如何预防科学记数法？

Try format function:

> xx = 100000000000
> xx
[1] 1e+11
> format(xx, scientific=F)
[1] "100000000000"

To set the use of scientific notation in your entire R session, you can use the scipen option. From the documentation (?options):

‘scipen’: integer.  A penalty to be applied when deciding to print
numeric values in fixed or exponential notation.  Positive
values bias towards fixed and negative towards scientific
notation: fixed notation will be preferred unless it is more
than ‘scipen’ digits wider.

So in essence this value determines how likely it is that scientific notation will be triggered. So to prevent scientific notation, simply use a large positive value like 999:

options(scipen=999)