全文获取类型
收费全文 | 303篇 |
免费 | 24篇 |
出版年
2020年 | 3篇 |
2016年 | 6篇 |
2015年 | 9篇 |
2014年 | 7篇 |
2013年 | 11篇 |
2012年 | 10篇 |
2011年 | 13篇 |
2010年 | 12篇 |
2009年 | 5篇 |
2008年 | 9篇 |
2007年 | 7篇 |
2006年 | 18篇 |
2005年 | 8篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 6篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 4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327条查询结果,搜索用时 62 毫秒
1.
Summary The main gibberellin in immature seed of Pisum sativum L., cv. Alaska, is identified as GA20 by GC-MS. GA9 may also be present. 相似文献
2.
Gibberellins (GAs) A17, A19, A20, A29, A44, 2OH-GA44 (tentative) and GA29-catabolite were identified in 21-day-old seeds of Pisum sativum cv. Alaska (tall). These GAs are qualitatively similar to those in the dwarf cultivar Progress No. 9 with the exception of GA19 which does not accumulate in Progress seeds. There was no evidence for the presence of 3-hydroxylated GAs in 21 day-old Alaska seeds. Dark-grown shoots of the cultivar Alaska contein GA1, GA8, GA20, GA29, GA8-catabolite and GA29-catabolite. Dark-grown shoots of the cultivar Progress No.9 contain GA8, GA20, GA29 and GA29-catabolite, and the presence of GA1 was strongly indicated. Quantitation using GAs labelled with stable isotope showed the level of GA1 in dark-grown shoots of the two cultivars to be almost identical, whilst the levels of GA20, GA29 and GA29-catabolite were significantly lower in Alaska than in Progress No. 9. The levels of these GAs in dark-grown shoots were 102- to 103-fold less than the levels in developing seeds. The 2-epimer of GA29 is present in dark-grown-shoot extracts of both cultivars and is not thought to be an artefact.Abbreviations cv
cultivar
- GAn
gibberellin An
- GC
gas chromatography
- GC-MS
combined gas chromatographymass spectrometry
- HPLC
high-pressure liquid chromatography
- KRI
Kovats retention index
- MeTMSi
methyl ester trimethylsilyl ether 相似文献
3.
A technique for covering areas of osteoradionecrosis in the medial aspect of the chest wall has been described. Utilizing a tissue expander, the skin was stretched sufficiently to obtain a suitable length whereby the medial defect could be covered and the donor site closed primarily. Such an operative approach should be considered when the patient presents with a medially located ulcer of small to moderate size and when nonirradiated skin is regionally available. Using this technique, long myocutaneous flaps that require extensive dissection, loss of functioning muscle, and resulting donor defects are avoided. 相似文献
4.
The gibberellin (GA) 2-hydroxylases in mature and immature seeds of Pisum sativum have been partially purified and characterised. The enzymes are unstable when stored below pH 7.0 or in the absence of a thiol reagent. The optimum assay pH is between 7.4 and 7.8 and activity is dependent upon the presence of -ketoglutarate, Fe2+ and ascorbate. The 2-hydroxylase activities for GA1, GA4, GA9 and GA20 are chromatographically inseparable and correspond to a protein of Mr 44000. The rate of GA 2-hydroxylation varies according to substrate and some evidence indicates that the 2-hydroxylase activities for GA1 and GA4 and for GA9 and GA20 may reside in different proteins. During pea seed maturation, the specific activity of the enzyme(s) increases dramatically and reaches a maximum at a time when endogenous GA9, GA20, GA29 and GA51 are also at their greatest concentration. This correlation is not the result of substrate induction of enzyme activity. Since the GA 2-hydroxylases operate at maximal rate at low substrate concentrations they are incapable of rapidly 2-hydroxylating excessive quantities of (exogenously applied) GA1 or GA20. On the basis of the kinetic parameters of the GA 2-hydroxylase activities, a generalised model is discussed for the control of the steady-state levels of bioactive hormone under normal physiological conditions.Abbreviations DTE
dithioerythritol
- EDTA
ethylenediaminetetraacetic acid
- GAn
gibberellin An
- HPLC
high-performance liquid chromatography
- HSS
high-speed supernatant
- LSS
low-speed supernatant
- PMSF
phenylmethane sulphonyl fluoride 相似文献
5.
