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111.
Bradley RD; Adkins RM; Honeycutt RL; McDonald JH 《Molecular biology and evolution》1998,15(6):709-717
Using the strictly neutral model as a null hypothesis, we tested for
deviations from expected levels of nucleotide polymorphism at the alcohol
dehydrogenase locus (Adh-1) within and among four species of pocket gophers
(Geomys bursarius major, G. knoxjonesi, G. texensis llanensis, and G.
attwateri). The complete protein-encoding region was examined, and 10
unique alleles, representing both electromorphic and cryptic alleles, were
used to test hypotheses (e.g., the neutral model) concerning the
maintenance of genetic variation. Nineteen variable sites were identified
among the 10 alleles examined, including 9 segregating sites occurring in
synonymous positions and 10 that were nonsynonymous. Several statistical
methods, including those that test for within-species variation as well as
those that examine variation within and among species, failed to reject the
null hypothesis that variation (both within and between species of Geomys)
at the Adh locus is consistent with the neutral theory. However, there was
significant heterogeneity in the ratio of polymorphism to divergence across
the gene, with polymorphisms clustered in the first half of the coding
region and fixed differences clustered in the second half of the gene. Two
alternative hypotheses are discussed as possible explanations for this
heterogeneity: an old balanced polymorphism in the first half of the gene
or a recent selective sweep in the second half of the gene.
相似文献
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Erik JM Toonen Pilar Barrera Jaap Fransen Arjan PM de Brouwer Agnes M Eijsbouts Pierre Miossec Hubert Marotte Hans Scheffer Piet LCM van Riel Barbara Franke Marieke JH Coenen 《Arthritis research & therapy》2012,14(6):R264
Introduction
The goal of this study is to investigate whether the -308G > A promoter polymorphism in the tumor necrosis factor alpha (TNFA) gene is associated with disease severity and radiologic joint damage in a large cohort of patients with rheumatoid arthritis (RA).Methods
A long-term observational early RA inception cohort (n = 208) with detailed information about disease activity and radiologic damage after 3, 6 and 9 years of disease was genotyped for the TNFA -308G > A promoter polymorphism (rs1800629). A longitudinal regression analysis was performed to assess the effect of genotype on RA disease severity and joint damage. Subsequently, a meta-analysis, including all publically available data, was performed to further test the association between joint erosions and the TNFA polymorphism. To learn more about the mechanism behind the effect of the polymorphism, RNA isolated from peripheral blood from RA patients (n = 66) was used for TNFA gene expression analysis by quantitative PCR.Results
Longitudinal regression analysis with correction for gender and disease activity showed a significant difference in total joint damage between GG and GA+AA genotype groups (P = 0.002), which was stable over time. The meta-analysis, which included 2,053 patients, confirmed an association of the genetic variant with the development of erosions (odds ratio 0.78, 95% CI 0.62, 0.98). No significant differences in TNFA gene expression were observed for the different genotypes, confirming earlier findings in healthy individuals.Conclusions
Our data confirm that the TNFA -308G > A promoter polymorphism is associated with joint damage in patients with RA. This is not mediated by differences in TNFA gene expression between genotypes. 相似文献114.
SYNOPSIS. The glucose transport system in Leishmania tropica promastigotes was characterized by the use of labeled 2-deoxy-D-glucose (2-DOG), a nonmetabolizable glucose analog. The uptake system has a Q10 of 2 and a heat of activation of 10.2 kcal/mole. The glucose transport system is subject to competitive inhibition by 2-DOG, glucosamine, N-acetyl glucosamine, mannose, galactose, and fructose which suggests that substitutions in the hexose chain at carbons 2 and 4 do not affect carrier specificity. In contrast, changes at carbon 1 (α-methyl-D-glucoside, 1,5-anhydroglucitol) and carbon 3 (3–0-methyl glucose) lead to loss of carrier affinity since these sugars do not compete for the glucose carrier. Sugars that compete with the glucose carrier have one common feature—they all exist in the pyranose form in solution. The carrier for D-glucose does not interact with L-glucose or any of the pentose sugars tested. Uptake of 2-DOG is inhibited by glycerol. This inhibition, however, is noncompetitive; it is evident, therefore, that glucose and glycerol do not compete for the same carrier. Glycerol does not repress the glucose carrier since cells grown in presence of glycerol transport the sugar normally. 相似文献
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Abstract: We present the first record of the cardiid genus Monodacna from the Pliocene of Anatolia, Turkey. Monodacna imrei sp. nov. was found in the Pliocene Killik Formation from the western margin of the Baklan Basin, in very marginal brackish to freshwater lacustrine deposits. The new record extends the stratigraphic range of the modern Ponto‐Caspian genus back into the Pliocene and adds to earlier evidence that modern Ponto‐Caspian taxa originated in the Pliocene of south‐western Turkey. 相似文献
120.