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排序方式: 共有352条查询结果,搜索用时 15 毫秒
1.
Are there proteins between the ribosomal subunits? Hot tritium bombardment experiments 总被引:1,自引:1,他引:0
The hot tritium bombardment technique [(1976) Dokl. Akad. Nauk SSSR 228, 1237-1238] was used for studying the surface localization of ribosomal proteins on Escherichia coli ribosomes. The degree of tritium labeling of proteins was considered as a measure of their exposure (surface localization). Proteins S1, S4, S7, S9 and/or S11, S12 and/or L20, S13, S18, S20, S21, L5, L6, L7/L12, L10, L11, L16, L17, L24, L26 and L27 were shown to be the most exposed on the ribosome surface. The sets of exposed ribosomal proteins on the surface of 70 S ribosomes, on the one hand, and the surfaces of 50 S and 30 S ribosomal subunits in the dissociated state, on the other, were compared. It was found that the dissociation of ribosomes into subunits did not result in exposure of additional ribosomal proteins. The conclusion was drawn that proteins are absent from the contacting surfaces of the ribosomal subunits. 相似文献
2.
Using the solid-phase translation system technique where template poly(U) is covalently coupled to Sepharose through cleavable disulfide bridges translating monoribosomes carrying a polypeptide (polyPhe) of 10 to 20 amino acids long have been isolated. Both pre-translocation state and post-translocation state ribosomes have been obtained. It has been shown that the sedimentation coefficient of the pre-translocation state ribosomes exceeds that of the post-translocation state ribosomes by a magnitude of about 1S. This difference is independent on the sedimentation rate (hydrostatic pressure) in the range of 20 000 to 40 000 rev/min and, most likely, is not a direct contribution of the increase of the particle mass at the expense of an additional tRNA in the pre-translocation state ribosomes. Together with other data, this result suggests that translating ribosomes in the pre-translocation state are more compact than post-translocation state ribosomes. 相似文献
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Anonymous nuclear DNA markers in the American oyster and their implications for the heterozygote deficiency phenomenon in marine bivalves 总被引:4,自引:0,他引:4
A puzzling population-genetic phenomenon widely reported in allozyme
surveys of marine bivalves is the occurrence of heterozygote deficits
relative to Hardy-Weinberg expectations. Possible explanations for this
pattern are categorized with respect to whether the effects should be
confined to protein-level assays or are genomically pervasive and expected
to be registered in both protein- and DNA-level assays. Anonymous nuclear
DNA markers from the American oyster were employed to reexamine the
phenomenon. In assays based on the polymerase chain reaction (PCR), two
DNA-level processes were encountered that can lead to artifactual genotypic
scorings: (a) differential amplification of alleles at a target locus and
(b) amplification from multiple paralogous loci. We describe symptoms of
these complications and prescribe methods that should generally help to
ameliorate them. When artifactual scorings at two anonymous DNA loci in the
American oyster were corrected, Hardy-Weinberg deviations registered in
preliminary population assays decreased to nonsignificant values.
Implications of these findings for the heterozygote-deficit phenomenon in
marine bivalves, and for the general development and use of PCR-based
assays, are discussed.
相似文献
6.
In vitro synthesis of firefly luciferase and its folding into an enzymatically active conformation were studied in a wheat germ cell-free translation system. A novel method is described by which the enzymatic activity of newly synthesized luciferase can be monitored continuously in the cell-free system while this protein is being translated from its mRNA. It is shown that ribosome-bound polypeptide chains have no detectable enzymatic activity, but that this activity appears within a few seconds after luciferase has been released from the ribosome. In contrast, the renaturation of denatured luciferase under identical conditions occurs with a half-time of 14 min. These results support the cotranslational folding hypothesis which states that the nascent peptides start to attain their native tertiary structure during protein synthesis on the ribosome. 相似文献
7.
Basolateral plasma membrane localization of ouabain-sensitive sodium transport sites in the secretory epithelium of the avian salt gland 下载免费PDF全文
The distribution of Na+ pump sites (Na+-K+-ATPase) in the secretory epithelium of the avian salt gland was demonstrated by freeze-dry autoradiographic analysis of [(3)H] ouabain binding sites. Kinetic studies indicated that near saturation of tissue binding sites occurred when slices of salt glands from salt-stressed ducks were exposed to 2.2 μM ouabain (containing 5 μCi/ml [(3)H]ouabain) for 90 min. Washing with label-free Ringer's solution for 90 min extracted only 10% of the inhibitor, an amount which corresponded to ouabain present in the tissue spaces labeled by [(14)C]insulin. Increasing the KCl concentration of the incubation medium reduced the rate of ouabain binding but not the maximal amount bound. In contrast to the low level of ouabain binding to salt glands of ducks maintained on a freshwater regimen, exposure to a salt water diet led to a more than threefold increase in binding within 9-11 days. This increase paralleled the similar increment in Na+-K+-ATPase activity described previously. [(3)H]ouabain binding sites were localized autoradiographically to the folded basolateral plasma membrane of the principal secretory cells. The luminal surfaces of these cells were unlabeled. Mitotically active peripheral cells were also unlabeled. The cell-specific pattern of [(3)H]ouabain binding to principal secretory cells and the membrane-specific localization of binding sites to the nonluminal surfaces of these cells were identical to the distribution of Na+-K+-ATPase as reflected by the cytochemical localization of ouabain-sensitive and K+-dependent nitrophenyl phosphatase activity. The relationship between the nonluminal localization of Na+-K+-ATPase and the possible role of the enzyme n NaCl secretion is considered in the light of physiological data on electrolyte transport in salt glands and other secretory epithelia. 相似文献
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旨在利用CRISPR/Cas9技术构建敲除花生四烯5-脂氧合酶基因(Arachidonate 5-lipoxygenase gene,ALOX5)的重组质粒。设计合成3对靶向敲除ALOX5第六外显子的sgRNA,将其分别插入到CRISPR/Cas9质粒骨架pX458载体中,转化感受态大肠杆菌DH5α后挑取克隆,通过测序评估重组质粒是否构建成功。将构建好的重组质粒转染293T细胞,在荧光显微镜下观察转染效果,挑取转染成功的细胞,用试剂盒提取转染细胞基因组DNA,PCR扩增含敲除位点的DNA片段,用测序技术获得核苷酸序列,用DNAStar软件分析转染细胞中ALOX5基因敲除情况。测序结果表明2对双链sgRNA寡核苷酸已插入质粒,且序列正确,靶向ALOX5基因的重组质粒pX458-sgRNAs-ALOX5构建成功。其在293T细胞中的转染效率约为50%,用一代测序法未检测到sgRNAs的切割效果。初步表明利用CRISPR/Cas9技术成功构建靶向ALOX5基因的重组质粒pX458-sgRNAs-ALOX5。 相似文献
10.
Molecular Biology - The mechanisms involved in the origin and development of malignant and neurodegenerative diseases are an important area of modern biomedicine. A crucial task is to identify new... 相似文献