共 6 条
[5]
Towards an open R&D system: Internal R&D investment, external knowledge acquisition and innovative performance[J] . Luca Berchicci.Research Policy . 2013 (1)
[6]
Firm Size, Market Structure, Opportunity, and the Output of Patented Inventions[J] . F. M. Scherer.The American Economic Review . 1965 (5)