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   102篇
  免费   3篇
  国内免费   3篇
环保管理   4篇
综合类   39篇
基础理论   28篇
污染及防治   33篇
评价与监测   3篇
社会与环境   1篇
  2022年   1篇
  2021年   1篇
  2018年   1篇
  2017年   4篇
  2015年   7篇
  2014年   1篇
  2013年   5篇
  2012年   7篇
  2011年   3篇
  2010年   1篇
  2009年   9篇
  2008年   5篇
  2007年   8篇
  2004年   1篇
  2003年   7篇
  2001年   1篇
  1999年   2篇
  1998年   2篇
  1997年   3篇
  1996年   1篇
  1995年   3篇
  1994年   4篇
  1993年   3篇
  1991年   1篇
  1990年   3篇
  1987年   1篇
  1984年   1篇
  1983年   1篇
  1979年   1篇
  1971年   1篇
  1968年   1篇
  1966年   2篇
  1960年   1篇
  1959年   3篇
  1958年   3篇
  1957年   1篇
  1956年   2篇
  1955年   3篇
  1954年   1篇
  1949年   1篇
  1944年   1篇
排序方式: 共有108条查询结果,搜索用时 312 毫秒
91.
The aim of this study was to determine a new spectrum of substances that will be selected for future breast milk monitoring in Bavaria, Germany. Up to now, the analysis of breast milk in Bavaria was limited to selected organochlorine pesticides (OCP) and polychlorinated biphenyls (PCB). Information on background levels of toxicologically interesting substances, such as dioxins and dioxin-like polychlorinated biphenyls (dl-PCB) or on flame retardants, such as polybrominated diphenyl ethers (PBDE) are very limited or not available for Bavaria. We present here levels on OCP, some nitro musks, indicator PCB, polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and dl-PCB concentrations in breast milk collected at 12 weeks post-partum of 43 primiparous mothers living in Bavaria. The average concentrations of PCDD, PCDF and dl-PCB were 4.98, 4.93 and 9.92 pg WHO-TEQ g(-1) lipid, respectively. The mean contribution of PCDD, PCDF, non-ortho and mono-ortho PCB to the total WHO-TEQ is consistently about 25% each. Furthermore the concentration on PBDE in breast milk at two sampling points, 12 weeks and 16 weeks after delivery, were determined. Overall, 19 PBDE congeners were analysed, however the level of 12 PBDE congeners were below the limit of detection. BDE-153 and BDE-47 were the predominant congeners accounting for about 66% of the total PBDE. The means of the total concentrations of PBDE (five congeners) at the first and second sampling point were 1.90 and 2.03 ng g(-1) lipid, respectively. Based on our results the overall concentrations of the analysed substances in milk samples from Bavaria are consistent with the levels of breast milk samples of other European countries reflecting the low background body burden of these compounds.  相似文献   
92.

Background

The European chemicals regulation REACH includes the legal duty for suppliers to inform consumers on request about the presence of substances of very high concern (SVHCs) in articles. Since this requirement has been in force now for 10 years, the intention of this study was to find out whether information on SVHCs is adequately communicated to the consumer today. Data on the presence of SVHCs in articles were collected as a prerequisite for the subsequent requests for a targeted choice of articles to examine the operability of the ‘right to know.’

Results

Literature data show that SVHCs have been measured and described in a large variety of commodities. 32% of 334 information requests for articles which were suspected to contain SVHCs were answered by suppliers and a minor number of these answers were of good quality. Only two respondents indicated the presence of SVHCs in their articles. Suppliers are not legally obliged to respond to requests if their articles are free of SVHCs. Therefore, the absence of a response might be interpreted as an indication that SVHCs are present below 0.1% in the articles in question. However, there are certain doubts that only two out of 334 articles suspected contain SVHCs.

Conclusions

The data question whether the ambitious aims of the SVHC regime can be achieved under the present conditions. Measures are proposed on how to improve implementation of the information requirement and to amend the legal criteria in the upcoming REACH revision.
  相似文献   
93.
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   
94.
Between 1980 and 1984, plankton was collected for metal analysis during four expeditions in the Baltic Sea. for comparison, samples from adjacent areas of the northeastern Atlantic Ocean were also taken. the mixed net-plankton samples were analyzed by AAS for metals (Al, Cd, Co, Cr, Cu. Fe, Mn, Ni, Pb, and Zn). the results are discussed with regard to spatial and temporal trends and for comparison with data from other authors. Correlations among the contents of the different metals and between the metal contents and 'external factors' including salinity, season, percentage of co-collected phytoplankton, and concentration of dissolved and particulate metals in the water are considered.

There is a tendency for higher metal contents in plankton from the brackish Baltic Sea (Al, Mn and Hg), while other metals (e.g. Cd) show higher levels in samples taken from the marine environment. Except for mercury, no clear correlations could be found between the metal content in plankton and the dissolved concentration of the same metal in the ambient water. Otherwise, the contents of aluminium, iron, manganese and zinc in the suspended particulate matter and in the plankton seem to be partly related to each other.  相似文献   
95.
96.
1. The importance of the recycling of organic matter for the overall carbon and nutrient flow in a food web, e.g., by the microbial loop has been recognized for pelagic and other ecosystems during the last decade. In contrast, analyses of the trophic food web structure conducted, e.g., by network analysis based on mass‐balanced flow diagrams (i.e., computation of, e.g., trophic positions and transfer efficiencies, organismal composition of trophic levels) which greatly contribute to our understanding of the flow and cycling of matter in food webs, have not yet responded adequately to this fact by developing coherent techniques with which dead organic matter and its consumers could be considered in the models. 2. At present, dead organic matter (measured in units of carbon or nutrients) is either allocated to a fixed trophic position (between zero and one), or the trophic position of dead autochthonous material depends on the trophic position of the organisms which released it. This causes partially ambiguous and inconsistent interpretations of key measures like trophic transfer efficiences and trophic positions and greatly hampers cross‐system comparisons. 3. The present paper describes and compares four different definitions of the trophic position of dead autochthonous organic material which have either been newly invented or already used. Their impact on the resulting trophic positions of individual groups is illustrated using a food web model from the pelagic zone of Lake Constance. The present analysis evaluates the partially far reaching consequences of the definition chosen, and suggests to allocate all dead organic material to the ‘zeroth’ trophic level irrespectively of its origin (allochthonous or autochthonous), chemical composition and the commodity used to quantify the food web model (e.g., units of carbon or nutrients). By this means trophic positions and trophic transfer efficiencies get a clear and consistent ecological interpretation, while inconsistencies between analyses conducted in units of carbon or nutrients and some operational problems can be overcome and cross‐system comparisons and empirical verification are facilitated.  相似文献   
97.
98.
99.
100.
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