全文获取类型
收费全文 | 238篇 |
免费 | 37篇 |
出版年
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 11篇 |
2013年 | 10篇 |
2012年 | 7篇 |
2011年 | 12篇 |
2010年 | 7篇 |
2009年 | 9篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1995年 | 4篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1981年 | 4篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1974年 | 6篇 |
1973年 | 2篇 |
1970年 | 6篇 |
1969年 | 3篇 |
1967年 | 2篇 |
1944年 | 2篇 |
1936年 | 3篇 |
1935年 | 7篇 |
1904年 | 1篇 |
排序方式: 共有275条查询结果,搜索用时 140 毫秒
41.
42.
We conducted an individual mark‐release‐recapture experiment on the beetle, Anoplophora glabripennis Motchulsky (Coleoptera: Cerambycidae). This invasive beetle has been introduced from Asia to Europe and North America and poses a serious threat to several important species of tree. Eradication efforts may benefit from knowledge of dispersal behaviour. Trees were cut and held to determine emergence rate of A. glabripennis. Unique marks were painted onto 912 beetles released into a group of 165 trees in Gansu, China. Data on subsequent sightings of beetles were used in a truncated diffusion model to calculate flight distances. Characteristics of the trees and climatic information were used in statistical tests for influence on movement. A total of 2245 sightings of beetles were observed and 29% of marked beetles were resighted. The scanning technique using binoculars was 90% effective in finding beetles and provided 81% accuracy for determining the sex of the beetles. Experimental manipulation of density quantified how A. glabripennis congregated on unoccupied trees and were repulsed from crowded hosts. The seasonal emergence rate of adults declined exponentially from July 20 to August 5. The results suggested A. glabripennis fly to nearby host trees at a rate of 34% per day. Median flight distance was estimated at 20 m per day. Statistical analysis with a generalized linear model tested the beetle's propensity to leave a tree and distance of flight. Generally, beetle movement showed a significant response to beetle density, weather conditions, beetle size, and tree size, in that order. The techniques developed here improve on previous recapture techniques to quantify dispersal and can be useful for analysing populations of other organisms. 相似文献
43.
Detection of additional antigenic determinants of hepatitis B antigen 总被引:30,自引:0,他引:30
W H Bancroft F K Mundon P K Russell 《Journal of immunology (Baltimore, Md. : 1950)》1972,109(4):842-848
44.
45.
John M. Romansic Amy A. Waggener Betsy A. Bancroft Andrew R. Blaustein 《Hydrobiologia》2009,624(1):219-233
Ambient levels of ultraviolet-B radiation (UVB) have a variety of detrimental effects on aquatic organisms. These include
death and effects on growth, development, physiology, and behavior. Amphibians show all of these effects. However, the effects
vary with species, life history stage, and ecological context. Little is known about the implications of the detrimental effects
of UVB on ecological dynamics. Our study was designed to test how UVB may affect predator–prey interactions, an important
ecological dynamic. Specifically, we tested the effect of UVB on the susceptibility of Cascades frog (Rana cascadae) larvae to predation by rough-skinned newts (Taricha granulosa). We also further examined the sublethal effects of UVB on growth and development in Cascades frog larvae. We found no direct
effect of UVB exposure on survival. However, UVB-exposed frog larvae displayed decreased growth and increased prevalence of
deformities. UVB also caused increased susceptibility to predation, but there was a significant treatment–block interaction.
UVB increased susceptibility to predation in two out of five blocks of Cascades frogs. The other three blocks did not show
an effect of UVB on susceptibility to predation. Our study suggests that UVB can alter susceptibility to predation in at least
one amphibian species. UVB-induced alteration of predator–prey interactions could potentially lead to changes at the population,
community, and ecosystem levels.
Handling editor: K. Martens 相似文献
46.
47.
