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131.
- During an investigation of the physiology of Azotobacter vinelandii with particular reference to polysaccharide formation, a suitable medium which was precipitate-free was developed by adding EDTA at a concentration of 50 mg/l to a basal medium containing one of eight different carbohydrates as sole carbon source.
- Acetylated alginate was always produced by the organism when cultured under defined conditions, regardless of the carbohydrate source incorporated in the basal medium.
- When EDTA was added to the medium, the bacteria produced acetylated polyuronides with a preponderance of mannuronic acid residues.
- A comparison of the infrared spectra of the alginate produced by Azotobacter vinelandii and the affect of EDTA upon the mannuronic acid/guluronic acid ratios of the alginate are reported.
132.
Yong-Bi Fu Gregory W. Peterson Brent D. McCallum Li Huang 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2010,120(2):271-281
Little is known about the genetic control of heterosis in the complex polyploid crop species oilseed rape (Brassica napus L.). In this study, two large doubled-haploid (DH) mapping populations and two corresponding sets of backcrossed test hybrids
(THs) were analysed in controlled greenhouse experiments and extensive field trials for seedling biomass and yield performance
traits, respectively. Genetic maps from the two populations, aligned with the help of common simple sequence repeat markers,
were used to localise and compare quantitative trait loci (QTL) related to the expression of heterosis for seedling developmental
traits, plant height at flowering, thousand seed mass, seeds per silique, siliques per unit area and seed yield. QTL were
mapped using data from the respective DH populations, their corresponding TH populations and from mid-parent heterosis (MPH)
data, allowing additive and dominance effects along with digenic epistatic interactions to be estimated. A number of genome
regions containing numerous heterosis-related QTL involved in different traits and at different developmental stages were
identified at corresponding map positions in the two populations. The co-localisation of per se QTL from the DH population
datasets with heterosis-related QTL from the MPH data could indicate regulatory loci that may also contribute to fixed heterosis
in the highly duplicated B. napus genome. Given the key role of epistatic interactions in the expression of heterosis in oilseed rape, these QTL hotspots might
harbour genes involved in regulation of heterosis (including fixed heterosis) for different traits throughout the plant life
cycle, including a significant overall influence on heterosis for seed yield. 相似文献
133.
134.
Comparative sequence analysis of the symbiosis island of Mesorhizobium loti strain R7A 总被引:9,自引:0,他引:9 下载免费PDF全文
Sullivan JT Trzebiatowski JR Cruickshank RW Gouzy J Brown SD Elliot RM Fleetwood DJ McCallum NG Rossbach U Stuart GS Weaver JE Webby RJ De Bruijn FJ Ronson CW 《Journal of bacteriology》2002,184(11):3086-3095
The Mesorhizobium loti strain R7A symbiosis island is a 502-kb chromosomally integrated element which transfers to nonsymbiotic mesorhizobia in the environment, converting them to Lotus symbionts. It integrates into a phenylalanine tRNA gene in a process mediated by a P4-type integrase encoded at the left end of the element. We have determined the nucleotide sequence of the island and compared its deduced genetic complement with that reported for the 611-kb putative symbiosis island of M. loti strain MAFF303099. The two islands share 248 kb of DNA, with multiple deletions and insertions of up to 168 kb interrupting highly conserved colinear DNA regions in the two strains. The shared DNA regions contain all the genes likely to be required for Nod factor synthesis, nitrogen fixation, and island transfer. Transfer genes include a trb operon and a cluster of potential tra genes which are also present on the strain MAFF303099 plasmid pMLb. The island lacks plasmid replication genes, suggesting that it is a site-specific conjugative transposon. The R7A island encodes a type IV secretion system with strong similarity to the vir pilus from Agrobacterium tumefaciens that is deleted from MAFF303099, which in turn encodes a type III secretion system not found on the R7A island. The 414 genes on the R7A island also include putative regulatory genes, transport genes, and an array of metabolic genes. Most of the unique hypothetical genes on the R7A island are strain-specific and clustered, suggesting that they may represent other acquired genetic elements rather than symbiotically relevant DNA. 相似文献
135.
