全文获取类型
收费全文 | 258篇 |
免费 | 19篇 |
专业分类
277篇 |
出版年
2020年 | 3篇 |
2016年 | 6篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 5篇 |
2012年 | 8篇 |
2011年 | 11篇 |
2010年 | 8篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 7篇 |
2006年 | 14篇 |
2005年 | 6篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 6篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 3篇 |
1996年 | 3篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 4篇 |
1974年 | 8篇 |
1973年 | 10篇 |
1972年 | 5篇 |
1971年 | 5篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1966年 | 3篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1960年 | 2篇 |
1956年 | 2篇 |
排序方式: 共有277条查询结果,搜索用时 15 毫秒
101.
102.
Paul Gaskin Michael Hutchison Norman Lewis Jake MacMillan Bernard O. Phinney 《Phytochemistry》1984,23(3):559-564
The metabolism of several ring C and D-functionalized ent-kaur-16-en-19-oic acids by cultures of Gibberella fujikuroi, mutant B1-41a, to the corresponding derivatives of the normal fungal gibberellins (GAs) and ent-kaurenoids is described. A range of 12α- and 12β-hydroxyGAs and ent-kaurenoids are characterized by their mass spectra and GC Kovats retention indices. The mass spectral and GC data are used to identify the 12α-hydroxy derivatives of GA12, GA14, GA37 and GA4 (GA58), and of the 12β-hydroxy derivatives of ent-7α-hydroxy- and ent-6α, 7α-dihydroxykaurenoic acids, in seeds of Cucurbita maxima. Similarly the metabolites of GA9, formed in seeds of Pisum sativum and cultures of G.fujikuroi, mutant B1-41a, are identified as 12α-hydroxyGA9. ent-11β-Hydroxy- and ent-11-oxo-kaurenoic acids are metabolized by the fungus to the corresponding 11-oxygenated derivatives of the normal fungal ent-kaurenoids and some C20-GAs; no 11-oxygenated C19-GAs are formed. Grandiflorenic acid, 11β-hydroxygrandiflorenic acid, attractyligen and ent-15β-hydroxykaurenoic acid are metabolized to unidentified products. 相似文献
103.
Peter Hedden Jan E. Graebe Michael H. Beale Paul Gaskin Jake MacMillan 《Phytochemistry》1984,23(3):569-574
A previously unknown pathway for the biosynthesis of 12α-hydroxylated gibberellins was found in a cell-free system from Cucurbita maxima endosperm. The microsome fraction converts the gibberellin precursor GA12-aldehyde simultaneously to GA12 and 12α-hydroxy-GA12-aldehyde. The ratio of these products is pH-dependent: above pH 6.5, the production of GA12 is favoured, whilst below pH 6.5, 12α-hydroxy-GA12-aldehyde is the predominant product. 12α-Hydroxy-GA12-aldehyde is converted further by soluble enzymes to 12α-hydroxy-GA14, 12α-hydroxy-GA15, 12α-hydroxy-GA37 and several unidentified products. This conversion is optimal between pH 6.0 and 6.5 in contrast to the previously known conversion of GA12-aldehyde to GA43 by soluble enzymes, which is optimal at pH 7.5. GA58, a major 12α-hydroxylated endogenous constituent of C. maxima endosperm, was not obtained when 12α-hydroxy-GA12-aldehyde was used as a substrate, but it was obtained together with GA4 when GA9 was incubated with a preparation containing both microsomal and soluble enzymes. 相似文献
104.
A systematic survey of conserved histidines in the core subunits of Photosystem I by site-directed mutagenesis reveals the likely axial ligands of P700. 总被引:2,自引:0,他引:2 下载免费PDF全文
K Redding F MacMillan W Leibl K Brettel J Hanley A W Rutherford J Breton J D Rochaix 《The EMBO journal》1998,17(1):50-60
The Photosystem I complex catalyses the transfer of an electron from lumenal plastocyanin to stromal ferredoxin, using the energy of an absorbed photon. The initial photochemical event is the transfer of an electron from the excited state of P700, a pair of chlorophylls, to a monomer chlorophyll serving as the primary electron acceptor. We have performed a systematic survey of conserved histidines in the last six transmembrane segments of the related polytopic membrane proteins PsaA and PsaB in the green alga Chlamydomonas reinhardtii. These histidines, which are present in analogous positions in both proteins, were changed to glutamine or leucine by site-directed mutagenesis. Double mutants in which both histidines had been changed to glutamine were screened for changes in the characteristics of P700 using electron paramagnetic resonance, Fourier transform infrared and visible spectroscopy. Only mutations in the histidines of helix 10 (PsaA-His676 and PsaB-His656) resulted in changes in spectroscopic properties of P700, leading us to conclude that these histidines are most likely the axial ligands to the P700 chlorophylls. 相似文献
105.
