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   417篇
  免费   9篇
  国内免费   7篇
安全科学   23篇
废物处理   11篇
环保管理   60篇
综合类   63篇
基础理论   115篇
环境理论   1篇
污染及防治   104篇
评价与监测   43篇
社会与环境   10篇
灾害及防治   3篇
  2023年   4篇
  2022年   15篇
  2021年   13篇
  2020年   14篇
  2019年   14篇
  2018年   14篇
  2017年   18篇
  2016年   17篇
  2015年   12篇
  2014年   22篇
  2013年   39篇
  2012年   19篇
  2011年   29篇
  2010年   20篇
  2009年   22篇
  2008年   29篇
  2007年   20篇
  2006年   16篇
  2005年   16篇
  2004年   14篇
  2003年   9篇
  2002年   9篇
  2001年   9篇
  2000年   1篇
  1999年   3篇
  1998年   2篇
  1997年   3篇
  1995年   2篇
  1994年   4篇
  1993年   1篇
  1992年   1篇
  1991年   2篇
  1990年   1篇
  1989年   3篇
  1986年   2篇
  1984年   1篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
  1973年   1篇
  1968年   1篇
  1961年   2篇
  1960年   1篇
  1954年   1篇
  1937年   1篇
  1936年   1篇
排序方式: 共有433条查询结果,搜索用时 109 毫秒
101.
The effects of chronic exposure to increasing levels of human‐induced underwater noise on marine animal populations reliant on sound for communication are poorly understood. We sought to further develop methods of quantifying the effects of communication masking associated with human‐induced sound on contact‐calling North Atlantic right whales (Eubalaena glacialis) in an ecologically relevant area (~10,000 km2) and time period (peak feeding time). We used an array of temporary, bottom‐mounted, autonomous acoustic recorders in the Stellwagen Bank National Marine Sanctuary to monitor ambient noise levels, measure levels of sound associated with vessels, and detect and locate calling whales. We related wind speed, as recorded by regional oceanographic buoys, to ambient noise levels. We used vessel‐tracking data from the Automatic Identification System to quantify acoustic signatures of large commercial vessels. On the basis of these integrated sound fields, median signal excess (the difference between the signal‐to‐noise ratio and the assumed recognition differential) for contact‐calling right whales was negative (?1 dB) under current ambient noise levels and was further reduced (?2 dB) by the addition of noise from ships. Compared with potential communication space available under historically lower noise conditions, calling right whales may have lost, on average, 63–67% of their communication space. One or more of the 89 calling whales in the study area was exposed to noise levels ≥120 dB re 1 μPa by ships for 20% of the month, and a maximum of 11 whales were exposed to noise at or above this level during a single 10‐min period. These results highlight the limitations of exposure‐threshold (i.e., dose‐response) metrics for assessing chronic anthropogenic noise effects on communication opportunities. Our methods can be used to integrate chronic and wide‐ranging noise effects in emerging ocean‐planning forums that seek to improve management of cumulative effects of noise on marine species and their habitats. Cuantificación de la Pérdida de Espacio de Comunicación Acústica para Ballenas Francas Dentro y Alrededor de un Santuario Marino Nacional en E. U. A.  相似文献   
102.
Evidence of diseases on vertebrate fossil bones can provide detailed information on many aspects of extinct animals. This study focused on pathological craniodental remains (left maxilla and dentary) referred to the canid Cuon alpinus unearthed from a Late Pleistocene karst filling deposit at San Sidero (Apulia, southern Italy). These fossils show clear evidence of a chronic periodontitis that caused the animal’s death. Clinical diagnosis of the disease and the timing of its development have been defined on the basis of a veterinary odontostomatology approach, in addition to radiographic and tomographic techniques. From the initiation of the infection until death, a time span of at least 6 months occurred, and three main steps have been defined: (1) the bacterial infections of the buccal cavity turning into severe periodontitis, (2) the fracture of the lower carnassial and (3) the loss of teeth due to the worsening infection that deformed and/or eroded maxillary and mandibular bones and enlarged alveoli. The analysis of the palaeopathology also provides information about the biomechanics of the bite, on the feeding behaviour and on the relationships of injured members in a pack of Late Pleistocene canids.  相似文献   
103.
Integrated coastal zone management (ICZM) has evolved as a key mechanism for the delivery of sustainable development objectives within coastal regions. Yet, despite significant advancements in ICZM application over recent years, one of the most noticeable weaknesses of ICZM performance has been a failure to adequately account for the existence of socio‐economic concerns. This information deficiency is particularly apparent in Scotland. Despite significant progress in the promotion of ICZM, Scottish experiences have been characterized by a focus upon sectoral policy co‐ordination and environmental dimensions of sustainability. This paper provides an evaluation of both socio‐economic conditions and processes which impact upon coastal communities in Scotland and considers how such issues can be accounted for within future coastal management debates.  相似文献   
104.
Minimisation is the top priority of the waste management hierarchy, which is one of the guiding principals for national solid waste management planning throughout the developed world. As such it should be encouraged as a means for reducing wastes which require treatment and disposal, whether they be household, commercial or industrial in source. This paper suggests that minimisation is not being given the necessary policy frameworks or legislation within which to develop in the UK, and questions whether minimisation is being afforded the respect and attention, from all levels, that is due the most preferable waste option according to the hierarchy. This theme is investigated by surveying the county councils of England as a representative sample of waste disposal authorities in England, and former waste regulation authorities. They are responsible for guiding local and district waste policy and are the regional waste planners in the UK. If they are not seriously taking on board the message of minimisation, then there is little chance that it will succeed without further legislative developments. Some 59% of English counties have a minimisation policy, whilst only 47% have participated in and supported a minimisation programme or trial within their region. The majority of these developments have occurred within the last three years, and 78% of counties who have participated in a programme have found it a successful venture. By 1999 79% of English counties will have been actively involved in a minimisation programme in their region, which is a positive scenario. This trend must continue if waste minimisation is to become the key theme of future sustainable waste management in the UK as was intended by declarations at the Rio '92 conference and in subsequent UK Government policy and strategy.  相似文献   
105.
