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   151079篇
  免费   3750篇
  国内免费   26篇
财政金融   25588篇
工业经济   11564篇
计划管理   21641篇
经济学   28990篇
综合类   1449篇
运输经济   963篇
旅游经济   2488篇
贸易经济   23449篇
农业经济   6080篇
经济概况   16904篇
水利工程   15491篇
信息产业经济   8篇
邮电经济   240篇
  2021年   1066篇
  2020年   1813篇
  2019年   2636篇
  2018年   2732篇
  2017年   2756篇
  2016年   3081篇
  2015年   2379篇
  2014年   3798篇
  2013年   16360篇
  2012年   4767篇
  2011年   4564篇
  2010年   4006篇
  2009年   4644篇
  2008年   4219篇
  2007年   3680篇
  2006年   4027篇
  2005年   3915篇
  2004年   3561篇
  2003年   3079篇
  2002年   3103篇
  2001年   2910篇
  2000年   2765篇
  1999年   2675篇
  1998年   2543篇
  1997年   2609篇
  1996年   2432篇
  1995年   2240篇
  1994年   2245篇
  1993年   2226篇
  1992年   2306篇
  1991年   2160篇
  1990年   2015篇
  1989年   1901篇
  1988年   1807篇
  1987年   1813篇
  1986年   1826篇
  1985年   2612篇
  1984年   2506篇
  1983年   2321篇
  1982年   2178篇
  1981年   2105篇
  1980年   2118篇
  1979年   2047篇
  1978年   1868篇
  1977年   1817篇
  1976年   1638篇
  1975年   1475篇
  1974年   1401篇
  1973年   1403篇
  1972年   1102篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
This paper explores differences in the bidding patterns of entrants and incumbents in road construction auctions. We find that entrants bid more aggressively and win auctions with significantly lower bids than incumbents. The differences in their bidding patterns are consistent with a model of auctions in which the distribution of an entrant's costs exhibits greater dispersion than that of an incumbent's and relations of stochastic dominance in the distributions do not persist for the entire range of estimated costs. We also find that more efficient firms bid, on average, more aggressively and firms with greater backlogs bid less aggressively.  相似文献   
82.
One Pleistocene mystery is why early North Americans eradicated their large, potentially domesticable animals (e.g., horses), whereas early Europeans did not. A commonly‐held hypothesis is that European species were evasive due to co‐evolution with hominids, whereas North American animals were naïve and unable to adapt quickly enough when experienced human hunters arrived from Eurasia. We explore this hypothesis with a paleoeconomic model of co‐evolution that integrates human hunting investments and wildlife population responses. We find that investments in hunting ability, based on the relative scarcity of prey species, could have mattered more than wildlife ‘naivety’ in explaining the extinction.  相似文献   
83.
84.
Despite the prevalence of elective business ethics courses, little research has sought to explain and predict why some students enroll in these courses and while others do not. Using the theory of planned behavior (Ajzen and Madden, 1986) as a theoretical foundation, 178 graduate students in Ireland were surveyed about their intention to sign up for an elective ethics class. Their behavior was measured two months later. The results reveal the power of the theory of planned behavior to explain and predict who takes elective ethics classes.Donna M. Randall is an associate professor and chair in the Department of Management and Systems at Washington State University. Her research interests include business ethics, organizational commitment, and reproductive risk in the work place. Her work has appeared inJournal of Business Ethics, Decision Sciences, Academy of Management Review, Journal of Vocational Behavior, Journal of Business Research, and others.  相似文献   
85.
Dissolved organic carbon (DOC) dynamics were investigated over a two year period in the Upper Rhǒne River to examine the role of side-arms in providing DOC to the main channel in relation to discharge fluctuations, especially floods. Concentrations of DOC are shown to remain low in space and in time (average 1.5 mg ?1) and to be more related to global hydrological events (precipitation) than to any local flushing for backwaters during floods. The results do not support the general assumption that side-arms are the providers of DOC to the main channel.  相似文献   
86.
87.
In this paper we will analyze the relationship between the value and duration moments of a cash flow and movements in the yield curve. We will show that for changes in the yield curve which can be related to tn , the 1st order changes in the net present value of a cash flow are linearly dependent on the n + lth duration moments, and that the 2nd order changes are dependent on the sum of duration moments of order 2 n + 1 and 2 n + 2. We will use this relationship to tilt tracking portfolios so as to protect them against specific changes in the yield curve.  相似文献   
88.
89.
90.
Conclusions 1. Use of dewatering systems based on voidless drainage is most effective when dewatering slightly permeable soils in regions with a deep seasonal frost. 2. Two-story drainage with the upper and lower stories spaced 30 m apart accelerates the discharge of gravitational water from the arable layer. Results of observations on two-story drainage in experimental-production sections indicated that it discharges 2 – 3.8 times more water than systematic tubular drainage with an interdrain spacing of 10 m and a 0.2-m thick three-dimensional filter of a sandy-gravelly mixture. 3. It is recommended to use crushed stone and porous-clay gravel with a fineness of 10 – 20 mm as a filler. In that case, protection of the drain filler is, as a rule, required only from the intrusion of soil from above during construction in cohesive soils with a plasticity indexW p≥7. 4. seepage rate in a voidless drain should be lower than the scouring velocity for the soil in which the voidless drainage is placed. In the opposite case, it is necessary to lower the grade of the drains or select a filler gradation such that the seepage rate in the drain be lower than the scouring velocity. Translated from Gidrotekhnicheskoe Stroitel’stvo, No. 8, pp. 41–43, August, 1998.  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