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   8075篇
  免费   567篇
  国内免费   269篇
安全科学   1617篇
废物处理   138篇
环保管理   3055篇
综合类   2125篇
基础理论   806篇
环境理论   10篇
污染及防治   204篇
评价与监测   331篇
社会与环境   345篇
灾害及防治   280篇
  2023年   85篇
  2022年   109篇
  2021年   179篇
  2020年   243篇
  2019年   190篇
  2018年   165篇
  2017年   219篇
  2016年   307篇
  2015年   253篇
  2014年   316篇
  2013年   455篇
  2012年   450篇
  2011年   571篇
  2010年   385篇
  2009年   491篇
  2008年   358篇
  2007年   470篇
  2006年   467篇
  2005年   361篇
  2004年   392篇
  2003年   296篇
  2002年   278篇
  2001年   270篇
  2000年   270篇
  1999年   205篇
  1998年   131篇
  1997年   135篇
  1996年   108篇
  1995年   105篇
  1994年   49篇
  1993年   62篇
  1992年   57篇
  1991年   47篇
  1990年   33篇
  1989年   27篇
  1988年   34篇
  1987年   33篇
  1986年   27篇
  1985年   23篇
  1984年   27篇
  1983年   17篇
  1982年   22篇
  1981年   18篇
  1980年   24篇
  1979年   33篇
  1978年   21篇
  1975年   14篇
  1973年   14篇
  1972年   16篇
  1971年   14篇
排序方式: 共有8911条查询结果,搜索用时 15 毫秒
991.
Analysis tools that combine large spatial and temporal scales are necessary for efficient management of wildlife species, such as the burrowing owl (Athene cunicularia). We assessed the ability of Ripley’s K-function analysis integrated into a geographic information system (GIS) to determine changes in burrowing owl nest clustering over two years at NASA Ames Research Center. Specifically, we used these tools to detect changes in spatial and temporal nest clustering before, during, and after conducting management by mowing to maintain low vegetation height at nest burrows. We found that the scale and timing of owl nest clustering matched the scale and timing of our conservation management actions over a short time frame. While this study could not determine a causal link between mowing and nest clustering, we did find that Ripley’s K and GIS were effective in detecting owl nest clustering and show promise for future conservation uses.  相似文献   
992.
Advocates of community-based approaches to environmental management argue that by respecting local circumstances, skills, and concerns we may improve the prospects of achieving environmental sustainability; yet, within nation states such as Canada, environmental conditions, management and enforcement costs and capabilities, and power differentials within and among civic and public sectors may result in a highly differentiated capacity for environmental management across different localities and regions. This article draws on insights of political ecology to 1) create a conceptual framework that identifies key elements shaping regional environmental management regimes and to 2) undertake a comparative analysis to assess how elements interact to generate uneven management outcomes. I compare experiences of two Canadian biosphere reserves designated in 2000: Clayoquot Sound, BC; and Redberry Lake, SK. Analysis reveals that differences in governance and institutional capacities in the biosphere reserves are key to explaining uneven local outcomes. Where the public and civic sectors are strong, a robust and publicly vetted form of management will emerge. Where these sectors are weak and land is held as private property, environmental nongovernmental organizations can set the type and level of management, to the exclusion of effective civic and state involvement. This result may improve environmental sustainability but hinder social sustainability of a management regime and raises questions about the efficacy of community-based management.  相似文献   
993.
The National Park Service (NPS) is increasingly focusing on alternative transportation systems in national parks to address environmental and social problems arising from a historical reliance on personal automobiles as the primary means of visitor access. Despite the potential advantages, alternative transportation may require a reorientation in the way that Americans have experienced national parks since the advent of auto-tourism in the early twentieth century. Little research exists, however, on visitor perspectives towards alternative transportation or the rationale underlying their perspectives. It remains unclear how transportation systems affect visitors’ experiences of the park landscape or the factors influencing their travel behavior in the parks. This report presents an interpretive study of visitor perspectives toward transportation management in the Yosemite Valley area of Yosemite National Park, California. Qualitative analysis of 160 semi-structured interviews identified individual psychological factors as well as situational influences that affect visitors’ behavior and perspectives. Individual psychological factors include perceived freedom, environmental values and beliefs, prior experience with Yosemite National Park and other national parks, prior experience with alternative transportation in national parks, and sensitivity to subjective perceptions of crowding. Situational factors included convenience, access, and flexibility of travel modes, as well as type of visit, type of group, and park use level. Interpretive communication designed to encourage voluntary visitor use of alternative transportation should focus on these psychological and situational factors. Although challenges remain, the results of this study suggest approaches for shaping the way Americans visit and experience their national parks to encourage environmental sustainability.  相似文献   
994.
Criteria for the Assessment of Sustainable Water Management   总被引:2,自引:1,他引:1  
Pressure on the world’s water resources is increasing, restraining social and economic development in many countries, and threatening ecological values in others. In order to manage water resources in a more sustainable manner, new planning methodologies/processes for river basin management need to be developed. This study attempts to construct a set of useable normative criteria for the analysis and evaluation of such processes. The criteria were designed as a response to the lack of deductive approaches in the evaluation of methodologies and working procedures used in the context of river basin management, making it possible to highlight their potential for sustainable development. The criteria are based on the twin concepts of participation and integration. These concepts function as well-established dimensions of both sustainable development and sustainable river basin management, and they are of significant methodological relevance. A synthesis of the key aspects connected to the two concepts is undertaken, based on a broad literature review. Focus is laid on how in methodological terms, and in relation to regional water management, to achieve participation and integration in a decision-making or planning process. The criteria are concerned with how knowledge and values are integrated into the planning process and how commitment, legitimacy, or acceptance for the resulting plan is generated.  相似文献   
995.
