全文获取类型
收费全文 | 2847篇 |
免费 | 104篇 |
国内免费 | 18篇 |
专业分类
电工技术 | 38篇 |
综合类 | 65篇 |
化学工业 | 1442篇 |
金属工艺 | 57篇 |
机械仪表 | 82篇 |
建筑科学 | 103篇 |
矿业工程 | 13篇 |
能源动力 | 666篇 |
轻工业 | 112篇 |
石油天然气 | 21篇 |
武器工业 | 13篇 |
无线电 | 26篇 |
一般工业技术 | 252篇 |
冶金工业 | 39篇 |
原子能技术 | 8篇 |
自动化技术 | 32篇 |
出版年
2024年 | 20篇 |
2023年 | 50篇 |
2022年 | 96篇 |
2021年 | 83篇 |
2020年 | 96篇 |
2019年 | 92篇 |
2018年 | 71篇 |
2017年 | 90篇 |
2016年 | 62篇 |
2015年 | 70篇 |
2014年 | 173篇 |
2013年 | 175篇 |
2012年 | 151篇 |
2011年 | 233篇 |
2010年 | 173篇 |
2009年 | 183篇 |
2008年 | 151篇 |
2007年 | 157篇 |
2006年 | 118篇 |
2005年 | 99篇 |
2004年 | 92篇 |
2003年 | 99篇 |
2002年 | 55篇 |
2001年 | 43篇 |
2000年 | 58篇 |
1999年 | 52篇 |
1998年 | 46篇 |
1997年 | 41篇 |
1996年 | 39篇 |
1995年 | 36篇 |
1994年 | 14篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有2969条查询结果,搜索用时 15 毫秒
101.
The combustion-wave propagation of nickel-coated aluminum particles is studied theoretically for packing densities in the range of 10–100% of the theoretical maximum density. Emphasis is placed on the effect of packing density on the burning properties. The energy conservation equation is solved numerically and the burning rate is determined by tracking the position of the flame front. Atomic diffusion coefficients and reaction rate of isolated nickel-coated aluminum particles are input parameters to the model. The burning behaviors and combustion wave structures are dictated by the heat transfer from the flame zone to the unburned region. Five different models for the effective thermal conductivity of the mixture are employed. The impact of radiation heat transfer is also assessed. As a specific example, the case with a particle size of 79 μm is considered in detail. The burning rate remains nearly constant (<1 cm/s) up to a packing density of 60%, and then increases sharply toward the maximum value of 11.55 cm/s at a density of 100%. The Maxwell–Eucken–Bruggeman model of thermal conductivity offers the most accurate predictions of the burning rate for all loading densities. 相似文献
102.
Yen Quach Nicolas Cinausero Rodolphe Sonnier Claire Longuet Jose‐Marie Lopez‐Cuesta 《火与材料》2012,36(7):590-602
In this work, flame retardant systems comprising ammonium polyphosphate (AP423) and hydrophilic (A200) or hydrophobic (R805) nanometric silica were incorporated into PMMA. The following techniques were performed to detail the fire behaviour of the composites: mass loss cone calorimetry, pyrolysis‐combustion flow calorimetry, pyrolysis‐gas chromatography–mass spectrometry, thermogravimetric analysis, X‐ray diffraction analysis, Fourier transform infrared spectroscopy and microscopic observations. The best fire behaviour was obtained with the surface‐treated silica in the presence of AP423. The formation of a new crystalline phase from the interactions between AP423 and R805 silica and a strong barrier effect due to a layered residue were the main modes of action of this system. Moreover, we have shown that the difference between the AP423 + R805 and AP423 + A200 systems was due to poor dispersion of the silica into the PMMA matrix in the latter formulation. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
103.
Effects of hydrogen concentration on the emission and heat transfer of a premixed LPG-hydrogen flame
This paper describes an experimental study of the effect of hydrogen concentration on the emission and heat transfer characteristics of a laminar premixed LPG-hydrogen flame. The mole fraction of hydrogen in the fuel mixture was varied from 0% to 50%. The equivalence ratio of the fuel/air mixture was kept at stoichiometry and the mixture jet Reynolds number was fixed at Re = 1500 for most of the tests. The results show that upon varying hydrogen content in the fuel mixture, there is a corresponding change in the appearance, pollutant emissions and heat transfer characteristics of the flame. 相似文献
104.
