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   155682篇
  免费   4822篇
  国内免费   261篇
财政金融   25671篇
工业经济   11901篇
计划管理   22641篇
经济学   29541篇
综合类   2661篇
运输经济   1018篇
旅游经济   2578篇
贸易经济   23995篇
农业经济   6480篇
经济概况   17884篇
水利工程   16147篇
信息产业经济   8篇
邮电经济   240篇
  2021年   1292篇
  2020年   1947篇
  2019年   2727篇
  2018年   2685篇
  2017年   2805篇
  2016年   3145篇
  2015年   2656篇
  2014年   4185篇
  2013年   16756篇
  2012年   5317篇
  2011年   5098篇
  2010年   4732篇
  2009年   5328篇
  2008年   4872篇
  2007年   4154篇
  2006年   4608篇
  2005年   4392篇
  2004年   3559篇
  2003年   3245篇
  2002年   3282篇
  2001年   3065篇
  2000年   2793篇
  1999年   2674篇
  1998年   2468篇
  1997年   2552篇
  1996年   2408篇
  1995年   2190篇
  1994年   2200篇
  1993年   2180篇
  1992年   2238篇
  1991年   2078篇
  1990年   1964篇
  1989年   1872篇
  1988年   1773篇
  1987年   1780篇
  1986年   1788篇
  1985年   2573篇
  1984年   2461篇
  1983年   2259篇
  1982年   2138篇
  1981年   2076篇
  1980年   2092篇
  1979年   2004篇
  1978年   1844篇
  1977年   1811篇
  1976年   1621篇
  1975年   1467篇
  1974年   1392篇
  1973年   1399篇
  1972年   1098篇
排序方式: 共有10000条查询结果,搜索用时 274 毫秒
991.
This paper considers the extent to which price and income proxy variables help in forecasting tourist demand in Spain. Contrary to some recent studies, we found that the inputs' contribution in terms of fitting and forecasting is nil when compared with alternative univariate models. Whether these findings are the results of the restrictions embedded in building the proxy inputs or in a poor specification of the dynamics of these models remains to be seen. We also contend that when dealing with medium, long-term forecasting comparisons, the use of the traditional aggregate accuracy measures like RMSE and MAPE help very little in discriminating among competing models. In these situations, predicted annual growth rates may be a better alternative.  相似文献   
992.
This study uses data on intra-day transactions to analyze whether real estate investment (REIT) liquidity as measured by the bid-ask spread changed from 1990 to 1994, a period during which the industry's market capitalization increased from $8.7 billion to $45 billion. REIT percentage spreads (spread as percentage of share price) narrowed significantly, primarily attributable to higher share prices rather than narrower dollar-value spreads. An empirical model is used to analyze the determinants of percentage spreads. Return variance and share price, not market capitalization are found to be the primary determinants of percentage spreads in both periods. This suggests that the liquidity of REIT securities is similar to that of non-REIT securities with similar prices and return variance. In addition, percentage spreads are wider for REITs trading on the NASDAQ.  相似文献   
993.
Snapshot samples     
Edward H. Kaplan 《Socio》1997,31(4):281-291
We consider a coverage model where an initial event that occurs at some point in time triggers an activity of random duration that leads to some subsequent event. A snapshot sample is constructed at a fixed point in chronological time either by sampling only subjects where the initial event has occurred but the subsequent event has yet to occur (active subjects), or by sampling only subjects where both the initial and subsequent events have occurred (inactive subjects). The biases inherent in snapshot sampling can be neatly characterized by the properties of two random variables: the history (defined as the time the initial event occurs as measured into the past from the chronological point of sampling), and the active time (defined as the length of time between the initial and subsequent events). Though snapshot samples are biased, recognizing the biases enables correct inferences to be drawn from snapshot-sampled data. Considering only the case where and are independent random variables, this paper presents the probability models associated with snapshot sampling, demonstrates the problems that can occur, offers procedures for overcoming these problems, and applies the methods to interesting data sets.  相似文献   
994.
995.
Gartner观点:Gartner的专家们认为直至2003年Web服务才能真正发展起来。2003年全球40%的电子商务贸易将利用Web服务来完成,2004年这一数字将超过50%,而交易时间将大大缩短。2003年大约80%的开发平台将支持Web服务体系,Web服务将代表下一代软件开发平台的发展方向。据调查显示,在创建Web服务应用程序时,有78%的人使用的是J2EE,并且认为它是最有效的创建和配置Web服务的平台;而使用微软.Net的人为22%。从中我们似乎可以看出哪一个平台更适合于Web服务,哪一个平台又更适合于大多数的开发者。这两个平台的竞争,在2002年愈演愈烈。  相似文献   
996.
An optimal advertising rule is derived for a good sold in an open market (beef) when a related substitute good (chicken) is production rationed and whose imports are subject to trade restrictions. Such a rule is developed using a multi-market equilibrium displacement model that reflects demand interrelatedness, open trade of the advertised good (beef), with rationed production and restricted trade of the related good (chicken). The optimal rule nests earlier optimal advertising rules under a variety of conditions. Results underscore the importance of accounting for cross-product advertising effects. When these effects are present (absent), the optimal generic beef advertising intensity in Canada is shown to fall (rise) with elimination of supply management in Canada's chicken sector.
L'auteur dérive une règie sur l'optimisation de la publicité pour un produit vendu sur un marché libre (bœuf) en présence d'un produit de substitution rationné dont on restreint les importations. Pour parvenir à une telle règie, l'auteur a utilisé un modèle de déplacement du point d'équilibre sur un marché multiple illustrant les liens entre la demande des produits concernés, le libre-échange du produit faisant l'objet de la publicité (bœuf) et la restriction de la production et des importations du produit apparenté (poulet). La règie d'optimisation englobe les règles antérieures sur l'optimisation de la publicité dans diverses situations. Les résultats soulignent qu'il est important de prendre en compte les retombées de la publicité sur les autres produits. Au Canada, en présence (absence) de telles retombées, le degré optimal de publicité générique sur le bœuf diminue (augmente) avec l'abolition de la gestion de l'offre de poulet.  相似文献   
997.
998.
999.
The Dynamics of Alliance Conditions in the Alliance Development Process   总被引:10,自引:0,他引:10  
One of the key issues in understanding the developmental processes of strategic alliances is how the alliance conditions change over the different stages of alliance development. A related question concerns the nature of the co-evolutionary dynamics of alliances in terms of their constituent partner firms. In this article we propose an integrated process model of alliances that is based on alliance conditions, allianc developmental stages, and an alliance system comprising co-evolutionary elements. We suggest that alliance conditions, or the key characteristics of an alliance at any given moment, link the alliance environment (firm characteristics) and the alliance development process. We also explore how specific patterns of alliance conditions have differential impacts on the interactive elements of the alliance co-evolutionary system.  相似文献   
1000.
Sufficient conditions are found for designs, derived from completely symmetric designs by deleting binary blocks, to be E-optimal. Sufficient conditions are also found for E-optimality of designs obtained from other E-optimal designs by deleting all blocks forming a balanced incomplete block design on a subset of the treatments. The results include many binary and non-binary designs for which E-optimality was previously unknown.  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