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孩提时听过龟兔赛跑的故事,长大后又听到了新龟兔赛跑的N种版本,其中一个版本很有意思。讲的是比赛中第二次赛跑时,兔子一路领先,抢先到达山顶。但在下山时很被动,老是翻着跟头往下摔,被摔得鼻青脸肿。而乌龟却缩头滚下了山坡毫发无损。可在平地时,兔子又跑到了前面,眼看离终点不远了,一条大河挡住了去路。兔子不会游泳,这时乌龟跑到了河边,[第一段] 相似文献
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河南省陆栖腹足类初报 总被引:1,自引:1,他引:0
整理自1984—1990年从河南省采集的陆栖腹足类标本,已鉴定30种,计前鳃亚纲,中腹足目Ⅰ科2属;肺螺亚纲,柄眼目12科22属。凡注有“*”者为河南省新纪录,注有“**”者为华北新纪录。标本均保存在河南师范大学、生物系。 相似文献
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当一个行业内所有的企业热衷于相互模仿,竞争便注定了沿着同一个方向没有赢利地赛跑,日本经济失败的经验如是,中国企业当引起警醒 相似文献
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研究蜗牛在农田的生活习性和生殖特性、为害特点,及重发生因素,提出采取农业防治、物理防治、化学防治相结合的综合防治对策。 相似文献
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LIU ZongXiu GU ZhaoYan WU NaiQin XU Bing 《科学通报(英文版)》2007,52(3):388-394
Carbon isotope compositions for both the carbonate shells and soft bodies (organic tissue) of living land snails collected mostly from the Loess Plateau, China have been measured. The result shows that δ 13C values range from -13.1‰ to -4.3‰ for the aragonite shell samples and from -26.8‰ to -18.0‰ for the soft body samples. Although the shells are enriched in 13C relative to the bodies averagely by 14.2(±0.8)‰, the shell δ 13Ca values are closely correlated to the body δ 13Corg values, expressed as δ 13Ca = 1.021 δ 13Corg 14.38 (R = 0.965; N = 31). This relationship indicates that δ 13Ca is primarily a function of the isotopic composition of the snail diets since previous studies have proved that the snail body is the same as their food in carbon isotope composition. In other words, carbon isotope compo-sition of the carbonate shell can be used as a proxy to estimate the dietary 13C abundance of the land snails. The data also support that the 13C enrichment of the carbonate shells results mainly from the equilibrium fractionations between the metabolic CO2, HCO3-in the hemolymph and shell aragonite, and partially from kinetic fractionations when snail shells form during their activity. 相似文献
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