全文获取类型
收费全文 | 6876篇 |
免费 | 96篇 |
国内免费 | 262篇 |
专业分类
电工技术 | 98篇 |
综合类 | 119篇 |
化学工业 | 1001篇 |
金属工艺 | 2878篇 |
机械仪表 | 433篇 |
建筑科学 | 104篇 |
矿业工程 | 90篇 |
能源动力 | 359篇 |
轻工业 | 32篇 |
水利工程 | 6篇 |
石油天然气 | 50篇 |
武器工业 | 25篇 |
无线电 | 159篇 |
一般工业技术 | 1301篇 |
冶金工业 | 442篇 |
原子能技术 | 47篇 |
自动化技术 | 90篇 |
出版年
2024年 | 1篇 |
2023年 | 51篇 |
2022年 | 89篇 |
2021年 | 158篇 |
2020年 | 170篇 |
2019年 | 112篇 |
2018年 | 118篇 |
2017年 | 124篇 |
2016年 | 111篇 |
2015年 | 156篇 |
2014年 | 306篇 |
2013年 | 321篇 |
2012年 | 381篇 |
2011年 | 617篇 |
2010年 | 375篇 |
2009年 | 396篇 |
2008年 | 372篇 |
2007年 | 443篇 |
2006年 | 411篇 |
2005年 | 349篇 |
2004年 | 289篇 |
2003年 | 295篇 |
2002年 | 275篇 |
2001年 | 244篇 |
2000年 | 187篇 |
1999年 | 182篇 |
1998年 | 150篇 |
1997年 | 130篇 |
1996年 | 111篇 |
1995年 | 90篇 |
1994年 | 72篇 |
1993年 | 41篇 |
1992年 | 32篇 |
1991年 | 19篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有7234条查询结果,搜索用时 234 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(52):22165-22179
Aluminum alloy bipolar plates have unique application potential in proton exchange membrane fuel cell (PEMFC) due to the characteristics of lightweight and low cost. However, extreme susceptibility to corrosion in PEMFC operation condition limits the application. To promote the corrosion resistance of aluminum alloy bipolar plates, a Ni–P/TiNO coating was prepared by electroless plating and closed field unbalanced magnetron sputter ion plating (CFUMSIP) technology on the 6061 Al substrate. The research results show that Ni–P interlayer improves the deposition effect of TiNO outer layer and increase the content of TiN and TiOxNy phases. Compared to Ni–P and TiNO single-layer coatings, the Ni–P/TiNO coating samples exhibited the lowest current density value of (1.10 ± 0.02) × 10?6 A·cm?2 in simulated PEMFC cathode environment. Additionally, potential cyclic polarization measurements were carried out aiming to evaluate the durability of the aluminum alloy bipolar plate during the PEMFC start-up/shut-up process. The results illustrate that the Ni–P/TiNO coating samples exhibit excellent stability and corrosion resistance. 相似文献
2.
《Ceramics International》2022,48(22):32696-32702
Aluminum nitride (AlN) ceramics are becoming cutting-edge materials for electronic information and communication. However, raw AlN hydrolyzed rapidly, and the high storage costs of this material prevent widespread application. In this study, raw AlN was modified by boric acid (H3BO3) at 30 °C to enhance hydrolysis resistance. Transmission electron microscope (TEM), X-ray diffraction (XRD), the magic angle spinning nuclear magnetic resonance (27Al-MAS-NMR and 11B-MAS-NMR), and the fourier transform infrared spectrometer (FTIR) were used to characterize the powder before and after treatment, and the mechanism of hydrolysis resistance was determined. Modification with 0.1 M boric acid did not change the crystal phase of the AlN particles. The modified powder did not hydrolyse at 90% humidity and 70° Celsius. In the presence of boric acid, a network structure of B–O–B linkages ([BOn], n = 3 or 4) formed that was connected to the AlN core via chemical bonds of B–N–Al and B–O–Al. The protective 6 – 10 nm-thick layer that formed on the surface of the AlN crystal, prevented attack by water molecules and hindered the hydrolysis of aluminium nitride. This study provides an alternative means of preparing anti-hydrolysis AlN powders. 相似文献
3.
