全文获取类型
收费全文 | 147篇 |
免费 | 74篇 |
国内免费 | 46篇 |
专业分类
安全科学 | 21篇 |
废物处理 | 4篇 |
环保管理 | 31篇 |
综合类 | 172篇 |
基础理论 | 12篇 |
污染及防治 | 10篇 |
社会与环境 | 15篇 |
灾害及防治 | 2篇 |
出版年
2024年 | 8篇 |
2023年 | 28篇 |
2022年 | 24篇 |
2021年 | 11篇 |
2020年 | 13篇 |
2019年 | 8篇 |
2018年 | 11篇 |
2017年 | 13篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 19篇 |
2013年 | 16篇 |
2012年 | 12篇 |
2011年 | 13篇 |
2010年 | 16篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 10篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1987年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有267条查询结果,搜索用时 15 毫秒
241.
中国人口老龄化:健康不安全及应对政策 总被引:2,自引:0,他引:2
中国不仅是世界上老龄人口增加最快的国家,也是老龄人口数量最多的国家,面临的老年健康不安全的挑战已成为社会发展最突出的挑战之一。如何构建一个老年健康友好型的社会,已不仅仅是为老年人群谋福求利的问题,更成为攸关当代社会全体人群未来切身利益、进而如何营造一个和谐、公平、可持续发展的重大社会问题和国家发展战略问题。本文提出通过制定和实施旨在投资于老年健康的基本公共卫生服务政策,发展服务于老年健康的产业体系,开发老年医学科学与研究系统,建立公平有效的社会保障与支持系统,建设和谐发展的社会支持系统等一系列政策及体系目标,构建老年健康友好型社会政策体系,以促进老年人口乃至全社会的健康发展,保障人类安全,缩小健康差距,消除健康贫困。 相似文献
242.
Effects of dissolved oxygen and iron aging on the reduction of trichloronitromethane, trichloracetonitrile, and trichloropropanone 总被引:1,自引:0,他引:1
Iron metal (Fe(0)) is a potent reductant capable of reducing a wide variety of halogenated organic compounds including disinfection byproducts (DBPs). These reduction reactions may play a role in DBP fate in iron water mains and potentially could be exploited to remove DBPs from drinking water or wastewater in a packed-bed configuration. Oxidants (i.e., dissolved oxygen (DO) and chlorine) present in the water, however, may decrease the DBP degradation rate by competing for reactive sites and rapidly aging or corroding the iron surface. Thus, batch experiments were performed to investigate the effect of DO on the degradation rates of selected DBPs by Fe(0). Experiments were performed under anaerobic conditions, in initially oxygen saturated buffer without DO control, and under controlled DO (approximately 4.0 or 8.0 mg l−1) conditions. The effect of short-term (25–105 min) iron aging in DO-containing buffer on DBP degradation rate also was investigated in separate experiments. For fresh Fe(0), the degradation rates of trichloronitromethane (TCNM) and trichloroacetonitrile (TCAN) in initially oxygen saturated buffer were similar to their respective rates under anaerobic conditions. The degradation rate of 1,1,1-trichloropropanone (1,1,1-TCP), however, decreased significantly in the presence of DO and the effect was proportional to DO concentration in the controlled DO experiments. For a DO concentration of 4 mg l−1, the degradation rate of the three DBPs was greater for longer aging times as compared to their respective rates after 25 min, suggesting the formation of a mineral phase that increased reactivity. For a DO concentration of 8 mg l−1, the effects of increasing aging time were mixed. TCNM degradation rates were stable for all aging times and comparable to that under anaerobic conditions. The TCAN and 1,1,1-TCP degradation rates, however, tended to decrease with increasing aging time. These results suggest that the reduction of highly reactive DBPs by Fe(0) will not be affected by the presence of DO but that the reaction rates will be slowed by DO for DBPs with slower degradation kinetics. 相似文献
243.
