apocalypse1 (26)in #cn • 3 months ago圆珠笔的发展历程简单的圆珠笔涉及到的物理原理可不少，它的内部其核心部件是笔尖的金属球，这个直径约1毫米的小球通常由不锈钢、钨合金等材料制成，表面经过精密抛光能在笔尖内腔中自如滚动。…apocalypse1 (26)in #cn • 4 months agoHow to make yourself betterFirst of all, we have to learn self-discipline and defeat procrastination. Daily Goals: Make goals for yourself in…
