全文获取类型
收费全文 | 297篇 |
免费 | 17篇 |
出版年
2023年 | 2篇 |
2021年 | 6篇 |
2020年 | 2篇 |
2019年 | 8篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 10篇 |
2014年 | 11篇 |
2013年 | 11篇 |
2012年 | 18篇 |
2011年 | 19篇 |
2010年 | 15篇 |
2009年 | 10篇 |
2008年 | 13篇 |
2007年 | 17篇 |
2006年 | 19篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 16篇 |
2002年 | 10篇 |
2001年 | 6篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1971年 | 4篇 |
1966年 | 2篇 |
1965年 | 5篇 |
1964年 | 3篇 |
1963年 | 3篇 |
1962年 | 3篇 |
1961年 | 2篇 |
1960年 | 4篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1954年 | 1篇 |
1953年 | 1篇 |
排序方式: 共有314条查询结果,搜索用时 734 毫秒
11.
Keith L. Constantine Mark S. Friedrichs David Detlefsen Maki Nishio Mitsuaki Tsunakawa Tamotsu Furumai Hiroaki Ohkuma Toshikazu Oki Susan Hill Robert E. Bruccoleri Pin-Fang Lin Luciano Mueller 《Journal of biomolecular NMR》1995,5(3):271-286
Summary The 21-amino acid peptides siamycin II (BMY-29303) and siamycin I (BMY-29304), derived from Streptomyces strains AA3891 and AA6532, respectively, have been found to inhibit HIV-1 fusion and viral replication in cell culture. The primary sequence of siamycin II is CLGIGSCNDFAGCGYAIVCFW. Siamycin I differs by only one amino acid; it has a valine residue at position 4. In both peptides, disulfide bonds link Cys1 with Cys13 and Cys7 with Cys19, and the side chain of Asp9 forms an amide bond with the N-terminus. Siamycin II, when dissolved in a 50:50 mixture of DMSO and H2O, yields NOESY spectra with exceptional numbers of cross peaks for a peptide of this size. We have used 335 NOE distance constraints and 13 dihedral angle constraints to generate an ensemble of 30 siamycin II structures; these have average backbone atom and all heavy atom rmsd values to the mean coordinates of 0.24 and 0.52 Å, respectively. The peptide displays an unusual wedge-shaped structure, with one face being predominantly hydrophobic and the other being predominantly hydrophilic. Chemical shift and NOE data show that the siamycin I structure is essentially identical to siamycin II. These peptides may act by preventing oligomerization of the HIV transmembrane glycoprotein gp41, or by interfering with interactions between gp41 and the envelope glycoprotein gp120, the cell membrane or membrane-bound proteins [Frèchet, D. et al. (1994) Biochemistry, 33, 42–50]. The amphipathic nature of siamycin II and siamycin I suggests that a polar (or apolar) site on the target protein may be masked by the apolar (or polar) face of the peptide upon peptide/protein complexation.Abbreviations ABNR
adopted basis Newton Raphson
- AIDS
acquired immunodeficiency syndrome
- CW
continuous wave
- DMSO
dimethylsulfoxide
- DQF-COSY
two-dimensional double-quantum-filtered correlation spectroscopy
- HIV
human immunodeficiency virus
- HSQC
heteronuclear single-quantum coherence
- NOE
nuclear Overhauser enhancement
- NOESY
two-dimensional nuclear Overhauser enhancement spectroscopy
- ppm
parts per million
- P.E.-COSY
two-dimensional primitive exclusive correlation spectroscopy
- REDAC
redundant dihedral angle constraint
- rf
radio frequency
- rmsd
root-mean-square difference
- SIV
simian immunodeficiency virus
- sw
spectral width
- m
mixing time
- TOCSY
two-dimensional total correlation spectroscopy
- TSP
trimethylsilyl-2,2,3,3-2H4-propionate
- 2D
two-dimensional 相似文献
12.
