The best input here will strongly depend on your your overall setup and the desired outcome.
Generally it is a bad idea to add too much markup commands to fields, as formatting should be up to the style and markup can be problematic for sorting. But here it seems not totally crazy to add some language switching markup at the end of the field (which is unlikely to matter for sorting).
\documentclass[german,english]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{csquotes}
\usepackage[style=authoryear, backend=biber, autolang=hyphen]{biblatex}
\begin{filecontents}{\jobname.bib}
@incollection{doe2000,
title = {Die numerische Strömungsmechanik
\foreignlanguage{english}{[Computational Fluid Dynamics]}},
author = {J. Doe},
booktitle = {Internationaler Mathematikerkongress
\foreignlanguage{english}{[International Congress of Mathematicians]}},
date = {2000},
langid = {german},
}
\end{filecontents}
\addbibresource{\jobname.bib}
\addbibresource{biblatex-examples.bib}
\begin{document}
\cite{doe2000}
\printbibliography
\end{document}
![Doe, J. (2000). “Die numerische Strömungsmechanik [Computational Fluid Dynamics]”. In: Internationaler Mathematikerkongress [International Congress of Mathematicians].](https://i.stack.imgur.com/MiODv.png)
For a fully multilingual bibliography with the possibility to translate certain fields, you'll probably have to wait until the biblatex
multiscript development branch makes it into the released version. See https://github.com/plk/biblatex/issues/416 for more details and an available test version.
In the meantime you can do some translating with field annotations.
\documentclass[ngerman,english]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{csquotes}
\usepackage[style=authoryear, backend=biber]{biblatex}
% expand the first argument of \foreignlanguage
% needs a modern TeX engine with \expanded primitive
\newcommand*{\foreignlanguageE}[1]{\foreignlanguage{\expanded{#1}}}
\newcommand*{\foreignlangbyannotation}[2][\currentfield]{%
\hasfieldannotation[#1][lang]
{\foreignlanguageE{\csuse{abx@annotation@literal@field@#1@lang}}{#2}}
{#2}}
\newcommand*{\printtranslation}[1][\currentfield]{%
\hasfieldannotation[#1][translation]
{\addspace \mkbibbrackets{\getfieldannotation[#1][translation]}}
{}}
\DeclareFieldFormat{title}{%
\mkbibemph{%
\foreignlangbyannotation[title]{#1}%
\printtranslation[title]}}
\DeclareFieldFormat
[article,inbook,incollection,inproceedings,patent,thesis,unpublished]
{title}{%
\mkbibquote{%
\foreignlangbyannotation[title]{#1}%
\printtranslation[title]\isdot}}
\DeclareFieldFormat
[suppbook,suppcollection,suppperiodical]
{title}{%
\foreignlangbyannotation[title]{#1}%
\printtranslation[title]}
\DeclareFieldFormat{booktitle}{%
\mkbibemph{%
\foreignlangbyannotation[booktitle]{#1}%
\printtranslation[booktitle]}}
\begin{filecontents}{\jobname.bib}
@incollection{doe2000,
title = {Die numerische Strömungsmechanik},
title+an:lang = {="ngerman"},
title+an:translation = {="Computational Fluid Dynamics"},
author = {J. Doe},
booktitle = {Internationaler Mathematikerkongress},
booktitle+an:lang = {="ngerman"},
booktitle+an:translation = {="International Congress of Mathematicians"},
date = {2000},
}
\end{filecontents}
\addbibresource{\jobname.bib}
\addbibresource{biblatex-examples.bib}
\begin{document}
\cite{doe2000}
\printbibliography
\end{document}
![Doe, J. (2000). “Die numerische Strömungsmechanik [Computational Fluid Dynamics]”. In: Internationaler Mathematikerkongress [International Congress of Mathematicians].](https://i.stack.imgur.com/3bP20.png)
I have shown a similar approach on TeXwelt: https://texwelt.de/fragen/24268/biblatexbiber-deutscher-autorenname-eines-bibliographie-eintrags-englischer-rest
\foreignlanguage
call or some such to switch the language. (\foreignlanguage
and other macros are problematic at the beginning of fields because of sorting, but the further back they appear the less likely they are to matter.) A conceptually nicer solution may use data annotations (one annotation would be the translation and a second annotation could be the language of the translation that would be used for\foreignlanguage
). ... – moewe Sep 9 '20 at 7:28biblatex
would be of interest here. It is still under development and I don't think it is ready for an official release any time soon, you can find out more about it at github.com/plk/biblatex/issues/416 (there is a test version available). – moewe Sep 9 '20 at 7:30