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51.
52.
Consider a linear regression model and suppose that our aim is to find a confidence interval for a specified linear combination of the regression parameters. In practice, it is common to perform a Durbin–Watson pretest of the null hypothesis of zero first‐order autocorrelation of the random errors against the alternative hypothesis of positive first‐order autocorrelation. If this null hypothesis is accepted then the confidence interval centered on the ordinary least squares estimator is used; otherwise the confidence interval centered on the feasible generalized least squares estimator is used. For any given design matrix and parameter of interest, we compare the confidence interval resulting from this two‐stage procedure and the confidence interval that is always centered on the feasible generalized least squares estimator, as follows. First, we compare the coverage probability functions of these confidence intervals. Second, we compute the scaled expected length of the confidence interval resulting from the two‐stage procedure, where the scaling is with respect to the expected length of the confidence interval centered on the feasible generalized least squares estimator, with the same minimum coverage probability. These comparisons are used to choose the better confidence interval, prior to any examination of the observed response vector.  相似文献   
53.
Norms that restrict choice sets or impose otherwise harsh requirements would seem to act as barriers to group formation by raising the costs of adherence to potential and continuing members. Contrary to that intuition, one observes a broad range of group norms in the real world that impose large costs on group members. Iannaccone provides a rationale for harsh norms as a mechanism to reduce free‐riding in supplying a club good. This paper proposes a new rationalization for harsh group norms as a mechanism under which harsh norms serve to screen out disloyal members, providing what is essentially a technology for measuring loyalty in environments where group leaders cannot reliably measure group members' loyalty. The model demonstrates that loyalty can be signalled through acts that are seemingly irrelevant to the group's core objectives and identity.  相似文献   
54.
The performance of public organizations has become a more salient issue as the popularity of accountability policies has grown. Though organizations are often defined as underperforming, little is known about the effectiveness of various strategies commonly recommended for agency turnaround. This study provides a large-N test of three common categories of turnaround mechanisms – retrenchment, repositioning, and reorganization – in nearly 300 failing New York City schools between 2008 and 2011. Models show that none of the three turnaround strategies appear to be significantly associated with improvements in core organizational performance from an administrative perspective, although repositioning appears to improve client satisfaction.  相似文献   
55.
Despite recent interest in flipped classrooms, rigorous research evaluating their effectiveness is sparse. In this study, the authors implement a randomized controlled trial to evaluate the effect of a flipped classroom technique relative to a traditional lecture in an introductory undergraduate econometrics course. Random assignment enables the analysis to eliminate other potential explanations of performance differences between the flipped and traditional classrooms, while assignment of experimental condition by section and lesson enables improved statistical precision. The authors find that the flipped classroom increases scores on medium-term, high-stakes assessments by 0.16 standard deviation, with similar long-term effects for high-performing students. Estimated impacts are robust to alternative specifications accounting for possible spillover effects arising from the experimental design.  相似文献   
56.
This article investigates the pricing/hedging conundrum, i.e. the observation of a mismatch between derivatives models’ pricing and hedging performances, that has so far been under-emphasized as the literature tends to focus on increasingly complicated option pricing models, without adequately addressing hedging performance. Hence, we analyse the ability of the Black–Scholes, Practitioner Black–Scholes, Heston–Nandi and Heston models to Delta-hedge a set of call options on the S&P500 index and Apple stock. We extend earlier studies in that we consider the impact of asset dynamics, apply a stringent payoff replication strategy, look at the impact of moneyness at maturity and test for the robustness to the parameters’ calibration frequency and Delta-Vega hedging. The study shows that adding risk factors to a model, as stochastic volatility, should only be considered in light of the data dynamics. Even then, however, more complicated models generally fare poorly for hedging purposes. Hence, a better fit of a model to option prices is not a good indicator of its hedging performance, and so of its ability to describe the underlying dynamics. This can be understood for reasons of over-fitting. Those findings hint to a potentially appealing hedging-based calibration of models’ parameters, rather than the standard pricing-based one.  相似文献   
57.
