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近20年黄河三角洲典型地区农村居民点景观格局 总被引：39，自引：2，他引：39
以1985年、1995年土地利用类型专题图和2003年TM影像作为信息源,结合野外实地调查,应用景观生态学的原理和定量分析方法,对黄河三角洲近20年来农村居民点的景观格局进行了研究,结果表明:①近20年来农村居民点景观格局发生了很大的变化,总的趋势是农村居民点在规模、数量、占用土地面积上是增加的,在空间分布上则呈现集中、密集的趋势,在形状上没有很大的变化,呈现出形状的不规则发展状态;②农村居民点景观格局表现出一定的空间差异,农村居民点的规模、数量、分布的密集程度、占用土地多少等,在农业自然条件较好、开发历史悠久的南部山前倾斜平原区均大于农业自然条件较差、开发历史短暂的现代黄河三角洲地区;③农村居民点景观格局最初与农业自然条件、开发历史密切相关,在其后的变化过程中,较多的受到经济发展、国家政策、人类活动、城市发展等的影响. 相似文献
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黄河三角洲和辽河三角洲湿地资源的比较研究 总被引：9，自引：0，他引：9
在利用遥感、地理信息系统、地球定位系统技术摸清了黄河三角洲和辽河三角洲湿地资源底数的基础上,通过对比两个地区在湿地组成、分布、景观生态等方面特点,探索了两地湿地资源的相似性和差异性,进而找出了环渤海三角洲湿地资源在利用和保护中存在的问题,为进一步研究其景 相似文献
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盐城海岸带土地利用变化的生态环境效应研究 总被引：29，自引：3，他引：29
海岸带是全球环境变化最为敏感的地区之一,其土地利用变化可引起多种资源与生态过程的改变.随着人口的增加以及经济的发展,盐城海岸带土地利用变化不断加剧,耕地和水域是其变化的2个核心.文章分析了该区土地利用及其变化对土壤环境、水环境以及生物多样性的生态效应,分析表明,滩涂在合理农业土地利用方式下可使土壤达到淋盐增肥的效果;入海河道污染负荷成倍增加,居民工矿用地扩展是导致盐城海岸带水环境质量下降的主要原因;因滩涂开发利用使生境压力增大、景观破碎化程度增加,威胁盐城海岸带生物多样性. 相似文献
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中国海岸带土地利用遥感分类系统研究 总被引：3，自引：0，他引：3
土地利用分类是土地利用数据建立和土地利用变化研究的前提。鉴于我国海岸带土地利用多样性显著而分类系统研究相对不足的现实,本文简要论述国内外海岸带土地利用分类系统的研究进展、适用的遥感数据类型和制图精度,并从陆海耦合的角度出发回顾国内滨海湿地分类系统的研究成果。在此基础上,提出中国海岸带土地利用遥感分类系统优化方案,包含8个一级类型和24个二级类型,较全面地涵盖了全国海岸带的土地资源类型,并从海岸带区域的特征出发,强调了湿地资源的细分;应用该分类系统,基于Landsat TM影像建立解译标志,并对2010年中国海岸带区域土地利用进行遥感制图,表明该分类系统具有较强的可行性。本研究可为全国尺度海岸带土地资源遥感调查、土地利用管理与规划、海岸带综合管理等研究工作提供参考。 相似文献
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干旱区绿洲土地利用景观空间格局动态变化研究——以渭干河—库车河三角洲绿洲为例 总被引：4，自引：0，他引：4
渭干河—库车河三角洲绿洲地处世界第二大沙漠塔克拉玛干沙漠的北缘，该绿洲现已成为新疆主要的农业区和棉花基地。但随着经济的快速发展，土地资源开发强度开始加大。本研究利用1989年和2001年的遥感影像数据，借助RS和GIS技术，运用景观生态学原理，通过计算多样性指数、优势度指数、分离度指数、均匀度指数、破碎度指数等指标，对渭干河—库车河三角洲绿洲的景观格局及土地利用变化进行动态分析，得出：多样性指数从1.304降低到1.190，优势度指数从0.305升高到0.419，均匀度指数从0.8104降低到0.7396，破碎度指数从0.0177升高到0.0225，并揭示出土地利用类型三增两减(盐碱地、水体、红柳增加，绿洲、荒地减少)的变化特征。同时，利用SPSS软件对土地利用变化的驱动机制进行了分析，结果表明：人口，经济，政策因子仍然是占主导地位的。 相似文献
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黄河是中华文明最主要的发源地,是中华民族的母亲河。2019年9月18日,习近平总书记在郑州主持召开黄河流域生态保护和高质量发展座谈会并发表重要讲话,作出了加强生态保护、推进高质量发展的重大战略部署。黄河流域最下游的三角洲地区具有良好的农业开发条件,但其高质量发展依然面临多方面的挑战。中国科学院在黄河三角洲具有良好的科研基础,前瞻性部署了科研基地建设和启动了一批科研项目,取得了有显示度的科研成果。在长期研究的基础上,围绕黄河三角洲生态保护和高质量发展的战略目标,进一步提出了转变开发思路,生态学原理和高新技术有效结合,走盐碱地适应性开发、盐碱地高效精致开发和现代化产业开发的道路,探索黄河三角洲盐碱地农业高效、高质、高值发展新模式。通过探索农业科技创新的新机制,激活科技创新能力和服务能力,为黄河三角洲农业高质量发展突破一批关键技术,提出"中科院方案",建立"中科院样板"。 相似文献
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海岸带城镇空间扩展情景模拟及其生态风险评价 总被引：4，自引：0，他引：4
海岸带城镇扩展及土地利用变化在很大程度上影响着海岸带生态安全。本文以滨海城市-烟台市为例,基于1990年-2009年间的遥感监测历史数据,将城市扩展动态模拟方法与区域生态风险评价方法相结合,模拟和评估三种海岸带政策管理预案条件下烟台市区2010年-2040年间的城镇扩展与土地利用变化过程,以及城镇扩展导致的海岸带资源损失和区域生态风险空间差异性。结果表明：烟台市区未来城镇化过程加速,开发区、莱山-牟平一带区域生态风险明显加大;若不加约束将有更多的耕地资源和近岸海域被侵占;鼓励海岸带开发利用与适度围填海的城镇发展政策,加速了岸线资源的损失,使得海岸带区域生态风险增大,需要采取强有力的海岸带保护和围填海建设监管措施,降低高强度开发给海岸带地区带来的生态风险。 相似文献
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全球气候变化及人类活动加剧等背景下,我国海岸带区域发展遭受显著影响,生态脆弱性异常突出,面临诸多严峻挑战。目前,海岸带区域相对独立发展的盐碱地农业、滩涂养殖和海洋牧场,已无法满足现代农业的发展要求。亟待查明陆海连通性的影响机制和调控途径,采用新设施和新工程技术,建立基于生态系统管理理念的海岸带生态农牧场新模式。文章以我国海岸带区域发展的典型和缩影——黄河三角洲为例,分析了海岸带资源、环境现状及存在的问题;基于海岸带区域盐碱地开发与海洋牧场产业发展现状与需求,论述了海岸带生态农牧场的建设理念、建设内容、科学问题、关键技术和发展途径,以期为我国海岸带保护与持续利用提供参考。 相似文献
