全文获取类型
收费全文 | 281篇 |
免费 | 23篇 |
出版年
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 14篇 |
2015年 | 9篇 |
2014年 | 17篇 |
2013年 | 28篇 |
2012年 | 36篇 |
2011年 | 22篇 |
2010年 | 14篇 |
2009年 | 12篇 |
2008年 | 15篇 |
2007年 | 16篇 |
2006年 | 11篇 |
2005年 | 13篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 12篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1975年 | 2篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1946年 | 2篇 |
排序方式: 共有304条查询结果,搜索用时 15 毫秒
31.
Ghantasala S Sameer Kumar Abhilash K Venugopal Anita Mahadevan Santosh Renuse H C Harsha Nandini A Sahasrabuddhe Harsh Pawar Rakesh Sharma Praveen Kumar Sudha Rajagopalan Keith Waddell Yarappa L Ramachandra Parthasarathy Satishchandra Raghothama Chaerkady T S Keshava Prasad K Shankar Akhilesh Pandey 《Clinical proteomics》2012,9(1):12
32.
Raman H Ryan PR Raman R Stodart BJ Zhang K Martin P Wood R Sasaki T Yamamoto Y Mackay M Hebb DM Delhaize E 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2008,116(3):343-354
Allele diversities of four markers specific to intron three, exon four and promoter regions of the aluminum (Al) resistance
gene of wheat (Triticum aestivum L.) TaALMT1 were compared in 179 common wheat cultivars used in international wheat breeding programs. In wheat cultivars released during
the last 93 years, six different promoter types were identified on the basis of allele size. A previous study showed that
Al resistance was not associated with a particular coding allele for TaALMT1 but was correlated with blocks of repeated sequence upstream of the coding sequence. We verified the linkage between these
promoter alleles and Al resistance in three doubled haploid and one intercross populations segregating for Al resistance.
Molecular and pedigree analysis suggest that Al resistance in modern wheat germplasm is derived from several independent sources.
Analysis of a population of 278 landraces and subspecies of wheat showed that most of the promoter alleles associated with
Al resistance pre-existed in Europe, the Middle East and Asia prior to dispersal of cultivated germplasm around the world.
Furthermore, several new promoter alleles were identified among the landraces surveyed. The TaALMT1 promoter alleles found within the spelt wheats were consistent with the hypothesis that these spelts arose on several independent
occasions from hybridisations between non-free-threshing tetraploid wheats and Al-resistant hexaploid bread wheats. The strong
correlation between Al resistance and Al-stimulated malate efflux from the root apices of 49 diverse wheat genotypes examined
was consistent with the previous finding that Al resistance in wheat is conditioned primarily by malate efflux. These results
demonstrate that the markers based on intron, exon and promoter regions of TaALMT1 can trace the inheritance of the Al resistance locus within wheat pedigrees and track Al resistance in breeding programmes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
33.
In verbal communication, not only the meaning of the words convey information, but also the tone of voice (prosody) conveys crucial information about the emotional state and intentions of others. In various studies right frontal and right temporal regions have been found to play a role in emotional prosody perception. Here, we used triple-pulse repetitive transcranial magnetic stimulation (rTMS) to shed light on the precise time course of involvement of the right anterior superior temporal gyrus and the right fronto-parietal operculum. We hypothesized that information would be processed in the right anterior superior temporal gyrus before being processed in the right fronto-parietal operculum. Right-handed healthy subjects performed an emotional prosody task. During listening to each sentence a triplet of TMS pulses was applied to one of the regions at one of six time points (400-1900 ms). Results showed a significant main effect of Time for right anterior superior temporal gyrus and right fronto-parietal operculum. The largest interference was observed half-way through the sentence. This effect was stronger for withdrawal emotions than for the approach emotion. A further experiment with the inclusion of an active control condition, TMS over the EEG site POz (midline parietal-occipital junction), revealed stronger effects at the fronto-parietal operculum and anterior superior temporal gyrus relative to the active control condition. No evidence was found for sequential processing of emotional prosodic information from right anterior superior temporal gyrus to the right fronto-parietal operculum, but the results revealed more parallel processing. Our results suggest that both right fronto-parietal operculum and right anterior superior temporal gyrus are critical for emotional prosody perception at a relatively late time period after sentence onset. This may reflect that emotional cues can still be ambiguous at the beginning of sentences, but become more apparent half-way through the sentence. 相似文献
34.
