全文获取类型
收费全文 | 3408篇 |
免费 | 217篇 |
国内免费 | 201篇 |
专业分类
电工技术 | 74篇 |
综合类 | 206篇 |
化学工业 | 994篇 |
金属工艺 | 150篇 |
机械仪表 | 113篇 |
建筑科学 | 29篇 |
矿业工程 | 18篇 |
能源动力 | 48篇 |
轻工业 | 178篇 |
水利工程 | 1篇 |
石油天然气 | 82篇 |
武器工业 | 120篇 |
无线电 | 1209篇 |
一般工业技术 | 343篇 |
冶金工业 | 37篇 |
原子能技术 | 31篇 |
自动化技术 | 193篇 |
出版年
2024年 | 1篇 |
2023年 | 22篇 |
2022年 | 27篇 |
2021年 | 28篇 |
2020年 | 31篇 |
2019年 | 33篇 |
2018年 | 28篇 |
2017年 | 51篇 |
2016年 | 77篇 |
2015年 | 103篇 |
2014年 | 147篇 |
2013年 | 178篇 |
2012年 | 214篇 |
2011年 | 252篇 |
2010年 | 188篇 |
2009年 | 215篇 |
2008年 | 210篇 |
2007年 | 245篇 |
2006年 | 242篇 |
2005年 | 195篇 |
2004年 | 163篇 |
2003年 | 205篇 |
2002年 | 143篇 |
2001年 | 96篇 |
2000年 | 117篇 |
1999年 | 106篇 |
1998年 | 84篇 |
1997年 | 98篇 |
1996年 | 72篇 |
1995年 | 77篇 |
1994年 | 62篇 |
1993年 | 36篇 |
1992年 | 37篇 |
1991年 | 20篇 |
1990年 | 10篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1984年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有3826条查询结果,搜索用时 15 毫秒
31.
远红外织物的保健性能 总被引:5,自引:2,他引:3
远红外织物是80年代中期研究开发出的一种通过高效吸收和发射远红外线而具有改善微循环、促进血液循环等功能的新型纺织品。本文通过研究实例综述了国内外近年来对远红外织物保健性能的研究成果。 相似文献
32.
The surface structure of the oxidized and ammonia dissolved MoO3/-Al2O3 samples and the adsorption characteristics of the sulfided samples were investigated by Laser Raman Spectroscopy (LRS) and Low Temperature Infrared Spectroscopy (LTIR) techniques.It was verified that there were two kinds of coordinated unsaturated Mo sites (denoted as MoA(CUS) and MoB(CUS)) on the surface and the precursors of MoA(CUS) and MoB(CUS) were Mo(O) and Mo(T), respectively. It was also concluded that MoA(CUS) sites could adsorb NO and CO, while MoB(CUS) could adsorb CO only. The surface concentration of MoA(CUS) might be far smaller than that of MoB(CUS). 相似文献
33.
涤纶帘子线的等离子体改性 总被引:4,自引:0,他引:4
运用等离子体对涤纶帘子线进行改性处理,从而提高涤纶帘子线与橡胶的粘合性,并用X光电子能谱和红外光谱表面分析技术分析改性后的涤纶帘子线表面结构所发生的变化。 相似文献
34.
In this paper the heteropoly complexes K_n[Ga(H_20)MW_(11)O_39)]·xH_20 [M=Cu(Ⅱ), Co(Ⅱ), Cr(Ⅲ),Fe(Ⅲ), Mn(Ⅳ)] have been prepared in this laboratory firstly. The products were characterized by chemicalanalysis, ionexchange, IR, UV and X-ray powder diffraction. 相似文献
35.
36.
L. Savary J. Saussey G. Costentin M. M. Bettahar M. Gubelmann-Bonneau J. C. Lavalley 《Catalysis Today》1996,32(1-4):57-61
A VPO/TiO2 catalyst tested in the oxydehydrogenation reaction (ODH) of propane between 300 and 400°C shows satisfactory performances (up to 80% of propene selectivity at 2% of propane conversion at 300°C or 56% of propene selectivity at 9% of propane conversion at 400°C). Addition of water or pyridine in the feed gas tends to decrease the propane conversion and enhances the propene selectivity. It is shown that water increases the number of Brönsted surface acid sites by dissociative adsorption which, in turn, enhances propene selectivity at the expense of the COx selectivity. These results are in good agreement with spectroscopic IR observations performed under catalytic conditions showing that the Lewis acid sites are linked to COxformation, whereas it seems that Brönsted sites would rather be linked to propene formation. 相似文献
37.
IR spectra of ultrafine diamonds produced by different teams of researchers are studied. The effects of heating and radiation on the properties of ultrafine diamonds are studied. Quantitative assumptions on the kinetics of formation of ultrafine diamonds are made from analysis of IR spectra. 相似文献
38.
The N‐[3‐(dimethoxy‐methyl‐silanyl)‐propyl]‐N′‐ (9‐methyl‐3,9‐dioxo‐2,4,8,10‐tetraoxa‐3,9‐diphospha‐spiro[5.5]undec‐3‐yl)‐ethane‐1,2‐diamine/dimethoxy dimethyl silane copolymer (PSiN II), which simultaneously contains silicon, phosphorus, and nitrogen, is synthesized and incorporated into polypropylene (PP). The flame retardancy is evaluated by the limiting oxygen index value, which is enhanced to 29.5 from 17.4 with 20% total loading of PSiN II. The thermal degradation behavior of PP/PSiN II is investigated by thermogravimetric analysis under N2 and air. The PP/PSiN II sample degrades at 400°C for different amounts of time, and the process of degradation is studied by Fourier transform IR. The morphology of the char formed at 400°C for 10 min is investigated by scanning electron microscopy. The swollen inner structure, close, and smooth outer surface provide a much better barrier for the transfer of heat and mass during fire and good flame retardancy. The thermal stability of PP is improved by incorporation of PSiN II. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2487–2492, 2005 相似文献
39.
40.
Although wood–plastic composites have become more accepted and used in recent years and are promoted as low‐maintenance, high‐durability building products, they do experience a color change and a loss in mechanical properties with accelerated weathering. In this study, we attempted to characterize the modulus‐of‐elasticity (MOE) loss of photostabilized high‐density polyethylene (HDPE) and composites of wood flour and high‐density polyethylene (WF/HDPE) with accelerated weathering. We then examined how weathering changed the surface chemistry of the composites and looked at whether or not the surface changes were related to the MOE loss. By examining surface chemistry changes, we hoped to begin to understand what caused the weathering changes. The materials were left unstabilized or were stabilized with either an ultraviolet absorber or pigment. After 1000 and 2000 h of accelerated weathering, the samples were tested for MOE loss. Fourier transform infrared (FTIR) spectroscopy was employed to monitor carbonyl and vinyl group formation at the surface. Changes in the HDPE crystallinity were also determined with FTIR techniques. It was determined that structural changes in the samples (carbonyl group formation, terminal vinyl group formation, and crystallinity changes) could not be reliably used to predict changes in MOE with a simple linear relationship. This indicated that the effects of crosslinking, chain scission, and crystallinity changes due to ultraviolet exposure and interfacial degradation due to moisture exposure were interrelated factors for the weathering of HDPE and WF/HDPE composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2263–2273, 2004 相似文献