全文获取类型
收费全文 | 433篇 |
免费 | 37篇 |
国内免费 | 1篇 |
出版年
2022年 | 6篇 |
2021年 | 19篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 8篇 |
2015年 | 15篇 |
2014年 | 17篇 |
2013年 | 24篇 |
2012年 | 28篇 |
2011年 | 37篇 |
2010年 | 12篇 |
2009年 | 12篇 |
2008年 | 17篇 |
2007年 | 16篇 |
2006年 | 22篇 |
2005年 | 24篇 |
2004年 | 14篇 |
2003年 | 23篇 |
2002年 | 10篇 |
1999年 | 3篇 |
1998年 | 6篇 |
1996年 | 6篇 |
1994年 | 3篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1984年 | 6篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1967年 | 4篇 |
1963年 | 2篇 |
1961年 | 3篇 |
1960年 | 2篇 |
1956年 | 2篇 |
1950年 | 2篇 |
1948年 | 2篇 |
1941年 | 3篇 |
1932年 | 2篇 |
1931年 | 3篇 |
1930年 | 2篇 |
1929年 | 2篇 |
1927年 | 3篇 |
排序方式: 共有471条查询结果,搜索用时 312 毫秒
461.
STUDIES ON NUCLEIC ACID METACHROMASY : I. The Effect of Certain Fixatives on the Dye Stacking Properties of Nucleic Acids in Solution 总被引:3,自引:2,他引:1
The stacking coefficients (K's) of nucleic acids have been thought to influence the color contrast between DNA and RNA in tissue sections stained with metachromatic dyes. This idea was tested by titrating toluidine blue (TB) and acridine orange (AO) in solution against DNA and RNA, native or treated with formaldehyde, acrolein, or Carnoy's fluid. Absorption spectra at varying polymer-dye ratios were used to compute K values by the methods of Bradley and colleagues. Results with both dyes fit Bradley's stacking equations. Fixatives did not block dye-binding sites but markedly altered K values. K of DNA was low, unaffected by aldehyde fixative, increased by Carnoy's fluid or heat denaturation. K of RNA was higher than that of DNA and was increased greatly by formaldehyde, almost as much by acrolein, considerably less by Carnoy's fluid. Aldehyde effects were partially reversed upon removal of aldehyde by dialysis. These observations accord with known effects of aldehydes and denaturation upon nucleic acid conformation. Differences between K's of DNA and RNA were greater after aldehyde treatment than after Carnoy's, and were greater with AO than with TB. This is generally consistent with the magnitude of the color contrasts observed in tissues. Additional factors must contribute to the intense color contrast observed in acrolein-fixed tissues stained with TB. 相似文献
462.
463.
464.
465.
466.
467.
Navdeep Grover Marc P. Douaisi Indrakant V. Borkar Lillian Lee Cerasela Zoica Dinu Ravi S. Kane Jonathan S. Dordick 《Applied microbiology and biotechnology》2013,97(19):8813-8821
AcT (perhydrolase) containing paint composites were prepared leading to broad-spectrum decontamination. AcT was immobilized onto multi-walled carbon nanotubes (MWNTs) and then incorporated into latex-based paints to form catalytic coatings. These AcT-based paint composites showed a 6-log reduction in the viability of spores of Bacillus cereus and Bacillus anthracis (Sterne) within 60 min. The paint composites also showed >4-log reduction in the titer of influenza virus (X-31) within 10 min (initially challenged with 107 PFU/mL). AcT-based paint composites were also tested using various perhydrolase acyl donor substrates, including propylene glycol diacetate (PGD), glyceryl triacetate, and ethyl acetate, with PGD observed to be the best among the substrates tested for generation of peracetic acid and killing of bacillus spores. The operational stability of paint composites was also studied at different relative humidities and temperatures to simulate real-life operation. 相似文献
468.
