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41.
J.-J. Vasseur B. Rayner J.-L. Imbach S. Verla J. A. McCloskey J. W. Lown 《Nucleosides, nucleotides & nucleic acids》2013,32(1-2):467-468
Abstract The mechanism of breakage of apurinic DNA with 3-aminocarbazole was determinated on a short oligonucleotide model. The results founded contrast with those reported in the literature.1 相似文献
42.
Role of the three consecutive G:C base pairs conserved in the anticodon stem of initiator tRNAs in initiation of protein synthesis in Escherichia coli. 总被引:2,自引:1,他引:1 下载免费PDF全文
N Mandal D Mangroo J J Dalluge J A McCloskey U L Rajbhandary 《RNA (New York, N.Y.)》1996,2(5):473-482
The three consecutive G:C base pairs, G29:C41, G30:C40, and G31:C39, are conserved in the anticodon stem of virtually all initiator tRNAs from eubacteria, eukaryotes, and archaebacteria. We show that these G:C base pairs are important for function of the tRNA in initiation of protein synthesis in vivo. We changed these base pairs individually and in combinations and analyzed the activities of the mutant Escherichia coli initiator tRNAs in initiation in vivo. For assessment of activity of the mutant tRNAs in vivo, mutations in the G:C base pairs were coupled to mutation in the anticodon sequence from CAU to CUA. Mutations in each of the G:C base pairs reduced activity of the mutant tRNA in initiation, with mutation in the second G:C base pair having the most severe effect. The greatly reduced activity of this C30:G40 mutant tRNA is not due to defects in aminoacylation or formulation of the tRNA or defects in base modification of the A37, next to the anticodon, which we had previously shown to be important for activity of the mutant tRNAs in initiation. The anticodon stem mutants are most likely affected specifically at the step of binding to the ribosomal P site. The pattern of cleavages in the anticodon loop of mutant tRNAs by S1 nuclease indicate that the G:C base pairs may be involved directly in interactions of the tRNA with components of the P site on the ribosome rather than indirectly by inducing a particular conformation of the anticodon loop critical for function of the tRNA in initiation. 相似文献
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T S Ro-Choi Y C Choi D Henning J McCloskey H Busch 《The Journal of biological chemistry》1975,250(10):3921-3928
The nucleotide sequences were determined for the 5'-oligonucleotides obtained by complete pancreatic RNase digestion (P25) and complete T1 RNase digestion (T27) of U-2 RNA. Complete digestion of oligonucleotide P25 with snake venom phosphodiesterase produced pm3 2,2,7G, pAm, pUm, and pCp in approximately equimolar ratios. Partial digestion of these oligonucleotides with snake venom phosphodiesterase produced -Um-C-Gp and pAm-Um, indicating the sequence of the 3'-terminal portion of the 5'-oligonucleotide is pAm-Um-C-Gp. The 5'-terminal oligonucleotide did not contain a 5'-phosphate and no free nucleoside was released from the 5' end by venom phosphodiesterase digestion. Since free pm3 2,2,7G was released by digestion with nucleotide pyrophosphatase and limited digestion with snake venom phosphodiesterase, this nucleotide is apparently linked to pAm in a pyrophosphate linkage. Mass spectrometry and thin layer chromatography in borate systems showed the ribose of m3 2, 2, 7G contains no 2'O-methyl residue. Moreover, the finding that the ribose of m3 2, 2, 7G was oxidized by NaIO4 and reduced by KB3H4 in intact U-2 RNA rules out other linkages involving the 2' and 3' positions. Accordingly, it is concluded that the structure of the 5'-terminal pentanucleotide of U-2 RNA is(see article). 相似文献
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George E. Milo Richard G. Olsen Steven E. Weisbrode John A. McCloskey 《In vitro cellular & developmental biology. Plant》1980,16(9):813-822
Summary Human diploid cells morphologically transformed by feline sarcoma virus were serially propagated under selective cell culture
conditions. When injected into nude mice prior to passage in soft agar (0.35%), morphologically transformed cells did not
produce tumors. However, when propagated under selective cell culture conditions, transformed cells grew in soft agar and,
when injected subcutaneously into the subcapsular region of the nμ/nμ mice, produced neoplastic nodules histopathologically
interpreted as fibromas. Karyological examination of cell populations grown out from the tumors confirmed that the tumors
were composed of human cells. Examination of electron micrographs of the excised tumor tissue revealed the presence of budding
virus particles. Tumor cells isolated from nude mice and morphologicaly transformed cells both contained the feline concornativirus-associated
cell membrane antigen. It was concluded that expression of feline oncornavirus-associated cell membrane antigen is associated
with an early stage of feline rerovirus-induced carcinogenesis, namely focus formation. In addition, it was shown that FeLV-FeSV
can induce morphological transformation in human cells in vitro and that there is a requirement for the cells to passage through
soft agar before subsequent tumor formation (neoplastic transformation) can be demonstrated.
