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   810篇
  免费   6篇
  国内免费   4篇
安全科学   11篇
废物处理   31篇
环保管理   60篇
综合类   183篇
基础理论   167篇
污染及防治   254篇
评价与监测   62篇
社会与环境   47篇
灾害及防治   5篇
  2023年   10篇
  2022年   32篇
  2021年   19篇
  2020年   9篇
  2019年   14篇
  2018年   29篇
  2017年   32篇
  2016年   49篇
  2015年   18篇
  2014年   49篇
  2013年   59篇
  2012年   37篇
  2011年   67篇
  2010年   34篇
  2009年   31篇
  2008年   44篇
  2007年   43篇
  2006年   39篇
  2005年   28篇
  2004年   31篇
  2003年   18篇
  2002年   19篇
  2001年   12篇
  2000年   5篇
  1999年   5篇
  1998年   3篇
  1997年   4篇
  1996年   3篇
  1995年   3篇
  1994年   4篇
  1993年   3篇
  1992年   3篇
  1991年   2篇
  1990年   3篇
  1989年   3篇
  1988年   3篇
  1983年   2篇
  1979年   2篇
  1966年   2篇
  1965年   3篇
  1964年   5篇
  1963年   4篇
  1962年   2篇
  1961年   4篇
  1960年   5篇
  1959年   2篇
  1958年   2篇
  1957年   5篇
  1942年   2篇
  1941年   2篇
排序方式: 共有820条查询结果,搜索用时 31 毫秒
291.
292.
293.
While new environmental policies and procedures often are developed incrementally, they can also result from crises or other significant events. In situations where policies and procedures are introduced in response to a crisis, questions about the strengths and weaknesses of existing mechanisms, and the extent to which they can be used to address concerns, may be ignored. This paper explores the complexities of introducing new policies and processes where planning systems and procedures already exist. Drinking water source protection policies that are being developed in response to the tragic events in Walkerton, Ontario, Canada serve as the context for the inquiry. Three case study watersheds were selected to reflect the diversity of municipal jurisdictions and water supply systems in Ontario. A content analysis was undertaken on regulatory and non-regulatory policy documents to determine the extent to which they addressed elements of the multi-barrier approach for drinking water safety. Findings from the research reveal considerable evidence of the multi-barrier approach in the policy and guiding documents analyzed. Policy development in response to a crisis can advance progress on the issue of drinking water safety and coincide with emerging governance strategies. Policy effectiveness may be enhanced by considering existing policies as well as contextual and jurisdictional differences.  相似文献   
294.
This paper empirically shows how the uncertainty associated to the absence of a mitigation regime which follows the United Nations Framework Convention on Climate Change Kyoto Protocol (UN FCCC Kyoto Protocol) is affecting investments in abatement activities in the EU electricity sector and, thus, future emissions levels. Based on a survey of EU electric utilities, it identifies the most likely post-Kyoto scenarios considered by them and how they are coping with such uncertainty in their investment decisions. It is found that firms react differently to such uncertainty and adopt different strategies to cope with it, diversifying their emissions control activities. Although most companies foresee post-Kyoto compliance regimes with emissions trading systems, they differ in their perceptions of the form that a post-Kyoto regime could take and are, thus, positioning differently to face such regime. The particular features of each company and the country where they operate affect their perception of the uncertainties, their position regarding a possible post-Kyoto regime and their inclination to carry out mitigation activities. Complying with Kyoto (and, eventually, post-Kyoto) targets significantly influences the investment decisions of European electricity companies. Uncertainty about a post-Kyoto regime may already be affecting investments in mitigation activities in the electricity sector. Therefore, significant progress has to be made in the definition of a post-Kyoto regime. It is urgent to define and agree internationally the emissions reduction objectives and the mitigation instruments that will be accepted for compliance, ensuring continuity of the international emissions trading system foreseen in the Kyoto Protocol.
Pablo del RíoEmail:
  相似文献   
295.
