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   446篇
  免费   11篇
  国内免费   2篇
安全科学   26篇
废物处理   20篇
环保管理   76篇
综合类   67篇
基础理论   100篇
环境理论   1篇
污染及防治   102篇
评价与监测   36篇
社会与环境   29篇
灾害及防治   2篇
  2023年   5篇
  2022年   13篇
  2021年   14篇
  2020年   7篇
  2019年   5篇
  2018年   16篇
  2017年   20篇
  2016年   27篇
  2015年   15篇
  2014年   19篇
  2013年   47篇
  2012年   17篇
  2011年   28篇
  2010年   22篇
  2009年   13篇
  2008年   21篇
  2007年   17篇
  2006年   22篇
  2005年   15篇
  2004年   14篇
  2003年   17篇
  2002年   14篇
  2001年   4篇
  2000年   5篇
  1999年   7篇
  1998年   3篇
  1997年   5篇
  1996年   3篇
  1995年   7篇
  1994年   4篇
  1993年   4篇
  1992年   5篇
  1991年   3篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1985年   4篇
  1984年   4篇
  1983年   2篇
  1982年   3篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1969年   1篇
排序方式: 共有459条查询结果,搜索用时 409 毫秒
401.
Defining Chlorophyll-a Reference Conditions in European Lakes   总被引:2,自引:0,他引:2  
The concept of “reference conditions” describes the benchmark against which current conditions are compared when assessing the status of water bodies. In this paper we focus on the establishment of reference conditions for European lakes according to a phytoplankton biomass indicator—the concentration of chlorophyll-a. A mostly spatial approach (selection of existing lakes with no or minor human impact) was used to set the reference conditions for chlorophyll-a values, supplemented by historical data, paleolimnological investigations and modelling. The work resulted in definition of reference conditions and the boundary between “high” and “good” status for 15 main lake types and five ecoregions of Europe: Alpine, Atlantic, Central/Baltic, Mediterranean, and Northern. Additionally, empirical models were developed for estimating site-specific reference chlorophyll-a concentrations from a set of potential predictor variables. The results were recently formulated into the EU legislation, marking the first attempt in international water policy to move from chemical quality standards to ecological quality targets.  相似文献   
402.
The biodegradation of blends of poly(caprolactone) (PCL) and poly(vinyl chloride) (PVC) has been studied. Blends of composition PCL/PVC 1:1 and 1:2 w/w were tested. The 1:1 blend contained crystals in the as-cast state and became more crystalline on exposure to different bio-active agents. The 1:2 blend was amorphous in the as-cast state but developed a significant crystal component after 4 months exposure to the bio-agents. Three bio-active agents were used and all were found to produce qualitatively similar behaviour but their activity was somewhat different. For both the 1:1 blend and the 1:2 blend the ranking of the three bio-active agents tested, in increasing order, was Curvularia sp.; Trogia buccinalis; Phanerochaete chrysosporium.  相似文献   
403.
404.
Chemical monitoring of water quality on a total of 16 rivers in the Azores archipelago (Portugal), since 2003, made it possible to identify the major pressures and spatial geochemical variations along main course of the rivers. River water pollution is to a large extent associated to point sources, namely domestic wastewater discharges, especially in urban areas, and diffuse sources, associated with pasture land, and explain the high values on BOD(5) and nutrients (P and N). Heavy metals and metalloids, as well as hydrocarbons and pesticides, are generally under the detection limits of the analytical methods. Generally, river water reflects pollution loads according to a simple model, derived from land use in the watershed: in the upper part conditions are pristine, in the intermediate portion of the basin pasture land dominates and near the coast urban discharges are increasingly important. Results stress the role that an approach based on the watershed scale, coupled with land use management measures, are crucial to water management procedures and a successful WFD implementation in small river basin districts like the Azores. The paper also shows the need for full compliance regarding EU directives on urban wastewater and nitrate pollution due to agriculture.  相似文献   
405.
The main objective of this work was to quantify and characterize the major indoor air contaminants present in different stages of a municipal WWTP, including microorganisms (bacteria and fungi), carbon dioxide, carbon monoxide, hydrogen sulfide ammonia, formaldehyde, and volatile organic compounds (VOCs). In general, the total bacteria concentration was found to vary from 60 to >52,560 colony-forming units (CFU)/m3, and the total fungi concentration ranged from 369 to 14,068 CFU/m3. Generally, Gram-positive bacteria were observed in higher number than Gram-negative bacteria. CO2 concentration ranged from 251 to 9,710 ppm, and CO concentration was either not detected or presented a level of 1 ppm. H2S concentration ranged from 0.1 to 6.0 ppm. NH3 concentration was <2 ppm in most samples. Formaldehyde was <0.01 ppm at all sampling sites. The total VOC concentration ranged from 36 to 1,724 μg/m3. Among the VOCs, toluene presented the highest concentration. Results point to indoor/outdoor ratios higher than one. In general, the highest levels of airborne contaminants were detected at the primary treatment (SEDIPAC 3D), secondary sedimentation, and sludge dehydration. At most sampling sites, the concentrations of airborne contaminants were below the occupational exposure limits (OELs) for all the campaigns. However, a few contaminants were above OELs in some sampling sites.  相似文献   
406.
