How to change speed of a smooth scroll? [closed]

问题:

I can 't change the speed of my smotth scroll (I already tried to change the value 1000 at the end of the following code) Could you please help me?

 $(document).ready(function() {
    $('ul li:last').css('margin-right', '0');
            $("ul").corner('bottom', '18px');
            $('ul li a').click(function (){
                    $('.current').removeClass('current');
                    $(this).addClass('current');
            });
        $('a[href*=#]').click(function() {
        if (location.pathname.replace(/^\//,'') == this.pathname.replace(/^\//,'')
                && location.hostname == this.hostname) {
                        var $target = $(this.hash);
                        $target = $target.length && $target || $('[name=' + this.hash.slice(1) +']');
                        if ($target.length) {
                                var targetOffset = $target.offset().top;
                                $('html,body').animate({scrollTop: targetOffset}, 1000);
                                return false;
                        }
                }
        });

});