全文获取类型
收费全文 | 10438篇 |
免费 | 678篇 |
国内免费 | 272篇 |
学科分类
工业技术 | 11388篇 |
出版年
2024年 | 21篇 |
2023年 | 188篇 |
2022年 | 177篇 |
2021年 | 326篇 |
2020年 | 335篇 |
2019年 | 303篇 |
2018年 | 309篇 |
2017年 | 265篇 |
2016年 | 248篇 |
2015年 | 264篇 |
2014年 | 535篇 |
2013年 | 617篇 |
2012年 | 647篇 |
2011年 | 822篇 |
2010年 | 731篇 |
2009年 | 617篇 |
2008年 | 649篇 |
2007年 | 680篇 |
2006年 | 730篇 |
2005年 | 586篇 |
2004年 | 530篇 |
2003年 | 363篇 |
2002年 | 241篇 |
2001年 | 185篇 |
2000年 | 187篇 |
1999年 | 189篇 |
1998年 | 176篇 |
1997年 | 112篇 |
1996年 | 81篇 |
1995年 | 54篇 |
1994年 | 46篇 |
1993年 | 37篇 |
1992年 | 31篇 |
1991年 | 31篇 |
1990年 | 21篇 |
1989年 | 20篇 |
1988年 | 12篇 |
1987年 | 4篇 |
1986年 | 9篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1980年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
81.
A unique electrochemical technique, namely continuous noise resistance calculation (CNRC), was used to obtain electrochemical kinetic information from the formation process of chromate conversion coatings (CCC) on aluminium electrodes. It was found that the noise resistance (Rn) of aluminium electrodes remained almost unchanged during electrodes' immersion in a chromate containing acidic solution where the CCC films were supposed to form rapidly. This result indicates that the formation of CCC was associated with continuous corrosion of the aluminium electrodes and that the CCC films formed on aluminium surface were not intact barrier films, but most likely porous layers. The CCCs became protective only after they were aged in the environment. Based on these findings, the formation and inhibition mechanisms of CCC have been discussed. 相似文献
82.
Jaspreet S. Gandhi William J. van Ooij 《Journal of Materials Engineering and Performance》2004,13(4):475-480
Organofunctional silanes recently have emerged as outstanding, environmentally friendly corrosion protectors for metal substrates,
compared with conventional chromate treatments. A simple immersion technique is typically used to coat the metal surface with
silane films. However, the thickness and uniformity of the films are uncontrolled in this process. This paper proposes a new
deposition technique for the silane films on the metal surface, i.e., by electrodeposition. Hydrolyzed silanes are water-soluble,
ionized molecules, so they can be deposited on metals by electrodeposition. Various combinations of silane mixtures were tested
at different voltages, pH values, bath concentrations, and exposure times on panels of alloy aluminum and mirror-polished
ferro-plate. The surface structure was characterized by scanning electron microscopy (SEM) and ellipsometry. The resistance
of the film to corrosion was investigated by direct current (DC) polarization and electrochemical impedance spectroscopy (EIS)
techniques. Electrodeposition results in a more organized and uniform film with fewer pores, compared with immersed or dipped
films.
This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September
15–17, 2003, in Indianapolis, Indiana, and appears on pp. 320–26 of the Proceedings. 相似文献
83.
The oxidation behavior in air at 1473 K, and sulfidation behavior in a H2S–H2 gas mixture with a sulfur partial pressure of 10–2 Pa at 973 K of Al–Re coated CMSX-4 were studied. Investigation on the sulfidation behavior of the Re-coated CMSX-4 was carried out in a H2S–H2 gas mixture with a sulfur partial pressure of 10–2 Pa at 973 K. The experimental results show that a Re-rich alloy layer was formed between an -Al2O3 layer and the inner concentration zone of Ta and Ti for the CMSX-4 single crystal alloy with an Al–Re coating after oxidation. The Re-rich alloy layer containing Cr, W, Ni, Co, and Mo effectively inhibited the outward diffusion of alloying elements and the inward diffusion of Al. The Al/Re-coated CMSX-4 single crystal alloy had excellent sulfidation resistance; the Re-rich alloy layer, containing W, Ti, Ta, and Mo, which formed during the sulfidation process and located between the alumina scale and the CMSX-4 base alloy, plays a role in inhibiting the outward diffusion of alloying elements. The sulfidation resistance of CMSX-4 single-crystal alloy is greatly improved by a Re coating on the CMSX-4 alloy surface; this is attributed to a Re–Cr–W alloy layer that retarded the outward diffusion of cations and the oxide layer containing Ta, Ti, and Al, which inhibited the inward penetration of sulfur. 相似文献
84.
