全文获取类型
收费全文 | 18093篇 |
免费 | 2109篇 |
国内免费 | 1078篇 |
专业分类
电工技术 | 1091篇 |
综合类 | 1208篇 |
化学工业 | 2780篇 |
金属工艺 | 378篇 |
机械仪表 | 1259篇 |
建筑科学 | 1114篇 |
矿业工程 | 221篇 |
能源动力 | 505篇 |
轻工业 | 1054篇 |
水利工程 | 79篇 |
石油天然气 | 884篇 |
武器工业 | 127篇 |
无线电 | 5868篇 |
一般工业技术 | 2824篇 |
冶金工业 | 304篇 |
原子能技术 | 254篇 |
自动化技术 | 1330篇 |
出版年
2024年 | 37篇 |
2023年 | 303篇 |
2022年 | 405篇 |
2021年 | 633篇 |
2020年 | 672篇 |
2019年 | 659篇 |
2018年 | 550篇 |
2017年 | 743篇 |
2016年 | 762篇 |
2015年 | 792篇 |
2014年 | 1223篇 |
2013年 | 1096篇 |
2012年 | 1245篇 |
2011年 | 1338篇 |
2010年 | 1082篇 |
2009年 | 1104篇 |
2008年 | 1028篇 |
2007年 | 1125篇 |
2006年 | 1045篇 |
2005年 | 919篇 |
2004年 | 766篇 |
2003年 | 704篇 |
2002年 | 482篇 |
2001年 | 440篇 |
2000年 | 397篇 |
1999年 | 294篇 |
1998年 | 242篇 |
1997年 | 195篇 |
1996年 | 170篇 |
1995年 | 129篇 |
1994年 | 152篇 |
1993年 | 130篇 |
1992年 | 75篇 |
1991年 | 62篇 |
1990年 | 59篇 |
1989年 | 37篇 |
1988年 | 31篇 |
1987年 | 14篇 |
1986年 | 23篇 |
1985年 | 24篇 |
1984年 | 25篇 |
1983年 | 17篇 |
1982年 | 19篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1959年 | 3篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 298 毫秒
91.
92.
Using black coatings and materials with high light absorbance that are capable of absorbing photons at visible and longer wavelengths is a very effective way to reduce unwanted stray light, also known as optical noise, within optical equipment. These lights can be greatly reduced to a reasonable level by functional and performable black coatings that are modified to absorb incident light as much as possible by their specific pigments. In the present work, several carbonaceous pigments were synthesized for the first time from wasteful materials and their optical properties in the visible and near‐infrared ranges studied. First, MCM‐48 and SBA‐15 were synthesized at different conditions and were then used as templates for carbonaceous products. SSS‐1 (the carbonic pigment synthesized by the mixture of sucrose and sodium silicate), SSS‐2 (the carbonic pigment synthesized by the mixture of sawdust and sodium silicate), and mesoporous carbon pigments (CMK‐3 and CMK‐1 with different levels of saturations) were synthesized. Finally, their structure, morphology, and optical properties were investigated by X‐ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE‐SEM), and Diffuse Reflectance Spectroscopy (DRS). The results indicated that the SSS‐1 pigment had a lower reflectance (below 1%) than carbon black (about 2.5%) in the visible region despite it being more cost‐effective than carbon black. The mesoporous pigments showed very high light absorbance in the visible region (about 2.5%). Compared with other black pigments, the CMK‐1 was the blackest synthesized material with a very low reflectance (about 0.05% in visible region), making it an ideal candidate as a super black pigment for reducing unwanted stray light within optical equipment. 相似文献
93.
Xue Li Xianjun Lyu Xiaohan Zhao Yan Zhang Stephen Nyabire Akanyange John C. Crittenden Huaqing Zhao Tianlin Jiang 《International Journal of Hydrogen Energy》2021,46(35):18376-18390
In this study, GO and Fe2P were used as co-catalysts to improve the separation efficiency of photogenerated electron-hole pairs in an In2S3 photocatalyst. The metallic character of Fe2P provided a cheap substitute for traditional noble metal co-catalyst for H2 production in aqueous media. The GO/Fe2P/In2S3 composite demonstrated significantly enhanced photocatalytic activity compared to pure In2S3, delivering a H2 production rate of 483.35 μmol h?1 g?1 and a quantum yield was 22.68% under visible light irradiation. The design of the photocatalyst was optimized using “Design Expert” software. The analysis showed that a GO loading of 1.18 wt%, a Fe loading of 5.36 wt%, and a calcination temperature of 180 °C were optimal. 相似文献
94.
