搜索结果: 1-1 共查到“导航建筑物与航标工程 Frequency”相关记录1条 . 查询时间(0.134 秒)
Time and Frequency Activities at the U.S. Naval Observatory
Time Frequency Activities U.S. Naval Observatory
2009/9/3
The US Naval Observatory (USNO) has provided timing for the navy since 1830 and, in cooperation with other institutions, has also provided timing for the United States and the international community....