Ok I will attempt to contribute my $0.02 to your dilemma.
I was using experts-exchange.com
Glad it's in the past ;)
I saw stackoverflow I liked its idea
Now you are in the right direction!
...allows the users to vote on a question which has not yet been resolved.
This is actually a very important feature of the sites. It allows the users to spot interesting questions. Voting on an unresolved question will signal whether or not the asker has put effort into his post. Whether sufficient research has been done and whether the asker has actually attempted to solve the issue on his own before posting it. Sure you'll get some random up/down votes thrown in there but this is the nature of a community - many people and each one with their own view on life and the world.
With regard to your second statement :
...they do not write why they give the bad or good score...
This has been discussed again and again and again here on meta. Obviously if you feel that a post is not helpful then you should downvote and if you feel the need to explain your vote - go right ahead! However users are by no means obligated to explain themselves. It is their opinion and they are entitled to it.
Please do not hesitate to post questions because you fear negative feedback - rather take that "fear" as incentive to write great posts! Do you research, prettify your post by adding appropriate links and formatting, be polite and realize that the people who are offering you assistance are not being paid to do so - they are doing it out of their free time and good will.
I think you'll agree that the site (while not 100% perfect) is pretty awesome. There are many, many, many (at least 42 ;) active users and "good" questions are usually answered very quickly. The system is not perfect by any means as I have said - there are some downfalls - for example when it comes to non-english speakers (strict language requirements). However in this specific example other users can come along and improve the post so that it can received and understood more easily by other users.