如何在R中导出df as.character？

How do I export a data frame completely as.character in r? I have digits that need to be treated as text in large dataframes, and I'm using write.csv, but even though I imported digits into r as characters, they are exporting as numbers (not surrounded by"" when viewed in notepad) and are occasionally rewritten as, e.g., 1e-04 (for a small decimal value). This is for data munging, and I need stuff to stay as formatted (once formatted). Shouldn't that be possible with some form of "as.character" or similar?How do I export a data frame completely as.char