全文获取类型
收费全文 | 30279篇 |
免费 | 2317篇 |
国内免费 | 1115篇 |
专业分类
电工技术 | 1520篇 |
技术理论 | 2篇 |
综合类 | 1748篇 |
化学工业 | 5086篇 |
金属工艺 | 1847篇 |
机械仪表 | 2058篇 |
建筑科学 | 2402篇 |
矿业工程 | 1017篇 |
能源动力 | 806篇 |
轻工业 | 1768篇 |
水利工程 | 550篇 |
石油天然气 | 2049篇 |
武器工业 | 221篇 |
无线电 | 3227篇 |
一般工业技术 | 3701篇 |
冶金工业 | 1582篇 |
原子能技术 | 359篇 |
自动化技术 | 3768篇 |
出版年
2024年 | 55篇 |
2023年 | 524篇 |
2022年 | 722篇 |
2021年 | 1213篇 |
2020年 | 1020篇 |
2019年 | 778篇 |
2018年 | 978篇 |
2017年 | 980篇 |
2016年 | 926篇 |
2015年 | 1163篇 |
2014年 | 1460篇 |
2013年 | 1824篇 |
2012年 | 1918篇 |
2011年 | 1952篇 |
2010年 | 1769篇 |
2009年 | 1716篇 |
2008年 | 1601篇 |
2007年 | 1571篇 |
2006年 | 1688篇 |
2005年 | 1406篇 |
2004年 | 905篇 |
2003年 | 854篇 |
2002年 | 760篇 |
2001年 | 638篇 |
2000年 | 673篇 |
1999年 | 808篇 |
1998年 | 691篇 |
1997年 | 621篇 |
1996年 | 559篇 |
1995年 | 468篇 |
1994年 | 357篇 |
1993年 | 263篇 |
1992年 | 205篇 |
1991年 | 157篇 |
1990年 | 116篇 |
1989年 | 98篇 |
1988年 | 82篇 |
1987年 | 48篇 |
1986年 | 49篇 |
1985年 | 22篇 |
1984年 | 21篇 |
1983年 | 14篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 2篇 |
1966年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
71.
Pengcheng Zhao Yu Xiang Yan Xu Yuehua Wen Wenfeng Zhang Xiayu Zhu Meng Li Zhaoqing Jin Hai Ming Gaoping Cao 《Ceramics International》2018,44(8):9105-9111
Garnet-type Li5La3Ta2O12 (LLTaO) solid electrolyte is a potential candidate component for future all-solid-state batteries due to its extraordinary stability against the reaction with molten lithium. In contrast with traditional cold isostatic pressing (CIP) method, which generally pursues ultra-high pressure, this paper tries to enhance the density and ionic conductivity of LLTaO by self-consolidation strategy without the assistance of any pressing operations. A LLTaO bulk with a relative density of 95% is obtained. SEM images reveal that the bulk sample is assembled by large dense particles in size of tens of microns indicating that the interstitial space among the particles has been dramatically minimized. Accordingly, the total ionic conductivity and the bulk ionic conductivity at 30?°C are promoted up about one order of magnitude higher to 2.63?× 10?5 S?cm?1 and 1.41?×?10?4 S?cm?1, respectively. Moreover, the lithium ionic migration network in the crystalline unit cell of LLTaO is first explored from its assembled way. A hexagon-like basic unit with tetrahedral Li1 joint sites and Li1- - Li1 edges is identified. The tetrahedral Li1 sites act as crucial junctions for the transportation of lithium ions. This work would significantly stimulate the development of LLTaO electrolyte membrane technology. 相似文献
72.
Zhentao Wang Yanwei Zeng Chuanming Li Zhupeng Ye Liangliang Cao Yuan Zhang 《Ceramics International》2018,44(9):10328-10334
Gd3+ and Fe3+ co-doped cerium oxide electrolytes, Ce0.9Gd0.1‐xFexO2-δ (x?=?0.00, 0.01, 0.03, 0.05, 0.07, 0.10), were prepared by co-precipitation for ultrafine precursor powders and sintering for densified ceramic pellets. The crystal and microscopic structures were characterized by XRD, FESEM and Raman spectroscopy and their electrical properties were studied by AC impedance spectroscopy and the measurement of single cell's outputs. In comparison with Ce0.9Gd0.1O1.95, the ceramic pellets of Ce0.9Gd0.1‐xFexO2-δ with a relative density of 95% can be obtained after sintered at 1000?°C for 5?h, showing a remarkably enhanced sintering performance with a sintering temperature reduction of 500?°C, which might be ascribed to the highly activated migration of constituent species in the cerium oxide lattice doped with Gd3+ and Fe3+ions. Moreover, the electrical conductivity of Ce0.9Gd0.1‐xFexO2-δ can be significantly enhanced depending on the mole fraction x, with Ce0.9Gd0.07Fe0.03O1.95 exhibiting the highest electrical conductivity of 38 mS/cm at 800?°C, about 36% higher than that of Ce0.9Gd0.1O1.95 electrolyte sintered at 1500?°C for 5?h. So, The Gd3+ and Fe3+ co-doped cerium oxide would be an excellent candidate electrolyte for ILT SOFCs due to its prominent sintering performance and enhanced electrical conductivity. 相似文献
73.
