Oretical and empirical research on the patent maintenance 并列题名:Oretical and empirical research on the patent maintenance Theoretical and empirical research on teacher learning Theoretical and empirical research on the financing problem of CB Theoretical and empirical research on criminal trail Theoretical and empirical research on the formation of tea price in China Oretical and empirical research on intergenerational mobility in China Theoretical and empirical research on regional energy-saving potential theoretical and empirical research based on the perspective of county theoretical and empirical research of frontier minority areas