全文获取类型
收费全文 | 17173篇 |
免费 | 1390篇 |
国内免费 | 745篇 |
专业分类
电工技术 | 935篇 |
技术理论 | 3篇 |
综合类 | 1155篇 |
化学工业 | 3002篇 |
金属工艺 | 830篇 |
机械仪表 | 947篇 |
建筑科学 | 1392篇 |
矿业工程 | 458篇 |
能源动力 | 495篇 |
轻工业 | 987篇 |
水利工程 | 284篇 |
石油天然气 | 1127篇 |
武器工业 | 109篇 |
无线电 | 2034篇 |
一般工业技术 | 2435篇 |
冶金工业 | 762篇 |
原子能技术 | 180篇 |
自动化技术 | 2173篇 |
出版年
2024年 | 60篇 |
2023年 | 285篇 |
2022年 | 446篇 |
2021年 | 670篇 |
2020年 | 452篇 |
2019年 | 445篇 |
2018年 | 489篇 |
2017年 | 494篇 |
2016年 | 441篇 |
2015年 | 600篇 |
2014年 | 775篇 |
2013年 | 888篇 |
2012年 | 1031篇 |
2011年 | 1117篇 |
2010年 | 997篇 |
2009年 | 992篇 |
2008年 | 952篇 |
2007年 | 904篇 |
2006年 | 954篇 |
2005年 | 839篇 |
2004年 | 552篇 |
2003年 | 540篇 |
2002年 | 478篇 |
2001年 | 406篇 |
2000年 | 452篇 |
1999年 | 471篇 |
1998年 | 419篇 |
1997年 | 400篇 |
1996年 | 359篇 |
1995年 | 327篇 |
1994年 | 238篇 |
1993年 | 190篇 |
1992年 | 149篇 |
1991年 | 87篇 |
1990年 | 101篇 |
1989年 | 105篇 |
1988年 | 67篇 |
1987年 | 31篇 |
1986年 | 28篇 |
1985年 | 21篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
利用导电高分子聚(3,4-二氧乙基噻吩)/聚(对苯乙烯磺酸)(PEDOT/PSS)作保护剂,制备了银纳米颗粒,用UV-Vis和TEM对其进行了表征.结果表明,选择合适量的PEDOT/PSS保护剂可以得到大小分布较窄银纳米颗粒. 相似文献
92.
本文研究了硅胶纱布膜的制备方法和治疗效果。在增生性瘢痕的治疗中,硅凝胶能较快地软化和减轻瘢痕,其治疗时间要比加压疗法短。目前,对硅凝胶的作用机理尚未完全明了,但一般认为水化和封闭是治疗作用的主要基础 相似文献
93.
Jia Bing Dai Xing Yuan Zhang Jing Chao Chen Yan Bai 《Journal of Coatings Technology and Research》2007,4(3):283-288
A novel core–shell type fluorinated acrylic and siliconated polyurethane (FSiPUA) hybrid emulsion was prepared by seeded emulsion
polymerization using siliconated polyurethane (SiPU) as a seed and forming the structure with SiPU as a shell and the copolymer
of butyl acrylate (BA) with 2,2,2-trifluoroethylmethacrylate (TFEMA) as a core. SiPU was synthesized using isophorone diisocyanate
(IPDI), polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG), dihydroxybutyl-terminated polydimethylsiloxane
(PDMS), dimethylol propionic acid (DMPA), 1,6-hexanediol (HDO) and triethylamine (TEA). The contents of siloxane and fluorine
were determined according to the feed ratio. Fourier transform infrared spectroscopy (FTIR) was used to identify the chain
structure of SiPU and FSiPUA. Investigation of transmission electron microscopy (TEM) confirmed the core–shell structure of
FSiPUA emulsion and gave the particle size at about 50 nm. The measurement results of water contact angles and the solvent
absorptions in water and n-octane for cured films showed that the water and the oil repellency for FSiPUA had been improved significantly with a suitable
content of fluorine and siloxane. 相似文献
94.
