全文获取类型
收费全文 | 2626篇 |
免费 | 189篇 |
国内免费 | 114篇 |
专业分类
电工技术 | 53篇 |
综合类 | 136篇 |
化学工业 | 594篇 |
金属工艺 | 650篇 |
机械仪表 | 194篇 |
建筑科学 | 124篇 |
矿业工程 | 76篇 |
能源动力 | 38篇 |
轻工业 | 202篇 |
水利工程 | 9篇 |
石油天然气 | 19篇 |
武器工业 | 42篇 |
无线电 | 40篇 |
一般工业技术 | 462篇 |
冶金工业 | 256篇 |
原子能技术 | 13篇 |
自动化技术 | 21篇 |
出版年
2024年 | 3篇 |
2023年 | 60篇 |
2022年 | 88篇 |
2021年 | 99篇 |
2020年 | 97篇 |
2019年 | 84篇 |
2018年 | 76篇 |
2017年 | 118篇 |
2016年 | 85篇 |
2015年 | 74篇 |
2014年 | 121篇 |
2013年 | 115篇 |
2012年 | 140篇 |
2011年 | 189篇 |
2010年 | 98篇 |
2009年 | 138篇 |
2008年 | 122篇 |
2007年 | 173篇 |
2006年 | 152篇 |
2005年 | 151篇 |
2004年 | 129篇 |
2003年 | 109篇 |
2002年 | 89篇 |
2001年 | 62篇 |
2000年 | 67篇 |
1999年 | 52篇 |
1998年 | 44篇 |
1997年 | 46篇 |
1996年 | 27篇 |
1995年 | 27篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 8篇 |
1991年 | 15篇 |
1990年 | 17篇 |
1989年 | 15篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1975年 | 1篇 |
1964年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有2929条查询结果,搜索用时 15 毫秒
1.
Xuye Wang Guopu Shi Qinggang Li Junyan Wu Hao Wu Liu Zhang Zhi Wang 《Ceramics International》2021,47(2):2280-2287
Owing to the good physicochemical compatibility and complementary mechanical properties of Ti3SiC2 and Al2O3, Ti3SiC2/Al2O3 composites are considered as ideal structural materials. However, TiC and TiSi2 typically coexist during the synthesis of Ti3SiC2/Al2O3 composites through an in-situ reaction, which adversely affects the mechanical properties of the resulting composites. In this study, Ti3SiC2/Al2O3 composites were prepared via in-situ hot pressing sintering at 1450 °C. Ge, which was used as a sintering aid, improved the purity and mechanical properties of the Ti3SiC2/Al2O3 composites. This is because Ge replaced some of the Si atoms to compensate the evaporation loss of Si to form Ti3(Si1-xGex)C2, which showed a crystal structure similar to that of Ti3SiC2. Furthermore, the molten Ge accelerated the diffusion reaction of the raw materials, increasing the overall density of the Ti3SiC2/Al2O3 composites. The optimum Ge amount for improving the mechanical properties of the composites was found to be 0.3 mol. The flexural strength, fracture toughness, and microhardness of the composite with the optimum Ge amount were 640.2 MPa, 6.57 MPa m1/2, and 16.21 GPa, respectively. The formation of Ti3(Si1-xGex)C2 was confirmed by carrying out X-ray diffraction, energy dispersive spectroscopy, and transmission electron microscopy analyses. A model crystal structure of Ti3(Si1-xGex)C2 doped with 0.3 mol Ge was established by calculating the solid solubility of Ge. 相似文献
2.
