全文获取类型
收费全文 | 13450篇 |
免费 | 861篇 |
国内免费 | 453篇 |
专业分类
电工技术 | 299篇 |
综合类 | 835篇 |
化学工业 | 4950篇 |
金属工艺 | 1060篇 |
机械仪表 | 1053篇 |
建筑科学 | 1144篇 |
矿业工程 | 462篇 |
能源动力 | 316篇 |
轻工业 | 601篇 |
水利工程 | 173篇 |
石油天然气 | 612篇 |
武器工业 | 108篇 |
无线电 | 768篇 |
一般工业技术 | 1421篇 |
冶金工业 | 534篇 |
原子能技术 | 153篇 |
自动化技术 | 275篇 |
出版年
2024年 | 47篇 |
2023年 | 124篇 |
2022年 | 219篇 |
2021年 | 299篇 |
2020年 | 322篇 |
2019年 | 315篇 |
2018年 | 288篇 |
2017年 | 381篇 |
2016年 | 435篇 |
2015年 | 433篇 |
2014年 | 706篇 |
2013年 | 1090篇 |
2012年 | 859篇 |
2011年 | 887篇 |
2010年 | 755篇 |
2009年 | 741篇 |
2008年 | 598篇 |
2007年 | 734篇 |
2006年 | 797篇 |
2005年 | 618篇 |
2004年 | 574篇 |
2003年 | 543篇 |
2002年 | 427篇 |
2001年 | 393篇 |
2000年 | 319篇 |
1999年 | 309篇 |
1998年 | 270篇 |
1997年 | 194篇 |
1996年 | 196篇 |
1995年 | 190篇 |
1994年 | 143篇 |
1993年 | 145篇 |
1992年 | 126篇 |
1991年 | 67篇 |
1990年 | 48篇 |
1989年 | 48篇 |
1988年 | 25篇 |
1987年 | 26篇 |
1986年 | 16篇 |
1985年 | 16篇 |
1984年 | 16篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1964年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
耐水性木材用脲醛粘合剂的研究 总被引:6,自引:1,他引:6
研究了改进胶合板用脲醛粘合剂的耐水性的方法。针对脲醛粘合剂耐水性低的原因,提出在胶液中添加碱性物质——耐水添加剂,可显著改善胶合板的耐水性,几种添加剂并用,胶合板可达一级耐水板的水平。 相似文献
132.
133.
134.
The effect of hygrothermal aging on a particle‐filled, epoxy‐based adhesive was studied using a gravimetric sorption technique. This study has explored moisture sorption characteristics as well as the associated behaviors of swelling and the depression of the glass transition temperature (Tg). We observed that the diffusion of water in this adhesive has a non‐Fickian behavior, and the depression of Tg proceeds to a definite value that is independent of the final equilibrium water content of the system. Our observations suggest that water diffuses into the polymer in a dual‐sorption mode, in which water resides in two populations. In one population, water is considered to occupy apparent free volume of the adhesive, and the second population water infiltrates polymer structure and forms hydrogen‐bonded clusters. Our results show that hygrothermal aging temperature and swelling do not alter the apparent free volume of this adhesive. We conclude that the constant value of Tg depression at saturation implies that only water in the apparent free volume is responsible for the Tg depression, whereas the swelling proceeds through the formation of hydrogen bonds in the adhesive. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1436–1444, 2003 相似文献
135.
136.
研制一种适用于低温挤出复合聚烯烃材料用的粘合剂,即在变熔融指数树脂链上,接上异氰酸酯极性基团。其复合强度大于5N/15mm,热合强度大于50N/15mm,且无毒、无异味、耐γ射线照射、工艺性能好。 相似文献
137.
天然橡胶乳液压敏胶粘剂 总被引:1,自引:0,他引:1
本文介绍了天然橡胶胶乳压敏胶的基本情况,内容包括基本组成、主要优缺点和改进方法。 相似文献
138.
无三苯CR/SBS/MMA/BA自交联鞋用胶粘剂的研制 总被引:1,自引:0,他引:1
采用复合引发剂 ,以N 羟甲基丙烯酰胺 (NAM )及丙烯酸 (AA)为功能单体 ,与CR、苯乙烯 丁二烯嵌段共聚物 (SBS)、甲基丙烯酸甲酯 (MMA)和丙烯酸丁酯 (BA)进行多元共混接枝共聚 ,再配以混合型增粘树脂 ,研制出不含苯、甲苯和二甲苯 (简称三苯 )自交联环保型鞋用胶粘剂。探讨了SBS用量、MMA/BA配比、功能单体NAM及AA用量对胶粘剂粘合性能的影响。结果表明 ,CR/SBS/MMA/BA/AA/NAM自交联型接枝胶粘剂对非极性鞋材的粘合性能明显优于CR/MMA/BA三元接枝胶和CR/SBS/MMA/BA四元接枝胶。 相似文献
139.
Although structural adhesives are becoming widespread in numerous applications, one important limitation at present is the long term behaviour of bonded assemblies under conditions of high humidity, especially at elevated temperatures. This study presents a comparison between bulk properties of a structural epoxy resin and its behaviour in a torsional joint consisting of a hollowed-out cylinder bonded to a plate—both substrates being in stainless steel. Exposure to ca. 100% relative humidity at 70°C leads to modification of the bulk properties of the polymer, notably reduction of its elastic modulus. Although this may explain some differences in behaviour of the torsional joint, premature failure is attributed to weaknesses in the interphase zone.
Auger Electron Spectroscopy (AES) has been employed to investigate both unbonded steel surfaces and fracture zones. Although prolonged exposure to water leads to a more extensive degree of (apparently) adhesive failure at the interface polymer/metal, AES has shown the presence of non-negligible quantities of carbon, attributed to residual polymer. Failure would seem to occur, at least partly, in a weak interphase of the polymer, near, but not at, the interface.
Various possible causes are evoked. For dry failure, residual polymer may be due to the topography of the metal surface and/or local modification of the adhesive during cure. In the case of aged joints, in addition there are potential effects due to swelling and differential stresses, secondary bond failure and molecular chain scission within the polymer, all provoked by the presence of water. 相似文献
Auger Electron Spectroscopy (AES) has been employed to investigate both unbonded steel surfaces and fracture zones. Although prolonged exposure to water leads to a more extensive degree of (apparently) adhesive failure at the interface polymer/metal, AES has shown the presence of non-negligible quantities of carbon, attributed to residual polymer. Failure would seem to occur, at least partly, in a weak interphase of the polymer, near, but not at, the interface.
Various possible causes are evoked. For dry failure, residual polymer may be due to the topography of the metal surface and/or local modification of the adhesive during cure. In the case of aged joints, in addition there are potential effects due to swelling and differential stresses, secondary bond failure and molecular chain scission within the polymer, all provoked by the presence of water. 相似文献
140.