Shen M Reitman ZJ Zhao Y Moustafa I Wang Q Arnold JJ Pathak HB Cameron CE 《The Journal of biological chemistry》2008,283(2):875-888
Picornaviruses have a peptide termed VPg covalently linked to the 5'-end of the genome. Attachment of VPg to the genome occurs in at least two steps. First, Tyr-3 of VPg, or some precursor thereof, is used as a primer by the viral RNA-dependent RNA polymerase, 3Dpol, to produce VPg-pUpU. Second, VPg-pUpU is used as a primer to produce full-length genomic RNA. Production of VPg-pUpU is templated by a single adenylate residue located in the loop of an RNA stem-loop structure termed oriI by using a slide-back mechanism. Recruitment of 3Dpol to and its stability on oriI have been suggested to require an interaction between the back of the thumb subdomain of 3Dpol and an undefined region of the 3C domain of viral protein 3CD. We have performed surface acidic-to-alanine-scanning mutagenesis of 3C to identify the surface of 3C with which 3Dpol interacts. This analysis identified numerous viable poliovirus mutants with reduced growth kinetics that correlated to reduced kinetics of RNA synthesis that was attributable to a change in VPg-pUpU production. Importantly, these 3C derivatives were all capable of binding to oriI as well as wild-type 3C. Synthetic lethality was observed for these mutants when placed in the context of a poliovirus mutant containing 3Dpol-R455A, a residue on the back of the thumb required for VPg uridylylation. These data were used to guide molecular docking of the structures for a poliovirus 3C dimer and 3Dpol, leading to a structural model for the 3C(2)-3Dpol complex that extrapolates well to all picornaviruses. 相似文献
35.
Pathak HB Oh HS Goodfellow IG Arnold JJ Cameron CE 《The Journal of biological chemistry》2008,283(45):30677-30688
The 5' ends of all picornaviral RNAs are linked covalently to the genome-encoded peptide, VPg (or 3B). VPg linkage is thought to occur in two steps. First, VPg serves as a primer for production of diuridylylated VPg (VPg-pUpU) in a reaction catalyzed by the viral polymerase that is templated by an RNA element (oriI). It is currently thought that the viral 3AB protein is the source of VPg in vivo. Second, VPg-pUpU is transferred to the 3' end of plus- and/or minus-strand RNA and serves as primer for production of full-length RNA. Nothing is known about the mechanism of transfer. We present biochemical and biological evidence refuting the use of 3AB as the donor for VPg uridylylation. Our data are consistent with precursors 3BC and/or 3BCD being employed for uridylylation. This conclusion is supported by in vitro uridylylation of these proteins, the ability of a mutant replicon incapable of producing processed VPg to replicate in HeLa cells and cell-free extracts and corresponding precursor processing profiles, and the demonstration of 3BC-linked RNA in mutant replicon-transfected cells. These data permit elaboration of our model for VPg uridylylation to include the use of precursor proteins and invoke a possible mechanism for location of the diuridylylated, VPg-containing precursor at the 3' end of plus- or minus-strand RNA for production of full-length RNA. Finally, determinants of VPg uridylylation efficiency suggest formation and/or collapse or release of the uridylylated product as the rate-limiting step in vitro depending upon the VPg donor employed. 相似文献
36.
Bais R 《The Clinical biochemist. Reviews / Australian Association of Clinical Biochemists》2008,29(Z1):S27-S31
* For detection of errors where the standard deviation is wide compared to clinical requirements, consider use of the Capability Index (Cps). * Cps is defined as 'Allowable Limit of Error divided by the standard deviation of between-batch QC measurement'. * 'Capable' assays have Cps >4 compared with 'incapable' ones with Cps <4. * Capability of an analyte can be used to optimise the amount of quality control (QC) required and still maintain appropriate error detection. * For EQA material, Cps can be used for continuously monitoring individual analytes, comparing laboratory performance with peers and comparison with industry-wide performance. * The capability approach can result in reducing the number of QCs run per day, reducing costs as well as significantly improving the performance of a number of assays. 相似文献
37.
Biogeographical variation in community response to root allelochemistry: novel weapons and exotic invasion 总被引:16,自引:0,他引:16
Jorge M. Vivanco Harsh P. Bais Frank R. Stermitz Giles C. Thelen Ragan M. Callaway 《Ecology letters》2004,7(4):285-292
Centaurea diffusa is one of the most destructive invasive weeds in the western USA and allelopathy appears to contribute to its invasiveness ( Callaway & Aschehoug 2000 ). Here we identify a chemical from the root exudates of C. diffusa, 8‐hydroxyquinoline, not previously reported as a natural product, and find that it varies biogeographically in its natural concentration and its effect as an allelochemical. 8‐Hydroxyquinoline is at least three times more concentrated in C. diffusa‐invaded North American soils than in this weed's native Eurasian soils and has stronger phytotoxic effects on grass species from North America than on grass species from Eurasia. Furthermore, experimental communities built from North American plant species are far more susceptible to invasion by C. diffusa than communities built from Eurasian species, regardless of the biogeographical origin of the soil biota. Sterilization of North American soils suppressed C. diffusa more than sterilization of Eurasian soils, indicating that North American soil biota may also promote invasion by C. diffusa. Eurasian plants and soil microbes may have evolved natural resistance to 8‐hydroxyquinoline while North American plants have not, suggesting a remarkable potential for evolutionary compatibility and homeostasis among plants within natural communities and a mechanism by which exotic weeds destroy these communities. 相似文献
38.
