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61.
62.
Jari Syväranta Julien Cucherousset Dorothée Kopp Aurélia Martino Régis Céréghino Frédéric Santoul 《Die Naturwissenschaften》2009,96(5):631-635
Many anadromous fish species, when migrating from the sea to spawn in fresh waters, can potentially be a valuable prey for
larger predatory fish, thereby efficiently linking these two ecosystems. Here, we assess the contribution of anadromous fish
to the diet of European catfish (Silurus glanis) in a large river system (Garonne, southwestern France) using stable isotope analysis and allis shad (Alosa alosa) as an example of anadromous fish. Allis shad caught in the Garonne had a very distinct marine δ13C value, over 8‰ higher after lipid extraction compared to the mean δ13C value of all other potential freshwater prey fish. The δ13C values of European catfish varied considerably between these two extremes and some individuals were clearly specializing
on freshwater prey, whereas others specialized on anadromous fish. The mean contribution of anadromous fish to the entire
European catfish population was estimated to be between 53% and 65%, depending on the fractionation factor used for δ13C. 相似文献
63.
本文根据宁夏固原饮水型氟中毒事件,从氟污染的形成,氟的环境化学特性及其迁移转化,氟对人体健康的影响,氟中毒的机制原理等几个方面进行了阐述,并提出防治对策及治理措施。 相似文献
64.
Birds migrating along coastlines may be at increased risk if displacement occurs toward open-ocean. Eastern North America
experiences prevailing northwesterly winds during autumn, which could compel some migrants to drift eastward. Therefore, migrants
at stop-over sites along this route may be a mixture of on- and off-course individuals. We assessed whether orientation behavior
of juvenile yellow-rumped warblers (Dendroica coronata) captured at a stop-over site in southern Nova Scotia was related to where they originated from (i.e., likely on/off-course).
We hypothesized three scenarios after displacement: 1) continued orientation in the migratory direction selected before displacement,
2) orientation from the new location toward the previous destination, or 3) correction to regain the original pathway. Using
stable isotopes, we determined that stop-over migrants originated from nearby areas (and assumed on-course) and as far away
as western Hudson Bay, over 1,600 km northwest (and assumed off-course) of the site. We used video-based orientation registration
cages to determine an individuals’ migratory orientation. Because numerous factors influence migratory orientation (e.g.,
fuel reserves, celestial cues), we simultaneously assessed the influence of body condition and cloud cover, in addition to
geographic origin, on orientation behavior. Individuals that originated closer to the site tended to orient more southwesterly.
Orientation directions became increasingly more west-northwesterly the further away an individual originated from the site
(i.e., the more likely it was to have been displaced). The result is most consistent with scenario three: individuals from
northwest origins likely respond to easterly displacement by orienting westerly to reestablish their previous migratory route. 相似文献
65.
采用一维土柱下渗实验和垂向入渗模型相结合的方式,研究垃圾渗滤液中邻苯二甲酸二乙基己基酯(DEHP)和邻苯二甲酸二正丁酯(DBP)在土壤中的垂向迁移演化规律。结果表明:原状土和混有石英砂土的土柱对DBP的吸附能力均强于DEHP,而混有石英砂的土柱中DEHP、DBP均出现不同程度的穿透现象,且DEHP的穿透速度比DBP要快2倍;做或不做防渗处理,DEHP和DBP渗出量均呈前期快速增长而后期归于稳定的趋势,防渗对DBP效果较DEHP好;垂向入渗模型与一维土柱实验结果一致,该模型可用于其他区域有机污染物在土壤中垂向迁移的研究。 相似文献
66.
Weigelin-Schwiedrzik S 《Journal of environmental management》2008,87(2):216-225
While the People's Republic of China appears on a daily basis in all of the important newspapers around the world with its enormous successes in modernizing its economy, life in the Chinese countryside usually does not attract international attention. However, we know from a wide range of reports that the situation in the Chinese countryside is getting more and more complicated with local corruption, pollution and poverty growing in most parts of the country. The Chinese language press reports on a growing number of local uprisings in remote areas. While some analysts regard the situation in the countryside as a potential threat to the ongoing peaceful process of economic reform in China, China seems to be well prepared to cope with this change and the state is comparatively flexible in dealing with unrest among the rural population. So far the system itself has not been challenged by peasant discontent. This article introduces the idea that the distance between state and rural society is the basis of this flexibility. It will analyze a major policy document issued by the state and party leadership in order to show how state and rural society interact on the basis of a still insurmountable distance between state and rural society. 相似文献
67.
