准确识别开发区生产率优势的来源,对于开发区的效率评价和政策制定具有重要意义。本文首次从"集聚效应"和"选择效应"两个方面对开发区影响生产率的渠道进行了论证,进而运用Combes et al.(2012)的方法对开发区和非...准确识别开发区生产率优势的来源,对于开发区的效率评价和政策制定具有重要意义。本文首次从"集聚效应"和"选择效应"两个方面对开发区影响生产率的渠道进行了论证,进而运用Combes et al.(2012)的方法对开发区和非开发区的生产率分布进行了系统比较,并定量识别了开发区的"集聚效应"和"选择效应"。研究发现:(1)"集聚效应"和"选择效应"都显著提高了开发区的生产率水平;(2)平均而言,开发区企业的生产率优势主要源自"集聚效应",但是这种"集聚效应"持续期非常短,在开发区成立三年后就基本消失。由制度和政策优惠所形成"选择效应"则是开发区长期生产率优势的主要源泉;(3)民营、小规模、年轻的低效率企业从"集聚效应"中获益更大,这一方面意味着开发区有助于提高资源配置效率,另一方面也说明开发区起到了"孵化器"的作用,促进了民营中小企业的发展。展开更多
[Objective]The aim was to study heterosis of N use efficiency for grain production (NUEg) of Brassica napus L. and provide theoretical basis for breeding N-efficient cultivars. [Method]Dry matter production and N co...[Objective]The aim was to study heterosis of N use efficiency for grain production (NUEg) of Brassica napus L. and provide theoretical basis for breeding N-efficient cultivars. [Method]Dry matter production and N content of six B.napus parents (Zheshuang 3,Yangyou 7,ZJ1,Shilijia,Ningyou 14 and Huyou 16) and their F1 combinations from 6 × 6 complete diallel cross in maturity stage under two N levels were measured; heterosis of NUEg,combining ability and heritability size were analyzed and calculated. [Result]The results showed that NUEg has obvious heterosis; combining ability variance analysis indicated that NUEg was mainly controlled by additive,dominant and cytoplasmic effects; genetic variance analysis showed that additive effects and dominance effects were all significant in low nitrogen fertilizer and dominance effects were significant in high nitrogen fertilizer. [Conclusion]NUEg of B.napus has obvious heterosis.展开更多
文摘准确识别开发区生产率优势的来源,对于开发区的效率评价和政策制定具有重要意义。本文首次从"集聚效应"和"选择效应"两个方面对开发区影响生产率的渠道进行了论证,进而运用Combes et al.(2012)的方法对开发区和非开发区的生产率分布进行了系统比较,并定量识别了开发区的"集聚效应"和"选择效应"。研究发现:(1)"集聚效应"和"选择效应"都显著提高了开发区的生产率水平;(2)平均而言,开发区企业的生产率优势主要源自"集聚效应",但是这种"集聚效应"持续期非常短,在开发区成立三年后就基本消失。由制度和政策优惠所形成"选择效应"则是开发区长期生产率优势的主要源泉;(3)民营、小规模、年轻的低效率企业从"集聚效应"中获益更大,这一方面意味着开发区有助于提高资源配置效率,另一方面也说明开发区起到了"孵化器"的作用,促进了民营中小企业的发展。
基金Supported by Agricultural Science &Technology Project of Jiangsu Province(BE2008369)~~
文摘[Objective]The aim was to study heterosis of N use efficiency for grain production (NUEg) of Brassica napus L. and provide theoretical basis for breeding N-efficient cultivars. [Method]Dry matter production and N content of six B.napus parents (Zheshuang 3,Yangyou 7,ZJ1,Shilijia,Ningyou 14 and Huyou 16) and their F1 combinations from 6 × 6 complete diallel cross in maturity stage under two N levels were measured; heterosis of NUEg,combining ability and heritability size were analyzed and calculated. [Result]The results showed that NUEg has obvious heterosis; combining ability variance analysis indicated that NUEg was mainly controlled by additive,dominant and cytoplasmic effects; genetic variance analysis showed that additive effects and dominance effects were all significant in low nitrogen fertilizer and dominance effects were significant in high nitrogen fertilizer. [Conclusion]NUEg of B.napus has obvious heterosis.