Yang Yang Hua Hao Lin Zhang Cheng Chen Zhiping Luo Zhen Liu Zhonghua Yao Minghe Cao Hanxing Liu 《Ceramics International》2018,44(10):11109-11115
BaTi1-xCaxO3-x [BTC100x] ceramics were synthesized via solid-state reaction method. Effect of Ca substitution on the structure, electrical and dielectric properties of BTC100x ceramics was systematically investigated. Calcined BTC100x powders were in tetragonal phase when x?≤?0.01, whereas transformed to cubic at x?>?0.01. Additionally, the diffraction peak (200) shifted to lower angles with increasing x, indicating increased unit cell volume. Meanwhile, Ba0.97Ca0.03TiO3 [BC3T] ceramic was prepared and studied, to compare with BaTi0.97Ca0.03O2.97 (BTC3). It was found that pure BaTiO3 [BT] and BC3T ceramics had the similar structural and dielectric properties, whereas BTC3 ceramic showed much difference,XRD patterns, Raman spectrum, impedance spectra and dielectric-temperature spectra provided strong evidence of Ca2+ substitution at Ti site in BT lattice. Finally, BTC100x ceramics were produced and dielectric properties were investigated. With increasing x, the Curie temperature decreased from 128?°C (BT) to 42?°C (BTC5). 相似文献
74.
Bao-Jia Li Yong-Ying Wang Li-Jing Huang Hai-Di Cao Qinghua Wang Nai-Fei Ren Hongtao Ding 《Ceramics International》2018,44(18):22225-22234
An ultrasonic-vibration-assisted laser annealing method was developed to enhance the performance of fluorine-doped tin oxide (FTO) thin films. The influences of ultrasonic vibration, laser scan line overlapping rate (LOR) and laser spot overlapping rate (SOR) on surface morphology, FTO layer thickness, RMS roughness, crystal structure and photoelectric properties of the FTO films were investigated. The results indicated that the presence of ultrasonic vibration during laser annealing could significantly enhance the film compactness, and using moderate LOR and SOR values resulted in significantly decreased FTO layer thicknesses and RMS roughnesses as well as slightly increased crystallite sizes, thus yielding significantly improved optical transmittance values and slightly enhanced electrical conductivity values. It was found that the optimal LOR and SOR values for ultrasonic-vibration-assisted laser annealing of the FTO films were 80% and 90%, respectively. The as-obtained film possessed the best overall photoelectric property with an average transmittance (400–800?nm) of 85.9%, a sheet resistance of 8.7?Ω/sq and a figure of merit of 2.51?×?10–2 Ω–1. This work may be of great significance in terms of performance optimization of transparent conducting oxide (TCO) thin films. 相似文献
75.
The in-situ fabrication of an electron-blocking layer between the Ba-containing anode and the ceria-based electrolyte is an effective approach in suppressing the internal electronic leakage in ceria-based solid oxide fuel cell (SOFC). To improve the thickness of the electron-blocking layer and to research the effect of the layer thickness on the improvement of SOFC, a Ba-containing compound (0.6NiO-0.4BaZr0.1Ce0.7Y0.2O3-δ) modified by Y stabilized zirconia (YSZ) was employed as a composite anode in this research. SEM analyses demonstrated that the thickness of the interlayer can be simply controlled by regulating the proportion of YSZ at anode. The in-situ formed interlayer in the cell with the anode modified by 20?mol% YSZ possesses a thickness of 0.9?µm which is more suitable for the cell achieving an enhanced performance. 相似文献
76.
ZrB2–SiC composite ceramics with different compositions (20 and 60?vol% ZrB2–SiC, 20ZS and 60 ZS, respectively) were prepared. Wear tests were conducted on the obtained ceramics in multiple distances using ball-on-flat tribotester. Volume loss and cross-sectional profiles of samples were measured by three–dimensional (3D) profilometer to study the onset of track wear damages. Pressure–depth curves and hardness were measured by indentation to investigate defects produced in the tribo-film by the debris. The debris of 20ZS was found to be joined to the tribo-film and accumulated with distance, shifting from microcrack (<10,000 cycles) to abrasive wear (50,000 cycles). Compared to 20ZS, lower debris accumulation of 60ZS resulted in better wear resistance, leading to thinner and more stable non-substrate regions for this sample. These differences between both samples basically resulted from different particle sizes. Fine grains were easily pulled out in the experiment, resulting in abrasive wear of the specimen. While transgranular fracture of grains and the pinning led to larger grains with less debris, the damage mode remained transgranular fracture. 相似文献
77.
