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   424篇
  免费   13篇
  国内免费   26篇
安全科学   35篇
废物处理   2篇
环保管理   145篇
综合类   151篇
基础理论   44篇
污染及防治   25篇
评价与监测   23篇
社会与环境   22篇
灾害及防治   16篇
  2023年   5篇
  2022年   3篇
  2021年   16篇
  2020年   20篇
  2019年   7篇
  2018年   12篇
  2017年   13篇
  2016年   16篇
  2015年   17篇
  2014年   17篇
  2013年   28篇
  2012年   18篇
  2011年   19篇
  2010年   23篇
  2009年   19篇
  2008年   22篇
  2007年   16篇
  2006年   16篇
  2005年   15篇
  2004年   9篇
  2003年   15篇
  2002年   12篇
  2001年   14篇
  2000年   16篇
  1999年   12篇
  1998年   10篇
  1997年   9篇
  1996年   4篇
  1995年   7篇
  1994年   4篇
  1993年   3篇
  1992年   3篇
  1990年   2篇
  1989年   4篇
  1988年   4篇
  1986年   5篇
  1985年   5篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1981年   2篇
  1980年   3篇
  1979年   4篇
  1978年   1篇
  1977年   1篇
  1976年   1篇
  1975年   1篇
  1974年   2篇
  1973年   1篇
  1971年   1篇
排序方式: 共有463条查询结果,搜索用时 156 毫秒
281.
A new iron-fly ash packing was studied for reductive transformation of p-nitrotoluene. The packing was made of iron, fly ash and kaolin with the mass ratio of 36:7:2. A reactor was designed to investigate the long-term performance of the packing. The results showed that the reduction of p-nitrotoluene increased with decreasing pH, because the reduction potential of reaction increased with the concentration of H+. The pH was one of the key factors impacting the reductive transformation of p-nitrotoluene. Comparing iron-activated carbon packing with the new iron-fly ash packing, the reduction efficiencies were respectively 76.61% and 75.36% after 20 days. The reduction efficiency for both was around 50% at 40 days. It was evident that these two kinds of packing had no significant difference in their capability for p-nitrotoluene reductive transformation. Compared with iron-activated carbon, the new iron-fly ash packing had obvious advantages in terms of manufacturing costs and environmental pollution degradation. This study showed that the new iron-fly ash packing had good performance in reductive transformation of nitrotoluene compounds.  相似文献   
282.
Collaboration is an increasingly important approach to dealing with complex environmental challenges. Participation of diverse actors in collaborative processes necessitates attention to the use of different forms of knowledge. We use a multi-case study of governance for water in New Brunswick, Canada, to explore knowledge-related concerns that are prominent in collaborative processes. As is common in other contexts, local or lay (experiential) forms of knowledge appeared to play complementary but ultimately subordinate roles to expert technical and scientific knowledge in the cases. Importantly, we found that the distinction between ‘expert’ and ‘local’ knowledge was not at all clear for the many participants. This study reinforces the importance of designing reflexive and flexible processes for encouraging the active engagement and use of knowledge in collaboration.  相似文献   
283.
The cause of poor welfare in broilers is multifactorial, but genotype is a major contributor. Modern broilers have been bred for rapid growth, and this leads to increases in lameness and ascites as the legs and hearts of the heavier birds find it difficult to cope with the extra demands placed on them. Visible lameness indicative of pain is more common in New Zealand than in Europe. The government, however, insists that New Zealand welfare standards are higher than Europe. The government also appears to have a strong antipathy to those demanding better welfare for broilers. Reasons for this antipathy and disparities between government statements and research results are discussed. Government publications reveal that animal welfare is seen as a question of image for market access and that there is little concern with animal welfare as an ethical imperative for its own sake. The Animal Welfare Act in theory makes it an offence to ill treat an animal, but in practice allows exemptions for industrial agriculture. The interests of animals may be better protected by an independent animal welfare advisory service.  相似文献   
284.
Primary steelmaking involves CO2-intensive processes, but the expansion of secondary steel production is limited by the global availability of steel scrap. The present work examines global scrap consumption in the past (1870–2012) and future scrap availability (2013–2050) based on the historical trend. The results reveal that (i) historically, the consumption of old scrap has been insufficient compared with the amounts of discarded steel, and (ii) based on historical scrap consumption, the future availability of scrap will not be sufficient to satisfy the two assumed cases of steel demand. Primary steelmaking is expected to remain the dominant process, at least up until 2050. Under the reference-demand case of 2.19 billion tons in crude steel production by 2050, the total production of pig iron and direct reduced iron could reach 1.35 billion tons. Consumption of old scrap could reach 0.76 billion tons. Because the availability of scrap will be limited in the context of the global total, it is important to research and develop innovative low-carbon technologies for primary steelmaking and to explore their economic viability if we are to aim for achieving large reductions in CO2 emissions from the iron and steel industry.  相似文献   
285.
