全文获取类型
收费全文 | 86篇 |
免费 | 7篇 |
出版年
2021年 | 1篇 |
2019年 | 1篇 |
2015年 | 2篇 |
2013年 | 7篇 |
2012年 | 4篇 |
2011年 | 4篇 |
2010年 | 4篇 |
2009年 | 1篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 8篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1971年 | 1篇 |
1964年 | 1篇 |
1946年 | 2篇 |
1943年 | 1篇 |
排序方式: 共有93条查询结果,搜索用时 578 毫秒
41.
Freek T. Bakker Dorothea Hellbrügge Alastair Culham Mary Gibby 《Plant Systematics and Evolution》1998,211(3-4):273-287
Phylogenetic analysis of nrDNA ITS and trnL (UAA) 5 exon-trnF (GAA) chloroplast DNA sequences from 17 species ofPelargonium sect.Peristera, together with nine putative outgroups, suggests paraphyly for the section and a close relationship between the highly disjunct South African and Australian species of sect.Peristera. Representatives fromPelargonium sectt.Reniformia, Ligularia s. l. andIsopetalum (the St. Helena endemicP. cotyledonis) appear to be nested within thePeristera clade. The close relationship between the South African and AustralianPeristera is interpreted as being caused by long-range dispersal to Australia, probably as recent as the late Pliocene. 相似文献
42.
Fitness effects of amino acid replacements in the beta-galactosidase of Escherichia coli 总被引:7,自引:1,他引:6
Two genetic procedures were used to obtain amino acid replacements in the
lacZ-encoded beta-galactosidase in Escherichia coli. Amino acid
replacements could be obtained without regard to their effects on lactase
activity by selecting spontaneous mutations that relieved the strong
polarity of six nonsense mutations. When streaked on MacConkey- lactose
indicator plates, approximately 75% of these mutants gave strong red
lactose-fermenting colonies, and 25% gave white nonfermenting colonies.
Mutants from 11 other nonsense codons were isolated directly using
MacConkey-lactose indicator plates, on which positive color indication
requires only 0.5% of the wildtype lactase activity. Among the total of 17
codons, 25 variant beta-galactosidases were identified using
electrophoresis and thermal denaturation studies. The fitness effects of
these variant beta-galactosidases were determined using competition
experiments conducted with lactose as the sole nutrient limiting the growth
rate in chemostat cultures. Three of the replacements were deleterious, one
was selectively advantageous, and the selective effects of the remaining 21
were undetectable under conditions in which the smallest detectable
selection coefficient was approximately 0.4%/generation.
相似文献
43.
Fred J. Rumsey Johannes Chr. Vogel Stephen J. Russell John A. Barrett Mary Gibby 《Plant Ecology & Diversity》2013,6(1):37-47
Summary The Killarney Fern (Trichomanes speciosum) was considered amongst the rarest and most vulnerable of Europe's plants. Research which fed into the Biodiversity Action Plan and developed alongside it, has forced us to reconsider the level of threat to this species. A hitherto overlooked stage of the life-cycle, the gametophyte, has been shown to be comparatively abundant, genetically diverse, largely threat-free and with the potential over time to regenerate the familiar sporophyte stage. This research also promoted wider public interest which itself generated additional records, such that even the sporophyte is now known at more British sites than at any time previously and the species is accordingly considered ‘recovered’. However, continued legal protection and the need for further research are still recommended. 相似文献
44.
Blackmore S Gibby M Rae D 《Botanical journal of the Linnean Society. Linnean Society of London》2011,166(3):267-281
The need for action on the global environment is now well understood and governments, agencies, non-governmental organizations and botanic gardens have all been working in their various ways to promote environmental sustainability and reduce species and habitat loss for at least 10–20 years. The Global Strategy for Plant Conservation (GSPC) has been widely adopted, particularly by the botanic garden community, and has resulted in many successes despite failing to achieve its ultimate goal of halting the loss of plant biodiversity. The objectives and targets for Phase 2 of the GSPC, running from 2010 to 2020, mirror those of Phase 1 and had been largely agreed prior to their formal adoption at the Conference of the Parties to the Convention on Biological Diversity in Nagoya in October 2010. However, to be successful, the scientific contribution of botanic gardens needs to be strengthened, as does government policy and commitment. Botanic garden research to underpin conservation action, including the role of botanic garden horticulture, training and international capacity building, has a major part to play and needs to be better understood and better coordinated. We provide examples based on the experience of the Royal Botanic Garden Edinburgh in the UK and overseas. Government policy, at national and international levels, needs to reflect the fundamental importance of plant diversity in maintaining the biosphere and supporting humanity. The commitment of significant new resources is an essential prerequisite for success, but this needs to be well coordinated, inclusive of all stakeholders and carefully targeted. A further challenge is the need to integrate better the plant diversity-related activities of what are currently diverse and disconnected sectors, including agriculture, forestry, protected area management and botanic gardens. 相似文献
45.
