get to the graph in PRISM, double click the y axis, you will get "Axes"
window, then go to the Axis tab,chosse Y Axis. Below it you get the "Gaps
and Direction" tab, click the up-side down arrow to choose "Two segments(...
.//....) to get what you want.
You can also choose other types.
And if you cancel the "Auto limits & interval" function (the tab is below "
Gaps and Direction", you can set the interval, minimum and maximum by
yourself at your desire.
Sorry can not input chinese in my lab. Hope it helps.