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81.
82.
Two hundred and thirty-two strains of Escherichia coli belonging to infantile enteropathogenic serotypes isolated in the United Kingdom during 1980 and 1981 were tested for resistance to 10 antimicrobial drugs. Resistance to one or more drugs was found in 134 (57.8%) of the strains, with resistance to sulphonamides, streptomycin, tetracycline, and ampicillin occurring most commonly. Resistance was transferable in 65 out of 104 resistant strains. These findings are a cause for concern because they indicate that the choice of treatment for severe illness is limited and suggest that a large pool of drug-resistant organisms exists in the community. 相似文献
83.
Multiresistant strains of Salmonella typhimurium phage types 204 and 193 appeared in calves in 1977 and then spread epidemically in cattle. Food poisoning is the main route by which drug-resistant strains from cattle are spread to man, and by the end of 1979 these two multiresistant strains had been identified in 290 cases of human salmonellosis in Britain. Trimethoprim-resistant S typhimurium were rare until a strain of a new phage type, designated type 204c, spread in cattle in 1979. All isolations of type 204c were trimethoprim resistant. Trimethoprim had been used to treat cattle and this usage has probably contributed to the establishment of type 204c and the increased incidence of trimethoprim-resistant strains. The responsibility to prevent or control drug resistance in bovine S typhimurium lies with the veterinary profession, and more stringent regulatiions governing the use of antibiotics in animals bred for food may be necessary. 相似文献
84.
Bat boxes are often installed as substitute habitats to offset the loss of large, hollow-bearing trees. However, emerging evidence suggests that they are failing to achieve intended conservation outcomes as they only support generalist species. Despite these concerns, the effect of bat boxes on the dynamics of bat communities remains understudied. We assessed the bat community in reserves where bat boxes had been installed in comparison with reserves where they had not using ultrasonic surveys in 16 small bushland reserves throughout Sydney, Australia. Reserves containing bat boxes and those without had comparable species diversity and composition; however, the activity of the dominant species, Gould's wattled bat (Chalinolobus gouldii), was significantly higher at sites with bat boxes. Species that commonly forage in open vegetation, including C. gouldii, were significantly positively associated with sites that had bat boxes. Occupation of boxes by bats was not recorded in the study due to limited information on their locations, so further research is required to understand the direct effects of boxes and the bats that occupy them on the bat community. If bat boxes continue to be recommended as a biodiversity offset, a greater understanding of the potential impact they have on altered competitive relationships and community dynamics is essential. 相似文献
85.
Helena?Oakey Reza?Shafiei Jordi?Comadran Nicola?Uzrek Brian?Cullis Leonardo?D?Gomez Caragh?Whitehead Simon?J?McQueen-Mason Robbie?Waugh Claire?HalpinEmail author 《Biotechnology for biofuels》2013,6(1):185
Background
In this study, a multi-parent population of barley cultivars was grown in the field for two consecutive years and then straw saccharification (sugar release by enzymes) was subsequently analysed in the laboratory to identify the cultivars with the highest consistent sugar yield. This experiment was used to assess the benefit of accounting for both the multi-phase and multi-environment aspects of large-scale phenotyping experiments with field-grown germplasm through sound statistical design and analysis.Results
Complementary designs at both the field and laboratory phases of the experiment ensured that non-genetic sources of variation could be separated from the genetic variation of cultivars, which was the main target of the study. The field phase included biological replication and plot randomisation. The laboratory phase employed re-randomisation and technical replication of samples within a batch, with a subset of cultivars chosen as duplicates that were randomly allocated across batches. The resulting data was analysed using a linear mixed model that incorporated field and laboratory variation and a cultivar by trial interaction, and ensured that the cultivar means were more accurately represented than if the non-genetic variation was ignored. The heritability detected was more than doubled in each year of the trial by accounting for the non-genetic variation in the analysis, clearly showing the benefit of this design and approach.Conclusions
The importance of accounting for both field and laboratory variation, as well as the cultivar by trial interaction, by fitting a single statistical model (multi-environment trial, MET, model), was evidenced by the changes in list of the top 40 cultivars showing the highest sugar yields. Failure to account for this interaction resulted in only eight cultivars that were consistently in the top 40 in different years. The correspondence between the rankings of cultivars was much higher at 25 in the MET model. This approach is suited to any multi-phase and multi-environment population-based genetic experiment.86.