Paul Carroll Lise J. Schreuder Julian Muwanguzi-Karugaba Siouxsie Wiles Brian D. Robertson Jorge Ripoll Theresa H. Ward Gregory J. Bancroft Ulrich E. Schaible Tanya Parish 《PloS one》2010,5(3)
Fluorescent reporter proteins have proven useful for imaging techniques in many organisms. We constructed optimized expression systems for several fluorescent proteins from the far-red region of the spectrum and analyzed their utility in several mycobacterial species. Plasmids expressing variants of the Discosoma Red fluorescent protein (DsRed) from the Mycobacterium bovis hsp60 promoter were unstable; in contrast expression from the Mycobacterium smegmatis rpsA promoter was stable. In Mycobacterium tuberculosis expression of several of the far-red reporters was readily visualised by eye and three reporters (mCherry, tdTomato, and Turbo-635) fluoresced at a high intensity. Strains expressing mCherry showed no fitness defects in vitro or in macrophages. Treatment of cells with antibiotics demonstrated that mCherry could also be used as a reporter for cell death, since fluorescence decreased in the presence of a bactericidal compound, but remained stable in the presence of a bacteriostatic compound. mCherry was functional under hypoxic conditions; using mCherry we demonstrated that the PmtbB is expressed early in hypoxia and progressively down-regulated. mCherry and other far-red fluorescent proteins will have multiple uses in investigating the biology of mycobacteria, particularly under non-replicating, or low cell density conditions, as well as providing a novel means of detecting cell death rapidly. 相似文献
48.
Genome-wide investigation of genetic changes during modern breeding of Brassica napus 总被引:1,自引:0,他引:1
Nian Wang Feng Li Biyun Chen Kun Xu Guixin Yan Jiangwei Qiao Jun Li Guizhen Gao Ian Bancroft Jingling Meng Graham J. King Xiaoming Wu 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2014,127(8):1817-1829
Key message
Considerable genome variation had been incorporated within rapeseed breeding programs over past decades.Abstract
In past decades, there have been substantial changes in phenotypic properties of rapeseed as a result of extensive breeding effort. Uncovering the underlying patterns of allelic variation in the context of genome organisation would provide knowledge to guide future genetic improvement. We assessed genome-wide genetic changes, including population structure, genetic relatedness, the extent of linkage disequilibrium, nucleotide diversity and genetic differentiation based on F ST outlier detection, for a panel of 472 Brassica napus inbred accessions using a 60 k Brassica Infinium® SNP array. We found genetic diversity varied in different sub-groups. Moreover, the genetic diversity increased from 1950 to 1980 and then remained at a similar level in China and Europe. We also found ~6–10 % genomic regions revealed high F ST values. Some QTLs previously associated with important agronomic traits overlapped with these regions. Overall, the B. napus C genome was found to have more high F ST signals than the A genome, and we concluded that the C genome may contribute more valuable alleles to generate elite traits. The results of this study indicate that considerable genome variation had been incorporated within rapeseed breeding programs over past decades. These results also contribute to understanding the impact of rapeseed improvement on available genome variation and the potential for dissecting complex agronomic traits. 相似文献49.
50.
Feng Li Biyun Chen Kun Xu Jinfeng Wu Weilin Song Ian Bancroft Andrea L. Harper Martin Trick Shengyi Liu Guizhen Gao Nian Wang Guixin Yan Jiangwei Qiao Jun Li Hao Li Xin Xiao Tianyao Zhang Xiaoming Wu 《DNA research》2014,21(4):355-367
Association mapping can quickly and efficiently dissect complex agronomic traits. Rapeseed is one of the most economically important polyploid oil crops, although its genome sequence is not yet published. In this study, a recently developed 60K Brassica Infinium® SNP array was used to analyse an association panel with 472 accessions. The single-nucleotide polymorphisms (SNPs) of the array were in silico mapped using ‘pseudomolecules’ representative of the genome of rapeseed to establish their hypothetical order and to perform association mapping of seed weight and seed quality. As a result, two significant associations on A8 and C3 of Brassica napus were detected for erucic acid content, and the peak SNPs were found to be only 233 and 128 kb away from the key genes BnaA.FAE1 and BnaC.FAE1. BnaA.FAE1 was also identified to be significantly associated with the oil content. Orthologues of Arabidopsis thaliana HAG1 were identified close to four clusters of SNPs associated with glucosinolate content on A9, C2, C7 and C9. For seed weight, we detected two association signals on A7 and A9, which were consistent with previous studies of quantitative trait loci mapping. The results indicate that our association mapping approach is suitable for fine mapping of the complex traits in rapeseed. 相似文献