scrapy request发生重定向问题

from scrapy.spider import CrawlSpider
from scrapy.selector import Selector
from scrapy.http import Request

class Spider(CrawlSpider):
name = 'wordSpider'
NUM = 14220485
start_urls = [
"http://baike.baidu.com/view/1.htm"
]
fi = open('e:/word.txt', 'w')
cnt = 2

def parse(self,response):
    selector = Selector(response)
    word = selector.xpath('body/div[@class="body-wrapper"]/div[@class="content-wrapper"]/div[@class="content"]/div[@class="main-content"]/dl/dd/h1/text()').extract_first()
    #word = selector.xpath('body/div[@id="J-lemma"]/div[@class="body-wrapper"]/div[@class="card-part"]/span[@class="lemma-title"]/text()').extract()
    self.fi.write(word + '\t' + 'n')
    if self.cnt <= self.NUM:
        wurl = "http://baike.baidu.com/view/%s.htm" % self.cnt
        self.cnt += 1
        yield Request(url=wurl, meta={}, callback=self.parse)

这是我的爬虫源码，如何阻止301/302重定向，要抓取的是百度所有词条，但是总会发生重定向导致无法获得想要的网页