全文获取类型
收费全文 | 1144篇 |
免费 | 173篇 |
国内免费 | 81篇 |
专业分类
电工技术 | 19篇 |
综合类 | 80篇 |
化学工业 | 400篇 |
金属工艺 | 167篇 |
机械仪表 | 18篇 |
建筑科学 | 80篇 |
矿业工程 | 50篇 |
能源动力 | 25篇 |
轻工业 | 66篇 |
水利工程 | 76篇 |
石油天然气 | 39篇 |
武器工业 | 2篇 |
无线电 | 101篇 |
一般工业技术 | 218篇 |
冶金工业 | 44篇 |
原子能技术 | 5篇 |
自动化技术 | 8篇 |
出版年
2024年 | 3篇 |
2023年 | 26篇 |
2022年 | 27篇 |
2021年 | 44篇 |
2020年 | 47篇 |
2019年 | 50篇 |
2018年 | 49篇 |
2017年 | 53篇 |
2016年 | 52篇 |
2015年 | 38篇 |
2014年 | 64篇 |
2013年 | 118篇 |
2012年 | 70篇 |
2011年 | 56篇 |
2010年 | 58篇 |
2009年 | 75篇 |
2008年 | 49篇 |
2007年 | 66篇 |
2006年 | 66篇 |
2005年 | 59篇 |
2004年 | 44篇 |
2003年 | 50篇 |
2002年 | 35篇 |
2001年 | 28篇 |
2000年 | 26篇 |
1999年 | 31篇 |
1998年 | 20篇 |
1997年 | 12篇 |
1996年 | 9篇 |
1995年 | 17篇 |
1994年 | 13篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1983年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有1398条查询结果,搜索用时 26 毫秒
61.
通过试验研究发现,晕环是由于Cu,Ag,Sn,Mn和Au等几种元素导先钎料整体沿晶界或毛细磨痕润湿母材的结果,从而提高钎料的润湿性。液态钎料与母材的性能以及在钎焊温度下相互作用情况是影响晕环形成的主要因素。 相似文献
62.
Liquid holdup and wetting efficiency were measured by means of stimulus-response (pulse-tracer) experiments in a trickle-bed reactor, packed with a commercial hydrodemetallization catalyst, and operated at 10 MPa and 330–370°C, with a superficial liquid velocity of 1.4 to 8.3 × 10?4 m/s. The total liquid holdup was obtained from the first moments, and the external wetting efficiency from the second moments, of the response curves. The dynamic holdup obtained from the total holdup lies within the range described by existing correlations, but wetting efficiency is significantly lower than literature data obtained at ambient conditions. 相似文献
63.
两步电镀铜对Cf/Cu复合材料的复合效果的影响 总被引:11,自引:1,他引:10
通过对碳纤维表面进行空气热氧化短处理,然后采用两步镀铜法对纤维表面进行电镀铜,有效的避免了普通镀铜方法中常见的“黑心”现象,使得纤维束内部单丝获得了均匀连续的镀铜层,而且纤维与镀铜层之间结合牢固.经两步镀铜处理后的碳纤维复合丝与铜基体复合后,碳纤维/铜复合材料中常见的严重纤维偏聚现象得到很大改善,获得了Cf/Cu界面结合良好,纤维分布均匀的铜基复合材料. 相似文献
64.
以孔径为200nm的阳极氧化铝(AAO)为模板,用简单的物理方法制备了生物可降解聚合物聚己内酯(PCL)的纳米管、线及其阵列结构。SEM和TEM测试结果表明:熔融法在120℃和140℃都能制得整齐的纳米管阵列结构,管径均匀,约300nm。在溶液法中,5%浓度的溶液制得了杂乱的纳米管,而10%浓度的溶液制得的是纳米线阵列,直径在200nm左右。 相似文献
65.
66.
Dynamic wetting of rolling oil on aluminum surfaces 总被引:1,自引:0,他引:1
Static and dynamic contact angles of stock oil and its solutions with additives(fatty acid, fatty alcohol, fatty methyl ester usually used in rolling aluminum) were measured on aluminum surface (Alloy 1145) by sessile drop technique on an OCA35 dynamic contact angle tester. The effect of additive on the drop spreading was investigated as well. It is shown that the drop spreads very quickly in the first 500 ms after the lubricant contacts with the aluminum surface, and then does slowly later. The dynamic contact angle decreases exponentially with time. In contrast to the stock oil, although addition of polarity additive of long chain alkyl into stock oil is able to decrease the surface tension of solutions, it weakens the wetting dynamic, which results fi'om the adsorption at the expanding solid/liquid interface. Among the same long chain polarity organic compounds used, dynamic wetting decreases in the order of fatty acid, fatty alcohol and fatty ester. The blend of fatty alcohol and fatty methyl ester can improve the oil wetting dynamics and promote the lubricant spreading. 相似文献
67.
