全文获取类型
收费全文 | 225篇 |
免费 | 20篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 13篇 |
综合类 | 11篇 |
化学工业 | 6篇 |
金属工艺 | 4篇 |
机械仪表 | 4篇 |
建筑科学 | 22篇 |
矿业工程 | 13篇 |
能源动力 | 3篇 |
轻工业 | 12篇 |
水利工程 | 2篇 |
石油天然气 | 19篇 |
武器工业 | 1篇 |
无线电 | 6篇 |
一般工业技术 | 5篇 |
冶金工业 | 119篇 |
原子能技术 | 4篇 |
自动化技术 | 7篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 6篇 |
2012年 | 7篇 |
2011年 | 39篇 |
2010年 | 22篇 |
2009年 | 12篇 |
2008年 | 15篇 |
2007年 | 17篇 |
2006年 | 18篇 |
2005年 | 10篇 |
2004年 | 11篇 |
2003年 | 11篇 |
2002年 | 9篇 |
2001年 | 8篇 |
1999年 | 3篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1993年 | 1篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1977年 | 1篇 |
1970年 | 1篇 |
1963年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有251条查询结果,搜索用时 15 毫秒
91.
Giana Angelo Victoria J. Drake 《Critical reviews in food science and nutrition》2015,55(14):1968-1991
We reviewed recent scientific evidence regarding the effects of multivitamin/mineral (MVM) supplements on risk of chronic diseases, including cancer, cardiovascular disease, and age-related eye diseases. Data from randomized controlled trials (RCTs) and observational, prospective cohort studies were examined. The majority of scientific studies investigating the use of MVM supplements in chronic disease risk reduction reported no significant effect. However, the largest and longest RCT of MVM supplements conducted to date, the Physicians’ Health Study II (PHS II), found a modest and significant reduction in total and epithelial cancer incidence in male physicians, consistent with the Supplémentation en Vitamines et Minéraux Antioxydants (SU.VI.MAX) trial. In addition, PHS II found a modest and significant reduction in the incidence of nuclear cataract, in agreement with several other RCTs and observational, prospective cohort studies. The effects of MVM use on other subtypes of cataract and age-related macular degeneration remain unclear. Neither RCTs nor prospective cohort studies are without their limitations. The placebo-controlled trial design of RCTs may be inadequate for nutrient interventions, and residual confounding, measurement error, and the possibility of reverse causality are inherent to any observational study. National surveys show that micronutrient inadequacies are widespread in the US and that dietary supplements, of which MVMs are the most common type, help fulfill micronutrient requirements in adults and children. 相似文献
92.
Woods Steven Paul; Weber Erica; Weisz Bradley M.; Twamley Elizabeth W.; Grant Igor 《Canadian Metallurgical Quarterly》2011,56(1):77
Objective: To determine whether deficits in prospective memory (i.e., “remembering to remember”) confer an increased risk of unemployment in individuals living with chronic HIV infection. Methods: Fifty-nine Unemployed and 49 Employed individuals with HIV infection underwent comprehensive neuropsychological and medical evaluations, including measures of prospective memory. Results: The Unemployed participants demonstrated significantly lower performance on time- and event-based prospective memory, which was primarily characterized by errors of omission. Importantly, prospective memory impairment was an independent predictor of unemployment when considered alongside other neurocognitive abilities, mood disturbance, and HIV disease severity. Conclusions: Prospective memory impairment is a salient predictor of unemployment in persons living with HIV infection and might be considered in screening for unemployment risk and developing vocational rehabilitation plans. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
93.
Xiao-fei Guo Yue Ruan Zi-hao Li 《Critical reviews in food science and nutrition》2019,59(17):2850-2862
AbstractEpidemiological studies have suggested controversial associations between flavonoid subclasses and type 2 diabetes mellitus (T2DM) risk. The aim of the present meta-analysis was to quantitatively estimate these associations with prospective cohort study. A systematic literature search in PubMed and Scopus databases was performed up to May 2018. Multivariate-adjust relative risks (RRs) with corresponding 95% confidence intervals (CIs) for the highest versus the lowest category were pooled by using a random-effects model. Using restricted cubic spline regression model, non-linear dose-response analysis was estimated. Nine independent prospective cohort studies with 172,058 participants and 16910 events were included. Dietary intakes of flavanols, flavonols, flavan-3-ols and isoflavones were inversely associated with T2DM risk, and the summary RRs were 0.86 (95%CI: 0.77, 0.97), 0.91 (95%CI: 0.85, 0.98), 0.90 (95%: 0.82, 0.99) and 0.91 (95%CI: 0.84, 0.98), respectively. Dose-response analysis showed that 135?mg/day increment of flavanols (95%CI: 0.92, 0.96; P for trend <0.001), 50?mg/day increment of flavonols (95%CI: 0.88, 0.99, P for trend?=?0.021), 68?mg/day increment of flavan-3-ols (95%CI: 0.92, 0.96, P for trend <0.001), or 1.8?mg/day increment of isoflavones (95%CI: 0.92, 0.97, P for trend <0.001) were associated with 6% reduction in T2DM risk. Non-significant association was observed with respect to flavanones and flavones. The present meta-analysis provides substantial evidence that dietary intakes of flavanols, flavonols, flavan-3-ols and isoflavones were inversely associated with T2DM risk, respectively. Higher dietary intakes of flavanol-, flavonol-, flavan-3-ol- and isoflavone-foods would have beneficial effects for protection against T2DM. 相似文献
94.
