You can update some of the settings loaded by the thebibliography
environment to a set of fixed lengths:

\documentclass{article}
\usepackage{filecontents}
\begin{filecontents*}{\jobname.bib}
@article{adk-1997,
author = {B Alziary and JP D{\'e}camps and PF Koehl},
title = {A {PDE} approach to {A}sian options: {A}nalytical and numerical evidence},
journal = {Journal of Banking \& Finance},
year = {1997},
volume = {21},
number = {5},
pages = {613-640}
}
\end{filecontents*}
\usepackage[numbers]{natbib}
\usepackage{etoolbox}
\makeatletter
\patchcmd{\thebibliography}{\c@NAT@ctr\z@}{\c@NAT@ctr\z@
\renewcommand{\makelabel}[1]{\makebox[1.2em][r]{##1\hfill}}%
\setlength{\labelwidth}{1.2em}%
\setlength{\labelsep}{.5em}%
\setlength{\leftmargin}{\dimexpr\labelwidth+\labelsep}%
}{}{}
\makeatother
\begin{document}
\nocite{*}
\bibliographystyle{apalike}
\bibliography{\jobname}
\end{document}
You can increase the two length measures 1.2em
that forms part of \makelabel
and setting \labelwidth
if you have more than 9 references.
biblatex
, but this is not apalike bib style, as far as I know: it is a numeric style.Alziary & al. 1997
, possibly between brackets, since it anauthoryear
style.