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1.
The sustainability of smallholder agriculture in the drylands of West Africa is a topic of long-lasting concern. This paper is focused on the scientific assessment of nutrient (mis)management affecting the long-term productivity of cropland. “Nutrient mining” is seen as a major mechanism for land degradation in the region. Two models will be the focus: that tied to the rangeland-to-cropland metric and the nutrient balance model. These tools of assessment follow a long history of environmental assessment and modeling that purposefully abstracts from the heterogeneity of the same farming practices that modeling efforts seek to assess. Abstraction is always part of modeling but the form of abstraction described here ignores any detailed understanding of farming practices and in so doing, demands very little information about farming practices. In this way, models serve as both the symptom and cause of continued ignorance of farming practices by most agronomists and soil scientists working in the region. The variables used in these models will be described and how these same variables are strongly influenced by the variation of farmers’ practices will be discussed. In addition, it will be shown that needless model abstraction results in research outcomes that provide very little insights to guide land policy formulation and agricultural extension. In short, these models point to the ultimate resource limits of the regional agricultural system but provide few insights of what could be changed to reduce rates of land degradation. The paper concludes by presenting alternative approaches that through their engagement with the diverse positionalities of farmers, provides insights useful for the development of effective land policies.  相似文献   
2.
China has the second largest area of pastoral land in the world, and these lands and their peoples play a very beneficial role in the global environment. Because of China's huge population, rate of social reform, and economic development, the pastoral ecosystems are at a critical turning point. There is a conflict between national benefit and the land users (mainly herders) benefit. This paper introduces the scale of pastoral land, the history of its management institutions, past and current projects and programs, as well as the current framework of policy and law as relevant to land management. The challenges for pastoral management in terms of institutions, administration, technology and their shifting role in regional economies of scale are also analyzed. Opportunities for sustainable development in China's pastoral lands are presented. Finally, this paper highlights the available approaches for enhancing livelihoods and conserving pastoral land, including establishment of law and policy framework at the national level, redefining use rights for community management, promoting Integrated Ecosystem Management (IEM) as a basis for natural resource utilization, preserving and respecting cultural aspects of pastoral peoples, and shifting the focus from GDP generation to environmental protection.  相似文献   
3.
Soil erosion, in its various forms, is caused or aggravated by agricultural activities. Mitigation of surface erosion comprises the construction of shelterbelts, fencing, riparian buffering, and stock reduction. Mitigation of mass‐movement erosion, in turn, takes the form of spaced planting of trees to maintain a persistent, healthy, and complete ground cover. In this article, we assess the economic implications to agriculture of the adoption of mitigation alternatives for erosion control in the Waikato District, New Zealand. The Waikato District presents a spatial pattern of erosion that affects profitability of dairy, and sheep and beef enterprises. We use the Universal Soil Loss Equation and the New Zealand Empirical Erosion Model to estimate erosion figures that are then fed into an economic‐focused, nonlinear, partial equilibrium mathematical programming model of New Zealand land use. Different scenarios are constructed for surface and mass‐movement soil erosion targets ranging from 0% to 50% below baseline levels. We find that achieving surface erosion targets is more expensive than mass‐movement targets, and results in different responses in regional‐level costs, land use, enterprise net revenue, and adoption of mitigation alternatives.  相似文献   
4.
[目的]随着社会经济的高速发展,资源开发规模和强度不断扩大,土地退化的问题也逐渐显现出其弊端。[方法]文章以2003年、2006年、2009年的旅顺口区土地利用数据为基础,运用GIS软件的叠置分析,空间分析对研究区土地退化分区分级研究。通过掌握土地利用变化的数量、时空模式及变化趋势来揭示研究区在不同时期、不同资源开发强度下土地退化的时空特征。[结果]研究表明,研究区的土地退化类型在2003~2009年主要为土地污染、次生盐碱化、草地退化;荒草地和耕地面积在6年间共减少2068.12hm2,耕地土地利用动态度为-2.85%,荒草地土地利用动态度为-2.37%,建设用地土地利用动态度为2.25%,其他未利用地土地利用动态度为6.84%;在不同的研究时期和区域,土地退化的强度不同;根据分区区域面积加权计算,旅顺口区的耕地退化指数小于3,预计土地退化程度属于轻度退化,研究结果可信。[结论]旅顺口区土地退化分区分级研究为今后旅顺口区的社会经济发展战略的决策和生态环境的管理提供了科学依据。  相似文献   
5.
Recognizing the socio-economic and biophysical causes of land degradation at the national level is important for cause-targeted strategies when designing policies for combating land degradation. This study aims to identify the biophysical and socio-economic factors that significantly affect land degradation across Vietnam and to interpret the causalities underlying the effects. The dependent variables considered in the study are spatial, the extent and intensity of degradation in three land-use zones (agriculture, forest and severely degraded abandonment). The hypothesized explanatory variables are common economic and demographic drivers and bio-physical factors such as soil, terrain constraints, and neighborhood land-use structures that are often neglected in many large-scale land degradation assessments. Instead of using a single inferential statistic technique, we used multi-linear regression and binary logistic regression in a complementary manner to increase the detectability and credibility of the degradation cause analyses. The results showed agricultural production growth had strong and consistent effects on land degradation extent and intensity. Population growth, especially in rural areas, had a strong effect on the extent of overall land degradation. The importance of a neighboring forest was revealed for its ability to reduce land degradation intensity in abandoned, unproductive lands. The concrete faceting of the causal analysis for each land-use zone as social–ecological stratum allowed us to combine the defined social–ecological contexts, contemporary theories, and hypotheses in the field to clarify the causal factors of a complex phenomenon like land degradation. The study demonstrates these contemporary inferential statistics can be complementarily used to sufficiently detect and understand land degradation causes at the national level. The results suggest implications for national land management policy: internalizing land degradation costs in the farming system evaluation for payment for ecosystem services policy, restricting forest conversion, and improving extension services and education in agrarian communities.  相似文献   
6.