Summary An extract from 6000 dark-grown Phaseolus coccineus seedlings was purified by countercurrent distribution and G-10 Sephadex followed by gradient elution from a silicic acid partition column with increasing amounts of ethyl actetate in n-hexane. 25 fractions were collected and tested with the barley-aleurone, Tan-ginbozu dwarf-rice, lettuce, cucumber, dwarf-pea, d-1, d-2, d-3 and d-5 maize, oat first-internode, and sugarcane-spindle bioassays. Major gibberellin (GA)-like activity was detected in fractions 4 (500g GA3-equivalents) and 12–13 (270 g GA3-equivalents) with smaller amounts in fractions 6, 8–9, 15–16, 18, 20, 23 and 25. The extracts were also applied to AMO-1618=dwarfed Ph.-coccineus seedlings. Fractions 4, 8 and 12 promoted the growth of both light- and dark-grown seedlings. GA1, GA3, GA4 and GA8 were active in the Phaseolus bioassay but GA8-glucoside was inactive.The biological and chromatographic properties of fractions 4, 8–9 and 12–13 correspond with those of GA4, GA19 and GA1. The identity of GA4 in fraction 4 was conclusively established by combined gas chromatography-mass spectrometry (GC-MS) of the methyl ester and the trimethylsilyl ether of the methyl ester. Gasliquid-chromatography peaks corresponding to these derivatives of GA19 and GA1 were detected on QF-1 and SE-33 columns but their intensities were too weak to permit conclusive identification by GC-MS.Supported by an S.R.C. StudentshipSupported by a NATO Grant.Supported by NRC Grant A-5727. 相似文献
6.
Abstract— A modified procedure is described for quantification of gangliosides in a mixture using thin-layer chromatography. Using this procedure, the gangliosides in human peripheral nerve were quantified, and compared with those in cerebral cortex and white matter. 相似文献
7.
Warfarin sodium was compared with bishydroxycoumarin (Dicumarol) in 16 patients on long-term anticoagulant therapy. When the patients were changed from bishydroxycoumarin to warfarin sodium there was no improvement in control of their prothrombin times. It was found that 5 mg. of warfarin had slightly less effect than 50 mg. of bishydroxycoumarin. It was concluded that the drugs were equally effective in long-term anticoagulant therapy. The metabolism of the ingested drug was more important than absorption in determining the control of the patients'' prothrombin times. 相似文献
8.
Characterization of four human YAC libraries for clone size, chimerism and X chromosome sequence representation. 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
R Nagaraja J Kere S MacMillan M J Masisi D Johnson B J Molini G R Halley K Wein M Trusgnich B Eble 《Nucleic acids research》1994,22(16):3406-3411
Four collections of human X-specific YACs, derived from human cells containing supernumerary X chromosomes or from somatic cell hybrids containing only X human DNA were characterized. In each collection, 80-85% of YAC strains contained a single X YAC. Five thousand YACs from the various libraries were sized, and cocloning was assessed in subsets by the fraction of YAC insert-ends with non-X sequences. Cocloning was substantial, ranging up to 50% for different collections; and in agreement with previous indications, in all libraries the larger the YACs, the higher the level of cocloning. In libraries made from human-hamster hybrid cells, expected numbers of clones were recovered by STS-based screening; but unexpectedly, the two collections from cells with 4 or 5 X chromosomes yielded numbers of YACs corresponding to an apparent content of only about two X equivalents. Thus it is possible that the DNA of inactive X chromosomes is poorly cloned into YACs, speculatively perhaps because of its specialized chromatin structure. 相似文献
9.
10.
DNA sequences were determined for three to five alleles of the bride-of-
sevenless (boss) gene in each of four species of Drosophila. The product of
boss is a transmembrane receptor for a ligand coded by the sevenless gene
that triggers differentiation of the R7 photoreceptor cell in the compound
eye. Population parameters affecting the rate and pattern of molecular
evolution of boss were estimated from the multinomial configurations of
nucleotide polymorphisms of synonymous codons. The time of divergence
between D. melanogaster and D. simulans was estimated as approximately 1
Myr, that between D. teissieri and D. yakuba as approximately 0.75 Myr, and
that between the two pairs of sibling species as approximately 2 Myr. (The
boss genes themselves have estimated divergence times approximately 50%
greater than the species divergence times.) The effective size of the
species was estimated as approximately 5 x 10(6), and the average mutation
rate was estimated as 1-2 x 10(-9)/nucleotide/generation. The ratio of
amino acid polymorphisms within species to fixed differences between
species suggests that approximately 25% of all possible single-step amino
acid replacements in the boss gene product may be selectively neutral or
nearly neutral. The data also imply that random genetic drift has been
responsible for virtually all of the observed differences in the portion of
the boss gene analyzed among the four species.
相似文献