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41.
通过对辽河群岩石中主要变质矿物的观察和研究,以岩石的变形历史作为变质结晶作用的相对时标,确定了矿物生长的时序特征及其演化过程。发现变质与变形既是有密切联系的又是各自独立的地质作用,辽河期的变形作用存在明显的3个变形幕,而辽河期的变质作用是个连续的完整的过程,无明显的热波动。变质作用高峰和变形作用高峰存在时间差。  相似文献   
42.
Polycyclic aromatic hydrocarbons (PAHs) contamination of topsoil in Benxi City, Northeast China was investigated in this study, and sampling sites were located in industrial area and residential area. Results demonstrate that there is high variability in the total PAHs concentrations, ranging from 783.00 ng/g to 729 076.29 ng/g dry weight in the topsoil of Benxi City and the pollution in industrial area is the most serious. The results also present that higher molecular weight PAHs (4–6 rings) contribute substantially (79.03%) to the overall content of PAHs. The PAHs sources were determined with factor analysis by nonnegative constraints, and the results show that PAHs originating from traffic tunnel, power plant, coke oven and residential emission sources, account for 27.10%, 40.81%, 20.11% and 11.98%, respectively, of the total. The PAHs pollution is the most serious around Benxi Iron and Steel Group Corporation, and the PAHs mainly originate from coke oven and traffic tunnel, with the average contribution rate of 57.40% and 42.60%, respectively. The source apportionment results are basically consistent with the industry distribution, and the geographical and climatic characteristics of the study area.  相似文献   
43.
以位于秦岭—大别造山带之北、华北陆块南部、地跨华北陆块稳定块体、陆块南部边缘变形带的南华北盆地为研究对象,通过对研究区42条不同时代的野外剖面详细观测,运用层序地层学理论,把南华北盆地作为一个整体系统,对青白口系—侏罗系层序界面特征及时空分布规律进行了系统分析,共识别出了8种类型层序界面的物质表现形式,分别是不整合面、渣状层、古喀斯特作用面、冲刷侵蚀面、超覆面、岩性岩相转换面、最大海泛面、最大湖泛面。并重点讨论了各类型界面的时空分布特征。结果表明:在时间演化上,从早到晚由海相—海陆过渡相—陆相,层序界面经历了海相沉积不整合、古喀斯特作用面、渣状层到陆相不整合面、冲刷侵蚀面等;在空间上,同一层序界面在不同相带表现形式不同,同一种类型的界面可在不同相带出现,但不同相带表现特征有一定差异性。  相似文献   
44.
基于地磁对电离层的影响,尝试利用GPS信号和Klobuchar模型估计地磁北极在地理坐标系中的位置,并建立了相应的数学模型。理论分析和数据验证了方法的可行性,如果进行Klobuchar模型的区域化改进和算法的完善,将更有利于地磁北极估计的可靠性和估计精度的提高。  相似文献   
45.
EVALUATION OF ECOLOGICAL SERVICES OF JILIN PROVINCE, NORTHEAST CHINA   总被引:1,自引:1,他引:1  
1INTRODUCTIONEcosystem services can be divided into two major cat-egories, one is system function, and the other is sys-tem services and goods provision, which provide not only materials such as food and medicine, but also support and maintenance of whole system. Ecological services contribute to the whole economic system, both directly and indirectly, and consequently repre-sent parts of the total value of our economy system (COSTANZA etal., 1997; GUO etal., 2001). Sustainable d…  相似文献   
46.
Under the special background of China, the cooperative innovation between different government-industry-university-research institutes plays an increasingly important role in the agricultural field. However, the existing literature has paid little attention to it. Considering the cooperation patents, published in the agriculture field stemming from the Full-text Database of China Patents as the study object, the spatial and institutional attribute of the authors as the data source, and by combining the social network and spatial econometrics analysis, this paper analyzes the structure evolution characteristics of cooperative innovation networks of agricultural government-industry-university-research institute in the city level of China in 1985–2014, based on the triple helix theory, with the influence factors discussed. This shows that, 1) since 1985, China's agricultural innovation level has been substantially increased, but the development degree of the cooperative innovation network is low, and the patent cooperation mainly relies on authors in the same unit; 2) enterprises play a leading role in the agricultural cooperative innovation. The effect of the government and hybrid organizations driven by the government is not obvious; 3) the cooperative innovation in the province and city dominates, and a multi-pole pattern has been formed. The cooperative innovation network structure evolves from a single helix empty core and double helix multi core to a double helix hierarchical network; 4) the city's science, education funding and personnel investment are key factors determining the agricultural cooperative innovation, while the agricultural development of the city presents slight negative impacts on it. The spatial mismatch of supply and demand is present in the technical cooperative innovation of China's agriculture. Therefore, the science enhancement and education investment to big agricultural provinces should be promptly implemented.  相似文献   
47.
