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   136篇
  免费   4篇
  2023年   9篇
  2022年   1篇
  2020年   14篇
  2019年   6篇
  2018年   15篇
  2017年   12篇
  2016年   12篇
  2015年   6篇
  2014年   13篇
  2013年   23篇
  2012年   11篇
  2011年   11篇
  2010年   2篇
  2008年   2篇
  2005年   1篇
  1999年   1篇
  1994年   1篇
排序方式: 共有140条查询结果,搜索用时 46 毫秒
71.
In this paper I try to explain why the potassium-argon dating method was developed much later than other radiometric methods (like U-He and U-Pb), which were established at the beginning of the 20th century. In fact the pioneering paper by Aldrich and Nier (1948) was published 50 years after the discovery of polonium and radium, when nearly all the details concerning potassium isotopes and radioactivity of potassium-40 had been investigated. The role of Marie Curie’s concept of the nature of radioactivity in the discovery of the radioactivity of potassium is emphasized.  相似文献   
72.
Metasequoia glyptostroboides is considered to be a species highly resistant to harmful environmental factors. For this reason it has been introduced to the cities. The climate of Krakow differs from that in its natural range in China. The research was focused on 40-year-old trees, planted in Kraków on fertile alluvial soils with a low level of ground water, in the vicinity of the steelworks. During the period of the highest level of air pollution in the 1970s and 1980s, the radial increment of investigated trees showed an increasing trend. At the end of the 1980s, when the emissions were reduced, a decreasing trend in radial growth was recorded. Throughout the entire period of their life the investi-gated trees have shown high homogeneity of short-term growth reactions. The sensitivity chronology of the trees was characterized by a high representativeness and a strong high-frequency signal. This may indicate that the investigated trees have shown a large sensitivity to climatic factors. The positive effect on the radial growth of Metasequoia had a cold September in the previous year, and also a cold January, April and May in the year of ring formation. Positive impact on the growth of trees had also the high precipitation occurring in April and August, as well as high air humidity in the spring of the year of ring formation. In the period 1974–2011 fifteen signature years were found. The analysis of the climatic conditions in these years confirms the results of the statistical analyses.  相似文献   
73.
The thermoluminescence (TL) dating method has a significant measurement error margin reaching almost 10%. Due to this fact it could be considered as little effective in case of such sites from the Roman period as burial grounds with many artefacts useful for archaeological dating. However, for many settlements from this period, where pottery is the only kind of artefacts, the TL method can give notable results. The main purpose of the study was to make an attempt at TL dating of pottery and clay daub samples from the Nieszawa Kolonia and Kręcieszki sites and to compare the obtained dates with the results of archaeological dating of selected features from the Przeworsk Culture settlements. In the Kręcieszki site the fragments of burnt clay daub were dated by the TL method for the first time in the Lublin laboratory. It turned out that clay daub is an equally good dating material as pottery. It can be found that the TL dating of pottery from Nieszawa Kolonia confirms two stages of settlement. The first settlement stage is related to the phases B2-B2/C1-C1a of the Roman period, i.e. from the beginning of the 2nd to the beginning of the 3rd century. The second group of TL dates corresponds to the phases C2D that is to the second stage of settlement, from the second half of the 3rd century to the half of the 5th century AD. The results of TL dating of pottery and clay daub in the Kręcieszki site are rather similar and correspond to the phase B1/B2 of the period of Roman influence, determined from pottery style, but can also indicate the phase B2/C1.  相似文献   
74.
75.
76.
The Port‐Vendres 4 shipwreck is evidence of coastal export trade between Hispania Citerior and Narbonne in 40/30 BC. The cargo is made up of a particular assemblage of Roman wine amphoras (Pascual 1, Dressel 1B and Lamboglia 2) destined for Gallic markets. Archaeological and archaeometric analyses conducted on a selection of the amphoras allowed the provenance of the cargo to be identified as Hispania Citerior and the central‐southern Tyrrhenian coast of Italy. Iluro and/or Baetulo are proposed as the ports of departure, enabling the reconstruction of the trade route and the historical and economic significance of this shipwreck.  相似文献   
77.
This article aims to compare the biographical experiences and individual memories of child deportees and migrants from Eastern Europe. The analysis is based on a field study of over 100 biographical interviews in two local communities situated in the borderland regions which were particularly exposed to post-war displacement, resettlement and population exchange: Ukrainian Galicia and Western Poland. The author claims that although the history of these two distant communities was totally different, contemporary memory of being a refugee/deportee/forced migrant, losing one's home/homeland and watching the deportation of the previous inhabitants of one's new place of residence bear many similarities. While analysing autobiographical narratives, I attempt to find common threads and topics generated by their experiences as children, as well as explain the differences by exploring the social context of individual memory, with a special accent on post-war socialisation and the Polish and Ukrainian memory culture. The author also strives to show how and why the children's memories differ from those of their parents.  相似文献   
78.
The paper concerns an interaction problem between soil and masonry vaults in historic buildings. A particular emphasis was placed on the influence of finishing method of vaults extrados and fill material properties on the behavior of masonry vaults. The results of experimental studies on barrel vaults with and without backfill are presented. During the experiments three finishing methods of vaults extrados and three fill materials were investigated. The results of the experiments show that the presence of backfill and type of vaults extrados finish affect the behavior and load-carrying capacity of tested elements. Moreover, tests were performed on vaults without fill for comparative purposes. The comparison of experimental results obtained for specimens with and without fill shows that the presence of backfill in vault haunches modifies the failure mechanism and increases load capacity of the analysed models. The presented results confirm the importance of backfill as a structural element of vaulted structures.  相似文献   
79.
Following a strictly theory-building approach, we developed an agent-based simulation model, the Nice Musical Chairs model, to represent the competition between groups of stakeholders of farming and herding activities in the arid Afro-Eurasia. The model deepens the questions raised by the results of our former model, the Musical Chairs model, and further introduces three socio-economic mechanisms, which modulate the behavior and performance of stakeholders and their groups. First, we define land use pairing as the awarding, regarding productivity, of any direct cooperation between farming and herding within a group. Second, group management is modeled as the prerogative of a group leadership to manage stakeholders to pursue a particular proportion between farming and herding. Third, we introduce restricted access to pasture as the engagement in territorial control of rangelands in opposition to an open access regime. An exhaustive exploration of scenarios and parameters placed the control over rangelands as the most significant factor in the formation of land use patterns, followed by land use management. While the effect of land use pairing is mild in comparison, it is still a significant factor in group selection and thus in the persistence of particular land use patterns in the long run.  相似文献   
80.
As what happened for thenova in 1604 and for the three comets which appeared in 1618 starting the debate between Galileo and the Jesuits of the Roman College, even the comet of 1644 enhanced the curiosity and expectations in astrometers’ and astrologers’ minds. This work focuses on some aspects of the European debate, by fixing our attention on the Bolognese observatory school of Santa-Lucia in particular, where Giovan Battista Riccioli and his socios had started an experimental activity which was known and appreciated for its accuracy all over Europe. It also closely examines the revaluation of the «medium sciences», such as geography and hydrometry, to point out the sociocultural conditions that originated the growth of new professional characters like engineers and technicians in Bologna.  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