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11.
Localization and Properties of Enzymes Involved with Electron Transport Activity in Mycobacteria 总被引:2,自引:0,他引:2 下载免费PDF全文
A study of the subcellular localization of the nicotinamide adenine dinucleotide (NADH)-3-(4, 3-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) oxido-reductase systems in Mycobacterium was presented. Evidence based on starch gel electrophoresis and different responses of the subcellular fractions to heat inactivation suggested the existence of more than one enzyme responsible for the NADH-MTT oxido-reductase activity. One type of activity was found in the membrane-mesosome fraction which contained labile and electrophoretically non-migrating enzymes. Another type of activity was also detected in the soluble fraction which on starch gel electrophoresis exhibited 4 bands of activity, two of which showed heat resistance. 相似文献
12.
Nanko S. Sasaki T. Fukuda R. Hattori M. Dai X. Y. Kazamatsuri H. Kuwata S. Juji T. Gill M. 《Human genetics》1993,92(4):336-338
A study of the genetic association between schizophrenia and aBalI polymorphism in exon 1 of the dopamine D3 (DRD3) gene, a candidate gene for schizophrenia, was conducted. The polymorphism was examined in 91 patients whose symptoms satisfied DSM-III-R for schizophrenia and 90 controls. There were no significant differences between the groups in allele frequencies or genotype counts. Contrary to a previous report, the patients were no more likely to be homozygous than controls. Moreover, no association with the presence of illness could be demonstrated when the patients were grouped according to sex, age of onset, history of admission to psychiatric institutions or positive family history. 相似文献
13.
Carotenogenic mutants ofPhycomyces, which accumulate excess β-carotene or its intermediates, always failed in zygospore development. No improvement occurred
when such mutants were mated together with a helper wild type of the same mating type against the wild type of the opposite
mating type. Addition of excess synthesized pheromone, trisporin B, also failed to improve the zygospore development, though
the mating response was significantly activated in the early stages and abundant zygophores were formed. Exceptional acceleration
of the zygospore development under these experimental conditions occurred in a regulatory albino mutant (carA), which does not accumulate excess intermediate carotenoids. Chemically- or genetically-induced ovarproduction of β-carotene
or lycopene also inhibited the zygospore development. These results imply that the zygospore development ofPhycomyces is maximal when the intracellular amount of β-carotene is optimal (=wild type), and that pheromones act mainly in the early
stages of mating, while other factors such as the cell-to-cell recognition system may also be involved in the later stages.
Intracellular accumulation of excess β-carotene or its intermediates probably disturb such later-stage factors. 相似文献
14.
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To understand the incompatibility between two related plasmids, both of which replicate in an autonomous state under a common control mechanism, we have developed a model that assumes a random choice mechanism for replication of plasmid copies and their random assortment into daughter cells upon cell division. Segregation kinetics by this model is analyzed mathematically and the number of generations required for segregation is calculated as a function of plasmid copy number per cell. The results obtained offer enough quantitative data to make our model reasonably realistic. 相似文献
16.
Tamotsu Kusano 《Population Ecology》1982,24(2):329-344
The postmetamorphic growth and survival of the salamander Hynobius nebulosus tokyoentisTago were surveyed in the study site located in Habu village of Hinodemachi, a suburb of Tokyo City, during 1975–1981. A laboratory experiment on the growth rate of juveniles was conducted in parallel with the field survey. The result indicated that this salamander grew at the rate of 8,mm in s.v.l. per year during the juvenile stage, but its growth rate decreased markedly as low as 1.8 mm for males and 1.1 mm for females, once it had attained sexual maturity. According to the “capture-recapture” procedure the annual survival rate after metamorphosis was found to be quite high; that is, approximately 0.7. By using the growth rate of juveniles and the difference between the sizes at metamorphosis and sexual maturity, the age at first reproduction was estimated to be 4 year for males and 5 year for females. From the data obtained in this study, the intrinsic rates of increase (r) were calculated for various values of age at first reproduction under different survival schedules, and the relationship between the age at first reproduction and fitness as measured by r was examined. The result indicated that an optimal age maximizing fitness always existed under respective survival schedules, and the observed age at first reproduction of this salamandei was found to coincide well with the predicted optimal age. 相似文献
17.
Hemicelluloses were isolated from pineapple-leaf fibers under different conditions. Study of the properties of these hemicelluloses gave direct evidence of some ester linkages between the hemicellulose and the lignin in this fiber. An aldobiouronic acid was isolated from this fiber hemicellulose, and characterized as 2-O-(4-O-methyl-α-d-glucopyranosyluronic acid)-d-xylose. This indicates that the general nature of the hemicellulose is similar to those of jute and other fiber hemicelluloses. 相似文献
18.
Cold adaptation in the phytopathogenic fungi causing snow molds 总被引:1,自引:0,他引:1
Snow molds are psychrophilic or psychrotrophic fungal pathogens of forage crops, winter cereals, and conifer seedlings. These
fungi can grow and attack dormant plants at low temperatures under snow cover. In this review, we describe the biodiversity
and physiological and biochemical characteristics of snow molds that belong to various taxa. Cold tolerance is one of the
important factors related to their geographic distribution, because snow molds develop mycelia under snow cover and because
they should produce intra- and extracellular enzymes active at low temperatures for growth and infection. Basidiomycetous
snow molds produce extracellular antifreeze proteins. Their physiological significance is to keep the extracellular environment
unfrozen. The psychrophilic ascomycete Sclerotia borealis shows normal mycelial growth under frozen conditions, which is faster than that on unfrozen media at optimal growth temperature.
This fungus does not produce extracellular antifreeze proteins, but osmotic stress tolerance enables the fungus to grow at
subzero temperatures. In conclusion, different taxa of snow molds have different strategies to adapt under snow cover. 相似文献
19.
Effects of ligand binding on the stability of aldo–keto reductases: Implications for stabilizer or destabilizer chaperones 下载免费PDF全文
Aurangazeb Kabir Ryo P. Honda Yuji O. Kamatari Satoshi Endo Mayuko Fukuoka Kazuo Kuwata 《Protein science : a publication of the Protein Society》2016,25(12):2132-2141
Ligands such as enzyme inhibitors stabilize the native conformation of a protein upon binding to the native state, but some compounds destabilize the native conformation upon binding to the non‐native state. The former ligands are termed “stabilizer chaperones” and the latter ones “destabilizer chaperones.” Because the stabilization effects are essential for the medical chaperone (MC) hypothesis, here we have formulated a thermodynamic system consisting of a ligand and a protein in its native‐ and non‐native state. Using the differential scanning fluorimetry and the circular dichroism varying the urea concentration and temperature, we found that when the coenzyme NADP+ was absent, inhibitors such as isolithocholic acid stabilized the aldo–keto reductase AKR1A1 upon binding, which showed actually the three‐state folding, but destabilized AKR1B10. In contrast, in the presence of NADP+, they destabilized AKR1A1 and stabilized AKR1B10. To explain these phenomena, we decomposed the free energy of stabilization (ΔΔG) into its enthalpy (ΔΔH) and entropy (ΔΔS) components. Then we found that in a relatively unstable protein showing the three‐state folding, native conformation was stabilized by the negative ΔΔH in association with the negative ΔΔS, suggesting that the stabilizer chaperon decreases the conformational fluctuation of the target protein or increase its hydration. However, in other cases, ΔΔG was essentially determined by the delicate balance between ΔΔH and ΔΔS. The proposed thermodynamic formalism is applicable to the system including multiple ligands with allosteric interactions. These findings would promote the development of screening strategies for MCs to regulate the target conformations. 相似文献
20.