全文获取类型
收费全文 | 183篇 |
免费 | 23篇 |
国内免费 | 26篇 |
专业分类
安全科学 | 67篇 |
废物处理 | 7篇 |
环保管理 | 28篇 |
综合类 | 67篇 |
基础理论 | 28篇 |
环境理论 | 1篇 |
污染及防治 | 7篇 |
评价与监测 | 6篇 |
社会与环境 | 15篇 |
灾害及防治 | 6篇 |
出版年
2022年 | 4篇 |
2021年 | 12篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 6篇 |
2017年 | 14篇 |
2016年 | 11篇 |
2015年 | 5篇 |
2014年 | 11篇 |
2013年 | 17篇 |
2012年 | 11篇 |
2011年 | 20篇 |
2010年 | 9篇 |
2009年 | 5篇 |
2008年 | 4篇 |
2007年 | 22篇 |
2006年 | 17篇 |
2005年 | 5篇 |
2004年 | 11篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有232条查询结果,搜索用时 15 毫秒
81.
针对我国大气环境管理的发展及实际情况,运用系统分析及目标规划的方法,设计了大气环境标准体系。大气标准体系包括基础标准、大气环境质量标准、排放标准、方法标准、样品标准、燃料使用标准、产品设备大气环保标准、环保行业大气环境保护标准。同时,在大气标准体系中将总量控制思想引入大气污染物排放标准的规定,提出按大气污染物的特征,分3种类型制定大气污染物排放标准等。 相似文献
82.
Introduction: It is widely agreed that highway work zones pose significant threats to road users because driving conditions in work zones are quite different from the normal ones, particularly when traffic volumes approach a highway capacity. Therefore, work zone safety is a critical aspect for state agencies and traffic engineers. Method: In the current study, a total of 10,218 crashes that occurred in highway work zones in the state of Washington for the period between 2007 and 2013 were used. Time of day is disaggregated into four subgroups: (1) Morning from 6:00 to 11:00 a.m. (2) Midday from 12:00 to 5:00 p.m. (3) Night from 6:00 to 11:00 p.m., and (4) Late night from 12:00 to 5:00 a.m. Then, four mixed logit models were estimated to account and correct for heterogeneity in the crash data by considering three injury severity levels: severe injury, minor injury, and no injury. Results: The estimation results reveal that most contributing factors are uniquely significant in a specific time of day period, whereas three factors affect injury severity regardless of time of day such as the indicators of not deployed airbag, one passenger vehicle involved in the crash, and rear-end collision. Further, some factors were found to affect injury severity into two or three time periods, such as female drivers that found to decrease the probability of no injury in morning and night time periods, while increasing severe injury outcome in midday time. Conclusions: The effect of time of day on injury severity of work-zone related crashes should be modeled separately rather than using a holistic model. Practical applications: As a starting point, findings of the current study can be used by transportation officials to reduce fatalities and injuries of work zone crashes by identifying factors that uniquely contribute to each time of day period. 相似文献
83.
系统地介绍了西方国家常用的1种评价环境物品(公共物品)的方法——条件价值法。在大量文献和作者已有研究的基础上,解释了环境物品的特征和价值含义,综述了条件价值法的概念、特点和总体框架内容,分析了该方法中出现的偏差类型,总结了该方法在国际国内的已有应用,提出其应用潜力和应用前景 相似文献
84.
85.
专业化、多样化与产业结构减贫效应的动态异质表现研究 总被引:1,自引:0,他引:1
新一轮扶贫攻坚阶段,贫困地区实现可持续减贫的关键不在于现有经济增长模式下如何提高转移支付的精度和效率,而在于真正改变贫困地区的经济发展理念,从盯住经济总量增长转向用减贫目标统领经济发展。产业结构与贫困减缓的关系影响着贫困地区产业发展的政策制定,但既往研究对何种产业结构更有助于贫困减缓没有形成共识。本文基于产业专业化和多样化视角,分析了专业化、多样化影响贫困减缓的理论机制,并利用2004—2014年中国省级面板数据,对专业化、相关多样化、不相关多样化与FGT贫困指数的关系进行了门限回归和稳健性检验。检验结果确认了产业结构减贫效应的动态异质表现:专业化的减贫效应在产品生命周期的初始和发展阶段趋于增强,并且经济密度更小、距离技术前沿更远的地区,专业化的减贫效果更显著;多样化的减贫绩效低于专业化,且相关多样化的减贫效应高于不相关多样化。细分产业来看,第三产业相关多样化比其他多样化结构更具减贫效果。贫困地区在减贫的产业结构选择上,首要目标是改善专业化程度,其次是在多样化的既定前提下,谋求相关多样化,尤其是第三产业的相关多样化。专业化和相关多样化对不同贫困群体的影响也存在差别,既往产业结构更有利于贫困线附近群体的贫困减缓,而对深度贫困群体的溢出不足。因此,在塑造合宜减贫产业结构,改善低技能劳动力需求的同时,还应辅以改善深度贫困人口劳动力供给的政策,改善其自我发展能力和经济机会,从而增强从益贫产业结构中获益的能力。 相似文献
86.
