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   161篇
  免费   8篇
  国内免费   21篇
安全科学   33篇
环保管理   16篇
综合类   72篇
基础理论   37篇
环境理论   1篇
污染及防治   5篇
评价与监测   14篇
社会与环境   2篇
灾害及防治   10篇
  2023年   7篇
  2022年   8篇
  2021年   11篇
  2020年   9篇
  2019年   8篇
  2018年   4篇
  2017年   2篇
  2016年   4篇
  2015年   2篇
  2014年   4篇
  2013年   2篇
  2012年   5篇
  2011年   16篇
  2010年   9篇
  2009年   26篇
  2008年   8篇
  2007年   9篇
  2006年   10篇
  2005年   7篇
  2004年   7篇
  2003年   7篇
  2002年   5篇
  2001年   3篇
  2000年   3篇
  1999年   4篇
  1998年   3篇
  1997年   1篇
  1993年   2篇
  1990年   1篇
  1986年   1篇
  1984年   1篇
  1974年   1篇
排序方式: 共有190条查询结果,搜索用时 15 毫秒
161.
Africa contains much of Earth's biological and cultural–linguistic diversity, but conserving this diversity is enormously challenging amid widespread poverty, expanding development, social unrest, and rapidly growing human population. We examined UNESCO (United Nations Educational, Scientific and Cultural Organization) Natural World Heritage Sites (WHSs) on continental Africa and nearby islands—48 protected areas containing globally important natural or combined natural and cultural resources—to gauge the potential for enlisting Indigenous peoples in their conservation. We used geographic information system technology to identify instances where Natural WHSs co-occur with Indigenous languages, a key indicator of cultural diversity. And, we compared the geographic ranges for 4 taxa and selected freshwater species with occurrence of all Indigenous languages within Natural WHSs and subsections of WHSs covered by the geographic extent of Indigenous languages to measure the correlation between linguistic and biological diversity. Results indicated that 147 languages shared at least part of their geographic extent with Natural WHSs. Instances of co-occurrence where a WHS, a language, or both were endangered marked localities particularly deserving conservation attention. We examined co-occurrence of all languages and all species, all languages and endangered species, and endangered languages and endangered species and found a correlation between linguistic and biological diversity that may indicate fundamental links between these very different measures of diversity. Considering only endangered species or endangered languages and species reduced that correlation, although considerable co-occurrence persisted. Shared governance of government-designated reserves is applicable for natural WHSs because it capitalizes on the apparent connection between culture and nature. Natural WHSs in Africa containing speakers of Indigenous languages present opportunities to conserve both nature and culture in highly visible settings where maintaining natural systems may rely on functioning Indigenous cultural systems and vice versa.  相似文献   
162.
The nitrate-nitrogen(NO 3-N) concentrations from shallow groundwater wells situated in 29 of the Chinese Ecosystem Research Network field stations,representing typical agroand forest ecosystems,were assessed using monitoring data collected between 2004 and 2010.Results from this assessment permit a national scale assessment of nitrate concentrations in shallow groundwater,and allow linkages between nitrate concentrations in groundwater and broad land use categories to be made.Results indicated that most of the NO 3--N concentrations in groundwater from the agroand forest ecosystems were below the Class 3 drinking water standard stated in the Chinese National Standard:Quality Standard for Ground Water(≤ 20 mg/L).Over the study period,the average NO 3--N concentrations were significantly higher in agro-ecosystems(4.1 ± 0.33 mg/L) than in forest ecosystems(0.5 ± 0.04 mg/L).NO 3-N concentrations were relatively higher(> 10 mg N /L) in 10 of the 43 wells sampled in the agricultural ecosystems.These elevated concentrations occurred mainly in the Ansai,Yucheng,Linze,Fukang,Akesu,and Cele field sites,which were located in arid and semiarid areas where irrigation rates are high.We suggest that improvements in N fertilizer application and irrigation management practices in the arid and semi-arid agricultural ecosystems of China are the key to managing groundwater nitrate concentrations.  相似文献   
163.
Effective environmental impact assessment and management requires improved understanding of the organization and transformation of ecosystems in which independent agents are linked through an intricate network of energy, matter, and informational interactions. While advances have been made, we still lack a complete understanding of the processes that create, constrain, and sustain ecosystems. Network environ analysis (NEA) provides one approach for building novel ecosystem insights, but it is model dependent. As ecological modeling is an imprecise art, often complicated by inadequate empirical data, the utility of NEA may be limited by model uncertainty. Here, we investigate the sensitivity of NEA indicators of ecosystem growth and development to flow and storage uncertainty in a phosphorus model of Lake Sidney Lanier, USA. The indicators are total system throughflow (TST), total system storage (TSS), total boundary input (Boundary), Finn cycling index (FCI), ratio of indirect-to-direct flows (Indirect/Direct), indirect flow index (IFI), network aggradation (AGG), network homogenization (HMG), and network amplification (AMP). Our results make two primary contributions. First, they demonstrate that five of the indicators – FCI, Indirect/Direct, IFI, AGG and HMG – are relatively robust to the flow and storage uncertainty in the Lake Lanier model. This stability lets us draw robust conclusions about the Lake Lanier ecosystem organization (e.g., phosphorus flux in the lake is dominated by internal processes) in spite of uncertainties in the model. Second, we show that the majority of the indicators co-vary and that most of their common variation could be mapped onto two latent factors, which we interpret as (1) system integration and (2) boundary influences.  相似文献   
164.
在对市环保局信访处理流程研究的基础上,开发一套自动化、无纸化的环保信访处理信息系统。  相似文献   
165.