W. J. Metzler B. T. Farmer nd K. L. Constantine M. S. Friedrichs T. Lavoie L. Mueller 《Protein science : a publication of the Protein Society》1995,4(3):450-459
Profilin is a ubiquitous eukaryotic protein that binds to both cytosolic actin and the phospholipid phosphatidylinositol-4,5-bisphosphate. These dual competitive binding capabilities of profilin suggest that profilin serves as a link between the phosphatidyl inositol cycle and actin polymerization, and thus profilin may be an essential component in the signaling pathway leading to cytoskeletal rearrangement. The refined three-dimensional solution structure of human profilin I has been determined using multidimensional heteronuclear NMR spectroscopy. Twenty structures were selected to represent the solution conformational ensemble. This ensemble of structures has root-mean-square distance deviations from the mean structure of 0.58 A for the backbone atoms and 0.98 A for all non-hydrogen atoms. Comparison of the solution structure of human profilin to the crystal structure of bovine profilin reveals that, although profilin adopts essentially identical conformations in both states, the solution structure is more compact than the crystal structure. Interestingly, the regions that show the most structural diversity are located at or near the actin-binding site of profilin. We suggest that structural differences are reflective of dynamical properties of profilin that facilitate favorable interactions with actin. The global folding pattern of human profilin also closely resembles that of Acanthamoeba profilin I, reflective of the 22% sequence identity and approximately 45% sequence similarity between these two proteins. 相似文献
13.
Genetic Structure and Internal Rearrangements of Stable Merodiploids from BACILLUS SUBTILIS Strains Carrying the trpE26 Mutation 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《Genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Transformation and transduction to tryptophan independence of strains of Bacillus subtilis carrying the "trpE26" chromosomal aberrations (a translocation and an inversion) with a "normal" 168 type strain as donor induce a tandem duplication of the thrA-ilvA region of the chromosome. The clones possessing this unstable duplication segregate besides the Trp- some stable Trp+ cells which retain only part of the duplication (the trpE-ilvA region) in nontandem configuration. Such clones may also be produced directly during the crosses. The genetic map of these clones (designated as class I stable merodiploids) was constructed: they possess the tranlocation and the inversion of the trpE26 parental strain. Another type of stable Trp+ clones (class II) also appears, although more rarely, in similar crosses. Studies on their genetic structure revealed that they are haploid for the trpE-ilvA region and carry a nontandem duplication of the thrA-trpE region. In these clones the cysB-tre region has the orientation of the 168 type strain. The duplications in both classes are stable, that of class I being more stable than that of class II where loss of one copy of the thrA-trpE region leads to about 1% haploid cells. Detailed genetic studies on heterozygous clones from both classes have shown exchange of alleles between copies of the nontandem duplications. Models are proposed for the formation of each class of merodiploids and for recombination events taking place in them. These models imply recombination at sequences of intrachromosomal homology and (or) introduction of heterologous juncions ("novel joints") by transformation or transduction. 相似文献
14.
The activity of the plasma membrane enzyme 5′-nucleotidase varies dramatically during the embryonic development of chick pectoral muscle. The specific activity is greatest at early stages of differentiation (8-day embryos), falls to a minimum on days 12–14, then rises again in older embryos. In cultured muscle cells obtained from embryonic chick muscle the 5′-nucleotidase activity is essentially absent. Muscle cells grown in the presence of bromodeoxyuridine, an inhibitor of muscle differentiation, contain enhanced levels of 5′-nucleotidase activity. These results indicate that 5′-nucleotidase may be absent in muscle fibers, but present in other cells of muscle tissue. 相似文献
15.
Hydroxyproline-2-epimerase was treated with 14C-iodoacetate under conditions that produced almost complete inactivation of the enzyme and concomitant incorporation of almost one molar equivalent of iodoacetate. Both processes were prevented by saturating concentrations of substrate. From reaction mixtures in which both incorporation and inactivation were 85 to 90% complete, two radioactive tryptic peptides were isolated by paper chromatography-electrophoresis. The incorporated radioactivity was divided between the peptides in an approximately 2:1 ratio. Analysis of the isolated peptides suggested that they both contained 9 amino acids and had similar composition; one appeared to be a lysine, the second an arginine peptide. Attempts to sequence each peptide failed, apparently because of the conversion of the S-carboxymethylcysteine to S-carboxymethylcysteine sulfone, indicating that the cysteine residue was N-terminal in each peptide. 相似文献
16.
