全文获取类型
收费全文 | 10696篇 |
免费 | 1157篇 |
国内免费 | 174篇 |
专业分类
电工技术 | 282篇 |
综合类 | 513篇 |
化学工业 | 7288篇 |
金属工艺 | 207篇 |
机械仪表 | 484篇 |
建筑科学 | 841篇 |
矿业工程 | 175篇 |
能源动力 | 73篇 |
轻工业 | 196篇 |
水利工程 | 151篇 |
石油天然气 | 451篇 |
武器工业 | 51篇 |
无线电 | 63篇 |
一般工业技术 | 1019篇 |
冶金工业 | 93篇 |
原子能技术 | 45篇 |
自动化技术 | 95篇 |
出版年
2024年 | 48篇 |
2023年 | 112篇 |
2022年 | 233篇 |
2021年 | 326篇 |
2020年 | 276篇 |
2019年 | 190篇 |
2018年 | 275篇 |
2017年 | 309篇 |
2016年 | 344篇 |
2015年 | 335篇 |
2014年 | 676篇 |
2013年 | 690篇 |
2012年 | 785篇 |
2011年 | 696篇 |
2010年 | 538篇 |
2009年 | 567篇 |
2008年 | 427篇 |
2007年 | 607篇 |
2006年 | 594篇 |
2005年 | 540篇 |
2004年 | 431篇 |
2003年 | 459篇 |
2002年 | 411篇 |
2001年 | 339篇 |
2000年 | 301篇 |
1999年 | 282篇 |
1998年 | 250篇 |
1997年 | 177篇 |
1996年 | 180篇 |
1995年 | 141篇 |
1994年 | 113篇 |
1993年 | 75篇 |
1992年 | 70篇 |
1991年 | 62篇 |
1990年 | 48篇 |
1989年 | 42篇 |
1988年 | 15篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 21篇 |
1984年 | 14篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1978年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
Ground rubber powder (GRP) and devulcanized rubber (Dev.R) waste through a continuous shear‐flow reaction were used as fillers for virgin natural rubber. A Horikx plot and the gel fraction proved that both main‐chain scission and crosslink scission occurred during the devulcanization. The cure characteristics, swelling behavior, crosslink density, and mechanical properties were studied. GRP and Dev.R, generated from passenger car and light truck tires, showed applicable mechanical properties in the new rubber compounds, and the compounds containing Dev.R demonstrated better properties than those containing GRP. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 208–217, 2005 相似文献
44.
45.
在选择三元共聚尼龙(PA)、聚氯乙烯(PVC)、丁腈橡胶(NBR)为主体材料,制备PA/PVC/NBR(10/30/60)三元共混弹性体的工作基础上,进一步探讨了填料品种和用量,共混温度,加料顺序等因素PA/PVC/NBR三元共混弹性体的影响。试验结果表明:在PA/PVC/NBR(10/30/60)共混体系中,补强型填料的补强效果优于非补强型的填料,6种填料补强效果依次是:快压出炭黑>半补强炭黑>白炭黑>活性重质,CaCO3>陶土>滑石粉,快压出炭黑的适宜用量是20-50份。在制备PA/PVC/NBR三元共混物时,适宜的共混温度是122-140℃,并且采用二段法混工艺制得的共混物性能优于采用一段法共混工艺。 相似文献
46.
Joo Batista A. Silva Regina C. M. de Paula Judith P. A. Feitosa Eduardo Diogo Gurgel‐Filho Claudio Maniglia‐Ferreira Francisco Jose de Souza Filho 《应用聚合物科学杂志》2006,100(5):4082-4088
Gutta‐percha cone is the most widely used material for root canal filling. The in vivo aging of this cone focus on the degradation of its main organic component, trans‐1,4‐polyisoprene, was studied. Aged cones (25 samples) from 2 to 30 years of root canal filling were extracted from different patients in the occasion of retreatment by mechanical way. The information about the aging time was given by the patients. Gel‐permeation chromatography (GPC) and infrared spectroscopy (FTIR) were the analytical techniques used. Polyisoprene degrades with time of aging, but in a slow process. Decrease in polymer molar mass from 5.7 × 105 to 1.7 × 105 g/mol was observed in polyisoprene from cone after 30 years of root canal filling and inside a noninfected tooth. In tooth with caries and periodontal infection, the decrease in molar mass is higher (4.6 × 104 g/mol in cone with 10 years of aging). The production of carbonyl and hydroxyl groups in the aged material indicates that the process is oxidative, even in closed teeth. In these cases, the oxygen could be provided from tissue fluid. The degradation mechanism is complex and depends on many factors, besides time of root canal filling. The dental problem caused by the aging could be the production and migration of cytotoxic substances to periodontal ligament and the reduction on the canal sealing property due to the polymer weight loss. Both of them could contribute to the root canal treatment failure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:4082–4088, 2006 相似文献
47.
介绍了FR-1型粘合剂用于氟橡胶、硅橡胶、三元乙丙橡胶与金属热硫化粘着,制作橡胶金属复合制品的情况。金属骨架经喷砂或表面化学处理并用溶剂清洗之后,涂FR—1型粘合剂,经预烘干后与橡胶进行热硫化粘着,效果良好。 相似文献
48.
49.
50.