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   40篇
  免费   3篇
化学工业   4篇
金属工艺   2篇
建筑科学   2篇
轻工业   11篇
石油天然气   1篇
无线电   6篇
一般工业技术   1篇
冶金工业   11篇
自动化技术   5篇
  2023年   2篇
  2022年   1篇
  2021年   2篇
  2020年   2篇
  2019年   3篇
  2017年   2篇
  2016年   1篇
  2015年   2篇
  2014年   1篇
  2013年   2篇
  2012年   1篇
  2011年   2篇
  2010年   2篇
  2009年   2篇
  2007年   2篇
  2005年   1篇
  2004年   1篇
  2002年   1篇
  1999年   1篇
  1998年   2篇
  1997年   2篇
  1994年   2篇
  1992年   1篇
  1983年   1篇
  1982年   1篇
  1977年   1篇
  1976年   2篇
排序方式: 共有43条查询结果,搜索用时 187 毫秒
11.
A novel method for testing ultra-high-temperature ceramics (UHTC) at very high temperature (above to 2,200 °C) in air with an exposure time of several minutes is used. The well-known ZrB2 + SiC material shows a limited temperature of use in an oxidizing environment due to the low stability above 2,000 °C of any silica that is formed. A few new systems without silicon are proposed, starting with the Hf or Zr, C, B and rare earth elements. The choice of rare earths is motivated by the formation of oxides with melting points higher than 2,000 °C. The complex oxide scales formed during oxidation are accurately described, in terms of presence of porosity and gradients of composition. Similarities with the mechanism of oxidation described for ZrB2 + SiC materials are shown. A significantly higher thermal stability of rare-earth oxide containing ceramics compared to silica is highlighted. As a consequence, the protective capacity of the oxide scale is improved.  相似文献   
12.
Current EU regulations on the protection of products with certain characteristics (geographical indications and designations of origin) aim to ensure fair competition for producers and increased consumers’ trust. Within the European integrated research project TRACE analytical methods are being developed to allow the maintenance of specific regulations for PGIs (products of protected geographical indication) and PDOs (products of designated origin). An example within the project is the PGI wheat variety Farro della Garfagnana. The aim of the research was to develop a method to establish the purity of Farro della Garfagnana DNA in complex cereal mixtures. The combined approach of padlock probe ligation and multiplex microarray detection can identify possible admixtures. One undesired ‘contaminant’ for Farro della Garfagnana is common bread wheat (Triticum aestivum), containing the BBAuAuDD genome. Since Farro harbours the BBAuAu genome, absence of the D-genome rules out the presence of bread wheat. The current detection limit of this multimethod is at least 2.5% bread wheat in Farro.  相似文献   
13.
Four main issues are considered in response to H. M. Wellman (see record 1997-42548-002) and M. Gauvain (see record 1997-42548-003): the relevance of adult data, the source of evidence for theories of mind, explaining development, and the proper focus of theory of mind research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
14.
The corrosion inhibition properties of newly synthesized 1-(2-pyrrole carbonyl)-benzotriazole (PCBT) and 1-(2-thienyl carbonyl)-benzotriazole (TCBT) in combination with the non-ionic surfactant Triton X-100 (TX-100) on metallic copper were studied in ground water environment and the results were compared with benzotriazole (BTA). Various electrochemical studies such as open circuit potential (OCP), potentiodynamic polarization, ac impedance and cyclic voltammetric (CV) were made. Surface analytical techniques like FT-IR and XRD were also performed. The results indicated that PCBT is a better corrosion inhibitor for copper and the formulation consisting of PCBT and TX-100 offered improved inhibition efficiency (IE) in a synergistic manner.  相似文献   
15.