乙苯脱氢氧化制苯乙烯工艺过程分析 总被引:2,自引:0,他引:2
对乙苯脱氢氧化工艺过程进行了热力学分析,表明氧化烧氢具有提高平衡转化率和能量合理利用的优点。通过一维拟均相模型模拟计算,比较了乙苯脱氢与乙苯脱氢氧化的反应效果,并由实验得到了验证。同时还讨论了乙苯实验转化率提高不多的原因。 相似文献
95.
Although carbon fiber epoxy composite materials have excellent properties for structures, the joint in composite materials often reduces the efficiency of the composite structure because the joint is often the weakest area in the composite structure.
In this paper, the effects of the adhesive thickness and the adherend surface roughness on the static and fatigue strengths of adhesively-bonded tubular polygonal lap joints have been investigated by experimental methods. The dependencies of the static and fatigue strengths on the stacking sequences of the composite adherends were observed.
From the experimental investigations, it was found that the fatigue strength of the circular adhesively-bounded joints was quite dependent on the surface roughness of the adherends and that polygonal adhesively-bonded joints had better fatigue strength characteristics than circular adhesively-bonded joints. 相似文献
In this paper, the effects of the adhesive thickness and the adherend surface roughness on the static and fatigue strengths of adhesively-bonded tubular polygonal lap joints have been investigated by experimental methods. The dependencies of the static and fatigue strengths on the stacking sequences of the composite adherends were observed.
From the experimental investigations, it was found that the fatigue strength of the circular adhesively-bounded joints was quite dependent on the surface roughness of the adherends and that polygonal adhesively-bonded joints had better fatigue strength characteristics than circular adhesively-bonded joints. 相似文献
96.
The pH mediated intra-molecular association and inter-molecular aggregation of a range of amphiphilic poly(l-lysine iso-phthalamide) polymers have been investigated in aqueous solution over a range of pH values and concentrations. The desired functionality of these novel bioresponsive amphiphilic polymers was achieved by incorporating pendant hydrophilic carboxyl groups along the polymer backbone, via the l-lysine moiety, balanced by a degree of hydrophobicity introduced via the iso-phthaloyl moiety. Incorporation of low levels of bis-functional Cy3 (poly-Cy3) and/or Cy5 dye (poly-Cy3/5 or poly-Cy5) co-monomers in the responsive polymer backbone allowed detailed probing of the pH mediated hydrophobic association using a combination of optical spectroscopic techniques. Both steady-state fluorescence spectroscopy and fluorescence lifetime measurements of poly-Cy3 revealed a conformational transition at pH 4.5. Thus, below a critical pH the polymer collapsed into a compact globular structure (hypercoil) bringing the fluorophore molecules into close proximity with one another. This resulted in a dramatic reduction in fluorescence intensity and fluorescent lifetime in the single fluorophore systems (poly-Cy3) accompanied by a red shift in the maximum emission wavelength. Observed redshifts in the emission maxima and enhancements of fluorescent lifetimes with increasing polymer concentration suggested the formation of polymer aggregates. Fluorescence resonance energy transfer (FRET) was measured in mixtures of single fluorophore containing poly-Cy3 (donor) and poly-Cy5 (acceptor) and dual fluorophore containing poly-Cy3 (donor)/Cy5 (acceptor) in an effort to distinguish between intra-molecular versus inter-molecular association. The relevance of the results with respect to potential in vivo applications (drug delivery and biodiagnostics) is discussed. 相似文献
97.
两种聚氨酯防水涂料的比较 总被引:4,自引:0,他引:4
对焦油型和非焦油水固化型聚氨酯防水涂料B组分的生产工艺、配方特点,施工操作工艺、固化时间、涂膜性能等方面进行了比较,指出新开发的非焦油型聚氨酯涂料生产周期短、能耗少、气味小,是环保型聚氨酯防水涂料。 相似文献
98.
柑桔样品中双甲脒及代射物在酸性条件下回流水解成2,4-二甲基苯胺,正己烷提取,酸,碱反复液-液分配净化,七氟丁酸酐将2,4-二甲基苯胺衍生成2,4-二甲苯七氟丁酰胺,用配有电子俘获检测器的气相色谱仪测定,外标法定量。 相似文献
99.
100.