Sophie Bresch Björn Mieller Daniela Schönauer-Kamin Ralf Moos Timmy Reimann Fabien Giovannelli Torsten Rabe 《Journal of the American Ceramic Society》2021,104(2):917-927
Calcium cobaltite Ca3Co4O9, abbreviated Co349, is a promising thermoelectric material for high-temperature applications in air. Its anisotropic properties can be assigned to polycrystalline parts by texturing. Tape casting and pressure-assisted sintering (PAS) are a possible future way for a cost-effective mass-production of thermoelectric generators. This study examines the influence of pressure and dwell time during PAS at 900°C of tape-cast Co349 on texture and thermoelectric properties. Tape casting aligns lentoid Co349. PAS results in a textured Co349 microstructure with the thermoelectrically favorable ab-direction perpendicular to the pressing direction. By pressure variation during sintering, the microstructure of Co349 can be tailored either toward a maximum figure of merit as required for energy harvesting or toward a maximum power factor as required for energy harvesting. Moderate pressure of 2.5 MPa results in 25% porosity and a textured microstructure with a figure of merit of 0.13 at 700°C, two times higher than the dry-pressed, pressureless-sintered reference. A pressure of 7.5 MPa leads to 94% density and a high power factor of 326 µW/mK2 at 800°C, which is 11 times higher than the dry-pressed reference (30 MPa) from the same powder. 相似文献
3.
Sijia Huo Yujin Wang Mianyi Yao Zhikun Zhang Lei Chen Hui Gu Jiahu Ouyang Yu Zhou 《Journal of the European Ceramic Society》2021,41(11):5466-5473
Novel TiC-based composites were synthesized by reactive hot-pressing at 1800 °C for 1 h with ZrB2 addition as a sintering aid for the first time. The effects of ZrB2 contents on the phase composition, microstructure evolution, and mechanical properties were reported. Based on the reaction and solid solution coupling effects between ZrB2 and TiC, the product ZrC may be partially or completely dissolved into the TiC matrix, and then phase separation within the miscibility gap is observed to form lamellar nanostructured ZrC-rich (Zr, Ti)C. The TiC-10 mol.% ZrB2 (starting batch composition) exhibits good comprehensive mechanical properties of hardness 27.7 ± 1.3 GPa, flexural strength 659 ± 48 MPa, and fracture toughness of 6.5 ± 0.6 MPa m1/2, respectively, which reach or exceed most TiC-based composites using ceramics as sintering aids in the previous reports. 相似文献
4.
5.
《Ceramics International》2021,47(18):25689-25695
The high-temperature mechanical and dielectric properties of Si2N2O ceramics are often limited by the introduction of a sintering aid. Herein, dense Si2N2O was prepared at 1700 °C by hot-pressing oxidized amorphous Si3N4 powder without sintering additives. A homogeneous network with short-range order and a SiN3O structure was formed in the oxidized amorphous Si3N4 powder during the hot-pressing process. Si2N2O crystals preferentially nucleated at positions within the SiN3O structure and grew into rod-like and plate-like grains. Fully dense ceramics with mainly crystalline Si2N2O and some residual amorphous phases were obtained. The as-prepared Si2N2O possessed a good flexural strength of 311 ± 14.9 MPa at 1400 °C, oxidation resistance at 1500 °C, and a low dielectric loss tangent of less than 5 × 10−3 at 1000 °C. 相似文献
6.
Kongbo Sun Zhenwen Yang Ruijie Mu Shiyu Niu Ying Wang Dongpo Wang 《Journal of the European Ceramic Society》2021,41(6):3196-3206
A bulk (Hf0.2Ta0.2Zr0.2Nb0.2Ti0.2)C high-entropy ceramic (HEC) with a high density was prepared by hot pressing (HP), and through a robust joining technique, large-sized piece was fabricated. A hot-pressed carbide HEC with a single-phase and homogeneous composition was obtained at the sintering temperatures from 1800 to 1950 °C for 30 min under a pressure of 30 MPa. The influence of sintering temperature on the mechanical properties of the HEC was investigated, and the flexural and compressive strengths were reported. Additionally, the feasibility of active brazing of this HEC was studied and solid joints with high shear strength were obtained by atomic diffusion and chemical reaction at the interface, providing a key approach to fabricate complex components of HECs. 相似文献
7.
《Journal of the European Ceramic Society》2019,39(4):1428-1435
Targeting higher toughness transparent ceramics, tetragonal (3 mol % yttria) and cubic (8 mol % yttria) ZrO2 starting powder mixtures were densified by spark plasma sintering (SPS) in vacuum at 1100 °C and post hot isostatic pressing (HIP) in argon at 1100 °C. The influence of the ultra-fine microstructure and phase composition on the fracture resistance and light transmission in the visible and infra-red range was assessed. Of special interest was the influence of a thermal annealing step in air on the transparency of the SPS and SPS-HIP ceramics. 相似文献
8.