This work was supported in part by NIH-NCI RO1-259007, NO1-CP-3571 and CPV08 103563, and Air Force F49620-77-C-110. 相似文献
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Bondurant RH Revah I Franti C Harman RJ Hird D Klingborg D McCloskey M Weaver L Wilgenberg B 《Theriogenology》1991,35(2):365-374
To assess the potential benefit to fertility from gonadotropin-releasing hormone (GnRH) administration to third service cows managed in typical California dairy systems, 963 cows were enlisted from 14 dairies served by 6 veterinary practices. The cows were randomly assigned to receive either GnRH (100 mug) or placebo at the time of the third artificial insemination. Fertility data were entered onto a proprietary microcomputer program common to all six practices, and collated independently by a third party. For the duration of the trial (1 yr), GnRH and placebo-treated cows had 43.2 and 39.3% conception rates, respectively (P=0.35). When treatments administered in summer months (July, August, September) were excluded, conception rates were 48.1 and 41.0%, respectively (P<0.1). The conception rates of cows treated with GnRH in August tended to be lower than those of placebo-treated cows (95% logarithmic confidence intervals of odds ratio = -1.139, 0.377). Between-herd variation in benefit from GnRH was evident, with two dairies showing no benefit, one dairy showing a negative effect, and four showing a range of effects from lightly beneficial to significantly beneficial. First-lactation cows did not benefit at any time from GnRH treatment. The data suggest that GnRH administered to third-service dairy cows under California conditions may result in increased conception rates in non-summer months, but that other unidentified variables may have important influence on the outcome of such treatment. 相似文献
50.
V(D)J recombination: evidence that a replicative mechanism is not required. 总被引:3,自引:1,他引:2 下载免费PDF全文
We examined a series of extrachromosomal DNA substrates for V(D)J recombination under replicating and nonreplicating conditions. Complete and partial replications were examined by monitoring the loss of prokaryote-specific adenine methylation at 14 to 22 MboI-DpnI restriction sites (GATC) on the substrates. Some of these sites are within 2 bases of the signal sequence ends. We found that neither coding joint nor signal joint formation requires substrate replication. After ruling out replication as a substrate requirement, we determined whether replication had any effect on the efficiency of V(D)J recombination. Quantitation of V(D)J recombination efficiency on nonreplicating substrates requires some method of monitoring the entry of substrate molecules into the cells. We devised such a method by monitoring DNA repair of substrates into which we had substituted deoxyuridine for 10 to 20% of the thymidine nucleotides in the DNA. The substrates which enter the lymphoid cells were repaired efficiently in vivo by the eukaryotic uracil DNA repair system. Upon plasmid harvest, we distinguished repaired (entered) from unrepaired (not entered) plasmids by cleaving unrepaired molecules with uracil DNA glycoylase and Escherichia coli endonuclease IV in vitro. This method of monitoring DNA entry does not appear to underestimate or overestimate the amount of DNA entry. By using this method, we found no significant quantitative effect of DNA replication on V(D)J recombination efficiency. 相似文献