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91.
92.
Neutron capture therapy (NCT) research encompasses a wide range of preclinical and clinical studies needed to develop this promising but complex cancer treatment. Many specialized facilities and capabilities including thermal and epithermal neutron irradiation facilities, boron analysis, specialized mixed-field dosimetry, animal care facilities and protocols, cell culture laboratories, and, for human clinical studies, licenses and review board approvals are required for NCT research. Such infrastructure is essential, but much of it is not readily available within the community. This is especially true for neutron irradiation facilities, which often require significant development and capital investment too expensive to duplicate at each site performing NCT research. To meet this need, the NCT group at the Massachusetts Institute of Technology (MIT) has established a User Center for NCT researchers that is already being accessed successfully by various groups. This paper describes the facilities, capabilities and other resources available at MIT and how the NCT research community can access them.  相似文献   
93.
Xanthomonas campestris pv. glycines is the causal agent of bacterial pustule disease of soybeans. The objective of this work was to construct a nonpathogenic mutant derived from the pathogenic wild-type strain YR32 and to evaluate its effectiveness in preventing growth of its parent on the soybean phyllosphere. A mini-Tn5-derived transposon was used to generate nonpathogenic mutants. Southern hybridization and pulsed-field gel electrophoresis confirmed the presence of a single transposon in each of the nonpathogenic mutants. One of the nonpathogenic mutants, M715, failed to induce a hypersensitive response in tomato leaves. An ice nucleation gene (inaZ) carried in pJL1703 was introduced into strain YR32 as a reporter gene to demonstrate that the presence of M715 could reduce colonization of the soybean phyllosphere by YR32. de Wit serial replacement analysis showed that M715 competed equally with its wild-type parental strain, YR32. Epiphytic fitness analysis of YR32 in the greenhouse indicated that the population dynamics of strains YR32, YR32(pJL1703), and M715 were similar, although the density of the mutant was slightly less than that of its parent. The M715 mutant was able to survive for 16 days after inoculation on soybean leaves and maintained population densities of approximately 10(4) to 10(5) cells g (fresh weight) of leaf(-1). Therefore, M715 shows promise as an effective biocontrol agent for bacterial pustule disease in soybeans.  相似文献   
94.

Background

Current detection or screening for malaria infection necessitates drawing blood by fingerprick or venipuncture, which poses risks and limitations for repeated measurement. This study presents PCR detection of Plasmodium falciparum in human urine and saliva samples, and illustrates this potential application in genotyping malaria infections.

Methods

Urine and saliva were obtained from 47 thick film positive and 4 negative individuals one day after collection of blood slides and filter paper blood spots. P. falciparum DNA was extracted from blood, urine and saliva, in separate groups, using the Chelex method or Qiagen DNEasy® kit (urine and saliva only). Blood, urine and saliva extracts were subjected to PCR in separate batches. Amplicons from the various sample types were examined for MSP2 polymorphisms and restriction fragment patterns on DHFR amino acid codon 59.

Results and discussion

Malaria infections exhibited primarily low-grade parasite densities, with a geometric mean of 775 asexual parasites/μl. Regularly matching polymorphic MSP2 genotypes were found between the corresponding urine, saliva and peripheral blood amplicons of each individual, with different inter-individual polymorphic genotypes. Amplicon yields were significantly dependent on DNA extraction method, parasite density and primer set (p < 0.001). A Qiagen® kit extraction had more than 2× higher amplicon yield than the Chelex method, for both urine and saliva. Amplicon yields were 1.6 fold higher from saliva than urine. For each unit increase in log parasite density, the probability of amplicon enhanced 1.8 fold. Highest amplicon yields were obtained from the primer set with the shortest PCR product.

Conclusion

P. falciparum infection is detectable by PCR on human urine and saliva samples. Subject to further refinement of extraction technique and amplicon yields, large-scale malaria parasite screening and epidemiological surveys could be possible without the need to collect blood and use of needles or sharps.  相似文献   
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Salinity effects on the cell membranes of four lines of wheat ( Triticum aestivum L.). and two cultivars of barley ( Hordeum vulgare L.), differing in salt resistance were investigated. Plants were grown for 10 days in 1/4-strength Hoagland solution and then for 5 more days in 1/4-strength Hoagland with and without NaCl (100 m M ) or (for Hordeum only) polyethylene glycol (PEG). Permeability to three non-electrolytes (urea, methylurea and ethylurea) of subepidermal cells of leaf sheaths ( Triticum ) and coleoptiles ( Hordeum ) was determined and membrane partiality calculated, a parameter which numerically indicates the degree of lipophilicity of a membrane. Non-electrolyte permeability significantly increased and membrane partiality decreased in the salt sensitive cultivars or lines under salt stress. Neither parameter changed significantly in the salt resistant lines and cultivar in a saline environment. Osmotic stress in Hordeum by PEG 10000 had no significant effect on permeability and thus membrane partiality neither in sensitive nor in resistant cultivars.
The osmotic component of salinity stress did not seem to be a major factor causing injury, rather ion toxicity may be a cause of cell damage. The results indicate differences in the membrane between salt sensitive and salt resistant genotypes. Salt resistance seems to be controlled by genetic factors independent of external salinity levels.  相似文献   
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With contaminated terrestrial sites always being multiple decades old before they first submit to health risk assessments for humans and ecological receptors, there is great opportunity for soils to elicit markedly lesser chemical toxicity than would be expected. Soil aging and weathering foster various physico-chemical processes that reduce the toxic potency or bioavailability of sequestered chemicals. Because only brand new and unadulterated chemicals with seemingly maximum potencies are used in animal dosing that supports toxicity factor derivation, measured chemical concentrations in soil can be misleading, producing exaggerated risk and hazard outcomes. We sought to determine the extent to which toxicity reduction occurs in experimentally amended soils, working with large soil volumes exposed to the unimpeded ambient condition for a calendar year. A broad toxicity testing matrix for two chemicals (i.e., multiple test species, endpoints, effect level concentrations, and soil types), found species’ responses in contaminated soils to be indistinguishable from those in control soil 80% and 98% of the time for the inorganic and organic compounds used, respectively; a case in point was lead with a soil concentration of 11,000 mg/kg. The results suggest that incorporating a toxicity reduction term is an indispensable task when deriving toxicity factors.  相似文献   
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