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1.
The pineapple plant (Ananas comosus) was shown to contain at least four distinct cysteine proteinases, which were purified by a procedure involving active-site-directed affinity chromatography. The major proteinase present in extracts of plant stem was stem bromelain, whilst fruit bromelain was the major proteinase in the fruit. Two additional cysteine proteinases were detected only in the stem: these were ananain and a previously undescribed enzyme that we have called comosain. Stem bromelain, fruit bromelain and ananain were shown to be immunologically distinct. Enzymic characterization revealed differences in both substrate-specificities and inhibition profiles. A study of the cysteine proteinase derived from the related bromeliad Bromelia pinguin (pinguinain) indicated that in many respects it was similar to fruit bromelain, although it was found to be immunologically distinct. 相似文献
2.
Ananain: a novel cysteine proteinase found in pineapple stem 总被引:3,自引:0,他引:3
A previously unknown cysteine proteinase, named ananain, has been isolated from crude commercial pineapple stem bromelain. The purification procedure involved affinity chromatography on Sepharose-Gly-Phe-glycinaldehyde semicarbazone, and cation-exchange chromatography. The relative molecular mass of ananain was very similar to that of bromelain (25,000 and 26,000, respectively), but ananain differed greatly in specificity for hydrolysis of peptide and protein substrates. The new enzyme behaved as a typical cysteine proteinase in showing strong inhibition by chicken cystatin, whereas bromelain was scarcely affected. Ananain was also shown to be immunologically distinct from bromelain. The significance of the discovery of ananain for the interpretation of previous work on "bromelain" is pointed out. 相似文献
3.
Activity of aminoacyl-transfer-ribonucleic acid synthetases in tobacco-leaf tissue in relation to senescence and to the action of 6-furfurylaminopurine 总被引:15,自引:7,他引:8 下载免费PDF全文
1. Streptomyces griseus was grown in a medium containing l-[Me-(14)C]methionine, and the labelled products from an ethanolic extract of the cells were examined. 2. Acid hydrolysis of one of the products gave a compound identified as 3-O-[Me-(14)C]-methylmannose by a series of degradative reactions. 3. Reduction of the radioactive compound gave 3-O-methyl-d-mannitol, indistinguishable from a synthetic sample. 相似文献
4.
Rowan Jenkins 《The Botanical review》1993,59(2):81-111
A review of methods used in the taxonomy of the Fagaceae is presented, with a critical focus made on the nomenclature of extant and fossil taxa, notablyNothofagus. The most recent classifications of the family and the problems of character weighting are considered, and an argument is made to reduce the subfamilies to tribes. The origin of the cupule is then discussed. Interpretations of the cupule as a series of reduced dichasial axes are criticized for their essentialistic approach, lack of evolutionary evidence and failure of application to the family as a whole. With the postulating of an ancestral form, the origin of the cupule involving a combination of characters from an outer tripartite perianth whorl and the pericarp is proposed. The theory provides for the evolution of the thin-walled dry pericarp and all the cupule forms found in the family today. 相似文献
5.
Steven A. Akman Fumiyo Kusu Kiyoko Takamura Rowan Chlebowski Jerome Block 《Analytical biochemistry》1984,141(2):488-493
A differential pulse polarographic assay for plasma vitamin K3 (menadione) has been developed. Details of the assay are (i) lipid-soluble material is extracted from plasma into ether by the method of Bjornsson et al. [(1978) Thromb. Haemostas.2, 466–473]; (ii) ether is evaporated under nitrogen and the residue is dissolved in the supporting electrolyte, methanol: 0.2 m borate buffer (9:1), pH 6.8; (iii) current height is measured at ?0.32 V vs SCE on the differential pulse polarogram. The lower sensitivity limit of this technique after addition of standard vitamin K3 to plasma is 0.3 μm; the calibration curve is linear from 0.6 through 10 μm. Two patients treated with a single dose of menadiol sodium diphosphate, 20 mg/M2 i.m., achieved measurable plasma vitamin K3 levels at 0.5 to 1.0 h ranging between 0.5 (0.08 μg/ml) and 2 μm (0.3 μg/ml). 相似文献
6.
