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121.
Emmanuel A. Frimpong John G. Lee Trent M. Sutton 《Journal of the American Water Resources Association》2006,42(5):1349-1361
ABSTRACT: This paper presents the results of cost effectiveness (CE) analysis of vegetative filter strips (VFS) and instream half‐logs as tools for recovering scores on a fish Index of Biotic Integrity (IBI) in the upper Wabash River watershed (UW) in Indiana. Three assumptions were made about recovery time for IBI scores (5,15, and 30 years) and social discount rates (1, 3, and 5 percent), which were tested for sensitivity of the estimated CE ratios. Effectiveness of VFS was estimated using fish IBIs and riparian forest cover from 49 first‐order to fifth‐order stream reaches. Half‐log structures had been installed for approximately two years in the UW prior to the study and provided a basis for estimates of cost and maintenance. Cost effectiveness ratios for VFS decreased from $387 to $277 per 100 m for a 1 percent increase in IBI scores from first‐to fifth‐order streams with 3 percent discount and 30‐year recovery. This cost weighted by proportion of stream orders was $360. The ratio decreased with decreasing time of recovery and discount rate. Based on installation costs and an assumption of equal recovery rates, half‐logs were two‐thirds to one‐half as cost‐effective as VFS. Half‐logs would be a cost‐effective supplement to VFS in low order streams if they can be proven to recover IBI scores faster than VFS do. This study provides baseline data and a framework for planning and determining the cost of stream restoration. 相似文献
122.
Xi Liu Zhi Wang Lu Zhang Weiying Fan Chao Yang Enhua Li Yun Du Xuelei Wang 《环境科学学报(英文版)》2021,33(11):102-113
Antibiotics are widely used in humans and animals, but their transformation from surface water to groundwater and the impact of land uses on them remain unclear. In this study, 14 antibiotics were systematically surveyed in a complex agricultural area in Central China. Results indicated that the selected antibiotic concentrations in surface waters were higher in winter (average: 32.7 ng/L) than in summer (average: 17.9 ng/L), while the seasonal variation in groundwaters showed an opposite trend (2.2 ng/L in dry winter vs. 8.0 ng/L in summer). Macrolides were the predominant antibiotics in this area, with a detected frequency of over 90%. A significant correlation between surface water and groundwater antibiotics was only observed in winter (R2 = 0.58). This study further confirmed the impact of land uses on these contaminants, with optimal buffer radii of 2500 m in winter and 500 m in summer. Risk assessment indicated that clarithromycin posed high risks in this area. Overall, this study identified the spatiotemporal variability of antibiotics in a typical agricultural area in Central China and revealed the impact of land uses on antibiotic pollution in aquatic environments. 相似文献
123.
Cropland Riparian Buffers throughout Chesapeake Bay Watershed: Spatial Patterns and Effects on Nitrate Loads Delivered to Streams 总被引:1,自引:0,他引:1
Donald E. Weller Matthew E. Baker 《Journal of the American Water Resources Association》2014,50(3):696-712
We used statistical models to provide the first empirical estimates of riparian buffer effects on the cropland nitrate load to streams throughout the Chesapeake Bay watershed. For each of 1,964 subbasins, we quantified the 1990 prevalence of cropland and riparian buffers. Cropland was considered buffered if the topographic flow path connecting it to a stream traversed a streamside forest or wetland. We applied a model that predicts stream nitrate concentration based on physiographic province and the watershed proportions of unbuffered and buffered cropland. We used another model to predict annual streamflow based on precipitation and temperature, and then multiplied the predicted flows and concentrations to estimate 1990 annual nitrate loads. Across the entire Chesapeake watershed, croplands released 92.3 Gg of nitrate nitrogen, but 19.8 Gg of that was removed by riparian buffers. At most, 29.4 Gg more might have been removed if buffer gaps were restored so that all cropland was buffered. The other 43.1 Gg of cropland load cannot be addressed with riparian buffers. The Coastal Plain physiographic province provided 52% of the existing buffer reduction of Bay‐wide nitrate loads and 36% of potential additional removal from buffer restoration in cropland buffer gaps. Existing and restorable nitrate removal in buffers were lower in the other three major provinces because of less cropland, lower buffer prevalence, and lower average buffer nitrate removal efficiency. 相似文献
124.
