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【目的】 蝗灾突发性强,传统地面调查及生物学模型方法在时间、空间上不能满足精准防控的需求,且对历史数据依赖度高,利用高分辨率遥感数据监测蝗虫栖息生境的变化,从而实现蝗灾及时、快速监测,对治蝗防蝗具有重要意义。【方法】 文章以埃及南部蝗灾常发区为研究区,基于Sentinel-2卫星数据和地面气象数据、土地利用数据、行政区划数据等,监测植被生长季植被指数及植被覆盖度变化,实现埃及地区蝗虫发生地、发生程度的快速评估。【结果】 2019年6—7月,埃及南部植被覆盖区蝗灾受灾面积比例约为12%,中度及重度以上面积不超6%,整体受灾不严重。【结论】 不依赖于历史数据,从短期植被覆盖度变化入手,可以动态监测蝗灾变化,总体时效性较强、效果较好。 相似文献
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分析了上海市1998~2008年信息产业增加值的统计测度,计算出了各年信息产业对上海经济增长的贡献度.然后.利用计量软件和模型,检验了信息产业增加值和经济总量增长的相关性,并由此推导出上海信息产业的发展对经济增长的影响系数.结果表明,信息产业对上海市的经济增长起到了很大的推动作用,其增加值占总量的比重居各产业之首.上海信息产业增加值和经济增长之间具有极强的相关性,对经济的弹性系数为0.6. 相似文献
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通过分析中国25个水稻主产省区21年(1982-2002年)主要品种的亲缘关系和遗传构成,研究国外稻种资源,特别是国际水稻所与日本稻种资源对中国水稻遗传贡献的时空变化及对中国水稻生产的经济影响.结果表明,国外稻种资源对中国水稻单产起到促进作用.国际水稻所遗传贡献率每增加1%,中国水稻单产将提高21%;日本稻种资源遗传贡献每增加1%,水稻单产将提高20%;其他国家的遗传贡献每增加1%,中国水稻单产将提高16%.政府应支持和鼓励研究人员大量引进国外稻种资源,加强对该种质的研究、开发与利用,更好地为中国水稻生产发展提供资源储备. 相似文献
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R B Hey 《Science (New York, N.Y.)》1974,184(140):1001-1003
The Puerto Rican lizard Anolis cristatellus behaviorally regulates body temperature in an open habitat but passively tolerates lower and more variable temperatures in an adjacent forest where basking sites are few and distant. Thermoregulation may be adaptive only when costs resulting from associated losses of time and energy are low. 相似文献
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Identification of general properties of evolutionary radiations has been hindered by the lack of a general statistical and phylogenetic approach applicable across diverse taxa. We present a comparative analytical framework for examining phylogenetic patterns of diversification and morphological disparity with data from four iguanian-lizard taxa that exhibit substantially different patterns of evolution. Taxa whose diversification occurred disproportionately early in their evolutionary history partition more of their morphological disparity among, rather than within, subclades. This inverse relationship between timing of diversification and morphological disparity within subclades may be a general feature that transcends the historically contingent properties of different evolutionary radiations. 相似文献
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WAKSMAN SA 《Science (New York, N.Y.)》1955,121(3147):580-581
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《Computers and Electronics in Agriculture》2009,68(1-2):80-84
Cattle behavior is potentially a valuable indicator of health and well-being; however, natural movement patterns can be influenced by the presence of a human observer. A remote system could augment the ability of researchers, and eventually cattle producers, to monitor changes in cattle behavior. Constant video surveillance allows non-invasive behavior monitoring, but logging the movement patterns on individual animals over long periods of time is often cost prohibitive and labor intensive. Accelerometers record three-dimensional movement and could potentially be used to remotely monitor cattle behavior. These devices collect data based on pre-defined recording intervals, called epochs. Our objectives were to (1) determine if accelerometers