Plant growth inhibitors of the podolactone-type have been detected by bioassay in ten further species of Podocarpus. The most active extracts in P. elatus were from root tips, root cortex and very young leaves. Fifty-seven other conifers were examined for this type of activity. It is present in Cephalotaxus harringtonia where it is probably due to the presence of harringtonolide, which, like momilactone B from rice husks, shows podolactone-type inhibition of the growth of etiolated dwarf pea hooks. 相似文献
7.
The low-field portions of the 250-MHz 1H nuclear magnetic resonance (NMR) specra of native and chemically modified bovine basic pancreatic trypsin inhibitor (BPTI) have been studied as a function of pH over the range pH 5-13. Resonances associated with the 16 protons of the aromatic rings of the four BPTI tyrosines have been located and assigned to specific tyrosyl residues. Titrations of pH yielded pK's for tyrosines-10, -21, -23, and -35 of 10.4, 11.0, 11.7, and 11.1, respectively. The resonances associated with the nitrotyrosine-10 protons of mononitrated BPTI and the nitrotyrosine-10 and -21 protons of dinitrated BPTI have been similarly located, assigned and titrated yielding pK's for nitrotyrosine-10 and -21 of 6.6 and 6.4, respectively. The high-field NMR spectrum indicates that the aromatic ring of tyrosine-35 rotates less than 160 times per second at 25 degrees for pH's in the range 5-9. 相似文献
8.
Wanzhen Liu David A. S. Smith Gayatri Raina Rowan Stanforth Ivy Ng'Iru Piera Ireri Dino J. Martins Ian J. Gordon Simon H. Martin 《Biology letters》2022,18(6)
Warning coloration provides a textbook example of natural selection, but the frequent observation of polymorphism in aposematic species presents an evolutionary puzzle. We investigated biogeography and polymorphism of warning patterns in the widespread butterfly Danaus chrysippus using records from citizen science (n = 5467), museums (n = 8864) and fieldwork (n = 2586). We find that polymorphism in three traits controlled by known mendelian loci is extensive. Broad allele frequency clines, hundreds of kilometres wide, suggest a balance between long-range dispersal and predation of unfamiliar morphs. Mismatched clines for the white hindwing and forewing tip in East Africa are consistent with a previous finding that the black wingtip allele has spread recently in the region through hitchhiking with a heritable endosymbiont. Light/dark background coloration shows more extensive polymorphism. The darker genotype is more common in cooler regions, possibly reflecting a trade-off between thermoregulation and predator warning. Overall, our findings show how studying local adaptation at the global scale provides a more complete picture of the evolutionary forces involved. 相似文献
9.
Rates of DNA change and phylogeny from the DNA sequences of the alcohol dehydrogenase gene for five closely related species of Hawaiian Drosophila 总被引:11,自引:1,他引:11
The sequence of 1.6 kb of DNA surrounding the alcohol dehydrogenase (Adh) gene from five species of the Planitibia subgroup of the Hawaiian picture-winged Drosophila, with estimated divergence times of 0.4-5.1 Myr, has been determined. The gene trees which were found by using the sequence divergence from different regions of the sequences are generally in accord with the phylogeny proposed for these species when chromosomal inversions and island of origin are used. One of the species (D. picticornis) appears to be more distant from the other species in this group than they are from a member of the Grimshawi group (D. affinidisjuncta) which is chromosomally more distant. Two of the species (D. differens and D. plantibia) show heterogeneity in the nucleotide changes in the Adh coding region, heterogeneity which is interpreted to be due to a gene conversion or recombination after hybridization between the two species. The minimal rate of nucleotide substitution of synonymous nucleotides and of nontranscribed nucleotides downstream from the coding region is estimated as 1.5 x 10(-8) and 1.1 x 10(-8) substitutions/nucleotide/year, respectively. This rate is two to three times the maximal rate estimated for mammalian synonymous substitutions. 相似文献
10.