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桃园套种黑牧草对土壤热状况的影响及其模拟研究 总被引:1,自引:1,他引:0
在实地试验的基础上,分析和模拟了桃园套种黑牧草对土壤热状况的影响.结果表明,在牧草种植区和自然裸露区,阴天条件下平均土壤容积热容量分别为2.54和2.53J·cm-3·C-1,平均土壤导温率分别为16.9和10.4cm2·h-1;土壤净热通量分别为136.6和167.6J·cm-2·d-1;晴天条件下分别为2.93和2.61J·cm-2·℃-1,16.3和5.8cm2·h-1,80.4和85.2J·cm-2·d-1.不同深度的土壤温度以一阶正弦波形式为主,土壤温度振幅随深度呈指数规律变化,自然裸露区的衰减系数大于牧草种植区;土壤温度位相落后随深度变化为0,4h·cm-1 相似文献
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大连汉族学生身高的研究 总被引:13,自引:2,他引:11
本文采用国际通用的人体测量方法,调查了大连城市7-17岁的1214(男601,女613)名汉族学生的身高,并利用以往的资料,研讨了大连学生身高的生长发育趋势、性差和生长突增高峰年龄。结果表明:大连汉族学生21年来身高吾逐渐增高趋势,平均每10年增长值男性为2.94cm,女性2.09cm,但近8年间在8 ̄10岁各年龄组的男女学生身高均呈负增长。在1974年-1995年的21年间,生长突增高峰年龄男性 相似文献
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双倍体酵母细胞D7经单核能为11.4MeV/u的An和U离子辐照后,测定了细胞随剂量的存活率和突变率。获得细胞对Au和U离子的失活截面分别为2.54μm2和1.92μm2。在存活率为37%的条件下,Au、U离子的RBE分别为0.28和0.19。在突变实验中,研究了DNA断链后的重组与倒位,它们对Au和U离子的截面为:8.3×10-2μm2[σm-rec(Au)],9.5×10-5μm2[σm-rec(U)]和6.1×10-4μm2[σm-rev(Au)]和3.8×10-5μm2[σm-rev(U)].最后,对所获结果进行了讨论。 相似文献
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中华鲟在成都地区池塘养殖试验报告 总被引:4,自引:0,他引:4
1993-1995年,在四川郫县省水产研究所进行了中华鲟的池塘养殖试验,基本摸清了中华鲟稚幼鱼在内塘里的生活习性及生长特点。全长约3cm的稚鱼经过113d的培育,平均全长为24cm,最大个体全长可达27cm,体重60g。幼鱼经过7个月的饲养后鱼体平均全长可达74cm,平均体重为1.9kg。继续饲养一年后,鱼体平均全长为97.5cm,体重3.3kg。最大个体全长110cm,体重5kg以上。通过两年的 相似文献
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细胞内外钙离子浓度对鲎腹神经感光器光适应的影响 总被引:4,自引:1,他引:3
用细胞内记录的方法研究了由微弱持续光刺激(6×10^6 ̄9×10^6光子/cm^2,10s引起鲎(Limlus polyphemus)腹神经光器膜电流的变化--光碰击。结果表明,在生理盐水(10mmol/LCa^2+)中光碰击的平均面积为(39.5±1.76)pC,微弱光适应(记录前2.5s加1次光闪,9×10^9光子/cm^2)使得光碰击的面积下降至(10.5±2.29)pC(n=4)。在低钙溶 相似文献
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剪切应力对毛细血管内皮细胞代谢的影响 总被引:3,自引:0,他引:3
建立的平行平板流动腔装置适用于研究血管内皮细胞代谢对剪切流场的响应。将培养的人胚肾小球血管单层内皮细胞置于剪应力分别为5×10-5N/cm2,1×10-4N/cm2和1.5×10-4N/cm2的定常层流中剪切25小时,样品中的内皮素分泌量用放射免疫法测定。结果表明,剪应力水平对内皮细胞内皮素的代谢活动有显著影响。与静态培养对照,低水平的剪应力(5×10-5N/cm2、1×10-4N/cm2)促进内皮素的分泌,而较高水平的剪应力(1.5×10-4N/cm2)抑制内皮素的分泌;剪应力对内皮素累积含量的影响比之分泌速率更大 相似文献
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解磷固氮菌剂的研制及其对小麦的增产效应 总被引:11,自引:0,他引:11
研究了固氮菌(Alcaligensfaecalis)和磷细菌(Bacillusmagatherumphosphaticum)同时存在于土壤中相互促进其生长和增强生理活性的过程。并研制出解磷固氮复合细菌肥料。用该菌肥接种小麦,产量增加10%-17.9%,平均增产13.2%,每亩增产小麦30.42kg。分析了产量构成因子,结果表明,接种的比不接种每平方米增加穗数10.1个,每穗粒子增加1.82,千粒重增加0.97g。 相似文献
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H.-R. GREGORIUS 《Biological journal of the Linnean Society. Linnean Society of London》1984,23(2-3):157-165
For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment. 相似文献
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment. 相似文献
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In this article, we systematically review Dr. Wu Lien-Teh's academic achievements and outstanding contributions in the prevention and control of the plague epidemic in northeast China and introduce the development of the earliest public health epidemic prevention system in China in order to commemorate the 140th anniversary of Dr. Wu Lien-Teh's birth. We hope that this article will provide insights into the effective prevention and control of emerging infectious diseases as well as the current worldwide pandemic of COVID-19, facilitating the improvement and development of public health systems in China and around the globe. 相似文献
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