小孢子壁形成时开始在绒毡层内切线壁出现的球状体到花粉粒成熟时仍有一部分附着于花粉粒表面。
The ubisch bodies which appeared on the inner tangential wall of the tapetum at the time of microspore wall formation are partially remain on the surface of matured pollen grain.
在射影几何的范畴内，全面地论述了两二次曲线的公有点和公切线的图解问题。
This paper deals with the graphics of the intersections and common tangents of two conics according to projective geometry .
基于小角X射线散射理论，利用逐级切线法和材料分形理论中的散射强度法，分别计算PAN基炭纤维内微孔大小、体积分数及微孔表面分形维数。
Based on SAXS theory and fractal theory, we obtain the calculating method and calculating formulas of the pore size, pore volume percentage and the fractal of pore surface in PAN - based carbon fiber.
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