全文获取类型
收费全文 | 193篇 |
免费 | 17篇 |
专业分类
210篇 |
出版年
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 10篇 |
2016年 | 7篇 |
2015年 | 12篇 |
2014年 | 9篇 |
2013年 | 16篇 |
2012年 | 17篇 |
2011年 | 19篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 9篇 |
2007年 | 14篇 |
2006年 | 8篇 |
2005年 | 8篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 9篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有210条查询结果,搜索用时 0 毫秒
31.
Teeri TH Elomaa P Kotilainen M Albert VA 《BioEssays : news and reviews in molecular, cellular and developmental biology》2006,28(7):756-767
Gerbera hybrida is a member of the large sunflower family (Asteraceae). Typical of Asteraceae, Gerbera bears different types of flowers in its inflorescence. The showy marginal flowers comprise elongate, ligulate corollas that are female, whereas the central and inconspicuous disc flowers are complete, with both male and female organs. As such, Gerbera offers great potential for comparative developmental research within a single genotype. Moreover, different Gerbera varieties show an impressive spectrum of color patterns, directly displaying responses to developmental cues at all important morphological levels (flower type, flower organ and within organs). Further, Gerbera harbors an arsenal of Asteraceae-type secondary metabolites, not present in other model plants. With powerful reverse genetics methods, a large collection of EST sequences and a new cDNA microarray, Gerbera has become a model plant of the sunflower family. 相似文献
32.
Kärkönen A Koutaniemi S Mustonen M Syrjänen K Brunow G Kilpeläinen I Teeri TH Simola LK 《Physiologia plantarum》2002,114(3):343-353
Activity of a number of enzymes related to lignin formation was measured in a Picea abies (L) Karsten suspension culture that is able to produce native-like lignin into the nutrient medium. This cell culture is an attractive model for studying lignin formation, as the process takes place independently of the complex macromolecular matrix of the native apoplast. Suspension culture proteins were fractionated into soluble cellular proteins, ionically and covalently bound cell wall proteins and nutrient medium proteins. The nutrient medium contained up to 5.3% of total coniferyl alcohol peroxidase (EC 1.11.1.7) activity and a significant NADH oxidase activity that is suggested to be responsible for hydrogen peroxide (H2O2) production. There also existed some malate dehydrogenase (EC 1.1.1.37) activity in the apoplast of suspension culture cells (in ionically and covalently bound cell wall protein fractions), possibly for the regeneration of NADH that is needed for peroxidase-catalysed H2O2 production. However, there is no proof of the existence of NADH in the apoplast. Nutrient medium peroxidases could be classified into acidic, slightly basic and highly basic isoenzyme groups by isoelectric focusing. Only acidic peroxidases were found in the covalently bound cell wall protein fraction. Several peroxidase isoenzymes across the whole pI range were detected in the protein fraction ionically bound to cell walls and in the soluble cellular protein fraction. One laccase-like isoenzyme with pI of approximately 8.5 was found in the nutrient medium that was able to form dehydrogenation polymer from coniferyl alcohol in the absence of H2O2. The total activity of this oxidase towards coniferyl alcohol was, however, several orders of magnitude smaller than that of peroxidases in vitro. According to 2D 1H-13C correlation NMR spectra, most of the abundant structural units of native lignin and released suspension culture lignin are present in the oxidase produced dehydrogenation polymer but in somewhat different amounts compared to peroxidase derived synthetic lignin preparations. A coniferin beta-glucosidase (EC 3.2.1.21) was observed to be secreted into the culture medium. 相似文献
33.
