全文获取类型
收费全文 | 230篇 |
免费 | 9篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 6篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 10篇 |
2012年 | 14篇 |
2011年 | 8篇 |
2010年 | 8篇 |
2009年 | 6篇 |
2008年 | 12篇 |
2007年 | 10篇 |
2006年 | 12篇 |
2005年 | 6篇 |
2004年 | 12篇 |
2003年 | 6篇 |
2002年 | 11篇 |
2001年 | 9篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 4篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1971年 | 4篇 |
1970年 | 12篇 |
1969年 | 2篇 |
1966年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有239条查询结果,搜索用时 94 毫秒
81.
L. E. Meshalkina G. A. Kochetov G. Hubner K. Tittmann R. Golbik 《Biochemistry. Biokhimii?a》2009,74(3):293-300
In this work, we investigated the rate of formation of the central intermediate of the transketolase reaction with thiamine diphosphate (ThDP) or 4′-methylamino-ThDP as cofactors and its stability using stopped-flow spectroscopy and circular dichroism (CD) spectroscopy. The intermediates of the transketolase reaction were analyzed by NMR spectroscopy. The kinetic stability of the intermediate was shown to be dependent on the state of the amino group of the coenzyme. The rates of the intermediate formation were the same in the case of the native and methylated ThDP, but the rates of the protonation or oxidation of the complex in the ferricyanide reaction were significantly higher in the complex with methylated ThDP. A new negative band was detected in the CD spectrum of the complex transketolase—4′-methylamino-ThDP corresponding to the protonated dihydroxyethyl-4′-methylamino-ThDP released from the active sites of the enzyme. These data suggest that transketolase in the complex with the NH2-methylated ThDP exhibits dihydroxyethyl-4′-methylamino-ThDP-synthase activity. Thus, the 4′-amino group of the coenzyme provides kinetic stability of the central intermediate of the transketolase reaction, dihydroxyethyl-ThDP. 相似文献
82.
Ludmilla E. Meshalkina German A. Kochetov Gerhard Hübner Kai Tittmann Ralph Golbik 《Journal of Molecular Catalysis .B, Enzymatic》2009,61(1-2):67
Transketolase (TK), a thiamin diphosphate (ThDP) dependent enzyme, catalyzes the reversible transfer of a two-carbon unit from keto- to aldo-substrates. Dihydroxyethylthiamin diphosphate (DHEThDP), formed as a result of cleavage of the donor substrate, serves as an intermediate of the TK reaction. TK from the yeast Saccharomyces cerevisiae is unique among thiamin enzymes displaying enzymatic activity after reconstitution with a methylated analogue of the native cofactor, 4′-methylamino-ThDP. The reconstitution of the apoenzyme with both ThDP and the methylated analogue can be analyzed by near UV circular dichroism. It was demonstrated that in the native holoenzyme and in the complex of TK with 4′-methylamino-ThDP the formation of the dihydroxyethyl-based carbanion/enamine took place with comparable rate constants, whereas the protonation of the reactive species was much faster in the complex with the analogue. The enzymatic activity of the enzyme reconstituted with 4′-methylamino-ThDP was 10fold higher in the ferricyanide assay. We suggest that a methylation of the 4′-amino group of ThDP impairs the resonance stabilization of the carbanion/enamine intermediate both sterically and electronically, thus allowing either a faster protonation or oxidation reaction by ferricyanide. The formation of the optically active DHE-4′-methylamino-ThDP was monitored by near UV circular dichroism spectra and corroborated by 1H NMR analysis. The protonated form of the intermediate DHE-4′-methylamino-ThDP was released from the active sites of TK and accumulated in the medium on preparative scale. 相似文献
83.
It is known that 5'-untranslated sequences of eukaryotic mRNA often contain AUG triplets, which may serve as the sites of translation initiation. It is thought that these leader open reading frames can fulfil the regulatory functions and encode functionally active proteins. However, they have been incompletely characterized. The article deals with the context organization of leader reading frames of eukaryotic mRNAs. It has been shown that their characteristics correlate with the position relative to the protein-encoding sequence, which may be associated with the efficiency of initiation of translation. 相似文献
84.
A computer model of the spatial structure of transketolase-like protein (TKTL1), a marker of certain tumor tissues, has been
constructed using the known spatial structure of transketolase found in normal human tissues. The structure of the two proteins
at all levels of their organization has also been compared. On the basis of the revealed differences in structures of these
proteins, we assume it is unlikely that TKTL1 can be a thiamine diphosphate-dependent protein capable of catalyzing the transketolase
reaction. 相似文献
85.
E. A. Trifonova A. V. Romanova S. S. Sangaev M. V. Sapotsky V. I. Malinovsky A. V. Kochetov 《Biologia Plantarum》2012,56(3):571-574
The gene of Zinnia elegans L. coding for S-like extracellular ribonuclease (ZRNase II) was used to produce transgenic tobacco plants with an increased ribonuclease activity. The protein-coding part of ZRNase
II included the signal peptide sequence so the transgenic protein was located extracellularly. The cDNA of ZRNase II was cloned under the control of 2′-promoter of the mannopine synthase (MAS 2′) gene from Ti-plasmid of Agrobacterium tumefaciens. It was shown that the resultant transgenic plants had an increased ribonuclease activity of the crude extracts and the induction
of MAS 2′ promoter by wounding additionally increased the activity. The plants of two transforming lines characterized by
different ribonuclease activities were used to analyze the transgene influence on plant resistance to tobacco mosaic virus.
