[Maxima] FullForm[...] in Maxima?

[Martin Schönecker]

Hello,

in Mathematica I like to use the FullForm to see the
Mathematica-internal representation of an expression.  For example,
FullForm[D[f[x],x]] would show that the internal representation is
Derivative[1][f][x], which can be used for further pattern-matching, or
other things.

Is there a similar command in Maxima to learn how it likes to represent
expressions?

Thank you,
Martin