Xueqing Li Dongxu Yao Kaihui Zuo Yongfeng Xia Jinwei Yin Hanqin Liang Yu-Ping Zeng 《Journal of the European Ceramic Society》2019,39(9):2855-2861
Porous Si3N4 ceramics with monomodal and bimodal pore structure were prepared by cold isostatic pressing and freeze-casting, respectively. Both the pore structure and permeability behavior of the porous Si3N4 ceramics were tailored by altering the pressure of cold isostatic pressing and the composition and content of solvent during freeze-casting. The specimens obtained by cold isostatic pressing exhibited smaller Darcian and non-Darcian permeability than those of freeze-casted samples due to their lower open porosity, smaller pore size and higher tortuosity. On the other hand, compared with the ice-templated specimens having the same solvent volume in the ceramic slurries as them during freeze-casting, the emulsion-ice templated samples showed smaller open porosity, macropore size and Dacian permeability, but the similar non-Darcian permeability because of their larger micropores and better pore interconnectivity. 相似文献
9.
Pranesh Dayal Rifat Farzana Yingjie Zhang Gregory R. Lumpkin Rohan Holmes Gerry Triani Daniel J. Gregg 《Journal of the American Ceramic Society》2022,105(8):5359-5372
Zirconolite-rich full ceramic wasteforms designed to immobilize Pu-bearing wastes were produced via hot isostatic pressing (HIP) using stainless steel (SS) and nickel (Ni) HIP canisters. A detailed profiling of the elemental compositions of the major and minor phases over the canister–wasteform interaction zone was performed using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDS) characterization. Bulk sample analyses from regions near the center of the HIP canister were also conducted for both samples using X-ray diffraction and SEM-EDS. The sample with the Ni HIP canister showed almost no interaction zone with only minor diffusion of Ni from the inner wall of the canister into the near-surface region of the wasteform. The sample with the SS HIP canister showed ∼100–120 μm of interaction zone dominated by high-temperature Cr diffusion from canister materials to the wasteform with the Cr predominantly incorporated into the durable zirconolite phase. We also examined, for the first time, changes to the HIP canister wall thickness caused by HIPing and demonstrated that no canister wall thinning occurred. Instead, in the areas examined, the canister wall thickness was observed to increase (up to ∼20%) due to the compression occurring during the HIP cycle. Further, only sparse formation of (Cr, Mn)-rich oxide particles were noted within the HIP canister inner wall area immediately adjacent to the ceramic material, with no evidence for reverse diffusion of ceramic materials. Though the HIP canister–wasteform interaction extends to ∼120 μm when using an SS HIP canister for the system investigated, this translates to <<1 vol.% for an industrial scale HIPed wasteform. Importantly, the HIP canister–wasteform interactions did not produce any obviously less durable phases in the wasteform or had any detrimental impact on the HIP canister properties. 相似文献
10.
R.N. Maksimov V.A. Shitov V.V. Platonov A.S. Yurovskikh G. Toci B. Patrizi M. Vannini A. Pirri 《Ceramics International》2021,47(4):5168-5176
Yb3+-doped Lu2O3 nanoparticles produced by laser ablation were used to fabricate transparent ceramics by a combination of pressureless sintering in vacuum (PS) followed by a hot isostatic pressing (HIPing). The samples were subjected to various PS and HIPing conditions and the microstructure evolution and its correlation with the transmittance were investigated. Relative densities of over 97% were achieved after PS at the temperatures of 1250–1700 °C. Rapid grain growth occurred within PS and HIPing temperatures above 1500 °C leading to formation of intragranular porosity which is deleterious for optical quality. Higher transmittance (81.7% at λ = 1080 nm) and ultrafine microstructure with an average grain size of 0.35 μm were obtained by PS at 1250 °C followed by HIPing at 1400 °C for 5 h under 207 MPa. Output power of 2.02 W with a slope efficiency of 46.5% was obtained under a quasi-continuous wave end pumping at 929.4 nm. 相似文献