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51.
L-Lactate dehydrogenase (L-LDH, E.C. 1.1.1.27) is encoded by two or three
loci in all vertebrates examined, with the exception of lampreys, which
have a single LDH locus. Biochemical characterizations of LDH proteins have
suggested that a gene duplication early in vertebrate evolution gave rise
to Ldh-A and Ldh-B and that an additional locus, Ldh-C arose in a number of
lineages more recently. Although some phylogenetic studies of LDH protein
sequences have supported this pattern of gene duplication, others have
contradicted it. In particular, a number of studies have suggested that
Ldh-C represents the earliest divergence among vertebrate LDHs and that it
may have diverged from the other loci well before the origin of
vertebrates. Such hypotheses make explicit statements about the
relationship of vertebrate and invertebrate LDHs, but to date, no closely
related invertebrate LDH sequences have been available for comparison. We
have attempted to provide further data on the timing of gene duplications
leading to multiple vertebrate LDHs by determining the cDNA sequence of the
LDH of the tunicate Styela plicata. Phylogenetic analyses of this and other
LDH sequences provide strong support for the duplications giving rise to
multiple vertebrate LDHs having occurred after vertebrates diverged from
tunicates. The timing of these LDH duplications is consistent with data
from a number of other gene families suggesting widespread gene duplication
near the origin of vertebrates. With respect to the relationships among
vertebrate LDHs, our data are not consistent with previous claims that
Ldh-C represented the earliest divergence. However, the precise
relationships among some of the main lineages of vertebrate LDHs were not
resolved in our analyses.
相似文献
52.
A flux analysis of glucose metabolism in the filamentous fungus Rhizopus oryzae was achieved using a specific radioactivity curve-matching program, TFLUX. Glycolytic and tricarboxylic acid cycle intermediates labeled through the addition of extracellular [U-14C]glucose were isolated and purified for specific radioactivity determinations. This information, together with pool sizes and the rates of glucose utilization and end product production, provided input for flux maps of the metabolic network under two different experimental conditions. Based upon the flux analysis of this system, a mutant of R. oryzae with higher lactate and lower ethanol yields than the parent was sought for and found. 相似文献
53.
The rate constants for the reaction of aquocobalamin with thiourea were measured as a function of ionic strength, pH and solvent composition in dioxane-water and acetonitrile-water mixtures. With the help of solubility measurements a complete quantitative analysis of solvent effects on the reaction profile could be made. The transfer Gibbs energy of the initial state strongly depends on solvent composition. Because the transition state and the final state closely follow the initial state, this is not reflected in the rate constants.For the acetonitrile-water mixtures the transfer enthalpy and transfer entropy were determined and were found to exhibit the familiar compensation effect.It is concluded that, when the solvent changes, vitamin B12 creates its own micro-environment around the active metal site, so that the reactivity is effectively solvent independent. The mechanism of activation is dissociative. 相似文献
54.
55.
Omar JM Hamza Mecky IN Matee Mainen J Moshi Elison NM Simon Ferdinand Mugusi Frans HM Mikx Wim H van Palenstein Helderman Antonius JMM Rijs André JAM van der Ven Paul E Verweij 《BMC microbiology》2008,8(1):135
Background
In Tanzania, little is known on the species distribution and antifungal susceptibility profiles of yeast isolates from HIV-infected patients with primary and recurrent oropharyngeal candidiasis. 相似文献56.
57.
Deborah M. Buehler Anita Koolhaas Thomas J. Van’t Hof Ingrid Schwabl Anne Dekinga Theunis Piersma B. Irene Tieleman 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2009,195(5):445-451
The winter immunoenhancement hypothesis associates long nights and increased exposure to melatonin with enhanced immune function
in winter when resource availability is low and the chances of becoming ill are high. Thus, increased exposure to melatonin
in the winter could be adaptive for species facing difficult winter conditions. This idea has found some support in studies
of resident mammals. In birds, the link between day length and melatonin over the annual cycle is weaker, and contributions
of melatonin to seasonal timing are unclear. Furthermore, many species, especially migrants, do not experience the most difficult
conditions of their annual cycle in winter. In this study, we tested whether the winter immunoenhancement hypothesis holds
in an avian species, the red knot Calidris canutus. We found that melatonin duration and amplitude varied significantly over the annual cycle with the highest values occurring
in winter. However, peaks did not correspond to the winter solstice or with annual variation in immune function. Our findings
do not support the winter immunoenhancement hypothesis in knots and question whether the idea that immune function should
be bolstered in winter can be generalized to systems where winter is not the most difficult time of the year. 相似文献
58.
There is a need for safe medications that can effectively support recovery by treating symptoms of protracted abstinence that may precipitate relapse in alcoholics, e.g. craving and disturbances in sleep and mood. This proof-of-concept study reports on the effectiveness of gabapentin 1200 mg for attenuating these symptoms in a non-treatment-seeking sample of cue-reactive, alcohol-dependent individuals. Subjects were 33 paid volunteers with current Diagnostic and Statistical Manual of Mental Disorders-IV alcohol dependence and a strength of craving rating 1 SD or greater for alcohol than water cues. Subjects were randomly assigned to gabapentin or placebo for 1 week and then participated in a within-subjects trial where each was exposed to standardized sets of pleasant, neutral and unpleasant visual stimuli followed by alcohol or water cues. Gabapentin was associated with significantly greater reductions than placebo on several measures of subjective craving for alcohol as well as for affectively evoked craving. Gabapentin was also associated with significant improvement on several measures of sleep quality. Side effects were minimal, and gabapentin effects were not found to resemble any major classes of abused drugs. Results suggest that gabapentin may be effective for treating the protracted abstinence phase in alcohol dependence and that a randomized clinical trial would be an appropriate next step. The study also suggests the value of cue-reactivity studies as proof-of-concept screens for potential antirelapse drugs. 相似文献
59.
60.
Martijn F Schenk Jan HG Cordewener Antoine HP America Wendy PC van't Westende Marinus JM Smulders Luud JWJ Gilissen 《BMC plant biology》2009,9(1):24