Direct Visualization of Spatial and Temporal Patterns of Antimicrobial Action within Model Oral Biofilms
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Shoji Takenaka Harsh M. Trivedi Audrey Corbin Betsey Pitts Philip S. Stewart 《Applied microbiology》2008,74(6):1869-1875
A microscopic method for noninvasively visualizing the action of an antimicrobial agent inside a biofilm was developed and applied to describe spatial and temporal patterns of mouthrinse activity on model oral biofilms. Three species biofilms of Streptococcus oralis, Streptococcus gordonii, and Actinomyces naeslundii were grown in glass capillary flow cells. Bacterial cells were stained with the fluorogenic esterase substrate Calcien AM (CAM). Loss of green fluorescence upon exposure to an antimicrobial formulation was subsequently imaged by time-lapse confocal laser scanning microscopy. When an antimicrobial mouthrinse containing chlorhexidine digluconate was administered, a gradual loss of green fluorescence was observed that began at the periphery of cell clusters where they adjoined the flowing bulk fluid and progressed inward over a time period of several minutes. Image analysis was performed to quantify a penetration velocity of 4 μm/min. An enzyme-based antimicrobial formulation led to a gradual, continually slowing loss of fluorescence in a pattern that was qualitatively different from the behavior observed with chlorhexidine. Ethanol at 11.6% had little effect on the biofilm. None of these treatments resulted in the removal of biomass from the biofilm. Most methods to measure or visualize antimicrobial action in biofilms are destructive. Spatial information is important because biofilms are known for their structural and physiological heterogeneity. The CAM staining technique has the potential to provide information about the rate of antimicrobial penetration, the presence of tolerant subpopulations, and the extent of biomass removal effected by a treatment. 相似文献
39.
Twelve fungi namelyAlternaria alternata, Aspergillus flavus, A niger, A ochraceus, Actinomucor repens, Capnodoium spp., Curvularia lunata, Fusarium
pallidoroseum, F solani, F verticillioides, Penicillium citrinum and Rhizopus stolonifer were recorded from samples ofAegle marmelos, Aesculus indica, Buchanania lanzan andPinus gerardiana. In case ofPrunus amygdalus only Rstolonifer was recorded. A significant variation in pattern of mycoflora incidence was observed in terms of source and season. Fungal
infestation in most of the substrates was found to be highest during monsoon. Aflatoxins were the most common mycotoxins elaborated
by different isolates ofA flavus obtained fromA marmelos, B lanzan andP gerardiana. The amount of aflatoxins produced by the toxigenic isolates ofA flavus was in the range of traces to 0.9–26.0 μg/ml inA marmelos, 0.8–17.5 μg/ml inP gerardiana and 0.65–13.2 μg/ml inB lanzan. The percentage toxigenicity was comparatively lower in the isolates of other mycotoxigenic fungi. Aflatoxins were detected
almost in all the samples analyzed for mycotoxin contamination. However, traces of zearalenone were detected inA marmelos. The concentration of aflatoxin B1 was in the range of 0.13–0.75 μg/g inA marmelos, 0.09–0.60 μg/g inP gerardiana and 0.01–0.20 ug/g inB lanzan. Mycotoxins were not detected inAesculus indica andPrunus amygdalus. 相似文献
40.
Harsh Pal Bais Julie B. Green Travis S. Walker Paul O. Okemo Jorge M. Vivanco 《In vitro cellular & developmental biology. Plant》2002,38(6):598-601
Summary
Spilanthes mauritiana DC., (Compositae), a East African medicinal herb containing pharmaceutically promising secondary metabolites, has successfully
been raised in vitro. We have developed a clonal propagation protocol that uses juvenile plants as starting material. The addition of benzylaminopurine
(BA) (1.0 μM) and naphthaleneacetic acid (NAA) (0.1 μM) to the culture medium resulted in maximum shooting response with minimal callusing. Shoots rooted best in vitro in MS medium supplemented with indole-3-acetic acid (IAA; 0.2 μM), and plants that had already developed roots showed better growth, with maximum survival rate, in the greenhouse after an
initial hardening. 相似文献