Abstract: Successful conservation efforts require understanding human behaviors that directly affect biodiversity. Choice of household location represents an observable behavior that has direct effects on biodiversity conservation, but no one has examined the sociocultural predictors of this choice relative to its environmental impacts. We conducted a case study of the Teton Valley of Idaho and Wyoming (U.S.A.) that (1) explored relationships between sociodemographic variables, environmental attitudes, and the environmental impact of household location choices, (2) assessed the potential for small household sizes in natural areas to multiply the environmental impacts of household location decisions, and (3) evaluated how length of residency predicted the environmental attitudes of people living in natural areas. We collected sociodemographic data, spatial coordinates, and land‐cover information in a survey of 416 households drawn from a random sample of Teton Valley residents (95% compliance rate). Immigrants (respondents not born in the study area) with the lowest education levels and least environmentally oriented attitudes lived in previously established residential areas in disproportionately high numbers, and older and more educated immigrants with the most environmentally oriented attitudes lived in natural areas in disproportionately high numbers. Income was not a significant predictor of household location decisions. Those living in natural areas had more environmental impact per person because of the location and because small households (<3 people/household) were 4 times as likely in natural areas as large households. Longer residency in natural areas predicted less environmentally oriented attitudes, suggesting that living in natural areas does not foster more concern for nature. Because populaces are rapidly aging, growing more educated, and potentially growing more environmentally oriented, these patterns are troubling for biodiversity conservation. Our results demonstrate a need for environmentalists to make household location decisions that reflect their environmental attitudes and future research to address how interactions between education level, environmental attitudes, population aging, and household location choices influence biodiversity conservation. 相似文献
244.
245.
针对在役老龄管线更换管段、在现有管线上添加装置、修复水下管段等进行修复时遇到的各类问题,提出了相应的解决方案和下一步需要完善的途径.介绍了封堵工艺的工作原理及其实际操作过程,采用封堵工艺能够实施老龄管线更新,从而确保老龄管线经济安全地运行. 相似文献
246.
本文在阐述自然资源代际转移实质的基础上,运用自然资源代际转移的基本模型分析了资源的代际分配关系。然后针对我国人口老龄化问题的特点,探讨了人口老龄化对自然资源代际转移的影响。 相似文献
247.
采用赤子爱胜蚓(Eisenia fetida)为测试生物,人工土壤为测试介质,Pb(NO3)2为土壤污染物,研究土壤老化对赤子爱胜蚓生长及繁殖的影响.结果表明,与对照组相比,污染土壤中赤子爱胜蚓体重随土壤中Pb(NO3)2浓度的升高呈现降低的趋势.Pb(NO3)2在人工土壤中老化0、7、28和84 d后,不同老化时间,Pb(NO3)2抑制赤子爱胜蚓的生长也不相同,影响最明显的是1 000 mg·kg-1和1 500 mg·kg-1试验组.不同老化时间的Pb(NO3)2对赤子爱胜蚓繁殖的影响有很大差异,其产茧量的半数有效浓度(EC50)分别为1 085.10、1 163.32、1 666.86和1 606.94 mg·kg-1;幼蚓孵化量的EC50分别为700.01、703.88、1 031.34和1 017.89 mg·kg-1.Pb(NO3)2在人工土壤中经过不同老化时间后,其对赤子爱胜蚓生长及繁殖的影响有很大的差异,这种差异影响到对土壤Pb(NO3)2污染的毒性评估,因此,进行Pb(NO3)2毒性试验时应考虑其在土壤中的老化作用.此研究结果可为老化土壤中污染物的生态风险评估以及土壤环境质量标准的制定提供科学依据. 相似文献
248.
The impacts of soil organic matter (SOM), aging and sterilization on the production of lignin peroxidase (LIP) and manganese peroxidase (MnP) by Phanerochaete chrysosporium during the biodegradation of pyrene in soils were investigated. The biodegradation of pyrene by P. chrysosporium decreased with increasing SOM content, whereas the maximum activities of LiP and MnP increased, which indicates that SOM outweighed pyrene in controlling enzyme production. Sterilization enhanced the degradation of pyrene due to the elimination of competition from indigenous microbes, whereas aging led to a reduction in the degradation of pyrene primarily through changes in its sorbed forms. Both sterilization and aging could reduce SOM content and alter its structure, which also influenced the bioavailability of pyrene and the enzyme activity. The sterilization and aging processes caused changes in the degradation of pyrene, and the enzyme activities were greater in soils with high SOM contents. MnP was related to the degradation of pyrene to a greater extent, whereas LiP was more related to the decomposition of SOM. 相似文献
249.
250.