全文获取类型
收费全文 | 436篇 |
免费 | 11篇 |
国内免费 | 13篇 |
出版年
2023年 | 3篇 |
2021年 | 4篇 |
2019年 | 13篇 |
2018年 | 13篇 |
2017年 | 6篇 |
2016年 | 1篇 |
2015年 | 6篇 |
2014年 | 25篇 |
2013年 | 15篇 |
2012年 | 23篇 |
2011年 | 17篇 |
2010年 | 28篇 |
2009年 | 18篇 |
2008年 | 14篇 |
2007年 | 16篇 |
2006年 | 21篇 |
2005年 | 18篇 |
2004年 | 12篇 |
2003年 | 14篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 12篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 8篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1988年 | 7篇 |
1986年 | 2篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 14篇 |
1981年 | 7篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有460条查询结果,搜索用时 15 毫秒
1.
I. L. Sun W. Toole-Simms F. L. Crane D. J. Morré H. Löw J. Y. Chou 《Journal of bioenergetics and biomembranes》1988,20(3):383-391
Retinoic acid inhibits the reduction of diferric transferrin through the transplasma membrane electron transport system on fetal rat liver cells infected with a temperature-sensitive SV40 virus when the cells are in the nontransformed state cultured at 40°C. When the cells are in the transformed state (grown at the permissive 33°C temperature), retinoic acid does not inhibit the diferric transferrin reduction. Inhibition of activity of nontransformed cells is specific for retinoic acid with only slight inhibition by retinol and retinyl acetate at higher concentrations. Isolated rat liver plasma membrane NADH diferric transferrin reductase is also inhibited by retinoic acid. The effect of transformation with SV40 virus to decrease susceptibility to retinoic acid inhibition stands in contrast to much greater adriamycin inhibition of diferric transferrin reduction in the transformed cells than in nontransformed cells. 相似文献
2.
Peter Alliger Wolfgang Traut Eric Carstens Ellen Fanning 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1988,951(2-3)
A monkey cell factor that interacts specifically with double- and single-stranded DNA sequences in the early domain of the simian virus 40 (SV40) core origin of replication was identified using gel-retention assays. The protein was enriched over 1200-fold using ion-exchange and affinity chromatography on single-strand DNA cellulose. Binding of protein to mutant origin DNA restriction fragments was correlated with replication activity of the mutant DNAs. Exonuclease footprint experiments on single-stranded DNA revealed prominent pause sites in the early domain of the core origin. The results suggest that this cellular protein may be involved in SV40 DNA replication. 相似文献
3.
Peter Zahradka 《Molecular and cellular biochemistry》1992,110(1):65-73
Summary The role of DNA polymerases in the replication of SV40 DNA was studied using a T-antigen-dependent assay supplemented with
a human KB cell extract. Inhibition of DNA polymerase α by addition of aphidicolin or monoclonal antibodies prevented DNA
synthesis, confirming the requirement for this enzyme in replication. The replication process was unaffected by ddTTP at a
concentration (5 μM) inhibitory to DNA polymerases β and γ, however, higher concentrations of ddTTP (200 μM) caused an apparent
accumulation of relaxed circular plasmid with a concomitant decrease in DNA synthesis. An analysis of this replication intermediate
indicated that it was formed during the replication reaction and that the replicative cycle was nearly complete. A kinetic
study of ddTTP inhibition strongly suggested DNA polymerase ε (PCNA-independent DNA polymerase δ) was the target of the inhibitor
and that this enzyme functions during the final stages of DNA replication. 相似文献
4.
Targeting of T7 RNA polymerase to tobacco nuclei mediated by an SV40 nuclear location signal 总被引:9,自引:0,他引:9
Michael W. Lassner Aubrey Jones Steve Daubert Luca Comai 《Plant molecular biology》1991,17(2):229-234
We have expressed two T7 RNA polymerase genes by electroporation into tobacco protoplasts. One of the genes was modified by inserting nucleotides encoding a viral nuclear localization signal (NLS) from the large T antigen of SV40. Both T7 RNA polymerase genes directed synthesis of a ca. 100 kDa protein in the electroporated protoplasts. T7 RNA polymerase activity was detected in extracts of protoplasts electroporated with both genes. Immunofluorescence analysis of these protoplasts indicated that only the polymerase carrying the NLS accumulated in the cell nucleus. These experiments suggest that mechanisms involved in the transport from the cytoplasm to the nucleus are similar in plant and animal cells. This system demonstrates the feasibility of T7 RNA polymerase-based approaches for the high-level expression of introduced genes in plant cells. 相似文献
5.
B Schwartz P Vicart C Delouis D Paulin 《Biology of the cell / under the auspices of the European Cell Biology Organization》1991,73(1):7-14
The aim of this study was to investigate a new method to enhance the efficiency to create mammalian cell lines. Cell immortalization was achieved by intranuclear microinjection of a recombinant DNA construct composed of a constitutive promoter controlling the genes encoding immortalizing proteins; the sequences coding for the large T and small t antigens were fused downstream of regulatory elements from the vimentin gene, the activation of which characterizes the vast majority of cells growing in vitro. Data show that the efficiency of the immortalizing procedures using the SV40 early genes could be enhanced by the control elements derived from the human vimentin (HuVim) 5' sequences that contained nucleotides -878 to +93 from the CAP site. This HuVim 830-T/t recombinant was used to create cell lines from numerous primary cultures of different origins: rabbit, porcine and human endothelial cells, rabbit and bovine epithelial cells. A set of large T-expressing cells was derived, and these cells retained characteristics of differential cells: binding of Ulex europaeus lectin and synthesis of Factor VIII for human endothelial cells; network of cytokeratin for bovine oviductal cells and rabbit mammary cells. 相似文献
6.
