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急性心肌梗死与季节相关性调查 被引量:5
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作者 刘战英 靳学雷 《现代中西医结合杂志》 CAS 2000年第20期2078-2078,共1页
关键词 急性心肌梗死 季节相关性调查 流行病学
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霞浦县野生动物资源调查成果分析
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作者 姚勇 《林业勘察设计》 2004年第2期77-79,共3页
对霞浦县野生动物资源开展调查,并对调查成果的成因、影响因素进行分析,提出应在适当的季节、时间开展调查以及建立野外监测点,定期观察野生动物等建议。
关键词 霞浦县 野生动物 资源调查 调查季节 调查时间 野外监测点
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Effects of seasonal water-level fluctuation on soil pore structure in the Three Gorges Reservoir,China 被引量:9
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作者 ZHANG Shu-juan TANG Qiang +5 位作者 BAO Yu-hai HE Xiu-bin TIAN Feng-xia LüFa-you WANG Ming-feng Raheel ANJUM 《Journal of Mountain Science》 SCIE CSCD 2018年第10期2192-2206,共15页
Inundation of the Three Gorges Reservoir has created a 30-m water-level fluctuation zone with seasonal hydrological alternations of submergence and exposure, which may greatly affect soil properties and bank stability... Inundation of the Three Gorges Reservoir has created a 30-m water-level fluctuation zone with seasonal hydrological alternations of submergence and exposure, which may greatly affect soil properties and bank stability. The aim of this study was to investigate the response of soil pore structure to seasonal water-level fluctuation in the reservoir, and particularly, the hydrological change of wetting and drying cycles. Soil pore structure was visualized with industrial X-ray computed tomography and digital image analysis techniques. The results showed that soil total porosity(? 100 ?m), total pore number, total throat number, and mean throat surface area increased significantly under wetting and drying cycles. Soil porosity, pore number and throat numberwithin each size class increased in the course of wetting and drying cycles. The coordination number, degree of anisotropy and fractal dimension were indicating an increase. In contrast, the mean shape factor, pore-throat ratio, and Euler-Poincaré number decreased due to wetting and drying cycles. These illustrated that the wetting and drying cycles made soil pore structure become more porous, continuous, heterogeneous and complex. It can thus be deduced that the water-level fluctuation would modify soil porosity, pore size distribution, and pore morphology in the Three Gorges Reservoir, which may have profound implications for soil processes, soil functions, and bank stability. 展开更多
关键词 Soil pore structure X-ray computed tomography Image analysis Wetting and drying cycles Water-level fluctuation Three Gorges
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Seasonal variations in fouling diatom communities on the Yantai coast 被引量:1
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作者 杨翠云 王建华 +2 位作者 于洋 刘苏静 夏传海 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2015年第2期439-446,共8页
Fouling diatoms are a main component of biofilm,and play an important role in marine biofouling formation. We investigated seasonal variations in fouling diatom communities that developed on glass slides immersed in s... Fouling diatoms are a main component of biofilm,and play an important role in marine biofouling formation. We investigated seasonal variations in fouling diatom communities that developed on glass slides immersed in seawater,on the Yantai coast,northern Yellow Sea,China,using microscopy and molecular techniques. Studies were conducted during 2012 and 2013 over 3,7,14,and 21 days in each season. The abundance of attached diatoms and extracellular polymeric substances increased with exposure time of the slides to seawater. The lowest diatom density appeared in winter and the highest species richness and diversity were found in summer and autumn. Seasonal variation was observed in the structure of fouling diatom communities. Pennate diatoms Cylindrotheca,Nitzschia,Navicula,Amphora,Gomphonema,and Licmophora were the main fouling groups. Cylindrotheca sp. dominated in the spring. Under laboratory culture conditions,we found that Cylindrotheca grew very fast,which might account for the highest density of this diatom in spring. The lower densities in summer and autumn might result from the emergence of fouling animals and environmental factors. The Cylindrotheca sp. was identified as Cylindrotheca closterium using18 S rDNA sequencing. The colonization process of fouling diatoms and significant seasonal variation in this study depended on environmental and biological factors. Understanding the basis of fouling diatoms is essential and important for developing new antifouling techniques. 展开更多
关键词 BIOFOULING diatom community seasonal variation Cylindrotheca closterium
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Tobacco Production Baseline Survey in Serengeti, Tarime and Rorya Districts, Mara Region
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作者 Nicholaus Musimu Kuboja Asheri Mwamba Kalala +1 位作者 Jacob Bulenga Lisuma Mariam Mrutu 《Journal of Agricultural Science and Technology(B)》 2012年第4期471-481,共11页
Using 2009/2010 cropping season survey data from 181 randomly selected smallholder tobacco farmers, this study provides baseline information on tobacco farming in Mara region. Both descriptive and inferential statisti... Using 2009/2010 cropping season survey data from 181 randomly selected smallholder tobacco farmers, this study provides baseline information on tobacco farming in Mara region. Both descriptive and inferential statistics were employed in data analysis. Result indicates that farmers adopted tobacco farming from tobacco farmers in Kenya. Drought and inadequate supply of inputs were identified as the major production constraints. Others were incidence of pests and diseases, shortage of fire woods, poor extension services and hailstones. Low selling price and contradicting grading systems were the major tobacco marketing constraints. The study also revealed that access to extension services was similar across study districts with over 65.7% of the respondents accessing technical expertise mainly from Alliance One Tanzania employees. Given the positive and negative impacts of tobacco farming, majority of the respondents (95.6%) still were willing to proceed with tobacco farming as their main source of income. However, watermelon, maize and sunflower were ranked as first priority alternative cash crops to tobacco in Serengeti, Tarime and Rorya districts, respectively. This study concludes that tobacco farming still is the main household income source; hence, more investment is required to ensure sustainable economic develooment of rural communities in Mara reeion. 展开更多
关键词 BASELINE MARKETING production tobacco.