Pengcheng Zhao Yu Xiang Yuehua Wen Meng Li Xiayu Zhu Songtong Zhao Zhaoqing Jin Hai Ming Gaoping Cao 《Journal of the European Ceramic Society》2018,38(16):5454-5462
Garnet-like Li7La3Zr2O12 electrolytes with Nb doping are synthesized by self-consolidation method. Different from conventional methods such as cold or hot isostatic pressing, not any pressing assistance is employed throughout the preparation process. Although the preparation process is dramatically simplified, both density and ionic conductivity of the obtained samples are enhanced. Nb-doped content plays a key role in the sintering of the packed precursor powders and in the structure stabilization of the obtained bulk samples. The optimized 0.60?mol Nb-doped sample with relative density of 94%, fine particle boundaries, and solitary cubic structure possesses the maximum total ionic conductivity of 5.22?×?10?4?S?cm?1 at 30?°C, which is comparable to the highest reported value of the samples prepared by conventional pressing methods. This work verifies that self-consolidation strategy is effective, reliable, and productive for the preparation of cubic Li7La3Zr2O12 electrolyte, which would significantly facilitate the development of ceramic electrolyte membrane technology. 相似文献
78.
Jinshuang Wang Junbin Sun Qiangshan Jing Bing Liu Hao Zhang Jieyan Yuan Shujuan Dong Xin Zhou Xueqiang Cao 《Journal of the European Ceramic Society》2018,38(7):2841-2850
The properties of ZrO2 co-stabilized by CeO2 and TiO2 ceramic bulks were investigated for potential thermal barrier coating (TBC) applications. Results showed that the (Ce0.15Tix)Zr0.85-xO7 (x?=?0.05, 0.10, 0.15) compositions with single tetragonal phase were more stable than the traditional 8YSZ at 1573?K. These compositions also showed a large thermal expansion coefficient (TEC) and a high fracture toughness, which were comparable to those of YSZ. However, the phase stability, fracture toughness and sintering resistance of the CeO2-TiO2-ZrO2 system showed a decline tendency with the increase of TiO2 content. The TEC of the ceramic bulks decreased with increase of TiO2 content as well because the crystal energy was enhanced with increasing substitution of Zr4+ by smaller Ti4+. The (Ce0.15Ti0.05)Zr0.8O2 had the best comprehensive properties among the (Ce0.15Tix)Zr0.85-xO2 compositions as well as a low thermal conductivity. Therefore, it can be explored as a TBC candidate material for high-temperature applications. 相似文献
79.
Isothermal crystallization kinetics and subsequent melting behavior of β‐nucleated isotactic polypropylene/graphene oxide composites with different ordered structure 下载免费PDF全文
Yansong Yu Fangxinyu Zeng Jinyao Chen Jian Kang Feng Yang Ya Cao Ming Xiang 《Polymer International》2018,67(9):1212-1220
The effects of ordered structure on isothermal crystallization kinetics and subsequent melting behavior of β‐nucleated isotactic polypropylene/graphene oxide (iPP/GO) composites were studied using differential scanning calorimetry. The ordered structure status was controlled by tuning the fusion temperature (Tf). The results showed that depending on the variation of crystallization rate, the whole Tf range could be divided into three regions: Region I (Tf > 179 °C), Region II (170 °C ≤ Tf ≤ 179 °C) and Region III (Tf < 170 °C). As Tf decreased from Region I to Region III, the crystallization rate would increase substantially at two transition points, due to the variation of the ordered structure status. Calculation of Avrami exponent n indicated that the ordered structure induced the formation of two‐dimensional growing crystallites rather than three‐dimensional growing crystallites. Moreover, in the case of isothermal crystallization, the ordered structure effect (OSE) can also greatly increase the relative content of β‐phase (βc). In Region II, OSE took place, resulting in evident increase of βc, achieving 92.4% at maximum. The variation of the isothermal crystallization temperature (Tiso) had little influence on the Tf range (Region II) of the OSE. The higher Tf in Region II was more favorable for the formation of higher βc. The ordered structure was favorable for the improvement of the nucleating efficiency of β‐nucleating agent (β‐NE), and was more effective for the improvement of lower β‐NE. © 2018 Society of Chemical Industry 相似文献