全文获取类型
收费全文 | 305篇 |
免费 | 21篇 |
出版年
2013年 | 4篇 |
2012年 | 3篇 |
2011年 | 8篇 |
2010年 | 8篇 |
2009年 | 9篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 7篇 |
2005年 | 15篇 |
2004年 | 5篇 |
2003年 | 8篇 |
2002年 | 4篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 8篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1987年 | 3篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 8篇 |
1972年 | 4篇 |
1968年 | 3篇 |
1965年 | 3篇 |
1959年 | 3篇 |
1958年 | 6篇 |
1956年 | 7篇 |
1955年 | 5篇 |
1954年 | 11篇 |
1953年 | 8篇 |
1952年 | 8篇 |
1951年 | 10篇 |
1950年 | 5篇 |
1949年 | 12篇 |
1948年 | 8篇 |
排序方式: 共有326条查询结果,搜索用时 15 毫秒
1.
We describe seven polymorphic, dinucleotide microsatellite loci isolated from bank voles (Clethrionomys glareolus, Rodentia: Muridae) collected from the Wirral Peninsula, United Kingdom. Microsatellites were isolated as part of a long‐term study on the wider effects of host–pathogen interactions of an endemic viral disease. These microsatellites showed between five and 13 alleles per locus in these populations. Observed and expected heterozygosities varied between 0.275 to 0.777 and 0.487 to 0.794, respectively. These markers will allow us to investigate the structure of this bank vole population. 相似文献
2.
Novel strategies for assessing and managing the risks posed by invasive alien species to global crop production and biodiversity 总被引:3,自引:0,他引:3
RICHARD BAKER RAY CANNON PAUL BARTLETT IAN BARKER 《The Annals of applied biology》2005,146(2):177-191
International actions to combat the threat posed by invasive alien species (IAS) to crops and biodiversity have intensified in recent years. The formulation of 15 guiding principles on IAS by the Convention on Biological Diversity (CBD) stimulated the International Plant Protection Convention (IPPC) to review its role in protecting biodiversity. IPPC standards now demonstrate clearly that the risks posed by any organism that is directly or indirectly injurious to cultivated or uncultivated plants can be assessed and managed under the IPPC. Since the IPPC, unlike the CBD, constitutes an international legal instrument recognised by the World Trade Organization, greater protection from the introduction of IAS is now available. However, phytosanitary measures can only be enacted if they can be justified by risk analysis and we outline some novel strategies to improve the assessment and management of the risks posed by IAS, highlighting some of the key challenges which remain. 相似文献
3.
DUNN M. ALISON; HUGHES MONICA A.; PEARCE ROGER S.; JACK PETER L 《Journal of experimental botany》1990,41(11):1405-1413
A cDNA library was made from low positive temperature (6 ?C/2?C) grown barley shoot meristems. Several genes which are differentiallyexpressed, as measured by mRNA abundance, were selected fromthe library using a differential screen. This paper reportsan analysis of in vivo expression in several cultivars, theDNA sequence, copy number and chromosomal location of one gene(BLT14). In addition, genomic restriction fragment length polymorphismfor this gene in the 10 most widely UK-grown spring and 9 mostwidely UK-grown winter barley cultivars is analysed. Key words: Hordeum vulgare, low temperature, RFLP, differential expression, cDNA sequence 相似文献
4.
Specificity of the effect of sap-transmissible viruses in increasing the accumulation of luteoviruses in co-infected plants 总被引:1,自引:0,他引:1
H. BARKER 《The Annals of applied biology》1989,115(1):71-78
The concentration of potato leafroll luteovirus (PLRV) (c. 1300 ng/g leaf) in singly infected Nicotiana clevelandii plants was increased up to 10-fold in plants co-infected with each of several potyviruses, or with narcissus mosaic potexvirus, carrot mottle virus or each of three tobravirus isolates. With the tobraviruses, PLRV concentration was increased equally by co-infection with either NM-type isolates (coat protein-free cultures containing RNA-1) or M-type isolates (particle-producing cultures containing RNA-1 and RNA-2). In contrast, the accumulation of PLRV was not substantially affected by co-infection with either of two nepoviruses, cucumber mosaic cucumovirus, broad bean mottle bromovirus, alfalfa mosaic virus, pea enation mosaic virus or parsnip yellow fleck virus. The specificity of these interactions between PLRV and sap-transmissible viruses was retained in tests made in Nicotiana benthamiana and when beet western yellows luteovirus was used instead of PLRV. 相似文献
5.