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Marjorie Armstrong-Stassen Margaret Landstrom Ramona Lumpkin 《The Information Society》1998,14(2):153-164
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors. 相似文献
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A joint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology his co-workers from Norway US Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of the National Academy of Sciences on September .…… 《中国科学院院刊(英文版)》2008,22(1):6-7
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007. 相似文献
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Caroline Haythornthwaite 《The Information Society》2001,17(3):211-226
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction. 相似文献
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A research group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol-a chemical found in the skins of red grapes in red wine-can improve the sensitivity of mice to the hormone insulin according to a report in the October issue of Cell Metabolism.…… 《中国科学院院刊(英文版)》2008,22(1):14-15
Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said. 相似文献
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Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies. 相似文献
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Puay Tang 《The Information Society》1998,14(1):19-31
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means. 相似文献
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Milton Mueller 《The Information Society》2001,17(3):151-163
Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP. 相似文献
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Prof. Raymond C.K. Chen a neuropsychologist with the CAS Institute of Psychology has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.…… 《中国科学院院刊(英文版)》2008,22(1):15-15
Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology. 相似文献
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Active biological molecules functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery disease diagnosis therapy new nanodevice construction.…… 《中国科学院院刊(英文版)》2008,22(1):22-22
Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction. 相似文献
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《中国科学院院刊(英文版)》2014,(3)
<正>In Xishuangbanna,one of China’s most biodiverse regions,landscape has changed dramatically during the past three decades due to the conversion of tropical rainforest to rubber plantations.In steep areas,terraces are often constructed before planting rubber trees,which causes two important changes in the soil:the destabilization of soil in the bench terraces and the increased vulnerability of unvegetated riser faces to erosion.Few studies have documented the nature and intensity of erosion on bench terraces.Prof.LIU Wenjie and his colleagues from the Xishuangbanna Tropical Botanical Garden(XTBG)conducted a study in Menglun County(21°5′39″N,101°15′55″E),Xishuangbanna to evaluate the influence 相似文献