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北京耕地流失的时空特征与驱动机制 总被引：14，自引：0，他引：14
利用1996年和2004年北京市两期土地利用图，提取各类用地的图斑，运用GIS技术和数理统计方法，分析了1996年～2004年间北京耕地流失的特点及其影响因素。结果发现：1996年～2004年北京土地利用变化中，大多数地类转换都与耕地直接有关，耕地流失是北京土地利用变化的核心问题；城镇扩展主要占用耕地，且耕地生产力高的平原地区因建设占用而流失的耕地量大；远郊山区耕地被建设占用的压力相对较小，但被生态用地占用的压力相对较大；1996年～2004年间，尽管耕地面积减少，但耕地破碎化程度却在加重；地形和交通状况对耕地的空间变化过程影响显著。本文研究表明，第三产业的快速发展是促使北京地区耕地流失的最主要的动力, 由此带来的居民生活水平提高对北京耕地变化的解释力最强，恰好与前人相关研究结论相互印证；人口快速增长、区域土地市场过度竞争、农业结构调整及退耕还林政策也是北京耕地流失的重要驱动因素。 相似文献
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耕地资源非农转化定量预测模型 总被引：3，自引：0，他引：3
社会经济发展对土地需求的增长性与土地稀缺性之间的不协调性历来是土地利用规划需要解决的问题,从经济发展的角度,合理确定区域耕地资源转化为非农建设用地的数量具有重要的价值和实际意义.本文首先给出了耕地资源非农转化的定义,即在一定的社会历史条件下,耕地被非农建设挤占的动态演变过程即为耕地非农转化,并进行了耕地资源非农转化的驱动分析.综合考虑引起耕地数量变化的3个方面:土地整理复垦、经济建设非农占用、生态退耕及自然灾毁,得出耕地的非农转化量即为综合考虑未来人口发展规模在食物安全状态下对耕地的需求量、生态安全建设中生态退耕面积、自然灾毁耕地面积与现有耕地总量、土地开发整理复垦补充耕地平衡之后剩余的耕地数量.构建了耕地非农转化定量预测模型,并以济南市为例,预测到2020年耕地资源的非农转化量为29 876.31hm2.对区域耕地资源非农转化的定性与定量分析,为协调土地利用规划与经济发展对土地的需求之间的矛盾提供了新的思路与方法. 相似文献
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社会经济发展对土地需求的增长性与土地稀缺性之间的不协调性历来是土地利用规划需要解决的问题,从经济发展的角度,合理确定区域耕地资源转化为非农建设用地的数量具有重要的价值和实际意义.本文首先给出了耕地资源非农转化的定义,即在一定的社会历史条件下,耕地被非农建设挤占的动态演变过程即为耕地非农转化,并进行了耕地资源非农转化的驱动分析.综合考虑引起耕地数量变化的3个方面:土地整理复垦、经济建设非农占用、生态退耕及自然灾毁,得出耕地的非农转化量即为综合考虑未来人口发展规模在食物安全状态下对耕地的需求量、生态安全建设中生态退耕面积、自然灾毁耕地面积与现有耕地总量、土地开发整理复垦补充耕地平衡之后剩余的耕地数量.构建了耕地非农转化定量预测模型,并以济南市为例,预测到2020年耕地资源的非农转化量为29 876.31hm2.对区域耕地资源非农转化的定性与定量分析,为协调土地利用规划与经济发展对土地的需求之间的矛盾提供了新的思路与方法. 相似文献
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改革开放以来,用地审批制度逐步成为中国土地管理的重要制度和手段之一,土地审批制度也历经了多次改革。为分析土地审批制度变化对建设占用耕地的影响,本文梳理了中国土地审批制度的改革历程,选取1995-2013年省级面板数据进行实证分析。结果表明：审批建设占用耕地规模对建设占用耕地的影响具有滞后性,全国当年审批建设占用耕地面积每增加1hm2能够显著引起当年及次年实际耕地被占用面积分别增加0.25hm2和0.36hm2,即当年建设占用耕地1hm2中约有0.25hm2由当年审批用地所致、约有0.36hm2为前一年审批用地所致、约0.4hm2为其他年份审批以及违法占地等所导致;国务院审批土地比重的增加使得建设占用耕地面积显著减少,国务院审批面积比重每增加1%约能减少耕地占用面积2351hm2;1999-2005年审批权限上收期比2006-2013年审批权限调整下放期在耕地保护的作用更为显著。建设用地审批权限的上收减缓了建设占用耕地速度,但后期的审批权限调整下放并未显著影响建设占用耕地。 相似文献
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1998年～2006年中国耕地资源的时空变化特征 总被引：17，自引：1，他引：16
根据1998年～2006年全国土地利用变更和全国耕地变化情况数据,对中国耕地资源的时空变化特征进行了分析。研究表明：①1998年～2006年间,耕地资源结构变化的区域分异明显。黄淮海平原、长江中下游平原以及东部和东南沿海这些水热条件好、优质耕地集中的区域,灌溉耕地面积减少,耕地生产力降低;②除新疆和黑龙江耕地面积净增加外,全国其它地区耕地面积均呈下降趋势。耕地变化最为剧烈的地区分布在京津塘、长江三角洲、珠江三角洲的经济快速发展区和内蒙长城沿线农牧交错带;③耕地资源增减分布的区域差异明显。耕地减少区域主要分布在黄土高原区、内蒙古及长城沿线的农牧交错带区和东部水热条件较好的平原及丘陵区;耕地增加区域呈明显的西移趋势,由此而导致耕地的整体生态条件恶化;④耕地增减变化的原因亦存在区域差异。在黄土高原区和内蒙古及长城沿线的农牧交错区,耕地减少的主要原因是生态退耕;在经济发达的东部沿海区,耕地减少的主要原因是农业结构调整和建设用地扩张。对于新增耕地而言,在西部地区,主要来自土地开发;在中东部地区,主要来自土地开发和整理;⑤建设用地占用耕地主要是由于独立工矿和村庄的扩张,其区位分布恰和我国重要的粮食生产区域相重叠。 相似文献
