i am a researcher in applied mathematics. I need to use mathematica full version. what edition will be useful for me and will be of less price?
Check out http://www.wolfram.com/mathematica/pricing/industry-individuals.php?desktop
My guess is that the $300 price is sufficient for your needs, unless you anticipate making a lot of use of either Wolfram Alpha or the cloud.
For professional and academic work the standard version at $2495 is the usual choice.The enterprise version adds capabilities for distributing applications, but for a much greater price. The home version license is limited to personal hobby use, and does not allow for professional or academic use.