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21.
Mfika Mubumbila Karl H.J. Gordon Edwin J. Crouse Gérard Burkard Jacques-Henry Weil 《Gene》1983,21(3):257-266
Construction of a physical map of the chloroplast DNA from Phaseolus vulgaris showed that this circular molecule is segmentally organized into four regions. Unlike other chloroplast DNAs which have analogous organization, two single-copy regions that separate two inverted repeats have been demonstrated to exist in both relative orientations, giving rise to two populations of DNA molecules.Hybridization studies using individual rRNA and tRNA species revealed the location of a set of rRNA genes and at least seven tRNA genes in each inverted repeat region, a minimum of 17 tRNA genes in the large single-copy region and one tRNA gene in the small single-copy region. The tRNA genes code for 24 tRNA species corresponding to 16 amino acids. Comparison of this gene map with those of other chloroplast DNAs suggests that DNA sequence rearrangements, involving some tRNA genes, have occurred. 相似文献
22.
The unusually long amino acid acceptor stem of Escherichia coli selenocysteine tRNA results from abnormal cleavage by RNase P. 总被引:6,自引:4,他引:2
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The nucleotide sequence of the gene encoding the Escherichia coli selenocysteine tRNA (tRNA(SeCys] predicts an unusually long acceptor stem of 8 base pairs (one more than other tRNAs). Here we show by in vivo experiments (Northern blots, primer extension analysis) and by in vitro RNA processing studies that E. coli tRNA(SeCys) does contain this additional basepair, and that its formation results from abnormal cleavage by RNase P. 相似文献
23.
Two sites of 5-hydroxytryptamine uptake in blood platelets 总被引:6,自引:0,他引:6
24.
A Mitogen-activated protein kinase controls differentiation of bloodstream forms of Trypanosoma brucei
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Domenicali Pfister D Burkard G Morand S Renggli CK Roditi I Vassella E 《Eukaryotic cell》2006,5(7):1126-1135
African trypanosomes undergo differentiation in order to adapt to the mammalian host and the tsetse fly vector. To characterize the role of a mitogen-activated protein (MAP) kinase homologue, TbMAPK5, in the differentiation of Trypanosoma brucei, we constructed a knockout in procyclic (insect) forms from a differentiation-competent (pleomorphic) stock. Two independent knockout clones proliferated normally in culture and were not essential for other life cycle stages in the fly. They were also able to infect immunosuppressed mice, but the peak parasitemia was 16-fold lower than that of the wild type. Differentiation of the proliferating long slender to the nonproliferating short stumpy bloodstream form is triggered by an autocrine factor, stumpy induction factor (SIF). The knockout differentiated prematurely in mice and in culture, suggestive of increased sensitivity to SIF. In contrast, a null mutant of a cell line refractory to SIF was able to proliferate normally. The differentiation phenotype was partially rescued by complementation with wild-type TbMAPK5 but exacerbated by introduction of a nonactivatable mutant form. Our results indicate a regulatory function for TbMAPK5 in the differentiation of bloodstream forms of T. brucei that might be exploitable as a target for chemotherapy against human sleeping sickness. 相似文献
25.
Thermodynamics of single mismatches in RNA duplexes 总被引:4,自引:0,他引:4
The thermodynamic properties and structures of single mismatches in short RNA duplexes were studied in optical melting and imino proton NMR experiments. The free energy increments at 37 degrees C measured for non-GU single mismatches range from -2.6 to 1.7 kcal/mol. These increments depend on the identity of the mismatch, adjacent base pairs, and the position in the helix. UU and AA mismatches are more stable close to a helix end, but GG mismatch stability is essentially unaffected by the position in the helix. Approximations are suggested for predicting stabilities of single mismatches in short RNA duplexes. 相似文献
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Free energies for stacking of unpaired nucleotides (dangling ends) at the termini of oligoribonucleotide Watson-Crick helixes (DeltaG(0)37,stack) depend on sequence for 3' ends but are always small for 5' ends. Here, these free energies are correlated with stacking at helix termini in a database of 34 RNA structures determined by X-ray crystallography and NMR spectroscopy. Stacking involving GA pairs is considered separately. A base is categorized as stacked by its distance from (=4.0 A), angle with (=30 degrees), and overlap with the terminal helix base-pair. A base is unstacked if it does not satisfy one or more of these criteria.Of the 36 unpaired bases in sequences with DeltaG(0)37,stackmore favorable than -0.7 kcal/mol, 30 (83 %) are stacked on the adjacent base-pair, indicating a propensity for such sequences to stack in the 3D structure. Structures containing the strongly stacked sequence [sequence: see text] show that the amino group of C closely overlaps the carbonyl-4 of U. Thermodynamic measurement of U stacking on a 2-pyrimidinone-guanine base-pair, where the amino group of C is replaced by hydrogen, suggests that interactions with the cytosine amino group contribute approximately 0.5 kcal/mol to DeltaG(0)37,stack.For GA mismatches at helix termini, the nucleotide at the 3' helix end is always stacked, and the nucleotide at the 5' end is stacked in almost 90 % of occurrences. In available structures, non-Watson-Crick paired bases 3' to an imino-hydrogen bonded GA are also always stacked; the GA provides a large platform for favorable stacking.For the 56 sequences associated with DeltaG(0)37,stackless favorable than -0.4 kcal/mol, 19 (34 %) are stacked; these sequences have a propensity for not stacking on adjacent base-pairs. Phylogenetic conservation of weakly stacking sequences at 3' ends may be a predictor of a backbone turn. 相似文献
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Pathogenic and non-pathogenic isolates of Streptococcus suis type 2 were screened to determine whether differences in superoxide dismutase (SOD) synthesis could explain the observed differences in their pathogenicity and intracellular fate in macrophages. A single band of SOD activity of similar Rf value was visualised in PAGE gels in all isolates and inhibition studies suggested that the cofactor present was manganese. There was no correlation between specific SOD activity and virulence. It is unlikely, therefore, that SOD produced by S. suis type 2 mediates intracellular survival of pathogenic isolates in macrophages. 相似文献
30.
Thomas R Burkard Melanie Planyavsky Ines Kaupe Florian P Breitwieser Tilmann Bürckstümmer Keiryn L Bennett Giulio Superti-Furga Jacques Colinge 《BMC systems biology》2011,5(1):17