首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   515篇
  免费   9篇
  国内免费   30篇
综合类   10篇
化学工业   194篇
金属工艺   50篇
机械仪表   10篇
建筑科学   3篇
矿业工程   5篇
能源动力   35篇
轻工业   18篇
石油天然气   78篇
无线电   23篇
一般工业技术   113篇
冶金工业   6篇
原子能技术   3篇
自动化技术   6篇
  2024年   1篇
  2023年   13篇
  2022年   21篇
  2021年   27篇
  2020年   23篇
  2019年   24篇
  2018年   21篇
  2017年   20篇
  2016年   13篇
  2015年   20篇
  2014年   26篇
  2013年   30篇
  2012年   24篇
  2011年   48篇
  2010年   29篇
  2009年   24篇
  2008年   33篇
  2007年   28篇
  2006年   34篇
  2005年   12篇
  2004年   7篇
  2003年   24篇
  2002年   5篇
  2001年   7篇
  2000年   5篇
  1999年   5篇
  1998年   6篇
  1997年   7篇
  1996年   3篇
  1995年   4篇
  1994年   2篇
  1993年   2篇
  1992年   1篇
  1991年   3篇
  1990年   1篇
  1989年   1篇
排序方式: 共有554条查询结果,搜索用时 15 毫秒
61.
《Ceramics International》2021,47(20):28685-28697
Because the CMAS corrosion and phase transformation at elevated temperatures above 1250 °C have limited the applications of traditional YSZ, the design of novel thermal barrier materials is a hotspot. GdTaO4 is considered as a type of potential novel thermal barrier material owing to its low thermal conductivity. In this study, the mechanical and thermal properties, CMAS corrosion resistance, and the wettability of the GdTaO4 were studied and compared with that of YSZ. The results show that the coefficient of thermal expansion and hardness of GdTaO4 are 14.1 × 10−6 K−1 (1350 °C) and 534.2 Hv0.3 respectively. The thickness of CMAS reaction layer of GdTaO4 is ~30.8 μm after 24 h reaction at 1350 °C, which is thinner than that of YSZ. After corrosion reaction, the CMAS glass aggregated instead of completely disappearing or continuously extending over the surface of GdTaO4. The main reaction product is Ca2Ta2O7, and the anorthite phase may not be detected, which is similar to YTaO4. By comparison, the dense substrate of YSZ became porous and CMAS glass has disappeared after 10 h. CMAS corrosion at 1350 °C. The on-line contact angle results show that the wettability of CMAS on GdTaO4 is worse than that on YSZ at 1350 °C, while the opposite of the work of adhesion, which indicates that GdTaO4 can remove liquid CMAS more easily than YSZ TBCs during the service. Furthermore, the corrosion depth and areas of GdTaO4 are smaller than those of YSZ in the same situation. These findings suggest that GdTaO4 possesses better high-temperature properties and CMAS corrosion resistance than YSZ as a kind of potential of thermal barrier material.  相似文献   
62.
To match the reflectance profile of desert colors including dark brown, light brown and olive green in the visible‐near IR (Vis‐NIR) bands, five selected colored pigments were utilized to print woven cotton/nylon fabrics. Multi‐walled carbon nanotube particles (MWCNT's) were also added to some of the printing pastes. The reflectance of printed fabrics was evaluated by using spectrophotometric technique. The effect of adding MWCNT's, on washing; light and crocking fastness alongside with colorimetric values of printed samples was evaluated. Furthermore, the water absorption time was measured in order to determine wettability of each printed sample. The results demonstrated that the presence of MWCNT's in concentration range of 0.04–0.12 g kg?1 in printing formulations was found to cause considerable decline in Near Infrared (NIR) reflectance while a surprising increase in visible reflectance of samples was observed. Color characteristics of printed fabrics were noticeably changed even at concentrations as low as 0.12 g kg?1 MWCNTs in printing formulations. Presence of MWCNTs in printing formulations was found to cause a significant increase in wetting time of samples. Also, the results indicated that air permeability of printed samples containing MWCNT's were higher than samples printed with no MWCNTs. Phenomena imposed by MWCNT's presence on pigment printed samples showed very good fastness levels in crocking, washing and light fastness tests. In dark brown sample, adding MWCNTs to the pigment printing pastes could tune the overall reflectance in order to match the standard reflectance profile accepted for use in concealment color of desert areas. © 2013 Wiley Periodicals, Inc. Col Res Appl, 40, 93–98, 2015  相似文献   
63.