Recent legislation mandates an increased role for public participation in natural resource policy making. This paper presents an operational way to provide those impacted with relevant information and to enable public officials to assess public reaction to proposed policies. The methodology transforms results obtained from a multisector model of income formation and distribution into positive economic measures of distributional impacts. The usefulness of the methodology is illustrated in the context of a policy to increase coal surface mining on public lands.  相似文献   
106.
Mercury Vapor Determination in Hospitals   总被引:1,自引:0,他引:1  
The measurements of metallic mercury vapor were carried out in seven local hospitals, where mercury-containing products are widely used, as well as in one residence to check effectiveness of decontamination after mercury spillage. Hopcalite as a solid sorbent was used in active and passive sampling methods, and mercury was analyzed by CV-AAS technique. Good agreement was found between results of mercury measurements using active samplers (pumped hopcalite adsorption tubes) and passive (diffusion) monitors applied in indoor atmosphere. The results indicated the presence of metallic mercury vaporization sources in the assessed hospital rooms but in the majority of cases mercury levels did not exceed 1 g/m3 i.e. Polish permissible concentration for residence. However, in some of the hospital rooms, elevated concentrations of mercury vapor were found and airborne levels of up to 13.9 g/m3 were recorded. Higher concentrations of mercury vapor were observed in autumn season when compared to summer.  相似文献   
107.
A Method of Mercury Removal from Topsoil Using Low-Thermal Application   总被引:3,自引:0,他引:3  
Mercury contamination in the environment is problematic due to the unusual physical properties and well-recognized toxicity of this common metal. The bioavailability of mercury depends strongly on its chemical speciation. Anthropogenic mercury and its compounds appear in soil as hot spots located close to industrial facilities that used or produced mercury. The nature of the chemical production process, transportation and disposal practices often determined the chemical composition and distribution of mercury in the surrounding soils. Current ex situ soil remediation methods are expensive, produce undesirable side effects to the environment and usually involve transportation of contaminated soil.In this project, sponsored by the U.S. Department of Energy, a low-cost, simple approach to removing mercury from soil was evaluated. The process uses low-temperature thermal desorption of volatile metallic mercury and its compounds, and subsequent vapor capture.The project consisted of laboratory and plot-scale experiments. The laboratory efforts evaluated theoretical calculations of mercury removal as a function of time and temperature. The plot-scale experiment was a practical application of the laboratory results. For both experiments, mercury-polluted soil was obtained from a chemical production facility located in southern Poland. In laboratory experiments, at temperature 373 K total mercury concentration decreased in soil by nearly 32%. In plot-scale experiments, at temperature 440 K, about 60–70% of total mercury was removed from the soil.At the end of the experiment, a test of soil biological activity was performed to check if the high temperature applied to the soil did not impair the soil growth properties. There was no negative effect of temperature found.  相似文献   
108.
With increasing concern over degradation of aquatic resources, issues of liability, and maintenance costs, removal of small dams has become increasing popular. Although the benefits of removal seem to outweigh the drawbacks, there is a relative paucity of studies documenting the extent and magnitude of biological and chemical changes associated with dam removal, especially those evaluating potential changes in contaminant inventories. In August and November of 2000, a run-of-the-river dam on Manatawny Creek (southeast Pennsylvania) was removed in a two-stage process. To assess the effects of dam removal on the contaminant redistribution within the creek, sedimentary concentrations of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and trace metals (Cd, Cr, Cu, Ni, Pb, Zn) were evaluated prior to and several months after removal. Pre- and post-removal analyses revealed elevated and spatially variable concentrations of total PAHs (ranging from approximately 200 to 81,000 ng(g dry weight) and low to moderate concentrations of trace metals and PCBs. The concentrations of these sedimentary contaminants pre- versus post-removal were not significantly different. Additionally, though the impoundment received storm water run-off and associated contaminants from the adjacent city of Pottstown, the total inventory of fine-grain sediments in the impoundment prior to removal was very low. The removal of the low-level Manatawny Creek dam did not significantly redistribute contaminants downstream. However, each dam removal should be assessed on a case by case basis where the potential of sedimentary contaminant redistribution upon dam removal exists.  相似文献   
109.
Little is known about the importance of landscape and land cover to the implementation and performance of agricultural conservation projects designed to improve stream quality. In our study, we addressed the potential importance of landscape and land cover to conservation projects by measuring variation across 191 μ-basins (100–2400 ha) and integrating the observed variation into a study design aimed at determining the effectiveness of conservation projects. Our findings indicate that there are strong gradients across which landscape and land cover attributes vary. Land cover varied along a gradient of agricultural intensity, basin morphometry across gradients of stream closure and basin size, basin substrate was described by variation in drumlin formation, glacial landform type, and soil drainage, while agricultural conservation projects varied according to the level of project implementation. Correlation of these gradients found several associations between landscape and land cover, indicating that agricultural intensity was being constrained predominantly by drumlin formation and glacial landform type. Landscape and land cover did not appear to be determining factors in the implementation of conservation projects by land owners. Based on these findings we chose 32 μ-basins which represented the variability along each of the defined gradients for further study. We conclude that landscape scale variables demonstrate important variation and covariation that can and should be integrated into study designs for the assessment of streams and human activities affecting streams.  相似文献   
110.
Environmental and Ecological Statistics - Teleconnection, the strong dependence between two distant locations, provides interesting information for discovering the structures in spatial data. While...  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