68.
Migration of 137Cs and 90Sr in undisturbed soil was studied in large lysimeters three and four years after contamination, as part of a larger European project studying radionuclide soil–plant interactions. The lysimeters were installed in greenhouses with climate control and contaminated with radionuclides in an aerosol mixture, simulating fallout from a nuclear accident. The soil types studied were loam, silt loam, sandy loam and loamy sand. The soils were sampled to 30–40 cm depth in 1997 and 1998. The total deposition of 137Cs ranged from 24 to 45 MBq/m2, and of 90Sr from 23 to 52 MBq/m2. It was shown that migration of 137Cs was fastest in sandy loam, and of 90Sr fastest in sandy loam and loam. The slowest migration of both nuclides was found in loamy sand. Retention within the upper 5 cm was 60% for both 137Cs and 90Sr in sandy loam, while in loamy sand it was 97 and 96%, respectively. In 1998, migration rates, calculated as radionuclide weighted median depth (migration centre) divided by time since deposition were 1.1 cm/year for both 137Cs and 90Sr in sandy loam, 0.8 and 1.0 cm/year, respectively, in loam, 0.6 and 0.8 cm/year in silt loam, and 0.4 and 0.6 cm/year for 137Cs and 90Sr, respectively, in loamy sand. A distinction is made between short-term migration, caused by events soon after deposition and less affected by soil type, and long-term migration, more affected by e.g. soil texture. Three to four years after deposition, effects of short-term migration is still dominant in the studied soils. 相似文献
69.
Luigi Monte 《Ecological modelling》1998,110(3):134
In the present paper a collective model for predicting the migration of dissolved toxic substances through drainage areas is described. The model has been validated using data for 137Cs and 90Sr concentrations in water of some European contaminated rivers following the atmospheric fall-out from the accident at the Chernobyl power plant. It has been demonstrated that the migration rate λ (s−1) of a dissolved toxic substance from a catchment may be evaluated by the following approximate formula: λ=(c ln t+d)/t, where t is the time from a pulse deposition event and the coefficients c and d depend on the characteristics of the substance. It has been shown that the mathematical form of the transfer function (flux of dissolved substance at time t following a single pulse deposition of a pollutant onto the catchment) of a toxic substance from a drainage area is very simple. Moreover, the values of the transfer function parameters are slightly variable despite the large range of characteristics of the catchments here examined. Indeed, the statistical aggregation of competing migration processes can lead to ‘stable’ collective behaviours that are less variable than each single process. 相似文献
70.
Migration of uranium(IV)/(VI) in the presence of humic acids in quartz sand: a laboratory column study 总被引:1,自引:0,他引:1
Mibus J Sachs S Pfingsten W Nebelung C Bernhard G 《Journal of contaminant hydrology》2007,89(3-4):199-217
The migration behavior of U(IV) and U(VI) in the presence of humic acid was studied in a quartz sand system. Laboratory column experiments were performed using humic acid, U(VI) in humic acid absence, U(IV) and U(VI) in humic acid presence, and for comparison a conservative tracer. In experiments using humic acid, both redox species of U migrate nearly as fast as the conservative tracer. Humic acid accelerates the U(VI) breakthrough compared to the humic acid-free system. There are strong indications for a similar effect on the U(IV) transport. At the same time, a part of U(IV) and U(VI) associated with the humic acid is immobilized in the quartz sand due to humic colloid filtration thus producing a delaying effect. Tailing at a low concentration level was observed upon tracer elution. The experimental breakthrough curves were described by reactive transport modeling using equations for equilibrium and kinetic reactions. The present study demonstrates that humic acids can play an important role in the migration of actinides. As natural organic matter is ubiquitous in aquifer systems, the humic colloid-borne transport of actinides is of high relevance in performance assessment. 相似文献