The ieeetr bibliography style is set not to typeset the contents of the number field of an entry of type @article.
As @yo' has already pointed out, you also need to fix the spelling of the first author's surname. I suggest you use {\AA}str{\"o}m. For more on how to input accented characters in bibliographies, see the posting How to write “ä” and other umlauts and accented letters in bibliography?
While you're fixing up the entry, you should also change the value of the month field from {jan} to jan. What's the difference, you may ask? The latter is recognized by BibTeX as a predefined string variable that evaluates to "Jan.", whereas the former will just be rendered as the string constant "jan".

\documentclass{article}
\usepackage{filecontents}
\begin{filecontents}{abcxyz.bib}
@article{Astrm2014,
doi = {10.1016/j.automatica.2013.10.012},
url = {http://dx.doi.org/10.1016/j.automatica.2013.10.012},
year = {2014},
month = jan,
publisher = {Elsevier},
volume = {50},
number = {1},
pages = {3--43},
author = {Karl J. {\AA}str{\"o}m and P. R. Kumar},
title = {Control: A perspective},
journal = {Automatica}
}
\end{filecontents}
\usepackage{cite}
\bibliographystyle{ieeetr}
\begin{document}
\nocite{*}
\bibliography{abcxyz}
\end{document}
\r{A}seems corrupted, maybe{\AA}str\"{o}mwould work better? – yo' Feb 05 '15 at 14:31{\r{A}}str\"{o}mgoes the same way, your way is simpler. In fact, in all published IEEE paper,no.is included. – wayne Feb 05 '15 at 14:35\bibliographystyle{IEEEtran}, which is the official style from IEEE? – egreg Feb 05 '15 at 14:44