全文获取类型
收费全文 | 133篇 |
免费 | 11篇 |
出版年
2023年 | 3篇 |
2021年 | 1篇 |
2020年 | 5篇 |
2019年 | 10篇 |
2018年 | 11篇 |
2017年 | 9篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 1篇 |
2013年 | 42篇 |
2012年 | 6篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 2篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1986年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有144条查询结果,搜索用时 482 毫秒
11.
12.
Jacob I. Ricks 《Development and change》2017,48(3):567-589
Why does a state build institutional capacity in certain sectors rather than others? Despite having gained leverage explaining the emergence of institutions in the developmental states of East Asia, we have comparatively weak accounts for sub‐national variation in institutional strength, a much more common phenomenon. Investigating the surprising achievements of the Philippines’ National Irrigation Administration, this article advances a theory of sectoral success in the face of a generally poor developmental record. The author demonstrates that executives will only construct institutional capacity when facing strong political pressure combined with resource scarcity. Such vulnerability permits politicians to exercise discretion in choosing which policies to pursue, allowing them to avoid upsetting their coalitions. Once a politician achieves some degree of policy success, he or she is then able to avoid engaging in similar reforms in other fields. Thus we see pockets of institutional capacity in states that otherwise struggle with developmental tasks. 相似文献
13.
Molding maize: the shaping of a crop diversity landscape in the western highlands of Guatemala 总被引:2,自引:0,他引:2
Today's domesticated plants not only embody past human–nature interactions, but also reflect social history. Human seed exchange, replacement and loss are important forces in shaping crop diversity. This essay explores regional history in relation to the shaping of maize diversity in the western highlands of Guatemala. This is an area of exceptional maize heterogeneity and a peripheral part of the region where maize was domesticated. Maize diversity seems to have developed through geographic isolation in networks of seed exchange that were generally very local in scope. However, recent studies on Mexican maize suggest otherwise. However, few studies have examined crop diversity or seed exchange from a historical perspective. A closer examination of regional history suggests which processes might be important for shaping the present geographical distribution of maize diversity. Seeds were occasionally transported over longer distances. As a consequence, maize diversity is geographically not characterised by sharp differences between farming communities; the main differences are to be found in regional occurrences. This challenges antimodern ideas of closed, local native ecologies. Consequently, the conservation of maize genetic resources is a challenge, but not entirely contradictory with its transforming socio-economic context. 相似文献
14.
15.
16.
17.
Giedre Motuzaite-Matuzeviciute Jérémy Jacob Sergey Telizhenko Martin K. Jones 《Archaeological and Anthropological Sciences》2016,8(1):43-50
During the archaeobotanical investigation of Scythian–Sarmatian period (Early Iron Age), pits with crop processing waste, discovered in the floodplain of Donets River, eastern Ukraine, and charred remains of cereal grains, dominated by broomcorn millet, were recorded. The grains from the pits were radiocarbon dated to the fifth to first century BC. Those pits are distant from any known contemporaneous settlement. The apparent disconnection of these pits from any local settlement suggests that (1) millet was brought from other locations by mobile groups, or (2) millet was cultivated locally by populations whose settlements have left no discernible archaeological trace. The analysis of molecular biomarkers preserved in palaeosols that are stratigraphically connected to the pits revealed high levels of miliacin, a molecule that can be preserved in ancient soils and sediments, and that is consistent with broomcorn millet (Panicum miliaceum). High levels in miliacin in soils stratigraphically connected to the pits are interpreted as the result of a large biomass of P. miliaceum produced at time of soil formation. Our biogeochemical results applied to a palaeosol thus attest to the in situ cultivation of crops dominated by the broomcorn millet during the early Iron Age in the floodplain of Donets River. Biochemical examination of soils and palaeosols can thus provide useful information on past dynamics of land-use by ancient population, especially when settlements or macrobotanical remains are absent. 相似文献
18.
Although sickle blades gloss is known to form during the harvest, which is a dynamic process and although it is known to be a type of wear which is the outcome of the repetitive encounters between the sickle blades working edges and plant stems; there is no common way to quantify its intensity. Since there is no consensus over a specific scale that will enable the estimation of the amount of wear, based on the quantification of gloss brightness intensity. In this paper we propose a new measurement system which is based on the projection of laser (He–Ne) beam on glossed sickle blades and an analysis of the reflected images. The results form a relative scale from which it is possible to infer on the sickle blades level of wear, and to create discard models. 相似文献
19.
20.
Andrew A. Meharg Kevin J. Edwards J. Edward Schofield Andrea Raab Joerg Feldmann Annette Moran Charlotte L. Bryant Barry Thornton Julian J.C. Dawson 《Journal of archaeological science》2012,39(3):717-727
Tin, as a constituent of bronze, was central to the technological development of early societies, but cassiterite (SnO2) deposits were scarce and located distantly from the centres of Mediterranean civilizations. As Britain had the largest workable ore deposits in the ancient Western world, this has led to much historical speculation and myth regarding the long-distance trading of tin from the Bronze Age onwards. Here we establish the first detailed chronology for tin, along with lead and copper deposition, into undisturbed ombrotrophic (rain-fed) peat bogs located at Bodmin Moor and Dartmoor in the centre of the British tin ore fields. Sustained elevated tin deposition is demonstrated clearly, with peaks occurring at 100–400 and 700–1000 calendar years AD – contemporaneous with the Roman and Anglo-Saxon periods respectively. While pre-Roman Iron Age tin exploitation undoubtedly took place, it was on a scale that did not result in convincingly enhanced deposition of the metal. The deposition of lead in the peat record provides evidence of a pre-Roman metal-based economy in southwest Britain. Emerging in the 4th century BC, this was centred on copper and lead ore processing that expanded exponentially and then collapsed upon Roman colonization during the 1st century AD. 相似文献