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排序方式: 共有65条查询结果,搜索用时 31 毫秒
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Developmental and tissue-specific expression of U4 small nuclear RNA genes. 总被引:6,自引:1,他引:5
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U4 RNA is one of several small nuclear RNAs involved in the splicing of mRNA precursors. The domestic chicken has two genes per haploid genome that are capable of encoding U4 RNA. The U4X RNA gene (which encodes a sequence variant of U4 RNA that was unknown prior to the cloning of the gene) and the U4B RNA gene were both expressed in vivo in each of seven adult and three embryonic chicken tissues examined. However, the ratio of U4B RNA to U4X RNA can vary more than sevenfold in both a tissue- and stage-specific manner. 相似文献
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A chicken middle-repetitive DNA sequence which shares homology with mammalian ubiquitous repeats. 总被引:19,自引:8,他引:11
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We have identified and sequenced two members of a chicken middle repetitive DNA sequence family. By reassociation kinetics, members of this family (termed CRl) are estimated to be present in 1500-7000 copies per chicken haploid genome. The first family member sequenced (CRlUla) is located approximately 2 kb upstream from the previously cloned chicken Ul RNA gene. The second CRl sequence (CRl)Va) is located approximately 12 kb downstream from the 3' end of the chicken ovalbumin gene. The region of homology between these two sequences extends over a region of approximately 160 base pairs. In each case, the 160 base pair region is flanked by imperfect, but homologous, short direct repeats 10-15 base pairs in length. When the CRl sequences are compared with mammalian ubiquitous interspersed repetitive DNA sequences (human Alu and Mouse Bl families), several regions of extensive homology are evident. In addition, the short nucleotide sequence CAGCCTGG which is completely conserved in ubiquitous repetitive sequence families from several mammalian species is also conserved at a homologous position in the chicken sequences. These data imply that at least certain aspects of the sequence and structure of these interspersed repeats must predate the avian-mammalian divergence. It seems that the CRl family may possibly represent an avian counterpart of the mammalian ubiquitous repeats. 相似文献
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DC Chhieng AR Frost S Niwas H Weiss WE Grizzle S Beeken 《Biotechnic & histochemistry》2013,88(1):25-36
Small biopsy samples are used increasingly to assess the biomarker expression for prognostic information and for monitoring therapeutic responses prior to and during neoadjuvant therapy. The issue of intratumor heterogeneity of expression of biomarkers, however, has raised questions about the validity of the assessment of biomarker expression based on limited tissue samples. We examined immunohistochemically the expression of HER-2neu (p185erbB-2), epidermal growth factor receptor (EGFR), Bcl-2, p53, and proliferating cell nuclear antigen (PCNA) in 30 breast carcinomas using archived, paraffin embedded tissue and determined the extent of intratumor heterogeneity. Each section was divided into four randomly oriented discrete regions, each containing a portion of the infiltrating carcinoma. For each tumor, the entire lesion and four regions were analyzed for the expression of these markers. Scores of both membrane and cytoplasmic staining of HER-2neu and EGFR, scores of cytoplasmic staining of Bcl-2, and scores of nuclear staining of both p53 and PCNA were recorded. The intensity of staining and the proportion of immunostained cells were determined. A semiquantitative immunoscore was calculated by determining the sum of the products of the intensity and corresponding proportion of stained tumor cells. We analyzed both invasive (IDC) and in situ (DCIS) carcinomas. The Wilcoxon signed-rank test was used for paired comparisons between overall and regional immunoscores and between overall and regional percentages of stained cells. Spearman's correlation coefficients were used to assess the level of agreement of overall biomarker expression with each of the regions. Generalized linear models were used to assess overall and pair-wise differences in the absolute values of percent changes between overall and regional expression of biomarkers. For IDCs, there were no statistically significant differences in the expression of the biomarkers in terms of either the percentage of cells staining or the immunoscores when comparing the entire tumor with each region except for the lower EGFR expression of arbitrarily selected region 1 and lower p53 expression of region 1 compared to that of the entire tumor section. For DCIS, there were no statistically significant differences in the expression of the biomarkers between the entire tumor and each region except in PCNA of region 2 compared to that of entire tumor section. Positive correlation of immunoscores was observed between the entire tumor and each region as well as across all four regions for IDC. Similar observations were noted with DCIS except for HER-2neu and PCNA. No statistically significant differences were observed in the absolute values of percent changes of biomarker expression between overall and the four regions for both DCIS and IDC. Therefore, no significant intratumor heterogeneity in the expression of HER-2neu, Bcl-2, and PCNA was observed in IDC. Minor regional variations were observed for EGFR and p53 in IDC. Similarly, no significant regional variation in the expression of markers was observed in DCIS except for PCNA. 相似文献
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Early evolution of metazoan serine/threonine and tyrosine kinases: identification of selected kinases in marine sponges 总被引:14,自引:1,他引:13
The phylum Porifera (sponges) was the first to diverge from the common
ancestor of the Metazoa. In this study, six cDNAs coding for protein-
serine/threonine kinases (PS/TKs) are presented; they have been isolated
from libraries obtained from the demosponges Geodia cydonium and Suberites
domuncula and from the calcareous sponge Sycon raphanus. Sequence
alignments of the catalytic domains revealed that two major families of
PS/TK, the "conventional" (Ca(2+)-dependent) protein kinase C (PKC), the
cPKC subfamily, as well as the "novel" (Ca(2+)- independent) PKC (nPKC),
form two separate clusters. In each cluster, the sequence from S. raphanus
diverges first. To approach the question about the origin of
protein-tyrosine kinases (PTK), which are found only in Metazoa, we
analyzed two additional PS/TKs which have been cloned from S. domuncula:
the stress-responsive protein kinase (KRSvSD) and the
protein-kinase-C-related kinase (PRKvSD). The construction of the
phylogenetic tree, comprising the eight PS/TKs and the PTK cloned
previously from G. cydonium, revealed that the PTK derived from the branch
including the KRSvSD kinase. These data facilitate the first molecular
approach to elucidate the origin of metazoan PTK within the PS/TK
superfamily.
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