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1.
Treatment with 5-azacytidine (5-aza-C) causes an advance in the time of replication and enhances the DNase-I sensitivity of the inactive X chromosome in Gerbillus gerbillus fibroblasts. We found that these changes were not stably inherited and upon removal of the drug the cells reverted to the original state of one active and one inactive X chromosome. In order to determine whether this reversion was random, we used a cell line of female Microtus agrestis fibroblasts in which the two X chromosomes are morphologically distinguishable. In this work we show that the reversion to a late pattern of replication is not random, and the originally late replicating X chromosome is preferentially reinactivated, suggesting an imprinting-like marking of one or both X chromosomes. The changes in the replication pattern of the X chromosome were associated with changes in total DNA methylation. Double treatment of cells with 5-aza-C did not alter this pattern of euchromatin activation and reinactivation. A dramatic advance in the time of replication of the entire X linked constitutive heterochromatin (XCH) region was however, observed in the doubly treated cells. This change in the replication timing of the XCH occurred in both X chromosomes and was independent of the changes observed in the euchromatic region. These observations suggest the existence of at least two independent regulatory sites which control the timing of replication of two large chromosomal regions.Deceased on 2 Jan. 1987 相似文献
2.
3.
Selective degradation of integrated murine leukemia proviral DNA by deoxyribonucleases 总被引:29,自引:0,他引:29
The sensitivity to micrococcal nuclease and DNAase I of the integrated proviral DNA sequences in Swiss mouse cells infected with Moloney murine leukemia virus has been studied. Chromatin was separated into micrococcal nuclease-sensitive and -resistant regions, and the amount of proviral sequences in these DNA preparations was estimated by kinetic hybridization with single-stranded complementary DNA of Moloney murine leukemia virus. At least two thirds of the proviral DNA sequences were found in the open regions of chromatin, and only one third was resistant to nuclease. The proviral DNA sequences are even more sensitive to deoxyribonuclease I. When intact nuclei were treated with limited amounts of enzyme, only 5% of the nuclear DNA was digested, whereas 48% of the proviral DNA was degraded.The proviral DNA sequences in cells which do not produce virus are more resistant to nuclease digestion, as compared to virus producer cells. Thus the endogenous proviral sequences, in normal uninduced Swiss mouse cells, are randomly distributed between resistant and sensitive portions of chromatin when tested with either micrococcal nuclease or pancreatic deoxyribonuclease I. The effect of cell cycle synchronization on the accessibility of the proviral sequences to pancreatic deoxyribonuclease I was investigated with rat cells infected with Moloney murine leukemia virus. The amount of proviral DNA sensitive to pancreatic deoxyribonuclease I is higher in actively dividing cells than in cells arrested at Go phase, which produce only small amounts of virus. 相似文献
4.
E. coli DNA methylase has been used to methylate chromatin DNA in vitro. At saturation only 50% of the chromatin DNA becomes methylated. The methylated regions of chromatin correspond to that fraction of the chromatin which is sensitive to staphylococcal nuclease. Using in vitro methylated chromatin followed by nuclease digestion movement of chromatin proteins along the DNA can be detected. By this criterion, sonication of chromatin or precipitation with MnCl2 causes 10% of the previously uncovered methylated regions to become covered by protein. Reconstitution of methylated chromatin results in the randomization of the chromatin proteins. Using nuclei which were methylated in vitro we have demonstrated that a small degree of protein sliding does occur during the preparation of chromatin from nuclei. Finally, we have prepared open region DNA by polylysine titration. This procedure does not cause displacement of chromatin proteins. 相似文献
5.
Cedar M. Chittenden Kevin G. Butterworth K. Fiona Cubitt Melinda C. Jacobs Adrian Ladouceur David W. Welch R. Scott McKinley 《Environmental Biology of Fishes》2009,84(1):129-140
Many coho salmon stocks (Oncorhynchus kisutch) have been in decline during the past three decades. Canada’s most endangered salmon stock, the Thompson River coho salmon,
is being studied extensively as managers attempt to reverse these population declines. Investigators are using acoustic telemetry
to track the migratory behaviour and survival of the Thompson River (and other) coho salmon stocks. Coho salmon pre-smolts
are relatively small compared with salmonid species that are typically studied using acoustic telemetry; therefore the identification
of the appropriate sizes of fish and tags to use is critical. This study tested the effects of surgically implanting the three
smallest sizes of acoustic tags currently available on the growth, survival, tag retention, swimming performance and physical
condition of coho salmon pre-smolts for 300 days post-surgery. Maximum tag size to body size ratios ranged from 15–17% by
fork length and 7–8% by mass for the three tag sizes (11 cm fork length for a 6 × 19 mm tag, 12.5 cm for a 7 × 19 mm tag,
and 14 cm for a 9 × 21 mm tag). Based on our results, it is unlikely that coho salmon pre-smolts implanted with acoustic transmitters
following these size guidelines would have poor survival in studies of freshwater migratory behaviour as a result of the surgery
or the tag. 相似文献
6.