Au-Ag-Si钎料合金的初步研究   总被引:13,自引:1,他引:13  
针对目前熔点在450~500℃范围内的电子器件用钎料的空缺,通过分析Au-Ag-Si系三元相图,并根据其存在的共晶单变量线e1e2,制备了几种熔化温度在400~500℃的共晶钎料合金,并对其钎焊性和加工性能进行了初步的研究。DTA分析发现,合金的熔点在所选定的合金成分范围内随Ag含量的增加而升高。此钎料与Ni板浸润性较好;将钎料合金铸锭热轧后表明该合金作为可加工的实用钎料是合适的。同时,初步探讨了Cu元素对于Au-Ag-Si系合金的熔化特性和塑性变形能力的影响,结果表明Cu对于改善合金的加工性能和缩小固液相间距具有重要的意义。  相似文献   
64.
Objective: To evaluate parameters about wettability, water absorption or swelling of excipients in forms of powders or dosage through various methods systematically and explore its correlation with tablet disintegration.

Material and methods: The water penetration and swelling of powders with different proportions of excipients including microcrystalline cellulose (MCC), mannitol, low-substituted hydroxypropyl cellulose (L-HPC), crospolyvinylpyrrolidone (PVPP), carboxymethyl starch sodium (CMS-Na), croscarmellose sodium (CCMC-Na) and magnesium stearate (MgSt) were determined by Washburn capillary rise. Both contact angle of water on the excipient compacts and surface swelling volume were measured by sessile drop technique. Moreover, the test about water absorption and swelling of compacts was fulfilled by a modified method. Eventually, the disintegration of tablets with or without loratadine was performed according to the method described in USP.

Results and discussion: These parameters were successfully identified by the methods above, which proved that excipient wettability or swelling properties varied with the structure of excipients. For example, MgSt could improve the water uptake, while impeded tablet swelling. Furthermore, in the present study it is verified that tablet disintegration was closely related to these parameters, especially wetting rate and initial water absorption rate. The higher wetting rate of water on tablet or initial water absorption rate, the faster swelling it be, resulting in the shorter tablet disintegration time.

Conclusion: The methods utilized in the present study were feasible and effective. The disintegration of tablets did relate to these parameters, especially wetting rate and initial water absorption rate.  相似文献   

65.
Two compositions of CuPd-V system filler alloy were designed for joining the Cf/SiBCN composite. Their dynamic wettability on the Cf/SiBCN composite was studied with the sessile drop method. The CuPd-8 V alloy exhibited a contact angle of 57° after holding at 1170℃ for 30 min, whereas for CuPd-13 V alloy,a lower contact angle of 28°can be achieved after heating at 1200 ℃ for 20 min. Sound C_f/SiBCN joints were successfully produced using the latter filler alloy under the brazing condition of(1170-1230)℃for 10 min. The results showed that the active element V strongly diffused to the surface of Cf/SiBCN composite, with the formation of V_2 C/VN reaction layer. The microstructure in the central part of the joint brazed at 1200 ℃ was characterized by the V_2 C/VN particles distributing scatteringly in CuPd matrix. The corresponding joints showed the maximum three-point bend strength of 82.4 MPa at room temperature.When the testing temperature was increased to 600 0 C, the joint strength was even elevated to 108.8 MPa.Furthermore, the joints exhibited the strength of 92.4 MPa and 39.8 MPa at 800 ℃ and 900 ℃, respectively.  相似文献   
66.
