从脚注中的@onlinesource 中删除年份、括号和点

Question

这是我的 MWE：

% !TEX encoding = UTF-8 Unicode
% !BIB TS-program = biber

\documentclass[a4paper,12pt]{article}

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[english,german]{babel}
\usepackage{csquotes}


\usepackage[citestyle=verbose-ibid,bibstyle=authoryear,sorting=nyt,backend=biber,]{biblatex}

\urlstyle{rm}

\usepackage{filecontents}

\begin{filecontents}{literatur.bib}
    @online{blk,
      url = {http://www.blk-bonn.de/papers/forum-bildung/band06.pdf},
      date-added = {2014-02-09 12:34:08 +0000},
      date-modified = {2014-02-09 13:32:07 +0000},
          urldate = {2014-02-04}
    }

@article{test1,
    Author = {Shen Ain and Brian W. Kernighan},
    Date-Modified = {2014-02-04 20:18:03 +0000},
    Journal = {Operations Research},
    Title = {An Effective Heuristic Algorithm for the Travelling-Salesman Problem},
    Volume = {21},
    Year = {1973}}
\end{filecontents}

\addbibresource{literatur.bib}

\begin{document}

Here is a cite for online \footcite{blk}

And here is a cite for article \footcite{test1}

\end{document}

这给了我：

现在，我删除 URL 前面的“URL：”：

\DeclareFieldFormat{url}{\url{#1}}

并将日期网址的文本从“(Besucht am xx.xx.xxx)”更改为“aus dem Internet entnommen am”：

\DeclareFieldFormat{urldate}{aus dem Internet entnommen am #1}

我现在有：

现在，我想删除年份、年份周围的括号和点仅有的来自‘@online’，但我不知道如何实现这一点......