全文获取类型
收费全文 | 366篇 |
免费 | 26篇 |
专业分类
392篇 |
出版年
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 18篇 |
2020年 | 13篇 |
2019年 | 5篇 |
2018年 | 18篇 |
2017年 | 8篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 24篇 |
2012年 | 37篇 |
2011年 | 40篇 |
2010年 | 17篇 |
2009年 | 10篇 |
2008年 | 41篇 |
2007年 | 35篇 |
2006年 | 11篇 |
2005年 | 24篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 2篇 |
2001年 | 4篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有392条查询结果,搜索用时 8 毫秒
41.
Denaturing high-performance liquid chromatography (DHPLC) has been used for rapid and accurate DNA mutation analysis; to extend the DNA fragment lengths analysis. Recently, polymorphism in polyglutamine-coding region of Amplified In Breast cancer gene 1 (AIB1) was analyzed as an independent genetic risk factor influencing breast cancer onset in carriers of mutation in breast cancer predisposing gene 1 (BRCA1). We have implemented efficient, cost-effective and rapid method for analysis of the AIB1 polyglutamine repeat polymorphism based on DHPLC analysis (WAVE system) of unlabeled PCR products. This strategy can be useful for genotyping of other trinucleotide repeat polymorphisms using DHPLC in medium/high throughput settings. 相似文献
42.
Chlorophyll fluorescence is routinely taken as a quantifiable measure of the redox state of the primary quinone acceptor QA of PSII. The variable fluorescence in thylakoids increases in a single turnover flash (STF) from its low dark level F
o towards a maximum F
mSTF when QA becomes reduced. We found, using twin single turnover flashes (TTFs) that the fluorescence increase induced by the first
twin-partner is followed by a 20–30% increase when the second partner is applied within 20–100 μs after the first one. The
amplitude of the twin response shows a period-of-four oscillation associated with the 4-step oxidation of water in the Kok
cycle (S states) and originates from two different trapped states with a life time of 0.2–0.4 and 2–5 ms, respectively. The
oscillation is supplemented with a binary oscillation associated with the two-electron gate mechanism at the PSII acceptor
side. The F(t) response in high frequency flash trains (1–4 kHz) shows (i) in the first 3–4 flashes a transient overshoot 20–30% above
the F
mSTF = 3*F
o level reached in the 1st flash with a partial decline towards a dip D in the next 2–3 ms, independent of the flash frequency,
and (ii) a frequency independent rise to F
m = 5*F
o in the 3–60 ms time range. The initial overshoot is interpreted to be due to electron trapping in the S0 fraction with QB-nonreducing centers and the dip to the subsequent recovery accompanying the reoxidation of the double reduced acceptor pair
in these RCs after trapping. The rise after the overshoot is, in agreement with earlier findings, interpreted to indicate
a photo-electrochemical control of the chlorophyll fluorescence yield of PSII. It is anticipated that the double exciton and
electron trapping property of PSII is advantageous for the plant. It serves to alleviate the depression of electron transport
in single reduced QB-nonreducing RCs, associated with electrochemically coupled proton transport, by an increased electron trapping efficiency
in these centers. 相似文献
43.
