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排序方式: 共有118条查询结果,搜索用时 15 毫秒
1.
Donald J. Brasch Hi Mui Chang Chaw T. Chuah Laurence D. Melton 《Carbohydrate research》1981,97(1):113-125
A galactan sulfate has been isolated from the seaweed Porphyra columbina, and its structure established by a combination of methylation, methanolysis, treatment with alkali followed by methylation, and 13C-n.m.r. spectroscopy. The polysaccharide belongs to the porphyran class, and consists of 3-linked β-d-galactosyl residues and 4-linked α-l-galactosyl residues. 3,6-Anhydro-l-galactose and l-galactose 6-sulfate residues total approximately half of the sugar units, the other half being made up of d-galactose and 6-O-methyl-d-galactose residues. Some evidence is presented that suggests that the galactan sulfate does not have a completely alternating structure. 相似文献
2.
Olendzenski L Liu L Zhaxybayeva O Murphey R Shin DG Gogarten JP 《Journal of molecular evolution》2000,51(6):587-599
Members of the Deinococcaceae (e.g., Thermus, Meiothermus, Deinococcus) contain A/V-ATPases typically found in Archaea or Eukaryotes which were probably acquired by horizontal gene transfer. Two methods were used to quantify the extent to which archaeal or eukaryotic genes have been acquired by this lineage. Screening of a Meiothermus ruber library with probes made against Thermoplasma acidophilum DNA yielded a number of clones which hybridized more strongly than background. One of these contained the prolyl tRNA synthetase (RS) gene. Phylogenetic analysis shows the M. ruber and D. radiodurans prolyl RS to be more closely related to archaeal and eukaryal forms of this gene than to the typical bacterial type. Using a bioinformatics approach, putative open reading frames (ORFs) from the prerelease version of the D. radiodurans genome were screened for genes more closely related to archaeal or eukaryotic genes. Putative ORFs were searched against representative genomes from each of the three domains using automated BLAST. ORFs showing the highest matches against archaeal and eukaryotic genes were collected and ranked. Among the top-ranked hits were the A/V-ATPase catalytic and noncatalytic subunits and the prolyl RS genes. Using phylogenetic methods, ORFs were analyzed and trees assessed for evidence of horizontal gene transfer. Of the 45 genes examined, 20 showed topologies in which D. radiodurans homologues clearly group with eukaryotic or archaeal homologues, and 17 additional trees were found to show probable evidence of horizontal gene transfer. Compared to the total number of ORFs in the genome, those that can be identified as having been acquired from Archaea or Eukaryotes are relatively few (approximately 1%), suggesting that interdomain transfer is rare. 相似文献
3.
Seth M Dever E Railey White Matthew CT Hartman Kristoffer Valerie 《Cell cycle (Georgetown, Tex.)》2012,11(4):687-694
Despite intense studies, questions still remain regarding the molecular mechanisms leading to the development of hereditary breast and ovarian cancers. Research focused on elucidating the role of the breast cancer susceptibility gene 1 (BRCA1) in the DNA damage response may be of the most critical importance to understanding these processes. The BRCA1 protein has an N-terminal RING domain possessing E3 ubiquitin-ligase activity and a C-terminal BRCT domain involved in binding specific phosphoproteins. These domains are involved directly or indirectly in DNA double-strand break (DSB) repair. As the two terminal domains of BRCA1 represent two separate entities, understanding how these domains communicate and are functionally altered in regards to DSB repair is critical for understanding the development of BRCA1-related breast and ovarian cancers and for developing novel therapeutics. Herein, we review recent findings of how altered functions of these domains might lead to cancer through a mechanism of increased aberrant homologous recombination and possible implications for the development of BRCA1 inhibitors.Key words: BRCT, DNA repair, peptide, radiation, RING, ubiquitylation 相似文献
4.
Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
5.
Inhibition of clinical human immunodeficiency virus (HIV) type 1 isolates in primary CD4+ T lymphocytes by retroviral vectors expressing anti-HIV genes. 总被引:1,自引:3,他引:1 下载免费PDF全文
T Vandendriessche M K Chuah L Chiang H K Chang B Ensoli R A Morgan 《Journal of virology》1995,69(7):4045-4052
Gene therapy may be of benefit in human immunodeficiency virus type 1 (HIV-1)-infected individuals by virtue of its ability to inhibit virus replication and prevent viral gene expression. It is not known whether anti-HIV-1 gene therapy strategies based on antisense or transdominant HIV-1 mutant proteins can inhibit the replication and expression of clinical HIV-1 isolates in primary CD4+ T lymphocytes. We therefore transduced CD4+ T lymphocytes from uninfected individuals with retroviral vectors expressing either HIV-1-specific antisense-TAR or antisense-Tat/Rev RNA, transdominant HIV-1 Rev protein, and a combination of antisense-TAR and transdominant Rev. The engineered CD4+ T lymphocytes were then infected with four different clinical HIV-1 isolates. We found that replication of all HIV-1 isolates was inhibited by all the anti-HIV vectors tested. Greater inhibition of HIV-1 was observed with transdominant Rev than with antisense RNA. We hereby demonstrated effective protection by antisense RNA or transdominant mutant proteins against HIV-1 infection in primary CD4+ T lymphocytes using clinical HIV-1 isolates, and this represents an essential step toward clinical anti-HIV-1 gene therapy. 相似文献
6.