can accurately document cattle behavior and (2) identify differences in classification accuracy among accelerometer epoch settings. Video-recorded observations and accelerometer data were collected from 15 crossbred beef calves and used to generate classification trees that predict behavior based on accelerometer data. Postural orientations were classified as lying or standing, while dynamic activities were classified as walking or a transition between activities. Video analysis was treated as the gold standard and logistic regression models were used to determine classification accuracy related to each activity and epoch setting. Classification of lying and standing activities by accelerometer illustrated excellent agreement with video (99.2% and 98.0% respectively); while walking classification accuracy was significantly (P < 0.01) lower (67.8%). Classification agreement was higher in the 3 s (98.1%) and 5 s (97.7%) epochs compared to the 10 s (85.4%) epoch. Overall, we found the accelerometers provided an accurate, remote measure of cattle behavior over the trial period, but that classification accuracy was affected by the specific behavior monitored and the reporting interval (epoch). 相似文献
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进入《SCI》的海洋与水产学科期刊投稿指引 总被引:1,自引:1,他引:0
谢轶茵 《农业图书情报学刊》2005,17(8):162-166
通过分析SCI的评价功能、选刊原则和期刊收录情况,为海洋与水产学科的科研人员提供向SCI源期刊投稿的指引。 相似文献
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JB Losos TR Jackman A Larson K Queiroz L Rodriguez-Schettino 《Science (New York, N.Y.)》1998,279(5359):2115-2118
The vagaries of history lead to the prediction that repeated instances of evolutionary diversification will lead to disparate outcomes even if starting conditions are similar. We tested this proposition by examining the evolutionary radiation of Anolis lizards on the four islands of the Greater Antilles. Morphometric analyses indicate that the same set of habitat specialists, termed ecomorphs, occurs on all four islands. Although these similar assemblages could result from a single evolutionary origin of each ecomorph, followed by dispersal or vicariance, phylogenetic analysis indicates that the ecomorphs originated independently on each island. Thus, adaptive radiation in similar environments can overcome historical contingencies to produce strikingly similar evolutionary outcomes. 相似文献
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贵州农村劳动力流动对经济增长的贡献研究 总被引:1,自引:0,他引:1
通过分析农村劳动力流动对经济增长的影响机理,明确了农村劳动力流动对经济增长的影响渠道,结合贵州农村劳动力流动的特点,研究了贵州农村劳动力流动对经济增长的贡献.结果表明,农村劳动力流动通过提高社会劳动生产率、推进工业化与城镇化进程、促进农民增收等多种机制和渠道对经济增长发挥作用.贵州农村劳动力流动具有主要流向省外从事第二产业、文化程度低、年轻化趋势等特点,其结果是劳动力流动产生的经济增长效应主要作用到了经济发达地区流入地,占比例较大的向省外流动对于贵州省经济增长的促进作用是比较有限的,占比不大的省内产业间流动对贵州省区域经济增长的促进作用则更为明显.在此基础上,从产业结构调整、政府抓劳动力输出、教育等方面提出了政策建议. 相似文献
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台商农业投资对福建漳州农业发展的贡献 总被引:1,自引:0,他引:1
以漳州1986~2006年农业增加值面板数据为基础,分析漳州市台商农业投资对区域农业发展的贡献,同时通过对台商座谈访问所获得的信息进一步分析台商投资过程的障碍因素,为进一步加强漳州投资环境建设、提高闽台农业合作水平提供借鉴与参考。 相似文献
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Casellas R Shih TA Kleinewietfeld M Rakonjac J Nemazee D Rajewsky K Nussenzweig MC 《Science (New York, N.Y.)》2001,291(5508):1541-1544