The Production of Leaves and Stolon Branches on Established White Clover Cuttings in Relation to Temperature and Soil Moisture in the Field 总被引:1,自引:1,他引:0
Successive sets of cuttings of three white clover genotypeswere raised in a 15 °C growth room and transferred to thefield at 14 d intervals over the course of a year. Rates ofleaf appearance (leaves per stolon growing point per unit time)were found to be closely correlated with 10 cm soil temperatures.Petiole lengths, and weights of the lamina+petiole increasedin May and decreased towards the end of August, but also exhibiteda marked response to a mid-season water deficit. In the conditionsof the experiment (i.e. in the absence of competition from neighbouringplants) the vast majority of axillary buds developed into visiblebranches at all times of the year. There was, however, an increasein the nodal age at which bud development was first observedin winter. Deferred bud development was also observed, particularlyin one genotype, during periods characterized by dry soil surfaceconditions. The results are discussed in relation to observedpatterns of stolon branching in sward conditions. White clover, Trifolium repens, axillary bud development, branching, growing points, leaf appearance rate, petiole length, soil moisture, soil temperature 相似文献
6.
H. BARKER 《The Annals of applied biology》1986,109(2):445-447
Potato cultivars were tested for susceptibility to two British isolates of beet western yellows virus originally obtained from sugar beet and oil seed rape. Neither isolate was transmitted by Myzus persicae to virus-free potato plants, either by itself or in association with potato leafroll virus. 相似文献
7.
An Evaluation of EPR Measurements of the Organic Free Radical Content of Individual Seeds in the Non-destructive Testing of Seed Viability 总被引:2,自引:0,他引:2
HEPBURN HENRY A.; GOODMAN BERNARD A.; McPHAIL DONALD B.; MATTHEWS STAN; POWELL ALISON A. 《Journal of experimental botany》1986,37(11):1675-1684
Hepburn, H. A., Goodman, B. A., McPhail, D. B., Matthews, S.and Powell, A. A. 1986. An evaluation of EPR measurements ofthe organic free radical content of individual seeds in thenon-destructive testing of seed viability.J. exp. Bot.37: 16751684. Electron paramagnetic resonance (EPR) spectra of individualintact seeds of a range of legumes and brassicas have been obtainedin order to measure their organic free radical contents. Norelationship was found between free radical content and seedviability or early seedling growth for both legumes and brassicas.The testa had a much greater free radical concentration thaneither the embryo axes or the cotyledons for all cultivars ofseed tested. The general high free radical content of the testasuggests that there is little possibility of EPR being usedto predict the viability of individual seeds. The spectroscopicsplitting factor of g = 2·0045 reported for the intactseeds is consistent with the radicals' arising from melanictype compounds. Key words: Seed viability, free radical content 相似文献
8.
The Importance of Genetically Determined Seed Coat Characteristics to Seed Quality in Grain Legumes 总被引:2,自引:0,他引:2
Comparisons of five pairs of isogenk lines of peas, differingonly in the A gene for seed coat colour showed that white seeds(genotype aa) imbibed more rapidly than coloured seeds (AA),suffered greater imbibition damage revealed by dead tissue onthe cotyledons, and higher solute leakage. Seed-coat pigmentationwas closely associated with slow water uptake, since when expressionof the A gene was suppressed by the recessive pollens gene,the resulting white seeds {palpal AA) imbibed rapidly. The slowwater uptake by coloured seeds was not due to the restrictionof water entry by the seed coat since the differences in imbibitionrate were maintained when a portion of the seed coat was removedand seeds were imbibed with the exposed cotyledon in contactwith moist filter paper. Imbibition of similarly treated seedsby immersion in polyethylene glycol solutions (14%) whichincreased the seed/solution wettability, had little effect onthe water uptake of coloured seeds compared to imbibition inwater whereas that of white seeds increased in the first 10mins imbibition. Poor wettability of the inner surface of colouredseed coats did not therefore explain the slow imbibition ofthese seeds. The white seed coats loosened rapidly during imbibitionwhilst the coloured seed coats remained closely associated withthe cotyledons suggesting that the adherence of the seed coatto the cotyledons and therefore the ease of access of waterbetween the testa and cotyledons determines the rate of imbibition.The rapid water uptake by white-coated seeds and the subsequentimbibition damage may explain the high incidence of infectionof these seeds by the soil-bome fungus Pythhan after 2 d insoil. Improved seed quality and emergence may therefore be achievedby breeding for seed coat characteristics leading to reducedrates of imbibition Pisum sativum, isogenic lines, A gene, seed coat colour, imbibition, imbibition damage, wettability, pollens gene, seed quality, grain legumes 相似文献
9.
The Biology of the Tospoviruses 总被引:1,自引:0,他引:1
The tospoviruses are a diverse, cosmopolitan and economically important genus of plant viruses. In the recent past, interest in the tospoviruses has been rekindled with the resurgence and expansion of tomato spotted wilt virus and the appearance of new tospoviruses, including impatiens necrotic spot. This renewed interest in the tospoviruses, accompanied with the many recent advances in plant virology techniques, particularly those utilising molecular biology, have resulted in a rapid growth of our understanding of these viruses. This paper provides a review of the tospoviruses, encompassing all the major aspects of their biology, including the recent changes in the classification of the genus and current knowledge on molecular biology, vector relations, control and diagnosis. 相似文献
10.