This paper questions the consequences of the use of electronic knowledge repositories for work and employment. Drawing on critical research suggesting that knowledge management associated with such tools presents similarities to scientific management principles, it proposes to examine the following key research question: how do employees experience the transformation of the employment relationship when a knowledge repository is introduced to the workplace? The inquiry is grounded in an exploratory qualitative case study of a knowledge management system designed to foster knowledge‐sharing in a Belgian public administration. The findings illustrate two complementary outcomes: this system resulted in employees experiencing deskilling and work degradation, and was met with resistance. Significantly, this paper considers work degradation as a reflexive phenomenon in the context studied, where knowledge‐sharing systems produced deskilling and resistance as part of a specific re‐regulation process.  相似文献   
7.
Estimating the costs and benefits of soil conservation in Europe   总被引:1,自引:0,他引:1  
Economics is about problems of choice. In erosion control, both public authorities and private land users are faced with such problems. What is the impact of erosion, both on-site and off-site, and to what extent can this impact be quantified? If we conceptualize this impact in terms of sustainability, how can we compare one type of effect against another? The former question can be answered only by natural scientists, the latter by economists and other social scientists. Weighing different aspects of sustainability requires value judgments, and economists are sometimes accused of having a jaundiced view of reality, wrongly supposing that decisions are based on rationality and denying the importance of emotion.However, let us assume that there is some mileage to be gained out of attempting to estimate the cost of erosion in an economic sense—which consists of converting the various effects into a common denominator: euros. If we can predict the impact of erosion control measures on erosion rates, we can know the benefit of these measures. The cost also needs to be calculated, not in terms of money but in terms of resources expended (which could have been used for other purposes) and in terms of possible negative impacts of erosion control (for instance, increased use of herbicides in reduced-tillage systems).There are important other considerations which economists may study. Firstly, there is the comparison of present versus future costs and benefits: how much can we sacrifice today for higher sustainability tomorrow?Secondly, there is the issue of private versus public costs and benefits: how do the goals of private land users differ from (those of?) the public good, how can this help us to predict land users’ behaviour, and what incentives would be appropriate to make them behave in such a way as to maximize the public good? Thirdly, how do we deal with uncertainty and risk?These problems loomed large in a study to support an extended impact assessment for the EU Soil Thematic Strategy, in 2005. Whereas much research has been done on erosion and its impact, much of this is on a small scale. The extent of the problem on a national, let alone a continental or a global scale, is still poorly known. The paper discusses how these problems were faced, which is not the same as saying they were resolved.  相似文献   
8.
The world economy faces two major threats: increasing environmental degradation and a growing gap between rich and poor. The root cause is that natural resources—or natural capital—is underpriced, and hence overly exploited, whereas human capital—the skills embodied in the workforce—is insufficient to meet demand. This outcome has three important consequences. First, all sectors of an economy will use too much natural resources relative to skilled labor. Second, the skilled workers throughout the economy will have higher real incomes and thus will be better off. Third, wealth inequality will increase, as the income gap between skilled and unskilled workers widens. Addressing this structural imbalance requires correcting the two underlying distortions, which are the chronic under-pricing of natural capital and the under-investment in human capital. This must be accompanied by a new suite of policies to provide improved incentives for more balanced wealth creation.  相似文献   
9.
This paper highlights the limiting factors of agricultural production in Zimbabwe and presents conservation agriculture (CA) as a potential solution to address many of these challenges. CA, based on the three principles of minimum soil disturbance, crop residue retention and crop rotations, targets low soil fertility, moisture deficits and low management standards through the use of soil-fertility-enhancing technologies (precision fertilizer application, crop rotations, sequencing and interactions), improved moisture use efficiency and higher standards of agronomic management practices. The paper also explains the role of CA in natural resource conservation as increasing productivity will reduce the land under crop production and increase the area under natural vegetation. Trends in the development of CA in the past five years and its current status in the country are explained, with the roles of different stakeholders outlined. Evidence on the impact of CA on both food security and the environment is presented. In conclusion, the paper looks at the various factors that may affect the spread of CA to different agro-ecological zones in the country.  相似文献   
10.
冯启蒙  马爱洁  李昕 《价值工程》2012,31(18):295-296
以辛酸亚锡为催化剂,丙交酯为单体,开环聚合得到聚L-乳酸(PLLA)。研究了各种因素对PLLA分子量及性能影响,包括单体的纯度、催化剂的浓度、反应温度及时间等。并产物进行了分子量及降解性能测试。结果表明,PLLA材料是热不稳定聚合物,具有良好的降解性和生物相容性。  相似文献   
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