exist at the present time的意思|示意

However, it would take long time to realize this objective because at present the criterion of home intelligent network has not been unified and many technology problems still exist.

然而，目前家庭智能化网络的标准尚未统一，许多技术问题还有待于进一步解决，因此家庭网络化目标的实现仍然需要长期不断的努力。

Throughout most of Earth's history, glaciers did not exist, but at the present time about 10 percent of Earth's land surface is covered by glaciers.

在地球大部分的历史时期，冰川是不存在的，但是在现在，地球表面有大概10%的地方时被冰川覆盖的。

At the present time, there exist a lot of repetitive work in analysis of software reliability and safety which increase the software development cost.

目前，在软件可靠性与安全性的分析中产生很多重复性工作，增加了软件的开发成本。