《International Journal of Hydrogen Energy》2022,47(14):8916-8928
As a novel high energy fuel, aluminum hydride (AlH3) has great potential in the field of solid propellants because of its high hydrogen capacity, which can significantly improve the specific impulse of solid propellants. In order to improve the stability of α-AlH3, hydrochloric acid has been used to stabilize AlH3 and the stabilization mechanism has been investigated. Various characterization techniques including scanning electron microscopy, X-ray electron spectrometer, X-ray diffraction, thermal analysis, and vacuum stability test have been employed to investigate the morphology, crystal structure, thermal stability, and decomposition kinetics of raw and passivated α-AlH3. The results showed that the honeycomb-like structures could be formed on the surface of α-AlH3 after passivation. First of all, the initial decomposition temperatures of the passivated samples were slightly increased. In particular, for the optimized sample with 105 min passivation time (AlH3-105min), the initial decomposition temperature (173.4 °C) is increased by 5.6 °C. Moreover, the total decomposition time (1652 min) is improved by about 50% than that of the raw sample (1098 min). Besides, the decomposition activation energies (Ea) of passivated samples are much higher than that of the raw sample (84.8 kJ mol?1), in which the optimized sample (AlH3-105min) reaches 107.1 kJ. mol?1. The decomposition kinetics model may change from 3-D nucleation and nucleus growth model to 2-D nucleation and nucleus growth model. It demonstrates the passivated samples have a lower decomposition rate and higher thermal stability. The stabilization mechanism is as follows: removing the impurities on the surface and accelerating the hydrolysis reaction of AlH3 to generate complete and dense oxide layers. 相似文献
4.
《Ceramics International》2022,48(10):13927-13937
Long-term thermal cycling causes irreversible dimensional changes of the material, which in turn affects the reliability of precision instruments. In this paper, dimensional stability mechanisms of SiC/Al composites during thermal cycling were revealed using high-precision thermal dilatometer, XRD and spherical aberration correction transmission electron microscope (Cs-TEM). First, how the factors including dislocations, internal stress and precipitates affect the dimensional change of SiC/Al composites were separately introduced. Then, the integrated effect of these factors affecting the dimensional stability of SiC/Al composites was further discussed. Among them, the integrated effect of dislocation-internal stress in SiC/pure Al composites leads to an increase in dislocation density and average lattice constant, which leads to an increase in dimensional change. The integrated effect of dislocation-internal stress-precipitates in SiC/2024Al composites leads to a decrease in the average lattice constant and some changes in the precipitation behavior (including the type, density and lattice constant of the precipitates), which ultimately leads to a decrease in dimensional change. The dimensional change of the two types of composites was semi-quantitatively estimated. Finally, the reasons for the significantly higher dimensional stability of the SiC/2024Al composites were given. 相似文献
5.
6.
《Ceramics International》2020,46(7):8839-8844
In this work, B4C-covered zirconia-toughened alumina (ZTA) particles are prepared and oxidised at 1050 °C for different times (0, 2, 4, and 8 h) in air. The X-ray diffraction and electron probe micro-analysis results show that the covering layer is mainly composed of oxide B2O3 intermetallics, residual B4C particles, and Al18B4O33 whiskers. The scanning electron microscopy results show that the growth of Al18B4O33 whiskers on the ZTA particles enhances with increasing heat preservation time; the optimum holding time is determined to be 8 h Al2O3 in the ZTA particles diffuse into the covering layer and combine with B2O3 to form Al18B4O33 whiskers; the Al18B4O33 whiskers grow via the liquid-solid mechanism. 相似文献
7.
