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   276篇
  免费   0篇
电工技术   2篇
化学工业   61篇
金属工艺   1篇
机械仪表   3篇
建筑科学   24篇
能源动力   2篇
轻工业   59篇
水利工程   1篇
无线电   7篇
一般工业技术   56篇
冶金工业   28篇
自动化技术   32篇
  2023年   1篇
  2022年   6篇
  2021年   9篇
  2020年   5篇
  2019年   2篇
  2018年   1篇
  2016年   7篇
  2015年   3篇
  2014年   4篇
  2013年   10篇
  2012年   17篇
  2011年   23篇
  2010年   9篇
  2009年   16篇
  2008年   15篇
  2007年   8篇
  2006年   14篇
  2005年   16篇
  2004年   6篇
  2003年   9篇
  2002年   5篇
  2001年   7篇
  2000年   3篇
  1999年   4篇
  1998年   3篇
  1997年   6篇
  1996年   7篇
  1995年   1篇
  1994年   4篇
  1993年   6篇
  1992年   4篇
  1991年   1篇
  1990年   3篇
  1989年   3篇
  1988年   2篇
  1986年   4篇
  1985年   1篇
  1984年   2篇
  1983年   4篇
  1982年   4篇
  1981年   2篇
  1980年   5篇
  1979年   1篇
  1978年   1篇
  1977年   4篇
  1976年   3篇
  1974年   2篇
  1973年   2篇
  1966年   1篇
排序方式: 共有276条查询结果,搜索用时 15 毫秒
21.
Juvenile court judges are often required to make distinctions as to whether certain adolescents should remain in the juvenile justice system or be transferred to adult courts. Typically, 3 broad factors weigh into juvenile court judges' decision making: (a) the level of danger the juvenile poses to the community, (b) the level of sophistication-maturity of the juvenile, and (c) the extent to which the juvenile is viewed as treatable. In an earlier study, knowledge of forensic and child psychologists was tapped to elucidate core characteristics related to the transfer process (R. T. Salekin et al, 2001). The current study augments that investigation. Judges provided (a) their perspective regarding the core criteria for dangerousness, sophistication-maturity, and amenability to treatment, and (b) data on the core characteristics of juveniles who were evaluated and subsequently judged to be appropriate for transfer to adult criminal courts. Policy implications for this increasingly critical interface between law and psychology are threefold: (a) Individualized assessments are key; (b) the adoption of a national standard for transfer to adult court is required; and (c) the development of treatment programs to improve the socialization of youth is necessary. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
22.
23.
Empirical evidence suggests that computer self-efficacy plays an important role in one’s acceptance and use of new information technology. Little is however known about the antecedents of computer self-efficacy. This paper reports on a study of 143 non-users of a self-checkout library system available at a large Canadian university which was conducted to investigate the relationships between stable personality traits and gender with computer self-efficacy. Results indicate that four of the five stable personality traits, as measured by the Big-5 factors of personality, contribute to explain computer self-efficacy. Taking gender into account, results show that the traits of neuroticism, extraversion, and agreeableness are significantly related to computer self-efficacy for women but not for men. Implications for research and practice are discussed.  相似文献   
24.
Ischemia can cause release of adenosine and purine catabolites from the heart, through the breakdown of ATP. If repeated periods of ischemia are induced, the efflux of purines is markedly reduced, although it is not clear if this is beneficial for the long-term survival of the heart. We have investigated changes in high-energy phosphates and purine release in the isolated perfused rat heart using31P NMR spectroscopy and high-performance liquid chromatography. Hearts were subjected to one of the following protocols: Group A—1 min of total global ischemia (TGI) after 40 min, 60 min, and 85 min of perfusion (a total of 3 × 1 min ischemia); Group B—1 min of TGI after 40 min of perfusion, 10 min of TGI after 50 min of perfusion, and a final 1 min of TGI after 85 min of perfusion. The profile of high-energy phosphate metabolites, Pi accumulation and purine release was similar for each 1-min period of TGI in Group A, whereas phosphocreatine content was increased and ATP content reduced by an extended period of TGI in Group B, leading to a less severe acidosis and purine efflux in the final 1 min of TGI at 85 min of perfusion. In conclusion, the reduced purine release observed in Group B may be related to the preischemic ATP pool size and accessibility and the increased myocardial energy reserve in the form of phosphocreatine.  相似文献   
25.
Summary The main constituents of the elastic gumbase, i.e. waxes, paraffins, glycerides, rosin derivatives, polyvinyl derivatives and elastomers, are isolated. Their structures are confirmed by IR, NMR, and GLC/MS.
Analytisches Verfahren für Kaugummi I. Elastische Grundlagen des Gummis
Zusammenfassung Die Hauptbestandteile der elastischen Grundlage des Gummis wie Wachse, Paraffine, Glyceride, Harzderivate, Polyvinylderivate, Elastomere werden isoliert. Ihre Struktur wird durch IR, NMR und CC-MS sichergestellt.
  相似文献   
26.
