全文获取类型
收费全文 | 653篇 |
免费 | 76篇 |
出版年
2021年 | 9篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 11篇 |
2017年 | 4篇 |
2016年 | 8篇 |
2015年 | 22篇 |
2014年 | 19篇 |
2013年 | 27篇 |
2012年 | 29篇 |
2011年 | 37篇 |
2010年 | 35篇 |
2009年 | 27篇 |
2008年 | 34篇 |
2007年 | 34篇 |
2006年 | 29篇 |
2005年 | 32篇 |
2004年 | 26篇 |
2003年 | 24篇 |
2002年 | 28篇 |
2001年 | 19篇 |
2000年 | 12篇 |
1999年 | 7篇 |
1998年 | 8篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 15篇 |
1990年 | 11篇 |
1989年 | 6篇 |
1988年 | 17篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 9篇 |
1973年 | 4篇 |
1971年 | 10篇 |
1970年 | 4篇 |
1890年 | 3篇 |
排序方式: 共有729条查询结果,搜索用时 953 毫秒
61.
Members of the plant NIMA-related kinases are involved in organ development and vascularization in poplar, Arabidopsis and rice 总被引:1,自引:1,他引:0
Vigneault F Lachance D Cloutier M Pelletier G Levasseur C Séguin A 《The Plant journal : for cell and molecular biology》2007,51(4):575-588
NIMA-related kinases (Neks) are a family of serine/threonine kinases that have been linked to cell-cycle regulation in fungi and mammals. Information regarding the function of Neks in plants is very limited. We screened the three plant species that have had their genomes sequenced in an attempt to improve our understanding of their role in plants. We retrieved seven members in Arabidopsis thaliana, nine in Populus trichocarpa and six in Oryza sativa. Phylogenetic analysis showed that plant Neks are closely related to each other and contain paralogous genes. Moreover, their chromosome distribution and their exon-intron structure revealed that the actual plant Nek family was derived from a single representative followed by large segmental duplication events. Functional expression analyses in the three species relied on RTqPCR in poplar and publicly available microarray data for Arabidopsis and rice. Although plant Neks are present in every organ analyzed, their expression profiles suggest their involvement in plant development processes. Furthermore, we showed that PNek1, a member of the poplar family, is expressed at sites of free auxin synthesis and is specifically involved during the vascularization process. 相似文献
62.
63.
Murat Akkurt Leocir Welter Erika Maul Reinhard Töpfer Eva Zyprian 《Molecular breeding : new strategies in plant improvement》2007,19(2):103-111
Sequence-characterized amplified regions markers (SCARs) were developed from six randomly amplified polymorphic DNA (RAPD)
markers linked to the major QTL region for powdery mildew (Uncinula necator) resistance in a test population derived from the cross of grapevine cultivars “Regent” (resistant) × “Lemberger”(susceptible).
RAPD products were cloned and sequenced. Primer pairs with at least 21 nucleotides primer length were designed. All pairs
were tested in the F1 progeny of “Regent” × “Lemberger”. The SCAR primers resulted in the amplification of specific bands
of expected sizes and were tested in additional genetic resources of resistant and susceptible germplasm. All SCAR primer
pairs resulted in the amplification of specific fragments. Two of the SCAR markers named ScORA7-760 and ScORN3-R produced
amplification products predominantly in resistant individuals and were found to correlate to disease resistance. ScORA7-760,
in particular, is suitable for marker-assisted selection for powdery mildew resistance and to facilitate pyramiding powdery
mildew resistance genes from various sources. 相似文献
64.
Ryan F. Hechinger Alan C. Wood Armand M. Kuris 《Proceedings. Biological sciences / The Royal Society》2011,278(1706):656-665
In some of the most complex animal societies, individuals exhibit a cooperative division of labour to form castes. The most pronounced types of caste formation involve reproductive and non-reproductive forms that are morphologically distinct. In colonies comprising separate or mobile individuals, this type of caste formation has been recognized only among the arthropods, sea anemones and mole-rats. Here, we document physical and behavioural caste formation in a flatworm. Trematode flatworm parasites undergo repeated clonal reproduction of ‘parthenitae’ within their molluscan hosts forming colonies. We present experimental and observational data demonstrating specialization among trematode parthenitae to form distinct soldier and reproductive castes. Soldiers do not reproduce, have relatively large mouthparts, and are much smaller and thinner than reproductives. Soldiers are also more active, and are disproportionally common in areas of the host where invasions occur. Further, only soldiers readily and consistently attack heterospecifics and conspecifics from other colonies. The division of labour described here for trematodes is strongly analogous to that characterizing other social systems with a soldier caste. The parallel caste formation in these systems, despite varying reproductive mode and taxonomic affiliation, indicates the general importance of ecological factors in influencing the evolution of social behaviour. Further, the ‘recognition of self’ and the defence of the infected host body from invading parasites are comparable to aspects of immune defence. A division of labour is probably widespread among trematodes and trematode species encompass considerable taxonomic, life history and environmental diversity. Trematodes should therefore provide new, fruitful systems to investigate the ecology and evolution of sociality. 相似文献
65.
