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都匀市封山育林基地内马尾松天然更新情况调查表明，马尾松在适生的更新迹地上具有强大的天然更新能力，影响更新效果较重要的环境因子是更新迹地上灌草盖度的多寡。在皆伐迹地上，每公顷保留健壮母树15～20株，在调查地区就能保证马尾松良好的天然更新。 相似文献
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The Urban Review - This work selects a political cite in which the state policy reform occurs to examine reasons and underlying ideologies for some consensus on the debates regarding the need to... 相似文献
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This study presents a novel approach to decant supernatant on a centrifugal platform. By manipulating the centrifugally induced pressure and the elastic deformation of the plastic lids in the decanting chamber, fixed amounts of the supernatant can be decanted into the detection chamber at lower rotational speeds. The experimental results showed that decanted volume is affected by the volume of deformation and the operating parameters. Factors that influence the decanting ratio are also discussed. This approach has the advantages of simple design and low manufacturing cost; further, it has no need of surface modification. It has been applied to on-disk separation of plasma from whole blood, and the results showed good stability and repeatability. 相似文献
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