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   193篇
  免费   8篇
综合类   1篇
化学工业   38篇
机械仪表   2篇
建筑科学   14篇
矿业工程   1篇
能源动力   4篇
轻工业   33篇
水利工程   1篇
石油天然气   2篇
无线电   8篇
一般工业技术   15篇
冶金工业   41篇
自动化技术   41篇
  2024年   1篇
  2023年   2篇
  2022年   7篇
  2021年   8篇
  2020年   4篇
  2019年   7篇
  2018年   6篇
  2017年   6篇
  2016年   11篇
  2015年   2篇
  2014年   8篇
  2013年   15篇
  2012年   6篇
  2011年   15篇
  2010年   7篇
  2009年   11篇
  2008年   13篇
  2007年   14篇
  2006年   9篇
  2005年   12篇
  2004年   4篇
  2003年   3篇
  2002年   4篇
  1999年   4篇
  1998年   1篇
  1996年   1篇
  1995年   3篇
  1994年   1篇
  1993年   2篇
  1991年   7篇
  1990年   1篇
  1988年   1篇
  1987年   1篇
  1986年   2篇
  1982年   1篇
  1979年   1篇
排序方式: 共有201条查询结果,搜索用时 15 毫秒
91.
The aim of this study was to (i) make a posture analysis of teachers during theoretical classroom teaching; (ii) to estimate the risk for the development of musculoskeletal problems (MSP); (iii) test the hypotheses that an electronic school board (EB) has more ergonomic advantages for teachers. Thirty-five secondary school teachers, of which 15 used an EB and 20 used chalkboards, were selected by convenience sampling and filmed during 30 min of a theoretical course. Posture analysis of back, arms, legs and risk assessment was performed using the Ovako Working Posture Analysis System. Most of the teachers’ postures did not indicate a higher risk for MSP. However, some postures may be harmful when accumulated for several hours of teaching a day; especially, long periods of standing and standing with a bended back. Results also indicated that currently the use of an EB does not improve teachers’ posture.

Practitioner Summary: The relationship between objectively measured physical work load and risk for injuries among teachers was not analysed so far. In this study teachers’ posture was analysed using the OWAS method. Prolonged standing and forward bending were identified as risk postures. Also, using an electronic school board currently does not improve posture.  相似文献   

92.
Exhaled breath condensate (EBC) is a biological fluid that contains trace amounts of secreted pulmonary proteins, and is emerging as a potentially valuable and non-invasively obtained source of disease biomarkers. Proteome analysis of these samples could lead to the identification of prognostic indicators of airway diseases. The objective of this study was to develop a protocol for proteome analysis of EBC samples. In this report, an improved procedure for EBC sample preparation and concentration is presented, together with a method for comparison of the protein profiles between two groups. The presented approach enabled to study the condensed exhaled breath proteome for biomarker analysis, and revealed proteins not previously identified in an EBC proteomics approach. In a comparative pilot study, EBC protein profiles obtained from smokers and non-smokers showed distinct differences and are illustrative for its potential in clinical studies. EBC from smokers contained higher concentrations of the more abundant proteins, such as cytokeratins, compared to non-smokers, and calgranulin B was identified uniquely in EBC samples from smokers.  相似文献   
93.
We seek to improve information retrieval in a domain-specific collection by clustering user sessions from a click log and then classifying later user sessions in real time. As a preliminary step, we explore the main assumption of this approach: whether user sessions in such a site are related to the question that they are answering. Since a large class of machine learning algorithms use a distance measure at the core, we evaluate the suitability of common machine learning distance measures to distinguish sessions of users searching for the answer to same or different questions. We found that two distance measures work very well for our task and three others do not. As a further step, we then investigate how effective the distance measures are when used in clustering. For our dataset, we conducted a user study where we had multiple users answer the same set of questions. This data, grouped by question, was used as our gold standard for evaluating the clusters produced by the clustering algorithms. We found that the observed difference between the two classes of distance measures affected the quality of the clusterings, as expected. We also found that one of the two distance measures that worked well to differentiate sessions, worked significantly better than the other when clustering. Finally, we discuss why some distance metrics performed better than others in the two parts of our work.  相似文献   
94.
95.
