全文获取类型
收费全文 | 19269篇 |
免费 | 2358篇 |
国内免费 | 1275篇 |
专业分类
电工技术 | 796篇 |
综合类 | 1084篇 |
化学工业 | 4001篇 |
金属工艺 | 4293篇 |
机械仪表 | 871篇 |
建筑科学 | 419篇 |
矿业工程 | 411篇 |
能源动力 | 808篇 |
轻工业 | 1778篇 |
水利工程 | 53篇 |
石油天然气 | 293篇 |
武器工业 | 217篇 |
无线电 | 1541篇 |
一般工业技术 | 3060篇 |
冶金工业 | 1588篇 |
原子能技术 | 1410篇 |
自动化技术 | 279篇 |
出版年
2024年 | 40篇 |
2023年 | 392篇 |
2022年 | 671篇 |
2021年 | 829篇 |
2020年 | 792篇 |
2019年 | 759篇 |
2018年 | 759篇 |
2017年 | 830篇 |
2016年 | 751篇 |
2015年 | 689篇 |
2014年 | 1000篇 |
2013年 | 1281篇 |
2012年 | 1207篇 |
2011年 | 1409篇 |
2010年 | 1012篇 |
2009年 | 1085篇 |
2008年 | 959篇 |
2007年 | 1311篇 |
2006年 | 1214篇 |
2005年 | 977篇 |
2004年 | 911篇 |
2003年 | 691篇 |
2002年 | 557篇 |
2001年 | 499篇 |
2000年 | 392篇 |
1999年 | 347篇 |
1998年 | 268篇 |
1997年 | 238篇 |
1996年 | 222篇 |
1995年 | 149篇 |
1994年 | 134篇 |
1993年 | 112篇 |
1992年 | 96篇 |
1991年 | 78篇 |
1990年 | 41篇 |
1989年 | 46篇 |
1988年 | 28篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 31篇 |
1981年 | 20篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1959年 | 3篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
《International Journal of Hydrogen Energy》2022,47(36):16165-16178
This study deals with the manufacturing of catalyst-coated membranes (CCMs) for newcomers in the field of coating. Although there are many studies on electrode ink composition for improving the performance of proton-exchange membrane fuel cells (PEMFCs), there are few papers dealing with electrode coating itself. Usually, it is a know-how that often remains secret and constitutes the added value of scientific teams or the business of industrialists. In this paper, we identify and clarify the role of key parameters to improve coating quality and also to correlate coating quality with fuel cell performance via polarization curves and electrochemical active surface area measurements. We found that the coating configurations can affect the performance of lab-made CCMs in PEMFCs. After the repeatability of the performance obtained by our coating method has been proved, we show that: (i) edge effects, due to mask shadowing - cannot be neglected when the active surface area is low, (ii) a heterogeneous thickness electrode produces performance lower than a homogeneous thickness electrode, and (iii) the origin and storage of platinum on carbon powders are a very important source of variability in the obtained results. 相似文献
12.
Andreas S. Katsigiannis Danny L. Bayliss James L. Walsh 《Comprehensive Reviews in Food Science and Food Safety》2022,21(2):1086-1124
Food safety is the primary goal for food and drink manufacturers. Cleaning and disinfection practices applied to the processing environment are vital to maintain this safety; yet, current approaches can incur costly downtime and the potential for microorganisms to grow and establish, if not effectively removed. For that reason, manufacturers are seeking nonthermal, online, and continuous disinfection processes to control the microbial levels within the processing environment. One such emerging technique, with great potential, is cold atmospheric pressure plasma (CAP). This review presents the latest advances and challenges associated with CAP-based technologies for the decontamination of surfaces and equipment found within the food-processing environment. It provides a detailed overview of the technology and a comprehensive analysis of the many CAP-based antimicrobial studies on food-contact surfaces and materials. As CAP is considered an emerging technique, many of the recent studies are still in the preliminary stages, with results obtained under widely different conditions. This lack of cohesive information and an inability to directly compare CAP systems has greatly impeded technological development. The review further explores the challenge of scaling CAP technology to meet industry needs, considering aspects such as regulatory constraints, environmental credentials, and cost of use. Finally, a discussion is presented on the future outlook for CAP technology in this area, identifying key challenges that must be addressed to promote industry uptake. 相似文献
13.