The effect of delay on prospective memory (PM) is mixed. Research has typically shown that PM either decreases or remains unchanged as the time increases between intention formation and encounter with a PM cue. However, the results of one study demonstrated that PM sometimes increases with increasing delays (Hicks, Marsh, & Russell, 2000). Hicks et al. hypothesised that increasing the delay may afford an opportunity for people to spontaneously rehearse the intention, or to be reminded of the intention. In the present work, we tested delays of 6 minutes, 21 minutes, and 36 minutes. Two factors were orthogonally manipulated between-subjects. One was the duration of the filler task that came between intention formation and the beginning of the ongoing task in which PM cues were embedded. The second was the duration of the ongoing task prior to the presentation of the first PM cue. Lengthening the ongoing task delay decreased PM. However, lengthening the filler task nominally increased PM. These results suggest that delays within the ongoing task replicate the effects traditionally found in retrospective memory work. In contrast, delays between intention formation and the beginning of the ongoing task may not have straightforward effects on PM retrieval. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
95.
Knight Justin B.; Meeks J. Thadeus; Marsh Richard L.; Cook Gabriel I.; Brewer Gene A.; Hicks Jason L. 《Canadian Metallurgical Quarterly》2011,37(2):298
In event-based prospective memory, current theories make differing predictions as to whether intention-related material can be spontaneously noticed (i.e., noticed without relying on preparatory attentional processes). In 2 experiments, participants formed an intention that was contextually associated to the final phase of the experiment, and lures that overlapped to differing degrees with the features of the intention-related cues were embedded in the initial phase. When participants were outside of the appropriate responding context (i.e., the initial phase), they exhibited slower latencies to lures that exactly matched the features of their intention compared with other types of lures and control words. In addition, on a final remember/know recognition test, participants reported having greater subjective recollection for the occurrence of the exact-match lures. These results suggest that exact-match lures were spontaneously noticed and differentially processed in the absence of any observable preparatory attentional processes. The findings have implications for the theoretical debate over whether preparatory attention must always be relied upon to notice intention-related material. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
96.
The neural correlates of prospective retrieval mode, and the basis of the interaction between prospective memory (PM) and task switching, were examined using event-related brain potentials (ERPs). In two experiments individuals performed pure and mixed blocks of trials where they indicated whether or not a word was a noun or a verb or contained one or two vowels based upon a cue that was presented before the target stimulus. Experiment 1 revealed that prospective retrieval mode was associated with slow wave activity over the frontal and posterior regions of the scalp that differed in topography depending upon whether the PM cues were embedded in pure or mixed blocks of trials. This experiment also revealed that the neural correlates of task set configuration, but not cue encoding, were sensitive to PM load. These data indicate that PM load may effect task switching by influencing an individual's ability to maintain multiple task sets in working memory and to efficiently implement a given task set to guide task performance. Additionally, task switching may effect PM by influencing the degree to which individuals rely on stimulus-independent and stimulus-oriented processing to support the realization of delayed intentions. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
97.
±1100kV特高压直流输电晶闸管阀运行试验系统设计 总被引:1,自引:0,他引:1
为满足我国特高压直流输电发展和建设的需要,提出了满足±1 100kV特高压工程换流阀运行试验系统的设计。根据±1 100kV特高压工程规范,提出了预期运行试验参数,从运行试验系统的一次电气原理设计、二次控制保护设计和测量监测设计3个方面进行讨论和研究,最终通过仿真手段对电气原理和控制系统原理进行了验证。研究结果表明,±1 100kV特高压工程换流阀运行试验系统设计是可行的,可以满足所有运行试验的要求,更加符合换流阀设计的特点,能够达到试验检测目的。该试验回路建成,可以满足±1 100kV工程阀15级串联同时进行运行试验,也将成为世界上容量最大的运行试验回路,可以为我国±1 100kV直流输电工程研发和工程建设提供保障。 相似文献
98.
Wang Lijuan; Altgassen Mareike; Liu Wei; Xiong Weirui; Akgün Canan; Kliegel Matthias 《Canadian Metallurgical Quarterly》2011,47(1):226
The present study examined the role of controlled attention in age differences in event-based prospective memory performance across adolescence. The researchers tested whether presenting the prospective memory cue in or out of focal awareness of the ongoing task (resulting in low versus high demands for controlled attention, respectively) might affect age-related prospective memory performance. In total, 119 Chinese participants ages 13 to 20 took part in this study (60 adolescents: age M = 13.26 years, SD = 0.50; 23 boys; 59 young adults: age M = 19.70 years, SD = 0.87; 19 men). Findings demonstrated a significant interaction, F(1, 114) = 6.41, p 相似文献
99.
Grundgeiger Tobias; Sanderson Penelope; MacDougall Hamish G.; Venkatesh Balasubramanian 《Canadian Metallurgical Quarterly》2010,16(4):317
Interruptions are frequent in many work domains. Researchers in health care have started to study interruptions extensively, but their studies usually do not use a theoretically guided approach. Conversely, researchers conducting theoretically rich laboratory studies on interruptions have not usually investigated how effectively their findings account for humans working in complex systems such as intensive care units. In the current study, we use the memory for goals theory and prospective memory theory to investigate which properties of an interruption influence how long it takes nurses to resume interrupted critical care tasks. We collected data with a mobile eye tracker in an intensive care unit and developed multiple regression models to predict resumption times. In 55.8% of all interruptions there was a finite—and therefore analyzable—resumption lag. For these cases, the main regression model explained 30.9% (adjusted R2) of the variance. Longer interruptions (β = .36, p p 相似文献
100.
On the basis of consistently finding significant overall costs to the ongoing task with a single salient target event, Smith, Hunt, McVay, and McConnell (2007) concluded that preparatory attentional processes are required for prospective remembering and that spontaneous retrieval does not occur. In this article, we argue that overall costs are not completely informative in terms of specifying the underlying processes mediating prospective memory retrieval, and we suggest more promising approaches for testing for the existence of these processes. We also argue that counterbalancing in a within-subjects design is one of several proper methods for assessing costs. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献