Hello!
You can take admission in B.Com. if you are from science stream. B.Com. is open for Commerce and science students but remember that your 12th marks should be enough to take admission in the college. Try to learn some basics of Commerce from someone before you enroll in B.Com. it will minimise the discomfort you will face during the initial year of your degree.
Eligibility criteria for B.Com (GENERAL) admission is

• Commerce stream - Minimum 60% in aggregate and  55% in Accountancy
• Science stream - Minimum 60% in aggregate and 60% in mathematics

Eligibility for B.Com. (Hons.)

• Commerce Stream - Minimum 60% in aggregate and 60% in Accountancy
• Science stream - Minimum 60% in aggregate and 60% in Mathematics

If you fall under ST/SC or any other reservation some relief in cut off percentage will be provided. In case of ST/SC aggregate of almost 40% is required for all streams.
Thank you
Reply for any doubts.