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101.
More diverse, perennial cropping systems often have better natural mechanisms for keeping pests at bay. But while scientists emphasise the broad benefits of conservation in terms of effective ecosystem functioning, farmers are more interested in biodiversity for the provision of food or of services such as shade or windbreaks. Because of their limited knowledge of the role of biodiversity in plant protection, farmers sometimes unconsciously disturb natural regulatory mechanisms. Some citrus farmers in Vietnam introduced sapodilla as an intercrop to diversify their source of income, and because this fruit tree requires little care. However, this apparently worthwhile attempt to combine two valuable crops has misfired. The ecological conditions that traditionally sustained natural pest control in citrus have been disturbed, thus trapping farmers in the pesticide treadmill. The weaver ant Oecophylla smaragdina stopped protecting citrus from stinkbugs and leaf-feeding caterpillars after facing competition from the black ant Dolichoderus thoracicus, which favours sapodilla trees as a nesting habitat. To avoid similar scenarios in the future, methods for linking scientific research on ecosystem functions with farmers' own knowledge, experience and priorities are presented. Examples are given of ways in which farmers in perennial cropping systems learn, and how scientists can facilitate this learning process.  相似文献   
102.
Following Wallis and North's pioneering attempt to estimate the size of transaction costs in the United States over the period 1870 to 1970, we seek to augment this seminal study by applying their methodology to the Australian economy for the period 1911 to 1991. Broadly speaking, our results support the Wallis and North finding with comparable magnitudes and growth rates in both the private and public transaction sectors.  相似文献   
103.
Two regions are distinguished by their technological capabilities. In autarky, the advanced region accumulates more rapidly. Trade augments both regions' growth rates, but can initially worsen the uneven accumulation. The advanced region's faster growth turns the terms of trade against itself. The growth gap narrows. Yet, trade can never close that gap completely. Further decline in the advanced region's growth rate is arrested by its investment in, and technology transfer to, the backward region to augment the latter's export. Whether uneven accumulation persists depends on how successfully the backward region's indigenous capitalists adopt the more efficient `foreign' technology.  相似文献   
104.
105.
This article presents a qualitative analysis method based on fuzzy relations for a cross-impact model designed for a technology impact assessment. The cross-impact knowledge is often uncertain or fuzzy when dealing with future events. Assessing the cross-impact relationships among future technologies creates a more uncertain or fuzzy situation because of the time and the uncertainty involved in evaluating future technologies. In addition, experts prefer to use linguistic terms or fuzzy values in their predictions. Thus a cross-impact matrix is represented as fuzzy relations on causal concepts. We therefore develop inference algorithms based on fuzzy relations and show a simple technology assessment example to illustrate this approach. This approach is useful in finding the key technology because it considers not only the direct impact but also the indirect impact.  相似文献   
106.
This paper suggests a technology forecasting approach based on a semi-Markov model, which appropriately describes the probabilistic nature of a sequential technology development process. This approach focuses primarily on the utilization of the information that has been skipped in conventional Delphi survey data. That is, through a simple statistic, the interrelationships among sequential technology developments can be extracted in a formal structure of a semi-Markov model from the original Delphi panel's estimates. A simulation technique is developed to forecast the development process by utilizing the information on such interrelationships. This technique provides a flexible and useful tool for R&D planners or project managers, especially in postanalysis of Delphi forecasting. To make good use of the approach, a computer-based interactive Delphi data analysis system (IDEAS) is implemented in IBM PC.  相似文献   
107.
We examine the relation between Chief Executive Officer (CEO) overconfidence and significant increases in research and development (R&D) expenditures. Although prior studies reveal a significantly positive market reaction to increases in R&D expenditures in both the long and short run, we find that long‐run stock performance is positive only for firms whose CEOs are not overconfident. Our findings, which may be attributable to overinvestment and the overestimation of future cash flows, imply that R&D resulting from overconfident behavior does not provide any value to firms.  相似文献   
108.
Automatic order matching systems have emerged as an electronic alternative to traditional markets. In current automatic order matching systems, price and quantity are the only product dimensions used for the order matching. However, a single-commodity market is made up of many heterogeneous goods which are close to each other but different in qualities and delivery conditions. Price and quantity are important but represent only parts of product attributes that commodity traders want to take into account. This study aims to extend current automatic order matching systems by diversifying product dimensions. An intelligent order matching system not only maximizes the total transaction volume based on the price and quantity but also satisfies traders' qualitative preferences over attributes other than price and quantity. The intelligent order matching mechanism combines an economic model with a preference model to incorporate both quantitative and qualitative utility of market participants. Constraint logic programming is investigated as a new information technology to structure and implement the intelligent order matching system.  相似文献   
109.
As breast cancer is the most prevalent cancer among women in Singapore, encouraging them to engage in preventive measures becomes increasingly important. This study aims to take a closer look at the influence of attention to media, interpersonal communication, news elaboration, and knowledge on women’s (aged between 30 and 70) perceived risks of breast cancer and their intentions to engage in preventive measures in Singapore. Attention to media, frequency of interpersonal communication, fatalistic belief, and knowledge structure density were found to be associated with risk perception of breast cancer among Singaporean women. Findings also showed that frequency of interpersonal communication, risk perception, elaboration, and factual knowledge were positively associated with women’s intentions to take up preventive measures such as breast self-examination, clinical breast examination, and mammography. Implications for theory and practice were discussed.  相似文献   
110.
We consider the effect of mergers between firms whose products are not viewed as direct substitutes for the same good or service, but are bundled by a common intermediary. Focusing on hospital mergers across distinct geographic markets, we show that such combinations can reduce competition among merging hospitals for inclusion in insurers' networks, leading to higher prices (or lower‐quality care). Using data on hospital mergers from 1996–2012, we find support that this mechanism operates within state boundaries: cross‐market, within‐state hospital mergers yield price increases of 7%–9 % for acquiring hospitals, whereas out‐of‐state acquisitions do not yield significant increases.  相似文献   
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