农业气象灾害分析网络服务系统   总被引:3,自引:0,他引:3  
高苹  黄毓华 《灾害学》1999,14(1):80-84
以大量翔实的农业气象灾害资料为基础,结合实时农业气象灾情分析,在windowsNTServer网络环境下,研制出具有网络功能的农业气象灾害分析服务系统,系统在Internet的NetscapeNavigator或Explorerto览器下运行,简便实用.系统以灾害服务为宗旨,体现了信息量大、服务迅速的特点。内容包括农业气象灾害类型库、逐年农业气象灾害评判库、实时农业气象灾害分析及灾情服务流程.  相似文献   
166.
甲烷在自然生态系统碳循环过程中起着重要作用,氮素形态的差异影响了甲烷氧化菌的氧化作用.选取北京市密云水库和北运河两类不同污染类型的水体作为研究区域,采用克隆文库分子生物学的方法,探究氮素形态及其来源的差异对MOB细菌群落特征的影响.结果表明:密云水库与北运河沉积物中氮素形态有显著差异,水库中氮素以NO3--N为主,河流中氮素以NH4+-N为主;氮素形态的差异影响了MOB细菌的系统发育,密云水库沉积物中MOB细菌的高同源性菌群主要来自湖泊生态系统,与NO3--N有较强的响应关系,北运河沉积物中MOB细菌高同源性菌群主要来自污水处理厂废水和活性淤泥,与NH4+-N有较强的响应关系,不同环境中氮素对MOB细菌的影响主要依赖于氮素的主要存在形态及其主要来源.北运河等重污染河流中MOB细菌群落的联系更紧密更趋于模块化,对环境变化的敏感程度更高,微生物更脆弱,更容易受到水质变化以及人类活动的干扰.北运河沉积物中NH4+-N对MOB细菌氧化速率的抑制性强于密云水库沉积物中NO3--N对甲烷氧化的抑制作用.重污染的城市河流中高浓度的NH4+-N通过抑制甲烷氧化速率和促进产甲烷产生速率的双重作用影响了河流沉积物中甲烷的产生.  相似文献   
167.
存域网(SAN)在数字图书馆中信息安全的应用研究   总被引:2,自引:0,他引:2  
数字图书馆是图书馆信息化建设的必然趋势 ,通过采用存域网 (SAN ,StorageAreaNetwork)技术 ,可以保证图书馆数据信息的可靠与安全 ,笔者分析了根据不同的需求 ,采用不同的SAN拓扑结构 ,为图书馆信息网络建设提供了多种可靠的解决方案  相似文献   
168.
Only with a properly designed water quality monitoring network can data be collected that can lead to accurate information extraction. One of the main components of water quality monitoring network design is the allocation of sampling locations. For this purpose, a design methodology, called critical sampling points (CSP), has been developed for the determination of the critical sampling locations in small, rural watersheds with regard to total phosphorus (TP) load pollution. It considers hydrologic, topographic, soil, vegetative, and land use factors. The objective of the monitoring network design in this methodology is to identify the stream locations which receive the greatest TP loads from the upstream portions of a watershed. The CSP methodology has been translated into a model, called water quality monitoring station analysis (WQMSA), which integrates a geographic information system (GIS) for the handling of the spatial aspect of the data, a hydrologic/water quality simulation model for TP load estimation, and fuzzy logic for improved input data representation. In addition, the methodology was purposely designed to be useful in diverse rural watersheds, independent of geographic location. Three watershed case studies in Pennsylvania, Amazonian Ecuador, and central Chile were examined. Each case study offered a different degree of data availability. It was demonstrated that the developed methodology could be successfully used in all three case studies. The case studies suggest that the CSP methodology, in form of the WQMSA model, has potential in applications world-wide.  相似文献   
169.
Nowadays forestry faces a complex management situation; the understanding of sustainable forest management (SFM) has gone far beyond the original meaning of sustainable yield of timber. SFM strategies should fulfil ecological, economic and social functions without causing damage to other ecosystems. In this understanding, forest management actions cannot be seen as isolated or mono-causal. In this case study, indicators for SFM are arranged in a Pressure-State-Response (PSR) framework at forest management unit level. This framework links pressures on the environment caused by human activities with changes of environmental state (condition) parameters. Forest management also responds to these changes by instituting environmental and economic measures to reduce pressures and restore natural resources. The Analytic Network Process (ANP) is utilized to evaluate the performance of four management strategies with regard to the PSR framework on SFM. Priorities of indicators and alternatives are modelled with the ANP resulting from the interconnections to other indicators and their respective cumulative importance. The approach allows for more detailed information on the network of human influences and their impacts on forest ecosystems and goes beyond the limitations of flat-dimensioned indicator sets.  相似文献   
170.
This study is about 16 policy-induced innovation networks on climate change adaptation, i.e., subsidised multi-actor networks that are initiated by research institutes and formed around a particular real-life problem aiming at joint development, test, and implement adaptation measures. The political-administrative context is Germany, and the institutional context is a joint research framework in which each network works independently on a particular topic, but remains bound to the principle of practical and solution-oriented research carried out in close partnership between scientific and extra-scientific actors. Our objective is to provide empirical insights into the processes and outcomes of such networks and to systematically analyse the networks’ collaboration success and its influencing factors. To this end, collaboration success is operationalised as a three-dimensional metric including (1) the practitioners’ satisfaction with the cooperation, (2) their perceived learning effects, and (3) their perceived implementation capacity. Results show a decreasing level of success throughout the three dimensions and particularly a gap between knowledge acquisition and learning on the one hand and implementation, i.e., transforming the knowledge into action, on the other. While the positive relationship between these dimensions is confirmed, results of correlation analysis highlight the importance of repeated participation, appropriate information management, and inclusive as well as responsive network practices. We discuss the results against our existing knowledge on multi-actor collaborative research and deduce (methodological) lessons learnt as well as future research needs.  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