The feasibility of low-temperature (7 °C) anaerobic digestion for the treatment of a trichloroethylene (TCE) contaminated wastewater was investigated. Two expanded granular sludge bed (EGSB) bioreactors (R1 and R2) were employed for the mineralisation of a synthetic volatile fatty acid based wastewater at an initial organic loading rate (OLR) of 3 kg COD m−3 d−1, and an operating temperature of 15 °C. Successive reductions in OLR to 0.75 kg COD m−3 d−1, and operational temperature to 7 °C, resulted in stable bioreactor operation by day 417, with COD removal efficiency and biogas CH4 content ≥74%, for both bioreactors. Subsequently, the influent to R1 was supplemented with increasing concentrations (10, 20, 30 mg l−1) of TCE, while R2 acted as a control. At an influent TCE concentration of 30 mg l−1, although phase average TCE removal rates of 79% were recorded, a sustained decrease in R1 performance was observed, with COD removal of 6%, and % biogas CH4 of 3% recorded on days 595 and 607, respectively. Specific methanogenic activity (SMA) assays identified a general shift from acetate- to hydrogen-mediated methanogenesis in both R1 and R2 biomass, while toxicity assays confirmed an increased sensitivity of the acetoclastic community in R1 to TCE and dichloroethylene (DCE), which contributed to acetate accumulation. Quantitative Polymerase Chain Reaction (qPCR) analysis of the methanogenic community confirmed the dominance of hydrogenotrophic methanogens in both R1 and R2, representing 71-89% of the total methanogenic population, however acetoclastic Methanosaeta were the dominant organisms, based on 16S rRNA gene clone library analysis of reactor biomass. The greatest change in the bacterial community, as demonstrated by UPGMA analysis of DGGE banding profiles, was observed in R1 biomass between days 417 and 609, although 88% similarity was retained between these sampling points.  相似文献   
27.
Contribution of ozone to airborne aldehyde formation in Paris homes   总被引:1,自引:0,他引:1  
Indoor aldehydes may result from ozone-initiated chemistry, mainly documented by experimental studies. As part of an environmental investigation included in the PARIS birth cohort, the aim of this study was to examine ozone contribution to airborne aldehyde formation in Paris homes. Formaldehyde, acetaldehyde and hexaldehyde levels, as well as styrene, nitrogen dioxide and nicotine concentrations, comfort parameters and carbon dioxide levels, were measured twice during the first year of life of the babies. Ambient ozone concentrations were collected from the closest background station of the regional air monitoring network. Traffic-related nitrogen oxide concentrations in front of the dwellings were estimated by an air pollution dispersion model. Home characteristics and families' way of life were described by questionnaires. Stepwise multiple linear regression models were used to link aldehyde levels with ambient ozone concentrations and a few aldehyde precursors involved in oxidation reactions, adjusting for other indoor aldehyde sources, comfort parameters and traffic-related nitrogen oxides. A 4 and 11% increase in formaldehyde and hexaldehyde levels was pointed out when 8-hour ozone concentrations increased by 20 μg/m3. The influence of potential precursors such as indoor styrene level and frequent use of air fresheners, containing unsaturated volatile organic compounds as terpenes, was also found. Thus, our results suggest that ambient ozone can significantly impact indoor air quality, especially with regard to formaldehyde and hexaldehyde levels.  相似文献   
28.
ABCB4 (ATP-binding cassette subfamily B member 4) is an ABC transporter expressed at the canalicular membrane of hepatocytes where it ensures phosphatidylcholine secretion into bile. Genetic variations of ABCB4 are associated with several rare cholestatic diseases. The available treatments are not efficient for a significant proportion of patients with ABCB4-related diseases and liver transplantation is often required. The development of novel therapies requires a deep understanding of the molecular mechanisms regulating ABCB4 expression, intracellular traffic, and function. Using an immunoprecipitation approach combined with mass spectrometry analyses, we have identified the small GTPase RAB10 as a novel molecular partner of ABCB4. Our results indicate that the overexpression of wild type RAB10 or its dominant-active mutant significantly increases the amount of ABCB4 at the plasma membrane expression and its phosphatidylcholine floppase function. Contrariwise, RAB10 silencing induces the intracellular retention of ABCB4 and then indirectly diminishes its secretory function. Taken together, our findings suggest that RAB10 regulates the plasma membrane targeting of ABCB4 and consequently its capacity to mediate phosphatidylcholine secretion.  相似文献   
29.
Two matrices with a similar rheological behaviour but with a different composition have been developed: one containing carbohydrates (d-glucose, pectin and starch) and in the second one, called complex matrix, a lipid (triolein) was added. The release of six aroma compounds is quantified by using the measurements of partition coefficients at thermodynamic equilibrium. The role of lipid (triolein) on the retention of all the aroma compounds was pointed out. The effect of carbohydrates was more complex: in comparison with water, ethyl hexanoate and trans-2-hexenal were more retained whereas diacetyl, 2-pentanone and cis-3-hexenol were “repulsed” from the matrix. The kinetic study of the release from these matrices had shown a decrease of the initial rate of release by reference with water. From carbohydrates matrix, the decrease of the release for three compounds (ethyl acetate, ethyl hexanoate, 2-pentanone) seemed to arise from the variation of diffusion and/or retention by carbohydrates. For the three other aroma compounds (diacetyl, cis-3-hexenol and trans-2-hexenal) no variation of the initial rate was registered. The comparison of the release rates from carbohydrate and complex matrices indicated the role of lipids and the comparison of the release rates from water and complex matrix showed the combined effects of texture and lipids. The decrease of initial release rate was more important in presence of lipids than in presence of carbohydrates. The most important decrease was observed with the most hydrophobic compound.  相似文献   
30.
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