英语习语：

scratch the surface 只懂皮毛，很不了解（通常和限制性副词如only, hardly等词连用）

双语例句：
You've certainly done a lot of research for your project.
你显然对你的课题做了不少研究。
It seems like a lot, but actually I've only scratched the surface.
看上去不少，但事实上我只懂一些毛皮。

These problems just scratch the surface.
这些问题只是涉及到表面。
So far, these studies only scratch the surface of human complexity.
到目前为止，这些研究所触及的还只是人类复杂性的表层。
The examples above merely scratch the surface on timeouts, which shows how ubiquitous timeouts are in any solution.
上述示例仅仅是触及了超时的表层，展示了所有解决方案中普遍存在的超时。
Never touch the lenses when they are dry.ray bans Aviator Dirt particles will scratch the surface.Never polish the lenses or rub them hard with a dry cloth.
不要触摸干的镜片.防光颗粒会划伤它的表面.不要使用干布用力去擦拭或磨擦.不要使用氨性清洁器。
Scratch the surface of the regime's propaganda, and profound discontent wells up.
在该政权表面的宣传之内，是喷涌而出的深深不满。