首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   20115篇
  免费   6522篇
  国内免费   871篇
安全科学   2050篇
废物处理   368篇
环保管理   3968篇
综合类   12352篇
基础理论   3128篇
环境理论   48篇
污染及防治   1926篇
评价与监测   2414篇
社会与环境   1002篇
灾害及防治   252篇
  2025年   73篇
  2024年   649篇
  2023年   745篇
  2022年   839篇
  2021年   931篇
  2020年   954篇
  2019年   841篇
  2018年   807篇
  2017年   1057篇
  2016年   1180篇
  2015年   1152篇
  2014年   1094篇
  2013年   1615篇
  2012年   1601篇
  2011年   1547篇
  2010年   1202篇
  2009年   1124篇
  2008年   911篇
  2007年   1240篇
  2006年   1199篇
  2005年   1018篇
  2004年   837篇
  2003年   923篇
  2002年   678篇
  2001年   620篇
  2000年   564篇
  1999年   407篇
  1998年   310篇
  1997年   286篇
  1996年   230篇
  1995年   202篇
  1994年   146篇
  1993年   136篇
  1992年   86篇
  1991年   58篇
  1990年   49篇
  1989年   32篇
  1988年   21篇
  1987年   14篇
  1986年   17篇
  1985年   8篇
  1984年   11篇
  1982年   7篇
  1981年   10篇
  1980年   12篇
  1979年   12篇
  1977年   10篇
  1975年   7篇
  1973年   7篇
  1972年   6篇
排序方式: 共有10000条查询结果,搜索用时 24 毫秒
1.
Abstract:  Broadly conceived and considered in its many usages, sustainability has grave defects as a planning goal, particularly when used by conservationists: it confuses means and ends; it is vague about what is being sustained and who or what is doing the sustaining; it is uninspiring; it is little more than Pinchot-era conservation (and thus ignores the many lessons learned since then); it need not be linked to land, to the land's functioning, or to any ecological science; it need not include a moral component; it is consistent with the view of humans as all-powerful manipulators of the planet; and, in general, it is such a malleable term that its popularity provides only a facade of consensus. When sustainability is defined broadly to include the full range of economic and social aspirations, it poses the particular risk that ecological and biodiversity concerns will be cast aside in favor of more pressing human wants. Given these many defects, the conservation movement should discard the term in favor of a more alluring goal, attentive to nature and its ecological functioning. A sound goal would incorporate and distill the considerable ecological and moral wisdom accumulated since Pinchot's day while giving conservationists the rhetorical tools needed to defend the land against competing pressures. In our view, conservation would be well served by an updated variant of "land health," Aldo Leopold's ecologically grounded goal from the 1940s. Land health as an independent understanding should set the essential terms of how we live and enjoy the earth, providing the framework within which we pursue our many social and economic aims.  相似文献   
2.
中国环境保护产业协会王心芳会长在2006年7月18-19日在北京召开的全国环境保护产业协会工作会议上,就我国环保产业的现状及存在的主要问题、环保产业“十一五”期间面临的形势及“十一五”期间中国环境保护产业协会主要的工作思路做了讲话(本文为讲话摘录)。  相似文献   
3.
通过对移动通信基站天线的电磁辐射分析和探讨,归纳了移动通信基站建设在施工期、营运期环境保护工作的重点与措施,对电磁环境影响评价制度与方法进行了系统的描述,并指出了今后的工作方向。  相似文献   
4.
介绍了一般工业固废填埋场工程的特点和环境监理的现状;结合填埋场项目环境监理工作的实践,分析并总结了填埋场建设项目环境监理要点,即制订切实的监理方案,对工程的关键部位、关键工序做好巡视、旁站监理工作,在实施过程中做好水土保持、生态保护的监理工作。  相似文献   
5.
本文应用生命周期评价,(life cycle assessment,LCA)方法,对镁合金以及塑料这两种笔记本电脑外壳进行了初步评价和比较,结果表明镁舍金能源消耗、温室效应方面为塑料的556.31%、383.30%。但在材料的性能、资源消耗、酸化效应、生态毒理、材料的再生性等方面明显优于塑料。  相似文献   
6.
