全文获取类型
收费全文 | 11101篇 |
免费 | 728篇 |
国内免费 | 291篇 |
专业分类
电工技术 | 372篇 |
综合类 | 354篇 |
化学工业 | 1614篇 |
金属工艺 | 416篇 |
机械仪表 | 618篇 |
建筑科学 | 747篇 |
矿业工程 | 241篇 |
能源动力 | 240篇 |
轻工业 | 633篇 |
水利工程 | 105篇 |
石油天然气 | 543篇 |
武器工业 | 60篇 |
无线电 | 1050篇 |
一般工业技术 | 1297篇 |
冶金工业 | 2763篇 |
原子能技术 | 100篇 |
自动化技术 | 967篇 |
出版年
2024年 | 33篇 |
2023年 | 170篇 |
2022年 | 269篇 |
2021年 | 359篇 |
2020年 | 286篇 |
2019年 | 257篇 |
2018年 | 273篇 |
2017年 | 333篇 |
2016年 | 305篇 |
2015年 | 317篇 |
2014年 | 471篇 |
2013年 | 538篇 |
2012年 | 547篇 |
2011年 | 668篇 |
2010年 | 533篇 |
2009年 | 511篇 |
2008年 | 500篇 |
2007年 | 425篇 |
2006年 | 417篇 |
2005年 | 359篇 |
2004年 | 260篇 |
2003年 | 229篇 |
2002年 | 186篇 |
2001年 | 177篇 |
2000年 | 161篇 |
1999年 | 336篇 |
1998年 | 907篇 |
1997年 | 622篇 |
1996年 | 393篇 |
1995年 | 254篇 |
1994年 | 197篇 |
1993年 | 216篇 |
1992年 | 61篇 |
1991年 | 60篇 |
1990年 | 53篇 |
1989年 | 43篇 |
1988年 | 33篇 |
1987年 | 39篇 |
1986年 | 32篇 |
1985年 | 19篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 17篇 |
1981年 | 16篇 |
1980年 | 26篇 |
1978年 | 6篇 |
1977年 | 55篇 |
1976年 | 120篇 |
1975年 | 3篇 |
1955年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
Real-time palmprint acquisition system design 总被引:1,自引:0,他引:1
Wong M. Zhang D. Kong W.-K. Lu G. 《Vision, Image and Signal Processing, IEE Proceedings -》2005,152(5):527-534
Capturing high quality palmprint images in a very short time period is a fundamental step in palmprint research. While a palmprint scanner capable of this function is especially important for developing a real-time online palmprint identification system, limited research effort has been put into designing and implementing palmprint acquisition systems. A novel palmprint acquisition system is presented, which is designed for various civilian applications such as access control, ATM, etc. The novel contactless design on the user interface prevents the distortion of the palm skin introduced by the traditional glass plate of a palm scanner. The system is designed to have the best performance at reasonable price. It has a resolution of 150 dpi that is able to obtain palmprint features, including the principal lines, wrinkles and ridge texture. The proposed system provides an important step for implementing a personal identification system using palmprint. Over 9,400 palmprint images were collected by the proposed system. An online palmprint identification system was then developed based on the proposed acquisition system. 相似文献
65.
氨合成塔出口氨含量偏低原因分析及对策 总被引:1,自引:0,他引:1
阐述UHDE合成塔运行现状 ,分析氨净值达不到设计值的原因 ,提出相应的解决措施 相似文献
66.
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
67.
The effects of acute pentobarbital treatment were assessed using a complex operant test battery containing five tasks in which correct performance is thought to depend upon processes associated with short-term memory and attention [delayed-matching-to-sample (DMTS)], color and position discrimination [conditioned position responding (CPR)], motivation [progressive ratio (PR)], time perception [temporal response differentiation (TRD)], and learning [incremental repeated acquisition (IRA)]. Adult, male rhesus monkeys were tested 15 min after IV injection of saline or pentobarbital (1, 3, 5.6, 10, or 15 mg/kg). Behavioral endpoints measured included percent task completed, response rate or latency, and response accuracy. The order of task sensitivity to disruption by PBT was TRD > IRA = DMTS = PR > CPR, in which sensitivity was defined as a significant disruption in any aspect of task performance. PBT slowed response rates at 10.0 and/or 15.0 mg/kg in all tasks. Accuracy was decreased in the TRD task at > or = 5.6 mg/kg but doses of > or = 10.0 mg/kg were required to decrease accuracy in the IRA, DMTS, and CPR tasks. Thus, behavior thought to model time perception (TRD) was more sensitive than behavior modeling learning (IRA), short-term memory and attention (DMTS), and motivation (PR). CPR was the least sensitive behavior. Because pentobarbital exerts its effects at least in part via GABA systems, the effects in the current study were compared with those of a previous study of the acute effects of diazepam. The two compounds exerted fundamentally different effects on operant test battery performance. 相似文献
68.
Flame retardant and the degradation mechanism of high impact polystyrene/Fe-montmorillonite nanocomposites 总被引:1,自引:1,他引:0
High impact polystyrene/Fe-montmorillonite (HIPS/Fe-MMT) nanocomposites were successfully prepared by melting intercalation.
The nanostructures of HIPS/Fe-MMT were testified by X-ray diffraction (XRD) and transmission electron microscope (TEM). Corresponding
to pure HIPS, the thermal stability of HIPS/Fe-MMT nanocomposites was notably improved. The peaks of heat release rate (PHRR)
and the mass loss rate (MLR) were significantly reduced after the formation of the HIPS/Fe-MMT nanocomposites from cone calorimetry.
And nanocomposites PHRR was further lower with the increase of Fe-MMT content in the range of 1 to 5 wt%. The degradation
mechanism of HIPS and HIPS/Fe-MMT nanocomposites was conducted by pyrolysis gas chromatography mass spectrometry (Py-GC-MS).
And the reason of the enhancement of thermal stability maybe is that structural iron is the operative site for radical trapping
in the Fe-MMT and the nanostructure enhances the interaction of the chains of the HIPS. 相似文献
69.
超低碳奥氏体不锈钢00Cr18Ni10还原脱磷研究 总被引:1,自引:0,他引:1
在 2 5kg真空感应炉上用镁钙合金对超低碳奥氏体不锈钢 0 0Cr18Ni10进行了还原脱磷试验。通过充入工业纯氩使炉内压力为 6 6 .6 6kPa和精炼时的反应温度 14 5 0~ 15 0 0℃ ,加入镁钙合金 5 0kg t和助熔剂CaF2 11kg t,可使精炼后 0 0Cr18Ni10的磷含量进一步降低到 (5 0~ 6 0 )× 10 - 6 ,钢中氧、硫含量分别稳定降到(4~ 6 )× 10 - 6 和 15× 10 - 6 。 相似文献
70.