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   1704篇
  免费   270篇
  国内免费   24篇
财政金融   202篇
工业经济   142篇
计划管理   415篇
经济学   260篇
综合类   177篇
运输经济   24篇
旅游经济   35篇
贸易经济   539篇
农业经济   69篇
经济概况   135篇
  2024年   3篇
  2023年   26篇
  2022年   25篇
  2021年   49篇
  2020年   90篇
  2019年   68篇
  2018年   78篇
  2017年   77篇
  2016年   67篇
  2015年   86篇
  2014年   137篇
  2013年   160篇
  2012年   175篇
  2011年   182篇
  2010年   143篇
  2009年   82篇
  2008年   112篇
  2007年   109篇
  2006年   92篇
  2005年   51篇
  2004年   47篇
  2003年   32篇
  2002年   22篇
  2001年   24篇
  2000年   13篇
  1999年   12篇
  1998年   9篇
  1997年   7篇
  1996年   3篇
  1995年   4篇
  1994年   7篇
  1992年   1篇
  1991年   2篇
  1990年   1篇
  1984年   1篇
  1983年   1篇
排序方式: 共有1998条查询结果,搜索用时 31 毫秒
1.
REITs draw attention from investors around the world, yet our understanding of the various risks associated with such securities is limited. Using the introduction of Arrowhead, a low-latency high-frequency trading platform, to the Tokyo Stock Exchange and the financial crisis of 2008 as natural experiments, we compare the resilience of REITs and equities in terms of liquidity and volatility. The results indicate that the introduction of Arrowhead improved the quality of the Japanese REIT market but also increased the probability of flash crashes. We also find that although the financial crisis significantly deteriorated overall equity market quality, the Japanese REIT market was resilient. Finally, using a difference-in-differences regression model, we show that the higher transparency and better price discovery of REITs, compared to non-REITS, protected them from the negative effects of the financial crisis and the introduction of Arrowhead. Overall, our analysis shows that REITs are more resilient than non-REITs.  相似文献   
2.
This paper deals with a fundamental subject that has seldom been addressed in recent years, that of market impact in the options market. Our analysis is based on a proprietary database of metaorders—large orders that are split into smaller pieces before being sent to the market—on one of the main Asian markets. In line with our previous work on the equity market [Said, E., Bel Hadj Ayed, A., Husson, A. and Abergel, F., Market impact: A systematic study of limit orders. Mark. Microstruct. Liq., 2018, 3(3&4), 1850008.], we propose an algorithmic approach to identify metaorders, based on some implied volatility parameters, the at the money forward volatility and at the money forward skew. In both cases, we obtain results similar to the now well-understood equity market: Square-Root Law, Fair Pricing Condition and Market Impact Dynamics.  相似文献   
3.
针对双站定位涉及的跳频信号多普勒频差估计问题,提出了归一化的频差最大似然估计算法,利用两个定位站接收到的跳频脉冲串信号,构建一个关于基准跳频频率多普勒频差的似然函数,通过网格搜索得到使似然函数最大的多普勒频差估计,既解决了跳频信号在不同跳频频率上多普勒频差不一致的问题,又充分利用在不同频率的脉冲串信号提高了多普勒频差估计精度。通过仿真对算法的性能进行了评估,结果表明,与基于子空间的算法比较,在脉冲数达到240个时,所提算法执行效率提升30%以上。  相似文献   
4.
为解决实际应用中克拉维酸钾峰与后相邻杂质的分离度达不到要求的问题,建立了一种同时测定阿莫西林克拉维酸钾片中阿莫西林和克拉维酸钾含量的新方法,采用反相高效液相色谱法(RP-HPLC),Ultimate AQ-C_(18)色谱柱(4.6mm×250 mm,5μm),以pH值为4.4的0.05 mol/L磷酸二氢钠缓冲液为流动相,柱温为35℃,流速为1.0mL/min,检测波长为220nm。结果表明:阿莫西林和克拉维酸钾两主峰与相邻杂质得到完全基线分离,分离度大于1.5;克拉维酸钾对照品溶液质量浓度为0.050 0~0.500 1mg/mL时与峰面积的线性关系良好(r=0.999 8),平均回收率(n=9)为100.14%,RSD值为0.24%;阿莫西林对照品溶液质量浓度为0.100 0~1.000 1mg/mL时与峰面积的线性关系良好(r=0.999 9),平均回收率(n=9)为100.45%,RSD值为0.17%。与原有的《中华人民共和国药典》方法相比,新的阿莫西林克拉维酸钾片含量测定方法专属性好,准确度高,操作简便快捷,结果可靠,可作为一种质量控制方法。  相似文献   
5.
Yu Ri Kim 《The World Economy》2019,42(9):2684-2722
The importance of aid for trade as a tool for facilitating trade, economic growth and social development has received attention since the concept was introduced in 2005. While one of the main targets of aid for trade is export diversification, reflecting the fact that the exports of many developing countries are concentrated in a small range of items, there have not been many efforts to measure the effect of aid for trade on export structure. This study, therefore, attempts to trace the relationship between aid for trade and 133 aid recipients' export structure between 1996 and 2013. Using the Herfindahl–Hirschman Index to measure the degree of export concentration, the findings suggest that total aid for trade has reduced the concentration level in the short run. In the long run, on the other hand, aid for trade has had no significant effect on export structure of recipient countries. Only aid for building productive capacity, which is one of the three categories of aid for trade, contributes to lower concentration. Yet, this change is not caused by an increase in export diversity but by the redistribution of shares of existing products of a similar sophistication level.  相似文献   
6.