The life cycle of rice: LCA of alternative agri-food chain management systems in Vercelli (Italy) 总被引:1,自引:0,他引:1
The Vercelli rice district in northern Italy plays a key role in the agri-food industry in a country which accounts for more than 50% of the EU rice production and exports roughly 70%. However, although wealth and jobs are created, the sector is said to be responsible for environmental impacts that are increasingly being perceived as topical. As a complex and comprehensive environmental evaluation is necessary to understand and manage the environmental impact of the agri-food chain, the Life Cycle Assessment (LCA) methodology has been applied to the rice production system: from the paddy field to the supermarket. The LCA has pointed out the magnitude of impact per kg of delivered white milled rice: a CO2eq emission of 2.9 kg, a primary energy consumption of 17.8 MJ and the use of 4.9 m3 of water for irrigation purposes. Improvement scenarios have been analysed considering alternative rice farming and food processing methods, such as organic and upland farming, as well as parboiling. The research has shown that organic and upland farming have the potential to decrease the impact per unit of cultivated area. However, due to the lower grain yields, the environmental benefits per kg of the final products are greatly reduced in the case of upland rice production and almost cancelled for organic rice. LCA has proved to be an effective tool for understanding the eco-profile of Italian rice and should be used for transparent and credible communication between suppliers and their customers. 相似文献
87.
88.
This is a part of the National Report on Volcanology and Chemistry of the Earth's Interior submitted to the XIXth General Assemblage of IUGG, Vancourver, Canada, 1987, by the China Committee for IUGG. It covers the main achievement in research during the period from 1983 to 1986, on mineralization that can be related to volcanism and that occur in volcanic terrains and probably have an indirect genetic relation with volcanism. 相似文献
89.
90.
1987-1990年四年中我国火山矿床研究中取得下列诸方面的成就:(1)玢岩铁矿的形成决定于基性-中基性并具有高碱低硅岩浆的演化,结晶分异时低氧逸度条件;从世界范围看,构造背景与板块俯冲带或缝合带(包括板内古缝合带)直接或间接有关;实验研究解决了几种特殊矿物组合如“膏包辉”组合等的物理化学条件问题。(2)随着中生代火山岩区金矿床的不断发现,对含矿主岩、基底及矿床类型与分布规律有了进一步的认识。(3)斑岩型矿床分布广泛,除Cu,Mo外,涉及Pb-Zn,Ag,Au,W及Sn矿床,并发现与国外层火山中心地区可以对比的上部为脉状矿下部为斑岩型铜矿的实例;(4)火山岩中铀矿床多形成于晚白垩世之后,受火山盆地攻破火山口构造的明显控制;(5)西北与西南海相火山岩区的块状硫化物矿床中,明确了黑矿型钢及多金属矿床和独立的金矿床的存在,在分类上除了Cu-,Cu-Zn-,Zn-Cu-Pb-及Zn-Pb-型之外,Cu-Pb型在国外很少有报导。(6)从成因或构造角度进行了火山岩区矿床成矿规律成分布规律的探索,注意到基底性质与基底构造的关系,对分布规律挺出了岩浆活动中心迁移造成的分布格局上的超覆和地区的剥蚀深度问题;(7)区分出非金属矿床的两个系列:次生石英岩系列及玻璃岩系列。通过这些研究,在火山岩中发现了一些新的远景区和新的矿床。 相似文献