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排序方式: 共有343条查询结果,搜索用时 15 毫秒
91.
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Xu Jingwei Li Chuanrong Li Qi Zheng Li & Wang Weidong Beijing Forestry University Beijing China Shandong Acdemy of Forestry Jinan China College of Forestry Shandong Agricultural University Taian China Shandong Normal University Jinan China 《中国人口.资源与环境(英文版)》2005,3(3)
Evaluating the biodiversity of previous and current species in a forest community is an important task. Some methodological researches and effective applications have been carried out widely in the temperate upland zone. However, they lack related researches in coastal shelter forests. This paper attempts to analyze them for Jiaonan coastal forest communities from the following three aspects, the relationship between plant biodiversity structure and its environment, the nexus between biodivers… 相似文献
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温度、盐度和光照对球形棕囊藻生长和产毒的影响研究 总被引:5,自引:0,他引:5
为阐明溶血毒素的生物合成机制、正确认识和评价球形棕囊藻赤潮的危害,设计了盐度、温度、光照三因素三水平正交实验,考查了不同盐度、温度、光照条件下球形棕囊藻的生长和产毒的变化,分析了盐度、温度、光照强度对球形棕囊藻生长和产毒的影响.结果显示,温度是影响球形棕囊藻生长和产毒的显著因子,盐度和光照的影响不显著.30℃时球形棕囊藻比生长速率最大,藻细胞产毒能力最强,但所能到达的藻密度最小.在盐度为22、33、40,温度为20、25、30 ℃,光照为2000、4000、5000 lx的所有实验组合中,盐度为40、温度为30℃、光照为4000 lx时球形棕囊藻细胞产毒能力最强,盐度为40、温度为30℃、光照为5000 lx时球形棕囊藻的比生长速率最大. 相似文献
95.
本文测试分析了4种涂层织物涂层前后撕裂和顶破性能,研究表明涂层织物平均撕裂强力趋于下降,撕裂强力均匀;涂层织物因织物和薄膜的共同作用,顶破形态呈矩形变化与基布的组织结构有密切关系,涂层后顶破强力变大。 相似文献
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Multidimensional Markov chain models in geosciences were often built on multiple chains, one in each direction, and assumed
these 1-D chains to be independent of each other. Thus, unwanted transitions (i.e., transitions of multiple chains to the
same location with unequal states) inevitably occur and have to be excluded in estimating the states at unobserved locations.
This consequently may result in unreliable estimates, such as underestimation of small classes (i.e., classes with smaller
than average areas) in simulated realizations. This paper presents a single-chain-based multidimensional Markov chain model
for estimation (i.e., prediction and conditional stochastic simulation) of spatial distribution of subsurface formations with
borehole data. The model assumes that a single Markov chain moves in a lattice space, interacting with its nearest known neighbors
through different transition probability rules in different cardinal directions. The conditional probability distribution
of the Markov chain at the location to be estimated is formulated in an explicit form by following the Bayes’ Theorem and
the conditional independence of sparse data in cardinal directions. Since no unwanted transitions are involved, the model
can estimate all classes fairly. Transiogram models (i.e., 1-D continuous Markov transition probability diagrams) are used
to provide transition probability input with needed lags to generalize the model. Therefore, conditional simulation can be
conducted directly and efficiently. The model provides an alternative for heterogeneity characterization of subsurface formations.
相似文献
Weidong LiEmail: |
98.
环境监测数据的质量是否具有代表性、准确性、精密性、可比性和完整性,将直接影响到环境监测为环境管理服务的质量、环境执法的公正性和严肃性以及政府环境决策的科学性,关系到科学发展观和国民经济可持续发展战略的正确实施,本文通过"五性"来谈一下如何提高监测数据的质量,也就是通过提高环境监测数据的代表性、准确性、精密性、可比性、完整性来提高数据质量,以期对同行有所启发。 相似文献
99.
Hong Zhang Wenzhong Tang Weidong Wang Wei Yin Honglei Liu Xiaomin M Yiqi Zhou Pei Lei Dongyang Wei Litian Zhang Cao Liu Jinmiao Zha 《环境科学学报(英文版)》2021,33(6):53-68
Constructed wetlands (CWs) have been introduced to and developed in China for environmental engineering over the most prosperous three decades (1990–2020). To study the origin, development process, and future trend of CWs, this review summarized a wide range of literatures between 1990 and 2020 by Chinese authors. Firstly, the publication number over years, research highlights, and the author contributions with the most published papers in this field were conducted through bibliometric analysis. Secondly, the most principal components of CWs, substrates and macrophytes were summarized and analyzed. Thirdly, the typical application cases from traditional CWs, pond systems to combined pond-wetland systems were presented. In China, CWs were predominately distributed in the east of the so-called 'Hu Huanyong Line'. Therefore CWs were limited by the socio-economic level and climatic conditions. It is unquestionable that the overall level of China's CWs has improved significantly, and one of the most prominent features has started towards the plural pattern development. There has been a trend of large-scale or low-cost CW application in the recent years. However, lifecycle research and management are required for better strategies in the future. 相似文献
100.
抑食金球藻可产生一种抑制双壳类动物摄食的胞外多糖,导致贝类大量死亡.由于抑食金球藻个体微小、形态学鉴定困难,故在辽东湾海域鲜见其分布报道,而高通量测序技术的发展极大地推动了微型/微微型浮游植物的鉴定研究.以18S rDNA V4区作为目标基因,结合高通量测序技术,设计了微型/微微型浮游植物鉴定引物V4(F/R),并对辽东湾2014年四季海水中微型和微微型浮游植物多样性进行了检测.结果表明,辽东湾抑食金球藻春季密度(7.743×103 L-1)最高,夏季(2.094×103 L-1)、秋季(0.392×103 L-1)、冬季(0.053×103 L-1)密度逐渐下降,水温是影响该藻暴发的主要因素,也验证了渤海褐潮多暴发在春季的原因.抑食金球藻密度高值区主要分布在与河北秦皇岛交界的绥中海域,该地区与实际暴发褐潮海域相邻,验证了检测结果的可靠性.春季抑食金球藻在西南海域优势度(平均40%)最高,其密度最高达78.128×103 L-1,虽未达到警戒标准,但分布扩散较广,致灾风险较高,应引起足够的重视. 相似文献