全文获取类型
收费全文 | 35949篇 |
免费 | 839篇 |
国内免费 | 3篇 |
专业分类
财政金融 | 6025篇 |
工业经济 | 2453篇 |
计划管理 | 5507篇 |
经济学 | 7376篇 |
综合类 | 370篇 |
运输经济 | 218篇 |
旅游经济 | 546篇 |
贸易经济 | 5062篇 |
农业经济 | 1570篇 |
经济概况 | 4176篇 |
水利工程 | 3417篇 |
邮电经济 | 71篇 |
出版年
2021年 | 233篇 |
2020年 | 353篇 |
2019年 | 501篇 |
2018年 | 733篇 |
2017年 | 686篇 |
2016年 | 688篇 |
2015年 | 490篇 |
2014年 | 747篇 |
2013年 | 3446篇 |
2012年 | 1142篇 |
2011年 | 1169篇 |
2010年 | 827篇 |
2009年 | 973篇 |
2008年 | 1109篇 |
2007年 | 1146篇 |
2006年 | 1101篇 |
2005年 | 1042篇 |
2004年 | 1039篇 |
2003年 | 785篇 |
2002年 | 728篇 |
2001年 | 722篇 |
2000年 | 698篇 |
1999年 | 618篇 |
1998年 | 603篇 |
1997年 | 577篇 |
1996年 | 575篇 |
1995年 | 519篇 |
1994年 | 567篇 |
1993年 | 554篇 |
1992年 | 548篇 |
1991年 | 569篇 |
1990年 | 524篇 |
1989年 | 456篇 |
1988年 | 440篇 |
1987年 | 447篇 |
1986年 | 441篇 |
1985年 | 659篇 |
1984年 | 607篇 |
1983年 | 618篇 |
1982年 | 611篇 |
1981年 | 524篇 |
1980年 | 508篇 |
1979年 | 513篇 |
1978年 | 451篇 |
1977年 | 397篇 |
1976年 | 341篇 |
1975年 | 309篇 |
1974年 | 286篇 |
1973年 | 269篇 |
1972年 | 210篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Fast and flexible storage capacity will become more important in a liberalised gas market. For this reason Trianel, together with other partners, has decided to build a gas cavern facility in Epe. The typical operation of a gas cavern is peak-shaving. In contrast this article shows the economic possibilities of the cavern to establish a full swing supply. 相似文献
993.
Perpetual growth requires offsetting diminishing returns to reproducible factors of production. In this article we present a theory of factor elimination. For simplicity and clarity, there is no augmentation of non-reproducible factors, thus excluding the standard engine of growth. By spending resources on R&D, agents learn to change the exponents of a Cobb–Douglas production function. We obtain the economy's balanced growth path and complete transition dynamics. The theory provides a mechanism for the transition from an initial technology incapable of supporting perpetual growth to one with constant returns to reproducible factors that supports it. 相似文献
994.
Shiri M. Breznitz Rory P. O'Shea Thomas J. Allen 《Journal of Product Innovation Management》2008,25(2):129-142
To analyze university contribution to economic development, the present study examines universities' technology transfer policies and their associated economic development impact. The article examines how a university defines itself as part of a region as well as what activities, if any, do university commercialization strategies in context of their regional environment affect spin‐off activity. Furthermore, this study explores the ways universities contribute to regional economic development by examining existing theories and analyzing universities' relationships with both government and industry in two regions. This study draws from Roberts and Malone's (1996) selectivity–support typology and highlights this article's argument by comparing the commercialization strategies of world‐class universities strategies in the development of regional biotechnology clusters in Massachusetts and in Connecticut. This article investigates the notion of whether universities can differently influence the economic development processes of the while still having successful commercial outcomes. These findings build on previous research ( Clarysse et al., 2005; Degroof and Roberts, 2004; Powers and McDougall, 2005 ), which argues that low support–low selectivity policies may be more suitable to entrepreneurially developed environments, whereas high support–high selectivity policies are more efficient in entrepreneurially underdeveloped environments. Masachusetts Institute of Technology (MIT) is located in a strong technopole region, whereby many of its support structures for spin‐off formation are provided by the regional infrastructure of the Cambridge–Boston region. In contrast, Yale University, which has an underdeveloped entrepreneurial context, has had to take a more proactive role in providing incubation capabilities to their spin‐off projects. This finding supports a contingent based perspective of academic entrepreneurship, whereby low support–low selectivity policies are more fitted to entrepreneurially developed environments, whereas high support–high selectivity policies are more efficient in entrepreneurially underdeveloped environments. 相似文献
995.
Rupak Rauniar William Doll Greg Rawski Paul Hong 《International Journal of Production Economics》2008,114(2):723
Product development processes based on the joint collaboration of the cross-functional team, suppliers, and customers can minimize project glitches. Glitches in the product development project can cause project cost over-runs and delay a project past when first mover advantages are possible. While previous theoretical work has suggested a negative relationship between shared knowledge and product development glitches, empirical studies have not identified how different types of shared knowledge are associated with each other and the design glitches. This study proposes a model of the relationship between specific types of shared knowledge and design glitches in integrated product development (IPD) projects. We test our model using a sample of 191 projects from the automotive industry in the United States. The major findings were that: (1) shared knowledge of the development process can be built by improving a team's shared knowledge of customers, suppliers, and internal capabilities, (2) shared knowledge of the development process for a project reduces product design glitches, and (3) reduced product design glitches improve product development time, cost, and customer satisfaction. 相似文献
996.
