nginx reverse Proxy some url can’t be access

i have some issue for something…

i want to make some proxy pass to some url..

server {
listen 80;
location / {
    proxy_pass http://www.xxx.xxx/;
}  

}

but the problems was : when i go to some url with http://109.365.52.12/user.php?user=gigantic i was go to the url i use http://www.xxx.xxx. but i dont want it i want it still in my url..