The synergistic effect on the thermal decomposition and heat release rate (HRR) in particular the peak heat release rate (PHRR) of unsaturated polyester (UP) resin blended with multiwalled carbon nanotubes (MWNTs) and sepiolite nanoclay was investigated using thermal gravimetric analysis (TGA), pyrolysis combustion flow calorimetery (PCFC) and the cone calorimetery. Initial microcalorimeter findings established a synergistic effect for ternary system comprising a 10:0.5 wt% mixture of sepiolite:MWNT, respectively, which resulted in a 40% reduction in heat release capacity (HRC). This result was also confirmed within the well‐established cone calorimeter by a 50% reduction in PHRR in contrast to unfilled UP. The mechanism behind this reduction is thought to be due to the bridging of the MWNTs between the sepiolite clay needles, creating a tight protective surface layer that reduces the MLR. TGA also confirmed the advantage of such a ternary system through a 36°C shift in the onset decomposition temperature and an 11% increase in residual char. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
105.
Flame‐retardancy properties of tris(2‐hydroxyethyl) isocyanurate based charring agents on polypropylene
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Tris(2‐hydroxyethyl) isocyanurate based charring agent (TBCA) was synthesized by melt polycondensation with tris(2‐hydroxyethyl) isocyanurate (THEIC) and terephthalic acid as raw materials. It was characterized by Fourier transform infrared spectroscopy, elemental analysis, 1H‐NMR, and thermogravimetric analysis (TGA). TBCA was blended with ammonium polyphosphate (APP) to form an intumescent flame retardant (IFR) for polypropylene (PP). The charring properties of TBCA was tested by flame retardancy in the PP/APP/TBCA (PP/IFR2) composite and compared with that of the PP/APP/THEIC (PP/IFR1) composite. The results show that PP/IFR2 had lower flame‐retardant properties but better water resistance than that of the PP/IFR1 composite because PP/IFR2 could still obtain a V‐0 rating after it had been soaked in water at 70°C for 96 h, whereas PP/IFR1 could not achieve any rating after 36 h. Their combustion performance was further evaluated by a cone calorimeter test, their thermal degradation processes were studied by TGA, and the morphology of the char residue was observed by scanning electron microscopy. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41810. 相似文献
106.
研究了甲基膦酸二甲酯(DMMP)、尿素(UC)、磷酸三乙酯(TEP)单独添加及复配使用对硬质聚氨酯泡沫塑料(RPUF)阻燃性能的影响。结果表明,UC与DMMP及TEP复配是气相和凝聚相双相协同阻燃机理的复合阻燃剂;UC与DMMP,UC与TEP复配阻燃RPUF,可达到垂直燃烧分级V0级;UC/DMMP复配使用,UC和DMMP含量分别为15%和25%时,其阻燃RPUF的氧指数最高,为27.3%,阻燃性能优于UC/TEP复配阻燃RPUF;复配阻燃RPUF的压缩强度比单独填充UC体系高,呈现协同作用。 相似文献
107.
为提高聚丙烯(PP)材料的热性能和力学性能,选用膨胀型阻燃剂(IFR)对PP/乙烯-辛烯共聚物(POE)共混体系进行阻燃改性,应用双螺杆共混挤出的方法制备了PP/POE/IFR共混复合体系,对共混复合体系的阻燃性能、力学性能、膨胀炭层以及微观相结构进行了研究。结果表明,少量增容剂马来酸酐接枝POE(POE-g-MAH)的加入使得IFR颗粒的分散更加均匀、分散粒径减小,同时颗粒与聚合物基体间的结合更加紧密,从而对共混复合体系的力学和阻燃性能都有明显的提高,特别是提高冲击强度。当PP/POE/IFR/POE-g-MAH配比为80/17/20/3时,共混复合体系的平均热释放速率、热释放速率峰值、比消光面积平均值、总烟释放量较未添加增容剂的共混复合体系(PP/POE/IFR配比为80/20/20)分别下降了22.4%,14.9%,29.2%,21.8%,冲击强度提高了69.6%。 相似文献
108.
酚醛泡沫因兼具优异的保温性能和阻燃性能在工程领域得到广泛应用,但其经高温燃烧后质量残留率很低,炭层疏松、强度低,离开火焰后还易出现阴燃现象。目前有关酚醛泡沫燃烧行为的研究大多集中在如何进一步提高酚醛泡沫塑料的阻燃等级或在改善其脆性的同时不降低固有的阻燃性能,还未见关于酚醛泡沫燃烧全过程行为的综述报道。文章介绍了酚醛泡沫在明火燃烧和阴燃状态的燃烧行为,分析了影响酚醛泡沫燃烧行为的因素,并总结了现有酚醛泡沫阻燃研究的进展。目前酚醛泡沫的燃烧行为及阻燃研究主要集中在泡沫的明火燃烧,对酚醛泡沫阴燃问题的研究重视不足,缺乏针对酚醛泡沫燃烧全过程的行为和机理探究。因此,提出应加大对酚醛泡沫阴燃行为的研究投入,注重对酚醛泡沫燃烧全过程的机理探索与阻燃方案研究,设计并研发出解决酚醛泡沫燃烧全过程问题的有效途径。 相似文献
109.
110.