Restriction endonuclease EcoO109 from Escherichia coli H709c with heptanucleotide recognition site 5'-PuG/GNCCPy 总被引:1,自引:0,他引:1
A new restriction endonuclease, EcoO109, has been isolated from Escherichia coli H709c by polyethyleneimine (PEI) precipitation, DEAE-cellulose chromatography and heparin agarose chromatography. The yield was high, more than 3000 units/g of wet cells. The EcoO109 endonuclease recognizes and cleaves a nucleotide sequence of (formula: see text), in the presence of 10 mM Mg2+. The enzyme will be useful for structural analysis and molecular cloning of DNA because of the stability, high yield and easy handling of the producer strain. 相似文献
7.
Foreign protein expression from the commonly used SV40 promoter has been found to be primarily during the S-phase of the cell cycle. Simple mathematical models with this cell cycle phase dependent expression of foreign protein suggest that the specific production rate will be proportional to the cell growth rate, which is particularly disadvantageous in high cell density fed-batch or perfusion bioreactors. In this study we investigate this predicted relationship between the production rate and growth rate by culturing recombinant CHO cells in a continuous suspension bioreactor. One CHO cell line, GS-26, has been stably transfected with the plasmid pSVgal, which contains the E. coli lac Z gene under the control of the SV40 promoter. This GS-26 cell line was grown in suspension cultures over a range of specific growth rates in batch and continuous modes. The intracellular -galactosidase activity was assayed using a standard spectrophotometric method after breaking the cells open and releasing the enzyme. A strong growth associated relationship is found between the intracellular -galactosidase content and the specific growth rate in batch and continuous cultures, as predicted. 相似文献
8.
利福霉素生产菌产生钝化RifSV物质的分离及性质研究 总被引:1,自引:0,他引:1
利福霉素SV(简称RifSV)生产菌──地中海拟无枝菌酸菌在生物合成RifSV过程中,产生一种能钝化自身产物(RifSV)的物质.实验证实,该物质是由谷氨酸、天冬氨酸、赖氨酸及缬氨酸等14种常见氨基酸组成的蛋白质.分子量(MW)约2.5×104D,等电点(PI)为5.7—6.1.在100℃下加热10min,其活性丧失.作用于RifSV的最适pH值范围为7.4—8.6,最适温度为29℃,初步证实该物质是一种酶(暂称利福霉素钝化酶) 相似文献
9.
John M. Lehman Emilee Dickerson Thomas Friedrich Judith Laffin 《In vitro cellular & developmental biology. Animal》1995,31(10):806-810
Summary The changes in cell size and total protein were determined for G1-arrested, contact-inhibited CV-1 cells infected with Simian
virus 40 (SV40). The assays used were the Biorad total protein assays (Bradford and DC protein assays) on a standard number
of cells, total protein as assayed by fluorescein isothiocyanate (FITC) and SR101 by flow cytometry, orthoganol (90°) light
scatter by flow cytometry, and direct microscopic measurement with an ocular micrometer. Uninfected CV-1 cells and two cell
lines with variations in DNA content (diploid vs. tetraploid) were used as controls for the studies presented. The results
demonstrated a 40–60% increase in total protein at 32 to 42 h postinfection. These increases were similar to values obtained
as control cells progress through the cell cycle. At later times postinfection (>42 h), total protein decreased due to cellular
changes resulting from viral replication and cell death. 相似文献
10.
Ali Arslan Cuillermina Almazan Hans H. Zingg 《In vitro cellular & developmental biology. Animal》1995,31(2):140-148
Summary Normal and neoplastic growth of epithelial cells depends on mutual interactions between epithelial and stromal cells. As a
tool for the study of the underlying molecular mechanisms, we have developed temperature-sensitive, nontransformed cell lines
derived from rat uterine epithelium and stroma by transfecting primary cultures with a temperature-sensitive mutant of the
SV40 large T antigen. The epithelial and stromal cell lines obtained shared relevant morphological characteristics with the
primary cells from which they were derived. Immunocytochemical analysis showed that the epithelial cell lines expressed the
intermediate filament cytokeratin, whereas the stromal lines expressed the intermediate filament vimentin. Alkaline phosphatase
activity was present in all cell lines examined. All cell lines were anchorage dependent and did not form foci. One epithelial
cell line expressed oxytocin mRNA, a gene product recently shown to be highly expressed in vivo in the uterine epithelium
at term. If grown on Matrigel, this cell line formed domelike structures, a further characteristic of its differentiated phenotype.
In an attempt to reconstitute an endometrium in vitro, epithelial cells were seeded on top of a layer of stromal cells. Paraffin
cross sections showed that this in vitro system consisted of a bilayer structure. Four to five cuboidal epithelial cells were
typically anchored atop one stromal cell, forming an endometriumlike tissue. The present in vitro system should provide a
useful model for further studies on endometrial functions and epithelial/stromal cell interactions at a molecular level. 相似文献