Abstract:  For many regions worldwide, multiple and often contrasting biogeographic classifications exist that are derived from a variety of taxa and techniques. This presents a challenge for managers who must choose appropriate large-scale spatial frameworks for systematic conservation planning. We demonstrate how systematically collected community data can be used to evaluate existing biogeographic classifications, identify the most appropriate metric for biogeographic patterns seen in other taxonomic groups, and develop an independent biogeographic classification scheme for systematic conservation planning. We evaluated 6 existing biogeographic classifications for New Zealand's nearshore marine environment with community-similarity metrics derived from abundance and presence–absence data for macroalgae (107 species) and mobile macroinvertebrates (44 species). The concordance between community metrics and the previous classifications was high, as indicated by a high multivariate classification success (CS) (74.3–98.3%). Subsequently, we carried out an independent classification analysis on each community metric to identify biogeographic units within a hierarchical spatial framework. The classification derived from macroalgal presence–absence data achieved the highest CS and could be used as a mesoscale classification scheme in which 11 regional groupings (i.e., bioregions) (CS = 73.8–84.8%) are nested within northern and southern biogeographic provinces (CS = 90.3–98.7%). These techniques can be used in systematic conservation planning to inform the design of representative and comprehensive networks of marine protected areas through evaluation of the current coverage of marine reserves in each bioregion. Currently, 0.22% of the territorial sea around mainland New Zealand is protected in no-take marine protected areas in which 0–1.5% of each bioregion represented.  相似文献   
286.
Davies‐Colley, Robert J., David G. Smith, Robert C. Ward, Graham G. Bryers, Graham B. McBride, John M. Quinn, and Mike R. Scarsbrook, 2011. Twenty Years of New Zealand’s National Rivers Water Quality Network: Benefits of Careful Design and Consistent Operation. Journal of the American Water Resources Association (JAWRA) 47(4):750‐771. DOI: 10.1111/j.1752‐1688.2011.00554.x Abstract: This paper reviews New Zealand’s National Rivers Water Quality Network (NRWQN), which is now in its third decade of monitoring. The NRWQN is noteworthy for being operationally stable throughout its history, and the resulting consistency is increasingly valuable for detecting water quality trends and for “anchoring” temporary special purpose monitoring campaigns. The NRWQN was carefully designed following considerable effort to learn from monitoring experiences elsewhere. Monthly visits are made to 77 sites (all near hydrometric stations) on 35 river systems that cumulatively drain about one half of the national landscape. “Core” (routinely measured) variables are: conductivity, pH, temperature, dissolved oxygen, visual clarity, turbidity, colored dissolved organic matter, fecal indicator bacteria, and different forms of nitrogen and phosphorus (italics indicate field measurements). Associated benthic biological monitoring comprises monthly visual assessment of periphyton and annual sampling for macro‐invertebrates. We overview the conception, design, initiation, and operational history of the NRWQN, and highlight the diverse applications of its datasets including numerous scientific applications, national‐scale modeling of material fluxes, and state‐of‐environment reporting and practical water management at both regional and national scale. The qualified success of the NRWQN can probably be attributed to careful (and parsimonious) design and consistent operation.  相似文献   
287.
The development corporations of the new towns in Scotland have had to overcome many obstacles in the execution of their task. This history is outlined for each new town in the appendices. The statutory and political context of the imminent winding‐up of the development corporations of the remaining five new towns is explained, and the preliminary steps by the Scottish Office in recent years are outlined. The Government's strategy for transfer of responsibilities from the development corporations to other bodies is summarised and discussed under four broad headings. Finally, the prospects for more new settlements in Scotland are assessed.  相似文献   
288.
Canoes forging through cold waters, mountains rising from the sea, a heart beating under a mountain lake, an albatross sailing toward the Antarctic: these were the story-images of Coastal Mappings, a large-scale community project set in and around Dunedin, New Zealand. In the Coastal Mappings performance project, people in the last months of their lives joined cancer survivors, family members and other interested people in explorations of Pakeha myths (by European-settler descendents) and Maori myths (by descendents of the crews of the first canoes, first inhabitants of New Zealand). Together, we created personal landscapes through movement, storytelling, photography and video. In this essay, I discuss some of the opportunities, challenges and experiences of leading a community dance project in an intercultural social environment, and with people whose relationship to their environment is different from mine.  相似文献   
289.
ABSTRACT

The evolution of Chinese environmental policy and politics can be better understood in the broader context of institutional changes that have taken place since the late 1970s. In this study, an analytical framework was established to analyze how overall institutional changes were reflected in the roles of relationships between governmental and non-governmental actors engaged in environmental governance. Institutional changes were observed at three levels: informal institutions (cultural traditions, and political ideology); formal institutions (the polity, political system, property rights, and judiciary); and governing mechanisms (structures, regulatory approaches, and incentives). This analysis of interactions between institutional changes and the changing environmental process explained not only the drives and constraints behind China’s environmental policy evolution so far but also shed light on future challenges and opportunities.  相似文献   
290.
为科学评估雄安新区表层土壤氟(F)地球化学分布特征及人体健康风险,利用GIS空间分析、相关分析等分析土壤F贫化富集特征及影响因素,开展土壤F健康风险评估,基于蒙特卡罗随机模拟,研究健康风险评价结果的不确定性.结果表明,新区表层土壤ω(F)均值为641 mg·kg-1,是全国A层土壤背景值的1.34倍,F过剩和高等级样点占比超过85%,F含量整体相对偏高.灌溉水样ρ(F-)均值为0.85 mg·L-1, F-含量空间分布特征受浅层地下水水化学类型和流向的影响.土壤F垂向空间变化不显著,其垂向变化主要受土壤有机碳、质地等土壤理化性质的垂向分布影响.表层土壤F的贫化富集主要受地质背景成因控制,人为因素(农业灌溉水、施肥和大气干湿沉降)等外源输入影响其异常的空间分布.区内土壤F含量与地貌环境“标志性”指标Al2O3、 Fe2O3、 MgO和K2O含量,土壤有机碳(Corg.)、阳离子交换量(CEC)...  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