The plants demonstrated either absence of disease symptoms or a significant delay in their appearance, depending on the virus
content in the inoculum and ribonuclease activity. 相似文献
86.
JC de Mauroy HR Weiss AG Aulisa L Aulisa JI Brox J Durmala C Fusco TB Grivas J Hermus T Kotwicki G Le Blay A Lebel L Marcotte S Negrini L Neuhaus T Neuhaus P Pizzetti L Revzina B Torres PJM Van Loon E Vasiliadis M Villagrasa M Werkman M Wernicka MS Wong F Zaina 《Scoliosis》2010,5(1):1-15
Abstract
Thoracic hyperkyphosis is a frequent problem and can impact greatly on patient's quality of life during adolescence. This condition can be idiopathic or secondary to Scheuermann disease, a disease disturbing vertebral growth. To date, there is no sound scientific data available on the management of this condition. Some studies discuss the effects of bracing, however no guidelines, protocols or indication's of treatment for this condition were found. The aim of this paper was to develop and verify the consensus on managing thoracic hyperkyphosis patients treated with braces and/or physiotherapy.Methods
The Delphi process was utilised in four steps gradually modified according to the results of a set of recommendations: we involved the SOSORT Board twice, then all SOSORT members twice, with a Pre-Meeting Questionnaire (PMQ), and during a Consensus Session at the SOSORT Lyon Meeting with a Meeting Questionnaire (MQ).Results
There was an unanimous agreement on the general efficacy of bracing and physiotherapy for this condition. Most experts suggested the use of 4-5 point bracing systems, however there was some controversy with regards to physiotherapeutic aims and modalities.Conclusion
The SOSORT panel of experts suggest the use of rigid braces and physiotherapy to correct thoracic hyperkyphosis during adolescence. The evaluation of specific braces and physiotherapy techniques has been recommended. 相似文献87.
Although prey species typically respond to the most limiting factors at coarse spatiotemporal scales while addressing biological requirements at finer scales, such behaviour may become challenging for species inhabiting human altered landscapes. We investigated how woodland caribou, a threatened species inhabiting North-American boreal forests, modified their fine-scale movements when confronted with forest management features (i.e. clearcuts and roads). We used GPS telemetry data collected between 2004 and 2010 on 49 female caribou in a managed area in Québec, Canada. Movements were studied using a use – availability design contrasting observed steps (i.e. line connecting two consecutive locations) with random steps (i.e. proxy of immediate habitat availability). Although caribou mostly avoided disturbances, individuals nonetheless modulated their fine-scale response to disturbances on a daily and annual basis, potentially compromising between risk avoidance in periods of higher vulnerability (i.e. calving, early and late winter) during the day and foraging activities in periods of higher energy requirements (i.e. spring, summer and rut) during dusk/dawn and at night. The local context in which females moved was shown to influence their decision to cross clearcut edges and roads. Indeed, although females typically avoided crossing clearcut edges and roads at low densities, crossing rates were found to rapidly increase in greater disturbance densities. In some instance, however, females were less likely to cross edges and roads as densities increased. Females may then be trapped and forced to use disturbed habitats, known to be associated with higher predation risk. We believe that further increases in anthropogenic disturbances could exacerbate such behavioural responses and ultimately lead to population level consequences. 相似文献
88.
Abstract It is known that the recognition of AUG triplet by eukaryotic ribosomes as a translation start site strongly depends on its nucleotide context. However, the relative significance of different context positions is not fully clear. In particular, it concerns the role of 3′-end part of the context located at the beginning of the protein-coding sequence. The significant bias observed in nucleotide frequencies in positions +4, +5, +6 (corresponding to the second codon of CDS) could result from different reasons and their contribution to start codon recognition and initiation of translation is under discussion. In this study, we conducted a comparative computational analysis of the human mRNA samples containing different nucleotides (adenine, guanine or pyrimidine) in the essential context position ?3. It was found that the presence of G in position +4 could be important for the context variant GnnAUG but not for AnnAUG. Interestingly, the second position of proteins encoded by mRNAs with AnnAUG context variant was specifically and significantly enriched with serine whereas the presence of GnnAUG context also correlated with a higher occurrence of alanine and glycine. It is likely that the efficiency of translation initiation process can depend on the interplay between 5′-context part, 3′-context part and the type of amino acid in the second position of the encoded protein. 相似文献
89.
90.
Florigio Lista Frans AG Reubsaet Riccardo De Santis Rene R Parchen Ad L de Jong Jasper Kieboom Anton L van der Laaken Ingrid AI Voskamp-Visser Silvia Fillo Hugo-Jan Jansen Jan Van der Plas Armand Paauw 《BMC microbiology》2011,11(1):1-11