全文获取类型
收费全文 | 238篇 |
免费 | 37篇 |
专业分类
275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 15 毫秒
21.
Sequence-level analysis of the diploidization process in the triplicated FLOWERING LOCUS C region of Brassica rapa 下载免费PDF全文
Yang TJ Kim JS Kwon SJ Lim KB Choi BS Kim JA Jin M Park JY Lim MH Kim HI Lim YP Kang JJ Hong JH Kim CB Bhak J Bancroft I Park BS 《The Plant cell》2006,18(6):1339-1347
Strong evidence exists for polyploidy having occurred during the evolution of the tribe Brassiceae. We show evidence for the dynamic and ongoing diploidization process by comparative analysis of the sequences of four paralogous Brassica rapa BAC clones and the homologous 124-kb segment of Arabidopsis thaliana chromosome 5. We estimated the times since divergence of the paralogous and homologous lineages. The three paralogous subgenomes of B. rapa triplicated 13 to 17 million years ago (MYA), very soon after the Arabidopsis and Brassica divergence occurred at 17 to 18 MYA. In addition, a pair of BACs represents a more recent segmental duplication, which occurred approximately 0.8 MYA, and provides an exception to the general expectation of three paralogous segments within the B. rapa genome. The Brassica genome segments show extensive interspersed gene loss relative to the inferred structure of the ancestral genome, whereas the Arabidopsis genome segment appears little changed. Representatives of all 32 genes in the Arabidopsis genome segment are represented in Brassica, but the hexaploid complement of 96 has been reduced to 54 in the three subgenomes, with compression of the genomic region lengths they occupy to between 52 and 110 kb. The gene content of the recently duplicated B. rapa genome segments is identical, but intergenic sequences differ. 相似文献
22.
23.
Park JY Koo DH Hong CP Lee SJ Jeon JW Lee SH Yun PY Park BS Kim HR Bang JW Plaha P Bancroft I Lim YP 《Molecular genetics and genomics : MGG》2005,274(6):579-588
We constructed a bacterial artificial chromosome (BAC) library, designated as KBrH, from high molecular weight genomic DNA
of Brassica rapa ssp. pekinensis (Chinese cabbage). This library, which was constructed using HindIII-cleaved genomic DNA, consists of 56,592 clones with average insert size of 115 kbp. Using a partially duplicated DNA
sequence of Arabidopsis, represented by 19 and 9 predicted genes on chromosome 4 and 5, respectively, and BAC clones from the KBrH library, we studied
conservation and microsynteny corresponding to the Arabidopsis regions in B. rapa ssp. pekinensis. The BAC contigs assembled according to the Arabidopsis homoeologues revealed triplication and rearrangements in the Chinese cabbage. In general, collinearity of genes in the paralogous
segments was maintained, but gene contents were highly variable with interstitial losses. We also used representative BAC
clones, from the assembled contigs, as probes and hybridized them on mitotic (metaphase) and/or meiotic (leptotene/pachytene/metaphase
I) chromosomes of Chinese cabbage using bicolor fluorescence in situ hybridization. The hybridization pattern physically identified
the paralogous segments of the Arabidopsis homoeologues on B. rapa ssp. pekinensis chromosomes. The homoeologous segments corresponding to chromosome 4 of Arabidopsis were located on chromosomes 2, 8 and 7, whereas those of chromosome 5 were present on chromosomes 6, 1 and 4 of B. rapa ssp. pekinensis. 相似文献
24.
STYLIANOS MICHAIL SIMAIAKIS EVEN TJØRVE GABRIELE GENTILE ALESSANDRO MINELLI MOISIS MYLONAS 《Biological journal of the Linnean Society. Linnean Society of London》2012,105(1):146-159
The present study article examines the shapes of centipede species–area relationships (SARs) in the Mediterranean islands, compares the results of the linear form of the power model between archipelagos, discusses biological significance of the power model parameters with other taxa on the Aegean archipelago, and tests for a significant small‐island effect (SIE). We used 11 models to test the SARs and we compared the quality‐of‐fit of all candidate models. The power function ranked first and Z‐values was in the range 0.106–0.334. We assessed the presence of SIEs by fitting both a continuous and discontinuous breakpoint regression model. The continuous breakpoint regression functions never performed much better than the closest discontinuous model as a predictor of centipede species richness. We suggest that the relatively low Z‐values in our data partly reflect better dispersal abilities in centipedes than in other soil invertebrate taxa. Longer periods of isolation and more recent island formation may explain the somewhat lower constant c in the western Mediterranean islands compared to the Aegean islands. Higher breakpoint values in the western Mediterranean may also be a result of larger distance to the mainland and longer separation times. Despite the differences in the geological history and the idiosyncratic features of the main island groups considered, the overall results are quite similar and this could be assigned to the ability of centipedes to disperse across isolation barriers. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 146–159. 相似文献
25.
O'Neill CM Morgan C Kirby J Tschoep H Deng PX Brennan M Rosas U Fraser F Hall C Gill S Bancroft I 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2008,116(5):623-634
Quantitative approaches are now widely used to study the genetic architecture of complex traits. However, most studies have
been conducted in single mapping populations, which sample only a fraction of the natural allelic variation available within
a gene pool and can identify only a subset of the loci controlling the traits. To enable the progress towards an understanding
of the global genetic architecture of a broad range of complex traits, we have developed and characterised six new Arabidopsis thaliana recombinant inbred populations. To evaluate the utility of these populations for integrating analyses from multiple populations,
we identified quantitative trait loci (QTL) controlling flowering time in vernalized plants growing in 16 h days. We used
the physical positions of markers to align the linkage maps of our populations with those of six existing populations. We
identified seven QTL in genomic locations coinciding with those identified in previous studies and in addition a further eight
QTL were identified.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
An erratum to this article can be found at 相似文献
26.
TJ Beveridge 《Biotechnic & histochemistry》2001,76(3):111-118
The Gram stain differentiates bacteria into two fundamental varieties of cells. Bacteria that retain the initial crystal violet stain (purple) are said to be 'Gram-positive,' whereas those that are decolorized and stain red with carbol fuchsin (or safranin) are said to be 'Gram-negative.' This staining response is based on the chemical and structural makeup of the cell walls of both varieties of bacteria. Gram-positives have a thick, relatively impermeable wall that resists decolorization and is composed of peptidoglycan and secondary polymers. Gram-negatives have a thin peptidoglycan layer plus an overlying lipid-protein bilayer known as the outer membrane, which can be disrupted by decolorization. Some bacteria have walls of intermediate structure and, although they are officially classified as Gram-positives because of their linage, they stain in a variable manner. One prokaryote domain, the Archaea, have such variability of wall structure that the Gram stain is not a useful differentiating tool. 相似文献
27.
Nocturnal penile tumescence (NPT), as circumference change and rigidity, and REM sleep were measured in eight normal eugonadal men in two controlled experiments. In the first, exposure to erotic film prior to sleep had no effect on frequency of REM or on NPT. In the second placebo controlled experiment 150 mg im testosterone enanthate administration was associated with enhanced rigidity of NPT but with no effect on frequency or circumference change of NPT and no effect on frequency of REM. 相似文献
28.
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
29.
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
30.