Teemu Smura Soile Blomqvist Tytti Vuorinen Olga Ivanova Elena Samoilovich Haider Al-Hello Carita Savolainen-Kopra Tapani Hovi Merja Roivainen 《PloS one》2014,9(4)
Genus Enterovirus (Family Picornaviridae,) consists of twelve species divided into genetically diverse types by their capsid protein VP1 coding sequences. Each enterovirus type can further be divided into intra-typic sub-clusters (genotypes). The aim of this study was to elucidate what leads to the emergence of novel enterovirus clades (types and genotypes). An evolutionary analysis was conducted for a sub-group of Enterovirus C species that contains types Coxsackievirus A21 (CVA-21), CVA-24, Enterovirus C95 (EV-C95), EV-C96 and EV-C99. VP1 gene datasets were collected and analysed to infer the phylogeny, rate of evolution, nucleotide and amino acid substitution patterns and signs of selection. In VP1 coding gene, high intra-typic sequence diversities and robust grouping into distinct genotypes within each type were detected. Within each type the majority of nucleotide substitutions were synonymous and the non-synonymous substitutions tended to cluster in distinct highly polymorphic sites. Signs of positive selection were detected in some of these highly polymorphic sites, while strong negative selection was indicated in most of the codons. Despite robust clustering to intra-typic genotypes, only few genotype-specific ‘signature’ amino acids were detected. In contrast, when different enterovirus types were compared, there was a clear tendency towards fixation of type-specific ‘signature’ amino acids. The results suggest that permanent fixation of type-specific amino acids is a hallmark associated with evolution of different enterovirus types, whereas neutral evolution and/or (frequency-dependent) positive selection in few highly polymorphic amino acid sites are the dominant forms of evolution when strains within an enterovirus type are compared. 相似文献
34.
Quaternary structure built from subunits combining NMR and small-angle x-ray scattering data 总被引:5,自引:0,他引:5 下载免费PDF全文
Mattinen ML Pääkkönen K Ikonen T Craven J Drakenberg T Serimaa R Waltho J Annila A 《Biophysical journal》2002,83(2):1177-1183
A new principle in constructing molecular complexes from the known high-resolution domain structures joining data from NMR and small-angle x-ray scattering (SAXS) measurements is described. Structure of calmodulin in complex with trifluoperazine was built from N- and C-terminal domains oriented based on residual dipolar couplings measured by NMR in a dilute liquid crystal, and the overall shape of the complex was derived from SAXS data. The residual dipolar coupling data serves to reduce angular degrees of freedom, and the small-angle scattering data serves to confine the translational degrees of freedom. The complex built by this method was found to be consistent with the known crystal structure. The study demonstrates how approximate tertiary structures of modular proteins or quaternary structures composed of subunits can be assembled from high-resolution structures of domains or subunits using mutually complementary NMR and SAXS data. 相似文献
35.
36.
Loss‐of‐function screening by CRISPR/Cas9 gene knockout with pooled, lentiviral guide libraries is a widely applicable method for systematic identification of genes contributing to diverse cellular phenotypes. Here, Random Sequence Labels (RSLs) are incorporated into the guide library, which act as unique molecular identifiers (UMIs) to allow massively parallel lineage tracing and lineage dropout screening. RSLs greatly improve the reproducibility of results by increasing both the precision and the accuracy of screens. They reduce the number of cells needed to reach a set statistical power, or allow a more robust screen using the same number of cells. 相似文献
37.
Borja Jiménez‐Alfaro Michal Hájek Rasmus Ejrnaes John Rodwell Paweł Pawlikowski Eddy J. Weeda Jarmo Laitinen Absjørn Moen Ariel Bergamini Liene Aunina Lucia Sekulová Teemu Tahvanainen François Gillet Ute Jandt Daniel Dítě Petra Hájková Gilles Corriol Hanna Kondelin Tomás E. Díaz 《应用植被学》2014,17(2):367-380
38.
Teemu Kuosmanen Johannes Cairns Robert Noble Niko Beerenwinkel Tommi Mononen Ville Mustonen 《PLoS computational biology》2021,17(9)
Increasing body of experimental evidence suggests that anticancer and antimicrobial therapies may themselves promote the acquisition of drug resistance by increasing mutability. The successful control of evolving populations requires that such biological costs of control are identified, quantified and included to the evolutionarily informed treatment protocol. Here we identify, characterise and exploit a trade-off between decreasing the target population size and generating a surplus of treatment-induced rescue mutations. We show that the probability of cure is maximized at an intermediate dosage, below the drug concentration yielding maximal population decay, suggesting that treatment outcomes may in some cases be substantially improved by less aggressive treatment strategies. We also provide a general analytical relationship that implicitly links growth rate, pharmacodynamics and dose-dependent mutation rate to an optimal control law. Our results highlight the important, but often neglected, role of fundamental eco-evolutionary costs of control. These costs can often lead to situations, where decreasing the cumulative drug dosage may be preferable even when the objective of the treatment is elimination, and not containment. Taken together, our results thus add to the ongoing criticism of the standard practice of administering aggressive, high-dose therapies and motivate further experimental and clinical investigation of the mutagenicity and other hidden collateral costs of therapies. 相似文献
39.
