首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   245篇
  免费   16篇
  国内免费   2篇
财政金融   9篇
工业经济   22篇
计划管理   74篇
经济学   45篇
综合类   18篇
运输经济   1篇
旅游经济   2篇
贸易经济   16篇
农业经济   51篇
经济概况   25篇
  2023年   2篇
  2022年   3篇
  2021年   7篇
  2020年   6篇
  2019年   4篇
  2018年   5篇
  2017年   3篇
  2016年   6篇
  2015年   9篇
  2014年   19篇
  2013年   16篇
  2012年   20篇
  2011年   22篇
  2010年   18篇
  2009年   13篇
  2008年   19篇
  2007年   22篇
  2006年   20篇
  2005年   8篇
  2004年   7篇
  2003年   10篇
  2002年   12篇
  2001年   2篇
  2000年   2篇
  1999年   5篇
  1998年   1篇
  1997年   1篇
  1988年   1篇
排序方式: 共有263条查询结果,搜索用时 17 毫秒
71.
We explore the behavioral methodology and “revolution” in economics through the lens of medical economics. We address two questions: (1) Are mainstream economic assumptions of utility-maximization realistic approximations of people’s actual behavior? (2) Do people maximize subjective expected utility, particularly in choosing from among the available options? In doing so, we illustrate–in terms of a hypothetical experimental sample of patients with dry eye diagnosis—why and how utility in pharmacoeconomic assessments might be valued differently by patients when subjective psychological, social, cognitive, and emotional factors are considered. While experimentally-observed or surveyed behavior yields stated (rather than revealed) preferences, behaviorism offers a robust toolset in understanding drug, medical device, and treatment-related decisions compared to the optimizing calculus assumed by mainstream economists. It might also do so more perilously than economists have previously understood, in light of the intractable uncertainties, information asymmetries, insulated third-party agents, entry barriers, and externalities that characterize healthcare. Behavioral work has been carried out in many sub-fields of economics. Only recently has it been extended to healthcare. This offers medical economists both the challenge and opportunity of balancing efficiency presumptions with relatively autonomous patient choices, notwithstanding their predictable, yet seemingly consistent, irrationality. Despite its comparative youth and limitations, the scientific contributions of behaviorism are secure and its future in medical economics appears to be promising.  相似文献   
72.
目前,饮用水水源污染已成为全球范围的主要环境问题之一,而常规水处理工艺已经难以应对当前严重的水体微污染问题.通过对常规启动的固定化生物活性碳(IBAC)、非常规启动的固定化生物活性碳(IBAC新)和普通活性碳(GAC)对TOC、UV254、浊度、氨氮、亚硝酸盐氮等指标的处理效果的比较,得出IBAC无论在净化效果和运行稳定程度上都优于另两个碳柱.  相似文献   
73.
生物医药CRO产业是目前生物医药领域发展最迅速和最有前景的细分行业之一,其发展具有重要的战略意义.文章提出国内生物医药CRO产业在发展中应引入创业投资,并对其必要性进行了探讨和分析,最后就国内生物医药CRO产业创业投资的发展提出相关建议.  相似文献   
74.
谢氏丙酸杆菌发酵废液中生物抑菌物质的研究   总被引:1,自引:1,他引:0       下载免费PDF全文
卢楠  朱文华 《河北工业科技》2012,29(3):138-140,145
对生产维生素B12的谢氏丙酸杆菌发酵废液中是否存在生物抑菌物质,其性质、抑菌作用大小及抗菌谱进行了研究。研究表明,谢氏丙酸杆菌的发酵液针对检验菌的抑菌效果明显优于化学防腐剂且抑菌谱较广,可以抑制一些革兰氏阳性菌、阴性菌及真菌,其中主要抑菌成分为等电点在2.0附近的蛋白类物质、丙酸氨、乙酸氨。  相似文献   
75.
刘伟 《价值工程》2010,29(16):125-126
当今的水处理技术中生物处理法已成为水污染控制的主要方法,尤其是现代生物技术将成为水污染控制领域重点开发和应用的技术手段。本文介绍了现代生物技术的内容与特点,着重综述了现代生物技术在废水生物处理、生物修复以及微生物水处理剂等方面的研究与应用状况,在此基础上提出今后现代生物技术在水污染控制领域中的研究方向。  相似文献   
76.
