function buscar(){
    if (document.getElementById("q").value!="" && document.getElementById("q").value.length >= 3){
        document.getElementById("busca_topo").action="index.php?modulo=eva_busca";
        document.getElementById("busca_topo").target="_self";
        document.getElementById("busca_topo").method="post";
        document.getElementById("busca_topo").submit();
    }else{
        alert('Informe uma palavra com no minimo 3 caracteres.');
        document.getElementById("q").focus();
        return false;
    }
}