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1.
A scrutiny of the literature shows that the ctenophore Haeckelia (= Euchlora) ruba has only kleptocnidae and that Hydroctena salenskii is a ctenophore without special cnidarian affinities. The “missing links” between cnidarians and ctenophores have thus turned out to be based on misinterpretations and must be excluded from future discussions on phylogeny. 相似文献
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Putrescine, spermidine, and spermine content were analysed inzygotic embryos of barley (Hordeum vulgare L.). Changes in polyaminecontent were observed during zygotic embryo growth. In two cultivars,Bomi and Golden Promise, the totalpolyamine content in the embryos was 2.62.9 nmol mg1fresh weight 10 d after anthesis, the highest content observed.It dropped to 1.3 nmol mg1 fresh weight 14 d after anthesis.This drop was caused by decreases in all three polyamine concentrations.From 14 to 35 d after anthesis the putrescine content continuedto decrease while the spermidine and spermine content increased,thus the total polyamine content remained constant until 35d after anthesis. The mutant Ris? 1508 showeda constant polyamine content around 1.3 nmol mg1 freshweight from 14 to 35 d after anthesis. The polyamine patternwas conserved in all three lines throughout the period of investigationshowing a spermidine content higher than putrescine contentwhich was, in turn, higher or equal to the spermine content.The polyamine content measured as nmol µg1 proteindecreased from 14 to 21 d post anthesis in all three lines,because the protein content (µg mg1 fresh weight)increased during the period. In dedifferentiating zygotic embryoscultured in vitro the putrescine content (nmol mg1 freshweight) rose by a factor of nine and the spermidine contentdoubled within the first week of cultivation, whereas sperminecontent did not change. For embryoderived calli a repeated patternof change in polyamine content was observed throughout the subculturingperiod. Key words: Polyamines, Hordeum vulgare L., embryo development 相似文献
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The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
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K.H. NIELSEN R.S.W. TSANG 《Journal of Rapid Methods and Automation in Microbiology》1992,1(3):227-239
The analytical sensitivities of three different enzyme linked immunoassays (ELISA), two competitive and a capture format were assessed. the assay systems employed monoclonal antibodies to Salmonella lipopolysaccharide (LPS) outer core epitopes to detect crude LPS antigens from Salmonella typhimurium. the most sensitive ELISA was the capture procedure, being capable of detection 1.3 ng/ml of LPS. This technique, however also gave the greatest between-test variation and as a result, the lowest amount that could be detected with a 95% confidence limit was actually 12.8 ng/ml and it took the longest time to perform (3 h, 30 min). A competitive ELISA using limiting monoclonal antibody to compete between solid phase antigen and soluble antigen in the sample, ranked second in sensitivity, and can detect 2.8 and 3.8 ng/ml of LPS when tested with two different monoclonal antibodies. However, because of the slight between test variation, the actual sensitivities that could be detected with a 95% confidence limit were 3.1 and 4.6 ng/ml, respectively. This test takes approximately 1 h and 30 min to perform.
The classical type of competitive assay, employing a labelled antigen, was the least sensitive being capable of detecting 5.8 ng/ml if the LPS was conjugated with horseradish peroxidase and 16.0 ng/ml if alkaline phosphatase was used as a label. to account for the between-test variation, the sensitivities with a 95% confidence limit were 8.6 and 18.7 ng/ml for the respective assays, which take 2 h and 15 min to perform.
These sensitivities compare favorably with those published for similar assays, but all of the procedures were judged insufficiently sensitive for direct use on food samples to be tested for the presence of Salmonella species. However, the assays would be quite suitable for demonstration of Salmonella sp. after an enrichment procedure. 相似文献
The classical type of competitive assay, employing a labelled antigen, was the least sensitive being capable of detecting 5.8 ng/ml if the LPS was conjugated with horseradish peroxidase and 16.0 ng/ml if alkaline phosphatase was used as a label. to account for the between-test variation, the sensitivities with a 95% confidence limit were 8.6 and 18.7 ng/ml for the respective assays, which take 2 h and 15 min to perform.
These sensitivities compare favorably with those published for similar assays, but all of the procedures were judged insufficiently sensitive for direct use on food samples to be tested for the presence of Salmonella species. However, the assays would be quite suitable for demonstration of Salmonella sp. after an enrichment procedure. 相似文献
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