95.
Hameed Al‐Attar Aula A Alwattar Athir Haddad Bassil A Abdullah Peter Quayle Stephen G Yeates 《Polymer International》2021,70(1):51-58
In this work we demonstrate, for the first time, the use of polylactic acid (PLA) as a biodegradable host matrix for the construction of the active emissive layer of organic light‐emitting diode (OLED) devices for potential use in bioelectronics. In this preliminary study, we report a robust synthesis of two fluorescent PLA derivatives, pyrene‐PLA ( AH10 ) and perylene‐PLA ( AH11 ). These materials were prepared by the ring opening polymerisation of l ‐lactide with hydroxyalkyl‐pyrene and hydroxyalkyl‐perylene derivatives using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene as catalyst. OLEDs were fabricated from these materials using a simple device architecture involving a solution‐processed single‐emitting layer in the configuration ITO/PEDOT:PSS/PVK:OXD‐7 (35%): AH10 or AH11 (20%)/TPBi/LiF/Al (ITO, indium tin oxide; PEDOT:PSS, poly(3,4‐ethylenedioxythiophene) doped with poly(styrenesulfonic acid); PVK, poly(vinylcarbazole); OXD‐7, (1,3‐phenylene)‐bis‐[5‐(4‐tert‐butylphenyl)‐1,3,4‐oxadiazole]; TPBi, 2,2′,2″‐(1,3,5‐benzenetriyl)tris(1‐phenyl‐1H‐benzimidazole)). The turn‐on voltage for the perylene OLED at 10 cd m–2 was around 6 V with a maximum brightness of 1200 cd m–2 at 13 V. The corresponding external quantum efficiency and device current efficiency were 1.5% and 2.8 cd A–1 respectively. In summary, this study provides proof of principle that OLEDs can be constructed from PLA, a readily available and renewable bio‐source. © 2020 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry. 相似文献
96.
Accurate measurements of radiation dose are essential prerequisites for the safe and effective use of ionizing radiation in diagnostic and therapeutic medical applications. Recently, dosimeters based on organic polymers have been developed for this purpose. In this work, Poly(3-hexylthiophene-2,5-diyl) (P3HT) based organic diodes were evaluated as potential radiation dosimeters by quantifying the radiation-induced photocurrent under various measurement conditions. Control devices were fabricated in which the P3HT was replaced by polystyrene (PS) for the purpose of quantifying the non-photocurrent contribution to the measured signal. Net photocurrent was determined by subtracting the signal from the PS devices from the signal in the P3HT devices under identical measurement conditions. The responses of these devices were tested in various beam qualities: 100 kVp, 180 kVp, 300 kVp and 6 MV, 18 MV photons. The influences of electric field, film thickness and dose rate on dosimeter sensitivity were investigated. The diodes produced a linear increase in current with increasing dose rate. They demonstrated an increase in sensitivity with increased instantaneous dose rate and an increase in sensitivity at the lowest average dose rates studied here. The sensitivities for different energies were 22.9 nC/Gy, 21.8 nC/Gy and 21.4 nC/Gy for 100 kVp, 180 kVp and 300 kVp, respectively; and 14.5 nC/Gy, 14.7 nC/Gy for 6 MV and 18 MV, respectively for device with P3HT thickness 29 μm. 相似文献
97.
《International Journal of Hydrogen Energy》2022,47(17):9925-9933
In recent years, tremendous efforts have been devoted to develop new photocatalyst with wide spectrum response for H2 generation from water or aqueous solution. In this paper, MnxCd1-xS composites were in-situ fabricated via the high-temperature sulfurization to enhance the solar-light photocatalytic capacity of H2 evolution. Benefiting from the S defects and junction interface between MnS and CdS, MnxCd1-xS composites exhibited the better H2 evolution rate than pure MnS. The H2 evolution rate of optimal Mn0.5Cd0.5S with a Mn(II) content of 22.52% and a Mn/Cd mole ratio of 0.95:1 was 9.27 mmol g?1 h?1, which was 35.65 and 2.38 times higher than pure MnS (0.26 mmol g?1 h?1) and CdS (3.89 mmol g?1 h?1), respectively. In addition, H2 evolution capacity of Mn0.5Cd0.5S decreased from 44.83 to 41.66 mmol g?1 after three cycles. Mn0.5Cd0.5S prepared via the high-temperature sulfurization was thus a potential material for solar-light induced H2 generation. 相似文献
98.
