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   614篇
  免费   50篇
  国内免费   114篇
安全科学   11篇
废物处理   3篇
环保管理   107篇
综合类   364篇
基础理论   128篇
环境理论   1篇
污染及防治   10篇
评价与监测   50篇
社会与环境   53篇
灾害及防治   51篇
  2024年   2篇
  2023年   12篇
  2022年   25篇
  2021年   24篇
  2020年   16篇
  2019年   25篇
  2018年   19篇
  2017年   26篇
  2016年   37篇
  2015年   34篇
  2014年   29篇
  2013年   57篇
  2012年   43篇
  2011年   53篇
  2010年   43篇
  2009年   22篇
  2008年   14篇
  2007年   29篇
  2006年   41篇
  2005年   28篇
  2004年   16篇
  2003年   31篇
  2002年   18篇
  2001年   12篇
  2000年   22篇
  1999年   23篇
  1998年   12篇
  1997年   10篇
  1996年   16篇
  1995年   9篇
  1994年   4篇
  1993年   2篇
  1992年   4篇
  1991年   3篇
  1990年   2篇
  1988年   3篇
  1987年   2篇
  1983年   1篇
  1980年   2篇
  1977年   3篇
  1975年   2篇
  1973年   1篇
  1972年   1篇
排序方式: 共有778条查询结果,搜索用时 484 毫秒
321.
Integrated Coastal Zone Management as a strategy for achieving conservation and sustainable multiple use of the coastal zone includes various types of management initiatives. Due to natural phenomena such as tides and winds and to social and economic activities, coastal areas undergo transformation. Coastal erosion and the disappearance of beaches as a result of wrong planning decisions and lack of effective legislation are among the most damaging effects and to reverse them requires application of a series of engineering techniques. Beach nourishment projects as a way towards shore protection and utilization through recreational purposes in the Spanish and Italian coasts are noteworthy in this respect. In beach nourishment projects, the roles of various entities, both public and private, should be clearly indicated and in the evaluation and execution stage a series of questions should be answered for the successful completion of any nourishment project. Past projects in the Mediterranean and experiences from recent Italian projects in Anzio and Nettuno confirm this. For example, dredging of the entrance channel of the port of Anzio enabled middle-sized ferryboats once again to enter the port (which had not been possible before). This will in turn increase the tourism potential of the town. Nourishment of two beaches at these sites prevented further erosion and provided more area for recreational purposes. Expected economic contribution of beach nourishments to the regional authority was estimated for Nettuno and Anzio; the resulting theoretical payback period was found to be 3 yr for the former and 15 yr for the latter.  相似文献   
322.
The US Environmental Protection Agency's Office of Research and Development has initiated the Environmental Monitoring and Assessment Program (EMAP) to monitor status and trends in the condition of the nation's near coastal waters, forests, wetlands, agro-ecosystems, surface waters, deserts and rangelands. the programme is also intended to evaluate the effectiveness of Agency policies at protecting ecological resources occurring in these systems. Monitoring data collected for all ecosystems will be integrated for regional and national status and trends assessments. the near coastal component of EMAP consists of estuaries, coastal waters, and the Great Lakes. Near coastal ecosystems have been regionalized and classified, and an integrated sampling strategy has been developed. EPA and NOAA have agreed to coordinate and, to the extent possible, integrate the near coastal component of EMAP with the NOAA National Status and Trends Program. A demonstration project was conducted in estuaries of the mid-Atlantic region (Chesapeake Bay to Cape Cod) in the summer of 1990. in 1991, monitoring continued in mid-Atlantic estuaries and was initiated in estuaries of a portion of the Gulf of Mexico. Preliminary results indicate: there are no insurmountable logistical problems with sampling on a regional scale; several of the selected indicators are practical and sensitive on the regional scale; and an efficient effort in future years will provide valuable information on condition of estuarine resources at regional scales.  相似文献   
323.
Concentrations of 8 heavy metals:cadmium(Cd),copper (Cu),zinc(Zn),lead(Pb),nickel(Ni),chromium (Cr),antimony (Sb) and tin(Sn)were examined in 3 species of bivalves (Perna viridis,Crassostrea rivularis and Ruditapes philippinarum)collected from 25 sites along the Pearl River Delta coastal waters in the South China Sea from July to August 1996.In general,Cd,Cu,Zn and Sn concentrations in the three bivalve species collected from the Estuarine Zone were significantly higher than those collected from the Western and Eastern Zones of the Pearl River Delta,which are related to the existence of various anthropogenic activities in the catchment of the Pearl River Delta.The Western Estuarine Zone is mainly impacted by Cr,Ni and Cu contamination.In Victoria Harbor,heavy metal contamination is mainly due to Cu and Pb.Cd,Cu and Zn concentrations in oysters were significantly higher than those in mussels and clams.This could be explained by the fact that oysters live mainly in the Estuarine Zone of the Pearl River Delta which receives most of the polluting discharges from the catchment of the Delta.During turbid condition,heavy metals(soluble or adsorbed on suspended particulates)discharged from the Delta are filtered from the water column and subsequently accumulated into the soft body tissues of oysters.Heavy metal concentrations in the three bivalve species were compared with the maximum permissible levels of heavy metals in seafood regulated by the Public Health and Municipal Services Ordinance,Laws of Hong Kong, and it was revealed that Cd and Cr concentrations in the three bivalve species exceeded the upper limits.At certain hotspots in the Delta, the maximum acceptable daily load for Cd was also exceeded.  相似文献   
324.
