In this chart for bonds traded on NYSE
it seems a lot of bonds do not have a value for the 'Previous Close'. Considering that bonds trade in the open market like stocks, is there an online resource that shows OHLC, Last bid, Last Ask etc. i.e.a yahoo finance page for bonds. What are the websites real time bond trading prices (just like level 2 real time stock quotes)? Because the above chart does not even AAPL bond data.
EDIT: I am asking specifically for US corporate bonds