Effects of riparian land use on water quality and fish communities in the headwater stream of the Taizi River in China 总被引:1,自引:0,他引:1
Sen DING Yuan ZHANG Bin LIU Weijing KONG Wei MENG 《Frontiers of Environmental Science & Engineering》2013,7(5):699-708
Riparian land use remains one of the most significant impacts on stream ecosystems. This study focuses on the relationship between stream ecosystems and riparian land use in headwater regions. Four riparian land types including forest, grassland, farmland, and residential land were examined to reveal the correlation between stream water and fish communities in headwater streams of the Taizi River in north-eastern China. Four land types along riparian of 3 km in length were evaluated at 25, 50, 100, 200 and 500 m widths, respectively. Generally, the results found a significant relationship between riparian land uses and stream water quality. Grassland was positively correlated with water quality parameters (conductivity and total dissolved solids) at scales from 100 to 500 m riparian width. Farmland and residential land was negatively correlated with water quality parameters at scales from 25 to 500 m and from 50 to 200 m riparian widths, respectively. Although the riparian forest is important for maintaining habitat diversity and fish communities, the results found that only fish communities were significantly correlated with the proportion of riparian farmland. Farmland had a positive correlation with individual fish abundance within a riparian corridor of 25 to 50 m, but a negative correlation with fish diversity metrics from 25 to 100 m. This study indicates that effective riparian management can improve water quality and fish communities in headwater streams. 相似文献
125.
126.
基于GIS的耕地定级方法及其应用 总被引:5,自引:1,他引:4
根据模糊数学和多元统计分析原理,建立了一个定量的耕地定级方法,并以湖北省鄂州市进行了实例说明,从而为该地区耕地的合理利用与管理提供依据,有利于实现耕地资源的信息共享和城乡土地市场一体化的建立。首先采用灰色关联分析法筛选定级因子,层次分析法确定相应的权系数;矢量化相关图层并提取农贸中心和道路作缓冲区分析后,采用多边形法确定耕地评价单元;通过采用不同的分值函数对因子属性值进行标准化;最后采用综合指数模型计算定级指数并根据聚类分析法将鄂州市耕地划分为5级,利用ArcGIS实现定级结果图的输出。定级结果表明:鄂州市耕地质量中等偏上,以二、三级地为主,共占74.78 %,该评价结果基本符合实际,同时利用GIS引入缓冲区分析方法来获取部分评价因子数据,提高了评价结果的准确性。 相似文献
127.
通过检验案例发现的隐患,阐述了安全部件在电梯运行中的重要性。对安全部件安装过程中存在的问题,分析了失效原因以及存在的问题,提出了解决方法。 相似文献
128.
Impact of Vegetative Cover on Runoff and Soil Erosion at Hillslope Scale in Lanjaron, Spain 总被引:3,自引:0,他引:3
Soil loss and surface runoff patterns over a four-year period (1997–2000) were studied in erosion plots from three hillslopes under different vegetative covers (Rosmarinus officinalis, Triticum aestivum and natural-spontaneous vegetation) in Lanjaron (Alpujarras) on the south flank of the Sierra Nevada of southeast Spain. The erosion plots were located on the hillslopes at 35.5% incline, at 1,480 m in altitude and with 41.8 m2 (21 m×1.9 m) in area. The vegetative covers were tested for effectiveness in controlling the surface runoff and soil loss production. The highest runoff and erosion values, ranging from 114.1 to 1.7 mmyr–1 and from 14,564.3 to 6.6 kgha–1yr–1, respectively, over the entire study period, were measured under the Triticum aestivum. In the Rosmarinus officinalis, runoff ranged from 7.9 to 1.3 mmyr–1 and erosion from 156.4 to 2.3 kgha–1yr–1, while on the hillslope under natural-spontaneous vegetation, runoff ranged from 4.4 to 0.9 mmyr–1 and erosion from 322.3 to 2.2 kgha–1yr–1. According to the results the vegetative covers of Rosmarinus officinalis and natural-spontaneous vegetation reduced the soil losses by 99 and 98%, with respect to the Triticum aestivum, and the runoff losses by 94 and 96%, respectively. Also, the Rosmarinus officinalis and natural-spontaneous plants influenced infiltration by intercepting much of the rainfall water respect to the Triticum aestivum. Monitoring allowed more direct linkages to be made between management practices and their impacts on runoff and soil erosion, thereby enabling to identify problems and take appropriate preventive measures to improve the management practices. 相似文献
129.
Asulam is often applied from the air to control bracken. This herbicide affects other ferns and spray drift could affect their survival. This paper discusses the use of bioassays to assess drift (a) spatially around a single bracken patch, (b) downwind from sprayed areas, and (c) spatially in undulating terrain and with different vegetation cover types. The aims were to develop policies to protect sensitive habitats. It is suggested that “no-spray” buffer zones in excess of 160–180 m are needed to minimise risk. Protection of rare ferns from overstorey vegetation or from steep slopes did not occur. Although less drift was found upwind there was significant damage at the end of the helicopter runs because of errors in switching the sprayer on and off. 相似文献
130.
ABSTRACT The abundant, high-quality waters of the Yellowstone River Basin have fostered a strong agricultural-based economy in eastern Montana. The region also contains the nation's largest strippable coal reserves. Numerous conflicts have developed around the mining of coal and in-state conversion of coal into electricity and synthetic fuels – processes that require large volumes of water. Competition for water among industrialists, agriculturalists, and others is a critical state issue. Probable effects of increased water diversions, the nature of water-energy conflicts, and state efforts to control development are discussed. 相似文献