高γ-氨基丁酸保健茶研究进展

近年来,高 γ-氨基丁酸茶的保健功效日益引起各界的广泛关注.γ-氨基丁酸具有促进睡眠、缓解焦虑、治疗糖尿病和哮喘以及提高记忆力等多种保健作用.本文综述了高γ-氨基丁酸茶的保健作用、富集方法和γ-氨基丁酸测定方法的最新研究进展,同时指出高γ-氨基丁酸茶在开发推广中仍存在的问题,展望了其前景,以期为高γ-氨基丁酸保健茶的进...     

生物技术产业集群的动力机制及其演进——基于国外典型集群的多案例研究

在产业集群理论的总体框架下,本文以国外五个典型集群为研究对象,归纳了生物技术产业集群演化的关键动力要素,即科学研究、风险投资、传统大企业介入、政府支持、中介机构、市场需求、创新文化、相关产业支撑、龙头企业以及"龙头企业-专家型公司-科研机构"之间的良性互动。在此基础上,研究了要素的演进和集群发展的内在规律。最后,结合我国的实际情况,基于政府的视角得出若干促进我国生物园区发展的启示。     

Heterogeneous returns to chemical fertilizer at the intensive margins: Insights from Nepal

Increased fertilizer use is considered important for agricultural development in low-income countries. Promoting increased use of chemical fertilizer by lowering its price may be ineffective if demand is price inelastic. In theory, the price elasticity of demand depends on the returns to its use, but the evidence is scarce. Furthermore, while returns are often estimated for small changes in chemical fertilizer use, returns to larger changes in its use (intensive margins) are less understood. Through the inter-zonal comparisons in Nepal, we provide indicative evidence that greater returns to chemical fertilizer are associated with greater price elasticities of demand. Moreover, the evidence suggests that returns at the intensive margins, rather than returns to small changes, may largely account for inter-zonal differences in returns to chemical fertilizer within Nepal. The results suggest that better understanding the returns at the intensive margins is critical for effective agricultural inputs policies in developing countries.     

城镇化对农药、化肥施用强度的影响——基于中介效应的分析

目的 探讨城镇化对农药、化肥施用强度的影响及其作用机制。方法 文章基于文献梳理,归纳城镇化对农药、化肥施用强度的影响机理;利用2000—2018年河南省106个县的面板数据,分别探讨城镇化对农药施用强度和化肥施用强度的影响;通过分析农地经营规模与居民收入水平的中介效应,探索其影响机制。结果 （1）城镇化对农药、化肥施用强度均具有显著的负向影响;（2）城镇化的农地规模效应显著,城镇化有利于扩大农地经营规模,从而有利于降低农药、化肥施用强度;（3）城镇化的收入效应显著,居民收入水平对农药、化肥施用强度的影响呈“倒U型”变化趋势,超过1/3的县已跨过农药施用强度的拐点,全部县均已跨过化肥施用强度的拐点;（4）城镇化对农药、化肥施用强度较低的县的影响更大。结论 适度推进新型城镇化建设有利于促进农药、化肥减量;鼓励农地适度规模经营,可以充分发挥城镇化的农地规模效应,降低农药、化肥施用强度;持续增加居民收入,同时促进居民选择环境友好型食物、减少食物浪费,可以从需求侧助推农药、化肥减量。     

三甲基醋酸的开发和应用

本文概述了三甲基醋酸的工业制法和发展趋势。介绍了它的主要用途和国内市场情况。     

乙醛酸的生产应用及市场前景分析

本文介绍了国内外乙醛酸的生产、应用概况,并对乙醛酸的市场前景作了分析.     

国内外醋酸生产应用及市场分析

对国内外醋酸生产技术发展动向和市场供需作了综述。认为醋酸作为重要有机原料品种之一，在我国发展前景看好。借鉴国外发展策略，应淘汰包括乙烯-乙醛法在内的落后工艺，发展先进的甲醇羰基合成工艺，同时还应重视规模效应，在有条件的地区建300-500kt／a规模的装置是可取的。     

阀控铅酸蓄电池寿命的影响因素及维护措施

阀控铅酸蓄电池在电信行业广泛应用以后，蓄电池寿命问题得到了广泛重视。着重分析各种内部原因与外部环境对阀控铅酸蓄电池寿命的影响，并且从提高电池使用寿命角度，对阀控铅酸蓄电池维护措施进行分析与讨论，在实践中提高了阀控铅酸蓄电池的寿命。     

Bt Cotton in India: Field Trial Results and Economic Projections

The performance of Bt cotton in India is analyzed on the basis of field trial data from 2001. The amounts of pesticides applied during the trials were reduced to one-third of what was used in conventional cotton, while––under severe pest pressure––yield gains were 80%. Productivity effects are modeled econometrically with a damage-control specification. The first approval for the commercial cultivation of Bt hybrids was given in 2002. By 2005, the technology is expected to cover one-quarter of total Indian cotton area. Medium-term projections show sizeable welfare gains for the overall economy, with farmers being the main beneficiaries.