Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Co-occurrence spectrum of high-frequency keywords in rehabilitation robot field. The cross represents keywords; the larger the cross, the thicker the cross, the higher the frequency of keywords; the line refers to the connection between keywords; the thicker the line, the closer the connection.