    
ABSTRACT

Although China’s urban floating population is mainly concentrated in developed cities, from the central and western cities to the eastern developed cities, but the characteristics of the floating population in different cities are significantly different. This paper systematically investigates the spatiotemporal characteristics and influencing factors of the floating population in different levels of cities. The results show that the regional imbalance to further strengthen, accumulation and dispersion trend has become increasingly obvious, liquidity is positively correlated and city level scale, and urban agglomeration and the core city is still polarization center of floating population. Flow range is closely related to urban hierarchy: the higher the intra-urban grade, the more tend to inter-provincial flow; the lower the city grade, the more tend to intra-urban mobility. Short-term (1-2 years) and long-term (more than 7 years) flow-time coexist. The short-term liquidity increases with the city grade, and the long-term liquidity decreases with the city level. Farmers are still the main body of the floating population. Younger age, lower education level, low-skilled, high gender ratio employees are the most basic demographic characteristics of the floating population, although there are differences between different cities. The main reason for affecting the floating population is seeking jobs and doing business.  相似文献   
7.
Freeze-induced acceleration of I-oxidation and the consequent iodination of dissolved or-ganic matter(DOM)contribute to the formation of organoiodine compounds(OICs)in cold regions.The formed OICs may be a potentially important source of risk and are very closely with the environment and human health.Herein,we investigated the acceleration effects of the freeze process on I-oxidation and the formation of OICs.In comparison to reac-tive iodine species(RIS)formed in aqueous solutions,I-oxidation and RIS formation were greatly enhanced in frozen solution and were affected by pH,and the content of I-and O2.Freeze-thaw process further promoted I-oxidation and the concentration of RIS reached 45.7 μmol/L after 6 freeze-thaw cycles.The consequent products of DOM iodination were greatly promoted in terms of both concentration and number.The total content of OICs ranged from 0.02 to 2.83 μmol/L under various conditions.About 183-1197 OICs were de-tected by Fourier transform ion cyclotron resonance mass spectrometry,and more than 96.2% contained one or two iodine atoms.Most OICs had aromatic structures and were formed via substitution and addition reactions.Our findings reveal an important forma-tion pathway for OICs and shed light on the biogeochemical cycling of iodine in the natural aquatic environment.  相似文献   
8.
A method for quality screening is suggested to detect volatile impurities in inorganic coagulants that are used for drinking water treatment. Static headspace gas chromatography with mass spectrometry detection (HS–GCMS) is sensitive and selective to detect volatiles in low concentrations. This study has discovered that volatile organic impurities are detectable in ferric and aluminium-based coagulants which are used for drinking water treatment. For ferric chloride, 2-propanol was detected at a level of 17–24 μg ml−1, acetone at 0.7–1.7 μg ml−1, 1,1,1-trichloroacetone at 0.02–0.04 μg ml−1, trichloromethane at 0.01–0.02 μg ml−1 and toluene at 0.01–0.12 μg ml−1. For ferric chloride sulfate, acetone was detected at a level of 0.12 μg ml−1, 1,1,1-trichloroacetone at 0.06–0.08 μg ml−1, trichloromethane at 0.13–0.23 μg ml−1, bromodichloromethane at 0.04–0.06 μg ml−1 and dibromochloromethane at 0.04–0.05 μg ml−1. For aluminium hydroxide chloride, only trichloromethane was detectable, but below the method detection limits (MDL). Although the concentrations of these impurities in commercial coagulants are low, this observation is important and should have impact on water industries for them to pay attention to the chemicals they are using for drinking water production.  相似文献   
9.
张华 《环境技术》2009,27(6):18-19,22
六自由度气锤振动与电磁斜面振动是两种模拟产品三轴振动的振动技术。由于两种振动技术的机理不同,其对样品的振动影响也会有区别。本文研究讨论两种不同振动技术的不同特点,以及对不同产品的振动效果别,我们可以根据样品特点和测试需求,选择更合适的震动技术。  相似文献   
10.
分析了福建省环保产业的发展状况及存在的主要问题,对福建省环保产业的发展进行了展望,提出了加快福建省环保产业市场发展的对策与措施。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号