全文获取类型
收费全文 | 59651篇 |
免费 | 5824篇 |
国内免费 | 3649篇 |
专业分类
电工技术 | 1373篇 |
技术理论 | 1篇 |
综合类 | 4114篇 |
化学工业 | 9092篇 |
金属工艺 | 7437篇 |
机械仪表 | 4394篇 |
建筑科学 | 6455篇 |
矿业工程 | 790篇 |
能源动力 | 1804篇 |
轻工业 | 2617篇 |
水利工程 | 736篇 |
石油天然气 | 1230篇 |
武器工业 | 425篇 |
无线电 | 9440篇 |
一般工业技术 | 12421篇 |
冶金工业 | 2198篇 |
原子能技术 | 3163篇 |
自动化技术 | 1434篇 |
出版年
2024年 | 107篇 |
2023年 | 974篇 |
2022年 | 1376篇 |
2021年 | 1837篇 |
2020年 | 1953篇 |
2019年 | 1886篇 |
2018年 | 1776篇 |
2017年 | 2136篇 |
2016年 | 2021篇 |
2015年 | 2000篇 |
2014年 | 2945篇 |
2013年 | 3538篇 |
2012年 | 3824篇 |
2011年 | 4709篇 |
2010年 | 3400篇 |
2009年 | 3706篇 |
2008年 | 3522篇 |
2007年 | 3980篇 |
2006年 | 3616篇 |
2005年 | 2925篇 |
2004年 | 2598篇 |
2003年 | 2282篇 |
2002年 | 1858篇 |
2001年 | 1458篇 |
2000年 | 1254篇 |
1999年 | 1096篇 |
1998年 | 1001篇 |
1997年 | 852篇 |
1996年 | 787篇 |
1995年 | 663篇 |
1994年 | 533篇 |
1993年 | 428篇 |
1992年 | 360篇 |
1991年 | 330篇 |
1990年 | 262篇 |
1989年 | 226篇 |
1988年 | 163篇 |
1987年 | 134篇 |
1986年 | 117篇 |
1985年 | 98篇 |
1984年 | 91篇 |
1983年 | 74篇 |
1982年 | 100篇 |
1981年 | 37篇 |
1980年 | 17篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1976年 | 8篇 |
1959年 | 17篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(87):36926-36952
The ohmic resistance in solid oxide fuel cells (SOFCs) mainly comes from the electrolyte, which can be reduced by developing novel electrolyte materials with higher ionic conductivity and/or fabricating thin-film electrolytes. Among various kinds of thin-film fabrication technology, the physical vapor deposition (PVD) method can reduce the electrolyte thickness to a few micrometers and mitigate the issues associated with high-temperature sintering, which is necessary for wet ceramic methods. This review summarizes recent development progress in thin-film electrolytes fabricated by the PVD method, especially pulsed laser deposition (PLD) and magnetron sputtering. At first, the importance of the substrate surface morphology for the quality of the film is emphasized. After that, the fabrication of thin-film doped-zirconia and doped-ceria electrolytes is presented, then we provide a brief summary of the works on other types of electrolytes prepared by PVD. Finally, we have come to the summary and made perspectives. 相似文献
2.
《International Journal of Hydrogen Energy》2022,47(66):28645-28654
The introduction of catalyst on anode of solid oxide fuel cell (SOFC) has been an effective way to alleviate the carbon deposition when utilizing biogas as the fuel. A series of La0.6Sr0.4Co1-xNixO3-δ (x = 0, 0.2, 0.4, 0.6, 0.8) oxides are synthesized by sol-gel method and used as catalysts precursors for biogas dry reforming. The phase structure of La0.6Sr0.4Co1-xNixO3-δ oxides before and after reduction are characterized by X-ray diffraction (XRD). The texture properties, carbon deposition, CH4 and CO2 conversion rate of La0.6Sr0.4Co1-xNixO3-δ catalysts are evaluated and compared. The peak power density of 739 mW cm?2 is obtained by a commercial SOFC with La0.6Sr0.4Co0.4Ni0.6O3-δ catalyst at 850 °C when using a mixture of CH4: CO2 = 2:1 as fuel. This shows a great improvement from the cell without catalyst for internal dry reforming, which is attributed to the formation of NiCo alloy active species after reduction in H2 atmosphere. The results indicate the benefits of inhibiting the carbon deposition on Ni-based anode through introducing the La0.6Sr0.4Co0.4Ni0.6O3-δ catalyst precursor. Additionally, the dry reforming technology will also help to convert part of the exhaust heat into chemical energy and improve the efficiency of SOFC system with biogas fuel. 相似文献
3.