Ingrid Balcells Anna Castelló Anna Mercadé José L Noguera Amanda Fernández-Rodríguez Armand Sànchez Anna Tomàs 《BMC genetics》2011,12(1):1-6
Background
Canine atopic dermatitis (AD) is a common, heritable, chronic allergic skin condition prevalent in the West Highland White Terrier (WHWT). In canine AD, environmental allergens trigger an inflammatory response causing visible skin lesions and chronic pruritus that can lead to secondary bacterial and yeast infections. The disorder shares many of the clinical and histopathological characteristics of human AD and represents an animal model of this disorder that could be used to further elucidate genetic causes of human AD. Microsatellite markers genotyped in families of WHWTs affected with AD were used to perform a genome-wide linkage study in order to isolate chromosomal regions associated with the disorder.Results
Blood samples and health questionnaires were collected from 108 WHWTs spanning three families. A linkage simulation using these 108 dogs showed high power to detect a highly penetrant mutation. Ninety WHWTs were genotyped using markers from the Minimal Screening Set 2 (MSS-2). Two hundred and fifty six markers were informative and were used for linkage analysis. Using a LOD score of 2.7 as a significance threshold, no chromosomal regions were identified with significant linkage to AD. LOD scores greater than 1.0 were located in a 56 cM region of chromosome 7.Conclusions
The study was unable to detect any chromosomal regions significantly linked to canine AD. This could be a result of factors such as environmental modification of phenotype, incorrect assignment of phenotype, a mutation of low penetrance, or incomplete genome coverage. A genome-wide SNP association study in a larger cohort of WHWTs may prove more successful by providing higher density coverage and higher statistical power. 相似文献66.
Doreen Zegers Sigri Beckers Fenna de Freitas Armand V. Peeters Ilse L. Mertens Stijn L. Verhulst Raoul P. Rooman Jean‐Pierre Timmermans Kristine N. Desager Guy Massa Luc F. van Gaal Wim van Hul 《Obesity (Silver Spring, Md.)》2011,19(1):152-159
The melanocortin‐3 receptor (MC3R), a G‐protein‐coupled receptor expressed in the hypothalamus, is a key component of the leptin‐melanocortin pathway that regulates energy homeostasis. It is suggested that an MC3R defect leads to an increased feed efficiency, by which nutrients are partitioned preferentially into fat. In this study, we hypothesized that early‐onset obesity could be induced by mutations in MC3R. To investigate this hypothesis, we screened the entire coding region of the MC3R gene for mutations in obese subjects. A total of 404 overweight and obese children and adolescents, 86 severely obese adults (BMI ≥40 kg/m2), and 150 normal‐weight control adults were included. Besides three synonymous coding variations in the MC3R gene (S69S, L95L, I226I), we were able to identify three novel heterozygous, nonsynonymous, coding mutations (N128S, V211I, L299V) in three unrelated obese children. None of these mutations were found in any of the control subjects. Functional studies assessing localization and signaling properties of the mutant receptors provided proof for impaired function of the L299V mutated receptor, whereas no conclusive evidence for functional impairment of the N128S and V211I mutated receptors could be established. First, these results provide supporting evidence for a role of the MC3R gene in the pathogenesis of obesity in a small subset of patients. Second, they show that caution is called for the interpretation of newly discovered mutations in MC3R. 相似文献
67.
The relationship between microorganisms and birds has received increased attention recently. The state of knowledge of this
relationship, however, is based largely on examination of sick or dead birds, and knowledge of the prevalence and community
structure and function of microbes in healthy wild populations is limited. Using carbon substrate utilization profiles, microbial
communities were examined in 91 cloacal samples from 14 species within apparently healthy summer and winter passerine populations.
Within each season, gradient lengths and eigenvalues from ordination analyses suggested that many samples differed in their
carbon substrate utilization and several had very different communities. Cloacal microbe carbon utilization profiles were
distinguishable among host species, season-specific diet, and study site in the ordination analyses. However, these patterns
were only observed for the analysis of the summer data set. The results of this study support the idea that the avian host’s
microbial community, relative to carbon substrate utilization, is related to host diet. Previously, this pattern had only
been reported for potential pathogens isolated from the avian cloaca. Study site–specific patterns in the ordination analysis
suggest that environmental conditions at a particular study site may influence cloacal microbial communities in birds. Results
of this study indicate that examination of community-level physiological profiles may be a useful technique for distinguishing
among avian cloacal samples, similar to that already established for discriminating aqueous and soil samples. Future studies
that correlate microbe physiological profiles to condition-based indices of avian hosts may be most useful for eventually
using the profile as an indicator of environmental conditions experienced by hosts. 相似文献
68.
The plant kingdom is constantly challenged by a battery of evolving pathogens. New species or races of pathogens are discovered on crops that were initially bred for disease resistance, and globalization is facilitating the movement of exotic pests. Among these pests, obligate biotrophic parasites make up some of the most damaging groups and have been particularly challenging to study. Here we demonstrate the utility of kinetic PCR (kPCR) (real-time PCR, quantitative PCR) to assess the growth of poplar rust, caused by Melampsora species, by quantification of pathogen DNA. kPCR allowed the construction of reliable growth curves from inoculation through the final stages of uredinial maturation, as well as pathogen monitoring before symptoms become visible. Growth parameters, such as latency period, generation time in logarithmic growth, and the increase in DNA mass at saturation, were compared in compatible, incompatible, and nonhost interactions. Pathogen growth was monitored in different applications dealing with plant pathology, such as host and pathogen diversity and transgenic crop improvement. Finally, the capacity of kPCR to differentiate pathogens in the same sample has broad molecular ecology applications for dynamically monitoring the growth of fungi in their environments or in mixed populations or to measure the efficacy of pest control strategies. 相似文献
69.
70.
Susanne?Abelin?T?rnblom Holger?Maul Aurelija?KlimaviciuteEmail author Robert?E?Garfield Birgitta?Bystr?m Anders?Malmstr?m Gunvor?Ekman-Ordeberg 《Reproductive biology and endocrinology : RB&E》2005,3(1):33