# 牙齒的外層是琺瑯質。它是人體最堅硬的物質,但僅形成薄薄一層,而且受損後無法更新。——《身體》
×
Sign in
Email
Password
Forgot password
or
By clicking below, you agree to our
terms of service
.
Sign in via Facebook
Sign in via Twitter
Sign in via GitHub
Sign in via Dropbox
Sign in with Wallet
Wallet (
)
Connect another wallet
New to HackMD?
Sign up