Naturally complete mixing promotes the spontaneous redistribution of dissolved oxygen(DO), representing an ideal state for maintaining good water quality, and conducive to the biomineralization of organic matter. Water lifting aerators(WLAs) can extend the periods of complete mixing and increase the initial mixing temperature. To evaluate the influence of artificial-induced continuously mixing on dissolved organic matter(DOM) removal performance, the variations of DOM concentrations, optical cha...  相似文献   
996.
近年来,我国大气环境、水环境和土壤环境质量得到一定的改善,“碧水蓝天”已经成为常态.但随着持久性有机污染物、内分泌干扰物、抗生素和微塑料等新污染物在环境中不断被检出,新污染物正逐步受到广泛的关注,壬基酚作为一种典型的内分泌干扰物也备受研究人员的关注.系统地概括了我国水体中壬基酚的环境行为和暴露水平,并基于风险商法和联合概率曲线法对壬基酚可能造成的生态风险进行了评估.结果表明,壬基酚对水生生物的毒性效应主要包括急性毒性、生长发育毒性、雌激素效应和繁殖毒性;壬基酚在我国主要流域水体中普遍存在,其浓度平均值在60~1 000 ng·L-1,浓度最高值可达4 628 ng·L-1;基于风险商法和联合概率曲线法的风险评估结果表明,壬基酚对我国主要流域里的水生生物均存在一定的风险.最后,总结了目前比较常用的壬基酚处理处置和风险管控技术,比较了国际上内分泌干扰物的监管方法,针对我国在新污染物环境管理中存在的问题,提出了针对性政策建议,研究结果可以为我国新污染物管理和管控提供参考.  相似文献   
997.
基于塔里木河流域生态系统特征,分析塔里木河流域生态系统管理面临的主要问题.①农业开发大量挤占生态用水,威胁流域生态系统安全;②流域农药使用量增长1.78倍,化肥使用量增长2.06倍,工业SO2排放量增长5.93倍,城镇污水量增长0.23倍,下游水质严重超标;③水资源利用效率仅为6.79元/m3,远低于新疆平均水平;④人口和种植规模年均增长11%以上,突破流域水资源承载力.从综合生态管理体制、生态资源市场交易机制、生态立法三方面提出塔里木河流域生态系统管理新方向.  相似文献   
998.
通过对山东省自然保护区进行研究发现,山东省自然保护区建设与管理虽然在自然保护区建设规模、类型、管护能力和主要保护对象等方面取得了新的成绩,但同时也存在自然保护区多区交叉重叠、资源本底不清、管护压力大与能力不足等新问题。随着国家公园、主体功能区和生态补偿制度的实施,山东省自然保护区建设与管理应深化自然保护区管理体制改革,提升自然保护区建设质量,加强自然保护区基础设施规范化建设。  相似文献   
999.
The rapid increase of phosphorus (P) use in farming has raised concerns regarding its conservation and environmental impact. Increasing the P use efficiency (PUE) is an approach to mitigating these adverse impacts. In this study, we applied substance flow analysis (SFA) to establish a life-cycle P use efficiency model to determine the life-cycle PUE of the farming system used in Anhui Province in 2011, which is typical of the agriculture practiced in central China. Based on this model, the P flows and PUEs of five subsystems were identified and quantified: crop farming, crop processing, livestock breeding, rural living, and urban living. The three largest P flows were found in the crop farming and livestock breeding subsystems; it can therefore be concluded that these subsystems have substantial impacts on the entire farming system. In contrast, the PUEs of crop farming, rural consumption, and livestock breeding subsystems presented the three lowest PUEs (58.79%, 71.75%, and 76.65%, respectively). These results were also consistent with the finding that the greatest P losses occurred in crop farming and livestock breeding. Consequently, the study proposes that great potential exists for increasing PUEs in the farming system of Anhui, and several of the most promising measures could be combined for improving PUEs. Finally, the study assesses data quality and presents a sensitivity analysis for use in interpreting the results. The study also shows that improving PUE and decreasing P losses in farming systems through improved nutrient management must be considered an important issue, and this study represents valuable experience in resource conservation and agricultural development in China.  相似文献   
1000.
Municipal solid waste (MSW) services of developing countries often suffer due to the lack of financial and operational autonomy, scientific approach, and adequate levels of resources. The solid waste management (SWM) practices of developed countries are benefited in cost and efficiency due to the participation of private players and sound financial management. However, developing economies depend on local municipalities to own and operate SWM services amidst structural and financial inefficiency. With the demands of augmenting efficient and cost-effective SWM services to the expanding population of cities and towns of newly industrialized nations on the rise, the municipalities in these countries are under pressure to adopt ways and means that can support efficient utilization of resources and improved decision-making capabilities. This research article reflects the current state of the MSW services in India and explores full cost accounting (FCA) framework in its ability to generate information on cost-related aspects and sustainable deployment of resources. Lastly, the extensibility of FCA is tested by integrating externalities of MSW services.  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