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教材内容选自教科版小学科学五年级上册。教学分析土壤覆盖在地球岩石圈的表面。土壤的形成是岩石的风化和生物作用的结果。整块的岩石风化成碎石,碎石继续风化就会变成越来越小的颗粒,当腐烂的动植物与岩石碎屑混在一起时,混合物就被称为土壤。在土壤中 相似文献
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邵锋星 《新课程学习(社会综合)》2011,(9)
教学分析
土壤覆盖在地球岩石圈的表面。土壤的形成是岩石的风化和生物作用的结果。整块岩石风化成碎石,碎石继续风化就会变成越来越小的颗粒,当腐烂的动植物与岩石碎屑混在一起时,混合物就被称为土壤。在土壤中我们很容易找到岩石变化留下的痕迹以及动植物的残体。 相似文献
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教材内容
选自教科版小学科学五年级上册。
教学分析
土壤覆盖在地球岩石圈的表面。土壤的形成是岩石的风化和生物作用的结果。整块的岩石风化成碎石,碎石继续风化就会变成越来越小的颗粒,当腐烂的动植物与岩石碎屑混在一起时,混合物就被称为土壤。在土壤中我们很容易找到岩石变化留下的痕迹以及动植物的残体。 相似文献
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李永春 《泉州师范学院学报》2003,21(4):43-47
从早期沉积成岩作用角度，首次在我国进行了全新世时期海、陆环境演变的对比研究．认为，青海湖湖滩岩和闽南海滩岩是我国全新世滨岸水体环境下早期沉积成岩的特殊岩石。对全新世古海岸升降、古湖平面变化和气侯干湿波动的规律研究具有标志作用和指示意义。是全新世气候环境事件的真实记录．并由此总结出青海湖与闽南海岸带全新世时期气候波动与环境演变的基本特征． 相似文献
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全新世中国北方气候变化及环境特征 总被引：1，自引：0，他引：1
中国地形地貌复杂，又处在具有复杂时空变率的东亚季风控制范围内，这使得不同的研究工作者在一些问题上存在意见分歧，比较统一的意见是：中国全新世始于约10．5kaB．P．；在约9～8kaB．P．左右为一段降温期；7～4kaB．P．为一段温暖期，通常称之为全新世大暖期；大约3kaB．P．左右开始降温，至近代才又升温；约1300aA．D．左右进入小冰期，到1850aA．D．左右结束。其间又有几次比较明显的温度振荡．1850aA．D．至今为温度的上升期，对于气候变动的驱动因素，不同的学者看法不一；从长时间尺度看，太阳辐射变化是气候变化的主要驱动力，本文对中国北方全新世气候变化与全新世大暖期的环境特征进行了阐述，对研究全球变化有重要的参考价值。 相似文献
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贵州在晚二叠世时期形成的大量泥炭，因年代久远，现已大部分深变质成煤。可作为泥炭利用的是近地表煤层经风化后所形成的含有机质丰富的风化物。本文对该风化物在贵州的分布进行研究。 相似文献
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《实验室研究与探索》2015,(7):7-11
以内蒙古自治区毛乌素沙漠东南缘萨拉乌苏河流域米浪沟湾剖面MGS1层段为例,对不同沉积相的重矿物组成进行分析,并探讨这些沉积相气候代用指标对于全新世气候变化的指示作用。结果显示:MGS1层段重矿物以绿帘石、石榴石、辉石、角闪石、钛铁矿、褐铁矿为主,各种沉积相均以较稳定矿物为含量最高,极稳定矿物和稳定矿物在河流相、湖沼相和古土壤含量较高,而较稳定矿物和不稳定矿物则在沙丘砂中含量较高,各种沉积相矿物组成基本一致,说明该地区不同沉积相的矿物来源基本一致。不同沉积相的重矿物风化系数呈波状变化,风化系数高代表了寒冷干旱的环境。重矿物矿物风化系数的变化均能够表现出萨拉乌苏河流域气候的多次变动:18D沉积环境较为干旱寒冷,形成古流动沙丘砂;17FL的河流相、13LS的湖沼相的沉积气候为温暖湿润;10D和2D两层古流动沙丘体现干旱寒冷的环境;1S的古土壤沉积时气候又为温暖。 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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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 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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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
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Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F. 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