Line plots appear blocky

I have a figure containing several (4) subplots. Each subplot contains a line plot of about 5000 data points. The measured data is smoothly varying (sinusoidal) but the lines appear "steppy" or "blocky". If I zoom in, the line become smooth. This steppy appearance carries over if I copy the plot into Word using imclipboard('copy', export_fig) . I am reluctant to filter or subsample the plotted data since I must see high-frequency noise when it appears, and I must plot the entire duration so I can't just show a subset. How can I eliminate the blocky appearance of a long time series plot?