This paper first introduced current situations of agricultural enterprises using B2C e-commerce to sell agricultural products.Then,using SWOT method,it analyzed strengths,weaknesses,opportunities,and threats of Wuding...This paper first introduced current situations of agricultural enterprises using B2C e-commerce to sell agricultural products.Then,using SWOT method,it analyzed strengths,weaknesses,opportunities,and threats of Wuding strong chicken farming enterprises implementing B2C e-commerce.Finally,it came up with recommendations for Wuding strong chicken farming enterprises implementing B2C e-commerce.展开更多
Based on the threshold panel data model,this paper analyzed the nonlinear relationship between chemical fertilizer input and grain output. At the provincial level,from the perspective of average and marginal net benef...Based on the threshold panel data model,this paper analyzed the nonlinear relationship between chemical fertilizer input and grain output. At the provincial level,from the perspective of average and marginal net benefits,it compared the effects of chemical fertilizer input on farmers' income. It reached the conclusion that the chemical fertilizer input efficiency has deviated from the optimal level. Thus,only by increasing the marginal productivity of chemical fertilizers,may it be able to increase farmers' income.展开更多
Based on the theory of comparative advantage,this paper analyzes the major challenges facing the development of green economy in China's mountain regions. The results show that in the development of green economy,...Based on the theory of comparative advantage,this paper analyzes the major challenges facing the development of green economy in China's mountain regions. The results show that in the development of green economy,the mountain regions have factor endowment and development conditions with comparative advantage,but they are also facing more challenges. In the future,the mountain regions need to make favorable development measures based on their own comparative advantages from the following four aspects: at the top design level,it is necessary to ensure green development through institutional innovation; at the regional level,it is necessary to lead green development through the differentiation strategy; at the industrial level,it is necessary to support green development through transformation and innovation; at the social level,it is necessary to focus on protecting vulnerable groups and give full play to the role of women to promote sharing of green development achievements.展开更多
The recently reported Ni-catalyzed methylation–allylation of alkynes with allylic alcohols and AlMe3 reagents delivers valuable tetrasubstituted alkene units in a highly regioselective fashion.Motivated by the experi...The recently reported Ni-catalyzed methylation–allylation of alkynes with allylic alcohols and AlMe3 reagents delivers valuable tetrasubstituted alkene units in a highly regioselective fashion.Motivated by the experimental significance and the mechanistic ambiguity(e.g.the details of C–O bond activation,the function of the Lewis acid AlMe3,etc.),we conducted a detailed mechanistic study using density functional theory(DFT)calculations.The reaction was found to occur via the C–O bond activation of allylic alcohol,allylation of alkyne,transmetalation,reductive elimination and catalyst regeneration steps.AlMe3 could easily react with the allylic alcohol to form a cyclodialuminoxane species bearing two groups of Lewis acid–base interactions.In this regard,the C(allyl)–O bond is remarkably activated,resulting in a relatively facile C–O activation(compared to the typical Lewis-acid mediated reactions).In addition,the Al–Me interaction is a double-edged sword to the methylation step:the cyclodialuminoxane group functions as the methyl resource,while the full dissociation of the Al–Me interaction(via a cis-to-trans isomerization)is a requisite to fully release the methyl group.In this context,the“Me-relay”pathway involving the[Ni]–Me intermediate is found to be more plausible than all other mechanistic possibilities(such as the typical concerted Me-transfer mechanism in previous studies).展开更多
文摘This paper first introduced current situations of agricultural enterprises using B2C e-commerce to sell agricultural products.Then,using SWOT method,it analyzed strengths,weaknesses,opportunities,and threats of Wuding strong chicken farming enterprises implementing B2C e-commerce.Finally,it came up with recommendations for Wuding strong chicken farming enterprises implementing B2C e-commerce.
文摘Based on the threshold panel data model,this paper analyzed the nonlinear relationship between chemical fertilizer input and grain output. At the provincial level,from the perspective of average and marginal net benefits,it compared the effects of chemical fertilizer input on farmers' income. It reached the conclusion that the chemical fertilizer input efficiency has deviated from the optimal level. Thus,only by increasing the marginal productivity of chemical fertilizers,may it be able to increase farmers' income.
基金Supported by Innovation Project of Chinese Academy of Social SciencesMajor National Survey Project of Chinese Academy of Social Sciences
文摘Based on the theory of comparative advantage,this paper analyzes the major challenges facing the development of green economy in China's mountain regions. The results show that in the development of green economy,the mountain regions have factor endowment and development conditions with comparative advantage,but they are also facing more challenges. In the future,the mountain regions need to make favorable development measures based on their own comparative advantages from the following four aspects: at the top design level,it is necessary to ensure green development through institutional innovation; at the regional level,it is necessary to lead green development through the differentiation strategy; at the industrial level,it is necessary to support green development through transformation and innovation; at the social level,it is necessary to focus on protecting vulnerable groups and give full play to the role of women to promote sharing of green development achievements.
基金supported by the National Natural Science Foundation of China(51961135104,21732006,51821006)the National Key R&D Program of China(2017YFA0303502)Natural Science Foundation of Anhui Province(2108085J08).
文摘The recently reported Ni-catalyzed methylation–allylation of alkynes with allylic alcohols and AlMe3 reagents delivers valuable tetrasubstituted alkene units in a highly regioselective fashion.Motivated by the experimental significance and the mechanistic ambiguity(e.g.the details of C–O bond activation,the function of the Lewis acid AlMe3,etc.),we conducted a detailed mechanistic study using density functional theory(DFT)calculations.The reaction was found to occur via the C–O bond activation of allylic alcohol,allylation of alkyne,transmetalation,reductive elimination and catalyst regeneration steps.AlMe3 could easily react with the allylic alcohol to form a cyclodialuminoxane species bearing two groups of Lewis acid–base interactions.In this regard,the C(allyl)–O bond is remarkably activated,resulting in a relatively facile C–O activation(compared to the typical Lewis-acid mediated reactions).In addition,the Al–Me interaction is a double-edged sword to the methylation step:the cyclodialuminoxane group functions as the methyl resource,while the full dissociation of the Al–Me interaction(via a cis-to-trans isomerization)is a requisite to fully release the methyl group.In this context,the“Me-relay”pathway involving the[Ni]–Me intermediate is found to be more plausible than all other mechanistic possibilities(such as the typical concerted Me-transfer mechanism in previous studies).