Most studies of counterproductive work behavior (CWB) are criticized for overreliance on self-report methodology. This study tested the convergence of 136 matched self-reports and coworker-reports of work stressors and CWB. For each participant dyad, the focal employee ("incumbent") completed a self-report survey and gave a coworker form to a peer familiar with the incumbent's work situation and behavior. Correlations and t tests demonstrated significant convergence between incumbent and coworker reports of key study variables, except organization-targeted CWB. Separately, both incumbent and coworker reports supported the Stressor-Emotion CWB model. In mixed-source analyses, only interpersonal relationships were significant--conflict and CWB targeting persons. Weaknesses in each report source are discussed, and multisourced triangulation to cover perceptual, experiential, and behavioral domains is recommended. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
16.
On the basis of the several studies recently published on the concentration of Hg and other heavy elements in seafish and especially tunafish a work as been carried out to determine the intake due to canned tunafish for the italian population. Instrumental activation analysis has been applied to tunafish canned samples avaible on the market in Rome. The following trace elements have been measured: Cr, Se, Hg, Cs, Fe, Zn, Co, Sb. The intake of Hg and other elements through the canned tuna foods have been evaluated on the basis of the production of such foods in Italy. The tunafish contribution to the total trace elements intakes has been determined by comparing the trace elements concentrations in the canned tunafish with those referred to diets that are representative for the italian population. The results obtained have demonstrated that the trace elements intake through the diet is not significantly influenced by the tunacanned foods intake.  相似文献   
17.
There is considerable evidence in the recent literature on children's understanding of the mind that young children have difficulty understanding false beliefs. Even when presented very strong evidence that a person's belief conflicts with the reality to which it refers, they tend to assume that it coincides with reality. Two studies tested the extent to which 3-yr-olds make this same mistake with other mental states. Results show that children of this age understand that desires can differ from reality before they understand that beliefs can, even when the exact same tasks are used to assess each understanding. Findings also indicate that young children understand pretense in this regard somewhat later than desire but earlier than belief and dream, particularly when the pretense is supported by actions. Three explanations for the results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
18.
An important issue for understanding early cognition is why very young children's real-world representations do not get confused by pretense events. One possible source of information for children is the pretender's behaviors. Pretender behaviors may vary systematically across real and pretend scenarios, perhaps signaling to toddlers to interpret certain events as not real. Pretender behaviors were examined in 2 experiments in which mothers were asked both to pretend to have a snack and really to have a snack with their 18-month-olds. Episodes were analyzed for condition differences in verbal and nonverbal behaviors, including smiling, looking, laughter, and functional movements. Reliable differences were found across conditions for several variables. In a 3rd experiment, children's apparent understanding of pretense in relation to their mothers' behaviors was examined, and significant associations were found with some of the mothers' behavioral changes but not others. This work provides a first inroad into the issue of how children learn to interpret pretense acts as pretense. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
19.
Blood samples were taken from fourteen sexually mature (ripe) male Atlantic salmon (Salmo salar), eight from the acidic Westfield river (pH 4.7) and six from the less acidic (pH 5.6) Medway river to determine if there is any difference in sex hormone production in the fish in the two rivers.The plasma levels of the two principal male sex hormones, testosterone and 11-ketotestosterone, which normally peak at functional sexual maturity, were significantly lower in salmon from the more acidic Westfield river compared to those in salmon from the Medway river. Since these fish were of the same stock, and were in the same state of sexual maturation, it is suggested that the more acidic Westfield River has affected the production and/or utilization of sex hormones in this species.  相似文献   
20.
Complex adaptive systems have historically been studied using simplifications that mandate deterministic interactions between agents or instead treat their interactions only with regard to their statistical expectation. This has led to an anticipation, even in the case of agents employing inductive reasoning in light of limited information, that such systems may have equilibria that can be predicted a priori. This hypothesis is tested here using a simulation of a simple market economy in which each agent's behavior is based on the result of an iterative evolutionary process of variation and selection applied to competing internal models of its environment. The results indicate no tendency for convergence to stability or a long-term equilibrium and highlight fundamental differences between deterministic and stochastic models of complex adaptive systems  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