CrSiN coatings with different Si concentration (Si/(Cr + Si) ratio: 0, 3.7, 11.7, 20%) were deposited on stainless steel substrates using a closed field unbalanced magnetron sputtering (CFUBM) system. The variation in the microstructure of the films with the Si concentration was measured by XRD. The corrosion behavior of the CrSiN coatings in a deaerated 3.5% NaCl solution was investigated by potentiodynamic tests, electrochemical impedance spectroscopy (EIS) and surface analyses. The microstructure of the CrSiN film was found to depend on the Si concentration. The results of the potentiodynamic polarization tests showed that the corrosion current density and porosity decreased with increasing Si/(Cr + Si) ratio. The EIS measurements showed that the corrosion resistance of the Si-bearing CrN was improved by the phase transformation of the film, which led to an increase in the pore resistance and charge transfer resistance. The Si-bearing CrN possesses the best corrosion resistance at a Si/(Cr + Si) ratio of 20%, measured by the maximization of the pore resistance and charge transfer resistance. 相似文献
85.
86.
采用等离子喷涂方法在LY12铝上制备了Ta/W/Sn复合涂层。研究了各种工艺参数对涂层材料熔化程度和沉积效率的影响。采用扫描电子显微镜观察了复合涂层的表面及界面,精密机械天平称量涂层的增重,力学拉伸机测量涂层的抗拉结合强度,能谱和化学方法分析涂层的化学成分。结果表明,等离子喷涂工艺可以制作组织致密,厚度均匀的Ta/W/Sn复合涂层;喷涂功率和送粉速率对材料的熔化状态影响较大,在特定喷距范围内喷距的影响则较小。 相似文献
87.
Molds made of gray cast iron for casting pig iron ingots are subjected to severe temperature fluctuations. The main life-
limiting factor for mold damage is the formation of surface cracks arising from thermal fa-tigue. Various flame and plasma
sprayed coatings were investigated to extend the life of these molds. Coating materials studied include plasma sprayed ceramic
coatings with bond coats as well as flame sprayed oxidation- resistant alloy powders. The results of cyclic furnace tests
from room temperature to 1100 °C in air, simulating the thermal cycle in casting, indicated that failure occurred along the
interface between the bond coat and the gray iron substrate because of iron oxidation, and not at the interface between the
ceramic top coat-ing and the bond coating for a superalloy substrate. The field test results indicated that plasma sprayed
alumina coatings with 200 μm top coating thickness are the most promising materials for pig iron casting. 相似文献
88.
Austenitic Mn-Al alloys (20–32 W/O Mn, 7–10 Al, 2–3 Si, 1C) were found to have satisfactory oxidation resistance up to 950°C under isothermal conditions in air. Surface enrichment of aluminum is a necessary condition for obtaining an almost pure alumina scale for uses at higher temperatures. Four different Mn-steels were Al-coated by the Capuano electroplating process. In all the steels there was an increase in the hot-oxidation resistance. The best results were obtained with steels containing both Al and Si, and this for temperatures up to 1100°C. No spalling was noticed during rapid cooling of the test pieces. Silicon was found to act as a diffusion barrier to outward iron diffusion. It appears that there is formation of a pure, thin film of alumina from the matrix which interacts with the aluminum diffusing from the superimposed, coating for the formation of good bonds. 相似文献
89.
90.