Другой подход к добавлению круглых скобок вокруг цитат состоит в изменении определения макроса \cite
:
\documentclass{article}
\usepackage{filecontents}
\begin{filecontents*}{\jobname.bib}
@book{knuth,
author = {Knuth, Donald E.},
title = {The {\TeX} book},
date = 1984,
maintitle = {Computers \& Typesetting},
volume = {A},
publisher = {Addison-Wesley},
location = {Reading, Mass.},
langid = {english},
langidopts = {variant=american},
sortyear = {1984-1},
sorttitle = {Computers & Typesetting A},
indexsorttitle= {The TeXbook},
indextitle = {\protect\TeX book, The},
shorttitle = {\TeX book}
}
@article{einstein,
author = {Einstein, A.},
title = {Die Grundlage der allgemeinen Relativitätstheorie},
journal = {Annalen der Physik},
volume = {354},
number = {7},
doi = {10.1002/andp.19163540702},
pages = {769--822},
year = {1916}
}
\end{filecontents*}
\usepackage[backend=bibtex,style=authoryear]{biblatex}
\addbibresource{\jobname.bib}
\DeclareCiteCommand{\cite}[\mkbibparens]
{\usebibmacro{prenote}}
{\usebibmacro{citeindex}%
\printtext[bibhyperref]{\usebibmacro{cite}}}
{\multicitedelim}
{\usebibmacro{postnote}}
\DeclareCiteCommand*{\cite}[\mkbibparens]
{\usebibmacro{prenote}}
{\usebibmacro{citeindex}%
\printtext[bibhyperref]{\usebibmacro{citeyear}}}
{\multicitedelim}
{\usebibmacro{postnote}}
\begin{document}
\cite{einstein}
\printbibliography
\end{document}
![enter image description here](https://i.stack.imgur.com/4dVwa.png)