% arara: pdflatex
% arara: biber
% arara: pdflatex
% arara: pdflatex
\documentclass{article}
\usepackage{filecontents}
\usepackage[style=numeric,backend=biber]{biblatex}
\addbibresource{\jobname.bib}
\begin{filecontents}{\jobname.bib}
@article{key1,
author = {Author, John},
title = {Title},
journal = {A Journal},
year = 2012,
}
@article{key2,
author = {Author2, John},
title = {Title},
journal = {A Journal},
year = 2012,
}
\end{filecontents}
\DeclareFieldFormat*{note}{\textbf{#1}:~\texttt{\thefield{entrykey}}}