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   6篇
  免费   0篇
现状及发展   3篇
综合类   3篇
  2006年   1篇
  2005年   1篇
  1996年   1篇
  1967年   2篇
  1966年   1篇
排序方式: 共有6条查询结果,搜索用时 15 毫秒
1
1.
2.
We have found that almost all paper documents, plastic cards and product packaging contain a unique physical identity code formed from microscopic imperfections in the surface. This covert 'fingerprint' is intrinsic and virtually impossible to modify controllably. It can be rapidly read using a low-cost portable laser scanner. Most forms of document and branded-product fraud could be rendered obsolete by use of this code.  相似文献   
3.
Résumé Une analyse a été fait des substances que perdent les cellules deStaphylococcus aureus chauffées à 50 °C et 60 °C. Ces substances comprennent des acides aminés, de la proteine et des substances absorbantes à une longeur d'onde de 260 nm.  相似文献   
4.
5.
Stromatolite reef from the Early Archaean era of Australia   总被引:3,自引:0,他引:3  
Allwood AC  Walter MR  Kamber BS  Marshall CP  Burch IW 《Nature》2006,441(7094):714-718
The 3,430-million-year-old Strelley Pool Chert (SPC) (Pilbara Craton, Australia) is a sedimentary rock formation containing laminated structures of probable biological origin (stromatolites). Determining the biogenicity of such ancient fossils is the subject of ongoing debate. However, many obstacles to interpretation of the fossils are overcome in the SPC because of the broad extent, excellent preservation and morphological variety of its stromatolitic outcrops--which provide comprehensive palaeontological information on a scale exceeding other rocks of such age. Here we present a multi-kilometre-scale palaeontological and palaeoenvironmental study of the SPC, in which we identify seven stromatolite morphotypes--many previously undiscovered--in different parts of a peritidal carbonate platform. We undertake the first morphotype-specific analysis of the structures within their palaeoenvironment and refute contemporary abiogenic hypotheses for their formation. Finally, we argue that the diversity, complexity and environmental associations of the stromatolites describe patterns that--in similar settings throughout Earth's history--reflect the presence of organisms.  相似文献   
6.
1
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