全文获取类型
收费全文 | 2137篇 |
免费 | 153篇 |
国内免费 | 610篇 |
专业分类
安全科学 | 32篇 |
废物处理 | 8篇 |
环保管理 | 350篇 |
综合类 | 1509篇 |
基础理论 | 535篇 |
污染及防治 | 179篇 |
评价与监测 | 66篇 |
社会与环境 | 204篇 |
灾害及防治 | 17篇 |
出版年
2024年 | 10篇 |
2023年 | 15篇 |
2022年 | 50篇 |
2021年 | 64篇 |
2020年 | 60篇 |
2019年 | 68篇 |
2018年 | 56篇 |
2017年 | 77篇 |
2016年 | 102篇 |
2015年 | 111篇 |
2014年 | 93篇 |
2013年 | 153篇 |
2012年 | 192篇 |
2011年 | 226篇 |
2010年 | 177篇 |
2009年 | 183篇 |
2008年 | 152篇 |
2007年 | 181篇 |
2006年 | 220篇 |
2005年 | 165篇 |
2004年 | 90篇 |
2003年 | 108篇 |
2002年 | 62篇 |
2001年 | 69篇 |
2000年 | 52篇 |
1999年 | 48篇 |
1998年 | 18篇 |
1997年 | 12篇 |
1996年 | 23篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1981年 | 1篇 |
1980年 | 4篇 |
排序方式: 共有2900条查询结果,搜索用时 546 毫秒
631.
632.
633.
笔者从道路交通事故和景观方面 ,研究道路中央隔离设施的功能与特征。首先 ,利用对某城市道路中央有无隔离带情况下记录的交通事故数据 ,进行交通安全统计比较分析 ;其次 ,分别利用层次分析法和语言分级评价法 ,对城市道路中央双黄线、中央护栏隔离和中央绿化隔离 3种情况的景观进行分析 ;最后 ,通过综合分析给出分析结果 ,即中央绿化隔离、中央栅栏隔离带和双黄线隔离的评价顺序。 相似文献
634.
635.
636.
本文针对如何正确处理开发旅游资源与保护景观的关系,运用景观生态学原理,阐述了景观生态协调机制的基本内容和实现这一机制的途径. 相似文献
637.
M. Z. Moustafa 《Journal of the American Water Resources Association》1998,34(1):135-147
ABSTRACT: Anthropogenic phosphorus loading, mainly from the Everglades Agricultural Area (EAA), is believed to be the primary cause of eutrophication in the Everglades. The state of Florida has adopted a plan for addressing Everglades eutrophication problems by reducing anthropogenic phosphorus loads through the implementation of Best Management Practices (BMPs) in agricultural watersheds and the construction of stormwater treatment areas (STAs). Optimizing the effectiveness of these STAs for reducing phosphorus concentrations from agricultural runoff is a critical component of the District's comprehensive Everglades protection effort. Therefore, the objective of this study was to develop a simple tool that can be used to estimate STAs’performance and evaluate management alternatives considered in the Everglades restoration efforts. The model was tested at two south Florida wetland sites and then was used to simulate several management alternatives and predict ecosystem responses to reduced external phosphorus (P) loadings. Good agreement between model predictions at the two wetland sites and actual observations indicated that the model can be used as a management tool to predict wetlands’response to reductions in external phosphorus load and long-term P levels in aquatic ecosystems. Model results showed that lowering P content of the Everglades Protection Area (EPA) depends on reducing P loads originating from EAA discharges, not from rainfall. Assuming no action is taken (e.g., no BMPs or STAs implemented), the steady state model predicted that the average concentration within the modeled area of the marsh would reach 20 μg L?1 within five years. With an 85 percent reduction in P loading, the steady-state model predicted that Water Conservation Area 2A (WCA-2A) P concentration will equilibrate at approximately 10 μ L?1, while elimination of all loadings is projected to further reduce marsh P to values less than 10 μg L?1. 相似文献
638.
试论旅游经济与环境保护的关系——以香溪河风景线为例 总被引:5,自引:1,他引:4
阐述了旅游经济与环境保护矛盾的由来;分析了旅游经济系统,景观生态系统的结构与功能。指出旅游经济系统的旅游产品结构、旅游行业结构同环境保护关系最为密切,只有对其结构实行优化,才可能解决它们与景观生态系统结构之间的矛盾,把旅游经济活动对生态与环境影响降低到最小程度。旅游经济系统功能与景观生态系统功能,受其经济影响也经常处于矛盾状态之中。自然景观生态系统是通过食物链和食物网进行物质、能量传递的,倘若旅游 相似文献
639.
640.
Bruce K. Ferguson 《Journal of the American Water Resources Association》1987,23(1):147-152
ABSTRACT: The increasing use of irrigation for urban landscapes is causing new demands for efficient watering systems. Conservation techniques for irrigated agricultural fields cannot be applied to urban landscapes without amendment. This paper attempts to review methods of urban landscape water conservation in the context of the diversity and complexity of urban landscapes and the demands upon them for quality of the urban environment. A development's initial site layout and planting design fundamentally determine how much irrigation water will be required; the complexity and creativity inherent in urban design open a number of specific possibilities for reducing water demand. Irrigation hardware is then designed to deliver the required volume of water to the specified landscape efficiently by implementing a number of physical and operational principles. Maintenance of the finished development involves monitoring results and making adjustments as the plantings grow and develop. The potential for conserving urban irrigation water is large. Effective conservation need not compromise other qualities of the urban environment such as aesthetics, screening, or shade. Urban design can address both the kinds of landscapes people need, and minimal consumption of irrigation water. 相似文献