Andersom Milech Einhardt Sandro Ferreira Lillian Mathias Oliveira Dimas Mendes Ribeiro Fabrício Ávila Rodrigues 《Physiologia plantarum》2020,170(4):592-606
Nickel (Ni) and glyphosate (Gl) are able to reduce the symptoms of Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, in soybean. However, their combined effects on the energy balance and ethylene metabolism of soybean plants infected with this fungus has not been elucidated. Therefore, the effects of Ni, Gl, and the combination of Ni + Gl on ASR development, photosynthetic capacity, sugar concentrations, and ethylene concentrations in plants of a Gl-resistant cultivar, uninfected or infected with P. pachyrhizi, were investigated. Inoculated plants supplied with Ni had the highest foliar Ni concentration in all the treatments. Gl had a negative effect on the foliar Ni concentration in Ni-sprayed plants. The ASR severity was reduced in plants sprayed with Ni and Gl. Carotenoid and chlorophyll concentrations were higher in inoculated Ni, Gl, and Ni + Gl plants than in control plants. Based on the chlorophyll a fluorescence parameters, the photosynthetic apparatus of the control inoculated plants was damaged, and the least amount of energy was directed to the photochemistry process in these plants. The reduced capacity of the photosynthetic mechanism to capture light and use the energy absorbed by photosystem II in inoculated plants was reflected in their reduced capacity to process CO2, as indicated by the high internal CO2 concentrations and low rates of net carbon assimilation. The low sugar concentrations in inoculated plants from the control treatment were linked to their reduced photosynthetic capacity due to the high ASR severity. In uninfected plants, the ethylene concentration was not affected by Ni or Gl, while the ethylene concentration decreased in inoculated plants; this decrease was more pronounced in plants from the control treatment than in treated inoculated plants. In conclusion, this study sheds light on the role played by both Ni and Gl in ASR control from a physiological perspective. Soybean plants exposed to Ni and Gl were able to maintain high ethylene concentrations and photosynthetic capacity during the P. pachyrhizi infection process; as a result, these plants consumed less of their reserves than inoculated plants not treated with Ni or Gl. 相似文献
469.
Deborah J. Briggs Jean S. Smith Francis L. Mueller James Schwenke Rolan D. Davis Chandra R. Gordon Kristen Schweitzer Lillian A. Orciari Pamela A. Yager Charles E. Rupprecht 《Biologicals》1998,26(4):347-355
Levels of rabies virus neutralizing antibody in sera from dogs and cats were titrated to endpoint by the Rapid Fluorescent Focus Inhibition Test (RFFIT) and retested by the RFFIT and the Fluorescent Antibody Virus Neutralization test (FAVN). The two tests were compared for their ability to detect the 0.5 international units/ml (I.U.) of antibody required by the World Health Organization and the Office International des Epizooties as the minimum response for proof of rabies immunization. No difference was observed in sensitivity or specificity for either method in tests of 168 sera from unvaccinated animals or 70 sera from vaccinated animals with high levels of neutralizing antibody (an initial RFFIT titre of > or = 1.0 I.U.). Test to test variation occurred for results obtained by both RFFIT and FAVN for 95 sera from vaccinated animals with low to moderate levels of neutralizing antibody (RFFIT titre < 1.0 I.U.). No significant differences were detected for the 95 sera in the frequency for one methodology more often than the other to have a positive response (> or = 0.5 I.U.), nor were significant differences detected for the symmetry (P = 0.43) or the marginal homogeneity (P = 0.39) of results obtained by the two methods. Both methods can adequately identity unvaccinated animals, but false positive and false negative results are possible for either method when a single test is used to measure the antibody response of low-responding vaccinated animals. Nucleotide sequence analysis identified several amino acid differences in stocks of the challenge rabies virus from different laboratories. The small differences in neutralizing antibody titre that may result from mutations in the challenge virus are not important for evaluating immunity induced by vaccines which are themselves prepared from a variety of different rabies virus strains, but differences in the challenge virus, rather than differences in methodology, may account for at least some of the discrepant results reported in inter-laboratory surveys. Comparative studies of serological methods for measuring rabies antibodies should use well-characterized unpassaged virus stocks obtained from a single reference laboratory. 相似文献
470.
The concentration of p-tyramine in the rat striatum was increased significantly by intraperitoneal injection of phenelzine (5 or 100 mg/kg). Unlike other monoamine oxidase (MAO) inhibitors, phenelzine had no effect on p-tyramine levels in the first 1-2 h following injection. The high dose of phenelzine increased the p-tyramine levels much more than the low dose. In addition, the high dose of phenelzine increased striatal p-tyrosine levels significantly 12 h after injection. Further studies showed that phenelzine inhibited the tyrosine aminotransferase activity of rat liver homogenates; the IC50 was 50 microM. Phenelzine also inhibited the aromatic L-amino acid decarboxylase activity of rat brain homogenate with an IC50 of 25 microM. Following intraperitoneal injection of 100 mg/kg phenelzine, the initial concentration of phenelzine in the striatum appears to be high enough to inhibit aromatic L-amino acid decarboxylase. It is suggested that the multiple enzyme inhibition caused by administration of high doses of phenelzine accounts for its unusual effects on striatal p-tyramine levels compared with other MAO inhibitors, i.e., its initial lack of effect on p-tyramine levels followed later by very large increases in p-tyramine levels. 相似文献