Receptor editing, clonal deletion, and anergy are the mechanisms by which B cells maintain tolerance to self antigens. To determine the extent to which receptor editing shapes the normal antibody repertoire, we generated an immunoglobulin kappa polymorphism that facilitates the detection of editing of immunoglobulin light chains in vivo. We found that B cells are targeted for editing during a 2-hour delay in development at the pre-BII cell stage, and that about 25% of all antibody molecules are produced by gene replacement. These results suggest that receptor editing represents a major force in shaping the antibody repertoire. 相似文献
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《江西农业学报》2017,(5)
基于卫星遥感数据及统计数据实现城郊分类的方法,利用赤壁、通城的1960~2014年及1979~2014年两个时段气温观测数据(OBS)以及美国国家环境预测中心(NCEP)和大气研究中心(NCAR)1979~2014年NCEP/NCAR再分析资料,采用UMR方法(Urban Minus Rural)和OMR方法(Observation Minus Reanalysis)计算了城市化对咸宁地区温度变化的影响。研究结果表明:1979~2014年与1960~2014年相比,咸宁地区城郊站气温观测数据(OBS)中呈显著增温趋势的是春、夏、秋及年的平均最低气温、平均最高气温、平均气温观测数据,城郊站冬季平均气温、平均最高气温增温趋势变小,UMR方法计算城市化对冬季平均最高气温贡献率从26%上升至55%。本文应用UMR方法与OMR方法计算的春、秋、年平均气温城市化贡献率基本一致,特别是冬季平均气温(OMR方法)、冬季平均最高气温(UMR方法)增暖影响均非常明显,但UMR方法表明城市化进程对夏季气温增暖影响在逐渐减弱,OMR方法下城市化对夏季平均气温增暖为负值。 相似文献
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Contribution of small glaciers to global sea level 总被引:1,自引:0,他引:1
Meier MF 《Science (New York, N.Y.)》1984,226(4681):1418-1421
Observed long-term changes in glacier volume and hydrometeorological mass balance models yield data on the transfer of water from glaciers, excluding those in Greenland and Antarctica, to the oceans. The average observed volume change for the period 1900 to 1961 is scaled to a global average by use of the seasonal amplitude of the mass balance. These data are used to calibrate the models to estimate the changing contribution of glaciers to sea level for the period 1884 to 1975. Although the error band is large, these glaciers appear to account for a third to half of observed rise in sea level, approximately that fraction not explained by thermal expansion of the ocean. 相似文献
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为定量研究资源型城市城镇化水平及其对中国城镇化发展的贡献性,以全国126个地级市(仅限大陆地区)资源型城市为研究对象,分析改革开放以来资源型城市城镇化发展的基本情况,并籍此为基础研究资源型城市城镇化发展对我国城镇化发展的贡献。结果表明:1)四大区域资源型城市城镇化水平发展不平衡,东北地区城镇化率始终保持领先,但增长幅度最小,东部地区城镇化率增长最快,各地区年均增长率呈下降趋势,增速放缓;2)地级市资源型城市城镇化发展对我国城镇化发展的贡献度为0.48~0.90,其中0.79%资源型城市城镇化对我国城镇化贡献度为中,40.48%资源型城市城镇化对中国城镇化贡献度较高,58.73%资源型城市城镇化对我国城镇化贡献度高;3)类型上,均有超过各自总量50%的非金属、金属、煤炭和油气型资源型城市城镇化对我国城镇化的贡献度高,而森工型资源型城市城镇化对我国城镇化贡献度高的城市数量不到其总量的1/3;空间上,东和中部地区资源型城市城镇化对我国城镇化发展贡献度大于东北地区和西部地区。资源型城市城镇化推动了我国城镇化发展,但资源型城市的不同类型和区位,对我国城镇化的贡献度有差异。 相似文献
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《江西农业学报》2022,(5)
基于卫星遥感数据及统计数据实现城郊分类的方法,利用赤壁、通城的19602014年及19792014年及19792014年两个时段气温观测数据(OBS)以及美国国家环境预测中心(NCEP)和大气研究中心(NCAR)19792014年两个时段气温观测数据(OBS)以及美国国家环境预测中心(NCEP)和大气研究中心(NCAR)19792014年NCEP/NCAR再分析资料,采用UMR方法(Urban Minus Rural)和OMR方法(Observation Minus Reanalysis)计算了城市化对咸宁地区温度变化的影响。研究结果表明:19792014年NCEP/NCAR再分析资料,采用UMR方法(Urban Minus Rural)和OMR方法(Observation Minus Reanalysis)计算了城市化对咸宁地区温度变化的影响。研究结果表明:19792014年与19602014年与19602014年相比,咸宁地区城郊站气温观测数据(OBS)中呈显著增温趋势的是春、夏、秋及年的平均最低气温、平均最高气温、平均气温观测数据,城郊站冬季平均气温、平均最高气温增温趋势变小,UMR方法计算城市化对冬季平均最高气温贡献率从26%上升至55%。本文应用UMR方法与OMR方法计算的春、秋、年平均气温城市化贡献率基本一致,特别是冬季平均气温(OMR方法)、冬季平均最高气温(UMR方法)增暖影响均非常明显,但UMR方法表明城市化进程对夏季气温增暖影响在逐渐减弱,OMR方法下城市化对夏季平均气温增暖为负值。 相似文献