Update 'README.md'

README.md

@@ -7,4 +7,6 @@
  - 见doc文件夹
 
 ### 实验代码
- - notebooks/data_pull.ipynb
+ - notebooks/data_pull.ipynb，下载数据
+ - notebooks/data_mining.ipynb, 构建网络，PageRank和度中心性实现
+ - notebooks/learning.ipynb，实现机器学习