根據中華民國科學技術統計要覽的統計資料顯示，在各產業分類中，我們可以發現一個共同的特徵，即廠商不一定會持續進行研發投資。在研發投資的相關研究中，已有許多文獻從各方面探討可能影響廠商研發投資的原因，但卻欠缺較為完善的分析。有鑑於此，本文將建立一個結合產品具有差異性及多種技術吸收能力函數變化的一般化模型，並藉此探討在數量競爭下，廠商如何決定均衡研發投資量及均衡數量等議題。本文的主要結論有以下幾點：（1）由於產品異質性的存在，我們得到D'Aspremont and Jacquemin（1988）一文所無法談及的結果，我們指出當產品差異性程度相對較小時，外溢效果對於廠商研發投資的影響為正的（即正的外溢效果）。（2）與Grunfeld（2003）的推論不同，我們指出只要產品差異性夠大，不管市場規模與技術吸收能力的大小，引入學習效果一定會增加廠商的研發投資。
According to the data proposed by Indicators of Science and Technology, we observe a common feature between industries. That is, the firm does not invest R&D investment continuously. In the literature, there are many researches which explain why the firm invests R&D investment. However, there is no rather complete and systematic analysis. Therefore, in this paper, I propose a general model combining product differentiation and various absorptive capacity settings to analyze how the firm determines R&D investment and quantity in equilibrium under Cournot competition. We found that the spillover effect motivates the firm to increases its R&D level if the product differention is small enough. On the other hand, if the product differention is relatively large, the learning effects of own R&D would necessarily drive up the incentive to invest in R&D.
