SciWheel allows for a quick and easy way to export references, be it a single one, a chosen set, or your whole library. Select the sources you want to export by checking the box beside them. To select all available references in your library or displayed on the current page, check the box in the header row.
Once the desired entries are selected, you can download them via the export button, which is also found in the header row.
Choose Export as... in the following context menu to reach the export interface. Make sure to select the BibTex file format before you download the bib-file.
More information on uploading bib files to SciFlow are available here.