应用酶联免疫吸附试验(ELISA)对307例自然人群和228例胃病患者的血清进行了抗幽门螺杆菌(HP)抗体的检测,同时与尿素酶试验和涂片镜检结果比较。结果:自然人群中HP抗体阳性率为14.66%,不同性别、职业、民族间HP抗体的阳性率无差异。各年龄组间HP抗体阳性率有随年龄增加而升高趋势。胃病患者HP抗体阳性率为61.41%,GMT为1:430.53,明显高于自然人群的14.66%,GMT 1:15783,两者差异显著。ELISA法与尿素酶试验和涂片镜检结果存在相关关系。认为ELISA法结果可靠,可用于人群普查及HP感染的诊断。 相似文献
7.
Cedar H. A. Boakye Ravi Doddapaneni Punit P. Shah Apurva R. Patel Chandraiah Godugu Stephen Safe Santosh K. Katiyar Mandip Singh 《PloS one》2013,8(8)
Background
The objective of this study was to demonstrate the anti-skin cancer and chemopreventive potential of 1,1-bis(3′-indolyl)-1-(p-chlorophenyl methane) (DIM-D) using an in vitro model.Methods
In vitro cell cytotoxicity and viability assays were carried out in A431 human epidermoid carcinoma cell line and normal human epidermal keratinocytes (NHEK) respectively by crystal violet staining. Apoptosis induction in A431 cells (DIM-D treated) and NHEK cells pretreated with DIM-D (2 hr) prior to UVB irradiation, were assessed. The accumulation of reactive oxygen species (ROS) in DIM-D pretreated NHEK cells (2 hr) prior to UVB exposure was also determined. Immunocytochemistry and western blot analysis was performed to determine cleaved caspase 3 and DNA damage markers in DIM-D treated A431 cells and in DIM-D pretreated NHEK cells prior to UVB irradiation.Results
The IC50 values of DIM-D were 68.7±7.3, 48.3±10.1 and 11.5±3.1 μM whilst for Epigallocatechin gallate (EGCG) were 419.1±8.3, 186.1±5.2 and 56.7±3.1 μM for 24, 48 and 72 hr treatments respectively. DIM-D exhibited a significantly (p<0.05) greater induction of DNA fragmentation in A431 cells compared to EGCG with percent cell death of 38.9. In addition, DIM-D induced higher expression in A431 cells compared to EGCG of cleaved caspase 3 (3.0-fold vs. 2.4-fold changes), Nurr1 (2.7-fold vs. 1.7-fold changes) and NFκB (1.3-fold vs. 1.1-fold changes). DIM-D also exhibited chemopreventive activity in UVB-irradiated NHEK cells by significantly (p<0.05) reducing UVB-induced ROS formation and apoptosis compared to EGCG. Additionally, DIM-D induced expression of Nurr1 but reduced expression of 8-OHdG significantly in UVB-irradiated NHEK cells compared to EGCG and UV only.Conclusion
Our results suggest that DIM-D exhibits Nurr1-dependent transactivation in the induction of apoptosis in A431 cells and it protects NHEK cells against UVB-induced ROS formation and DNA damage. 相似文献8.
The 2 Mb domain on chromosome 15q11-q13 that carries the imprinted genes involved in Prader-Willi (PWS) and Angelman (AS) syndromes is under the control of an imprinting center comprising two regulatory regions, the PWS-SRO located around the SNRPN promoter and the AS-SRO located 35 kb upstream. Here we describe the results of an analysis of the epigenetic features of these two sequences and their interaction. The AS-SRO is sensitive to DNase I, and packaged with acetylated histone H4 and methylated histone H3(K4) only on the maternal allele, and this imprinted epigenetic structure is maintained in dividing cells despite the absence of clearcut differential DNA methylation. Genetic analysis shows that the maternal AS-SRO is essential for setting up the DNA methylation state and closed chromatin structure of the neighboring PWS-SRO. In contrast, the PWS-SRO has no influence on the epigenetic features of the AS-SRO. These results suggest a stepwise, unidirectional program in which structural imprinting at the AS-SRO brings about allele-specific repression of the maternal PWS-SRO, thereby preventing regional activation of genes on this allele. 相似文献
9.
The eukaryotic genome is divided into well-defined DNA regions that are programmed to replicate at different times during S phase. Active genes are generally associated with early replication, whereas inactive genes replicate late. This expression pattern might be facilitated by the differential restructuring of chromatin at the time of replication in early or late S phase. 相似文献
10.
García-Ríos CI Alvarez-Ruiz M Barraza JE Rivera AM Hasbún CR 《Revista de biología tropical》2007,55(1):171-176
Collections of 11 species of shallow water Polyplacophora from El Salvador were made in July 2002. Previously only five species had been documented in El Salvador: Chaetopleura lurida (Sowerby, 1832); Ischnochiton guatemalensis (Thiele, 1910); Ceratozona angusta (Thiele, 1909); Chiton stokesii (Broderip, 1832) and Acantochitona exquisita (Pilsbry, 1893). Of these, L. guatemalensis and A. exquisita were not collected in this census. Seven other species are reported here for El Salvador for the first time: Lepidochitona beanii (Carpenter, 1857); Ischnochiton dispar (Sowerby, 1832); Stenoplax limaciformis (Sowerby, 1832); Callistochiton expressus (Carpenter, 1865); Acanthochitona arragonites (Carpenter, 1867); A. ferreirai (Lyons, 1988) and A. hirudiniformis (Sowerby, 1832). The known geographic distribution of 1. dispar is extended to the north. An un-named species of Lepidochitona is briefly described. 相似文献