全文获取类型
收费全文 | 319篇 |
免费 | 38篇 |
国内免费 | 82篇 |
专业分类
安全科学 | 45篇 |
废物处理 | 16篇 |
环保管理 | 64篇 |
综合类 | 197篇 |
基础理论 | 37篇 |
污染及防治 | 54篇 |
评价与监测 | 7篇 |
社会与环境 | 8篇 |
灾害及防治 | 11篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 13篇 |
2020年 | 12篇 |
2019年 | 22篇 |
2018年 | 8篇 |
2017年 | 11篇 |
2016年 | 14篇 |
2015年 | 21篇 |
2014年 | 13篇 |
2013年 | 22篇 |
2012年 | 35篇 |
2011年 | 23篇 |
2010年 | 30篇 |
2009年 | 27篇 |
2008年 | 10篇 |
2007年 | 27篇 |
2006年 | 21篇 |
2005年 | 18篇 |
2004年 | 22篇 |
2003年 | 10篇 |
2002年 | 15篇 |
2001年 | 10篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有439条查询结果,搜索用时 328 毫秒
391.
随着城市轻轨建设的发展,交通噪声污染逐渐引起人们重视。在轻轨桥架两侧设置声屏障是控制轨道噪声的重要措施之一。声屏障的高昂成本往往是由不合理的设计参数造成的,通过对目前声屏障设计方法进行分析,提出了轻轨桥架声屏障优化设计方法。该方法以声屏障建造成本为目标函数,以降噪要求为声学约束,综合考虑设置位置、高度和长度等设计变量的影响;由列车噪声1/3倍频程频谱计算插入损失,提高了优化过程中插入损失的计算精度。该优化设计法与目前设计方法对比,验证了声屏障优化设计在改善降噪性能和经济性能方面的优越性。讨论了设计参数对成本和降噪性能的影响,并且对轨边矮墙的降噪性能进行了分析,所获的结论对声屏障和轨边矮墙设计参数与形状的选择具有指导意义。 相似文献
392.
Brazil’s Samuel Dam: Lessons for Hydroelectric Development Policy and the Environment in Amazonia 总被引:3,自引:0,他引:3
Fearnside PM 《Environmental management》2005,35(1):1-19
Brazil’s Samuel Dam, which formed a 540-km2 reservoir in the state of Rondônia in 1988, provides lessons for development decisions throughout Amazonia and in other tropical areas. The decision to build the dam was heavily influenced by its role in the political strategies of key decision makers. Samuel illustrates both impacts and benefits of electricity supply and the dilemmas facing decision makers regarding the various options for planned electricity generation. Environmental costs included flooding forest and stimulating illegal logging activity throughout western Amazonia because of an exception opened for Samuel in Brazil’s prohibition of export of raw logs. Samuel emitted substantially more greenhouse gases than would have been emitted by generating the same amount of electricity from oil. Contamination of fish in the reservoir resulted from methylation of mercury present in the soil. Social costs of the dam included resettlement of 238 families of farmers; impacts on indigenous people were indirect. Mitigating measures included faunal rescue and creation of a forest reserve. The lessons of Samuel include the need to consider a full range of alternatives prior to making decisions in practice and the importance of adhering to the logical sequence of decision making, where information is gathered and compared prior to the decision. It also shows the need to maintain flexibility when the costs and benefits of different alternatives change significantly over the course of the project’s planning and execution, as occurred at Samuel. 相似文献
393.
Richard H. McCuen 《Journal of the American Water Resources Association》1980,16(3):546-549
ABSTRACT: The fact that dams have failed indicates that there is still a risk involved, in spite of the major effort to ensure reliability. In seeking ways to reduce the risk, all aspects of the design, construction, monitoring, inspection, and rehabilitation of earth dams should be examined. Because dam classification is a central element, ways of minimizing uncertainty associated with classification need to be considered. A Bayesian approach to classification has numerous advantages over existing methods of earth dam classification because it directly evaluates the effects of uncertainties. A framework for incorporating Bayesian decision theory into the classification process is presented. 相似文献
394.
分析了某电厂厂界噪声超标的原因,根据噪声源的噪声特性,提出了厂界噪声综合治理方案,对隔声墙进行了设计,并对效果进行了计算和预测。 相似文献
395.
隔声技术在民用工程中的应用 总被引:5,自引:1,他引:5
叙述了隔声技术在民用工程噪声控制中的几种应用 ,特别对固定式和活动式声屏障的设计方法、使用效果作了介绍。声屏障用于降低以空气动力性噪声为主的水泵、风机、冷却塔等噪声源 ,结合室内吸声处理能收到明显的效果。 相似文献
396.
基于生态安全格局的国土空间生态保护修复关键区域诊断与识别——以烟台市为例 总被引:5,自引:1,他引:5
山水林田湖草系统生态保护修复是维护国家生态安全的重要保障。当前国土空间生态保护修复研究缺乏从生态系统的完整性和结构连通性角度对国土空间生态保护修复关键区域进行诊断和识别。烟台市作为我国典型滨海城市,湿地退化,生境类型单一造成景观稳定性差,国土空间生态保护修复刻不容缓。为全面识别烟台市国土空间生态保护修复关键区域,利用生境质量模型、生境风险评估模型、粒度反推法、最小累积阻力模型和电路理论,通过构建区域生态安全格局,诊断生态“夹点”、生态障碍点、生态断裂点等,识别和确定研究区域的国土空间生态保护修复关键区域。研究发现:(1)烟台市生态源地共计668.85 km2,主要为林地、水域,源间廊道共计1548.36 km,呈现“两横两纵”的空间特征;(2)基于生态安全格局识别烟台生态保护修复关键区域,包括13处生态“夹点”区域、8处生态障碍点区域、39处生态断裂点区域、破碎生态空间1308.66 km2;(3)结合各类生态保护修复关键区域的空间分布特征、土地利用现状,分别提出修复提升方向。研究可为国土空间生态保护修复关键区域识别、生态系统整体修复提升提供科学指导。 相似文献
397.
Evolution of the mate recognition system (MRS) can play a central role in animal speciation. One dramatic consequence of changes
in the MRS is the failure of individuals from divergent lineages to successfully court and mate, thereby reducing gene flow
between these groups. Here, we test the role of an acoustic mating signal on mate choice in a Hawaiian cricket genus (Gryllidae:
Laupala). Speciation in Laupala is proceeding at an extremely rapid rate, apparently driven by divergence in aspects of the mate recognition system, most
conspicuously the pulse rate of male calling song. Previous studies demonstrate that females prefer the pulse rate of a conspecific
male’s song when perceived at long range, in laboratory phonotaxis trials. In this study, we examined mate choice in two species
that differ dramatically in pulse rate: Laupala paranigra and Laupala kohalensis. We tested the female’s preference in both species for pulse rates at close range, by providing females an opportunity to
mate with hybrid males producing a range of intermediate pulse rates. Results of our study demonstrate that while strong behavioral
barriers exist between these two species, variation in the pulse rate of male calling song did not predict female mate choice
at close range. These results suggest a more complex architecture to mate recognition in Laupala than previously hypothesized. 相似文献
398.
399.
400.
城市高架公路新型声屏障设计、试验及应用 总被引:1,自引:0,他引:1
探讨了声屏障的声学设计、结构设计、强度设计方法 ,介绍了新型城市高架公路声屏障的试验室测试结果和应用情况 ,这种声屏障平均吸声系数为 0 7,平均隔音量为 30dB ,是控制城市高架公路噪声的有效设施 ,在上海外环线应用取得良好效果 相似文献