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   175篇
  免费   18篇
  2023年   7篇
  2022年   1篇
  2021年   1篇
  2020年   6篇
  2019年   8篇
  2018年   17篇
  2017年   18篇
  2016年   11篇
  2015年   10篇
  2014年   6篇
  2013年   34篇
  2012年   5篇
  2011年   6篇
  2010年   11篇
  2009年   11篇
  2008年   4篇
  2007年   4篇
  2006年   4篇
  2005年   2篇
  2003年   3篇
  2002年   4篇
  2001年   3篇
  1999年   1篇
  1998年   2篇
  1997年   1篇
  1991年   1篇
  1988年   1篇
  1987年   1篇
  1983年   1篇
  1982年   3篇
  1981年   1篇
  1978年   1篇
  1975年   1篇
  1974年   1篇
  1969年   1篇
  1949年   1篇
排序方式: 共有193条查询结果,搜索用时 15 毫秒
181.
182.
183.
In this paper we report on Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) of a sample of ceramics from Nasca, Peru collected by Alfred Kroeber in the 1920’s and curated at the Field Museum of Natural History in Chicago. The analysis was conducted for two principal reasons: (1) to test the efficacy of LA-ICP-MS when compared to INAA; and (2) to evaluate samples that post-date Early Nasca (where focus has primarily been placed). We show here that LA-ICP-MS is a viable alternative to INAA, present some of the compositional variability in the Kroeber samples, and propose some explanations for this variability.  相似文献   
184.
Siversson, M., Cook, T.D., Ryan, H.E., Watkins, D.K., Tatarnic, N.J., Downes, P.J. & Newbrey, M.G. May 2018. Anacoracid sharks and calcareous nannofossil stratigraphy of the mid-Cretaceous Gearle Siltstone and Haycock Marl in the lower Murchison River area, Western Australia. Alcheringa XX, XX–XX.

Extensive bulk sampling over the past 20 years and greatly improved stratigraphic control permitted a meaningful revision of previously described anacoracid sharks from the ‘upper’ Gearle Siltstone and lower Haycock Marl in the lower Murchison River area, Western Australia. Isolated teeth of anacoracids are rare in the lower three (Beds 1–3) of four stratigraphic units of the ‘upper’ Gearle Siltstone but relatively common in the uppermost layer (Bed 4) and in the lower part of the overlying Haycock Marl. On the basis of calcareous nannofossils, Beds 1 and 2 of the ‘upper’ Gearle Siltstone can be placed in the uppermost upper Albian calcareous nannofossil Subzone CC9b whereas Bed 3 can be referred to the lowermost Cenomanian CC9c Subzone. Bed 1 yielded fragments of strongly serrated anacoracid teeth as well as a single, smooth-edged tooth. The samples from Beds 2 and 3 contained a few small fragments of serrated anacoracid teeth. Bed 4 is barren of calcareous nannofossils but the presence of a dentally advanced tooth of the cosmopolitan lamniform genus Cretoxyrhina in combination with the age of the overlying Haycock Marl indicate deposition within the younger half of the Cenomanian. The unit produced teeth of two anacoracids; Squalicorax acutus sp. nov. and S. bazzii sp. nov. The basal, laminated part of the Haycock Marl is placed in the uppermost upper Cenomanian part of CC10b. It yielded Squalicorax mutabilis sp. nov. and S. aff. S. bernardezi. Exceptionally well-preserved teeth of the former species span a 5:1 size ratio range for teeth of comparable jaw position. The teeth reveal strong ontogenetic heterodonty with a large increase in the relative size of the main cusp with age and the transition from a vertical distal heel of the crown in very young juveniles to a sub-horizontal, well demarcated heel in ‘adult’ teeth. An isolated phosphatic lens in the lower part of the Haycock Marl produced calcareous nannofossils indicative of the CC10b SubZone, most likely the lowermost lower Turonian part. It contains teeth of Squalicorax mutabilis sp. nov., S. aff. S. bernardezi, and S. sp. C.

Mikael Siversson* [], Helen E. Ryan [] and Peter Downes [] Department of Earth and Planetary Sciences, Western Australian Museum, 49 Kew Street, Welshpool, Western Australia 6106, Australia; David K. Watkins [] Department of Earth and Atmospheric Sciences, University of Nebraska, Lincoln, NE 68588, USA; Todd D. Cook [] School of Science, Penn State Behrend, 4205 College Drive, Erie, PA 16563, USA; Nikolai J. Tatarnic? [] Department of Terrestrial Zoology, Western Australian Museum, 49 Kew Street, Welshpool, Western Australia 6106, Australia; Michael G. Newbrey? [] Department of Biology, Columbus State University, Columbus, GA 31907-5645, USA. *Also affiliated with: School of Molecular and Life Sciences, Curtin University, Kent Street, Bentley, WA 6102, Australia. ?Also affiliated with: Centre for Evolutionary Biology, University of Western Australia, Crawley, Western Australia 6009. ?Also affiliated with: Canadian Fossil Discovery Centre, 111-B Gilmour Street, Morden, Manitoba R6 M 1N9, Canada.

http://zoobank.org/urn:lsid:zoobank.org:pub:97D5131F-C0D5-4A7E-9C9A-0FDF13BFCBBB

http://zoobank.org/urn:lsid:zoobank.org:act:5977DCC2-355C-4732-8B0A-4BD0EABBA8DE

http://zoobank.org/urn:lsid:zoobank.org:act:2D7C4147-B756-4434-847A-B0C1C6D167DF

http://zoobank.org/urn:lsid:zoobank.org:act:33F3B55E-41E0-45B3-8296-A3B95C17B41D  相似文献   

185.
186.
ABSTRACT

This paper presents the results of integrated geoarchaeological and archaeobotanical analyses of desiccated and charred ovicaprid dung pellets from the New Kingdom pharaonic settlement of Amara West (Sudan). These analyses reveal diagnostic phytolithic evidence for considerable variations in plant diet amongst the site’s ovicaprid population. These data shed light on aspects of ancient animal husbandry practice, the settlement’s subsistence economy and residents’ exploitation of natural resources. We also observe that specific phytolith types correlate with the presence (and quantity) or absence of calcium carbonate faecal spherulites in analysed dung pellets. This evidence, augmented by experimental analysis of analogous modern plant material, suggests that dietary Ca intake is implicated in faecal spherulite crystallization within the ovicaprid digestive system.  相似文献   
187.
188.
ABSTRACT

Listed events are policies enacted by states to protect the free-to-air rights of specific television and radio broadcasts that are identified as being of particular national significance. Some states (including the UK, Belgium, and Argentina) have begun to adopt these listed events policies, typically regarding significant national sporting events. We re-conceptualize listed events as a practical means by which to protect the intangible cultural heritage of states – an issue addressed by international institutions such as ICOMOS and UNESCO. Furthermore, we engage in a critical analysis regarding both the merits and potential problems involved in the possibility of Canada adopting listed broadcasting events policies, specifically involving hockey broadcasts.  相似文献   
189.
190.
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