Microchip has long been studied and facilitated recent investigations in multiple biomedical and material fields. The advances in functional materials triggered several leaps in the development of microchip technology. Microarray chip, benefiting from micropatterning and nucleic acid nanotechnology, was firstly introduced around 1980 and rapidly facilitated genomics, proteomics, and biodetections. In the following generation, the microfluidic chips, raised from microelectromechanical systems (MEMS) and soft lithography, are revolutionizing several areas like biology, material fabrication, energy, and environmental science. More recently, the advances in materials fabrication keep expanding the frontiers of microchip platforms, like nanoscale fabrications and flexible device manufacturing. One of the most promising platforms is the wettability-patterned materials inspired by ubiquitous natural wetting creatures such as lotus leaf, spider silk, and Stenocara beetles. The unique property of handling liquids with no sophisticated equipment potentially facilitated the current microchip platform by combining the merits of microarray and microfluidics, and in turn, benefits material communities and beyond. In this featured article, we briefly introduce the state of art technologies to fabricate wettability-patterned chips and highlight some proof-of-concept demonstration of its emerging applications in material and biomedical science. We also give an outlook on its further developments including machine-learning micropattern manufacturing technology and reveal its potentiality to revolute several scientific areas.  相似文献   
67.
The wetting of SiC plate by Y2O3/AlN additive was analysed using the sessile drop method. The wetting behaviour was observed by image capture system using a CCD camera during the heating, in argon atmosphere. The contact angle was measured as a function of temperature and time. After the wetting test the SiC plus additive samples were cut in order to observe the thickness plate cross section. The additive area and the interface between SiC and additive were analysed using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The wetting of SiC by Y2O3/AlN is influenced by the presence of a solid phase in some of the additive drops that depends mainly on the additive composition and consequently on the temperature. The measured contact angles were below 7°, reaching 0° for Y2O3/AlN additive tested at the eutectic composition, indicating a very good wettability of Y2O3/AlN on the SiC.  相似文献   
68.
Jianfen Zheng  Junxing Li 《Polymer》2006,47(20):7095-7102
Polystyrene (PS) surfaces with various morphologies have been produced by electrospinning or electrospraying, such as beads with different sizes and shapes, bead-on-string structures with different aspect ratios of the beads and fibers with different diameters and shapes. Both the solution properties and the electrospinning conditions affected the PS surface morphology obtained. The results of water contact angle (CA) measurement indicated that the surface morphology could affect the wettability distinctively. It was found that CA values of PS surfaces comprised merely fibers were in the range of 140°-150°. The CA values of PS surfaces comprised bead-on-string structures were usually about 150°. However, the CA values of PS surfaces consisted of particles could reach up to 160°, which shows a superhydrophobic property. A bilayer fibers-on-beads surface was verified to be stable and superhydrophobic.  相似文献   
69.
Al2O3-W复合材料的抗渣蚀性能   总被引:4,自引:2,他引:4  
韩兵强  李楠 《耐火材料》2003,37(1):11-13
在埋炭条件下,以金属铝粉、氧化钨及刚玉为原料,对以铝热反应为基础制备的Al2O3-W复合材料的抗渣性能进行了研究.结果表明Al2O3-W复合材料的抗渣性能随金属钨含量的增加而改善.金属钨和渣较差的润湿性是一个重要因素,而氧化铝和熔渣的反应机理和常规刚玉质材料的抗渣蚀机理一致.金属钨和渣中被还原的铁相反应生成高熔点相Fe7W6,增加了液相的粘度,抑制了熔渣的侵蚀和渗透.  相似文献   
70.
水平井堵水技术是提高水平井原油采收率的一项关键技术,通过对毛管压力方程的分析,明确了水平井润湿反转堵水的机理,建立了水平井润湿反转的模型,并运用数值模拟方法证明了润湿反转堵水的可行性。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号