全文获取类型
收费全文 | 18223篇 |
免费 | 2461篇 |
国内免费 | 1397篇 |
专业分类
电工技术 | 484篇 |
综合类 | 1725篇 |
化学工业 | 2603篇 |
金属工艺 | 559篇 |
机械仪表 | 793篇 |
建筑科学 | 1575篇 |
矿业工程 | 687篇 |
能源动力 | 247篇 |
轻工业 | 2895篇 |
水利工程 | 689篇 |
石油天然气 | 1067篇 |
武器工业 | 173篇 |
无线电 | 2130篇 |
一般工业技术 | 1731篇 |
冶金工业 | 579篇 |
原子能技术 | 107篇 |
自动化技术 | 4037篇 |
出版年
2024年 | 55篇 |
2023年 | 250篇 |
2022年 | 507篇 |
2021年 | 582篇 |
2020年 | 692篇 |
2019年 | 629篇 |
2018年 | 521篇 |
2017年 | 677篇 |
2016年 | 710篇 |
2015年 | 791篇 |
2014年 | 1220篇 |
2013年 | 1158篇 |
2012年 | 1459篇 |
2011年 | 1454篇 |
2010年 | 1204篇 |
2009年 | 1182篇 |
2008年 | 1072篇 |
2007年 | 1350篇 |
2006年 | 1152篇 |
2005年 | 953篇 |
2004年 | 800篇 |
2003年 | 664篇 |
2002年 | 534篇 |
2001年 | 447篇 |
2000年 | 368篇 |
1999年 | 298篇 |
1998年 | 233篇 |
1997年 | 183篇 |
1996年 | 186篇 |
1995年 | 174篇 |
1994年 | 134篇 |
1993年 | 105篇 |
1992年 | 74篇 |
1991年 | 51篇 |
1990年 | 42篇 |
1989年 | 32篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 16篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1979年 | 6篇 |
1964年 | 8篇 |
1963年 | 5篇 |
1962年 | 5篇 |
1957年 | 3篇 |
1955年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Kazi Md. Shorowordi Md. Mohar Ali Bepari 《Journal of Materials Engineering and Performance》2002,11(6):625-630
Carbon (0.13%) steel samples containing about 0.48% molybdenum (Mo) singly and in combination with nickel (Ni) were carburized in a natural Titas gas atmosphere at a temperature of 1223 K (950 °C) and at a pressure of about 0.10 MPa (15 psia) for time periods ranging from 1–4 h followed by slow cooling in the furnace. Their microstructure was studied by optical microscopy. The austenite grain size of the case and the case depths were determined. It was found that Mo and Ni alone and in combination decrease the thickness of the cementite network near the surface of the carburized case of the steels. However, Ni is found to be more effective than Mo in decreasing the thickness of cementite network. Both Mo and Ni enhance the formation of Widmanstätten cementite plates at the grain boundary and within the grains near the surface of the carburized steels. However, Ni alone is more effective than Mo in the formation of Widmanstätten cementite plates. In the presence of Ni, Mo is much more effective in the formation of Widmanstätten cementite plates than Mo in absence of Ni. It was also revealed that both Mo and Ni increased the case depth. Ni is more effective than Mo in increasing the case depth. The combined effect of Mo and Ni is much greater than that of either Mo or Ni alone in increasing case depth. Mo as Mo carbide (Mo2C) particles refined the austenite grain size of the carburized case. Ni in solution was not found to have any effect in restricting grain growth of austenite, but the presence of Ni enhances the austenite grain size refining effect of Mo in the carburized case. 相似文献
53.
Roy S. Berns 《Color research and application》2007,32(4):334-335
The term “color gamut” historically has been associated with color output such as optimal color stimuli and additive and subtractive imaging systems. Recently, this term has been used with input devices such as scanners and digital cameras. It is proposed that the term “color‐gamut rendering” should be used instead of input devices. This clarifies the distinction between input (analysis) and output (synthesis) color systems in terms of the effect of an input system on defining the colorimetric properties of an output system. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 334–335, 2007 相似文献
54.
This study examined how 1 symbol is selected to control the allocation of attention when several symbols appear in the visual field. In Experiments 1-3, the critical target feature was color, and it was found that uninformative central arrows that matched the color of the target were selected and produced unintentional shifts of attention (i.e., involuntary, initiated slowly, producing long-lasting facilitatory effects). Experiment 4 tested whether such selection is the result of an attentional filter or of a competition bias due to a match of incoming information against integrated object representations stored in working memory. Here, the critical feature was shape and color was irrelevant, but matching color arrows were still selected. Thus, features of objects in working memory will bias the selection of symbols in the visual field, and such selected symbols are capable of producing unintentional shifts of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
Braithwaite Jason J.; Humphreys Glyn W.; Hodsoll John 《Canadian Metallurgical Quarterly》2003,29(4):758
Five experiments addressed the role of color grouping in preview search (D. G. Watson & G. W. Humphreys, 1997). Experiment 1 used opposite color ratios of distractors in preview and second search displays, creating equal numbers of distractors in each color group in the final display. There was selective slowing for new targets carrying the majority color of the old items. This effect held when there was no bias in the preview and only the second search set had an uneven color ratio (Experiment 2). In Experiment 3, participants had foreknowledge of the target color, and effects were shown over and above those due to color biases. Experiment 4 demonstrated negative color carryover even when previews changed color. Experiment 5 showed reduced color carryover effects when previews were presented more briefly. Collectively, the results provide evidence for inhibitory carryover effects in preview search based on feature grouping. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
56.
It has been reported that it is harder to switch to a strong, well-practiced task from a weaker, less-practiced task than vice versa. Three experiments replicated this surprising asymmetry and investigated how it is affected by a reduction in interference between tasks. Experiment 1 progressively delayed the onset of the stimulus attribute associated with the stronger task. Experiments 2 and 3 separated the response sets of the tasks. Both manipulations reduced, without eliminating, interference of the stronger with the weaker task but reversed the asymmetry of switch costs, resulting in a larger cost of switching to the weaker task. The results are interpreted in terms of a model of the interactions between control input, task strength, and task priming. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
57.
ABSTRACT: How the quality of cold-smoked Atlantic salmon ( Salmo salar ) is affected by freezing the raw fish as whole fish, as gutted fish, and as fillets before smoking, and by freezing the finished product after smoking was studied. Freezing before smoking resulted in increased product yield and water content, but softer texture and increased K-value. Freezing reduced the content of astaxanthin but increased the lightness and the color intensity of the flesh. Gaping increased when the fish was frozen as fillets before smoking. Freezing only after smoking led to fewer changes in quality than freezing before smoking, whereas refreezing the finished products had little additional effect on quality. 相似文献
58.
在工业CT断层图像缺陷检测应用中,提出了将数字高程模型DEM与伪彩色技术一起应用于二维灰度图像缺陷检测领域的算法流程。应用该算法流程,能够充分利用CT断层灰度图像信息,获得清晰的视觉检查效果,从而大大增强了系统检测缺陷的能力。在大型工业CT图像重建与检查分系统中采用该算法流程已经取得了较为理想的效果。 相似文献
59.
60.