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61.
K. Indira Priyadarsini Matthew A. Naylor Michael R. L. Stratford Peter Wardman 《Free radical research》1996,25(2):99-107
The bifunctional hypoxia-specific cytotoxin RB90745, has a nitroimidazole moiety attached to an imidazo[1,2,-a]quinoxaline mono-N-oxide with a spacer/linking group. The reduction chemistry of the drug was studied by pulse radiolysis using the one electron reductant CO2˙-. As N-oxides and nitro compounds react with CO2˙- at diffusion controlled rates, initial reaction produced a mixture of the nitro radical (λmax 410 nm) and the N-oxide radical (λmax 550 nm) in a few microseconds. Subsequently an intramolecular electron transfer (IET) was observed (k = 1.0 ± 0.25 × 103 s-1 at pH 5-9), from the N-oxide to the more electron-affinic nitro group. This was confirmed by the first order decay rate of the radical at 550 nm and formation at 410 nm, which was independent of both the concentration of the parent compound and the radicals. The rates of electron transfer and the decay kinetics of the nitro anion radicals were pH dependent and three different pKaS could be estimated for the one electron reduced species: 5.6 (nitroimidazole group) and 4.3, and 7.6 (N-oxide function). The radicals react with oxygen with rate constants of 3.1 × 107 and 2.8 × 106 dm3 mol-1 s-1 observed at 575 nm and 410 nm respectively. Steady state radiolysis studies indicated four electron stoichiometry for the reduction of the compound. 相似文献
62.
Amrita Ahluwalia Kuppan Gokulan Indira Nath D. Nageswara Rao 《Microbiology and immunology》1997,41(10):779-784
A successful peptide vaccine for AIDS is desired to elicit T-helper and cytotoxic T lymphocyte responses besides neutralizing antibodies. The V3 loop peptide of HIV-1 has been shown to contain the principal neutralizing domain, one of the most immunodominant regions, having both B-cell and T-cell determinants. In this study, the tip of the V3 loop region was mutated from GPGR to GPGQ based on the sequence of Indian isolates (CKRKIHIGPGQAFYT). To further enhance the immunogenicity of this epitope, two delivery systems of immune stimulating complexes (ISCOMs) and liposomes were used to incorporate the peptide. Mice of differing haplotypes, H-2b, H-2d, H-2k and H-2S, showed no MHC restriction when immunized with these formulations. The IgG levels as assessed by ELISA were found to be significantly higher (P<0.05 to P< 0.001) for even five-fold lower doses of the peptide in ISCOMs and liposomes as compared to the conventional alum-based preparation. The major subtype elicited was IgG2a/IgG2b, suggestive of a Th1-like response for all the formulations. Thus, it would appear that the same peptide incorporated in ISCOMs and liposomes selects a Th1 response and may therefore be important not only for neutralization but also for virus clearance. 相似文献
63.
Patrick L. Healey Indira J. Mehta Karin E. Westerling 《American journal of botany》1986,73(8):1093-1099
Guayule (Parthenium argentatum), a native shrub of the Chihuahuan desert, contains rubber. Guayule has been crossed with other Parthenium species in an attempt to improve its agronomic characteristics. The resulting hybrids show intermediate morphologies. Each Parthenium species has a characteristic combination of leaf trichomes. In order to recognize the contribution of each parent in future studies of hybrids, characteristics of leaf trichomes of the following Parthenium species were studied: P. tomentosum, P. fruticosum, P. Schottii and P. rollinsianum. All species studied had two or more types of trichomes, and, in some species, trichomes of upper and lower epidermal surfaces were different. The prominent trichomes on upper epidermis of P. tomentosum and P. fruticosum were simple, uniseriate, conical trichomes, which also were observed on both epidermal surfaces of P. Schottii. Extremely long, narrow, simple, whiplike, trichomes formed a dense cover on both surfaces of P. rollinsianum and on the lower surfaces of P. tomentosum and P. fruticosum. Simple, uniseriate, cylindrical trichomes, and biseriate, glandular trichomes were observed in all four species. 相似文献
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Summary An important development in the field of plant cell and tissue culture has been the demonstration in the past decade of the
totipotency of higher plant cells. Isolated single cells were first successfully grown on a nurse tissue separated by a filter
paper and gave rise to a callus tissue. Later, completely isolated single cells of tobacco were grown in microchambers to
form small clumps of cells which then could be differentiated to form adult tobacco plants. Indirect evidence of the totipotency
of higher plant cells has also been provided in a number of other plants. Embryo-like structures (or embryoids) or whole plants,
or both, have been obtained from such highly differentiated cells as the pollen grains (gametic and haploid), photosynthetic
palisade cells in leaves, epidermal cells from the hypocytyl, and the triploid endosperm cells; all of these cell types perform
very highly specialized functions in the plant. Plant protoplasts (cell wall is digested with enzymes) have also been cultured
to give rise to normal adult plants. In many instances embryoids have been produced in vitro from several species of flowering
plants which do not show such asexual activity in nature. These embryoids are normally indistinguishable morphologically from
embryos produced by gametic fusion, often follow the same pattern of cell divisions and differentiation as the developing
zygote, and are economically important as they provide clonal populations. Early work in this area emphasized the necessity
of dissociating tissues into single cells and providing a nutritional environment identical to that of the zygote in the embryo
sac (usually by supplementing the medium with liquid endosperm from coconuts), before the cells could be released morphogenetically
to express their totipotency by forming embryoids. Much of the recent work, however, has shown that perfect development of
embryoids can be obtained in completely synthetic media in callus tissues as well as in suspension cultures.
This paper is dedicated to the memory of the late Professor Philip R. White, a dear friend who provided much counsel and inspiration
to us both. for his pioneering work, valuable contributions and untiring efforts in developing the science of plant cell,
tissue, and organ culture.
Florida Agricultural Experiment Stations Journal Series No. 4699.
Presented in the Symposium on Functional Differentiated Systems at the 23rd Annual Meeting of the Tissue Culture Association,
Los Angeles, California, June 5–8, 1972. 相似文献
66.
Intraperitoneal administration of citrulline (30 mg/kg body weight) for three days to rats brought about an increase in the activity of hepatic ornithine-aminotransferase without any change in glutamine-synthetase activity. In the brain of the same animals, the activity of the glutamine synthetase in cerebellum and brain stem increased significantly. In cerebral hemispheres the activity of ornithine aminotransferase was increased without a change in glutamine-synthetase activity. Under these conditions, there is a rise in the content of glutamine, citrulline, arginine and ornithine in all the three regions of the brain. 相似文献
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