have a look 的用法和动词look的用法相似.look是一个不及物动词,如果后面跟宾语的时候,要加介词at,后面没有宾语的时候就不用介词.I have a beautiful picture.Please have a look(at it).
have a look看一下Can I have a look?have a look at ...后边要加名词Can I have a look at the book?