This study employs questionnaire survey and financial accounting data to extend earlier empirical work on the foreign exchange (FX) exposure management practices of Finnish industrial firms. The paper concentrates on: (i) the form that FX corporate hedging policy takes; (ii) the control of FX procedures and trading; and, (iii) our respondents' perceptions about their ability to predict FX rate changes for hedging decisions. Our results indicate that the extent to which firms hedge FX exposure depends on the type of exposure and the form that FX hedging policy takes. Also, a significant number of the firms pursue FX hedging strategies on the expectation of attaining trading profits and this strategy appears to be accommodated within their FX policies. This feature is not explicitly demonstrated in previous studies. Finnish firms hedge a much higher proportion of both transaction and translation exposures compared to economic exposure. We partly attribute this emphasis to the requirements of the Finnish Accounting Act, which came into effect in 1993. The organisational, historical and financial settings of the firms also have significant impacts on exposure management practices. The overall implication of those results is that firms respond to changes in the financial, economic and regulatory environments in which they operate.  相似文献   
58.
Incentives in agriculture are highly distorted. It has long been argued that these distortions were a key explanation for differences in supply and productivity across countries, but the empirical evidence is limited. We revisit this issue using data on policy distortions across 63 countries for the period 1961–2011. We estimate the effects of differential changes in agricultural distortions across countries on supply and productivity. We highlight concerns in our analysis and previous work about endogeneity that biases the estimated effect downward—countries that lose comparative advantage are likely to increase support for agriculture. We address these concerns by including country and region-time fixed effects, along with a rich set of controls. Overall, we find evidence that enhanced incentives through policy changes can increase the rate of production growth, with about half of the increase due to productivity increases. This result is strongest in Sub-Saharan Africa where anti-agricultural policies on exports were reduced and in Europe where pro-agricultural policies on imports were reduced, driven largely by external pressure. Endogeneity appears to be strongest in Asia where countries have followed the typical pattern of raising support for agriculture during industrialization due to a rising farm-urban income gap.  相似文献   
59.
To help bridge the obstacle of inadequate injury fatality data in low and medium income countries (LMICs) a simple cost effective system for mortuary surveillance of fatal injuries is being developed in consultation with the WHO. This will inform, direct and monitor injury prevention (IP) interventions and policies in LMICs. This article uses CDC's 'attributes of a successful surveillance system' to describe the process, the barriers and solutions in development of this mortuary data guideline. The consultative process utilised generated feedback from key stakeholders including forensic pathologists, Ministry of Health officials and injury prevention experts. An International Advisory Group was also convened to guide the guideline development. These assisted the adjustment of the proposed guideline to maximise flexibility, acceptability and stability; whilst minimising resource implications. Representativeness and the securing of government support perhaps remain the most significant challenges. Consultation with the advisory group and the wider stakeholders has been effective in developing a widely acceptable, user-friendly, low resource data form to gather useful data. Further strategies to overcome barriers need to be developed over the course of the pilot study and this should be done in consultation with the advisory group and stakeholders.  相似文献   
60.
Survey-based research concerning sexual behaviour almost inevitably confronts the simultaneous problems of misreporting and non-response. These problems lead to disparities among estimates of the number and characteristics of those who engage in same-sex sexual behaviour. This paper proposes a statistical model to consistently estimate the frequency of same-sex sexual behaviour in the presence of non-ignorable misreporting and non-response. The model is fitted using 1991–2000 General Social Survey data. Frequency estimates corrected for simultaneous misreporting and non-response are reported. According to the model, 7.1% of US males and 4.1% of females – 15.8 million individuals – are not exclusively heterosexual. Allowing for misreporting and non-response increases the estimated same-sex frequency by more than four million. The model reveals new patterns between misreporting and non-response probabilities and standard demographic variables such as age and income.  相似文献   
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