Burgmans, van Boxtel, Vuurman, et al. (2009) published an interesting study titled “The Prevalence of Cortical Gray Matter Atrophy May Be Overestimated in the Healthy Aging Brain” on how subclinical cognitive disorders may affect correlations between age and cortical volume. Correlations between cortical gray matter volume and age were found in 30 elderly with cognitive decline after 6 years, but not in 28 elderly without cognitive decline. This study is important, and demonstrates that preclinical cognitive disorders may affect cortical brain volumes before being detectable by neuropsychological tests. However, we are not convinced by the conclusions: “… gray matter atrophy… is to a lesser extent associated with the healthy aging process, but more likely with brain processes underlying significant cognitive decline” (p. 547) and “… cortical gray matter atrophy in the aging brain may be overestimated in a large number of studies on healthy aging” (p. 547). We analyzed the cross-sectional MR data (n = 1,037) as well as longitudinal data from a sample of very well-screened elderly followed by cognitive testing for 2 years. In the cross-sectional data, the correlations between age and brain volumes were generally not much reduced when the upper age limit was lowered. This would not be expected if age-related incipient cognitive disorders caused the correlations given that the incidence of cognitive decline increased with age. Longitudinally, 1-year atrophy was identified in all tested regions. It is likely that cortical brain atrophy is manifested in cognitively normal elderly without subclinical cognitive disorders. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
96.
Cell-free RNAs have the potential to act as a means of gene expression regulation between cells and are therefore used as diagnostic markers describing the state of tissue environment. The origin and functions of such RNAs in human ovarian follicle, the environment of oocyte maturation, are unclear. The current study investigates the difference in the microRNA profiles of fertile women and polycystic ovary syndrome (PCOS) patients in three compartments from the same preovulatory follicle: mural granulosa cells (MGC), cell-free follicular fluid (FF), and extracellular vesicles (EV) of the FF by small RNA sequencing. In silico analysis was used for the prediction and over-representation of targeted pathways for the detected microRNAs. PCOS follicles were distinguished from normal tissue by the differential expression of 30 microRNAs in MGC and 10 microRNAs in FF (FDR < 0.1) that commonly regulate cytokine signaling pathways. The concentration of EV-s was higher in the FF of PCOS patients (p = 0.04) containing eight differentially expressed microRNAs (p < 0.05). In addition, we present the microRNA profiles of MGC, FF, and EV in the fertile follicle and demonstrate that microRNAs loaded into EVs target mRNAs of distinct signaling pathways in comparison to microRNAs in FF. To conclude, the three follicular compartments play distinct roles in the signaling disturbances associated with PCOS.  相似文献   
97.
Pheromonal communication of adult peach twig borers, Anarsia lineatella Zeller (Lepidoptera: Gelechiidae), was reinvestigated based on recent findings that virgin female-baited traps were more attractive to mate-seeking males than a two-component synthetic sex pheromone consisting of (E)-5-decen-1-yl acetate (1000 μg) and (E)-5-decen-1-ol (100 μg), suggesting that females use additional pheromone components. Hypothesizing that these additional components may be released from body parts other than abdominal sex pheromone glands, we extracted female body scales and analyzed aliquots by coupled gas chromatographic–electroantennographic detection (GC-EAD) and GC–mass spectrometry. Eight straight-chain and four methylated aliphatic hydrocarbons, as well as two acetates, all elicited responses from excised male antennae. In laboratory experiments with synthetic candidate pheromone components, a combination of octadecyl acetate, (R)-11-methyltricosane, and (S)-11-methyltricosane in the presence of gland-derived sex pheromone components were shown to elicit contact of female decoys by males. However, body pheromone components did not enhance attractiveness of sex pheromone components in field trapping experiments, suggesting that they are effective only at close range and that other stimuli are responsible for superior attractiveness of female-baited traps.  相似文献   
98.
A patient on maintenance hemodialysis asked his physician if it would be safe for him to run a marathon. For healthy persons, studies show that it is relatively safe. Very few data are available on patients on hemodialysis performing out of center endurance exercise. To address this question, we conducted a clinical study to investigate the electrolyte derangements during different running distances. Our main concern was development of hyperkalemia. We present a case of an anuric hemodialysis patient, who ran eight different runs with a maximum distance of 32.2 km. Blood was analyzed before and after the runs. We did not find severe hyperkalemia at any point. According to this study, we found no signs of increased risk.  相似文献   
99.
100.
At the 2011 Computers and Writing Conference, Town Hall speakers were asked to envision the future. This piece extends that conversation, with contributors presenting a range of ideas, often looking backward at our history before gazing into their crystal balls to envision what the future might bring. The pieces included here discuss writing, teaching writing, writing assessment, publishing, robotics, mobility, and other aspects of the field loosely termed computers and composition as it was, is, or may come to be in what we hope will be only the start of an ongoing conversation.  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