87.
Forced convection can significantly influence the heat loss from birds and their offspring but effects may be reduced by using sheltered micro-sites such as cavities or constructing nests. The structural and thermal properties of the nests of two species, the spiny-cheeked honeyeater (Acanthagenys rufogularis) and yellow-throated miner (Manorina flavigula), were measured in relation to three wind speeds. Nest dimensions differ between the two species, despite the similar body mass of the incubating adults, however nest conductance is comparable. As wind speed increases, so does the rate of heat loss from the nests of both species, and further still during incubation recesses. The significance of forced convection through the nest is a near-doubling in heat production required by the parent, even when incubating at relatively low wind speeds. This provides confirmation that selecting a sheltered nest site is important for avian reproductive success. 相似文献
88.
Murphy C Pillay V Choonara YE du Toit LC Ndesendo VM Chirwa N Kumar P 《AAPS PharmSciTech》2012,13(1):1-15
In order to overcome poor bioavailability of narrow absorption window drugs, a gastrosphere system comprising two mechanisms
of gastric retention, namely buoyancy and gastroadhesion, has been investigated in this study employing poly(lactic-co-glycolic
acid) (PLGA), polyacrylic acid (PAA), alginate, pectin, and a model drug metformin hydrochloride. Fifteen formulations were
obtained using a Box–Behnken statistical design. The gastrosphere yield was above 80% in all cases; however, due to the high
water solubility of metformin, drug entrapment efficacy was between 18% and 54%. Mean dissolution time and gastroadhesive
strength were used as the formulation responses in order to optimize the formulation. Furthermore, the molecular mechanics
force field simulations were performed to corroborate the experimental findings. Drug release profiles revealed three different
release kinetics, namely, burst, first-order and zero-order release. Varying gastroadhesive results were obtained, and were
highly sensitive to changes in polymer concentrations. FTIR revealed that strong bonds of PAA and PLGA were retained within
the gastrosphere. Surface area and porosity analysis provided supporting evidence that the lyophilization process resulted
in a significant increase in the porosity. Analysis of the surface morphology by SEM revealed that air pockets were spread
over the entire surface of the gastrosphere, providing a visual proof of the high porosity and hence low density of the gastrosphere.
The spatial disposition and energetic profile of the sterically constrained and geometrically optimized multi-polymeric complex
of alginate, pectin, PAA, and PLGA corroborated the experimental results in terms of in vitro drug release and gastroadhesive strength of the fabricated gastrospheres. 相似文献
89.
90.
Kenneth G. Hutson David R. Threlfall 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,632(4):630-648
Chloroform-soluble extracts of unpurified chloroplast preparations of lettuce, pea and spinach and of class I lettuce chloroplasts that have been incubated in the light with [methylene-3H]homogentisate contain 3H-labelled plastoquinones-9 and -8 (minor homologue), 2-demethylplastoquinones-9 and -8 (minor homologue), pytylplastoquinone and 2-demethylphytylplastoquinone.. The absence of demethylquinols, the presumed precursors of the dimethylquinones, from the extracts to the fact that no precautions were taken in the extraction procedure to present their oxidation to the corresponding quinones.In unpurified lettuce chloroplasts the synthesis of these compounds from [methylene-3H]homogentisate is Mg2+-dependent and it is stimulated by light. The addition of isopentenyl pyrophosphate to the incubation mixtures increases the amounts of both groups of quinones (polyprenyl quinones and phytyl quinones) synthesised in the light and the amounts of polyprenyl quinones synthesised in the dark. Replacement of isopentenyl pyrophosphate with a source of preformed polyrenyl pyrophosphates brings about a marked rise in the amounts of polyprenyl quinones synthesized. This rise in polyprenyl quinone synthesis is further increased if the chloroplats are subjects to osmotic shock. The presence of S-adenosylmethionine increases the amounts of dimethylquinones synthesized at the expense of the demethylquinones. The implied precursor-product relationships between 2-demethylphytylplastoquinone (quinol?) and phytylplastoquinone and between the 2-demethylplastoquinones (quinols) and plastoquinones were verified in a pulse-labelling experiment. Confirmation that these quinones, or their corresponding quinols, are synthesized. 相似文献