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   63篇
  免费   1篇
大气科学   29篇
地球物理   15篇
地质学   1篇
海洋学   14篇
天文学   1篇
综合类   1篇
自然地理   3篇
  2021年   1篇
  2020年   1篇
  2018年   1篇
  2014年   1篇
  2013年   4篇
  2012年   1篇
  2011年   4篇
  2010年   2篇
  2009年   1篇
  2008年   1篇
  2007年   1篇
  2006年   3篇
  2005年   1篇
  2004年   25篇
  2003年   2篇
  2002年   1篇
  2001年   5篇
  2000年   1篇
  1999年   4篇
  1998年   2篇
  1993年   1篇
  1992年   1篇
排序方式: 共有64条查询结果,搜索用时 250 毫秒
21.
Polycyclic Aromatic Hydrocarbon (PAH) pollution in coastal areas from the NW Mediterranean has been assessed by measuring bile PAH metabolites in two fish species, the red mullet – Mullus barbatus-and the sea comber – Serranus cabrilla – Bile crude samples were directly analysed by LC-fluorescence at the excitation/emission wavelengths of benzo[a]pyrene (380/430 nm). Subsequently, bile samples were hydrolysed and analysed by (a) LC-fluorescence at the excitation/emission wavelength pairs of naphthol (290/335 nm) and pyrenol (345/395 nm), and (b) gas chromatography–mass spectrometry (GC–MS) for the determination of individual PAHs. Qualitative and quantitative differences were recorded among sampling sites. Both species allowed us to detect different pollution gradients, the highest levels of FACs were observed in organisms caught in the vicinity of big industrial cities, whereas the lowest levels were recorded in organisms from Corsica and Sardinia. The obtained results highlight the usefulness of the LC-fluorescence technique as an initial screening method to assess PAH exposure in coastal fish.  相似文献   
22.
Many lichens are very sensitive to air pollution due to their symbiotic nature. However, they are generally less sensitive to toxic effects of trace elements; therefore they can be used as accumulator organisms for estimating concentrations of these elements in the environment. Heavy metal accumulation in lichens is a commonly used bioindication method for assessing heavy metal ambient levels. An active biomonitoring method was used for the determination of short-term accumulation of zinc, lead, arsenic and cadmium by epiphytic lichens transplanted at different localities in Slovenia polluted by heavy metals. The atomic absorption spectrophotometry method was used for the determination of heavy metal content in lichen thalli. The content of heavy metals in lichens collected in the background area with clean air (Rogla, Pohorje Mountains) was used as the reference value. Lichens were transplanted from Rogla using the branch transplantation technique for a period of 6 months in the surroundings of Slovenian thermal power plants (Velenje, otanj, Zavodnje, Veliki Vrh, Vnajnarje, and Dobovec) and close to the lead and zinc ore smelter at erjav. The monthly accumulation of heavy metals was comparable within years at selected locations. Heavy metal pollution was the highest at erjav despite of remediation of lead and zinc ore smelter. The monthly accumulation of all four heavy metals was statistically significantly higher in lichens exposed at erjav than at other localities.  相似文献   
23.
The results of a transplant experiment with the fruticose lichen Evernia prunastri aimed at monitoring the trends of trace elements deposition in a repeated biomonitoring study are reported. Data comparability between the two surveys and interpretation of the results were addressed in this study. The ratio between the concentration of each element after the exposure and in control samples prior to exposure (exposed-to-control ratio, EC ratio), as well as an appropriate interpretative scale, were adopted as a means of determining the temporal trends of element accumulation by lichen transplants. The results showed that the method adopted is indeed a reliable tool, pinpointing a Zn smelting plant and an oil refinery as principal pollution sources in the area, which indicate that elements associated with the former were similarly accumulated in both 2002 and 2003, while elements associated with the latter tended to decrease in 2003.  相似文献   
24.
In the year 2000, the elemental composition of mosses collected from 528 French sites has been studied as part of the 2000 European Moss Survey. Five moss species were collected: Scleropodium purum (56%), Pleurozium schreberi (18%), Hypnum cupressiforme (18%), Thuidium tamariscinum (4.5%.) and Hylocomium splendens (3.5%). Mosses were kept whole for analysis, including green and brownish parts. Summary statistics on element concentrations (Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Na, Ni, P, Pb, Rb, Sr, V and Zn), and comparisons made with data from the other 27 participating European countries are shown here. The sources of these elements are identified using calculations of enrichment factors (EF) and principal component analysis (PCA). Finally, the spatial distribution in France of 10 elements is also shown, using maps underscoring areas showing highest concentration levels for each metal.  相似文献   
25.
