全文获取类型
收费全文 | 738篇 |
免费 | 31篇 |
国内免费 | 40篇 |
专业分类
林业 | 8篇 |
农学 | 122篇 |
基础科学 | 61篇 |
132篇 | |
综合类 | 290篇 |
农作物 | 48篇 |
水产渔业 | 16篇 |
畜牧兽医 | 32篇 |
园艺 | 13篇 |
植物保护 | 87篇 |
出版年
2024年 | 3篇 |
2023年 | 12篇 |
2022年 | 37篇 |
2021年 | 27篇 |
2020年 | 28篇 |
2019年 | 31篇 |
2018年 | 24篇 |
2017年 | 35篇 |
2016年 | 31篇 |
2015年 | 21篇 |
2014年 | 37篇 |
2013年 | 55篇 |
2012年 | 54篇 |
2011年 | 45篇 |
2010年 | 73篇 |
2009年 | 37篇 |
2008年 | 21篇 |
2007年 | 27篇 |
2006年 | 26篇 |
2005年 | 20篇 |
2004年 | 17篇 |
2003年 | 24篇 |
2002年 | 21篇 |
2001年 | 17篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 2篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 13篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有809条查询结果,搜索用时 31 毫秒
51.
Accumulation of soluble phenolic compounds in sunflower capitula correlates with resistance to Sclerotinia sclerotiorum 总被引:2,自引:0,他引:2
Disease symptoms and total soluble phenolics content have been analysed in four sunflower (Helianthus annuus L.)lines with different resistance levels(from highly susceptible to resistant) to head rot caused by Sclerotinia sclerotiorum (Lib.) de Bary. At the beginning of the flowering stage, capitula were inoculated by spraying with a water suspension of
ascospores, and disease symptoms were evaluated from day 6 to day14 after inoculation. The most susceptible genotypes showed
all their ovaries to be necrosed and abundant lesions in corollas, bracts and receptacle. In the resistant line, the ovary
and corolla were only partially necrosed with no symptoms in the bracts or the receptacle. Total soluble phenolics were extracted
and quantified from different parts of the capitulum in both inoculated and non-inoculated plants. The amount of phenolic
compounds depended on the sunflower line, the time after inoculation, and the tissue. Higher constitutive and induced phenolic
content as well as phenylalanine ammonia-lyase activity were present in the most resistant line, these differences correlated
with the absence/presence of disease symptoms.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
52.
53.
Three diploid perennial sunflower species are useful for variety improvement: Helianthus mollis, because of sessile leaves, H. salicifolius, because of a high oil concentration, and H. maximiliani, a potential source of resistance to Sclerotinia sclerotiorum. The crossability of these species to cultivated sunflower was examined.Hybrids were obtained from eight combinations, with 3–15 F1 plants per combination. The F1's exhibited the dominant phenotype of the wild species. Pollen viability varied between 32.1 and 69.9%. Meiosis was irregular in the F1 hybrids. At diakinesis, bivalents (62.7–97.9% of meiocytes), univalents (0–31.23%), and multivalents (3.84–7.68%) were detected. At anaphase I, chromosome bridges were detected in 6.77 to 11.44% of meiocytes. Fast chromosomes in metaphase I, and lagging chromosomes in anaphase I and telophase II were evidenced in a high percentage of meiocytes. 相似文献
54.
Construction and characterization of a BAC library for sunflower (Helianthus annuus L.) 总被引:1,自引:0,他引:1
A bacterial artificial chromosome (BAC) library was constructed using the sunflower (Helianthus annuus L.) restorer line RHA325, which carries the restorer gene Rf1 and the Pl2-gene conferring resistance to downy mildew. High molecular weight DNA was prepared from nuclei using leaf material from two-week old seedlings. The library was constructed using the HindIII site of pBeloBAC11. The current BAC library comprises 104,736 clones. The insert size of the clones varied between 20 and 270 kb, with an average insert size of 60 kb. The whole 1.9× sunflower BAC library was spotted in duplicate on four high-density filters, each carrying 55,296 clones. The content of organellar DNA, which was estimated by colony hybridisation against the mitochondrial probe coxI and the chloroplast probe rbcL, proved to be less than 0.03 and 0.1%, respectively. BAC pools, allowing PCR-based screening, were made and used to identify positive BAC clones for the markers OP-K13_454, closely linked to the restorer gene Rf1. The PCR-based screening was verified by the results obtained for this marker by colony hybridisation. 相似文献
55.