《Ceramics International》2022,48(9):12800-12805
Perovskite solid solution materials, namely, 0.67BiFeO3-0.33BaTiO3, were synthesized by spark plasma sintering method. The effects of the spark plasma sintering temperature on phase purity, microstructure, and electric properties of the as-prepared materials were investigated. The materials could be referred as pseudocubic phases based on the X-ray diffraction patterns. The bulk density first increased and then decreased. The 880 °C-sintered-ceramics had the maximal density and a compact microstructure with grain size of 0.77 ± 0.34 μm. The dielectric constant as a function of temperature exhibited a broad peak. At the optimal spark-plasma-sintering temperature, enhanced ferroelectric properties were observed with a value of Pr ~ 21 μC/cm2. This investigation on the spark plasma sintering process confirms it as an efficient approach to prepare outstanding performance BiFeO3–BaTiO3 ceramics. 相似文献
14.
《Ceramics International》2022,48(16):23510-23517
In the present work, microstructural refinement and mechanical response of Al2O3–ZrO2 eutectics fabricated by a pulse discharge plasma assisted melting (PDPAM) method were investigated. The solidified microstructure evolves from polygonal eutectic colonies into irregular cellular colonies with increasing the superheating temperature of the melt from 1820 °C to 1900 °C. The average eutectic spacing inside the colonies decreases from 1.80 ± 0.10 μm to 0.25 ± 0.06 μm, and the coarse inter-colonial structure is refined, which is attributed to the increase in undercooling temperature. High-temperature microstructural stability of Al2O3–ZrO2 eutectics is improved significantly as contrasted with the as-sintered ceramics. Besides, the load dependence of Vickers hardness for Al2O3–ZrO2 eutectics is investigated. 相似文献
15.
《Ceramics International》2022,48(17):24540-24549
In this study, we investigated the physical and chemical properties of H2 plasma-treated tin oxide (SnOX) thin films, followed by their applications in ambipolar thin-film transistors (TFTs). Finely controlled H2 implantation was carried out using a reactive-ion-etching system at a radio frequency power of 30 W and under various exposure times. H2 plasma treatments induced changes in the chemical structures and surface morphologies of the SnOX thin films, including a partial phase transformation of Sn and SnO to SnO2. The defects originating from oxygen vacancies (OVacs) in the SnOX thin films were passivated by H via the formation of Sn–H bonds, which decreased the density of subgap states in the SnOX thin films. The H2 plasma-treated SnOX TFTs showed considerably improved ambipolarity and electrical performance. Complementary metal–oxide–semiconductor (CMOS) logic inverters comprising H2-plasma-treated ambipolar SnOX TFTs exhibited a maximum gain of 34.5 V/V at a supply voltage of 10 V. The results of this study present the meaningful investigation of H2 plasma-treated ambipolar SnOX TFTs that can be used to fabricate CMOS circuits for various applications. 相似文献
16.
《Ceramics International》2022,48(20):30376-30383
In this study, α/β-Si3N4 composite ceramics with high hardness and toughness were fabricated by adopting two different novel ternary additives, ZrN–AlN–Al2O3/Y2O3, and spark plasma sintering at 1550 °C under 40 MPa. The phase composition, microstructure, grain distribution, crack propagation process and mechanical properties of sintered bulk were investigated. Results demonstrated that the sintered α/β-Si3N4 composite ceramics with ZrN–AlN–Al2O3 contained the most α phase, which resulted in a maximum Vickers hardness of 18.41 ± 0.31 GPa. In the α/β-Si3N4 composite ceramics with ZrN–AlN–Y2O3 additives, Zr3AlN MAX-phase and ZrO phase were found and their formation mechanisms were explained. The fracture appearance presented coarser elongated β-Si3N4 grains and denser microstructure when 20 wt% TiC particles were mixed into Si3N4 matrix, meanwhile, exhibited maximum mean grain diameter of 0.98 ± 0.24 μm. As a result, the compact α/β-Si3N4 composite ceramics containing ZrN–AlN–Y2O3 additives and TiC particles displayed the optimal bending strength and fracture toughness of 822.63 ± 28.75 MPa and 8.53 ± 0.21 MPa?m1/2, respectively. Moreover, the synergistic toughening of rod-like β-Si3N4 grains and TiC reinforced particles revealed the beneficial effect on the enhanced fracture toughness of Si3N4 ceramic matrix. 相似文献
17.
