全文获取类型
收费全文 | 125篇 |
免费 | 14篇 |
国内免费 | 3篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 12篇 |
2012年 | 4篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 4篇 |
2008年 | 6篇 |
2007年 | 2篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2002年 | 1篇 |
2001年 | 8篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 9篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1967年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有142条查询结果,搜索用时 15 毫秒
91.
Small-subunit ribosomal RNA sequence from Naegleria gruberi supports the polyphyletic origin of amoebas 总被引:2,自引:0,他引:2
We have sequenced the small-subunit ribosomal RNA gene of the amoebo-
flagellate protozoan Naegleria gruberi. Comparison of this sequence with
the rRNA sequences of other eukaryotes resulted in a phylogenetic tree that
supports the suggested polyphyletic origin of amoebas and suggests a
flagellate ancestry for Naegleria.
相似文献
92.
Cross-hybridizing snake satellite, Drosophila, and mouse DNA sequences may have arisen independently 总被引:2,自引:0,他引:2
Previous reports have interpreted hybridization between snake satellite DNA
and DNA clones from a variety of distant taxonomic groups as evidence for
evolutionary conservation, which implies common ancestry (homology) and/or
convergence (analogy) to produce the cross- hybridizing sequences. We have
isolated 11 clones from a genomic library of Drosophila melanogaster, using
a cloned 2.5-kb snake satellite probe of known nucleotide sequence. We have
also analysed published sequence data from snakes, mice, and Drosophila.
These data show that (1) all of the cross-hybridization between the snake,
fly, and mouse clones can be accounted for by the presence of either of two
tandem repeats, [GATA]n and [GACA]n and (2) these tandem repeats are
organized differently among the different species. We find no evidence that
these sequences are homologous apart from the existence of the simple
repeat itself, although their divergence from a common ancestral sequence
cannot be ruled out. The sequences contain a variety of homogeneous
clusters of tandem repeats of CATA, GA, TA, and CA, as well as GATA and
GACA. We suggest that these motifs may have arisen by a self-accelerating
process involving slipped-strand mispairing of DNA. Homogeneity of the
clusters might simply be the result of a rate of accumulation of tandem
repeats that exceeds that of other mutations.
相似文献
93.
Purification of galectin-3 from ovine placenta: developmentally regulated expression and immunological relevance 总被引:2,自引:1,他引:1
Iglesias MM; Rabinovich GA; Ambrosio AL; Castagna LF; Sotomayor CE; Wolfenstein-Todel C 《Glycobiology》1998,8(1):59-65
Galectins, beta-galactoside-binding lectins, are extensively distributed in
the animal kingdom and share some basic molecular properties. Galectin-3, a
member of this family, is generally associated with differentiation,
morphogenesis, and metastasis. In this study, galectin-3 was isolated from
ovine placental cotyledons round the middle of the gestation period by
lactose extraction followed by affinity chromatography on lactosyl-agarose,
and separated from galectin-1 by size exclusion chromatography on a
Superose 12 column. Under native conditions this lectin behaved as a
monomer with an apparent molecular weight of approximately 29,000 and an
isoelectric point of 9.0. The partial amino acid sequence of the peptides
obtained by tryptic digestion of this protein followed by HPLC separation
showed striking homology with other members of the galectin-3 subfamily.
Furthermore, ovine placental galectin-3 exhibited specific mitogenic
activity toward rat spleen mononuclear cells. Besides, this protein
strongly reacted with a rabbit antiserum raised against a chicken galectin.
Results obtained by Western blot analysis showed that its expression was
greatly decreased in term placenta with respect to the middle of the
gestation period, suggesting a regulated expression throughout development.
相似文献
94.
Taxol from fungal endophytes and the issue of biodiversity 总被引:7,自引:0,他引:7
GA Strobel WM Hess E. Ford RS Sidhu X Yang 《Journal of industrial microbiology & biotechnology》1996,17(5-6):417-423
Fungi represent one of the most understudied and diverse group of organisms. Commonly, these organisms make associations with higher life forms and may proceed to biochemically mimic the host organism. An excellent example of this is the anticancer drug, taxol, which had been previously supposed to occur only in the plant genusTaxus (yew). However, taxol has been reported in a novel endophytic fungus—Taxomyces andreanae, but also has been demonstrated to occur in a number of unrelated fungal endophytes includingPestalotia, Pestalotiopsis, Fusarium, Alternaria, Pithomyces, Monochaetia and others. Thus, this report presents information on the presence of taxol among disparate fungal genera, and uses these observations as an additional argument to support efforts to study fungal endophytes and preserve their associated host plants. 相似文献
95.
96.
Gary Cobbs 《Genetics》1976,82(1):53-62
Three new alleles are reported at the esterase-5 locus of Drosophila pseudoobscura. All three of these alleles are different from those previously reported in their ability to dimerize. One allele will not form heterodimers or homodimers and exists only as a monomer. A second allele does form heterodimers but will not form homodimers. The third allele forms both hetero- and homodimers as well as forming monomers. Estimates of the frequency of these alleles in a natural population are given. The existence of these is discussed with respect to recently proposed models for a molecular mechanism for heterosis. 相似文献
97.
