by oneself 与oneself的区别：
by oneself=alone, 强调“一个人”、“单独”。
oneself 强调“亲自”、“自己”。
by oneself
1、One is firmly established by oneself.
卓然自立。
2、The infirmity that felling is so by oneself with need to be depended on!
感觉自己是那么的虚弱和需要依靠！
3、It's more satisfying to do the job by oneself.
独自一人做这项工作更让人感到满足。
4、I really hope that can know the languages of all countries by oneself.
我真希望自己能懂所有国家的语言。
5、Visitors can drive by oneself and have.
游人可自驾车而上。
oneself
1、One must apply oneself to the present and keep one's eyes firmly fixed on one's future goals
人们必须立足现在，目光锁定未来目标。
2、The historic feeling of the town makes it a pleasant place to base oneself for summer vacations
该镇的历史气息让它成为人们夏季度假的好去处。
3、It is a very rewarding exercise to work this out oneself
独自解决这个问题是一次受益匪浅的锻炼。
4、It is better to die oneself than to kill.
宁可自亡，不可行凶。
5、To work one must have time to oneself.
一个人要工作就必须有属于自己的时间。