The Metabolism of Gibberellin A20 to Gibberellin A1 by Tall and Dwarf Mutants of Oryza sativa and Arabidopsis thaliana 总被引:4,自引:0,他引:4 下载免费PDF全文
The purpose of this study was to demonstrate the metabolism of gibberellin A20 (GA20) to gibberellin A1 (GA1) by tall and mutant shoots of rice (Oryza sativa L.) and Arabidopsis thaliana (L.) Heynh. The data show that the tall and dx mutant of rice and the tall and ga5 mutant of Arabidopsis metabolize GA20 to GA1. The data also show that the dy mutant of rice and the ga4 mutant of Arabidopsis block the metabolism of GA20 to GA1. [17-13C,3H]GA20 was fed to tall and the dwarf mutants, dx and dy, of rice and tall and the dwarf mutants, ga5 and ga4, of Arabidopsis. The metabolites were analyzed by high-performance liquid chromatography and full-scan gas chromatography-mass spectrometry together with Kovats retention index data. For rice, the metabolite [13C]GA, was identified from tall and dx seedlings; [13C]GA1 was not identified from the dy seedlings. [13C]GA29 was identified from tall, dx, and dy seedlings. For Arabidopsis, the metabolite [13C]GA1 was identified from tall, ga5, and ga4 plants. The amount of [13C]GA1 from ga4 plants was less than 15% of that obtained from tall and ga5 plants. [13C]GA29 was identified from tall, ga5, and ga4 plants. [13C]GA5 and [13C]GA3 were not identified from any of the six types of plant material. 相似文献
106.
Aerobic Heterotrophic Bacteria Indigenous to pH 2.8 Acid Mine Water: Microscopic Examination of Acid Streamers 总被引:5,自引:1,他引:4 下载免费PDF全文
"Acid streamers" found in acid coal mine drainage consist of bacteria trapped within an extracellular fibrillar polymer network. Inorganic compounds also precipitate within the polymer network. Several bacteria which appear to be different and are presumed to be different species are associated in the slimy mass of the "acid streamers." The "streamers" contain individual microcolonies or microcosms that can be recognized by a selective polysaccharide stain, which suggests that the slime streamer is a conglomeration of polymers produced by more than one species. 相似文献
107.
Natalie N. Kinloch Daniel R. MacMillan Anh Q. Le Laura A. Cotton David R. Bangsberg Susan Buchbinder Mary Carrington Jonathan Fuchs P. Richard Harrigan Beryl Koblin Margot Kushel Martin Markowitz Kenneth Mayer M. J. Milloy Martin T. Schechter Theresa Wagner Bruce D. Walker Jonathan M. Carlson Art F. Y. Poon Zabrina L. Brumme 《Journal of virology》2016,90(3):1244-1258
108.
The metabolism and growth-promoting activity of gibberellin A20 (GA20) were compared in the internode-length genotypes of pea, na le and na Le. Gibberellin A29 and GA29-catabolite were the major metabolites of GA20 in the genotype na le. However, low levels of GA1, GA8 and GA8-catabolite were also identified as metabolites in this genotype, confirming that the le allele is a leaky mutation. Gibberellin A20 was approximately 20 to 30 times as active in promoting internode growth of genotype na Le as of genotype na le. However, the levels of the 3-hydroxylated metabolite of GA20, GA8 (2-hydroxy GA1), were similar for a given growth response in both genotypes. In each case a close linear relationship was observed between internode growth and the logarithm of GA8 levels. A similar relationship was found on comparing GA20 metabolism in the three genotypes le
d, le and Le. The former mutation results in a more severe dwarf phenotype than the le allele (which has previously been shown to reduce the 3-hydroxylation of GA20 to GA1). These results indicate that GA20 has negligible intrinsic activity and support the contention that GA1 is the only GA active per se in promoting stem growth in pea.Abbreviations GAn
gibberellin An
- GC-MS
gas chromatography-mass spectrometry
- HPLC
high-pressure liquid chromatography 相似文献
109.
The induction of -amylase by exogenously supplied gibberellin A1 (GA1) and GA4 in embryoless caryopses of Hordeum vulgare (cv. Himalaya) was determined indirectly by measuring reducing sugars released from the endosperm. The presence of the inhibitors of GA biosynthesis, 2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidinecarboxylate methyl chloride (Amo 1618), Ancymidol, 2-chloroethyl trimethyl ammonium chloride (CCC) or (R,S)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,3-triazolyl)pentan-3-ol (PP333) did not inhibit -amylase production by either GA1 or GA4.Abbreviations Amo-1618
2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidinecarboxylate methyl chloride
- CCC
2-chloroethyl trimethyl ammonium chloride
- cv.
cultivar
- GA
gibberellin
- GC
gas chromatography
- GC-MS
combined gas chromatography-mass spectrometry
- PP333
(R,S)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,3-triazolyl) pentan-3-01 相似文献
110.
The large-scale purification of the anti-gibberellin monoclonal antibody, MAC 182, is described. N-Terminal amino acid sequences of the heavy and light chains were determined and compared with those of known antibodies. Fab-fragments were prepared and purified to a state suitable for crystallization. 相似文献