Environment, Development and Sustainability - The activated biochar is a carbonaceous material obtained from thermal degradation of biomass with high adsorption potential. On the other hand, the...  相似文献   
407.
Collaborative planning theory and co-management paradigms promise conflict prevention and the incorporation of indigenous knowledge into plans. Critics argue that without devolved power to culturally legitimate institutions, indigenous perspectives are marginalized. Co-management practice in North America is largely limited to treaty-protected fish and wildlife because federal agencies cannot devolve land management authority. This paper explores why the Pueblo de Cochiti, a federally recognized American Indian Tribe, and the U.S. Bureau of Land Management sustained an rare joint management agreement for the Kasha-Katuwe Tent Rocks National Monument in New Mexico despite a history of conflict over federal control of customary tribal lands that discouraged the Pueblo from working with federal agencies. Based on the participant interviews and documents, the case suggests that clear agreements, management attitudes, and the direct representation of indigenous forms of government helped achieve presumed co-management benefits. However, parties enter these agreements strategically. We should study, not assume, participant goals in collaborative processes and co-management institutions and pay special attention to the opportunities and constraints of federal laws and institutional culture for collaborative resource management with tribal and local communities.  相似文献   
408.
Concentrations of polybrominated diphenyl ethers (PBDEs) in Forster’s tern (Sterna forsteri) eggs from San Francisco Bay have been reported to range up to 63 μg g−1 lipid weight. This value exceeds the lowest-observed-adverse-effect level (1.8 μg g−1 egg wet weight; ∼32 μg−1 lipid weight) reported in an embryotoxicity study with American kestrels (Falco sparverius). As a surrogate for Forster’s terns, common tern (Sterna hirundo) eggs were treated by air cell injection with corn oil vehicle (control) or a commercial penta-BDE formulation (DE-71) at nominal concentrations of 0.2, 2, and 20 μg g−1 egg. As a positive control, kestrel eggs received vehicle or 20 μg DE-71 g−1 egg. In terns, there were no effects of DE-71 on embryonic survival, and pipping or hatching success; however, treated eggs hatched later (0.44 d) than controls. Organ weights, organ-to-body weight ratios, and bone lengths did not differ, and histopathological observations were unremarkable. Several measures of hepatic oxidative stress in hatchling terns were not affected by DE-71, although there was some evidence of oxidative DNA damage (8-hydroxy-deoxyguanosine; 8-OH-dG). Although DE-71 did not impair pipping and hatching of kestrels, it did result in a delay in hatch, shorter humerus length, and reduced total thyroid weight. Concentrations of oxidized glutathione, reduced glutathione, thiobarbituric acid reactive substances, and 8-OH-dG in liver were greater in DE-71-treated kestrels compared to controls. Our findings suggest common tern embryos, and perhaps other tern species, are less sensitive to PBDEs than kestrel embryos.  相似文献   
409.
The use of forest land for ecotourism has been well accepted due to its ability to provide income to local people and to conserve the forest. Preparing the forest with infrastructure to attract and educate visitors has been reported of importance. This study applied Q methodology in a small rural community of the State of Puebla, Mexico, to reveal forest owners’ perceptions to build infrastructure in their forest as part of their ecotourism project. It also discloses forest owners’ underlying motives to use their forest for ecotourism. Ecotourism is perceived as a complementary activity to farming that would allow women to be involved in community development. Low impact infrastructure is desired due to forest owners’ perception to preserve the forest for the overall community well-being.  相似文献   
410.
A key characteristic of global organic agriculture governance through standards is the coexistence of regulatory fragmentation and regional integration. To reduce barriers to organic trade, especially for market participants from developing countries, international and transnational entrepreneurs increasingly promote the setting of organic agriculture standards (OAS) in different world regions, for example, in East Africa, the Pacific, or Asia. Although scholars from different disciplines have done a lot of research on the role of standards in global governance, we still know little about why and how regional standard-setting processes evolve. Applying findings from regime analysis, entrepreneurship, and political authority, the article introduces the concept of authority pooling. It argues that legal, moral, and technical authority sources interact in a blurred functional division of labour between the public and the private sector in standard-setting. The article presents results from a within-case study of the development of the East African Organic Products Standard using the process-tracing method. It detects the underlying causal mechanism by which international and transnational entrepreneurs pooled different authority sources and, thus, significantly influenced political actors in East Africa to set the first regional OAS in the developing world.  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