全文获取类型
收费全文 | 747篇 |
免费 | 22篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 304篇 |
综合类 | 24篇 |
化学工业 | 74篇 |
金属工艺 | 15篇 |
机械仪表 | 25篇 |
建筑科学 | 109篇 |
矿业工程 | 4篇 |
能源动力 | 42篇 |
轻工业 | 2篇 |
水利工程 | 4篇 |
石油天然气 | 15篇 |
武器工业 | 4篇 |
无线电 | 41篇 |
一般工业技术 | 50篇 |
冶金工业 | 25篇 |
原子能技术 | 5篇 |
自动化技术 | 27篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 12篇 |
2020年 | 22篇 |
2019年 | 13篇 |
2018年 | 7篇 |
2017年 | 20篇 |
2016年 | 28篇 |
2015年 | 22篇 |
2014年 | 37篇 |
2013年 | 23篇 |
2012年 | 42篇 |
2011年 | 60篇 |
2010年 | 33篇 |
2009年 | 31篇 |
2008年 | 45篇 |
2007年 | 46篇 |
2006年 | 36篇 |
2005年 | 39篇 |
2004年 | 26篇 |
2003年 | 36篇 |
2002年 | 30篇 |
2001年 | 25篇 |
2000年 | 18篇 |
1999年 | 19篇 |
1998年 | 30篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有770条查询结果,搜索用时 31 毫秒
761.
根据超高压直流输电系统的特点和系统绝缘配合的要求,分析了HVDC工程用交流电容器组内部的绝缘配合问题,给出了单台电容器的绝缘水平、层间绝缘水平和对地绝缘水平的计算方法和选取原则。 相似文献
762.
针对国内深水单层隔水管柱测试作业具有隔热性差、上部隔水管环空与下部油套环空连通会影响测试性和传压性等特点,研制了由合成多元醇与还原糖醇复配而成的低导热系数非水基液"一体化"保温测试液。并对该保温测试液进行了导热性、密度可调性、可泵性、流变性等性能的评价,实验结果表明,该测试液抗温可达150℃,导热系数为0.2428~0.2866 W/(m·K)),密度能在1.05~1.50 g/cm3或者1.50~1.05 g/cm3间由低到高或由高到低调节,150℃静止15 d的沉降降因子为0.50,25℃下表观黏度不大于70 mPa·s,4℃下静切力不大于3 Pa,具有较好的传压性,150℃下的3 d平均腐蚀速率为0.0369~0.0690 mm/a,岩心渗透率恢复值达95%以上;另外该保温测试液不仅环境友好,含油量为零,能满足GB 18420.1-2009《海洋石油勘探开发污染物生物毒性第1部分:分级》标准中一级海域使用要求,而且还可回收再利用,可大大节约测试成本。可以用于深水单层隔水管测试作业。 相似文献
763.
《Egyptian Journal of Petroleum》2020,29(4):257-264
In this study, Asphalt PUF (asphalt polyurethane foam) was simply prepared from the point of view of industry by in-situ polymerization of a polyoxyalkylene polyol (caster oil) and an organic isocyanate 4,4′diphenyl methane diisocyanate (MDI) into asphalt emulsion media at different NCO/OH index starting from (0.8 to 1.6). The chemical reaction is confirmed by FTIR. Surface morphology is scanned with SEM. Some of selected physical tests were performed for different insulating purposes; such as sound absorption, vibration damping, thermal conductivity, thermal cycling and water absorptivity%. The results approved that the prepared foams have an excellent sound and vibration damping properties. Furthermore, they can easily fit the uneven surface because of their good shape retention. Hence, it seems to be suitable especially for engine compartment as sound and vibration insulator. In addition, the water resistance properties of these foams are important for applications requiring long-term exposure to water, such as sealant, coating and membranes for landfills, tanks and pipes. 相似文献
764.
765.
766.
高真空多层绝热的主要影响因素 总被引:7,自引:1,他引:7
通过分析国内外的代表性文献,着重从原理及影响因素方面对高真空多层绝热的研究情况进行了论述。 相似文献
767.
《International Journal of Hydrogen Energy》2023,48(41):15600-15611
The conversion process from parahydrogen to orthohydrogen accompanies an endothermic effect. Embedment of a para-ortho hydrogen converter into the thermal insulation could enhance the thermal protection of a liquid hydrogen storage tank. A physical model was proposed to simulate the heat transfer behavior of the insulation structure that integrates a polyurethane foam, a blanket of multilayer insulation, a vapor-cooled shield, and a para-ortho hydrogen converter. The effect of the para-ortho conversion process was considered. The model was validated by experimental data and then used to investigate how the para-ortho hydrogen conversion influences the temperature distribution inside the composite insulation. It was found that a single converter improves the cooling performance most effectively if it is placed at the middle length of the venting pipe mounted on the vapor-cooled shield. Either incorporating more converters or extending the length of the vapor-cooled shield pipes brings limited further improvement. The optimum position of the vapor-cooled shield inside the multilayer insulation moves towards the cold boundary in the presence of para-ortho conversion, compared to conventional vapor-cooled shield and multilayer insulation structures. A net heat flux reduction of over 10% could be achieved when the para-ortho conversion is located at the optimal position inside the vapor-cooled shield. 相似文献
768.
《Ceramics International》2023,49(5):7515-7523
In this study, core-shell structured FeSiBCCr@SiO2&ZrO2 amorphous magnetic powder cores (AMPCs) were successfully prepared by the sol-gel method using tetraethyl orthosilicate (TEOS) and zirconium oxychloride hydrate (ZrOCl2·8H2O) as raw materials. The growth mechanism and potential chemical reactions of the SiO2&ZrO2 mixed insulation layer were analyzed by XRD, XPS and SEM?EDS. In addition, the effect of the insulation layer content on the soft magnetic properties of FeSiBCCr@SiO2&ZrO2 AMPCs was systematically investigated. The SiO2&ZrO2 insulation layer can significantly increase the resistivity, effectively improve the DC bias performance and reduce the core loss of AMPCs. S2* (1.2 mL TEOS and 1.4 g ZrOCl2·8H2O) had a minimum core loss of 2290 mW/cm3 at high frequency (50 mT, 1 MHz). It had a high effective permeability of 48.2 and a superior direct current (DC) bias performance of 77.9% at 8 kA/m. This study provides a valid method to practically produce SMPCs with high resistivity, low core loss at high frequency and excellent DC bias performance through a novel insulation coating process. 相似文献
769.
《Ceramics International》2023,49(6):8945-8951
Phase change materials (PCMs) applied in energy storage and temperature control system are important for energy conservation and environmental protection. In this work, structure-adjustable water-borne polyurethane (WPU)/boron nitride (BN) aerogels were synthesized via directional freeze-drying method, and used as supporting scaffolds to confine paraffin wax (PW) and obtain composite phase change materials. The three-dimensional (3D) porous thermal conductivity network of BN was derived by the in-situ ice crystal mound in aerogel, which endows the PW/WPU/BN composite PCM-2.5 with high thermal conductivity (0.96 W m?1 K?1) and high energy storage density (140.04 J/g). Shape-stabilized PCMs with high thermal conductivity and excellent electrical insulation prepared by the simple method have great potential for the thermal management of electronic products. 相似文献
770.
Energy demand overall the world increas相似文献