I've looking round the internet for a solution to this and everyone is talking about different things or just saying does size="x" help? I've made a Plunk to illustrate my issue. On my screen I can see up to item 20 when I click the drop down. I'd like to be able to set this to show more, or at least have some control.
Gabriele Petrioli
You cannot because the select box is a system control..
See Height of an HTML select box (dropdown)
You could use a dropdown replacement widget/module..
You are add size tag like this
<select size="30">
来源：https://stackoverflow.com/questions/16788863/how-to-adjust-select-drop-down-height