A commercial model used to describe the charging of program use. As the name suggests. it is based on the idea that use is charged on the amount of a resource that is used than, say, on a subscription.
科学参考收录了60776条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。