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实际研究中，不可能逐一计数某个种群的个体总数，如何测定某物种的种群密度呢？常用的是取样调查法，即计数种群的一小部分，估计整个种群的密度。要测定某地的某种动物的种群密度，常用的取样调查法是标志重捕法。 相似文献
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珍稀濒危植物华顶杜鹃种群结构与分布格局的研究 总被引：1，自引：0，他引：1
研究华顶杜鹃(Rhododendron huadingense)种群的高度结构、径级结构和年龄结构；应用聚集度指标、Iwao方程和Taylor幂法则模型等测定方法分析了该种群的空间分布格局。结果表明，华顶杜鹃的株数随基径级的增加而逐渐减少；高度级和年龄级结构近似正态分布；空间分布格局为聚集分布。 相似文献
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调查了尚湖枝角类的种类组成和生物多样性，研究了尚湖枝角类春季空间格局分布。采用Iwao聚集格局回归分析法、数理统计分析和一元线性正态相关回归分析，结果发现尚湖六个采样点间枝角类的种群密度差异极显著，其群落多样性指数与空间分布有相关性。枝角类种群的空间分布格局理论上属于聚集型负二项分布。 相似文献
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应用4种聚集度指标和Iwao法、Taylor幂法则研究了桃树上山楂叶螨种群数量动态和空间格局。结果表明：在桃树上,山楂叶螨既可作聚集分布,也可作均匀分布;6月中旬至7月下旬山楂叶螨呈聚集分布;8月上旬至8月中旬呈均匀分布;8月下旬呈聚集分布;9月上旬至9月下旬呈均匀分布,表现为聚集→扩散→再聚集→再扩散的趋势;山楂叶螨在桃树上的为害时间较长,在6月下旬出现为害高峰。 相似文献
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研究华顶杜鹃 (Rhododendronhuadingense)种群的高度结构、径级结构和年龄结构 ;应用聚集度指标、Iwao方程和Taylor幂法则模型等测定方法分析了该种群的空间分布格局 结果表明 ,华顶杜鹃的株数随基径级的增加而逐渐减少 ;高度级和年龄级结构近似正态分布 ;空间分布格局为聚集分布 相似文献
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不同封育时间蒙古栎林主要乔木种群分布格局的分析 总被引：1，自引：0，他引：1
应用理论拟合、聚集强度指数分析方法对不同封育时间蒙古栎林样地内的主要乔木种群进行研究，结果表明：蒙古栎、黄榆种群均为聚集型分布；蒙古栎和黄榆种群的聚集强度在不同封育时间内表现不同的变化．总体上看种群聚集强度均呈下降趋势．在封育初期，黄榆种群比蒙古栎种群的聚集强度更大，随着封育时间的延长，黄榆种群的聚集强度下降，呈扩散趋势． 相似文献
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刘军 《新课程导学(上)》2013,(2):81+52
种群密度是种群最基本的数量特征,在农林害虫的监测和预报、渔业上捕捞强度的确定、生态环境的保护等方面,都需要测定种群的密度。高中生物教材介绍了如何运用样方法和标志重捕法调查种群密度。一、动物——标志重捕法标志重捕法是指在被调查种群的生存环境中捕获一部分个体,将这些个体标志后再放回原来的环境,经过一段时 相似文献
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种群密度是种群最基本的数量特征，而种群密度调查则是构建种群数量变化模型的基础。种群密度调查就是指对被调查的种群数量进行统计，可以直接计数种群的每个个体，也可以采用估算的方法。后者又可以分为样方法、标志重捕法和取样器取样法等。笔者从教学实践角度出发，对高中生物学中的植物、动物和微生物的种群密度调查问题进行归类分析与讨论。 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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唐芳 《读与写:教育教学刊》2008,5(6)
During interview with English majors, it was found that a majority of students expressed disappointment with their experience of English literature classes. Students' dislike of learning English literature appears to be the major problem of teaching English literature in China. Reader response approach is a good way to solve this problem. In this paper, I explain the rationale behind the reader response approach, such as its origin, definition, features, assumptions, and strategies. Then I illustrate how reader response approach works as a teaching strategy by presenting several teaching models. At last I evaluate its usefuiness for teachers and present the advantages of reader response approach in Chinese context. 相似文献