77.
Botrytis bunch rot is a disease that causes loss of yield and quality in many fruit and vegetable crops in temperate climates worldwide. The rot is caused by the fungus Botrytis cinerea, a saprophytic necrotroph. In grapes, the presence of the fungus can reduce yield, taint wine and increase its sensitivity to oxidation. In the current work, inter-row phacelia and ryegrass were mulched in situ in winter 2005 and compared with a bare ground control. The mulches were applied under 10-year-old Chardonnay vines in a 10-replicate randomized block design in New Zealand. Functional soil biological activity increased by 1.5–4.5 times in the two cover crop treatments compared with the control, an effect related to elevated soil moisture in these treatments. This increase in soil moisture and a higher rate of soil biological activity increased vine debris degradation, reduced B. cinerea primary inoculum on the debris and decreased B. cinerea severity at flowering (December 2005) and harvest (April 2006). These results show the potential of mulched cover crops to enhance soil ecosystem services, reduce variable costs and improve the sustainability of viticulture and potentially other agricultural systems, in temperate climates worldwide.  相似文献   
78.
Wild European rabbits are serious agricultural and environmental pests in Australia; myxoma virus and rabbit haemorrhagic disease virus have been used as biocontrol agents to reduce impacts. We review the literature on changes in rabbit numbers together with associated reports on the economic benefits from controlling rabbits on agricultural production. By using loss–expenditure frontier models in with and without biocontrol scenarios, it is conservatively estimated that biological control of rabbits produced a benefit of A$70 billion (2011 A$ terms) for agricultural industries over the last 60 years. The consequences for ongoing rabbit control and research investment are discussed.  相似文献   
79.
Soil biota, ecosystem services and land productivity   总被引:6,自引:0,他引:6  
The soil environment is likely the most complex biological community. Soil organisms are extremely diverse and contribute to a wide range of ecosystem services that are essential to the sustainable function of natural and managed ecosystems. The soil organism community can have direct and indirect impacts on land productivity. Direct impacts are those where specific organisms affect crop yield immediately. Indirect effects include those provided by soil organisms participating in carbon and nutrient cycles, soil structure modification and food web interactions that generate ecosystem services that ultimately affect productivity. Recognizing the great biological and functional diversity in the soil and the complexity of ecological interactions it becomes necessary to focus in this paper on soil biota that have a strong linkage to functions which underpin ‘soil based’ ecosystem services. Selected organisms from different functional groups (i.e. microsymbionts, decomposers, elemental transformers, soil ecosystem engineers, soil-borne pest and diseases, and microregulators) are used to illustrate the linkages of soil biota and ecosystem services essential to life on earth as well as with those associated with the provision of goods and the regulation of ecosystem processes. These services are not only essential to ecosystem function but also a critical resource for the sustainable management of agricultural ecosystems. Research opportunities and gaps related to methodological, experimental and conceptual approaches that may be helpful to address the challenge of linking soil biodiversity and function to the provision of ecosystem services and land productivity are discussed. These include: 1) integration of spatial variability research in soil ecology and a focus on ‘hot spots’ of biological activity, 2) using a selective functional group approach to study soil biota and function, 3) combining new and existing methodological approaches that link selected soil organisms, the temporal and spatial dynamics of their function, and their contribution to the provision of selected ‘soil based' ecosystem services, 4) using understanding about hierarchical relationships to manage soil biota and function in cropping systems, 5) using local knowledge about plants as indicators of soil quality, remote sensing and GIS technologies, and plant-soil biota interactions to help understand the impacts of soil biota at landscape scale, and 6) developing land quality monitoring systems that inform land users about their land's ecosystem service performance, improve capacities to predict and adapt to environmental changes, and support policy and decision-making.  相似文献   
80.
机械加工行业含油废水的治理一直是困扰企业环保工作的难题,以济南柴油机股份有限公司中水处理站建设和运行为例,根据污水处理的现有条件,并针对生产工艺产生废水的具体特点,同时参考国内外污水生物处理工艺的发展情况,进行方案比较,选出采用"活性滤料生物滤池"的实施处理工艺这一最佳方案,有效杜绝了厂区所排的废水对环境的污染,实现了社会和企业的双赢.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号