Robbins JR Monack D McCallum SJ Vegas A Pham E Goldberg MB Theriot JA 《Molecular microbiology》2001,41(4):861-872
The generation and maintenance of subcellular organization in bacteria is critical for many cell processes and properties, including growth, structural integrity and, in pathogens, virulence. Here, we investigate the mechanisms by which the virulence protein IcsA (VirG) is distributed on the bacterial surface to promote efficient transmission of the bacterium Shigella flexneri from one host cell to another. The outer membrane protein IcsA recruits host factors that result in actin filament nucleation and, when concentrated at one bacterial pole, promote unidirectional actin-based motility of the pathogen. We show here that the focused polar gradient of IcsA is generated by its delivery exclusively to one pole followed by lateral diffusion through the outer membrane. The resulting gradient can be modified by altering the composition of the outer membrane either genetically or pharmacologically. The gradient can be reshaped further by the action of the protease IcsP (SopA), whose activity we show to be near uniform on the bacterial surface. Further, we report polar delivery of IcsA in Escherichia coli and Yersinia pseudotuberculosis, suggesting that the mechanism for polar delivery of some outer membrane proteins is conserved across species and that the virulence function of IcsA capitalizes on a more global mechanism for subcellular organization. 相似文献
136.
David G. Hamilton Menna E. Jones Elissa Z. Cameron Douglas H. Kerlin Hamish McCallum Andrew Storfer Paul A. Hohenlohe Rodrigo K. Hamede 《Proceedings. Biological sciences / The Royal Society》2020,287(1940)
Infectious diseases, including transmissible cancers, can have a broad range of impacts on host behaviour, particularly in the latter stages of disease progression. However, the difficulty of early diagnoses makes the study of behavioural influences of disease in wild animals a challenging task. Tasmanian devils (Sarcophilus harrisii) are affected by a transmissible cancer, devil facial tumour disease (DFTD), in which tumours are externally visible as they progress. Using telemetry and mark–recapture datasets, we quantify the impacts of cancer progression on the behaviour of wild devils by assessing how interaction patterns within the social network of a population change with increasing tumour load. The progression of DFTD negatively influences devils'' likelihood of interaction within their network. Infected devils were more active within their network late in the mating season, a pattern with repercussions for DFTD transmission. Our study provides a rare opportunity to quantify and understand the behavioural feedbacks of disease in wildlife and how they may affect transmission and population dynamics in general. 相似文献
137.
Design and synthesis of RNA miniduplexes via a synthetic linker approach. 2. Generation of covalently closed, double-stranded cyclic HIV-1 TAR RNA analogs with high Tat-binding affinity. 总被引:3,自引:3,他引:0 下载免费PDF全文
M Y X Ma K McCallum S C Climie R Kuperman W C Lin M Sumner-Smith R W Barnett 《Nucleic acids research》1993,21(11):2585-2589
138.
Wheat bran cell walls were subjected to mild acid hydrolysis and the major phenolic product was purified and identified as 5-O-(trans-feruloyl)-arabinofuranose. Sensitive continuous and stopped, microtiter plate-based spectrophotometric assays for trans-feruloyl esterase activity were developed using this compound as substrate. Procedures were also developed for the detection of trans-feruloyl esterase activities on gels following electrophoresis using this compound. These procedures are applicable to other natural feruloyl esters derived from plant cell walls by enzymatic hydrolysis. The extracellular trans-feruloyl esterases of Aspergillus niger 814 grown on 1% wheat bran were fractionated by anion-exchange chromatography and isoelectric focusing. These studies indicate that there are multiple forms of trans-feruloyl esterase but that most activity is associated with a major isozyme with a pI of 3.2. 相似文献
139.
Jeremy E. B. McCallum Christopher W. Coyle Ryan R. Elson Blake A. Titterington 《Nucleosides, nucleotides & nucleic acids》2018,37(3):169-178
The development of small molecules to stabilize the G-quadruplex structure has garnered significant attention for anticancer drug discovery. Herein, we report the synthesis of several 4,4′-diaminoazobenzene derivatives containing different substituent groups and their ability to bind and stabilize telomeric G-quadruplex DNA. Circular dichroism (CD) spectroscopy was performed to characterize the quadruplex topologies, measure stabilization effects, and evaluate their capabilities for conformational photoregulation. 4,4′-Diaminoazobenzene derivatives were found to moderately stabilize quadruplex structures but not affect conformational photoregulation. This work further develops the design and general understanding of the stabilization effects of small molecules with telomeric G-quadruplex DNA. 相似文献