Christopher J. Marvel Qirong Yang Scott D. Walck Kelvin Y. Xie Kristopher D. Behler Jerry C. LaSalvia Masashi Watanabe Richard A. Haber Martin P. Harmer 《Journal of the American Ceramic Society》2022,105(5):2990-3007
Compositional analysis of boron carbide on nanometer length scales to examine or interpret atomic mechanisms, for example, solid-state amorphization or grain-boundary segregation, is challenging. This work reviews advancements in high-resolution microanalysis to characterize multiple generations of boron carbide. First, ζ-factor microanalysis will be introduced as a powerful (scanning) transmission electron microscopy ((S)TEM) analytical framework to accurately characterize boron carbide. Three case studies involving the application of ζ-factor microanalysis will then be presented: (1) accurate stoichiometry determination of B-doped boron carbide using ζ-factor microanalysis and electron energy loss spectroscopy, (2) normalized quantification of silicon grain-boundary segregation in Si-doped boron carbide, and (3) calibration of a scanning electron microscope X-ray energy-dispersive spectroscopy (XEDS) system to measure compositional homogeneity differences of B/Si-doped arc-melted boron carbides in the as-melted and annealed conditions. Overall, the improvement and application of advanced analytical tools have helped better understand processing–microstructure–property relationships and successfully manufacture high-performance ceramics. 相似文献
4.
5.
《Advanced Powder Technology》2022,33(12):103879
Heat transfer within ceramic feedstock powders is still unclear, which impedes optimization of the thermal and mechanical properties of the thermal sprayed coatings. The microspheres (yttria-stabilized zirconia YSZ and lanthanum zirconate LZO) were prepared via the electro-spraying assisted phase inversion method (ESP). The thermal properties of the two ESP microspheres and a commercial hollow spherical powder (HOSP) were investigated by using theoretical, experimental, and simulation methods. Thermal conductivity of the single microsphere was estimated via a novel nest model that was derived from the Maxwell-Eucken 1 and the EMT model. Thermal conductivity of a single YSZ/LZO-ESP microsphere prepared at 1100–1200 °C was within 0.36–0.75 W/m K, which was ~ 20 % lower than that of a single YSZ-HOSP microsphere with a similar porosity. Heat flux simulation showed that high tortuosity around the multi-scaled voids of the ESP microsphere led to a more efficient decrease in thermal conductivity compared with total porosity. 相似文献
6.
《International Journal of Hydrogen Energy》2022,47(64):27481-27492
Photocatalytic water splitting has become a promising technology to solve environmental pollution and energy shortage. Exploring stable and efficient photocatalysts are highly desired. Herein, we propose novel low-dimensional InSbS3 semiconductors with good stability based on density functional theory. Such InSbS3 structures could be obtained from their bulk crystal by suitable exfoliation methods. Our calculations indicate that two-dimensional (2D) and one-dimensional (1D) InSbS3 nanostructures have moderate band gaps (2.54 and 1.97 eV, respectively) and suitable band edge alignments, which represents sufficient redox capacity for photocatalytic water splitting. 2D InSbS3 monolayer possesses oxygen evolution reaction (OER) activity and 1D InSbS3 single-nanochain possesses hydrogen evolution reaction (HER) activity under acidic conditions. Interestingly, two edge electron states can be introduced when the dimension of InSbS3 is reduced from 2D to 1D and the new electron states can exist in arbitrary-width nanoribbons, which can effectively promote the process of HER. Moreover, InSbS3 monolayer and single-nanochain also exhibit large solar-to-hydrogen efficiency, high carrier mobility, and excellent optical absorption properties, which can facilitate the process of photocatalytic reactions. Our findings can stimulate the synthesis and applications of low-dimensional InSbS3 semiconductors for overall water splitting. 相似文献
7.
