全文获取类型
收费全文 | 465篇 |
免费 | 40篇 |
国内免费 | 72篇 |
专业分类
安全科学 | 78篇 |
废物处理 | 32篇 |
环保管理 | 73篇 |
综合类 | 255篇 |
基础理论 | 33篇 |
污染及防治 | 48篇 |
评价与监测 | 25篇 |
社会与环境 | 22篇 |
灾害及防治 | 11篇 |
出版年
2023年 | 2篇 |
2022年 | 17篇 |
2021年 | 18篇 |
2020年 | 21篇 |
2019年 | 14篇 |
2018年 | 16篇 |
2017年 | 20篇 |
2016年 | 15篇 |
2015年 | 21篇 |
2014年 | 22篇 |
2013年 | 26篇 |
2012年 | 40篇 |
2011年 | 38篇 |
2010年 | 34篇 |
2009年 | 26篇 |
2008年 | 17篇 |
2007年 | 37篇 |
2006年 | 34篇 |
2005年 | 25篇 |
2004年 | 14篇 |
2003年 | 23篇 |
2002年 | 9篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有577条查询结果,搜索用时 46 毫秒
531.
532.
Elemental Conservation Units: Communicating Extinction Risk without Dictating Targets for Protection
Abstract: Conservation biologists mostly agree on the need to identify and protect biodiversity below the species level but have not yet resolved the best approach. We addressed 2 issues relevant to this debate. First, we distinguished between the abstract goal of preserving the maximum amount of unique biodiversity and the pragmatic goal of minimizing the loss of ecological goods and services given that further loss of biodiversity seems inevitable. Second, we distinguished between the scientific task of assessing extinction risk and the normative task of choosing targets for protection. We propose that scientific advice on extinction risk be given at the smallest meaningful scale: the elemental conservation unit (ECU). An ECU is a demographically isolated population whose probability of extinction over the time scale of interest (say 100 years) is not substantially affected by natural immigration from other populations. Within this time frame, the loss of an ECU would be irreversible without human intervention. Society's decision to protect an ECU ought to reflect human values that have social, economic, and political dimensions. Scientists can best inform this decision by providing advice about the probability that an ECU will be lost and the ecological and evolutionary consequences of that loss in a form that can be integrated into landscape planning. The ECU approach provides maximum flexibility to decision makers and ensures that the scientific task of assessing extinction risk informs, but remains distinct from, the normative social challenge of setting conservation targets. 相似文献
533.
1 and C2 hydrocarbons (trichloroethane, trichloroethene, tetrachloroethene, dichloromethane). Measures aiming at the reduction of
toxic emissions and ozone depletion potential (ODP) may possibly lead to a shift of environmental impacts towards higher energy
consumption, emission of waste water, and volatile organic compounds (VOC) with photochemical oxidant creation potential (POCP).
The present article concerns itself with a life cycle assessment of the three main degreasing processes in order to compare
their integral environmental impacts with one another. This is supplemented by presenting the methodology of the life cycle
inventory life cycle inventory analysis (LCI). Generally, the applicability of the established LCI method can be shown quite
clearly. However, some difficulties arise, especially at the stage of the goal definition, as the use of the process and the
functional unit cannot be pinned down as easily and neatly as for most other products. The definition of the use of the process
and the functional unit is not as straightforward as for most products. Among the potential functional units identified are
the mass of removed impurities, cleaning time, cleaning work, percentage of purity, throughput of parts, loads, mass or surface
and virtual coefficients. The mass of removed impurities turned out to be the most suitable parameter for measuring the technical
performance of degreasing processes. The article discusses background, purpose, scope, system boundaries, target group, process
tree and representativeness of the present study. 相似文献
534.
人工湿地污水处理系统中构建天然蛭石缓冲单元可行性研究 总被引:1,自引:0,他引:1
为提高人工湿地污水处理的冬季处理效果,建议在人工湿地处理系统中构建缓冲单元,并将天然蛭石作为缓冲单元的主体填料.结果表明:在水力负荷为1.4 m3/(m2·d)和蛭石层填充高度≥60 cm的条件下,对于经初沉处理的生活污水(COD值为150-350 mg/L,NH4 -N为10-30 mg/L,TP为1.0-1.5 mg/L),无植物天然蛭石缓冲单元至少可在45 d内保持其出水各项水质指标达到一级排放标准,从而可基本满足人工湿地在植物换季时期的处理需要.另外,适当增加系统含氧量和蛭石用量可提高体系缓冲性能. 相似文献
535.
536.
膜蒸馏是将膜与蒸馏过程相结合的分离方法,是一种节能高效的分离技术。本文从其过程机理出发,展望了该技术在苦咸水淡化技术中应用的前景。 相似文献
537.
一种分析城市代谢系统互动关系的方法 总被引:4,自引:0,他引:4
提出一种集成了能值分析和生态网络分析,研究城市代谢系统组分间互动关系的方法.基于城市复合生态系统和城市代谢的基本原理,在确定城市系统代谢单元和代谢环节的基础上,采用提出的方法,分析了城市代谢单元之间掠夺、限制和共生的关系.最后,以中国北京、上海、天津、重庆、广州和深圳6大城市为例进行了实证研究.结果表明,天津、重庆、广州市社会经济子系统对自然生态子系统存在着掠夺关系;北京、上海和深圳市自然生态子系统对社会经济子系统存在着限制关系;实现城市代谢系统良性运行的前提在于调控代谢单元间的互动关系,促进城市代谢单元间的协调共生. 相似文献
538.
地勘单位安全生产存在的问题及对策研究 总被引:1,自引:0,他引:1
针对地勘单位安全生产现状及存在的主要问题,采用系统的理论和方法,从人、机、环境、管理4个要素入手进行分析和研究,并从如何改善安全环境、加强职工安全教育和培训、落实安全责任制、加强安全机构和安全管理人员队伍建设、建立行业安全监管体系等方面有针对性地提出了改进的对策和措施,以促进地勘单位健康、和谐、持续的发展. 相似文献
539.
介绍了研制开发的油罐浮舱检查器的结构及试验情况,试验表明采用油罐浮舱检查器进行大型储油罐的浮舱检查,既提高了工作效率,又可避免人员中毒等事故的发生。 相似文献
540.
Deyin Hou Jun Wang Changwei Zhao Baoqiang Wang Zhaokun Luan Xiangcheng Sun 《环境科学学报(英文版)》2010,22(12):1860-1867
The direct contact membrane distillation applied for fluoride removal from brackish groundwater was investigated.The self-prepared polyvinylidene fluoride membrane exhibited high rejection of inorganic salt solutes.The maximum permeate flux 35.6 kg/(m2 ·hr) was obtained with the feed solution at 80°C and the cold distillate water at 20°C.The feed concentration had no significant impact on the permeate flux and the rejection in fluoride.The precipitation of CaCO3 would clog the hollow fiber inlets and foul the membrane surface with increasing concentration factor when natural groundwater was used directly as the feed,which resulted in a rapid decline in the module efficiency.This phenomenon was diminished by acidification of the feed.The experimental results showed that the permeate flux and the quality of obtained distillate kept stable before concentration factor reached 5.0 with the acidified groundwater as feed.The membrane module efficiency began to decline gradually when the feed continued to be concentrated,which can be mainly attributed to the formation of CaF2 deposits on the membrane surface.In addition,a 300 hr continuous fluoride removal experiment of acidified groundwater was carried out with concentration factor at 4.0,the permeate flux kept stable and the permeate fluoride was not detected. 相似文献