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   76篇
  免费   8篇
  2023年   1篇
  2020年   1篇
  2019年   7篇
  2018年   5篇
  2017年   7篇
  2016年   9篇
  2015年   3篇
  2014年   3篇
  2013年   22篇
  2012年   3篇
  2011年   1篇
  2010年   2篇
  2009年   5篇
  2004年   1篇
  2003年   1篇
  2002年   1篇
  1993年   1篇
  1992年   1篇
  1987年   1篇
  1985年   2篇
  1984年   1篇
  1983年   2篇
  1980年   2篇
  1974年   1篇
  1969年   1篇
排序方式: 共有84条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
25.
Goat and Cows     
  相似文献   
26.
Microfossils which are hollow, possess a two-layered vesicle wall, and occur as single elements or, more rarely, as compound forms, have been recovered from the Early Cambrian Heatherdale Shale, on the Fleurieu Peninsula, South Australia. The microfossils, which range in size from 4 to 14.5 μm, are informally and tentatively assigned to the genus Sphaerocongregus Moorman 1974. Superficially they resemble forms assigned to Pyritosphaera Love 1958 and its probable junior synonym, Bavlinella Shepeleva 1962. Topotypes of these genera, however, have yet to be studied using SEM techniques, and their morphologic details remain uncertain. The organic composition of the present microfossils is supported by energy-dispersive X-ray analyses. Samples of the Heatherdale Shale were also analysed using pyrolysis techniques; the organic matter is, however, over-mature with respect to petroleum generation, and no geochemical assessment of original kerogen type is possible.  相似文献   
27.
During the five years before the outbreak of the First World War, Thomas Graham Brown (1882–1965) conducted research into the control of locomotion that gained him a deserved and long-lasting reputation as a neuroscientist and, in 1927, was recognized by election to the Fellowship of the Royal Society. In 1915, with the First World War raging, he agonized about continuing his research or joining the Royal Army Medical Corps (RAMC). Told by his father to seek a commission, he served two and half years in Macedonia with the British Salonika Force. Whilst in Greece, he kept a daily diary. The entries from June 1916 to May 1917 are extant. They are unpublished and provide the background to the narrative to follow. Casualties with traumatic injury to the brain and spinal cord afforded him the opportunity to carry out careful observations, particularly concerning sensory localization, which resulted in novel findings and his observations on shell shock led to him being called as an expert witness to the national inquiry into the nature and treatment of the condition. In 1920, Graham Brown was appointed to the Chair of Physiology in Cardiff, which he held until 1947.  相似文献   
28.
29.
30.
An experimental approach has been used to establish whether medieval ironworking activity could be identified in peat bogs using mineral magnetic measurements. The research project comprised three elements. First, magnetic susceptibility and remanence properties were obtained for materials from an experimental iron smelt, in a furnace of medieval design, and from material collected during the excavation of the medieval bloomery at Llwyn Du in Coed y Brenin, Snowdonia. Materials sampled and measured included charcoal, aerial dust, roasted bog ore and furnace dust. A second experiment determined whether small amounts of aerial dust released from the furnace could be detected in accumulating peat samples. This was achieved by sprinkling small quantities of dust on to a constructed ’peat core’ that had no detectable magnetic signature prior to the addition of the dust. The application rates used were within the range expected to fall on a peat bog located close to a medieval furnace. Thirdly, mineral magnetic measurements were made on a peat core collected close to the Llwyn Du bloomery. The results confirm that roasted bog ore, aerial dust released from and dust accumulating in the furnace after a smelt, are magnetically detectable. The aerial dust and roasted bog ore produced enhanced susceptibility and remanence signatures in the constructed ’peat core’ experiments. Peaks in IRM(0.88T) and HIRM were measured in the Llwyn Du peat monolith and appear to correlate with a time when the medieval bloomery was operational. The results presented here suggest that it is possible to identify evidence of past ironworking in peat bogs using mineral magnetic measurements and that the signatures remain well preserved in the peat record even after burial for several hundred years.  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