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101.
102.
Astringency of aqueous solutions of phenolic compounds (grape seed tannins,
tannic acid, catechin and gallic acid) increased upon addition of citric
acid, whereas the astringency of alum was reduced. Astringency of alum was
decreased equivalently by addition of equi-sour levels of lactic acid,
citric acid or hydrochloric acid. The difference between alum and the
phenolic compounds is speculated to result from chemical modifications
affecting binding of the astringents with oral proteins rather than
cognitive differences. Chelation of the aluminum ion in alum by acids
reduces its availability for interacting with salivary proteins or
epithelial proteins. In contrast, the increased astringency produced upon
acidification of phenolic compounds is speculated to result from the pH
driven increase in the affinity of the phenols for binding with proteins.
These results suggest that alum cannot be used interchangeably with
phenolic astringents in psychophysical studies.
相似文献
103.
DNA sequences complementary to human 7 SK RNA show structural similarities to the short mobile elements of the mammalian genome 总被引:8,自引:0,他引:8
S Murphy F Altruda E Ullu M Tripodi L Silengo M Melli 《Journal of molecular biology》1984,177(4):575-590
A complementary DNA clone of 7 SK RNA from HeLa cells was used to study the genomic organization of 7 SK sequences in the human genome. Genomic hybridizations and genomic clones show that 7 SK is homologous to a family of disperse repeated sequences most of which lack the 3' end of the 7 SK RNA sequence. Only few of the genomic K sequences are homologous to both 3' and 5' 7 SK probes and presumably include the gene(s) for 7 SK RNA. The sequence of four genomic 7 SK clones confirms that they are in most cases pseudogenes. Although Alu sequences are frequently found near the 3' and 5' end of K DNA, the sequences immediately flanking the pseudogenes are different in all clones studied. However, direct repeats were found flanking directly the K DNA or the K-Alu unit, suggesting that the K sequences alone or in conjunction with Alu DNA might constitute a mobile element. 相似文献
104.
Human 7SL RNA consists of a 140 nucleotide middle-repetitive sequence inserted in an alu sequence 总被引:43,自引:0,他引:43
We have cloned and sequenced a cDNA copy of in vitro-polyadenylated 7SL RNA of HeLa cells. The cloned fragment is 303 bp long and has a composite structure. A central block of 140 bp is homologous to a new set of human middle-repetitive sequences. This block appears to be inserted in an Alu consensus sequence, 100 bp from the 5' end and 40 bp from the 3' end of the Alu monomer. Two 6 bp direct repeats are found at the junction between the Alu flanking sequences and the central element. The analysis of several clones shows the existence of sequence microheterogeneity in the 5' portion of the molecule. The 7L DNA probably represents a subset of the Alu family of DNA, highly conserved in evolution. 相似文献
105.
Amino acids conserved in interleukin-1 receptors (IL-1Rs) and the Drosophila toll protein are essential for IL-1R signal transduction. 总被引:7,自引:0,他引:7
A Heguy C T Baldari G Macchia J L Telford M Melli 《The Journal of biological chemistry》1992,267(4):2605-2609
The cytoplasmic domain of the human T cell-type interleukin-1 receptor (hIL-1R) is not involved in the binding, internalization, or nuclear localization of interleukin-1 (IL-1), but is essential for signal transduction. We have previously localized a 50-amino acid region (residues 477-527) critical for IL-1-mediated activation of the interleukin-2 promoter in T cells. This region displays a striking degree of amino acid conservation in human, murine, and chicken IL-1Rs. Here we report the results of a site-directed mutational analysis of the cytoplasmic domain of the hIL-1R. We have introduced single-amino acid substitutions at positions conserved in all three receptors and at nonconserved positions and identified key amino acids for IL-1R function in signal transduction. Three basic (Arg431, Lys515, and Arg518) and 3 aromatic (Phe513, Trp514, and Tyr519) amino acids that are conserved in human, murine, and chicken IL-1Rs could not be replaced without abolishing IL-1R-mediated signal transduction. A substitution at another conserved position (Pro521) reduces significantly the ability of the IL-1R to transmit the IL-1 signal. Nonconserved residues could be replaced without affecting signal transduction. The cytoplasmic domain of the IL-1R is related to that of the Drosophila Toll protein, with a 26% identity and a 43% similarity in amino acid sequence. The amino acids shown to be essential for IL-1R function are conserved in the Toll protein. Our experimental data indicate that the amino acid sequence similarity between the IL-1R and the Drosophila toll protein reflects a functional homology between the two proteins. 相似文献
106.
This report describes a lysozyme expressed at high levels in the stomach of
the hoatzin, the only known foregut-fermenting bird. Evolutionary
comparison places it among the calcium-binding lysozymes rather than among
the conventional types. Conventional lysozymes were recruited as digestive
enzymes twice in the evolution of mammalian foregut fermenters, and these
independently recruited lysozymes share convergent structural changes
attributed to selective pressures in the stomach. Biochemical convergence
and parallel amino acid replacements are observed in the hoatzin stomach
lysozyme even though it has a different genetic origin from the mammalian
examples and has undergone more than 300 million years of independent
evolution.
相似文献
107.
Dabritz HA Gardner IA Miller MA Lappin MR Atwill ER Packham AE Melli AC Conrad PA 《The Journal of parasitology》2007,93(4):806-816
We evaluated the sensitivity (Se) and specificity (Sp) of an IgG enzyme-linked immunosorbent assay (ELISA) and IgG indirect fluorescent antibody test (IFAT) for detection of Toxoplasma gondii-specific antibodies in sera from 2 cat populations using a Bayesian approach. Accounting for test covariance, the Se and Sp of the IgG ELISA were estimated to be 92.6% and 96.5%, and those of the IgG IFAT were 81.0% and 93.8%, respectively. Both tests performed poorly in cats experimentally coinfected with feline immunodeficiency virus and T. gondii. Excluding this group, Se and Sp of the ELISA were virtually unchanged (92.3% and 96.4%, respectively), whereas the IFAT Se improved to 94.2% and Sp remained stable at 93.7%. These tests and an IgM ELISA were applied to 123 cat sera from the Morro Bay area, California, where high morbidity and mortality attributable to toxoplasmosis have been detected in southern sea otters. Age-adjusted IgG seroprevalence in this population was estimated to be 29.6%, and it did not differ between owned and unowned cats. Accounting for Se, Sp, and test covariances, age-adjusted seroprevalence was 45.0%. The odds for T. gondii seropositivity were 12.3-fold higher for cats aged >12 mo compared with cats aged <6 mo. 相似文献
108.
Wainwright KE Lagunas-Solar M Miller MA Barr BC Gardner IA Pina C Melli AC Packham AE Zeng N Truong T Conrad PA 《Applied and environmental microbiology》2007,73(17):5663-5666
Inactivation of Toxoplasma gondii oocysts occurred with exposure to pulsed and continuous UV radiation, as evidenced by mouse bioassay. Even at doses of >or=500 mJ/cm2, some oocysts retained their viability. 相似文献
109.
110.
Yasuyuki Kobayashi Jon T Giles Masaharu Hirano Isamu Yokoe Yasuo Nakajima Joan M Bathon Joao AC Lima Hitomi Kobayashi 《Arthritis research & therapy》2010,12(5):R171