前着是指一般的人都有机会怎么怎么样
后者强调必须经过自己的一番努力从而获得的机会.这个机会是很难得的
比如
John had did his utmost to gain access to the further abord studing finally .（John通过自己的艰辛努力,最终还是取得了国外继续学习的机会）
On no account can we bilieve in having access to the summer holiday,there is no point in studying or going over our lessons.(我们决不能因为过暑假 就认为学习没有意义了！）
have access to 指有机会接近------
gain access to 强调通过努力获得机会
You have access to the house.
He study so hard that he gain access to the famous college.
have access to 指有接近某事物的机会；
gain access to 指得到了接近某事物的机会。
