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   235篇
  免费   5篇
  国内免费   4篇
安全科学   12篇
废物处理   14篇
环保管理   10篇
综合类   80篇
基础理论   53篇
污染及防治   54篇
评价与监测   15篇
社会与环境   5篇
灾害及防治   1篇
  2023年   3篇
  2022年   3篇
  2021年   6篇
  2020年   11篇
  2019年   5篇
  2018年   9篇
  2017年   5篇
  2016年   11篇
  2015年   16篇
  2014年   11篇
  2013年   16篇
  2012年   16篇
  2011年   13篇
  2010年   12篇
  2009年   9篇
  2008年   12篇
  2007年   20篇
  2006年   13篇
  2005年   9篇
  2004年   7篇
  2003年   11篇
  2002年   7篇
  2001年   2篇
  1999年   4篇
  1998年   3篇
  1997年   1篇
  1995年   1篇
  1994年   1篇
  1993年   4篇
  1991年   1篇
  1988年   1篇
  1978年   1篇
排序方式: 共有244条查询结果,搜索用时 15 毫秒
241.
New dental remains of listriodont suids are described from the lower member of the early to middle Miocene Vihowa Formation of the Bugti Hills, Pakistan. The material is homogeneous in terms of morphology and dimensions and referred as a whole to Listriodon guptai Pilgrim, 1926. This species is also mentioned in coeval deposits of the Zinda Pir Dome, Pakistan, dating back to ca. 19 Ma. The early occurrence of an advanced listriodont in Pakistan constrains the age of acquisition of several characters correlated to lophodonty within Listriodontini, and raises major questions about the early history of the Old World Listriodontinae. Strong morphological similarity between Listriodon guptai and the African species Listriodon akatikubas found in the late early Miocene of Maboko (Kenya, ca. 16.5 Ma) suggests that this latter is most probably a migrant originating from Asia.  相似文献   
242.
Observations of dental microwear are used to analyse the correlation between changes in molar tooth crown morphology and the direction of masticatory movement during the evolution of Myodonta (Rodentia, Mammalia). The studied sample includes 36 specimens representing both superfamilies of Myodonta (Muroidea and Dipodoidea) spanning 16 dipodoid and 9 muroid species. Microscopic scratches on occlusal surfaces resulting from contact between opposite teeth during mastication are analysed. Using these features, we determine the direction of masticatory movements. Microwear patterns display diverse orientations among Dipodoidea: oblique in Sicistinae, Euchoreutinae and Zapodinae, propalinal in Dipodinae and intermediary in Allactaginae. Similarly, Muroidea exhibit the following orientations: oblique in Cricetinae and propalinal in Arvicolinae, Cricetomyinae, Gerbillinae and Murinae. These various chewing types illustrate different evolutionary grades within the superfamilies. Acquisition of the antero-posterior masticatory movement in Dipodoidea is related to flattening of the molar occlusal surface. However, in some muroid subfamilies, this direction of mastication is associated with low-crowned and cuspidate molars (Cricetomyinae, Murinae).  相似文献   
243.
Field investigations were conducted to measure subsoil trace element content and factors influencing content in an intensive periurban market garden in Chenggong County,Yunnan Province,South-West China.The area was divided into three different geomorphological units:specifically,mountain (M),transition (T) and lacustrine (L).Mean trace element content in subsoil were determined for Pb (58.2 mg/kg),Cd (0.89 mg/kg),Cu (129.2 mg/kg),and Zn (97.0 mg/kg).Strong significant relationships between trace element con...  相似文献   
244.
Environmental Modeling & Assessment - We designed a survey that aims at estimating individual willingness-to-pay to reduce noise and air pollution arising from transportation activity near the...  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