Omitting fields in Bibliography

One way to proceed is to create a modified version of the file plainnat.bst, in which the functions that format and print fields such as doi and isbn are reduced to stubs that do nothing:

• Find the file plainnat.bst in your TeX distribution. Make a copy of this file and call it, say, myplainnat.bst. (Don't edit an original file of the TeX distribution directly.)

• Open myplainnat.bst in your favorite text editor, and search for the function called format.doi. (In my copy of the file, it starts on line 292.)

• In this function, replace the line

  { new.block "\doi{" doi * "}" * }
  

  with

  { "" }
  

  In short, tell BibTeX to do nothing even if the field doi is non-empty. (You could go further and replace the function's entire body with { " " }. However, if you ever choose to undo some of these edits, it may be easier to do so if you leave behind for more than that absolute minimum code snippet.)

• Repeat this procedure, as needed, for the functions format.url, format.issn, and format.isbn.

• Save the file myplainnat.bst, either in the directory where your main .tex file is located or in a directory that's searched by BibTeX. If you choose the latter option, you'll probably need to update the filename database of your TeX distribution too.

• Start using the new bibliography style via

  \bibliographystyle{myplainnat}
  

You should use biblatex with this in your preamble (remove \bibliographystyle{plainnat})

\usepackage[style=authoryear-comp,firstinits=true,citestyle=authoryear,natbib=true,backend=bibtex]{biblatex}
\renewcommand\nameyeardelim{, }
\DeclareNameAlias{sortname}{last-first}
\renewcommand*{\multinamedelim}{\addcomma\space}
\renewcommand*{\finalnamedelim}{\addcomma\space}
\setlength{\bibitemsep}{\baselineskip}
\renewbibmacro{in:}{}

Where this gives you the expected removal.

\AtEveryBibitem{%
  \clearfield{issn} % Remove issn
  \clearfield{doi} % Remove doi

  \ifentrytype{online}{}{% Remove url except for @online
    \clearfield{url}
  }
}

This is based on http://codydunne.blogspot.se/2012/01/suppressing-bibtex-fields-for-specific.html