首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   45篇
  免费   4篇
  国内免费   3篇
电工技术   1篇
化学工业   20篇
金属工艺   1篇
建筑科学   4篇
能源动力   3篇
轻工业   5篇
冶金工业   9篇
自动化技术   9篇
  2023年   3篇
  2022年   5篇
  2021年   7篇
  2020年   2篇
  2018年   3篇
  2017年   1篇
  2016年   1篇
  2015年   3篇
  2014年   2篇
  2013年   2篇
  2012年   2篇
  2011年   2篇
  2010年   2篇
  2009年   1篇
  2008年   3篇
  2006年   1篇
  2005年   1篇
  2001年   2篇
  1998年   1篇
  1996年   1篇
  1995年   1篇
  1993年   1篇
  1992年   2篇
  1989年   1篇
  1985年   1篇
  1965年   1篇
排序方式: 共有52条查询结果,搜索用时 656 毫秒
1.
Despite the early onset of attention deficit disorder with hyperactivity (ADDH), there is a dearth of treatment studies with preschoolers with this disorder. Forty-six families with ADDH preschoolers were randomly assigned to either an immediate or a delayed group parent training program aimed at improving child compliance. Groups were balanced on demographic variables. Treatment outcome was evaluated by comparing the groups at pre- and posttreatment and 3-month follow-up on measures of parent–child interactions during free play, a compliance task, and parent-supervised activities, as well as on parent-completed Conners Hyperkinesis Index (C. H. Goyette et al; see record 1980-22450-001) scores. Positive treatment effect was obtained on measures of compliance, parental style of interaction, and management skills. These improvements were maintained at 3-month follow-up. Evaluation of treatment effects on nontargeted child behaviors indicated no generalization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
2.
Chiral poly[4,6-bis(alkylthio)-1,3-phenylene-alt-2-methyl-1,3-phenylene] was synthesized from 1,3-dibromo-2,6-bis(3-dodecyl-2-methylthio)benzene and 2-methyl-1,3-phenylenebis(pinacol borate) as a precursor of chiral poly(thiaheterohelicene). Circular dichroism (CD) spectra that arise from the poly(1,3-phenylene) backbone inverted according to the chirality of the side chains, which indicated that a helical conformation of the polymer was induced by the interaction between the side chains. The CD intensity of the polymer increased in non-polar solvents such as hexane. The decrease in the molar CD intensity and the broadening of a fluorescence band at higher concentrations suggested that the aggregation of the polymer suppressed the formation of the helical structure. The conformational changes were monitored by the CD and the 1H NMR spectra at different temperatures. In a good solvent such as dichloromethane, the CD intensity increased, and the 1H NMR signal of benzene protons shifted to lower fields at low temperatures. In hexane, the CD spectra and the 1H NMR signals were less dependent on temperatures, as a result of the strong interaction between the chiral alkyl chains in the polymer to freeze the helical conformation.  相似文献   
3.
Dental implants are widely used and are a predictable treatment in various edentulous cases. Occlusal overload may be causally related to implant bone loss and a loss of integration. Stress concentrations may be diminished using a mechanobiologically integrated implant with bone tissue. The purpose of this study was to investigate the biomechanical behavior, biocompatibility and bioactivity of a Ti-Nb-Sn alloy as a dental implant material. It was compared with cpTi. Cell proliferation and alkaline phosphatase (ALP) activity were quantified. To assess the degree of osseointegration, a push-in test was carried out. Cell proliferation and ALP activity in the cells grown on prepared surfaces were similar for the Ti-Nb-Sn alloy and for cpTi in all the experiments. A comparison between the Ti-Nb-Sn alloy implant and the cpTi implant revealed that no significant difference was apparent for the push-in test values. These results suggest that implants fabricated using Ti-Nb-Sn have a similar biological potential as cpTi and are capable of excellent osseointegration.  相似文献   
4.
