我有两组dataframe数据：

日数据df1
datetime
2008-06-03    24643.0
2008-06-04    24924.0
2008-06-05    24356.0
2008-06-06    24612.0
2008-06-07    24944.0
               ...  
2020-03-24     9595.0
2020-03-25     9730.0
2020-03-26     9900.0
2020-03-27     9865.0
2020-03-28     9740.0


分钟数据df2

datetime
2008-06-02 10:08:00    24643
2008-06-02 10:09:00    24643
2008-06-02 10:10:00    24643
2008-06-02 10:11:00    24643
2008-06-02 10:12:00    24643
                       ...  
2020-03-27 14:55:00     9740
2020-03-27 14:56:00     9740
2020-03-27 14:57:00     9740
2020-03-27 14:58:00     9740
2020-03-27 14:59:00     9740

我想处理成:

datetime
2008-06-02 14:55:00    nan
2008-06-02 14:56:00    nan
2008-06-02 14:57:00    nan
2008-06-02 14:58:00    nan
2008-06-02 14:59:00    24643
                       ...  
2020-03-27 14:55:00     nan
2020-03-27 14:56:00     nan
2020-03-27 14:57:00     nan
2020-03-27 14:58:00     nan
2020-03-27 14:59:00     9740

请教一下我们该怎么处理
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FROM 112.45.97.*