'hash' url rewrite in .htaccess

The # can be added in the substitution URL with the NE flag. Check:

• This Apache link that describes specifically how to redirect anchors.

• This W3C Protocols link and this one.

• This answer in SO is pretty complete.

• Another answer in SO.

• Another answer in SO (mine).

So, you may try this:

Options +FollowSymlinks -MultiViews
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_URI}  !articles\.html      [NC]
RewriteCond %{REQUEST_URI}  ^/articles/([^/]+)/? [NC]
RewriteRule .*       /articles.html#%1           [R,NE,L]

Redirects

http://example.com/articles/parameter

To

http://example.com/articles.html#parameter

String articles is assumed to be fixed while parameter is assumed to be variable.

No, it's not possible. The URL fragment (everything from # on) not even gets sent to the server.

Maybe you want to consider a JavaScript based solution, where the actual content will be loaded via AJAX dependent on the fragment. You will find some useful information about this method here: What's the shebang/hashbang (#!) in Facebook and new Twitter URLs for?