17.
Boutas Ioannis Kontogeorgi Adamantia Dimitrakakis Constantine Kalantaridou Sophia N. 《Molecular biology reports》2021,48(7):5699-5705
Molecular Biology Reports - Galectin-3 is part of a protein group called lectins and acts as a multifunctional glycoprotein due to its expression location. Galectin-3 is expressed by different... 相似文献
18.
Timothy A. McCaffrey Constantine Tziros Jannet Lewis Richard Katz Robert Siegel William Weglicki Jay Kramer I. Tong Mak Ian Toma Liang Chen Elizabeth Benas Alexander Lowitt Shruti Rao Linda Witkin Yi Lian Yinglei Lai Zhaoqing Yang Sidney W. Fu 《International journal of biological sciences》2013,9(4):350-360
19.
Introduction
Secondhand smoke (SHS) exposure causes disease and death among nonsmokers. With a plethora of smoke-free legislation implemented and a steady decrease in cigarette consumption noted over the past decade in the U.S., this study assessed trends in indoor SHS exposure among U.S. adolescents in grades 6–12 during 2000–2009.Methods
Data were obtained from the 2000–2009 National Youth Tobacco Survey – a national survey of U.S. middle and high school students. SHS exposure within an indoor area within the past seven days was self-reported. Trends in indoor SHS exposure during 2000–2009 were assessed overall and by socio-demographic characteristics, using the Wald''s test in a binary logistic regression. Within-group comparisons were performed using chi-squared statistics (p<0.05).Results
The proportion of U.S. middle and high school students who were exposed to indoor SHS declined from 65.5% in 2000 to 40.5% in 2009 (p<0.05 for linear trend). Significant declines were also observed across all population subgroups. Between 2000 and 2009, prevalence of indoor SHS exposure declined significantly among both middle (58.5% to 34.3%) and high school (71.5% to 45.4%) students. Prevalence of indoor SHS exposure was significantly higher among girls (44.0% in 2009) compared to boys (37.2% in 2009) during each survey year. Similarly, prevalence of indoor SHS exposure during 2000–2009 was highest among non-Hispanic whites (44.2% in 2009) and lowest among non-Hispanic Asians (30.2% in 2009). During each survey year, prevalence was highest among the oldest age group (≥18 years) and lowest among the youngest (9–11 years). Also, prevalence was significantly higher among current cigarette smokers (83.8% in 2009) compared to nonsmokers (34.0% in 2009).Conclusion
Significant declines in indoor SHS exposure among U.S. middle and high school students occurred during 2000–2009. While the results are encouraging, additional efforts are needed to further reduce youth indoor SHS exposure. 相似文献20.
Flora Zagouri Theodoros N. Sergentanis Maria Gazouli Constantine Dimitrakakis Alexandra Tsigginou Irene Papaspyrou Dimosthenis Chrysikos Maria Lymperi George C. Zografos Aris Antsaklis Meletios-Athanassios Dimopoulos Christos A. Papadimitriou 《Molecular biology reports》2013,40(8):5035-5040
This case control study aims to investigate the role of MMP-2 ?1306C > T polymorphism as a potential risk factor and possible prognostic marker for breast cancer in a South European population. 113 consecutive incident cases of histologically confirmed ductal breast cancer and 124 healthy controls were recruited. MMP-2 ?1306C > T polymorphism was genotyped; multivariate logistic regression as well as Cox regression analysis were performed. MMP-2 ?1306C > T status was not associated with breast cancer risk either at the total sample or at the subanalyses on premenopausal and postmenopausal women. At the survival analysis, a trend towards a favorable association between MMP-2 ?1306C > T allele and disease-free survival as well as overall survival was observed. Regarding subanalyses on ER-negative and ER-positive cases, the favorable association implicating MMP-2 ?1306C > T allele was particularly evident among ER-positive cases; no significant associations emerged among ER-negative cases. MMP-2 ?1306C > T polymorphism does not seem to be a risk factor for breast cancer in South European population; however, a trend towards a favorable association with survival has been observed. 相似文献