We conducted acoustical surveys with a horizontal beam transducer to detect fish and with a vertical beam transducer to detect depth and macrophytes in two typical shallow lakes along the middle and lower reaches of the Changjiang(Yangtze) River in November 2013. Both lakes are subject to active fish management with annual stocking and removal of large fish. The purpose of the study was to compare hydroacoustic horizontal beam estimates with fish landings. The preliminary results show that the fish distribution patterns dif fered in the two lakes and were af fected by water depth and macrophyte coverage. The hydroacoustically estimated fish biomass matched the commercial catch very well in Niushan Lake, but it was two times higher in Kuilei Lake. However, acoustic estimates included all fish, whereas the catch included only fish 45 cm(smaller ones were released). We were unable to determine the proper regression between acoustic target strength and fish length for the dominant fish species in the two lakes.  相似文献   
48.
We investigated the effect of the replacement of dietary fish oil with vegetable oils on the growth and flesh quality of large yellow croaker(Larmichthys crocea). The basal diet(FO) was formulated to contain 66.5% fish meal and 6.4% menhaden fish oil; whereas the other 3 experimental diets were formulated by replacing the fish oil with 50% soybean oil(SO50), 100% soybean oil(SO100) and 100% palm oil(PO100), respectively. The 4 diets were randomly assigned to 4 floating sea cages(3.0 m × 3.0 m × 3.0 m), and each was stocked with 250 fish individuals with an initial average weight of 245.29 g ± 7.45 g. The fish were fed to apparent satiation twice a day at 5:00 and 17:00, respectively, for 12 weeks. Experimental analysis showed that the specific growth rate of fish fed SO50 or PO100 were significantly higher than that of fish fed FO or SO100(P0.05), and crude lipid contents of ventral muscle and viscera were significantly lower in fish fed FO than in those fed the other 3 diets(P0.05). No significant differences in condition factor, viscerosomatic index, hepatosomatic index, gutted yield and colorimetric values of fish among the dietary treatments were observed(P0.05). Compared to FO diet, SO50, SO100 and PO100 diets led to substantial decreases in the liquid loss and water loss from fresh fillets(1 d, 4℃)(P0.05). Similarly, thiobarbituric acid reactive substance(TBARS) values of fillets under different storage conditions(1 d, 4℃; 7 d, 4℃; 4 weeks,-20℃; 8 weeks,-20℃) decreased significantly after partial or complete replacement of fish oil with vegetable oils. These findings indicated that the growth performance and selected flesh quality properties(liquid holding capacity and TBARS value) of large yellow croaker were substantially improved by replacing dietary fish oil with vegetable oils.  相似文献   
49.
Fine root is critical to restrain soil erosion and its distribution pattern is of great influence on the restraining effects. This study studied the fine root biomass(Br) distribution of different aged Leucaena leucocephala(5, 10, 15 years) in debris flow source area in Jiangjia Gully by digging downward to the bottom at different distances to stem in three directions on slope. The results showed the Br increased dramatically by 143% from 5 years to 10 years and then rose slowly by 38% from 10 years to 15 years. The Br of 5 years was significantly asymmetric between uphill and alonghill directions, but there was little difference among directions for other ages, and a concentration trend appeared to exist in downhill and alonghill directions. Moreover, fine root(D≤1 mm) was significantly heavier than that of fine root(1mmD≤2 mm), playing a leading role in the vertical distribution of the whole fine root, with a logarithmic or an exponential function. The results presented may shed light on fine root distribution pattern and evaluation of its effect on slope stability in debris flow source area.  相似文献   
50.
?????????????????????????ο??????????????????????????????????????????????????????????NGA?????????????????????????飬??????????????????????о?????????????????????????????????????????2012?????4.7??????????е?????????????????????????????????????PGA??????S??a??T???????б????о??????????????????????????????????????????????????????????????????????????????????????????????  相似文献   
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