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71.
Evolution of eutherian cytochrome c oxidase subunit II: heterogeneous rates of protein evolution and altered interaction with cytochrome c 总被引:3,自引:1,他引:2
Cytochrome c oxidase subunit II (COII), encoded by the mitochondrial
genome, exhibits one of the most heterogeneous rates of amino acid
replacement among placental mammals. Moreover, it has been demonstrated
that cytochrome c oxidase has undergone a structural change in higher
primates which has altered its physical interaction with cytochrome c. We
collected a large data set of COII sequences from several orders of mammals
with emphasis on primates, rodents, and artiodactyls. Using phylogenetic
hypotheses based on data independent of the COII gene, we demonstrated that
an increased number of amino acid replacements are concentrated among
higher primates. Incorporating approximate divergence dates derived from
the fossil record, we find that most of the change occurred independently
along the New World monkey lineage and in a rapid burst before apes and Old
World monkeys diverged. There is some evidence that Old World monkeys have
undergone a faster rate of nonsynonymous substitution than have apes. Rates
of substitution at four-fold degenerate sites in primates are relatively
homogeneous, indicating that the rate heterogeneity is restricted to
nondegenerate sites. Excluding the rate acceleration mentioned above,
primates, rodents, and artiodactyls have remarkably similar nonsynonymous
replacement rates. A different pattern is observed for transversions at
four-fold degenerate sites, for which rodents exhibit a higher rate of
replacement than do primates and artiodactyls. Finally, we hypothesize
specific amino acid replacements which may account for much of the
structural difference in cytochrome c oxidase between higher primates and
other mammals.
相似文献
72.
E I Golub O V Kovalenko R C Gupta D C Ward C M Radding 《Nucleic acids research》1997,25(20):4106-4110
The cDNA for human protein HsRad54, which is a structural homolog of Saccharomyces cerevisiae recombination/repair protein Rad54, was cloned and expressed in Escherichia coli. As demonstrated by analysis in vitro and in vivo, HsRad54 protein interacts with human Rad51 recombinase. The interaction is mediated by the N-terminal domain of HsRad54 protein, which interacts with both free and DNA-bound HsRad51 protein. 相似文献
73.
Molecular evolution of cytochrome c oxidase: rate variation among subunit VIa isoforms 总被引:3,自引:1,他引:2
Schmidt TR; Jaradat SA; Goodman M; Lomax MI; Grossman LI 《Molecular biology and evolution》1997,14(6):595-601
Cytochrome c oxidase (COX) consists of 13 subunits, 3 encoded in the
mitochondrial genome and 10 in the nucleus. Little is known of the role of
the nuclear-encoded subunits, some of which exhibit tissue-specific
isoforms. Subunit VIa is unique in having tissue-specific isoforms in all
mammalian species examined. We examined relative evolutionary rates for the
COX6A heart (H) and liver (L) isoform genes along the length of the
molecule, specifically in relation to the tissue-specific function(s) of
the two isoforms. Nonsynonymous (amino acid replacement) substitutions in
the COX6AH gene occurred more frequently than in the ubiquitously expressed
COX6AL gene. Maximum-parsimony analysis and sequence divergences from
reconstructed ancestral sequences revealed that after the ancestral COX6A
gene duplicated to yield the genes for the H and L isoforms, the sequences
encoding the mitochondrial matrix region of the COX VIa protein experienced
an elevated rate of nonsynonymous substitutions relative to synonymous
substitutions. This is expected for relaxed selective constraints after
gene duplication followed by purifying selection to preserve the
replacements with tissue-specific functions.
相似文献
74.
Induction of chondrocyte vesiculation in vitro 总被引:1,自引:0,他引:1
E E Golub S C Schattschneider P Berthold A Burke I M Shapiro 《The Journal of biological chemistry》1983,258(1):616-621
75.
Biosynthesis of the Actinomycin Chromophore: Incorporation of 3-Hydroxy-4-Methylanthranilic Acid into Actinomycins by Streptomyces antibioticus 总被引:1,自引:0,他引:1 下载免费PDF全文
Actinomycin synthesis by washed mycelia of Streptomyces antibioticus has been conducted in the presence of 3-hydroxy-4-methylanthranilate-(carboxyl-14C). Incorporation of this compound into actinomycins has been observed, which constitutes further evidence that 3-hydroxy-4-methylanthranilate is an intermediate in actinomycin biosynthesis. The position of the incorporated label has been determined to be within the actinomycin chromophore, and the label appears to be equally distributed between both halves of the chromophore. Incidental to these findings was the observation that the 14C-labeled actinomycins were subject to rapid reabsorption by the organism with actinomycin V taken up preferentially to actinomycin IV. 相似文献
76.
Unrelated conjugative plasmids have sequences which are homologous to the leading region of the F factor. 总被引:5,自引:1,他引:4 下载免费PDF全文
Conjugative plasmids from various incompatibility groups which carry DNA homologous to the ssb gene of the F factor were found to have additional homology with the F factor. This region homologous with F was located on both sides of the ssb gene and occupied a considerable part of the leading region, i.e., the 12.9-kilobase portion of F transferred first during conjugation. This region was the only region of the F factor which has a homologous counterpart on many plasmids. 相似文献
77.
78.
Escherichia coli and Salmonella typhimurium supX genes specify deoxyribonucleic acid topoisomerase I. 总被引:11,自引:1,他引:10 下载免费PDF全文
Mutations of the Escherichia coli or Salmonella typhimurium supX genes eliminated deoxyribonucleic acid topoisomerase I. Suppression of a supX amber mutation partially restored the topoisomerase. Multicopy plasmids carrying supX+ caused overproduction of topoisomerase. Thus, these supX genes were identified as topA genes which specify deoxyribonucleic acid topoisomerase I. 相似文献
79.
80.
Timothy M. Anderson Yukihiro Ibayashi E. Carmack Holmes Sidney H. Golub 《Cancer immunology, immunotherapy : CII》1987,25(1):65-68
Summary The purpose of these studies was to compare local and systemic human lymphokine activated killer (LAK) and natural killer (NK) cytotoxic activity and to determine its modulation by biologic agents. Local immunity may be an important component in limiting local tumor growth. Therefore, as a model for studying immune function in the local compartment, we assessed NK activity of lymphocytes present at the site of human tumors and in peripheral blood (PBL). We extracted tumor infiltrating lymphocytes (TIL) and PBL from patients with pulmonary tumors and compared NK activity and response to the biological modifiers gamma interferon (IFN-), indomethacin (INDO), and interleukin 2 (IL-2). We also studied TIL and PBL LAK activity using the NK-resistant M14 target cells and determined the TIL response to IL-2, plus IFN-. Titration of K562 targets in a 51Cr release assay revealed that untreated TIL have low cytotoxicity (4.32%) compared to untreated PBL (34.3%, P=<0.001). This low level of TIL NK activity was not affected by IFN-, INDO, or IL-2 at 1 h. However, at 3 days of culture, IL-2 with or without exogenous IFN- significantly increased TIL NK ctotoxicity (20.5%, P=0.02 without IFN- and 32.52 lytic units (LU), P=<0.02 with IFN-). Untreated TIL and PBL both had low cytotoxicity against M14 targets (1.08 LU and 1.26 LU), respectively. After 3 days culture with IL-2 plus IFN-, both TIL and PBL LAK cytotoxicity were increased (14.34 LU and 40.63 LU). We conclude that local NK and LAK activity is intrinsically low. However, this activity can be modulated by biologic agents, thus giving hope for the development of local antitumor effectors capable of in vivo tumor control. 相似文献