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跨区域财政转移制度是解决耕地保护区域非均衡的重要工具,其通过管制弱化区域和管制强化区域之间的横向财政转移,使得不同区域均能享受到国土空间优化带来的福利提升,有助于耕地保护的实施。本文初步尝试将新增费缴纳、新增费分配过程有机结合,视为横向跨区域财政转移支付,即新增费由建设用地指标多的非农发展区流向耕地保护任务重的农地保护区,并考察这种以新增费为载体的跨区域财政转移制度的耕地保护作用机理。在此基础上,本文采用中国2005—2015年间省级面板数据,通过建立动态面板计量模型和引入系统GMM估计方法进行实证检验。研究结果表明：以新增费为载体的省际横向跨区域财政转移制度有助于调动地方政府保护耕地的积极性,达到耕地保护的目的,但是其发挥的作用非常有限。进一步探讨新增费的两个主要组成部分——新增费缴纳和新增费分配的耕地保护效应大小可知,相比于新增费分配,新增费缴纳的耕地保护效果更好。本文研究结果有助于完善以新增费为载体的省际横向跨区域财政转移支付制度,促进耕地资源保护。 相似文献
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河北省耕地占用与GDP增长的脱钩分析 总被引：19，自引：5，他引：14
在经济发展过程中,大量优质耕地被占用已成为严重制约我国可持续发展的重大挑战.本文基于脱钩理论,运用经济合作与发展组织(OECD)提出的脱钩指数计算模型和Tapio等划分的脱钩状态,构建脱钩模型,计算脱钩弹性,建立脱钩程度坐标图,并以河北省为例分析各阶段脱钩状态及其原因,以期指导经济发展过程中的耕地保护问题.研究表明:1990年～1999年脱钩弹性值变化平缓,由强脱钩向复钩状态变化,建设占用耕地压力增大;2000年～2005年脱钩弹性值变化剧烈,由强脱钩向复钩状态变化,建设占用耕地压力较前一阶段急剧减小后增大;2006年～2007年脱钩弹性减小,呈现弱脱钩状态,建设占用耕地压力减小.总体来看,建设占用耕地与非农GDP产值的关系曲线呈现"M"型变化,耕地保护政策、措施实施效果明显.随着经济发展,在未来一段时期建设占有耕地与非农GDP产值关系有向复钩状态发展的趋势,建设占用耕地压力将增大,为此应加大建设占用耕地管理力度,采用节约集约利用土地的政策和措施. 相似文献
8.
1991年～2006年贵阳市土地利用变化及其驱动因素分析 总被引：2，自引：1，他引：1
以贵阳市为研究区,利用1991年、1996年、2000年、2006年4期的遥感影像资料和地形图,运用人机交互目视解译方法以及地理信息系统的空间分析和数理统计功能,获得贵阳土地利用的现状、动态度、土地利用类型转移矩阵等专题图、数据,并结合社会经济及人口数据对贵阳市土地利用的时空变化情况进行了深入分析。结果显示：①建设用地和林地的面积保持持续上升,耕地呈现持续下降,草地和未利用地面积则呈现出先减少后略有增加,水体的转移比例一直很小;②1991年～2006年间,主要的土地利用变化是耕地与建设用地、耕地与林地、未利用地与耕地之间的相互转化;③1996年～2006年间,耕地都主要转向建设用地和林地,林地主要来自耕地、草地和未利用地;④1991年～2006年间,研究区土地利用变化强度较大,总体来看,经济发展是土地利用变化的主导因素。 相似文献
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2000-2010年中国耕地变化与耕地占补平衡政策效果分析 总被引：1，自引：0，他引：1
本文基于中分辨率卫星遥感数据,深入分析了2000-2010年间中国耕地变化及其空间差异,并对中国耕地占补平衡政策的实施效果进行了评估。结果表明：10年间中国耕地面积有所减少,由2000年的1.85亿hm2,减少到2010年的1.81亿hm2,耕地减少的主要方式为耕地转为城镇建设用地。耕地变化在空间上呈现出西增东减,北增南减,东部沿海自然条件良好地区以及中部生态环境脆弱地区耕地减少,西部水资源缺乏地区耕地增加的基本格局。大部分省份没有实现耕地占补平衡基本目标,有18个省份占补平衡指数小于-50％。建设占用的耕地多适宜农业耕作,而新增耕地只有不到一半适宜农业耕作。研究时段内经济快速发展、人口增加以及城镇化等因素导致的建设用地需求快速增加,决定了东部地区耕地占补平衡很难有效实施。全国耕地总体占补平衡背后存在较为严重的生态风险,耕地增加过于依赖土地开发,对现有耕地的保护亟待加强。 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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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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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)》2008,22(1):2-3
CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing. 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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《中国科学院院刊(英文版)》2008,22(1)
With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants." 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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Leah A. Lievrouw 《The Information Society》2000,16(2):155-159
This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment. 相似文献