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71.
We have shown by several independent criteria that actin is encoded by a very large and complex superfamily of genes in Petunia. Several cDNA and genomic probes encoding actins from diverse organisms (Dictyostelium, Drosophila, chicken and soybean) hybridize to hundreds of restriction fragments in the petunia genome. Actin-hybridizing sequences were isolated from a petunia genomic library at a rate of at least 200 per genome equivalent. Twenty randomly selected actin-hybridizing clones were characterized in more detail. DNA sequence data from four representative and highly divergent clones, PAc2, PAc3, PAc4 and PAc7, demonstrate that these actin-like sequences are related to functional actin genes. Intron positions typical of other known plant actin genes are conserved in these clones. Four of six clones analyzed (PAc1, PAc2, PAc3, PAc4) hybridize to leaf mRNA of the same size (1.7 kb) as that reported for other plant actin mRNAs and to a slightly smaller mRNA species (1.5 kb). Five distinct subfamilies of actin-related genes were characterized which varied in size from a few members to several dozen members. It is clear from our data that other actin gene subfamilies must also exist within the genome. Possible mechanisms of actin gene amplification and genome turnover are discussed. 相似文献
72.
Paired sequence difference in ribosomal RNAs: evolutionary and phylogenetic implications 总被引:12,自引:1,他引:11
Ribosomal RNAs have secondary structures that are maintained by internal
Watson-Crick pairing. Through analysis of chordate, arthropod, and plant 5S
ribosomal RNA sequences, we show that Darwinian selection operates on these
nucleotide sequences to maintain functionally important secondary
structure. Insect phylogenies based on nucleotide positions involved in
pairing and the production of secondary structure are incongruent with
those constructed on the basis of positions that are not. Furthermore,
phylogeny reconstruction using these nonpairing bases is concordant with
other, morphological data.
相似文献
73.
Michael McLean Wm. Vance Baird Anton G. M. Gerats Richard B. Meagher 《Plant molecular biology》1988,11(5):663-672
The actin gene superfamily of Petunia hybrida cv. Mitchell contains greater than 100 gene members which have been divided into several highly divergent subfamilies [1]. Five subfamily-specific probes have been used to compare the actin genes among the Mitchell, Violet 23 (V23) and Red 51 (R51) cultivars of P. hybrida. The sum total of actin genes in these five subfamilies was estimated to be between 10 and 34 members in both V23 and R51. Restriction fragment length polymorphisms (RFLPs) between V23 and R51 were examined with these five probes and eleven different restriction endonucleases. Among the 55 comparisons, 87% exhibited RFLPs. These data indicate extreme divergence between V23 and R51 in DNA sequence and/or the presence of small insertions and deletions surrounding these actin gene subfamilies. This divergence suggests that V23 and R51, which have contrasting phenotypic marker loci on every chromosome, may be useful for the development of a complete RFLP linkage map of the Petunia genome. The segregation of Hind III RFLPs among the progeny of two backcrosses demonstrated that representatives of the five subfamilies of Petunia actin genes exist at four distinct genetic locations and suggested that two of these loci are tightly linked. Apparently, amplification of the numerous members of the Petunia actin gene superfamily occurred via gene dispersal of the original subfamily progenitors and not primarily as a result of amplification of a single chromosomal region. 相似文献
74.
75.
Benjamin C. Buer Jennifer L. Meagher Jeanne A. Stuckey E. Neil G. Marsh 《Protein science : a publication of the Protein Society》2012,21(11):1705-1715
Highly fluorinated analogs of hydrophobic amino acids are well known to increase the stability of proteins toward thermal unfolding and chemical denaturation, but there is very little data on the structural consequences of fluorination. We have determined the structures and folding energies of three variants of a de novo designed 4‐helix bundle protein whose hydrophobic cores contain either hexafluoroleucine (hFLeu) or t‐butylalanine (tBAla). Although the buried hydrophobic surface area is the same for all three proteins, the incorporation of tBAla causes a rearrangement of the core packing, resulting in the formation of a destabilizing hydrophobic cavity at the center of the protein. In contrast, incorporation of hFLeu, causes no changes in core packing with respect to the structure of the nonfluorinated parent protein which contains only leucine in the core. These results support the idea that fluorinated residues are especially effective at stabilizing proteins because they closely mimic the shape of the natural residues they replace while increasing buried hydrophobic surface area. 相似文献
76.
77.
Histone H2A.Z Regulates the Expression of Several Classes of Phosphate Starvation Response Genes But Not as a Transcriptional Activator 总被引:1,自引:0,他引:1
78.
Malin C. Rivers Steven P. Bachman Thomas R. Meagher Eimear Nic Lughadha Neil A. Brummitt 《Biodiversity and Conservation》2010,19(7):2071-2085
Despite the ecological and economic importance of plants, the majority of plant species and their conservation status are
still poorly known. Based on the limited knowledge we have of many plant species, especially those in the tropics, the use
of GIS techniques can give us estimates of the degree of population subdivision to be used in conservation assessments of
extinction risk. This paper evaluates how best to use the IUCN Red List Categories and Criteria to produce effective and consistent
estimates of subpopulation structure based on specimen data available in the herbaria around the world. We assessed population
structure through GIS-based analysis of the geographic distribution of collections, using herbarium specimen data for 11 species
of Delonix sensu lato. We used four methods: grid adjacency, circular buffer, Rapoport’s mean propinquity and alpha hull, to quantify population
structure according to the terms used in the IUCN Red List: numbers of subpopulations and locations, and degree of fragmentation.
Based on our findings, we recommend using the circular buffer method, as it is not dependent on collection density and allows
points to be added, subtracted and/or moved without altering the buffer placement. The ideal radius of the buffer is debatable;
however when dispersal characteristics of the species are unknown then a sliding scale, such as the 1/10th maximum inter-point
distance, is the preferred choice, as it is species-specific and not sensitive to collection density. Such quantitative measures
of population structure provide a rigorous means of applying IUCN criteria to a wide range of plant species that hitherto
were inaccessible to IUCN classification. 相似文献
79.
Meagher MJ Schumacher JM Lee K Holdcraft RW Edelhoff S Disteche C Braun RE 《Gene》1999,228(1-2):197-211
In a screen for RNA binding proteins expressed during murine spermatogenesis, we cloned a novel, ancient zinc finger protein possessing a region common to a small class of RNA binding proteins. Zfr (zinc finger RNA binding) encodes a protein of 1052 amino acids with three widely spaced Cys2His2 zinc fingers. Outside of the zinc fingers, ZFR shares a region that is highly conserved between several RNA binding proteins containing copies of the double-stranded RNA binding motif. By northern blotting, Zfr is expressed at highest levels within the testis, ovary and brain. Immunohistochemistry and confocal microscopy were used to show that ZFR is highly expressed during meiosis I in males and females and is chromosome associated. Zfr is also expressed in Sertoli cells in the testis and granulosa cells in the ovary where it is localized to the nucleus. Using fluorescent in situ hybridization we mapped Zfr to chromosome 15 region A. ZFR appears to be an ancient protein, as apparent homologs exist in invertebrates (D. melanogaster) nematodes (C. elegans) and humans (H. sapiens). 相似文献