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   150469篇
  免费   4398篇
  国内免费   26篇
财政金融   25595篇
工业经济   11567篇
计划管理   21654篇
经济学   28993篇
综合类   1449篇
运输经济   963篇
旅游经济   2488篇
贸易经济   23457篇
农业经济   6080篇
经济概况   16908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   1812篇
  2019年   2638篇
  2018年   2733篇
  2017年   2756篇
  2016年   3083篇
  2015年   2380篇
  2014年   3799篇
  2013年   16366篇
  2012年   4768篇
  2011年   4564篇
  2010年   4006篇
  2009年   4646篇
  2008年   4218篇
  2007年   3683篇
  2006年   4027篇
  2005年   3917篇
  2004年   3561篇
  2003年   3079篇
  2002年   3103篇
  2001年   2912篇
  2000年   2765篇
  1999年   2675篇
  1998年   2543篇
  1997年   2610篇
  1996年   2434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   1902篇
  1988年   1808篇
  1987年   1815篇
  1986年   1826篇
  1985年   2612篇
  1984年   2506篇
  1983年   2321篇
  1982年   2178篇
  1981年   2106篇
  1980年   2119篇
  1979年   2048篇
  1978年   1868篇
  1977年   1817篇
  1976年   1639篇
  1975年   1475篇
  1974年   1402篇
  1973年   1404篇
  1972年   1104篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.

A compelling body of research has found that investments in knowledge from other firms and universities spill over to enhance the performance of entrepreneurial firms. This literature has shown that firm performance is positively related to investments in new knowledge by other firms and research universities. This paper addresses a gap in the literature by positing that public sector knowledge is also conducive to enhancing performance by knowledge intensive entrepreneurial (KIE) firms. Our findings suggest that the public sector provides a fertile source of knowledge for enhancing KIE firm performance.

  相似文献   
64.
Dreissenid mussel veligers compose a substantial component of pelagic biomass in the Great Lakes, yet their dynamics are poorly understood. To evaluate seasonal, spatial, and inter-annual variation in veliger density, we used a 64-μm mesh plankton net (2008, 2013–2016) and a 153-μm mesh plankton net (2007–2016) to collect dreissenid veligers at nearshore (15–25?m depth), transitional (45?m) and offshore (93–110?m) sites in southeast Lake Michigan during March–December. We also evaluated trends in density of recently settled mussels relative to veliger abundance and the density of the standing stock of adult mussels. Veliger density peaked during both summer and fall at all sites, but peak densities in summer were generally higher nearshore, whereas peak densities in the fall were generally higher offshore. The density of veligers in the 153-μm net was overall 28% of that in the 64-μm net, but there was high variability in this comparison among months. Smaller veligers were much more abundant in the 64-μm net, but there was little difference in the size distribution and abundance between nets for the 210–300?μm size classes. Thus, the 153-μm net could still be a useful tool for assessing density trends of larger veligers just prior to their settlement. Newly settled mussels (≤2?mm) were most abundant in summer or fall at the nearshore and offshore sites but were nearly absent at the transitional site despite the high density of veligers there. Factors other than veliger density must play an important role in mussel recruitment.  相似文献   
65.
A defining feature of large-scale retailing during the period 1950–1980 was the emergence and evolution of planned shopping centres. During the 1950s, department stores in the United States were in the vanguard of this phenomenon. In contrast, British department stores continued operating from traditional high street sites, and had limited opportunities for expansion within planned shopping centres until the 1970s. This paper addresses the connection between department store retailing and the development of the planned shopping centre in Britain from the perspective of one enterprise: the John Lewis Partnership. The article demonstrates that the Partnership was willing to operate department stores within centrally located shopping centres, but was circumspect about operating stores in non-centrally located shopping centres.  相似文献   
66.
Advertising situated in environments where people congregate or pass through on their way to somewhere else benefit from being placed in such high traffic areas. However, these strategically placed ads also suffer from conditions of human crowding that prevents them from being noticed and processed. We undertake a study of place-based advertising in a shopping mall using facial recognition software to determine the effect of human density on the attention directed to advertising. We find that as human density increases, attention to advertising decreases, but only to a point where it begins to increase again. Our research also finds that human density plays a moderating role on the motivation to process advertising.  相似文献   
67.
This study examines why most derivatives markets that settle on the day following expiration choose the opening rather than the closing price as the final settlement price (FSP), whereas most markets that settle on the expiration day select an average rather than a single price as the FSP. Four exogenous changes in the Taiwan Futures Exchange settlement procedures provide an experimental basis for studying the settlement procedures’ impact on underlying assets. Greatest market efficiency is observed when the FSP is determined by a single rather than an average price and hypothesize that manipulation is prevented at the expense of market quality.  相似文献   
68.
69.
70.
Hypoxia formation and breakdown were tracked during 2015 in Muskegon Lake estuary at multiple locations, and five years (2011–2015) of time-series buoy observatory data were evaluated for the effect of episodic wind-events on lake mixing. Bi-weekly water temperature and dissolved oxygen (DO) profiles at four locations revealed that hypoxia occurred at all sites and persisted for 2–3 months during summer 2015. On one date in late-summer, up to 24% of the lake’s volume was estimated to be mildly hypoxic (DO < 4 mg L?1) as defined by lake sturgeon requirements. Patterns of wind speed and water column stability in late spring indicated that high winds and low stability delayed the onset of hypoxia while in late summer low winds and high stability delayed degradation of hypoxia. Wind speeds appear to play a great role in the interannual variability of stratification and subsequent hypoxia. Water temperature and DO profiles taken before and after one mid-summer mixing event (wind speed >7.7 m s?1 for 10 h), indicated that while the wind was unable to completely mix the entire water column, it deepened the epilimnion by ~1.5 m and sheared a thin layer from the upper hypolimnion. By entraining internally loaded nutrients, such episodic wind-events may initiate and sustain algal blooms in nutrient limited surface waters. Quantifying the variable role of wind and mixing events will be key to integrating limnological processes into climate models of the future.  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