全文获取类型
收费全文 | 66篇 |
免费 | 3篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 2篇 |
综合类 | 7篇 |
化学工业 | 14篇 |
金属工艺 | 5篇 |
机械仪表 | 3篇 |
建筑科学 | 7篇 |
矿业工程 | 3篇 |
能源动力 | 2篇 |
石油天然气 | 1篇 |
无线电 | 15篇 |
一般工业技术 | 3篇 |
冶金工业 | 17篇 |
原子能技术 | 1篇 |
自动化技术 | 1篇 |
出版年
2024年 | 1篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2018年 | 1篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2011年 | 1篇 |
2010年 | 6篇 |
2009年 | 5篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2006年 | 1篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 6篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有81条查询结果,搜索用时 15 毫秒
1.
Basing on TGA (thermal gravimetric analysis) of thermal nitridation at l200, l250, l300℃, respectively,analysis of high temperature kinetics for nitridation of silicon monocrystal has been carried out. According tothe theory for kinetics of reaction of vapour with solid phase a nitridation kinetic model, from which it can beshown thal the rate of nitridation reaction of silicon crystal should be controlled by three stage limiting factors,was proposed. These limiting factors are chemical reaction, chemical reaction mixed with diffusion and diffu-sion. Using this model to treat our experimental data, satisfactory correlation coefficient and apparentactivation energy of nitridation of p-type (lll) silicon crystal have been obtained. The nitride film was identi'fied to be a-Si_3N_4 (Hexagonal, a=0.7758nm,c_o=0.5623nm) by X-ray diffraction analysis. Morphology ofthe nitride films formed in different nitridation duration was observed in both planar andcross-sectional viewsby SEM (scanning electron microscope). 相似文献
2.
采用氮保护气氛生长的功率晶体管用硅单晶的研究 总被引:1,自引:0,他引:1
本文论述在纯氮气氛中生长硅单晶技术,根据器件工艺要求,与器件厂相互配合,取得了功率晶体管成品率的大幅度提高,肯定了氮保护气氛下生长的硅单晶的优越质量。 相似文献
3.
研究了加料顺序,陈化方式,陈化条件,对Fe(naph)_2—Al(i—Bu)_3——CH_2=CHCl体系催化丁二烯聚合活性的影响。结果发现按Bd+Fe+Cl+Al的加料顺序配制的催化剂的活性高于其它加料顺序;陈化方法不能提高催化剂的活性。 相似文献
4.
This paper presents the study of a thermoelectric cooler (TEC) designed for small‐scale space conditioning applications in buildings. A theoretical study was undertaken to find the optimum operating conditions, which were then applied in the laboratory testing work. A TEC unit was assembled and tested under laboratory conditions. Eight pieces of UltraTEC were shown to generate up to 220 W of cooling with a COP of 0.46 under the input current of 4.8 A for each module. Thermo‐economical analysis was carried out and results showed that a system with PV panel can compete with an equivalent system without a PV panel when PV costs fall down to or lower than £1.25 per Watt. For the cases without a PV panel, the system with a high level of TEC power input delivered a better performance in terms of the average cooling energy price than that system with a low level of TEC power input after critical interest rate (currently 4%). Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
5.
6.
为实现采矿权勘测定界工作科学化、规范化、精准化,研究制定采矿权勘测定界技术规程已刻不容缓。本文基于矿业权“三位一体”权利结构的解析,从准入资质、国土空间管控行政权及资产物权三个维度,梳理了相关技术标准对勘测定界测量精度的规定,确定采矿权勘测定界测量精度应分级规制,不应一刀切。从物权角度探讨了采矿权勘测定界测量精度的决定因素,规定了三个等级采矿权勘测定界测量中误差分别为0.1、0.2、1.0m。最后提出了关于矿区范围拐点坐标数值只需保留两位的政策建议。 相似文献
7.
Drawing from cognitive-developmental and cartographic theory, the authors tested children's understanding of person–map–space relations. After introducing maps of the classroom, an adult moved to different positions in the room and pointed straight ahead. Five- to 12-yr-old children (N?=?259) placed colored arrow stickers on the map to show the person's location and heading, once when the map was aligned with the room and once when rotated 180°. Performance was better on the aligned condition and when headings were parallel to the nearby wall; most younger children failed to understand point of view; and sex differences favored boys. Data from 168 children given additional spatial tasks were consistent with the hypothesized importance of projective spatial concepts for mapping. Data suggest that it is geometric (spatial) rather than representational (symbolic) space–map correspondences that pose particular difficulty for older children. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
9.
Investigated the role of operative schemes in explaining older children's superior memory on past Piagetian memory tasks. In Exp I, 60 1st–4th grade concrete operational children—half with deficits in visual memory (learning disabled, LD)—reconstructed 2 stimuli in which operative schemes were or were not relevant (a seriated array vs an arbitrary color sequence). As predicted, LD children performed significantly worse than normals on the arbitrary stimulus only. Exp II tested whether this difference resulted simply from differential task difficulty. 28 preschoolers who either could or could not seriate reconstructed both stimuli. Only seriaters performed significantly better on the operative stimulus than on the arbitrary stimulus, supporting the Piagetian position. (2 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
One possible explanation of the long-term memory improvement for seriated stimuli reported by Piaget and B. Inhelder (1973) is that there is a developmental increase in the tendency to seriate any drawing spontaneously. Results of an earlier study by R. Altemeyer et al (see record 1970-02150-001) do not support this explanation. In the present study, a total of 377 kindergarten, 1st-, 2nd-, and 3rd-grade children were tested to determine whether other developmental changes in drawings might have obscured an underlying change in the tendency to seriate. Using Altemeyer's procedure, which required children to draw pictures from a relatively vague hint, no developmental change in seriation was found. However, a significant developmental increase in the production of representational drawings did occur. This latter age difference was eliminated by using a more informative hint, and with this modification, a developmental increase in the tendency to seriate was revealed. Results are discussed in relation to previous Piagetian memory research. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献