You can split this with a regular expression.
str='68753-9.990e+000 -9.900e-002 -9.990e-003-3.330e+000';
RE=['[+-]?',... %start with an optional + or -
'[.\d]*',... %then the number itself: only digits or periods
'(e[+-]\d*)?'];%optionally followed by e with either + or - and several digits
nums=regexp(str,RE,'match')
You can even send this result to str2double to convert them to their numeric values:
str2double(nums)
