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   4103篇
  免费   175篇
  国内免费   18篇
财政金融   620篇
工业经济   275篇
计划管理   999篇
经济学   678篇
综合类   306篇
运输经济   65篇
旅游经济   105篇
贸易经济   765篇
农业经济   183篇
经济概况   299篇
信息产业经济   1篇
  2024年   6篇
  2023年   42篇
  2022年   41篇
  2021年   90篇
  2020年   122篇
  2019年   99篇
  2018年   109篇
  2017年   144篇
  2016年   118篇
  2015年   96篇
  2014年   237篇
  2013年   429篇
  2012年   336篇
  2011年   344篇
  2010年   301篇
  2009年   271篇
  2008年   293篇
  2007年   234篇
  2006年   241篇
  2005年   188篇
  2004年   155篇
  2003年   95篇
  2002年   52篇
  2001年   48篇
  2000年   47篇
  1999年   25篇
  1998年   35篇
  1997年   20篇
  1996年   20篇
  1995年   11篇
  1994年   8篇
  1993年   7篇
  1992年   3篇
  1991年   7篇
  1990年   2篇
  1989年   3篇
  1988年   1篇
  1987年   1篇
  1985年   4篇
  1984年   5篇
  1983年   2篇
  1982年   2篇
  1980年   1篇
  1976年   1篇
排序方式: 共有4296条查询结果,搜索用时 15 毫秒
101.
The gold ores in Roşia Montană have been intensely mined for the last two thousand years, as this mining district was one of the richest gold deposits in the Apuseni Mountains (the so-called Golden Quadrangle of Romania). Itis currently considered the largest gold deposit in Europe. Up until a few decades ago, gold mines had a relatively predictable path, which began with exploration and ended with abandonment. This has since changed, once the impact of abusive past or current exploitation methods and technologies has been deemed unacceptable by the state and the public. With its millennia-old history of mining, Roșia Montană raises the intriguing question of what does the future hold for different actors in a situation that is clearly unsustainable, but which may be continued through environmental rehabilitation, or even a larger mine. We address the question for this particular mine by drawing on a worldwide database of similar cases contained in the Environmental Justice Atlas (EJAtlas). We consider three scenarios, namely: 1) continued degradation with no intervention; 2) approval of large-scale mining, due to international arbitration; 3) environmental rehabilitation. These capture the most plausible future scenarios of the Roșia Montană case and, by relating them to the relevant transnational environmental justice context, we aim at assessing their implications for different actors and also the extent to which they are illustrative for the fate of other mines worldwide. Mine closure and the rehabilitation of the environment, regardless how distant they may seem at the beginning of the prospection and extraction stage, are imminent in the mine life cycle and a mandatory step of the environmental management process. We conclude by suggesting under which governance regimes each scenario is likely to unfold and what implications can be drawn for public policy.  相似文献   
102.
Recent non-parametric statistical analysis of high-frequency VIX data (Todorov and Tauchen, 2011) reveals that VIX dynamics is a pure jump semimartingale with infinite jump activity and infinite variation. To our best knowledge, existing models in the literature for pricing and hedging VIX derivatives do not have these features. This paper fills this gap by developing a novel class of parsimonious pure jump models with such features for VIX based on the additive time change technique proposed in Li et al., 2016a, Li et al., 2016b. We time change the 3/2 diffusion by a class of additive subordinators with infinite activity, yielding pure jump Markov semimartingales with infinite activity and infinite variation. These processes have time and state dependent jumps that are mean reverting and are able to capture stylized features of VIX. Our models take the initial term structure of VIX futures as input and are analytically tractable for pricing VIX futures and European options via eigenfunction expansions. Through calibration exercises, we show that our model is able to achieve excellent fit for the VIX implied volatility surface which typically exhibits very steep skews. Comparison to two other models in terms of calibration reveals that our model performs better both in-sample and out-of-sample. We explain the ability of our model to fit the volatility surface by evaluating the matching of moments implied from market VIX option prices. To hedge VIX options, we develop a dynamic strategy which minimizes instantaneous jump risk at each rebalancing time while controlling transaction cost. Its effectiveness is demonstrated through a simulation study on hedging Bermudan style VIX options.  相似文献   
103.
