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Stability and unfolding of mammalian and microbial α-amylases have been intensively investigated. However, there is only limited information available on the structural stability of plant α-amylases, namely of the two isoenzymes from barley AMY1 and AMY2, of the α-amylase from mung bean (Vigna radiata), and of the α-amylase from malted sorghum (Sorghum bicolor). We report here the stability of soyabean α-amylase (GMA), against elevated temperatures and chemical denaturants (GndHCl) by employing circular dichroism and fluorescence spectroscopy. Since it is well-known that calcium ions play a crucial role for enzymatic activity and stability of a-amylases, we performed our studies with calcium bound and calcium free GMA. The thermal unfolding transition temperature decreased from 72°C for calcium saturated samples to 57°C for the case of calcium depleted GMA. Similarly, the GndHCl transition concentration was lowered from 0.70 M for calcium bound GMA to 0.41 M in the absence of calcium. Thermal unfolding of GMA irreversible due to aggregation of the unfolded state. GMA unfolded in 6 M GndHCl shows high degree of reversibility after diluting the unfolded enzyme in native buffer containing 7 M glycerol. Furthermore, the refolded enzyme showed 93% of activity. 相似文献
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Over two billion people, depending largely on staple foods, suffer from deficiencies in protein and some micronutrients such as iron and zinc. Among various approaches to overcome protein and micronutrient deficiencies, biofortification through a combination of conventional and molecular breeding methods is the most feasible, cheapest, and sustainable approach. An interspecific cross was made between the wheat cultivar 'Chinese Spring' and Aegilops kotschyi Boiss. accession 396, which has a threefold higher grain iron and zinc concentrations and about 33% higher protein concentration than wheat cultivars. Recurrent backcrossing and selection for the micronutrient content was performed at each generation. Thirteen derivatives with high grain iron and zinc concentrations and contents, ash and ash micronutrients, and protein were analyzed for alien introgression. Morphological markers, high molecular weight glutenin subunit profiles, anchored wheat microsatellite markers, and GISH showed that addition and substitution of homoeologous groups 1, 2, and 7 chromosomes of Ae. kotschyi possess gene(s) for high grain micronutrients. The addition of 1U/1S had high molecular weight glutenin subunits with higher molecular weight than those of wheat, and the addition of 2S in most of the derivatives also enhanced grain protein content by over 20%. Low grain protein content in a derivative with a 2S-wheat translocation, waxy leaves, and absence of the gdm148 marker strongly suggests that the gene for higher grain protein content on chromosome 2S is orthologous to the grain protein QTL on the short arm of group 2 chromosomes. 相似文献
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Ravindra Pal Singh Vishal Gupta Puja Kumari Manoj Kumar C. R. K. Reddy Kamalesh Prasad Bhavanath Jha 《Journal of applied phycology》2011,23(4):755-762
The extracellular enzyme alginate lyase produced from marine fungus Aspergillus oryzae isolated from brown alga Dictyota dichotoma was purified, partially characterized, and evaluated for its sodium alginate depolymerization abilities. The enzyme characterization
studies have revealed that alginate lyase consisted of two polypeptides with about 45 and 50 kDa each on 10% sodium dodecyl
sulfate polyacrylamide gel electrophoresis and showed 140-fold higher activity than crude enzyme under optimized pH (6.5)
and temperature (35°C) conditions. Zn2+, Mn2+, Cu2+, Mg2+, Co2+ and NaCl were found to enhance the enzyme activity while (Ca2+, Cd2+, Fe2+, Hg2+, Sr2+, Ni2+), glutathione, and metal chelators (ethylenediaminetetraacetic acid and ethylene glycol tetraacetic acid) suppressed the
activity. Fourier transform infrared and thin-layer chromatography analysis of depolymerized sodium alginate indicated the
enzyme specificity for cleaving at the β-1,4 glycosidic bond between polyM and polyG blocks of sodium alginate and therefore
resulted in estimation of relatively higher polyM content than polyG. Comparison of chemical shifts in 13C nuclear magnetic resonance spectra of both polyM and polyG from that of sodium alginate also showed further evidence for
enzymatic depolymerization of sodium alginate. 相似文献
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Infant facial features are thought to be powerful elicitors of caregiving behaviour. It has been widely assumed that men and women respond in different ways to those features, such as a large forehead and eyes and round protruding cheeks, colloquially described as 'cute'. We investigated experimentally potential differences using measures of both conscious appraisal ('liking') and behavioural responsivity ('wanting') to real world infant and adult faces in 71 non-parents. Overall, women gave significantly higher 'liking' ratings for infant faces (but not adult faces) compared to men. However, this difference was not seen in the 'wanting' task, where we measured the willingness of men and women to key-press to increase or decrease viewing duration of an infant face. Further analysis of sensitivity to cuteness, categorising infants by degree of infantile features, revealed that both men and women showed a graded significant increase in both positive attractiveness ratings and viewing times to the 'cutest' infants. We suggest that infant faces may have similar motivational salience to men and women, despite gender idiosyncrasies in their conscious appraisal. 相似文献
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Gap junctions serve as intercellular conduits that allow the exchange of small molecular weight molecules (up to 1 kDa) including ions, metabolic precursors and second messengers. Microglia are capable of recognizing peptidoglycan (PGN) derived from the outer cell wall of Staphylococcus aureus, a prevalent CNS pathogen, and respond with the robust elaboration of numerous pro-inflammatory mediators. Based on recent reports demonstrating the ability of tumor necrosis factor-alpha and interferon-gamma to induce gap junction coupling in macrophages and microglia, it is possible that pro-inflammatory mediators released from PGN-activated microglia are capable of inducing microglial gap junction communication. In this study, we examined the effects of S. aureus-derived PGN on Cx43, the major connexin in microglial gap junction channels, and functional gap junction communication using single-cell microinjections of Lucifer yellow (LY). Exposure of primary mouse microglia to PGN led to a significant increase in Cx43 mRNA and protein expression. LY microinjection studies revealed that PGN-treated microglia were functionally coupled via gap junctions, the specificity of which was confirmed by the reversal of activation-induced dye coupling by the gap junction blocker 18-alpha-glycyrrhetinic acid. In contrast to PGN-activated microglia, unstimulated cells consistently failed to exhibit LY dye coupling. These results indicate that PGN stimulation can induce the formation of a functional microglial syncytium, suggesting that these cells may be capable of influencing neuro-inflammatory responses in the context of CNS bacterial infections through gap junction intercellular communication. 相似文献