京津冀地区是我国工业发展的核心区域之一 ,大耗水型的重化工结构突出 ,长期发展造成了地区水资源供需的尖锐矛盾 ,并导致了严重的区域环境问题。论文提出了以水资源高效利用为引导机制 ,调整工业结构,建立适水型工业体系是此地区工业发展的必然选择的观点 ;阐述了优化城市工业结构,发展清洁生产,建立滨海产业的建议与措施  相似文献   
325.
长乐—南澳构造带在中生代时期经历了多幕构造变形和多期变质作用。它们分别是:高角闪岩相变质作用—第一幕变形;低角闪岩相变质作用—第二幕变形;绿片岩相变质作用—第三幕变形。每一幕变形和每期变质作用均有各自的构造形迹和典型矿物共生组合。  相似文献   
326.
韩保新  林奎 《海洋环境科学》1998,17(4):70-74,80
从沿海WEDSS的系统目标和要求着手,提出并论述了沿海WEDSS的系统结构设计,并在此基础上建立了沿海WEDSS,从而使GIS,环境信息,预测模型和决策支持合为一体,最后介绍了该系统在大亚湾开发区环评中的应用。  相似文献   
327.
近海水域三维水动力学和水质的精细模型研究   总被引:3,自引:0,他引:3  
本文把研究近海水域水质污染与控制的三维精细预报系统作为目标。在分析近海环境中各种物理、化学和生物现象的基础上 ,针对近海水域水污染的特点 ,选定一个包含有二十多个状态变量及其相互作用的三维非线性系统作为研究和模拟对象 ,建立了一个统一考虑物理、化学和生物等过程综合作用的近海水域三维水动力学和水质的精细模型 ,并成功地应用于日本博多湾的水质模拟。  相似文献   
328.
山东海滨城市主要海洋地质灾害述评与减防灾措施探讨   总被引:3,自引:1,他引:3  
海滨城市的海洋地质灾害可分为两大类型:其一是由纯内外自然地质作用造成的危及城乡安全的灾害,如地震、断裂活动、海岸侵蚀、风暴潮;其二是人为活动与自然地质作用相互影响形成的灾害,如过量开采地下水和滥伐森林等引起的地面沉降、海水入侵与倒灌、不合理的海岸工程布局引起的海岸流场变化导致的岸线突变。本文目的在于探讨山东沿海这些灾害类型的分布与成因,进而提出减少或防止这些灾害危害的措施。  相似文献   
329.
BACKGROUND, AIMS AND SCOPE: The concentration of chlorinated dibenzo-p-dioxins and dibenzofurans in many fish from the Baltic requires monitoring, since it approaches or exceeds the European Union threshold limit value of 4 pg TEQ/g wet weight of fish for human consumption. The concentrations, expressed in TEQs, are important for toxicology and regulations, but hide the concentrations of the individual congeners, which are important for other environmental sciences, source allocation, and for the detection of measurement errors. This report evaluates the results of a survey reported earlier only in the terms of the TEQ concentrations. METHODS: Principal Component Analysis (PCA) was used to reduce the dimensions of the data (17 = 7 chlorinated dibenzo-p-dioxin and 10 chlorinated dibenzofuran congeners) to three principal components. This facilitated the interpretation of the congener profiles. Slopes of the congener concentrations as a function of age of the fish were estimated by least squares regression. The results were compared with a large set of data for lake trout from Lake Ontario. RESULTS AND DISCUSSION: The congener profiles of Baltic herring are less scattered than those of sprat. The profiles of herring from the central Baltic differ from those of herring from the Gulf of Riga and both appear to be affected relatively minimally by the age of the fish. The congener profiles of herring from the western Gulf of Finland are similar to those from the central Baltic, those from middle Gulf of Finland are similar to those from the Gulf of Riga. Both seem to be more affected by age of the fish than the profiles of the first two groups. The concentrations of several pentachloro- and hexachloro-dibenzo-p-dioxins and dibenzofurans increase with the age of the fish CONCLUSION: PCA is a good technique for the evaluation of the congener profiles. The resulting loading and score plots provide a good graphic summary of the multidimensional data. Additional analyses are needed to confirm the observed profile patterns. A comparison with the results of a long-term monitoring from another area shows that the age of the fish is a more important factor than the year of capture. RECOMMENDATION AND OUTLOOK: The surveys should continue for a number of years and the results should be presented and evaluated both in terms of the TEQs as well as in terms of weight concentrations. Since the concentrations do not appear to change very much from year to year, it would be better to carry out surveys only every 3-4 years and, instead, stratify the sampling according to age and gender of the fish, and to analyze replicate extracts by replicate measurements. The inclusion of unmarked replicate samples would be a good quality assurance measure. It would be desirable to analyze additional parts of the food chain in order to understand the fate of the compounds in the ecosystem.  相似文献   
330.
ABSTRACT: The purpose of this paper is to describe a land use and environmental planning model. Map overlays were used for analyzing and aggregating economic, social, and environmental data. Various land use categories were evaluated using a numerical scoring system. These scores were then used to assist in the development of land use regulations in a coastal county in South Carolina.  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