Lichens are now well known for their potential as bio-indicators of environmental pollution, but less is known about their suitability as quantitative biomonitors for atmospheric emissions of tritium (mainly as tritiated water, HTO) and radiocarbon (as 14CO2) from nuclear facilities, although both radionuclides could result in non-trivial individual or collective radiation doses due to their high environmental mobility and their long half-lives. 3H and 14C are fixed in lichens mainly by the photosynthesis of the algal partner and then stored in the organic molecules of both alga and fungus. They have the advantage of allowing the monitoring of atmospheric water vapour without interference of soil water or soil organic substances as long as soil-inhabiting species are avoided. Lichens were collected in the surroundings of (military and civil) nuclear facilities, in areas away from any direct source of contamination and some were transplanted from a contaminated area to a non-contaminated one. The influence of the nuclear facilities can be clearly traced, sometimes in a spectacular way and the first results of analyses after transplants give a base for estimating the effective half-life of 3H in lichens.  相似文献   
26.
Test shallot plants Allium cepa L. var. ascalonicum were exposed to field conditions at six research plots in the most polluted areas in Slovenia in the vegetation seasons in 1999 and 2000. The intention of this research was to evaluate the influence of air pollution on mitotic activity and frequency of chromosomal aberrations in meristematic tissues of root tips of bioindication plants. Significant differences in the mitotic index and in frequency of chromosomal aberrations at different sampling plots in pot experiments were found and the correlation between the ozone concentration and the mitotic index was determined. The results showed the presence of cytotoxic substances at chosen sampling sites, which caused the decrease of mitotic cell division and the presence of genotoxic substances, which resulted in the increase of frequency of chromosomal aberrations.  相似文献   
27.
The sorption studies of Hg2+, CH3Hg+ and elemental mercury (Hg0) were carried out on lichen (Parmelia sulcata) and moss (Funaria hygrometrica) samples under laboratory conditions. Desorption studies with HCl indicate that inorganic mercury (Hg+2) and methyl mercury could be completely desorbed with 1 M HCl and 0.5 M HCl, respectively. Samples loaded with elemental mercury, however, needed 4–5 M HCl concentration for complete desorption of the adsorbed elemental mercury. When similar desorption studies were carried out with field samples collected around a thermometer factory with elevated levels of mercury (8 mg/kg), it was found that only about 10–15% of total mercury was desorbed with 1M HCl, while 4–5 M acid was required for complete desorption. We have tried to correlate this information to understand the transformations of mercury species that may occur either in the atmosphere or on the biomonitors. The results indicated that the elemental mercury, the principal form of mercury contamination around the thermometer factory, is converted into a strongly held form by some chemical binding agents on the surface of lichen/moss, or elemental mercury could diffuse into the cells of the lichen/moss, which then needs the stronger acid to release it. Sorption capacity studies suggest that the lichens and mosses can also be used as sorbent material for the decontamination of inorganic and methyl mercury from aqueous solutions.  相似文献   
28.
回顾了近年来海洋环境污染生物监测中的海洋底栖无脊椎动物早期发育和变态阶段的毒性实验的研究进展 ,强调应根据敏感性和代表性水平来选取生物有机体进行生物毒性实验 ,并探讨了运用幼虫变态实验来进行海洋污染监测的可行性  相似文献   
29.
30.
This study demonstrates application of artificial neural networks (ANNs) for identifying the origin of green macroalgae (Enteromorpha sp. and Cladophora sp.) according to their concentrations of Cd, Cu, Ni, Zn, Mn, Pb, Na, Ca, K and Mg. Earlier studies confirmed that algae can be used for biomonitoring surveys of metal contaminants in coastal areas of the Southern Baltic. The same data sets were classified with the use of different structures of radial basis function (RBF) and multilayer perceptron (MLP) networks. The selected networks were able to classify the samples according to their geographical origin, i.e. Southern Baltic, Gulf of Gdańsk and Vistula Lagoon. Additionally in the case of macroalgae from the Gulf of Gdańsk, the networks enabled the discrimination of samples according to areas of contrasting levels of pollution. Hence this study shows that artificial neural networks can be a valuable tool in biomonitoring studies.  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