全文获取类型
收费全文 | 311篇 |
免费 | 38篇 |
专业分类
349篇 |
出版年
2021年 | 9篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 15篇 |
2015年 | 5篇 |
2014年 | 22篇 |
2013年 | 14篇 |
2012年 | 19篇 |
2011年 | 26篇 |
2010年 | 15篇 |
2009年 | 11篇 |
2008年 | 11篇 |
2007年 | 15篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 15篇 |
2003年 | 16篇 |
2002年 | 21篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1960年 | 1篇 |
1954年 | 1篇 |
1951年 | 1篇 |
1935年 | 1篇 |
1931年 | 1篇 |
排序方式: 共有349条查询结果,搜索用时 15 毫秒
1.
Several unit-length minicircles from the kinetoplast DNA of Leishmania tarentolae were cloned into pBR322 and into M13 phage vectors. The complete nucleotide sequences of three different partially homologous minicircles were obtained. The molecules contained a region of approx. 80% sequence homology extending for 160–270 bp and a region unique to each minicircle. A 14-mer was found to be conserved in all kinetoplast minicircle sequences reported to date. The frequency distributions of various minicircle sequence classes in L. tarentolae were obtained by quantitative gel electrophoresis and by examination of the “T ladder” patterns of minicircles randomly cloned into M13 at several sites. By these methods we could assign approx. 50% of the total minicircle DNA into a minimum of five sequence classes. A sequence-dependent polyacrylamide gel migration abnormality was observed with several minicircle fragments both cloned and uncloned. The abnormality was dependent on the presence of a portion of the conserved region of the minicircle. 相似文献
2.
3.
In vitro attachment of bilins to apophycocyanin. III. Properties of the phycoerythrobilin adduct 总被引:3,自引:0,他引:3
Addition of phycoerythrobilin (PEB) to apophycocyanin at pH 7.0 resulted in covalent adduct formation. The adduct showed absorbance maxima at 575 and 605 nm and fluorescence emission maxima at 582 and 619 nm. Analysis of bilin peptides obtained upon tryptic digestion of the adduct showed residues alpha-Cys-84 and beta-Cys-82 to be the sites of bilin addition. The product of PEB addition at the alpha-Cys-84 site was shown by 1H NMR analysis to be a dihydrobiliviolinoid peptide-linked pigment differing in structure from that of the naturally occurring PEB-adduct by the presence of a double bond in between C2 and C3 of ring A. At the beta-Cys-82 site both a dihydrobiliviolinoid and a PEB adduct were obtained. Biliverdin also formed a covalent adduct with apophycocyanin with a lambda max of 669 nm. These results show that the spontaneous in vitro addition of bilins to apophycocyanin does not exhibit the site selectivity of bilin addition observed in vivo. This offers the opportunity to form novel semisynthetic phycobiliproteins. 相似文献
4.
Estimation of microsatellite mutation rates in recombinant inbred strains of mouse 总被引:15,自引:0,他引:15
John F. Dallas 《Mammalian genome》1992,3(8):452-456
5.
Cloning, sequence analysis, and overexpression of Escherichia coli folK, the gene coding for 7,8-dihydro-6-hydroxymethylpterin-pyrophosphokinase. 下载免费PDF全文
The gene coding for the Escherichia coli enzyme 7,8-dihydro-6-hydroxymethylpterin-pyrophosphokinase has been cloned and sequenced. This gene, designated folK, codes for a protein of 159 amino acids, including an amino-terminal methionine. The protein was overexpressed in E. coli MC4100 by cloning the gene behind the lacUV5 promoter in a high-copy-number plasmid. The enzyme was purified to homogeneity. Amino-terminal analysis of the purified protein showed that the amino-terminal methionine had been removed. The compositional molecular mass (17,945 Da) was identical to the molecular mass determined by mass spectrometry. The enzyme was observed to have a large number of proline residues and migrated anomalously in sodium dodecyl sulfate-polyacrylamide gels, with an apparent molecular mass of 23,000 Da. 相似文献
6.
The value of genome-specific repetitive DNA sequences for use as molecular markers in studying genome differentiation was investigated. Five repetitive DNA sequences from wild species of rice were cloned. Four of the clones, pOm1, pOm4, pOmA536, and pOmPB10, were isolated from Oryza minuta accession 101141 (BBCC genomes), and one clone, pOa237, was isolated from Oryza australiensis accession 100882 (EE genome). Southern blot hybridization to different rice genomes showed strong hybridization of all five clones to O. minuta genomic DNA and no cross hybridization to genomic DNA from Oryza sativa (AA genome). The pOm1 and pOmA536 sequences showed cross hybridization only to all of the wild rice species containing the C genome. However, the pOm4, pOmPB10, and pOa237 sequences showed cross hybridization to O. australiensis genomic DNA in addition to showing hybridization to the O. minuta genomic DNA. 相似文献
7.
Michael G. Clark Sally D. Neville Dallas G. Clark 《Biochemical and biophysical research communications》1981,103(2):690-697
Hepatocytes were prepared from a strain of rats deficient in hepatic phosphorylase kinase and were used to assess the role of this enzyme in the adrenergic regulation of pyruvate kinase and gluconeogenesis. Epinephrine (10 μM) stimulated glucose output and gluconeogenesis from 1.8 mM lactate but did not significantly affect the concentration of hepatocyte glycogen. In addition epinephrine treatment led to an inhibition of pyruvate kinase. The stimulation of gluconeogenesis and the inhibition of pyruvate kinase by epinephrine were blocked by both α- and β-antagonists: similar effects with epinephrine were observed in cells from control animals. It is concluded that mechanisms for the adrenergic regulation of pyruvate kinase and gluconeogenesis are similar in hepatocytes from both phosphorylase kinase-deficient and normal rats. 相似文献
8.
Adenosine 3′,5′-cyclic monophosphate (cAMP) has been shown to be involved in regulating a number of membrane functions in Escherichia coli cells, including various respiratory and transport activities. In this report we show that this regulation is mediated by the cAMP receptor protein (CRP). In addition, data are presented which show that the cAMP-CRP system is involved in regulating the E. coli fatty acid composition. 相似文献
9.
Gold salts and phenylbutazone selectively inhibit the synthesis of PGF2α and PGE2 respectively. Lowered production of one prostaglandin species is accompanied by an increased production of the other. Selective inhibition by these drugs was observed in the presence of adrenaline, reduced glutathione and copper sulphate under conditions when most anti-inflammatory compounds inhibited PGE2 and PGF2α syntheses equally. It is postulated that selective inhibitors may have a different mode of action
and beneficial effects may be related to the endogenous ratio of PGE to PGF required for normal function. 相似文献
10.