全文获取类型
收费全文 | 56370篇 |
免费 | 5247篇 |
国内免费 | 2840篇 |
专业分类
电工技术 | 3587篇 |
技术理论 | 2篇 |
综合类 | 4965篇 |
化学工业 | 6870篇 |
金属工艺 | 2006篇 |
机械仪表 | 3618篇 |
建筑科学 | 10703篇 |
矿业工程 | 1297篇 |
能源动力 | 3461篇 |
轻工业 | 5517篇 |
水利工程 | 833篇 |
石油天然气 | 2464篇 |
武器工业 | 743篇 |
无线电 | 3279篇 |
一般工业技术 | 5343篇 |
冶金工业 | 2451篇 |
原子能技术 | 333篇 |
自动化技术 | 6985篇 |
出版年
2024年 | 376篇 |
2023年 | 1032篇 |
2022年 | 1937篇 |
2021年 | 2282篇 |
2020年 | 2385篇 |
2019年 | 1978篇 |
2018年 | 1917篇 |
2017年 | 2196篇 |
2016年 | 2304篇 |
2015年 | 2344篇 |
2014年 | 4117篇 |
2013年 | 3558篇 |
2012年 | 4224篇 |
2011年 | 4317篇 |
2010年 | 3353篇 |
2009年 | 3393篇 |
2008年 | 2982篇 |
2007年 | 3766篇 |
2006年 | 3018篇 |
2005年 | 2513篇 |
2004年 | 2074篇 |
2003年 | 1681篇 |
2002年 | 1349篇 |
2001年 | 1128篇 |
2000年 | 856篇 |
1999年 | 645篇 |
1998年 | 458篇 |
1997年 | 386篇 |
1996年 | 363篇 |
1995年 | 248篇 |
1994年 | 184篇 |
1993年 | 143篇 |
1992年 | 112篇 |
1991年 | 101篇 |
1990年 | 79篇 |
1989年 | 63篇 |
1988年 | 48篇 |
1987年 | 37篇 |
1986年 | 22篇 |
1985年 | 32篇 |
1984年 | 44篇 |
1983年 | 30篇 |
1982年 | 26篇 |
1980年 | 48篇 |
1965年 | 20篇 |
1964年 | 28篇 |
1963年 | 26篇 |
1961年 | 23篇 |
1956年 | 18篇 |
1955年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Shumin Zhai Jing Kong Xiangshi Ren 《International journal of human-computer studies》2004,61(6):823-856
Pointing tasks in human–computer interaction obey certain speed–accuracy tradeoff rules. In general, the more accurate the task to be accomplished, the longer it takes and vice versa. Fitts’ law models the speed–accuracy tradeoff effect in pointing as imposed by the task parameters, through Fitts’ index of difficulty (Id) based on the ratio of the nominal movement distance and the size of the target. Operating with different speed or accuracy biases, performers may utilize more or less area than the target specifies, introducing another subjective layer of speed–accuracy tradeoff relative to the task specification. A conventional approach to overcome the impact of the subjective layer of speed–accuracy tradeoff is to use the a posteriori “effective” pointing precision We in lieu of the nominal target width W. Such an approach has lacked a theoretical or empirical foundation. This study investigates the nature and the relationship of the two layers of speed–accuracy tradeoff by systematically controlling both Id and the index of target utilization Iu in a set of four experiments. Their results show that the impacts of the two layers of speed–accuracy tradeoff are not fundamentally equivalent. The use of We could indeed compensate for the difference in target utilization, but not completely. More logical Fitts’ law parameter estimates can be obtained by the We adjustment, although its use also lowers the correlation between pointing time and the index of difficulty. The study also shows the complex interaction effect between Id and Iu, suggesting that a simple and complete model accommodating both layers of speed–accuracy tradeoff may not exist. 相似文献
32.
Multiple forms of a symbol-digit substitution task were used to provide a componential analysis of age differences in coding task performance. The results demonstrated age differences in feature encoding, memory, and visual search. A 2nd experiment was conducted with young adults to investigate a sensory deficit as a locus of age differences. The spatial contrast sensitivity deficit of older adults was simulated on forms by applying a digital filter. Persons in the age-simulated contrast condition performed worse than those in the normal contrast condition. The stimulus degradation effect was linked to visual search speed. The study illustrates the utility of componential analysis and offers direct support for the hypothesis that sensory deficits affect performance on tasks used to assess intelligence (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
33.
34.
35.
36.
37.
An approximate method is presented for predicting the effect of a louvered blind on the centre‐glass thermal performance of a fenestration. The method combines a one‐dimensional heat transfer model with data from a numerical simulation of the window and blind. Sample results for a blind mounted on the indoor surface of a window show the effect of blind slat angle on heat transmission. Both summer and winter conditions are considered. The results show that a louvered blind can improve the U‐value of a standard double‐glazed window by up to 37%. Also, the radiation heat exchange with the room can be dramatically reduced (by up to 60%), which will improve the level of occupant comfort. However, there was found to be a trade‐off between U‐value and occupant comfort; placing the blind closer to the window improves the U‐value, but increases the radiation heat exchange with the room. The predictions from the present simplified method compare well with results from a full two‐dimensional computational fluid dynamics solution of the conjugate blind/window interaction. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
38.
Judge Timothy A.; Jackson Christine L.; Shaw John C.; Scott Brent A.; Rich Bruce L. 《Canadian Metallurgical Quarterly》2007,92(1):107
The present study estimated the unique contribution of self-efficacy to work-related performance controlling for personality (the Big 5 traits), intelligence or general mental ability, and job or task experience. Results, based on a meta-analysis of the relevant literatures, revealed that overall, across all studies and moderator conditions, the contribution of self-efficacy relative to purportedly more distal variables is relatively small. Within moderator categories, there were several cases in which self-efficacy made unique contributions to work-related performance. For example, self-efficacy predicted performance in jobs or tasks of low complexity but not those of medium or high complexity, and self-efficacy predicted performance for task but not job performance. Overall, results suggest that the predictive validity of self-efficacy is attenuated in the presence of individual differences, though this attenuation does depend on the context. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
39.
40.
Polyoxymethylene (POM) composites filled with low-density polyethylene (LDPE) and rice husk flour (RHF) were prepared by injection molding. The POM/5 wt % LDPE/7.5 wt % RHF composite exhibited the lowest wear rate, whereas the coefficient of friction remained low, and the POM/5 wt % LDPE/5 wt % RHF composite had the best mechanical properties. X-ray diffraction analysis was carried out, and the worn surfaces were examined with scanning electron microscopy. The results showed that the addition of the filler reduced the crystallinity degree of the POM composites. The main wear mechanism for unfilled POM was adhesion, whereas for the POM composites, wear seemed to occur mainly by fatigue and abrasion. It was experimentally confirmed that the POM composite filled with LDPE and RHF, which is well-performing, low-cost, and environmentally friendly, could be a potential material for tribological applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献