《International Journal of Hydrogen Energy》2022,47(47):20617-20631
Morphology of carbon nanofibers significantly effects Pt nanoparticles dispersion and specific interaction with the support, which is an important aspect in the fuel cell performance of the electrocatalysts. This study emphasizes, the defects creation and structural evolution comprised due to N–F co-doping on graphitic carbon nanofibers (GNFs) of different morphologies, viz. GNF-linearly aligned platelets (L), antlers (A), herringbone (H), and their specific interaction with Pt nanoparticle in enhancing the oxygen reduction reaction (ORR). GNFs–NF–Pt catalysts exhibit better ORR electrocatalytic activity, superior durability that is solely ascribed to the morphological evolution and the doped N–F heteroatoms, prompting the charge density variations in the resultant carbon fiber matrices. Amongst, H–NF–Pt catalyst performed outstanding ORR activity with exceptional electrochemical stability, which shows only 20 mV loss in the half-wave potential whilst 100 mV loss for Pt/C catalyst on 20,000 potential cycling. The PEMFC comprising H–NF–Pt as cathode catalyst with minimum loading of 0.10 mg cm?2, delivers power density of 0.942 W cm?2 at current density of 2.50 A cm?2 without backpressures in H2–O2 feeds. The H–NF–Pt catalyst owing to its hierarchical architectures, performs well in PEMFC at the minimized catalyst loading with outstanding stability that can significantly decrease total price for the fuel cell. 相似文献
8.
Xuejie Li Yaqing Wen Jian Zhang Dongyun Ma Jie Zhang Yanxia An Xiaoyan Song Xiujuan Ren Weifeng Zhang 《International Journal of Food Science & Technology》2022,57(3):1544-1553
The effects of non-thermal plasma (NTP) on the physicochemical properties of wheat flour and the quality of fresh wet noodles ( FWN) were investigated. The results showed that NTP effectively decreased the total plate count (TPC), yeast and mould count (YMC) and Bacillus spp. in wheat flour. Wet gluten contents and the stability time reached the maximum when treated for 20 s. The viscosity of starch increased significantly after treatment due to the increased of damaged starch. The contents of secondary structure were altered to some extent, which was because that the ordered network structure of gluten protein broken. Furthermore, compared with the control, texture properties of FWN were enhanced significantly at 20 s, and the darkening rate of FWN was greatly inhibited due to the low polyphenol oxidase (PPO) activity. Consequently, the most suitable treatment was 500 W for 20 s, providing a basis for the application of NTP in flour products. 相似文献
9.
《Geotextiles and Geomembranes》2022,50(5):910-921
This paper presents a field-scale experimental track over a poor subgrade with an unreinforced section and a geocell-reinforced section subjected to in-situ performance tests. Plate load tests and Benkelman beam tests were carried out distributed in several unreinforced and reinforced layers. The objective was to: (1) examine the variability of the elastic modulus of unbound granular material (UGM) due the influence of its thickness and the presence of poor subgrade in its base, (2) evaluate the modulus improvement factor (MIF) generated by the geocell reinforcement in the UGM and (3) verify the most appropriate condition to apply the MIF to transport infrastructure design. The results showed that there is a significant influence of the thickness of the UGM layer on its elastic modulus when the layer is supported directly over a soft subgrade. The MIF values obtained in field suggest that its determination is mostly related to the UGM maximum elastic modulus rather than its decreased values (by virtue of poor subgrade or reduced thicknesses), and that the analytical formulation presented for MIF calculation has good predictive capability to be applied to pavement design. 相似文献
10.
《Ceramics International》2021,47(22):31590-31596
In this study, the high ferroelectric hysteresis loss of (Pb0·93La0.07)(Zr0·82Ti0.18)O3 (PLZT 7/82/18) antiferroelectric (AFE) ceramics was reduced by employing a combinatorial approach of Mn acceptor doping followed by thick film fabrication via an aerosol deposition (AD) process. The grains of the as-deposited PLZT 7/82/18 AFE AD thick films were grown by thermal annealing at 550 °C to enhance their electrical properties. Investigation of the electrical properties revealed that Mn-doping results in improved dielectric and ferroelectric properties, increased dielectric breakdown strength (DBS), and energy-storage properties. The Mn-doped PLZT AFE AD films possess a frequency-independent high dielectric constant (εr ≈ 660) with low dielectric loss (tan δ ≈ 0.0146), making them suitable candidates for storage capacitor applications. The bipolar and unipolar polarization vs. electric field (P-E) hysteresis loops of PLZT 7/82/18 AFE AD thick films were found to be slimmer than those of their bulk form (double hysteresis) with significantly reduced ferroelectric hysteresis loss, which is attributed to the AD-induced mixed grain structure. The Mn-doped PLZT 7/82/18 AFE AD thick films exhibited a low remnant polarization (Pr ≈ 9.22 μC/cm2) at a high applied electric field (~2750 kV/cm). The energy-storage density and energy efficiency of the Mn-doped PLZT AFE AD thick films were calculated from unipolar P-E hysteresis loops and found to be ~38.33 J/cm3 and ~74%, respectively. 相似文献