Here's a way of doing this in AdventureWorks which you can apply to your own data:

WITH MEMBER [MonthsFilled]

AS COUNT(EXISTING([Measures].[Internet Order Count], [Date].[Calendar].[Month]))

MEMBER [InternetFullYearOrders]

AS IIF([MonthsFilled]=12,[Measures].[Internet Order Count], NULL)

SELECT

{[InternetFullYearOrders]} ON 0

,

NON EMPTY

{[Date].[Calendar].[Calendar Year]} ON 1

FROM

[Adventure Works]

Let me explain what it does. Firstly it does a count of the number of months that have internet orders, as we are using year in the query this is broken down by year. Then if there are fewer than 12 months that have orders in a year it does not display anything. Finally a NON EMPTY clause is used in the query to filter out non "full" years.

I hope this helps.