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
18.
《International Journal of Hydrogen Energy》2022,47(4):2234-2244
In this work, the solution plasma-assisted method was used to prepare NiMnAl-LDO (layered double oxides) catalysts with different treatment times, which were used for the CO2 methanation reaction. Solution plasma treatment can enhance the dispersibility of the catalyst, create oxygen defects and improve the chemical adsorption capacity of the catalyst. The results show that the low-temperature activity of the catalyst has been improved after the solution plasma treatment. We demonstrate that the NiMnAl-LDO-P(20) catalyst with high dispersion has the highest catalytic activity in CO2 methanation (81.3% CO2 conversion and 96.7% CH4 selectivity at 200 °C). Even though working for 70 h, the catalyst is still highly stable. This work provides a great promise for improving the low-temperature activity of Ni-based catalysts. 相似文献
19.
《International Journal of Hydrogen Energy》2022,47(8):5240-5249
Coke deposition has been considered to be one of the most important reasons hindering the stability of the catalyst during CH4/CO2 reforming. In this study, after the addition of P123 (PEG-PPG-PEG triblock copolymer), Ni2+ can be well-dispersed on the mesoporous molecular sieve MCM-41. And then, the catalysts were prepared by using N2 radio frequency (RF) discharge plasma for different treatment times to reduce the size of Ni particles, improve the anti-coking performance, and thereby improve the stability of the catalyst. The results showed that the catalyst NM-P123-PN2h exhibits superior catalytic properties in the CH4/CO2 reforming. The initial conversions of CH4 and CO2 were 90.80% and 89.60% at 750 °C, respectively. The catalyst NM-P123-PN2h showed highly coke resistance with less carbon deposition (1.12%) at 750 °C after 10 h of continuous reaction, while the carbon deposition of the catalyst NM-C was 37.32%. Compared with the traditional calcination method, the catalyst prepared by plasma treatment has a smaller particle size and better dispersibility of nickel. In particular, the nickel particle size of the catalyst NM-C was 8.37 nm, however, that of the catalyst NM-P123-PN2h was only 1.70 nm, and the nickel particle size was reduced by 5 times. Therefore, it can be concluded that the catalyst prepared under the combined action of P123 and RF plasma-treated can effectively improve the coke resistance of the catalyst and the stability of the CH4/CO2 reforming. 相似文献
20.
Application-specific optical glass properties are achieved by utilizing complex material compositions. This can be problematic in reactive plasma-assisted deterministic surface processing since a non-volatile surface layer may form depending on the glass composition, which affects the etch rate and thereby the local etching depth. In this investigation, a model algorithm is proposed to tackle some restrictions in applying fluorine-based plasma jet as etching tool utilized for freeform surface machining of optics made of complex glass composition, like borosilicate crown glass (e.g., N-BK7®). In this regard, firstly an analytical model is proposed for estimating the depth-dependent etch rate function. Subsequently, a recursive simulation algorithm is introduced for convolving the derived depth-dependent etch rate function with the given dwell time matrix to simulate a deterministic freeform generation process. By the proposed simulation algorithm, the impeding influence of the residual layer on the reduction of etching depth is computed prior to a real experiment in order to scale the local dwell time to ensure the targeted local removal. Finally, the simulated freeform shape is compared with the corresponding result of an etching experiment to validate the feasibility of the proposed approach. 相似文献