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Seasonal Changes in Phytoplankton Biomass and Dominant Species in the Changjiang River Estuary and Adjacent Seas:General Trends Based on Field Survey Data 1959-2009 被引量:7
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作者 YANG Shu HAN Xiurong +3 位作者 ZHANG Chuansong SUN Baiye WANG Xiulin SHI Xiaoyong 《Journal of Ocean University of China》 SCIE CAS 2014年第6期926-934,共9页
The characteristics of seasonal variation in phytoplankton biomass and dominant species in the Changjiang River Estuary and adjacent seas were discussed based on field investigation data from 1959 to 2009. The field d... The characteristics of seasonal variation in phytoplankton biomass and dominant species in the Changjiang River Estuary and adjacent seas were discussed based on field investigation data from 1959 to 2009. The field data from 1981 to 2004 showed that the Chlorophyll-a concentration in surface seawater was between 0.4 and 8.5 ktg dm-3. The seasonal changes generally presented a bimodal trend, with the biomass peaks occurring in May and August, and Chlorophyll-a concentration was the lowest in winter. Seasonal biomass changes were mainly controlled by temperature and nutrient levels. From the end of autumn to the next early spring, phytoplankton biomass was mainly influenced by temperature, and in other seasons, nutrient level (including the nutrient supply from the terrestrial runoffs) was the major influence factor. Field investigation data from 1959 to 2009 demonstrated that dia- toms were the main phytoplankton in this area, and Skeletonerna costatum, Pseudo-nitzschia pungens, Coscinodiscus oculus-iridis, Thalassinoema nitzschioides, Paralia sulcata, Chaetoceros lorenzianus, Chaetoceros curvisetus, and Prorocentrum donghaiense Lu were common dominant species. The seasonal variations in major dominant phytoplankton species presented the following trends: 1) Skeletonema (mainly S. costatum) was dominant throughout the year; and 2) seasonal succession trends were Coscinodiscus (spring) →Chaetoceros (summer and autumn) → Coscinodiscus (winter). The annual dominance of S. costatum was attributed to its environmental eurytopicity and long standing time in surface waters. The seasonal succession of Coscinodiscus and Chaetoceros was associated with the seasonal variation in water stability and nutrient level in this area. On the other hand, long-term field data also indicated obvious interannual variation of phytoplankton biomass and community structure in the Changjiang River Estuary and adjacent seas: average annual phytoplankton biomass and dinoflagellate proportion both presented increased trends during the 1950s - 2000s. 展开更多
关键词 the Changjiang River Estuary and adjacent seas phytoplankton biomass dominant species seasonal variation
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拱北口岸鼠蚤调查
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作者 曾林泉 《中国国境卫生检疫杂志》 CAS 1990年第4期234-236,共3页
本文介绍了拱北口岸鼠体外寄生蚤种属、季节消长的调查结果。全年共捕活鼠6种126只,染蚤鼠67只,染蚤率53.2%,共检获蚤259只,总蚤指数2.06,经鉴定为3属4种蚤,其中以印鼠客蚤为优势种,占90%。全年中以春夏4、5月和秋季8、9月为高峰。啮齿... 本文介绍了拱北口岸鼠体外寄生蚤种属、季节消长的调查结果。全年共捕活鼠6种126只,染蚤鼠67只,染蚤率53.2%,共检获蚤259只,总蚤指数2.06,经鉴定为3属4种蚤,其中以印鼠客蚤为优势种,占90%。全年中以春夏4、5月和秋季8、9月为高峰。啮齿目黄胸鼠与食虫目臭鼩鼱是多种蚤的寄主。 展开更多
关键词 鼠蚤种属 季节消长调查
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