Environmental flows are now a standard part of sustainable water management globally but are only rarely implemented. One reason may be insufficient engagement of stakeholders and their priority outcomes in the environmental flow‐setting process. A recent environmental flow assessment (EFA) in the Kilombero basin of the Rufiji River in Tanzania concentrated on a broad‐based investigation of stakeholders' use and perceptions of the ecosystem services provided by the river as a framework for the assessment of flow regimes that would maintain them. The EFA process generally followed the Building Block Methodology but within an enhanced stakeholder engagement framework. Engagement began with the involvement of institutional stakeholders to explain the purpose of the EFA and to elicit their priority outcomes. Extensive interactions with direct‐use stakeholders followed to investigate their uses of and priorities for the rivers. Results were used by the EFA specialist team in choosing flow indicators and defining measurable environmental objectives. The specialists then met to reach a consensus of the flow requirements. The EFA results were lastly reported back to stakeholders. During the Kilombero EFA, we learned that stakeholders at all levels have a good awareness of the natural services provided by a healthy river and can contribute to the setting of environmental objectives for the rivers and floodplain. These can be factored into the biophysical assessments of river flows required to maintain habitats, processes, water quality, and biodiversity. It is therefore important to allocate significant resources to stakeholder engagement. It now remains to be seen if enhanced stakeholder engagement, including the increased understanding and capacity built among all stakeholders, will increase support for the implementation of the recommended flows. 相似文献
997.
Poverty Traps and Index-Based Risk Transfer Products 总被引:1,自引:0,他引:1
998.
This paper develops and estimates models of family and sex-specific emigration, as well as the sex composition of this emigration, from 12 European source countries to the U.S. for the period 1870–1910. The models are based on the distinction between economic migrants (males, single females, and some married females) and tied or trailing migrants (females) and are estimated with panel data, including data that relate to the occupational/industrial structure of male and female economic activity in source countries. Hausman-Taylor instrumental variable estimates suggest that although both males and females responded to labor-market signals, males were more responsive than females to per capita GDP differences. Moreover, compared to the rest of Europe, Ireland, and Scandinavia were the sources of many young, single male, and female migrants, who responded strongly to gaps in economic opportunities. In fact, much of the European response to such gaps appears to be due to migrants from Ireland and Scandinavia. Females tended to originate in English-speaking countries and countries that were agriculturally oriented. Service and manufacturing jobs in source countries discouraged the migration of females relative to males. Males tended to follow recent migrants more than females, but females responded more to long-term influences as measured by stocks of migrants from their source countries who had previously settled in the U.S. Countries with high birth rates had relatively fewer female emigrants, whereas those with high rates of natural increase 20 years earlier experienced relatively more male emigration. Intact families, other family members (including family-strategy male migrants and trailing female migrants), and single males and females responded strongly to economic incentives, but the singles were most responsive followed by family-strategy males. 相似文献
999.
Mangrove forests as a nature-based solution for coastal flood protection: Biophysical and ecological considerations 下载免费PDF全文
Rosanna van Hespen Zhan Hu Bas Borsje Michela De Dominicis Daniel A. Friess Svetlana Jevrejeva Maarten G. Kleinhans Maria Maza Celine E. J. van Bijsterveldt Tom Van der Stocken Bregje van Wesenbeeck Danghan Xie Tjeerd J. Bouma 《水科学与水工程》2023,16(1):1-13
Nature-based coastal protection is increasingly recognised as a potentially sustainable and cost-effective solution to reduce coastal flood risk. It uses coastal ecosystems such as mangrove forests to create resilient designs for coastal flood protection. However, to use mangroves effectively as a nature-based measure for flood risk reduction, we must understand the biophysical processes that govern risk reduction capacity through mangrove ecosystem size and structure. In this perspective, we evaluate the current state of knowledge on local physical drivers and ecological processes that determine mangrove functioning as part of a nature-based flood defence. We show that the forest properties that comprise coastal flood protection are well-known, but models cannot yet pinpoint how spatial heterogeneity of the forest structure affects the capacity for wave or surge attenuation. Overall, there is relatively good understanding of the ecological processes that drive forest structure and size, but there is a lack of knowledge on how daily bed-level dynamics link to long-term biogeomorphic forest dynamics, and on the role of combined stressors influencing forest retreat. Integrating simulation models of forest structure under changing physical (e.g. due to sea-level change) and ecological drivers with hydrodynamic attenuation models will allow for better projections of long-term natural coastal protection. 相似文献
1000.
Pikeperch,Sander lucioperca Invasion in the Neretva River Watershed (Bosnia and Herzegovina,Croatia) After Alteration of River Flow 下载免费PDF全文
J. Pavličević L. Glamuzina A. Conides N. Savić I. Rozić D. Klaoudatos A. Kazić B. Glamuzina 《河流研究与利用》2016,32(5):967-974
The invasion history and the recent distribution, abundance and prey composition of pikeperch, Sander lucioperca in Neretva River watershed (Bosnia and Herzegovina and Croatia) are presented. The species was illegally/unintentionally introduced in Ramski Reservoir in the upper river part in 1986, while establishment of its abundant populations was reported during the 1990s in two connected artificial reservoirs. The research on the present abundance and food composition was executed during the 2012–2014 period. The results showed that pikeperch occupied most of the water bodies of the Neretva River, with an exception of natural river parts with gravel sediment and fast flow: all five artificial reservoirs (Ramski, Jablani?ki, Grabovica, Salakovac and Mostarski reservoirs) and lower wetland zone. However, the success and impact of colonization differ among water bodies, indicating pikeperch preference for warm and shallow reservoirs. Pikeperch prey is composed of different fish species abundant in specific water bodies. In artificial reservoirs, it preys mostly on introduced fish species, with a potential for controlling pumpkinseed abundance and biomass. Sampling carried out in Ramski Reservoir between 2013 and 1014 showed exclusive feeding on the introduced Leucaspius delineatus, and the establishment of a new food web, where only introduced species play significant roles. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献