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671.
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673.
The models of complete, quasi and conditional symmetry as well as marginal homogeneity and diagonal asymmetry, applicable to square contingency tables are extended to non-square ones. Several properties of the models are investigated and estimation and test theory is presented. The utility of the new proposed models is discussed and illustrated by reanalyzing classical data sets. 相似文献
674.
675.
Konstantinos PatsialasEmmanouil H. Papaioannou Maria Liakopoulou-Kyriakides 《Carbohydrate polymers》2012,87(2):1112-1118
It has been recently reported that the peptide Ac-Glu-Thr-Lys-Thr-Tyr-Phe-Trp-Lys-NH2, analogue of the Glu1811-Lys1818 region of A3 light chain of blood coagulation factor VIII, presents in vitro significant anticoagulant activity. The encapsulation of this peptide into different polyvinyl alcohol formulations is examined here. The formulations were prepared using polyvinyl alcohol cross-linked with either boric acid or glutaraldehyde, giving a series of twelve different hydrogels. In case of PVA-boric acid method, a small percentage of sodium alginate was used in order to avoid bead's agglomeration. In that case, the most efficient encapsulation of the octapeptide (74%) was achieved with 0.2% (w/w) sodium alginate. It was also observed that the increase in sodium alginate percentage leads to beads with increased peptide release time, ranging from 60 to 90 min at 0.02% and 1% (w/w) sodium alginate respectively. The water holding of the PVA gels was estimated to be 27% regardless of the cross-linking reagent used, while it was increased with increasing sodium alginate concentration and reached about 60% for 1% sodium alginate. The longer octapeptide release, at 120 min, was observed with PVA-glutaraldehyde hydrogel, with encapsulation efficiency comparable to those obtained with boric acid, indicating that this hydrogel may be further used in drug delivery systems. 相似文献
676.
食源性致病菌是引发食物中毒的主要微生物,对人类的健康构成了重要威胁,也逐渐发展为公共卫生、食品工业部门高度重视的一个问题。近年来,因食源性致病菌产生的疾病在世界各地蔓延,其中,大肠杆菌O157∶H7是食源性致病菌种类中造成病死率较高的一种细菌,其感染剂量低、致病性强等特点引起研究人员和世界各国卫生组织的广泛关注。基于此,对大肠杆菌O157∶H7的检测方法及其演变进行了梳理和比较分析,并着重综述了生物传感器(biosensor)在其检测中的应用进展,以期为大肠杆菌O157∶H7快速、准确和可商业化的检测方法的研发提供参考。 相似文献
677.
Due to the increasing prevalence of diabetes, finding therapeutic analogues for insulin has become an urgent issue. While many experimental studies have been performed towards this end, they have limited scope to examine all aspects of the effect of a mutation. Computational studies can help to overcome these limitations, however, relatively few studies that focus on insulin analogues have been performed to date. Here, we present a comprehensive computational study of insulin analogues—three mutant insulins that have been identified with hyperinsulinemia and three mutations on the critical B26 residue that exhibit similar binding affinity to the insulin receptor—using molecular dynamics simulations with the aim of predicting how mutations of insulin affect its activity, dynamics, energetics and conformations. The time evolution of the conformers is studied in long simulations. The probability density function and potential of mean force calculations are performed on each insulin analogue to unravel the effect of mutations on the dynamics and energetics of insulin activation. Our conformational study can decrypt the key features and molecular mechanisms that are responsible for an enhanced or reduced activity of an insulin analogue. We find two key results: 1) hyperinsulinemia may be due to the drastically reduced activity (and binding affinity) of the mutant insulins. 2) Y26BS and Y26BE are promising therapeutic candidates for insulin as they are more active than WT-insulin. The analysis in this work can be readily applied to any set of mutations on insulin to guide development of more effective therapeutic analogues. 相似文献
678.
McCann T. J.; Terranova G.; Keyte J. W.; Papaioannou S. S.; Mason W. T.; Meikle M. C.; McDonald F. 《American journal of physiology. Cell physiology》1998,275(1):C33
Osteoblasts can be activated by their collagen matrix and inparticular the DGEA peptide motif. We have reported that DGEA is ableto activate Ca2+ signalingpathways in the human osteoblast-like cell line, Saos-2, by a tyrosinekinase-dependent pathway (T. J. McCann, W. T. Mason, M. C. Meikle, andF. McDonald. Matrix Biol. 16:271-280, 1997). In the present study, we show that this activityis due to coupling of the signal to intracellularCa2+ stores, since the DGEA actionis not blocked by La3+ but is lostwhen Ca2+ stores are depleted with2 µM and blocked by 10 µM ryanodine. The activated stores alsodiffer functionally from those activated by thrombin, as blockade withU-73122 obstructs only thrombin-activated Ca2+ release. We have shown thatthe DGEA activity was not due to its high-charge density, since the twoacidic residues can be substituted with their uncharged homologues(asparagine and glutamine) without significant loss of activity. Thiswas in turn measured by an adhesion assay that also demonstrated thislevel of specificity. Furthermore, by constructing DGEA bound to FITC,we have shown that DGEA binding was dependent on divalent cations. Wehave also demonstrated that an intact actin cytoskeleton is notrequired for Ca2+ activation byinhibiting actin polymerization with the addition of cytochalasin B. These data strengthen the argument that collagen has a significant rolein regulating osteoblast function via this peptide motif. 相似文献
679.
The circadian system of c-fos deficient mice 总被引:1,自引:0,他引:1
G. I. Honrado Randall S. Johnson D. A. Golombek B. M. Spiegelman V. E. Papaioannou M. R. Ralph 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1996,178(4):563-570
We examined the role of c-fos in the synchronization of circadian rhythms to environmental light cycles using a line of gene-targeted mice carrying a null mutation at this locus. Circadian locomotor rhythms in mutants had similar periods as wild-type controls but took significantly longer than controls to entrain to 12:12 light-dark cycles. Light-induced phase shifts of rhythms in constant dark were attenuated in mutants although the circadian timing of phase delays and advances was not changed. A functional retinohypothalamic projection was indicated from behavioral results and light-induced jun-B expression in the SCN. The results indicate that while c-fos activation is not an absolute requirement for rhythm generation nor photic responses, it is required for normal entrainment of the mammalian biological clock.Abbreviations
SCN
suprachiasmatic nucleus
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RHT
retinohypothalamic tract
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IEG
immediate early genes
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NGF
nerve growth factor
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VIP
vasoactive intestinal polypeptide
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DD
constant darkness
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CT
circadian time 相似文献
680.
Virginia E. Papaioannou Karen Artzt Gerald B. Dooher Dorothea Bennett 《Molecular reproduction and development》1979,2(2):147-151
Mouse chimaeras produced by aggregation of embryos heterozygous for two different recessive mutations at the T/t complex have been analyzed by breeding to explore the basis for the phenomena of male transmission ratio distortion and sterility associated with these genes. Whereas males of genotype tw2/tw5 are always sterile, male chimaeras of the type +/tw2 ? +/tw5 are normally fertile; furthermore, they transmit each t mutation to the same very high extent seen in ordinary (+/t) heterozygotes. Since spermatogenic cells derived from either the +/tw2 and +/tw5 genotypes thus function quite independently of one another in mosaic testes, it can be concluded that sterility, and presumably distorted transmission ratio as well, depends on specific interactions between T/t alleles in diploid spermatogenic cells or their individual meiotic descendants. 相似文献