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排序方式: 共有803条查询结果,搜索用时 31 毫秒
651.
石杉碱戊和石杉碱己的结构   总被引:3,自引:0,他引:3  
在石杉[Huperziaserrata(Thunb.)Trev.]中分得了命名为石杉碱成素和已素的2个新生物碱,并用2D-NMR和MS测定了它们的化学结构.  相似文献   
652.
物元模型及其在区域水环境质量评价中的应用   总被引:8,自引:0,他引:8  
将灰色关联聚类法引入评价指标权重的确定,在物元分析的基础上,建立了基于聚类权重的区域水环境质量综合评价物元模型。通过实例分析将该模型与其它评价方法进行比较。结果显示,该模型弥补了模糊综合评判法、灰色聚类法的不足,评价结果合理,信息利用率高。  相似文献   
653.
综述了国内自由锻CAPP技术开发与应用情况,归纳了其不同发展阶段主要功能及技术特征,并展望了其发展和应用前景。  相似文献   
654.
Are chaos and catastrophe theories relevant to environmental sciences?   总被引:1,自引:0,他引:1  
Data acquired in the area of Environmental Sciences are by their very nature often discontinuous and abrupt. As such, the mathematical theories of catastrophe and chaos may be of use in analyzing such scientific data and in formulating mathematical models.  相似文献   
655.
Zhu C  Wang L  Kong L  Yang X  Wang L  Zheng S  Chen F  MaiZhi F  Zong H 《Chemosphere》2000,41(3):303-309
The photocatalytic degradation performance of photocatalysts TiO2 supported on 13-X, Na-Y, 4A zeolites with different loading content was evaluated using the photocatalytic oxidation of dyes direct fast scarlet 4BS and acid red 3B in aqueous medium. The results showed that the best reaction dosage of TiO2-zeolite catalysts is about 2 g/l and the photocatalytic kinetics follows first order for all supported catalysts. The photocatalytic activity order of the three series catalysts is 13X type >Y type >4A type. The physical state of titanium dioxide on the supports is evaluated by X-ray photoelectron spectra (XPS), powder X-ray diffraction (XRD), BET, and FTIR.  相似文献   
656.
Urban-scale air pollutants for sulfur dioxide, nitrogen dioxide, particulate matter with aerodynamic diameter > or = 10 microm, and ozone (O3) were simulated over the Seoul metropolitan area, Korea, during the period of July 2-11, 2002, and their predicting capabilities were discussed. The Air Pollution Model (TAPM) and the highly disaggregated anthropogenic and the biogenic gridded emissions (1 km x 1 km) recently prepared by the Korean Ministry of Environment were applied. Wind fields with observational nudging in the prognostic meteorological model TAPM are optionally adopted to comparatively examine the meteorological impact on the prediction capabilities of urban-scale air pollutants. The result shows that the simulated concentrations of secondary air pollutant largely agree with observed levels with an index of agreement (IOA) of >0.6, whereas IOAs of approximately 0.4 are found for most primary pollutants in the major cities, reflecting the quality of emission data in the urban area. The observationally nudged wind fields with higher IOAs have little effect on the prediction for both primary and secondary air pollutants, implying that the detailed wind field does not consistently improve the urban air pollution model performance if emissions are not well specified. However, the robust highest concentrations are better described toward observations by imposing observational nudging, suggesting the importance of wind fields for the predictions of extreme concentrations such as robust highest concentrations, maximum levels, and >90th percentiles of concentrations for both primary and secondary urban-scale air pollutants.  相似文献   
657.
本文利用向含氟废水中加入适量石灰和聚合氯化铝PAC ,然后投加适量钙盐、磷酸和聚丙烯酰胺PAM的二级处理工艺除氟。通过控制合适的 pH、钙盐和磷酸的投加量、反应时间、反应温度、搅拌强度和絮凝剂的投加量 ,确定了最佳的除氟工艺 ,可以使氟的浓度降至 5mg/L ,达到国家一级排放标准GB8978 1996。  相似文献   
658.
Nordberg G  Jin T  Bernard A  Fierens S  Buchet JP  Ye T  Kong Q  Wang H 《Ambio》2002,31(6):478-481
This paper presents the main findings of a study on health effects of environmental cadmium pollution in China, performed in 1998, i.e. approximately 25 years after the first warnings of such effects were published in Ambio. Forearm bone mineral density (BMD) and renal dysfunction were assessed in population groups exposed to cadmium via rice. Decreased BMD was found in postmenopausal women with elevated urinary cadmium (CdU) or cadmium in blood (CdB) and among men with elevated CdB. Also, clear and statistically significant dose-effect and dose-response relationships were found between CdB or CdU and renal dysfunction (increased excretion of retinol-binding protein). This is the first report of bone effects among Cd-exposed population groups in Asia outside Japan. The report is also of interest since it demonstrates that bone effects, a comparatively severe adverse health effect of Cd, in combination with renal dysfunction, still occurs in environmentally exposed population groups in Asia. Recent reports on bone effects in Cd-exposed population groups in Europe are discussed.  相似文献   
659.
利用HFS 1型深度光氧化废水处理设备对活性艳蓝K3R、酸性红 3B、活性黑KNB、酸性红A、直接耐酸大红4BS等 5种染料的水溶液和多菌灵农药废水进行了深度光氧化处理。结果表明 :(1)染料在处理 5min后 ,脱色率都在 90 %以上 ;处理 15min后 ,CODCr的去除率除活性艳蓝K3R较低外 ,其余的都在 80 %以上 ;BOD5/CODCr的值都有所增大。 (2 )多菌灵农药废水 (经稀释 )处理 4 0min后CODCr的去除率为 5 7.0 % ,BOD5/CODCr的值由 0 .2 0增加到 0 .4 4。 (3)采用深度光氧化 -絮凝的工艺处理多菌灵农药废水 ,CODCr的去除率为 5 7.5 %。  相似文献   
660.
Despite the economic importance of oysters due to the high aquaculture production of several species, the current knowledge of oyster phylogeny and systematics is still fragmentary. In Europe, Ostrea edulis, the European flat oyster, and Ostreola stentina, the Provence oyster or dwarf oyster, are both present along the European and African, Atlantic and Mediterranean, coasts. In order to document the relationship not only between O. stentina and O. edulis, but also with the other Ostrea and Ostreola species, we performed a sequence analysis of the 16S mitochondrial fragment (16S rDNA: the large subunit rRNA-coding gene) and the COI fragment (COI: cytochrome oxidase subunit I). Oysters were sampled from populations in Portugal (two populations), Tunisia (two populations) and Morocco (one population), identified as O. stentina on the basis of shell morphological characters. Our data supported a high degree of differentiation between O. stentina and O. edulis and a close relationship between O. stentina and both Ostrea aupouria (from New Zealand) and Ostreola equestris (from Mexico Gulf/Atlantic). The status of this geographic disjunction between these closely related species is discussed. Furthermore, although identified in a separate genus Ostreola by Harry (Veliger 28:121–158, 1985), our molecular data on O. stentina, together with those available for the other two putative congeneric species, O. equestris and Ostreola conchaphila, would favour incorporation of Ostreola in Ostrea. Finally, a PCR-RFLP approach allowed the rapid identification of O. edulis and O. stentina.  相似文献   
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