LaTeX Forum

\documentclass{scrartcl}
\usepackage[style=nejm,backend=biber, sorting=none, maxnames=99]{biblatex}
\addbibresource{biblatex-examples.bib}
\DeclareFieldFormat[incollection]{booktitle}{#1\isdot}
\DeclareFieldFormat[article]{journal}{#1\isdot}
\renewcommand*{\finalnamedelim}{\addcomma \space}
\defbibheading{head}{\chapter{Literaturverzeichnis}}
\begin{document}
Zitiere Onlinequelle: \cite{ctan,markey}\par
Zitiere Buch: \cite{companion}\par
Zitiere Artikel: \cite{springer}
\printbibliography
\end{document}

\defbibenvironment{bibliography}
  {\list
    {\printtext[labelnumberwidth]{%
	 \printfield{prefixnumber}%
	 \printfield{labelnumber}}}
     {\setlength{\labelwidth}{\labelnumberwidth}%
      %\setlength{\leftmargin}{\labelwidth}% evtl
      \setlength{\leftmargin}{0pt}% evtl
      \setlength{\labelsep}{\biblabelsep}%
      \addtolength{\leftmargin}{\labelsep}%
      \setlength{\itemsep}{\bibitemsep}%
      \setlength{\itemindent}{\dimexpr\labelwidth+\labelsep}%neu
      \setlength{\parsep}{\bibparsep}}%
      \renewcommand*{\makelabel}[1]{\hss##1}}
  {\endlist}
  {\item}