A new sunflower mutant, CAS-12, was obtained, which has both high palmitic (≈30%) and high oleic acid contents, and also a
substantial amount of palmitoleic acid (≈7%). The mutant was selected after X-ray irradiation of dry seeds of the inbred line
BSD-2-423, which had normal palmitic (≈3%) and high oleic (≈88%) acid levels. The increase of palmitic and palmitoleic acids
occurred at the expense of the oleic acid content, which decreased to around 55% in respect to the original line. Linoleic
acid content is always under 5%. Palmitic and palmitoleic acid levels were similar to those of the high palmitic mutant CAS-5
obtained in a previous programme from a low oleic line isogenic to BSD-2-423 using a similar mutagenic treatment. In that
previous programme we also selected three high stearic acid mutants using chemical mutagenic treatment on the same sunflower
line (RDF-1-532). We attempted to obtain mutants in other lines but were unsuccessful. The isolation of similar mutants in
isogenic parental lines illustrates the importance of the genetic background in the development of specific mutants with an
altered seed oil fatty acid composition. The oil of this mutant will increase the range of potential uses of sunflower oil.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
56.
Ernest D. P. Whelan 《Euphytica》1980,29(1):33-46
Summary Interspecific substitutions of the nucleus of Helianthus annuus (2n=34) cv. Saturn into the cytoplasm of H. petiolaris (2n=34) by successive backcrossing, resulted in progenies with indehiscent anthers containing white, rather than normal yellow, pollen. Further backcrossing by cv. Saturn failed to restore pollen shed, suggesting that the male sterility was cytoplasmic. In vivo germination tests of pollen from 23 such plants from eight BC5 lines, indicated complete pollen sterility for 14 plants, but normal seed set, suggesting that female fertility was not affected. Meiosis in all plants examined was normal.Crosses between seven sources of pollen-fertility restorer, one collection of wild H. annuus, and an existing source of cytoplasmic male sterility, resulted in a high frequency of plants with normal pollen shed in all F1 progenies. However, no normal pollen shed was evident in F1 progenies for similar crosses between BC5 male-steriles and three of the seven restorer sources, nor for the single wild H. annuus evaluated. The foregoing suggests that the backcross substitution lines are a new source of cytoplasmic male sterility. The inheritance of restoration of pollen shed was complex and not fully elucidated. Some data suggested that two independent, complementary, dominant genes were required, but others indicated two to three independent, dominant genes. 相似文献
57.
58.
59.
Sclerotinia sclerotiorum infections on sunflower capitula produce white rot, one of the most dangerous diseases sunflower bears in all humid areas.
Therefore, disease quantification on developed genetic materials is a very important action in sunflower breeding. Given the
horizontal type of resistance these evaluations should be made in different environments. Several hybrids obtained after crossing
seven female × seven male sunflower inbred lines in a factorial mating design were evaluated for resistance to white rot in
two locations in the southeast of the province of Buenos Aires, Argentina. Disease incidence and the symptom appearance index
indicated significant genotypic effects and genotype × environment (G × E) interactions. Genotypic effects were a greater
source of variance than the G × E interaction effects. The G × E interactions only represented changes in magnitude. These
results were used to identify the best genotypes for both resistance factors. Four hybrids showed low disease incidence values
under both artificial and natural infections, of which only two had high values of the symptom appearance index at both locations.
These hybrids are considered to have adequate resistance attributes for the ascosporic penetration and the mycelium extension
in the capitulum tissue and could therefore be sown in the province of Buenos Aires without increasing risks of S. sclerotiorum attacks. 相似文献
60.