It is well known that的意思是“众所周知”。
well可以替换为：commonly，generally，widely，always，also等。
比如：
It is well known that bamboo shoots are a panda's staple diet.
竹笋是熊猫的主要食物，这是人所共知的。
It is well known that natural resources are scarce.
众所周知，自然资源是稀缺的。
It is well known that when gas is cooled at a constant pressure its volume decreases.众所周知，当气体在定压下冷却时，它的体积减小。It is well known that caffeine is a stimulant.众所周知，咖啡是一种兴奋剂。
It is well known that China has many beautiful places.众所周知，中国有许多风景优美的地方。
It's commonly known that certain diseases are linked with occupations like lung disease in coalminers.
众所周知，某些疾病与职业有关，如煤矿工人易患肺病。
It is generally known that the overseas Chinese are a hardworking lot.
众所周知华侨是刻苦耐劳的。
It is widely known that talking with your mouth full is not polite.
大家都知道，满嘴食物时讲话是不礼貌的。
It is widely known that water is the most popular drink in the world.
众所周知,水是世界上最受欢迎的饮料。
It is widely known that CFCs can damage the ozone layer.
众所周知氯氟烃会破坏臭氧层。
It's always been known that key figures in the government do very well for themselves.
众所周知政府中的要员都很会保全自己的利益。
It's also known that baby girls usually talk at an earlier age than baby boys do.
众所周知,女婴说话的年龄通常比男婴早。
