For a field $k$, I know that $k(x_1,\cdots,x_n)/k(s_1,\cdots,s_n)$ is a finite Galois extension with Galois group $S_n$ where $s_i$ is an elementary symmetric polynomial. Thus its dimension is $n!$.
What is its base?
Edit: base -> basis
Edit2:I want an explicit example of a basis. If its proof why it is a basis is complicated then I want to see how the basis represents some concrete examples of polynomials like $x_1.$