采用Gleeble-1500热力模拟机对铸态Ti-48Al-2Nb-2Cr合金进行高温变形热压缩试验,变形温度范围为1050~1200℃,应变速率范围为0.001~0.1s^-1,压缩变形量为60%。研究该合金高温变形温度和应变速率与流变应力之间的关系,计算了合金激活能,并建立了Ti-48Al-2Nb-2Cr合金的Arrhenius本构模型和多元线性回归的本构模型。结果表明,该合金的激活能随温度升高和应变速率增大而增大;Arrhenius本构模型的相关系数为0.98228,平均相对误差为9.97%,相对误差在10%以内的点只占62.0%;而采用多元线性回归本构模型的相关系数为0.99566,平均相对误差为4.76%,相对误差在10%以内的点占92.6%,本构精度较高。 相似文献
8.
Aluminum dross produced from aluminum industry was used to fabricate Al2O3/Al porous composites. The dross was milled for 20?h to obtain nano powder. The milled material was examined by TEM and XRD. Graphene (up to 4?wt%) was mixed with the dross and utilized to reinforce sintered composites. The milled powders were compacted then fired at various temperatures up to 700?°C. Physical properties in terms of bulk density and apparent porosity for sintered composites were tested using Archimedes method. SEM attached by energy dispersive spectrometer (EDS) was used to inspect microstructure and elemental analysis of sintered composites. Microhardness and compressive strength were also measured. Ultrasonic nondestructive technique was utilized to examine the elastic moduli. Electrical conductivity of sintered composite was also studied. During milling up to 20?h, Al2O3/Al core-shell was in-situ formed with size of 65.9 and 23.8?nm, respectively. The apparent porosity of sintered composites was improved with rising graphene percent while it decreased with increasing sintering temperature. Increasing of graphene mass percent and firing temperature led to remarkable increase in all mechanical properties and electrical conductivity. The maximum compressive strength, hardness, elastic modulus and electrical conductivity were 200?MPa, 1200?MPa, 215?GPa and 1.42?×?10?5 S/m, respectively, obtained for composite sintered at 700?°C having 4?wt% graphene. 相似文献
9.
Saionara V. Costa Nilsa T. Azana Pei Shieh Talita Mazon 《Ceramics International》2018,44(11):12174-12179
In this work, we demonstrated a novel and effective approach on the use of low-cost electrodes, an eco-friendly substrate and zinc oxide (ZnO) micro or nanorods (MRs or NRs, respectively) for building triboelectric devices (TENGs). The reported strategy focuses on using low-cost materials and fabrication processes. For the first time and without any pre-treatment, an aluminum recyclable paper from the milk carton (named ARP) was used as a substrate and TENG bottom electrode. A systematic study on the growing of ZnO structures on ARP by chemical bath deposition has been carried out. We found that the ZnO rods size, and resistivity of the TENG upper electrode considerably influence the power density of the device. Such sustainable, low-priced ZnO-based TENGs can produce up to 1.6μW/cm2 output power density when operated at 50?Hz. The fabrication of an eco-friendly nanogenerator demonstrates the possibility of manufacturing low-cost, flexible, and large-area energy harvesting devices for future applications. 相似文献
10.
Seung-Hwan Lee Jin-Myung Choi Jae-Hong Lim Jozeph Park Jin-Seong Park 《Ceramics International》2018,44(2):1978-1983
The thermoelectric properties of aluminum-doped tin oxide (ATO) thin films synthesized by thermal atomic layer deposition (ALD) were studied with respect to the aluminum concentration. The overall aluminum content in each layer was modulated by adjusting the relative number of tin oxide (SnO2) and aluminum oxide (Al2O3) growth cycles, where a sequential process involving n cycles of SnO2 growth followed by 1 cycle of Al2O3 deposition was performed (building up a super-cycle). The electrical conductivity (620 S/cm), free carrier concentration (1.23x1021 cm-3), and power factor (0.49 mW/K2m) increase until their maximum values are reached when the Al content is approximately 1.50 at% of the cations, and decrease as more Al is added in. On the other hand, the Seebeck coefficient decreases monotonically as the Al content increases up to about 2.88 at%, and begins to increase with further Al doping. Here the thermoelectric efficiency is therefore determined primarily by the free carrier concentration, while the Seebeck coefficient appears to be influenced by the overall crystal structure. 相似文献