Displays that can be reversibly stretched in their geometrical layout are highly important in various applications. Stretchable displays are commonly demonstrated using two-dimensional (2D) geometries with stretchable rubber substrates and elastic interconnects. However, mechanical stretch induces deterioration of the resolution per unit area and blurs the displayed image, consequently lowering the display quality. In this study, we demonstrate a morphable 3D structure inspired by origami/kirigami to produce stretchable displays that can preserve the original image quality by maintaining the display pixel density under stretching. The morphable 3D display consists of a 7 × 7 micro-light-emitting diode (LED) pixel array integrated on a transparent epoxy structural frame, which can be stretched up to 100% without affecting the performance of the display. The functional 3D system can create important unconventional opportunities for optoelectronic devices. 相似文献
99.
Sinuo Zhang Imam Akbar Sutejo Jeehwan Kim Yeong-Jin Choi Honghyun Park Hui-suk Yun 《Journal of the American Ceramic Society》2022,105(6):3827-3837
Illite is a group of clay minerals that are expected to be widely used in catalyst fabrication, radioactive element adsorption, and so forth, due to its excellent adsorption properties. However, the shape control limitation of the illite product should be overcome to maximize its utilization and properties. We herein propose additive manufacturing (AM) as one of the best solutions to solve this structural drawback. Digital light processing (DLP) technology with the film-type of the material supplying system was adapted instead of the general vat-type DLP system to increase illite printability. The photo-curability and printability of illite-contained photocurable suspension were optimized. The color effect due to different ferric oxide content in yellow- and white-illite which influence the photopolymerization process also adjusted thoroughly. White illite showed better photo-curability and could be increased solid loading than yellow illite. The defect-free illite products with three-dimensional complex structures, which cannot be produced by typical ceramic processes, were obtained by DLP technology for both yellow- and white-illite after sintering at 1100°C. The overcoming of shape control limitation of illites by ceramic AM proved in this study has excellent potential for expanding illite utilities in various applications. 相似文献
100.
Wei Wei Haoyang Gong Lin Sheng Houfan Wu Shuguang Zhu Li Feng Xuhao Li Weihong You 《Ceramics International》2021,47(17):24062-24072
Bismuth oxyhalides (BiOX (X = Cl, Br, I) are considered to be an important p-type semiconductors in the photocatalysis applications. In particular, tetragonal BiOBr is considered as a stable photocatalyst due to its resilient absorption in the visible region with an band gap energy of 2.8 eV. In the meantime, lanthanide ions (with 3+ oxidation state) implies as conversion catalyst gained huge impact and remain a serious topic in materials chemistry. Here we synthesized upconversion photocatalyst mainly consists of BiOBr with the Er 3+ and Tb 3+ ions along with low band gap g-C3N5 for the improved photocatalytic performances. The synthesized Er3+/Tb3+@BiOBr-g-C3N5 heterojunction was systematically characterized by XRD, and FT-IR for the confirmation of the composite and their morphology were analysed with FESEM and HR-TEM analysis which revealed that the sheets of g-C3N5 were decorated by Er3+/Tb3+ loaded BiOBr microspheres. The XPS analysis confirmed the suitable oxidation state of all the individual elements existing in the composite. As the UV-DRS analysis showed that the band gap of the Er3+/Tb3+ BiOBr-gC3N5 heterojunction was narrowed to 2.64 eV. To evaluate the photocatalytic efficiency of the synthesized g-C3N5, Er3+/Tb3+@BiOBr and Er3+/Tb3+@BiOBr-gC3N5 heterojunction under the simulated visible light irradiation source towards the aqueous sulfamethoxazole degradation. The Er3+/Tb3+@BiOBr-gC3N5 heterojunction shows maximum degradation efficiency of 94.2% after 60 min of visible light irradiation whereas the pure g-C3N5 provided about 43.8% and Er3+/Tb3+@BiOBr implies 55.2% degradation efficiency. The plausible degradation mechanism of pollutant removal was proposed. 相似文献