Phosphoinositides (PIs) play important roles in the structure and function of the brain. Associations between PIs and the pathophysiology of schizophrenia have been studied. However, the significance of the PI metabolic pathway in the pathology of schizophrenia is unknown. We examined the expression of PI signaling-associated proteins in the postmortem brain of schizophrenia patients. Protein expression levels of phosphatidylinositol 4-phosphate 5-kinase type-1 gamma (PIP5K1C), phosphatidylinositol 4-kinase alpha (PIK4CA, also known as PIK4A), phosphatase and tensin homolog deleted from chromosome 10 (PTEN), protein kinase B (Akt), and glycogen synthase kinase 3β (GSK3β) were measured using enzyme-linked immunosorbent assays and multiplex fluorescent bead-based immunoassays of the prefrontal cortex (PFC) of postmortem samples from 23 schizophrenia patients and 47 normal controls. We also examined the association between PIK4CA expression and its genetic variants in the same brain samples. PIK4CA expression was lower, whereas Akt expression was higher, in the PFC of schizophrenia patients than in that of controls; PIP5K1C, PTEN, and GSK3β expression was not different. No single-nucleotide polymorphism significantly affected protein expression. We identified molecules involved in the pathology of schizophrenia via this lipid metabolic pathway. These results suggest that PIK4CA is involved in the mechanism underlying the pathogenesis of schizophrenia and is a potential novel therapeutic target.  相似文献   
5.
Examined whether preschool children differed on measures of psychosocial functioning both cross-sectionally and longitudinally. 132 children who varied in levels of body fat participated in the study along with their natural parents. Results indicated that the children did not differ in levels of self-esteem and family functioning as a function of their body fat. Prospectively, physical self-esteem weakly (but significantly) correlated with body fat at ages 1 and 2 yrs, and father's perception of family functioning predicted body fat at age 1 yr only. Results suggested that childhood obesity may not develop as a result of psychosocial factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
6.
Examined the effects of behavioral parent training groups on parenting stress and sense of competence. Ss, parents of 91 clinically diagnosed hyperactive preschoolers (aged 3–6 yrs), were randomly assigned to an immediate treatment group (experimental) or a delayed treatment group (control). Results indicate that group parent training yielded benefits beyond changes in parent and child behavior. Compared with controls, experimental Ss reported less parenting stress and increased sense of competence following treatment and 3 mo later. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
7.
Spectroscopic characterization of AgI-ion-mediated C-AgI-A and C-AgI-T base pairs found in primer extension reactions catalyzed by DNA polymerases was conducted. UV melting experiments revealed that C-A and C-T mismatched base pairs in oligodeoxynucleotide duplexes are specifically stabilized by AgI ions in 1:1 stoichiometry in the same manner as a C-C mismatched base pair. Although the stability of the mismatched base pairs in the absence of AgI ions is in the order C-A≈C-T>C-C, the stabilizing effect of AgI ions follows the order C-C>C-A≈C-T. However, the comparative susceptibility of dNTPs to AgI-mediated enzymatic incorporation into the site opposite templating C is dATP>dTTP≫dCTP, as reported. The net charge, as well as the size and/or shape complementarity of the metal-mediated base pairs, or the stabilities of mismatched base pairs in the absence of metal ions, would be more important than the stability of the metallo-base pairs in the replicating reaction catalyzed by DNA polymerases.  相似文献   
8.
9.
This serial research has proposed the hybrid power system combined the wind power unit with the counter-rotating type pump-turbine unit, to provide the constant output for the grid system, even at the suddenly fluctuating/turbulent wind circumstance. In this paper, the tandem impellers prepared for the counter-rotating type pumping unit were operated at the turbine mode, and the performances and the flow conditions were investigated numerically with accompanying the experimental results. Even though providing the pumping unit for the turbine mode, the maximum hydraulic efficiency is close to one of the counter-rotating type hydroelectric unit designed exclusively for the turbine mode. Besides, the runners/impellers of the unit work evidently so as to coincide the angular momentum change through the front runners/impellers with that through the rear runners/impellers, namely to take the axial flow at not only the inlet but also the outlet, without the guide vanes. From these results, it can be concluded that this type unit is effective to work at not only the pumping but also the turbine modes.  相似文献   
10.
Self-incompatibility (SI) is conserved among members of the Brassicaceae plant family. This trait is controlled epigenetically by the dominance hierarchy of the male determinant alleles. We previously demonstrated that a single small RNA (sRNA) gene is sufficient to control the linear dominance hierarchy in Brassica rapa and proposed a model in which a homology-based interaction between sRNAs and target sites controls the complicated dominance hierarchy of male SI determinants. In Arabidopsis halleri, male dominance hierarchy is reported to have arisen from multiple networks of sRNA target gains and losses. Despite these findings, it remains unknown whether the molecular mechanism underlying the dominance hierarchy is conserved among Brassicaceae. Here, we identified sRNAs and their target sites that can explain the linear dominance hierarchy of Arabidopsis lyrata, a species closely related to A. halleri. We tested the model that we established in Brassica to explain the linear dominance hierarchy in A. lyrata. Our results suggest that the dominance hierarchy of A. lyrata is also controlled by a homology-based interaction between sRNAs and their targets.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号