全文获取类型
收费全文 | 363篇 |
免费 | 41篇 |
国内免费 | 1篇 |
专业分类
405篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 25篇 |
2014年 | 26篇 |
2013年 | 25篇 |
2012年 | 37篇 |
2011年 | 31篇 |
2010年 | 17篇 |
2009年 | 13篇 |
2008年 | 15篇 |
2007年 | 26篇 |
2006年 | 14篇 |
2005年 | 20篇 |
2004年 | 10篇 |
2003年 | 22篇 |
2002年 | 18篇 |
2001年 | 10篇 |
2000年 | 11篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1980年 | 1篇 |
1969年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有405条查询结果,搜索用时 0 毫秒
401.
Gabriele Cerutti Yicheng Guo Tongqing Zhou Jason Gorman Myungjin Lee Micah Rapp Eswar R. Reddem Jian Yu Fabiana Bahna Jude Bimela Yaoxing Huang Phinikoula S. Katsamba Lihong Liu Manoj S. Nair Reda Rawi Adam S. Olia Pengfei Wang Baoshan Zhang Lawrence Shapiro 《Cell host & microbe》2021,29(5):819-833.e7
402.
403.
Dobson Michael Mathooko Jude M. Ndegwa Fidensio K. M’Erimba Charles 《Hydrobiologia》2004,519(1-3):207-210
Mass loss of leaf litter from five common riparian trees in Kenya was determined using mesh bags over a 70-day period. The study was carried out in a river which previous research has shown to be apparently devoid of invertebrate shredders. There was a five fold difference between the most rapid and slowest decay rates, but all were within the fast range identified from temperate zone trees, demonstrating high rates of microbial activity. We conclude, therefore, that the low biomass of invertebrate shredders in Kenyan highland streams cannot be explained by poor quality of the leaf litter that enters them. 相似文献
404.
Field experiments to examine the effect of continuous physical disturbance on the Ephemeroptera of the Naro Moru River, Kenya,
wereundertaken from June 1993 to January 1994. Continuous disturbance wasadministered on a randomly selected subsite of the
sediment surface.Artificial physical disturbance within the experimental subsite involvedcontinuous local displacement, shifting
and stirring of the streambedsurface substrates (about 10 cm depth) by hand every one minute for 10 or 14min. Three control
samples were also taken randomly from the sedimentsurface of an undisturbed stratified area of the study riffle at the startof
each disturbance occasion. All samples were collected using a Hesssampler (surface sampling area of 3.142 dm2; meshsize 80μm). Seven mayfly species were particularly abundant and these included Afronurus sp., Afroptilum sudafricanum
LESTAGE, Baetis s.l., Baetis(Nigrobaetis) sp. 1, Baetis (Nigrobaetis) sp. 2, Caenis sp. and Choroterpes(Euthraulus) sp. About
83,8% of the total mayfly density and88.1% of the biomass were removed from the streambed surface withinthe first three minutes
of continuous physical disturbance. A mayfly biomassof 33.7391 mg dm2 and total density of 1357.6 inddm2 were collected from the disturbed subsite during the studyduration. Further, a biomass of about 42.8335 mg dm−2and total density of 2366 ind dm−2 were collected fromthe control sites. There was a near-complete depletion of mayflyindividuals from the topmost sediment
layer within 14 min of continuousdisturbance.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
405.
David M Hunt Jude Fitzgibbon Sergey J Slobodyanyuk James K Bowmaker Kanwaljit S Dulai 《Molecular phylogenetics and evolution》1997,8(3):415-422
Lake Baikal in Eastern Siberia contains a remarkable flock of 29 species of teleost fishes of the suborder Cottoidei (sculpins, bullheads) that are endemic to the lake and its associated rivers and occupy all depth habitats down to over 1500 m. The species are divided into three families, the Cottidae with 7 species, the Abyssocottidae with 20 species, and the Comephoridae with 2 species. Nucleotide sequences of the rod opsin gene from 12 of these species, plus a non-Baikal marine species, have been used to examine the evolutionary relations and the divergence time of the flock. Phylogenetic trees, generated by neighbor-joining and maximum parsimony, indicate that the unique Comephoridae family with its viviparity and unusual appearance is closely related to the Cottidae and Abyssocottidae, whereas the genusCottocomephorus,at present placed in the Cottidae, was the first to diverge from the ancestral species and forms a separate lineage. The major adaptation to deep water would appear to be of relatively recent origin, and there is evidence that the ancestral species occupied a shallow-water marine or brackish habitat. Estimates of antiquity obtained from synonymous substitutions place the origin of the species flock at around 4.9 million years ago. 相似文献