排序方式： 共有35条查询结果，搜索用时 15 毫秒
21.
海岸带及海洋环境中的微塑料污染已经成为全球环境问题。我国已对一些典型河口、海湾、海岛周边海域及潮滩开展了微塑料污染的初步调查,积累了一些基础数据。但目前从基础理论、方法学及评估与控制技术等方面都远未达到环境监管的要求。因此,需要从建立和完善微塑料调查、监测与评估的方法学体系,厘清我国海洋微塑料的排放格局与污染分布规律,建立微塑料及其附着污染物的毒理学评价指标体系与参数库,形成海洋及海岸环境微塑料污染控制与管理技术体系等角度开展全面系统研究,解决现有的技术难点和关键科学问题,为我国海岸及海洋环境微塑料污染的监管与安全保障提供科学支撑。 相似文献
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基于支持向量机(SVM)的相关反馈算法在反馈过程中只利用SVM的分类器,反馈结果排序会出现一定错误, 提出一种改进的相关反馈策略,将图像的视觉特征度量函数和SVM分类器函数进行线性加权,作为相关反馈中的相似性度量准则. 实验表明,改进策略能够优化遥感图像检索排序结果,提高检索的精度. 相似文献
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基于SLEUTH模型的沈阳-抚顺都市区城市规划 总被引：2，自引：0，他引：2
利用SLEUTH模型,在3种规划预案下研究沈阳-抚顺都市区城市规划。结果表明,低生态保护的城市增长预案导致了城市快速扩张和农田、林地等其他景观类型面积迅速减少.严格的生态保护规划预案虽然能很好地保持聚集的城市增长格局,减少对其他景观的侵占,但限制了城市增长速度,与区域经济发展现状相矛盾.如果扩散的城市增长格局能得到进一步的控制,适当生态保护的城市增长预案将是沈阳-抚顺都市区未来发展的推荐预案. 相似文献
24.
通过慢性暴露实验研究了菲律宾蛤仔在锌(Zn2+),铅(Pb2+)单一胁迫及联合胁迫下,消化腺和鳃内富集Zn2+和Pb2+及其金属硫蛋白水平随Zn2+、Pb2+暴露浓度的变化规律.结果表明, Zn2+50μg/L、Pb2+25μg/L联合胁迫时,消化腺和鳃内重金属的富集低于Zn2+、Pb2+单一胁迫,表现为拮抗作用;MT含量随着Zn2+、Pb2+暴露质量浓度变化而变化,比较发现消化腺中MT含量随Pb2+暴露质量浓度的变化最显著(p<0.01). 相似文献
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由于海岸带地理、地质条件的特殊性,我国重点海岸地下水资源环境承载力脆弱。近年来,围海造陆等海岸工程加快,海岸带环境水文地质问题频发,生态环境恶化,已经严重制约我国海岸带的生态建设。文章分析了我国海岸带环境水文地质特征,研究海岸带地下水需求现状和不合理开采地下水所产生的主要地质环境问题,指出水资源短缺、海(咸)水入侵所导致的生态环境退化问题将严重制约我国海岸带的可持续发展,如何科学促进地下水资源和环境的协调发展,已成为我国海岸带综合管理的一项重要战略任务。 相似文献
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长期以来,东部沿海区域在我国经济社会快速发展过程中扮演了"动力引擎"的角色,与此相应,中国大陆海岸线的开发利用广泛而深刻,尤其是最近几十年来自然岸线消失和破坏的速度惊人、程度严重,围填海愈演愈烈,急剧的岸线开发和扰动过程导致了一系列的资源、环境、生态和灾害问题,对中国当前及未来的海岸带综合管理乃至沿海经济社会可持续发展形成了极为严峻的挑战。文章概述了过去近70年中国大陆海岸线开发利用的过程特征,总结了存在的问题及其对海岸带的影响,在此基础上,指出当前及未来时期中国海岸带综合管理的重点和策略,包括:加强以海岸线为重点的海岸带监测、观测和科学研究;加强自然岸线的保护力度,优化人工岸线的开发利用;开展"恢复中国的河口"行动,维持和强化河口的水文与生态连通性;以海湾为重要抓手,通过实施海湾分类管理促进大陆海岸线的保护;建立健全法律法规,推进海岸带综合管理的多部门协同和区域协同。 相似文献
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《Teaching and Teacher Education》2004,20(1):17-29
In the last 15 years, New Zealand has experienced a range of educational “reforms” driven by a neo-liberal agenda which has insisted that the education system serve the goal of enhancing the nation's economic performance and its competitive edge through the inculcation in learners of the skills requisite to the pursuit of this goal. Fuelled by a perception that the education system needed quality management and greater accountability to its clientele, a series of administrative reforms were put in place in the late 1980s and were followed by a series of radical, state-dictated curriculum and assessment reforms. The subsequent reshaping of curriculum and assessment has had a profound impact on the nature of teachers’ work and their identity as professionals. Using research undertaken in New Zealand in the later 1990s, this article examines ways in which 1990s reforms in New Zealand have worked to reconstruct the professional knowledge (including pedagogical knowledge) of secondary English teachers. It further examines the implications of these changes in teachers’ work for professional identity and discusses some of the implications of these “reforms” for pre-service teacher education. 相似文献
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《Early childhood research quarterly》2004,19(2):337-353
The central question addressed in this study was: What factors are associated with individual differences in academic motivation among first-grade students who were born to low-income adolescent mothers? Data from a 7-year longitudinal study were used to address the question. First-grade teachers assessed academic motivation for 89 children at the end of the school year. We tested a model that children’s experiences in the home prior to school entry influence the developmental trajectories of the children; experiences in the home are likely to influence the cognitive abilities children have when they enter school. More competent children are likely to be more successful on school-related tasks, which in turn, should influence level of motivation in the early elementary grades. The results of a path analysis were consistent with this model. Parenting practices and quality of the home environment during the early childhood period were predictive of children’s receptive language skills at age 4.5 years and achievement in the fall semester of first grade; achievement test scores were, in turn, predictive of academic motivation at the end of first grade. We also expected parental support for achievement after school entry to be related to individual differences in academic motivation, but this hypothesis was not supported. 相似文献
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以黄河三角洲地区为实验区域,利用实测的土壤全盐含量数据,结合中国产的中巴地球资源卫星02B(CBERS-02B)多光谱遥感影像,分别应用传统的多元线性回归模型和BP人工神经网络模型,对其进行含盐量反演建模,并对2种模型的精度进行比较.实验表明,应用BP人工神经网络建模,明显改善了反演精度;且该反演模型更适宜于高盐度区域(全盐含量>1%)土壤含盐量反演制图,具有较好的应用前景. 相似文献