This study aims to explore the causal relationship between economic risk and foreign direct investment (FDI) inflows for the case of Turkey. With the aim of establishing robust findings for the research in mind, both traditional and modern causality techniques are utilized; time domain Granger (1969, “Investigating Causal Relations by Econometric Models and Cross-Spectral Methods.” Econometrica 37: 424–438.), Toda and Yamamoto (1995, “Statistical Inference in Vector Autoregressions with Possibly Integrated Processes.” Journal of Econometrics 66 (1–2): 225–250.), Fourier Toda-Yamamoto and frequency domain Breitung and Candelon (2006, “Testing for short- and long-run causality: A frequency-domain approach.” Journal of Econometrics 132 (2): 363–378.) spectral causality test. Our empirical findings reveal that; economic risk changes in Turkey significantly lead to changes in FDI inflows. However, there is no evidence of causality running from FDI to economic risk. The findings imply that economic risk is an essential determinant of FDI inflows in Turkey. Our findings are compatible with historical macroeconomic developments in Turkey and imply important policy implications. The results of this study can be generalized for other emerging economies that have similar macroeconomic environments, in order to create useful policy implications regarding FDI inflow.  相似文献   
7.
[目的]文章选取了山西省3个具有代表性的特色农业产业集群(运城苹果、朔州羊肉、晋城大豆)进行研究,通过探索山西省特色农业产业集群发展的优势与不足,有助于提升产品竞争力和助力区域经济发展,进而达到促进农业发展、带动农民增收的目的。[方法]文章运用2005年、2010年、2015年3个时期的数据,首先基于波特的钻石模型分析了3个产业的发展情况,然后运用区位商和集中系数指标、产业效率优势指数和规模优势指数指标分别分析了3个特色农业产业集群的集中化程度和竞争力。[结果]从集中化程度来看,运城苹果产业发展进入成熟阶段,专业化程度和集中化程度近几年一直较为稳定,进一步提升空间不大;朔州羊肉产业处于大幅上升阶段,集中化程度明显,且优于专业化程度;晋城大豆产业专业化程度优势优于集中化程度优势,但二者均呈先升后降趋势。从竞争力评价角度来看,运城苹果产业已初具产业效率优势且稳定上升,规模优势稳定且变化不明显;朔州羊肉产业具有极高的产业效率优势且高位运行,规模优势稳定且处于成熟阶段;晋城大豆产业正在形成产业效率优势,规模优势近年来稍有下降。从综合比较优势来看,运城苹果产业处于成熟阶段,朔州羊肉产业具有极强的综合比较优势,晋城大豆产业受规模优势下降的影响而下降。[结论]总体来看,3个产业作为山西省的特色农业产业,其集中化程度和竞争力均较高,且具有发展优势和发展空间,区域布局合理,已经形成或正在形成特色农业产业集群,但同时也存在一定的问题。从微观层面来说,农户、企业等微观主体应该继续发挥产品的品质优势,同时努力扩大市场份额和拓展销售渠道,积极延伸产业链,加强与科研院所的合作;从宏观层面来说,应该加强政府支持和引导,减少市场风险的不确定性。  相似文献   
8.
The endo–exo problem lies at the heart of statistical identification in many fields of science, and is often plagued by spurious strong-and-long memory due to improper treatment of trends, shocks and shifts in the data. A class of models that has shown to be useful in discerning exogenous and endogenous activity is the Hawkes process. This class of point processes has enjoyed great recent popularity and rapid development within the quantitative finance literature, with particular focus on the study of market microstructure and high frequency price fluctuations. We show that there are important lessons from older fields like time series and econometrics that should also be applied in financial point process modelling. In particular, we emphasize the importance of appropriately treating trends and shocks for the identification of the strength and length of memory in the system. We exploit the powerful Expectation Maximization algorithm and objective statistical criteria (BIC) to select the flexibility of the deterministic background intensity. With these methods, we strongly reject the hypothesis that the considered financial markets are critical at univariate and bivariate microstructural levels.  相似文献   
9.
基于引力模型,结合社会网络分析法的凝聚子群分析,对31个省(区、市)的创新产出空间联系进行探究,研究发现:我国省域创新产出空间联系主要集中于京津冀和长三角一带,呈现出严重的分布不均状况,具有较强的区域集中性和空间依赖性;北京、天津、上海、浙江、江苏作为区域创新产出引力较强的节点省(区、市),对周边区域的创新产出具有较强的辐射作用;总体来看,省域创新产出空间联系并没有形成贯穿东西南北的交叉网状结构,中心省(区、市)数量较少且分布不均,辐射范围有限。基于此,提出加大区域创新投入、减少区域创新产出联系的政策性障碍、营造区域创新产出联系的良好环境等政策建议。  相似文献   
10.
This study suggests that testing the impact of exchange rate on trade should be done using high-frequency data. Using different data frequencies for identical periods and specifications between the US and Canada, we show that low-frequency data might suppress and distort the evidence of the impact of exchange rate on trade in the short run and the long run.  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