fetch.js

var request = require('request');
var cheerio = require('cheerio');
var Iconv = require('iconv').Iconv;
var iconv  = require('iconv-lite');

var i = 10;
var url = 'http://www.esgweb.net/Html/Yxzcpstj/'+i+'.htm';
console.log(url);
request(url, function(err, resp, body) {
    if (err)
        throw err;

    // did not work
    $ = cheerio.load(iconv.decode(body, 'gbk'));
    console.log($('body').text());

    // did not work either
    var converter = new Iconv('GB2312', 'UTF-8');
    var utf8_buffer = converter.convert((body));
    console.log(utf8_buffer.toString());
});

fetch.php

<?php

// it works!
$ch = curl_init('http://www.esgweb.net/Html/Yxzcpstj/10.htm');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$body = curl_exec($ch);
echo($body);

echo iconv('gbk', 'utf8', $body);