五、词组 as yet （到目前为止）和 just yet （就在此刻）常用于否定句中
1. They have not made such an advanced computer as yet.
他们目前尚未制造出这样一种先进的计算机.
2. No one has as yet been able to produce the absolute zero of temperature.
还没有人能产生绝对零度.
3. It will not happen just yet.
此事一时尚不至于发生.