A new fourier transform approach for protein coding measure based on the format of the Z curve 总被引:2,自引:0,他引:2
MOTIVATION: At the core of most protein gene-finding algorithms are the
coding measures used to make a decision on coding/non-coding. Of the
protein coding measures, the Fourier measure is one of the most important.
However, due to the limited length of the windows usually used, the
accuracy of the measure is not satisfactory. This paper is devoted to
improving the accuracy by lengthening the sequence to amplify the
periodicity of 3 in the coding regions. RESULTS: A new algorithm is
presented called the lengthen-shuffle Fourier transform algorithm. For the
same window length, the percentage accuracy of the new algorithm is 6-7%
higher than that of the ordinary Fourier transform algorithm. The resulting
percentage accuracy (average of specificity and sensitivity) of the new
measure is 84.9% for the window length 162 bp. AVAILABILITY: The program is
available on request fromC.- T. Zhang. Contact: ctzhang@tju.edu.cn
相似文献
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9.
Chuah SC Moore PK Zhu YZ 《American journal of physiology. Heart and circulatory physiology》2007,293(5):H2693-H2701
S-allylcysteine (SAC) is an organosulfur-containing compound derived from garlic. Studies have shown that garlic is beneficial in the treatment of cardiovascular diseases. This study aims to elucidate if SAC is responsible for this cardioprotection using acute myocardial infarction (AMI) rat models. In addition, we hypothesized that SAC may mediate cardioprotection via a hydrogen sulfide (H(2)S)-related pathway. Rats were pretreated with saline, SAC (50 mg x kg(-1) x day(-1)), SAC + propagylglycine (PAG; 50 mg + 10 mg x kg(-1) x day(-1)) or PAG (10 mg x kg(-1) x day(-1)) for 7 days before AMI induction and killed 48 h after. Our results showed that SAC significantly lowered mortality (12.5% vs. 33.3%, P < 0.05) and reduced infarct size. SAC + PAG- and PAG-treated rats had larger infarct sizes than controls (60.9 +/- 0.01 and 62.0 +/- 0.03%, respectively, vs. 50.0 +/- 0.03%; P < 0.05). Pretreatment with SAC did not affect BP, but BP was significantly elevated in SAC + PAG and PAG-treated groups (P < 0.05). In addition, plasma H(2)S levels and left ventricular cystathionine-gamma-lyase (CSE) activities were analyzed to investigate the involvement of H(2)S. CSE is the enzyme responsible for H(2)S production in the heart. SAC increased left ventricular CSE activity in AMI rats (2.75 +/- 0.34 vs. 1.23 +/- 0.16 micromol x g protein(-1) x h(-1); P < 0.01). SAC + PAG-treated rats had significantly lower CSE activity compared with the SAC-treated group (1.22 +/- 0.27 vs. 2.75 +/- 0.34 micromol x g protein(-1) x h(-1); P < 0.05). Similarly, SAC-treated rats had higher plasma H(2)S concentration compared with controls and the SAC + PAG-treated group. Protein expression studies revealed that SAC upregulated CSE expression (1.1-fold of control; P < 0.05), whereas SAC + PAG and PAG downregulated its expression (0.88-fold of control in both groups; P < 0.005). In conclusion, our study provides novel evidence that SAC is protective in myocardial infarction via an H(2)S-related pathway. 相似文献
10.
Calcium-dependent and phosphorylation-stimulated proteolysis of lipocortin I by an endogenous A431 cell membrane protease 总被引:2,自引:0,他引:2
Purified placental lipocortin I but not lipocortin II was proteolyzed during A431 cell membrane-catalyzed phosphorylation reactions. Proteolysis was Ca2+-dependent but was not prevented in the presence of a variety of inhibitors of Ca2+-dependent proteases, suggesting that the Ca2+ effect is a property of lipocortin I itself. Proteolysis was inhibited by Triton X-100 or dithiothreitol and was temperature-dependent, occurring at 30 degrees C but not at 0 degrees C. Tyrosine phosphorylation and proteolysis are distinct events as both phosphorylated and nonphosphorylated lipocortins could be cleaved by the membrane protease, but prephosphorylation enhanced the rate of proteolysis 2-fold during the initial reaction and by 60 min almost half of the phosphorylated lipocortin was proteolyzed. Cleavage of the 38-kDa phosphotyrosyl lipocortin I generated a truncated 37-kDa form of lipocortin which retained the phosphate label, indicating that proteolysis occurred at a site N-terminal to the site of tyrosine phosphorylation, possibly at tryptophan 12. Ando, Y., Imamura, S., Hong, Y.-M., Owada, M.K., Kakunaga, T., and Kannagi, R. [1989) J. Biol. Chem. 264, 6948-6955) have recently reported that in vitro cleavage at sites in the N-terminal tail region of lipocortin I by exogenously added proteases dramatically enhanced the Ca2+ sensitivity of phospholipid binding by lipocortin. The demonstrated ability of an endogenous membrane protease to catalyze a similar and specific cleavage in a Ca2+-dependent manner indicates that this event may occur in the cell where it would have important effects on the functional properties of lipocortin I. 相似文献