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   469016篇
  免费   167432篇
  国内免费   20850篇
  657298篇
  2018年   5812篇
  2017年   5572篇
  2016年   6952篇
  2015年   8587篇
  2014年   9675篇
  2013年   13171篇
  2012年   14768篇
  2011年   15327篇
  2010年   12545篇
  2009年   16707篇
  2008年   14807篇
  2007年   14868篇
  2006年   13380篇
  2005年   12788篇
  2004年   12642篇
  2003年   11933篇
  2002年   12421篇
  2001年   22717篇
  2000年   20816篇
  1999年   21331篇
  1998年   13125篇
  1997年   12939篇
  1996年   12274篇
  1995年   12091篇
  1994年   11643篇
  1993年   11259篇
  1992年   19175篇
  1991年   18577篇
  1990年   19132篇
  1989年   18477篇
  1988年   16770篇
  1987年   15615篇
  1986年   14451篇
  1985年   14059篇
  1984年   11255篇
  1983年   9588篇
  1982年   8211篇
  1981年   7363篇
  1980年   7172篇
  1979年   10341篇
  1978年   8330篇
  1977年   7706篇
  1976年   7351篇
  1975年   7439篇
  1974年   7977篇
  1973年   7888篇
  1972年   7542篇
  1971年   6794篇
  1970年   6067篇
  1969年   5822篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
7.
8.
Systematics and taxonomy of hares of the genus Lepus (Lagomorpha) are under contentious debate, and phylogenetic relationships among many taxa are not well understood. Here we study genetic differentiation and evolutionary relationships among North African hares, currently considered subspecies of Lepus capensis , cape hares ( L. capensis ) from the Cape province in South Africa, and brown hares ( L. europeaus ) from Europe and Anatolia, using maternally (mtDNA) and biparentally (allozymes) inherited markers. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of a c. 1.8 kb long segment of the mitochondrial control region using eight hexanucleotide-recognizing restriction endonucleases yielded 28 haplotypes, and horizontal starch gel electrophoresis of proteins encoded by 25 structural gene loci revealed 52 alleles at 18 polymorphic loci. Diverse phylogenetic analyses (neighbor joining dendrogram, median joining network, multidimensional scaling of pairwise distances, AMOVA, F -statistics, hierarchical F -statistics) of genetic variants revealed marked substructuring of mtDNA into three phylogeographic groups, namely an African, a central European, and an Anatolian, but a somewhat less pronounced overall differentiation of the nuclear genome, despite a relatively high number of population-specific (private) alleles. However, all our results are not incongruent with Petter's (1959: Mammalia 23 , 41; 1961: Z. f. Säugetierkunde 26 , 30; 1972 : Société Des Sciences Naturelles et Physiques du Maroc 52 , 122) hypothesis that North African hares generally belong to L. capensis and that brown hares should be included in this species as well.  相似文献   
9.
Ikenna Nzimiro was politically and intellectually active from 1948 through the next 50 years in the most momentous phase of the African emergence, and from the mid 1960s on to the last burst of intellectual output in his declining years, very much engaged. Nzimiro’s three-phase series of works will come to be seen as a contribution to the intellectual history of post-colonial Africa from a non-Marxist standpoint. Along with Coser’s ‘Men of Ideas’, African radical Leftists in that peasant environment, were more like the ‘French Ideologues’ of the pre-Napoleonic (post-Voltaire) era, than the ?scientific Marxist-Leninists’ many knew they had to be, to claim the then self-avowed path. Interestingly was Nzimiro’s attack on the ‘Eurocentric notion of class’ – in the process blurring the distinction between class and status. He was much more than a distinguished analyst, taking his calling as a radical public sociologist and Marxist advocate seriously. Yet, shielded by his historic role as an anti colonialist freedom fighter, the power elite considered him, in ironic contradiction, as one of their own. In the end, he was a genuine nationalist in search of a radical, even if less than textbook-revolutionary, revamping of the moribund postcolonial nation his peers ran, and to which he was on principle, very much opposed.  相似文献   
10.
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