Desertification and land degradation are worldwide problems affecting soil, vegetation and the livelihoods of rural populations. Bowal (plural bowé) is a particular form of degraded land that occurs in tropical regions and leads to the exposure of ferricretes, which are unsuitable for farming. Bowé are more common on farmland and degraded savanna. Changes in land use/land cover were used to map a region of 6.7 million ha in northern Benin, West Africa in 1975, 1990 and 2010. The changes observed during these periods (1975–1990, 1990–2010 and 1975–2010) were used to predict the occurrence of bowé in the period up to 2050 using Markovian chain analysis. The results showed a considerable change in land use/land cover during the three periods. The types of land on which bowé occur (farmland and degraded savanna) increased in northern Benin by 5.4% per year during the period 1975–1990 and 9.5% per year during the periods 1990–2010, while the natural vegetation (forest, woodland and tree savanna) decreased by the same amount. The future scenarios also predicted the same trend. In the period 1975–1990, 1.28 million ha (26%) of natural vegetation was converted to degraded savanna and farmland while 2.23 million ha (53%) of natural vegetation was converted to degraded savanna and farmland in the period 1990–2010. Based on the dynamics recorded during the period 1975–1990 and 1990–2010 respectively, a total of 1.28 million ha (26% of the natural vegetation that was present in 1975) and 1.29 million ha (31% of the natural vegetation that was present in 1990) will be converted to farmland and degraded savanna in the study area by 2050.Thus bowalization will persist and increase in the period up to 2050. The natural vegetation could disappear if protection and restoration measures are not taken. It is thus important to take measures to stop the degradation and to implement programs to restore soils on bowé based on the soil and water conservation techniques used on highly degraded West African soils, such as zaï pit and stone rows with grass strips. Some native plants species adapted to bowalization and resistant to climate change in northern Benin (e.g. Asparagus africanus, Andropogon pseudapricus and Combretum nigricans) should be used in association with soil and water conservation techniques on bowé.  相似文献   
104.
Forced to compete with private and public sector providers, charities experience tensions as the quest for a more commercially-oriented position may conflict with their social imperative. Little attention has been given to understanding the experiences of local charities as service providers. This paper captures the reactions of those working on the charity front line.  相似文献   
105.
This paper uses a model of strategic interaction among firms –that set discriminatory and nonlinear prices– in addition to public information on prices of the plans marketed by the three major mobile phone companies, to assess the extent to which on-net/off-net price differentials in the plans they offered could represent predatory practices in the mobile telephony market in Chile. The results show that the largest companies offered a few plans with an off-net/on-net price differential larger than what a competitive theoretical model predicts. This larger differential is consistent with the notion of predation defined by Hoernig (2007) as reducing a competitor's profits. Despite the fact that these plans were a small fraction of all the plans mobile phone firms offered, they were recently banned by the antitrust authority because of their potential anticompetitive effects.  相似文献   
106.
In order to promote angel investments, attracting those who have entrepreneurial experience is necessary because their capital, unique managing experience, and business insight are highly beneficial to the performance of the investment. This can be accomplished by providing a preferred investment environment for potential angels who have entrepreneurial backgrounds. In this paper, we use an adaptive conjoint analysis to identify preferred investment environments represented as a combination of support policies for business angels who have entrepreneurial experience in Korea. Of particular interest is a preference for angel insurance. This insurance is newly proposed based on prospect theory, which explains that people tend to be more sensitive to a loss than to a gain. The value of the angel insurance is compared to those of tax policies and matching funds for business angels. The empirical results are expected to contribute to promoting angel investments by attracting entrepreneurs to become business angels.  相似文献   
107.
对与油气管道领域相关的ISO、API、ASME、ASTM、NACE 5所知名国外标准化组织进行了简要介绍,对各组织在提案申请要求、提案内容、尤其是标准制修订流程方面进行了初步对比分析,同时以参与国际标准化组织ISO,为例详细说明了参与国际标准的注意事项及技巧,最后提出了我国在油气管道领域开展标准国际化的启示和建议。  相似文献   
108.
Many statistical agencies use the sum of hours worked when measuring labour services. This implies that all workers provide work of equal quality. Various indices for adjusting for labour quality have been employed in a large body of literature. However, this literature has not yet addressed the issue of how to quality‐adjust the impact of workers entering and exiting the labour market. We outline a theoretical framework for dealing with quality adjustment of labour services caused by workers entering and exiting employment. To illustrate the theoretical framework, we use the case of Norway in the period 1997–2013. The impact on labour services due to our quality adjustment of net entry is found to be cyclical. While the adjustment for the quality of net entry amounts to about −0.3 percentage points annually during expansions, it is offset by about the same magnitude during contractions.  相似文献   
109.
The importance of board committees – specialized subgroups that exist to perform many of the board's most critical functions, such as setting executive compensation, identifying potential board members, and overseeing financial reporting – has grown over time due to increased legal requirements and greater complexity of the environment in which firms operate. This has resulted in a large body of work examining board committees across the accounting, finance, and management disciplines. However, this research has developed rather independently within each discipline, preventing scholars and practitioners from developing a comprehensive understanding of board committees. To address this issue, we conduct a comprehensive review of the literature that: 1) summarizes and synthesizes antecedents and outcomes associated with board committees in publicly‐traded firms in English common law countries; and 2) offers a critical analysis of existing research, providing recommendations for advancements and new directions in board committee research.  相似文献   
110.
In an arbitrage-free economy with non-zero bid-ask spreads the existence of payoffs whose price is lower than the price of a dominated payoff cannot be discarded in general. However, when the former price corresponds to trivial portfolios which involve buying or selling one unit of the basis assets, its presence, although not an arbitrage, is a severe market anomaly which we refer to as an inefficient quote. In an empirical study, we report evidence that indicates that in options markets both the frequency and the magnitude of these anomalies are substantial and we document puzzling patterns in their behavior.  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