Shuo Cao Jing Tang Yue Sun Kai Peng Yunan Gao Yanhui Zhao Chenjiang Qian Sibai Sun Hassan Ali Yuting Shao Shiyao Wu Feilong Song David A. Williams Weidong Sheng Kuijuan Jin Xiulai Xu 《Nano Research》2016,9(2):306-316
We report the direct observation of coupling between a single self-assembled InAs quantum dot and a wetting layer, based on strong diamagnetic shifts of many-body exciton states using magneto-photoluminescence spectroscopy. An extremely large positive diamagnetic coefficient is observed when an electron in the wetting layer combines with a hole in the quantum dot; the coefficient is nearly one order of magnitude larger than that of the exciton states confined in the quantum dots. Recombination of electrons with holes in a quantum dot of the coupled system leads to an unusual negative diamagnetic effect, which is five times stronger than that in a pure quantum dot system. This effect can be attributed to the expansion of the wavefunction of remaining electrons in the wetting layer or the spread of electrons in the excited states of the quantum dot to the wetting layer after recombination. In this case, the wavefunction extent of the final states in the quantum dot plane is much larger than that of the initial states because of the absence of holes in the quantum dot to attract electrons. The properties of emitted photons that depend on the large electron wavefunction extents in the wetting layer indicate that the coupling occurs between systems of different dimensionality, which is also verified from the results obtained by applying a magnetic field in different configurations. This study paves a new way to observe hybrid states with zero- and two-dimensional structures, which could be useful for investigating the Kondo physics and implementing spin-based solid-state quantum information processing. 相似文献
68.
《Journal of Adhesion Science and Technology》2013,27(1):817-827
Polyolefin films were surface-modified by different methods to improve the wetting and adhesion of water-borne printing inks. Polyethylene (PE) films were treated with corona at various energy levels. Surface-modified PE films were characterized by contact angle measurements and electron spectroscopy for chemical analysis (ESCA). Good wetting was already achieved with treatment at a lower energy level. Various degrees of adhesion were obtained at various degrees of treatment. A hydrophilic monomer, 2-hydroxyethylmethacrylate (HEMA), was polymerized onto the surfaces of polypropylene (PP) with radiation-induced grafting, which was carried out at two different radiation doses. In both cases, a thick, visible layer of polyHEMA was formed on the surface of PP, and satisfactory wetting was already achieved at lower radiation doses. Scanning electron microscopy (SEM) showed that different degrees of roughness were achieved at various radiation doses. Like the case of corona-treated PE, different degrees of adhesion were obtained at different degrees of surface treatment. This study shows that improved wetting alone is not satisfactory for good practical adhesion', regardless of the surface modification method used. 相似文献
69.
《Journal of Adhesion Science and Technology》2013,27(8-9):1169-1180
Abstract A comparative study of wetting transitions on porous and post-built polymer surfaces is reported. The transitions were observed under vibration of droplets of different volumes deposited on the surfaces possessing controlled roughness. Initial wetting states were identified as the Cassie air-trapping (‘Fakir’) state for porous and the Wenzel state for post-built relief, whereas the final wetting state was the Cassie impregnating one for both kinds of surfaces. For both porous and post-built surfaces, wetting transitions occurred under constant force acting on a unit length of the three-phase (triple) line. Wetting transitions for both porous and post-built surfaces start from the triple line. 相似文献
70.
《Drying Technology》2013,31(3):413-438
Abstract Although a detailed mathematical model incorporating all physical mechanisms of moisture and heat transfer in the material would yield valuable design information, it is not feasible to do this on a routine basis for the design of dryers. A simple liquid diffusion model was developed in the present study to quantitatively assess the influence of various operating parameters of engineering interest in drying of heat-sensitive materials. Heat of wetting, temperature, and moisture dependent effective diffusivity and thermal conductivity, changes in product density and drying-induced ideal shrinkage of the product are considered in this model. The effects of combining convection with conduction, radiation, and volumetric heating using a microwave field are simulated in view of the increasing interest in multimode heat input drying processes. Numerical results are reported on drying of potato slices to demonstrate how the moisture and temperature profiles as well as drying performance are affected by multi-mode heat input. Effects of key parameters e.g., drying air velocity, temperature, relative humidity, and product thickness are computed and discussed. 相似文献