Sojka D Hajdusek O Dvorák J Sajid M Franta Z Schneider EL Craik CS Vancová M Buresová V Bogyo M Sexton KB McKerrow JH Caffrey CR Kopácek P 《International journal for parasitology》2007,37(7):713-724
Ticks are ectoparasitic blood-feeders and important vectors for pathogens including arboviruses, rickettsiae, spirochetes and protozoa. As obligate blood-feeders, one possible strategy to retard disease transmission is disruption of the parasite's ability to digest host proteins. However, the constituent peptidases in the parasite gut and their potential interplay in the digestion of the blood meal are poorly understood. We have characterised a novel asparaginyl endopeptidase (legumain) from the hard tick Ixodes ricinus (termed IrAE), which we believe is the first such characterisation of a clan CD family C13 cysteine peptidase (protease) in arthropods. By RT-PCR of different tissues, IrAE mRNA was only expressed in the tick gut. Indirect immunofluorescence and EM localised IrAE in the digestive vesicles of gut cells and within the peritrophic matrix. IrAE was functionally expressed in Pichia pastoris and reacted with a specific peptidyl fluorogenic substrate, and acyloxymethyl ketone and aza-asparagine Michael acceptor inhibitors. IrAE activity was unstable at pH > or = 6.0 and was shown to have a strict specificity for asparagine at P1 using a positional scanning synthetic combinatorial library. The enzyme hydrolyzed protein substrates with a pH optimum of 4.5, consistent with the pH of gut cell digestive vesicles. Thus, IrAE cleaved the major protein of the blood meal, hemoglobin, to a predominant peptide of 4kDa. Also, IrAE trans-processed and activated the zymogen form of Schistosoma mansoni cathepsin B1 -- an enzyme contributing to hemoglobin digestion in the gut of that bloodfluke. The possible functions of IrAE in the gut digestive processes of I. ricinus are compared with those suggested for other hematophagous parasites. 相似文献
44.
45.
46.
Petrlová J Blastík O Průsa R Kukacka J Potĕsil D Mikelová R Adam V Zehnálek J Kizek R 《Biomedical papers of the Medical Faculty of the University Palacky, Olomouc, Czechoslovakia》2005,149(2):485-488
Metallothioneins belong to the group of intracellular, high molecular and cysteine-rich proteins whose content increase with increasing concentration of a heavy metal. Here we applied the adsorptive transfer stripping differential pulse voltammetry Brdicka reaction for the determination of metallothionein in human blood serum of patient poisoned by lead and/or treated by platinum. The increased metallothionein concentrations in both cases were observed. 相似文献
47.
48.
Zvarec O Polyak SW Tieu W Kuan K Dai H Pedersen DS Morona R Zhang L Booker GW Abell AD 《Bioorganic & medicinal chemistry letters》2012,22(8):2720-2722
Herein we outline the antibacterial activity of amino acid containing thiazolidinediones and rhodanines against Gram-positive bacteria Staphylococcus aureus ATCC 31890, Staphylococcus epidermidis and Bacillus subtilis ATCC 6633. The rhodanine derivatives were generally more active than the analogous thiazolidinediones. Compounds of series 5 showed some selectivity for Bacillus subtilis ATCC 6633, the extent of which is enhanced by the inclusion of a non-polar amino acid at the 5-position of the core thiazolidinediones and rhodanines scaffolds. SAR data of series 8 demonstrated improved activity against the clinically more significant Staphylococci with selectivity over Bacillus subtilis ATCC 6633 induced by introduction of a bulky aryl substituent at the 5-position of the core scaffolds. 相似文献
49.
50.
Est1 and Ebs1 in Saccharomyces cerevisiae are paralogous proteins that arose through whole-genome duplication and that serve distinct functions in telomere maintenance and translational regulation. Here we present our functional analysis of the sole Est1/Ebs1 homologue in the related budding yeast Kluyveromyces lactis (named KlEst1). We show that similar to other Est1s, KlEst1 is required for normal telomere maintenance in vivo and full telomerase primer extension activity in vitro. KlEst1 also associates with telomerase RNA (Ter1) and an active telomerase complex in cell extracts. Both the telomere maintenance and the Ter1 association functions of KlEst1 require its N-terminal domain but not its C terminus. Analysis of clusters of point mutations revealed residues in both the N-terminal TPR subdomain and the downstream helical subdomain (DSH) that are important for telomere maintenance and Ter1 association. A UV cross-linking assay was used to establish a direct physical interaction between KlEst1 and a putative stem-loop in Ter1, which also requires both the TPR and DSH subdomains. Moreover, similar to S. cerevisiae Ebs1 (ScEbs1) (but not ScEst1), KlEst1 confers rapamycin sensitivity and may be involved in nonsense-mediated decay. Interestingly, unlike telomere regulation, this apparently separate function of KlEst1 requires its C-terminal domain. Our findings provide insights on the mechanisms and evolution of Est1/Ebs1 homologues in budding yeast and present an attractive model system for analyzing members of this multifunctional protein family. 相似文献