I am using this url, can anyone tell what I am doing wrong?
This is not the correct way to pass the OAuth tokens to the API. You need to construct correct Authorization HTTP headers and sign your request. Something more like:
GET https://api.twitter.com/1.1/statuses/user_timeline.json?screen_name=twitterapi
Authorization: OAuth oauth_consumer_key=\"xxxxx\", oauth_nonce=\"xxxx\", oauth_signature=\"xxxx\", oauth_signature_method=\"HMAC-SHA1\", oauth_timestamp=\"xxxx\", oauth_token=\"xxx\", oauth_version=\"1.0\"\r\n