我必须去买些替换用的钢笔笔心。

I must go and buy some refills for my pen.

youdao

锁具使用一段时间后，会出现开启不顺畅的现象，不要往锁心内滴机油，将滑石粉或铅笔心的细屑滑入锁心内即可。

When used for a time, the lock may not be opened smoothly. Do not dip mechanical oil into the lock. Instead, slip some French chalk or pencil fines into it.

youdao

从构造上看，阑尾位于盲肠的末端，不与其他部分连结。 它有一个比铅笔心还细的开口，防止了可能携带病原菌的废物流入其中。

Structurally, the appendix is isolated from the rest of the gut, with an opening smaller than a pencil lead, protected from the fecal stream that might be carrying pathogens.

youdao