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   1374766篇
  免费   123192篇
  国内免费   1416篇
  2021年   17941篇
  2019年   16193篇
  2018年   18074篇
  2017年   16855篇
  2016年   28276篇
  2015年   42411篇
  2014年   50420篇
  2013年   76567篇
  2012年   37775篇
  2011年   26801篇
  2010年   44087篇
  2009年   45319篇
  2008年   25557篇
  2007年   23588篇
  2006年   28503篇
  2005年   29539篇
  2004年   28760篇
  2003年   26063篇
  2002年   24212篇
  2001年   33449篇
  2000年   30877篇
  1999年   31058篇
  1998年   25414篇
  1997年   25316篇
  1996年   24771篇
  1995年   22932篇
  1994年   22723篇
  1993年   21819篇
  1992年   27269篇
  1991年   25812篇
  1990年   24554篇
  1989年   25257篇
  1988年   23481篇
  1987年   22374篇
  1986年   21211篇
  1985年   23088篇
  1984年   22854篇
  1983年   20234篇
  1982年   20601篇
  1981年   19832篇
  1980年   18589篇
  1979年   19045篇
  1978年   17902篇
  1977年   17200篇
  1976年   16471篇
  1975年   16012篇
  1974年   16670篇
  1973年   16991篇
  1972年   14583篇
  1971年   13364篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
221.
In 1990 and 1994, two males of Golden Eagles were found with small lead particles in their stomachs. Both individuals died soon after they had been taken sitting on the soil in bad condition. There are some findings of dead eagles in the same area which showed no sign of having been injured. The two cases of presumed lead poisoning coincide with intense efforts to reduce the number of ChamoixRupicapra rupicapra by hunting. The bullets used contain a nucleus of lead and eagles were seen taking the entrails of the shot chamoix.  相似文献   
222.
223.
224.
Agapophytinae subf.n. is a highly diverse lineage of Australasian Therevidae, comprising eight described and two new genera: Agapophytus Guérin‐Méneville, Acupalpa Kröber, Acraspisa Kröber, Belonalys Kröber, Bonjeania Irwin & Lyneborg, Parapsilocephala Kröber, Acatopygia Kröber, Laxotela Winterton & Irwin, Pipinnipons gen.n. and Patanothrix gen.n. A genus‐level cladistic analysis of the subfamily was undertaken using sixty‐eight adult morphological characters and c. 1000 base pairs of the elongation factor‐1α (EF‐1α) protein coding gene. The morphological data partition produced three most parsimonious cladograms, whereas the molecular data partition gave a single most parsimonious cladogram, which did not match any of the cladograms found in the morphological analysis. The level of congruence between the data partitions was determined using the partition homogeneity test (HTF) and Wilcoxon signed ranks test. Despite being significantly incongruent in at least one of the incongruence tests, the partitions were combined in a simultaneous analysis. The combined data yielded a single cladogram that was better supported than that of the individual partitions analysed separately. The relative contributions of the data partitions to support for individual nodes on the combined cladogram were investigated using Partitioned Bremer Support. The level of support for many nodes on the combined cladogram was non‐additive and often greater than the sum of support for the respective nodes on individual partitions. This synergistic interaction between incongruent data partitions indicates a common phylogenetic signal in both partitions. It also suggests that criteria for partition combination based solely on incongruence may be misleading. The phylogenetic relationships of the genera are discussed using the combined data. A key to genera of Agapophytinae is presented, with genera diagnosed and figured. Two new genera are described: Patanothrix with a new species (Pat. skevingtoni) and Pat. wilsoni (Mann) transferred from Parapsilocephala, and Pipinnipons with a new species (Pip. kroeberi). Pipinnipons fascipennis (Kröber) is transferred from Squamopygia Kröber and Pip. imitans (Mann) is transferred from Agapophytus. Agapophytus bicolor (Kröber) is transferred from Parapsilocephala. Agapophytus varipennis Mann is synonymised with Aga. queenslandi Kröber and Aga. flavicornis Mann is synonymised with Aga. pallidicornis (Kröber).  相似文献   
225.
226.
227.
228.
229.
230.
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