Marjamaa K Hildén K Kukkola E Lehtonen M Holkeri H Haapaniemi P Koutaniemi S Teeri TH Fagerstedt K Lundell T 《Plant molecular biology》2006,61(4-5):719-732
Plant class III peroxidases (POXs) take part in the formation of lignin and maturation of plant cell walls. However, only
a few examples of such peroxidases from gymnosperm tree species with highly lignified xylem tracheids have been implicated
so far. We report here cDNA cloning of three xylem-expressed class III peroxidase encoding genes from Norway spruce (Picea abies). The translated proteins, PX1, PX2 and PX3, contain the conserved amino acids required for heme-binding and peroxidase catalysis.
They all begin with putative secretion signal propeptide sequences but diverge substantially at phylogenetic level, grouping
to two subclusters when aligned with other class III plant peroxidases. In situ hybridization analysis on expression of the
three POXs in Norway spruce seedlings showed that mRNA coding for PX1 and PX2 accumulated in the cytoplasm of young, developing
tracheids within the current growth ring where lignification is occurring. Function of the putative N-terminal secretion signal
peptides for PX1, PX2 and PX3 was confirmed by constructing chimeric fusions with EGFP (enhanced green fluorescent protein)
and expressing them in tobacco protoplasts. Full-length coding region of px1 was also heterologously expressed in Catharanthus roseus hairy root cultures. Thus, at least the spruce PX1 peroxidase is processed via the endoplasmic reticulum (ER) most likely
for secretion to the cell wall. Thereby, PX1 displays correct spatiotemporal localization for participation in the maturation
of the spruce tracheid secondary cell wall. 相似文献
40.
Ojanen T Rauhala T Häkkinen K 《Journal of strength and conditioning research / National Strength & Conditioning Association》2007,21(1):216-222
Thirty-two master athletes (shot put, discus, and hammer throw) were divided into 4 groups according to their age (T40 [40 years of age], 50 [50 years of age], 60 [60 years of age], and 75 [75 years of age]). Twenty-eight age-matched men served as controls (C40 [40 years of age], 50 [50 years of age], 60 [60 years of age], and 75 [75 years of age]). The subjects were tested for maximal isometric strength of the lower and upper extremities. Power was measured by performing jump squats and bench press in the Smith machine with the load of 60% of 1 repetition maximum. Electromyographic (EMG) activity was recorded from 6 different muscles. The muscle thickness of vastus lateralis and intermedius (VL+VI) and triceps brachii (TB) was measured by ultrasound. Maximal strength differed (p < 0.05- 0.001) in all testing actions between T40 and T60 and T40 and T75 as well as between T and C groups. Both VL+VI and TB thickness in T40 was greater (p < 0.05-0.01) than in T60 and T75 and in T was larger than in C groups. Average force during the first 500 milliseconds (ms) was higher (p < 0.05-0.001) in T40 compared to T50, T60, and T75 in bilateral leg extension, biceps curl, and especially in unilateral knee flexion. T40 produced higher power than the other groups (p < 0.05-0.001). The relative agonist EMG activation (VL) in leg extension during the first 100 ms compared to maximum activation was lower (p < 0.05) in T50, T60, and T75, but not in T40. The present data indicate that maximal strength and muscle thickness as well as explosive strength and power characteristics decline with aging also in master athletes who carry out strength training and throwing exercises actively over several decades. Nevertheless, in master athletes, maximal strength and muscle mass as well as explosive force production of the upper and lower extremities seem to be at remarkably higher levels than those recorded for age-matched control men. 相似文献