Myrmecophytes offer plant-ants a nesting place in exchange for protection from their enemies, particularly defoliators. These obligate ant–plant mutualisms are common model systems for studying factors that allow horizontally transmitted mutualisms to persist since parasites of ant–myrmecophyte mutualisms exploit the rewards provided by host plants whilst providing no protection in return. In pioneer formations in French Guiana, Azteca alfari and Azteca ovaticeps are known to be mutualists of myrmecophytic Cecropia (Cecropia ants). Here, we show that Azteca andreae, whose colonies build carton nests on myrmecophytic Cecropia, is not a parasite of AztecaCecropia mutualisms nor is it a temporary social parasite of A. alfari; it is, however, a temporary social parasite of A. ovaticeps. Contrarily to the two mutualistic Azteca species that are only occasional predators feeding mostly on hemipteran honeydew and food bodies provided by the host trees, A. andreae workers, which also attend hemipterans, do not exploit the food bodies. Rather, they employ an effective hunting technique where the leaf margins are fringed with ambushing workers, waiting for insects to alight. As a result, the host trees’ fitness is not affected as A. andreae colonies protect their foliage better than do mutualistic Azteca species resulting in greater fruit production. Yet, contrarily to mutualistic Azteca, when host tree development does not keep pace with colony growth, A. andreae workers forage on surrounding plants; the colonies can even move to a non-Cecropia tree.  相似文献   
296.
The Great American Biotic Interchange has been the predominant paradigm for explaining biotic diversification in the Nearctic/Neotropical overlap or Mexican Transition Zone, which is commonly explained by the collision of the North and South American continental plates, which began in the Oligocene and fused both landmasses. In the most far-reaching cladistic biogeographical analysis of the area to date, evidence has been found supporting the existence of a remnant Caribbean region extending from eastern Mexico to southeastern USA, a hypothesis that challenges current views of the Great American Biotic Interchange and the Mexican Transition Zone. We show herein that an older terrane, which has drifted to the present day positions of Yucatan and Cuba, may be biogeographically linked to an early ‘Gondwanan’ biota of the Paleocene (ca. 60 Ma). The evidence indicates an east–west biotic divide in Mexico, existing before the collision and formation of Central America. The south–north division of the country, previously recognized by several authors as associated with the Great American Biotic Interchange and the Mexican Transition Zone, is of a younger age. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
297.
BACKGROUND: Mold growth is believed to be one causative factor underlying the association between dampness in buildings and increased respiratory morbidity. Measurements of beta(1-->3)-glucans and fungal extracellular polysaccharides (EPS) are used as markers of mold exposure in field studies. Little is known about their levels and determinants in homes. OBJECTIVE: To study levels and determinants of beta(1-->3)-glucan and EPS levels in mattress and living room floor dust in three European countries. METHODS: Mattress and living room floor dust was collected in the homes of 1065 German, Dutch, and Swedish (pre-)school children. All samples were analyzed for beta(1-->3)-glucans and EPS in one central laboratory. Determinants were assessed by questionnaire. RESULTS: Amounts of dust, EPS and beta(1-->3)-glucan levels differed between countries. Amounts of dust, beta(1-->3)-glucan and EPS levels for mattresses were only weakly correlated with those for living room floors. Floor dust beta(1-->3)-glucan loads, EPS loads and EPS concentrations were strongly correlated with the amount of dust sampled, which is largely determined by the type of floor that was sampled (carpeted floors had 5-20 higher amounts of dust). None of the other determinants was consistently and statistically significantly associated with amounts of dust, beta(1-->3)-glucan and EPS concentrations on floors and mattresses. CONCLUSION: Mattress dust and floor dust are two different measures of exposure to the investigated mold components. Living room floor beta(1-->3)-glucan and EPS loads and EPS concentrations are largely determined by the type of floor sampled. Differences between countries can only partly be explained by the determinants studied.  相似文献   
298.
This paper presents an environmental system study of the production of propionic acid in a biorefinery system based on agricultural by-products. Here, propionic acid is produced by fermentation of glycerol, a by-product from biodiesel production, as carbon source and potato juice, a by-product from starch production, as nitrogen source. Biomass-based propionic acid leads to a greenhouse gas reduction of 60% compared to propionic acid from fossil sources. However, the primary energy input is about twice as high for the biomass-based propionic acid. The choice of input energy and the efficiency of the process, as well as the technology applied, have high impacts on the environmental performance of the biorefinery concept. There is a potential for increased integration both on the input of substrates and the output of end products of the biorefinery system, which will further improve its environmental performance.  相似文献   
299.
Environmental Science and Pollution Research - In this study, the performance of the Sequential Gaussian Simulation (SGS) approach was studied with the aim of accurately determining local health...  相似文献   
300.
Environmental Science and Pollution Research - Toxic heavy metals released into the environment through various industrial processes have potential adverse effects on the environment and human...  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