global biogeochemical cycles. Driving forces behind LULC changes mainly include rapid growth rates of population and consumption, lack of valuation of ecological services, poverty, ignorance of biophysical limitations, and use of ecologically incompatible technologies. One of the major ecological tragedies of the commons in a Mediterranean region of Turkey is the loss of Lake Amik at the expense of increasing the area of croplands, which used to provide vital ecosystem goods and services for the region. In this study, we aimed at quantifying the effects of past land-use transitions on soil organic carbon (SOC) pools (0–20 cm) in a Mediterranean region of 3930 km2, between 1972 and 2000. LULC changes were quantified from a time series of satellite images of Landsat-MSS in 1972, Landsat-5 TM in 1987, and Landsat-7 ETM+ in 2000 using geographic information systems. The study showed that the increase in croplands between 1972 and 1987 took place at the expense of the irreversible losses of Lake Amik and its related wetlands of over 53 km2. In the period of 1972 to 2000, croplands, settlements, and evergreen forests increased by 174%, 106%, and 14%, respectively. The increase in settlements occurred mostly to the detriment of croplands. Given the average rates of all the land-use transitions, and associated changes in SOC density for the study region of 3930 km2, total SOC pool was estimated to decrease by 14.1% from 130.1 Mt in 1972 to 111.7 Mt in 2000.  相似文献   
436.
Investigations of land use/land cover (LULC) change and forest management are limited by a lack of understanding of how socioeconomic factors affect land use. This lack also constrains the predictions of future deforestation, which is especially important in the Amazon basin, where large tracts of natural forest are being converted to managed uses. Research presented in this article was conducted to address this lack of understanding. Its objectives are (a) to quantify deforestation in the Northern Ecuadorian Amazon (NEA) during the periods 1986–1996 and 1996–2002; and (b) to determine the significance and magnitude of the effects of socioeconomic factors on deforestation rates at both the parroquia (parish) and finca (farm) levels. Annual deforestation rates were quantified via satellite image processing and geographic information systems. Linear spatial lag regression analyses were then used to explore relationships between socioeconomic factors and deforestation. Socioeconomic factors were obtained, at the finca level, from a detailed household survey carried out in 1990 and 1999, and at the parroquia level from data in the 1990 and 2001 Ecuadorian censuses of population. We found that the average annual deforestation rate was 2.5% and 1.8%/year for 1986–1996 and 1996–2002, respectively. At the parroquia level, variables representing demographic factors (i.e., population density) and accessibility factors (i.e., road density), among others, were found to be significantly related to deforestation. At the farm level, the factors related to deforestation were household size, distance by road to main cities, education, and hired labor. The findings of this research demonstrate both the severity of deforestation in the Northern Ecuadorian Amazon and the array of factors affecting deforestation in the tropics.  相似文献   
437.
对南山国家森林公园主要植被物种资源进行调查和区系结构研究。结果表明,南山国家森林公园森林覆盖率达73%,自然生态系统中目前已知的高等植物(藻菌、苔藓、地衣除外)共计有74科、251属、340种。构成镇江市区各类植被的优势成分共有约27种,其中东亚分布的种占55.6%,热带分布为主的植物占7.4%,连同东亚分布以及我国特有热带、亚热带分布为主的成分,一起可达88.9%。南山国家森林公园植被在区系组成上具有明显的亚热带特点,同时也反映出一定的过渡性,与江苏省森林木本植物区系分布特点基本一致。  相似文献   
438.
基于RS和GIS技术的贵州省植被生态环境监测分析   总被引:1,自引:0,他引:1  
为阐明贵州省植被生态环境变化的整体状况,基于RS和GIS技术,应用美国国家航空航天局最新的全球植被指数变化研究数据(GIMMS),通过计算月归一化植被指数(NDVI)变化率,并对研究区一元线性回归模拟,分析了贵州省1982年-2003年的地表植被覆盖。结果表明:22年来,研究区植被覆盖呈增加趋势,表明贵州省植被生态环境向好的方向发展;贵州省平均植被覆盖在春季和秋季呈上升趋势,夏季和冬季呈下降趋势,其中春季对植被覆盖总变化量的贡献最大;植被覆盖程度增减因区域不同而异,变化程度呈增加的区域主要位于贵,ki-I省的中部地区;变化程度呈减小的区域分布在贵州省的四周边缘。  相似文献   
439.
In this study, Grey model (GM) and artificial neural network (ANN) were employed to predict suspended solids (SSeff) and chemical oxygen demand (CODeff) in the effluent from a wastewater treatment plant in industrial park of Taiwan. When constructing model or predicting, the influent quality or online monitoring parameters were adopted as the input variables. ANN was also adopted for comparison. The results indicated that the minimum MAPEs of 16.13 and 9.85% for SSeff and CODeff could be achieved using GMs when online monitoring parameters were taken as the input variables. Although a good fitness could be achieved using ANN, they required a large quantity of data. Contrarily, GM only required a small amount of data (at least four data) and the prediction results were even better than those of ANN. Therefore, GM could be applied successfully in predicting effluent when the information was not sufficient. The results also indicated that these simple online monitoring parameters could be applied on prediction of effluent quality well.  相似文献   
440.
以国家生态文明试验区(贵州)作为研究区,以植被覆盖度(FVC)作为研究对象,基于2000~2019年的NDVI数据分析了贵州省近20年FVC的时空演变特征,利用地理探测器方法识别并量化了经济持续增速下维持植被恢复的主要驱动力,结果表明:(1)近20年来贵州省FVC整体呈增加趋势,FVC分布整体水平较高,主要以中等、中高和高度覆盖为主,三者面积占比之和约为89.7%,年均增长率为0.52%,平均FVC为0.53.(2)近20年来贵州省FVC变化趋势以轻微改善、基本不变为主,两者面积占比之和为68.94%,改善区域面积占比为57.93%,西部区域得到明显改善和提升,退化区域主要集中在城镇周边,总体动态变化趋于稳定且向好改善.(3)FVC空间分布格局演变深受人类活动与自然环境因子的双重影响,且人类活动对于植被恢复的驱动作用更强,国内生产总值(GDP)和降水是经济持续增速下维持植被恢复的人类活动与自然环境因子主导驱动力.(4)积极推动产业结构优化升级、大力推进第三产业快速发展以及不断贯彻落实退耕还林还草政策等积极的人类活动为贵州省实现经济增速与植被恢复协调发展的“双赢”局面做出了巨大贡献.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号