46.
47.
TT Chowdhury S Arghandawi J Brand OO Akanji DL Bader DM Salter DA Lee 《Arthritis research & therapy》2008,10(2):R35
Background
Nitric oxide and prostaglandin E2 (PGE2play pivotal roles in both the pathogenesis of osteoarthritis and catabolic processes in articular cartilage. These mediators are influenced by both IL-1β and mechanical loading, and involve alterations in the inducible nitric oxide synthase (iNOS) and cyclo-oxygenase (COX)-2 enzymes. To identify the specific interactions that are activated by both types of stimuli, we examined the effects of dynamic compression on levels of expression of iNOS and COX-2 and involvement of the p38 mitogen-activated protein kinase (MAPK) pathway. 相似文献48.
Squirrell J Hollingsworth PM Woodhead M Russell J Lowe AJ Gibby M Powell W 《Molecular ecology》2003,12(6):1339-1348
The attributes of codominance, reproducibility and high resolution have all contributed towards the current popularity of nuclear microsatellites as genetic markers in molecular ecological studies. One of their major drawbacks, however, is the development phase required to obtain working primers for a given study species. To facilitate project planning, we have reviewed the literature to quantify the workload involved in isolating nuclear microsatellites from plants. We highlight the attrition of loci at each stage in the process, and the average effort required to obtain 10 working microsatellite primer pairs. 相似文献
49.
Rohrich RJ Sorokin ES Brown SA Gibby DL 《Plastic and reconstructive surgery》2003,112(1):259-63; discussion 264-5
A common misconception is that the umbilicus is a midline structure. To date, an anatomical survey examining whether the umbilicus is located at the midline has not been reported. This study measured the position of the umbilicus among 136 subjects, in two separate experiments. The results demonstrated that the umbilicus was not at the midline for nearly 100 percent of subjects and was more than 2 percent from the midline for more than 50 percent of subjects. This finding is of great importance for patient counseling in preoperative and postoperative settings. Because the discerning eye has repeatedly been demonstrated to be able to detect smaller asymmetries, these findings are significant and should be discussed with patients undergoing cosmetic abdominoplasty or reconstructive procedures, for preoperative informed consent. Education and preoperative demonstration can help prevent medicolegal ramifications. The umbilicus is rarely midline and, when critically analyzed, is located lateral to the midline axis more often than not. 相似文献
50.
High variation and strong phylogeographic pattern among cpDNA haplotypes in Taxus wallichiana (Taxaceae) in China and North Vietnam 总被引:1,自引:0,他引:1
Gao LM Möller M Zhang XM Hollingsworth ML Liu J Mill RR Gibby M Li DZ 《Molecular ecology》2007,16(22):4684-4698
We studied the phylogeography of Chinese yew (Taxus wallichiana), a tree species distributed over most of southern China and adjacent regions. A total of 1235 individuals from 50 populations from China and North Vietnam were analysed for chloroplast DNA variation using polymerase chain reaction-restriction fragment length polymorphism of the trnL-F intron-spacer region. A total of 19 different haplotypes were distinguished. We found a very high level of population differentiation and a strong phylogeographic pattern, suggesting low levels of recurrent gene flow among populations. Haplotype differentiation was most marked along the boundary between the Sino-Himalayan and Sino-Japanese Forest floristic subkingdoms, with only one haplotype being shared among these two subkingdoms. The Malesian and Sino-Himalayan Forest subkingdoms had five and 10 haplotypes, respectively, while the relatively large Sino-Japanese Forest subkingdom had only eight. The strong geography-haplotype correlation persisted at the regional floristic level, with most regions possessing a unique set of haplotypes, except for the central China region. Strong landscape effects were observed in the Hengduan and Dabashan mountains, where steep mountains and valleys might have been natural dispersal barriers. The molecular phylogenetic data, together with the geographic distribution of the haplotypes, suggest the existence of several localized refugia during the last glaciation from which the present-day distribution may be derived. The pattern of haplotype distribution across China and North Vietnam corresponded well with the current taxonomic delineation of the three intraspecific varieties of T. wallichiana. 相似文献