G Cobbs 《The Journal of heredity》1992,83(2):81-84
Frequencies of sex chromosome aneuploid sperm were measured for standard and "sex-ratio" Drosophila pseudoobscura males with identical genetic backgrounds. The "sex-ratio" males produced a 15.6-fold higher frequency of nullo-XY sperm than the standard males produced, but diplo-XY sperm were produced at the same rate in the two types of males. "Sex-ratio" males with the same SR chromosome but with different chromosome backgrounds were found to produce different frequencies of sterile sons. These results indicate that strains of D. pseudoobscura differ at autosomal or Y-linked modifiers of sr. Such modifiers are similar to the msr genes found in the L116 strain of this species. 相似文献
98.
Very few silver grains were seen on the cell surface and none intracellularly after incubation for 2 h at 4 degrees C. However, numerous grains were seen in various subcellular organelles when the tissues were incubated for 2 h at 22 degrees or 38 degrees C. The grain distribution was qualitatively similar, but quantitatively, there were fewer grains at 22 degrees than at 38 degrees C. Co-incubation of 125I-hCG with excess unlabelled hCG resulted in the virtual disappearance of silver grains from all the subcellular organelles. Excess unlabelled human luteinizing hormone (but not follicle-stimulating hormone or prolactin) inhibited the appearance of silver grains in luteal tissue. There were no silver grains in bovine liver slices incubated with 125I-hCG. The plasma membrane-associated grains progressively decreased, while intracellular organelle-associated grains increased with time at 38 degrees C. There were no grains in nuclei at 5 min, but they appeared at 10 min and increased until 120 min. After correction for radiation spread by three-step mask analysis, smooth endoplasmic reticulum and mitochondria did not contain any grains. The grain density was the highest in Golgi, followed by lysosomes, rough endoplasmic reticulum, nuclei, and plasma membranes after incubation for 2 h at 38 degrees C. Thus, the electron microscope autoradiography approach confirmed our biochemical data in the preceding paper (Chegini et al., Exp cell res 151 (1984) 466 [5]) on time, temperature dependency and specificity of 125I-hCG internalization, association of internalized hormone with a variety of intracellular organelles, and the highest uptake in Golgi. 相似文献
99.
VJ Lara-Diaz I Castilla-Cortazar I Martín-Estal M García-Magariño GA Aguirre JE Puche RG de la Garza LA Morales U Muñoz 《Journal of physiology and biochemistry》2017,73(2):245-258
Even though the liver synthesizes most of circulating IGF-1, it lacks its receptor under physiological conditions. However, according to previous studies, a damaged liver expresses the receptor. For this reason, herein, we examine hepatic histology and expression of genes encoding proteins of the cytoskeleton, extracellular matrix, and cell-cell molecules and inflammation-related proteins. A partial IGF-1 deficiency murine model was used to investigate IGF-1’s effects on liver by comparing wild-type controls, heterozygous igf1+/?, and heterozygous mice treated with IGF-1 for 10 days. Histology, microarray for mRNA gene expression, RT-qPCR, and lipid peroxidation were assessed. Microarray analyses revealed significant underexpression of igf1 in heterozygous mice compared to control mice, restoring normal liver expression after treatment, which then normalized its circulating levels. IGF-1 receptor mRNA was overexpressed in Hz mice liver, while treated mice displayed a similar expression to that of the controls. Heterozygous mice showed overexpression of several genes encoding proteins related to inflammatory and acute-phase proteins and underexpression or overexpression of genes which coded for extracellular matrix, cytoskeleton, and cell junction components. Histology revealed an altered hepatic architecture. In addition, liver oxidative damage was found increased in the heterozygous group. The mere IGF-1 partial deficiency is associated with relevant alterations of the hepatic architecture and expression of genes involved in cytoskeleton, hepatocyte polarity, cell junctions, and extracellular matrix proteins. Moreover, it induces hepatic expression of the IGF-1 receptor and elevated acute-phase and inflammation mediators, which all resulted in liver oxidative damage. 相似文献
100.
J B Perkins A Sloma T Hermann K Theriault E Zachgo T Erdenberger N Hannett N P Chatterjee V Williams II GA Rufo Jr R Hatch J Pero 《Journal of industrial microbiology & biotechnology》1999,22(1):8-18
Recombinant DNA engineering was combined with mutant selection and fermentation improvement to develop a strain of Bacillus subtilis that produces commercially attractive levels of riboflavin. The B. subtilis riboflavin production strain contains multiple copies of a modified B. subtilis riboflavin biosynthetic operon (rib operon) integrated at two different sites in the B. subtilis chromosome. The modified rib operons are expressed constitutively from strong phage promoters located at the 5′ end and in an internal region of the operon.
The engineered strain also contains purine analog-resistant mutations designed to deregulate the purine pathway (GTP is the
precursor for riboflavin), and a riboflavin analog-resistant mutation in ribC that deregulates the riboflavin biosynthetic pathway.
Received 22 June 1998/ Accepted in revised form 6 November 1998 相似文献