全文获取类型
收费全文 | 2295篇 |
免费 | 131篇 |
国内免费 | 24篇 |
专业分类
电工技术 | 5篇 |
综合类 | 259篇 |
化学工业 | 981篇 |
金属工艺 | 205篇 |
机械仪表 | 23篇 |
建筑科学 | 125篇 |
矿业工程 | 16篇 |
能源动力 | 201篇 |
轻工业 | 17篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 81篇 |
一般工业技术 | 480篇 |
冶金工业 | 15篇 |
原子能技术 | 8篇 |
自动化技术 | 26篇 |
出版年
2024年 | 2篇 |
2023年 | 303篇 |
2022年 | 123篇 |
2021年 | 91篇 |
2020年 | 156篇 |
2019年 | 144篇 |
2018年 | 38篇 |
2017年 | 105篇 |
2016年 | 92篇 |
2015年 | 105篇 |
2014年 | 120篇 |
2013年 | 88篇 |
2012年 | 158篇 |
2011年 | 137篇 |
2010年 | 111篇 |
2009年 | 87篇 |
2008年 | 59篇 |
2007年 | 180篇 |
2006年 | 124篇 |
2005年 | 63篇 |
2004年 | 30篇 |
2003年 | 31篇 |
2002年 | 32篇 |
2001年 | 19篇 |
2000年 | 16篇 |
1999年 | 22篇 |
1998年 | 9篇 |
1997年 | 5篇 |
排序方式: 共有2450条查询结果,搜索用时 15 毫秒
2.
Additive manufacturing,quasi-static and dynamic compressive behaviours of ceramic lattice structures
《Journal of the European Ceramic Society》2022,42(15):7102-7112
Ceramic lattice structures (CLSs) are used for construction in common and extreme environments because of the extraordinary properties of ceramics. In this study, we designed and additively manufactured CLSs with distinct structural parameters to explore their quasi-static and dynamic compressive behaviours in detail. It was demonstrated that both the relative density (?ρ) and inclination angle (ω) had a significant impact on the quasi-static and dynamic mechanical properties of the CLSs. Furthermore, the mathematical relationships between the quasi-static compressive properties, including quasi-static compressive strength (QS), quasi-static Young’s modulus (QY), and quasi-static energy absorption (QE), versus ?ρ and ω obeyed the Gibson–Ashby and Deshpande and Fleck models, respectively. It was revealed by experiment and simulation that as the stiffness increased, the quasi-static failure mode of the CLSs changed from a parallel-vertical-inclined mixed mode to a parallel-vertical mode. In addition, the relationship between the dynamic mechanical properties of the CLSs versus ?ρ and ω also followed the Gibson–Ashby and Deshpande and Fleck models. The exceptional dynamic increase factor indicated that CLSs are highly suitable for extreme environments. These findings will aid in the research and development of customised additively manufactured CLSs. 相似文献
3.
Kai Liu Chenyang Zhou Jiaming Hu Song Zhang Qingqing Zhang Ce Sun Yusheng Shi Huajun Sun Changxia Yin Yuzhen Zhang Yu Fu 《Journal of the European Ceramic Society》2021,41(12):5909-5917
A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices. 相似文献
4.
Poly(4-styrenesulfonic acid) (PSSA) doped polypyrrole (PPy)/tungsten oxide (WO3)/reduced graphene oxide (rGO) hybrid nanocomposite have been successfully synthesized using appropriate amounts of PSSA, pyrrole monomer, WO3, and rGO dispersed in aqueous solution through in situ chemical oxidation polymerization. Here, a simple spin coating method was used to fabricate a nitric oxide (NO) gas sensor composed of the aforementioned nanocomposite on a surface acoustic wave (SAW) resonator. This sensor can detect NO gas at concentrations of 1–110 parts per billion (ppb) at room temperature in dry air, with a sensitivity of 12 Hz/ppb and response and recovery times of <2 min. Moreover, its limit of detection (LOD) is 0.31 ppb for a signal to noise ratio of 3. It demonstrates repeatability, fast response, and recovery at room temperature. Moreover, its sensory performance remains highly stable over 30 days with only a 6.3% decrease in sensitivity. In addition, the sensor is highly selective for NO, even when nitrogen dioxide, ammonia, and carbon dioxide are applied as interfering gases. The inclusion of rGO (with large specific surface area) and the synergic effect of n-type WO3 nanoparticles in the p-type PPy matrix (leading to p-n heterojunction region formation) possibly underlie the efficient sensing performance of our sensor. 相似文献
5.
《Journal of the European Ceramic Society》2019,39(16):5373-5379
The nanocrystals play a critical role in generating and affecting functionalities of glass materials. Therefore, scientists have made considerable efforts in clarifying microscopic mechanisms of nanocrystal formation in glass to obtain the desired type of nanocrystals. However, the phase transitions of nanocrystals during heating have not been well understood. Here we report on a discovery of the reversible melting-formation of nanocrystals in an oxyfluoride germanate glass during heating-cooling circles. Using a differential scanning calorimetry (DSC), we detected a striking endothermic event at 925 K during heating, after the glass underwent a DSC upscan to a temperature between 925–986 K and subsequent cooling. Based on Raman spectroscopy, X-ray diffraction and transmission electron microscopy, the endotherm is attributed to the melting of nano-crystal BaGeF6 (˜20 nm). An exothermal response was observed at 890 K during the DSC downscan, implying the re-formation of BaGeF6 nano-crystals. This suggests that the melting-formation of BaGeF6 nano-crystals is a typical first-order transition. 相似文献
6.
《Journal of the European Ceramic Society》2019,39(16):5292-5297
Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF), which exhibits a high mixed oxide ionic-electronic conduction, was used for the fabrication of an oxygen separation membrane. An asymmetric structure, which was a thin and dense BSCF membrane layer supported on a porous BSCF substrate, was fabricated by the electrophoretic deposition method (EPD). Porous BSCF supports were prepared by the uniaxial pressing method using a powder mixture with BSCF and starch as the pore-forming agent (0–50 wt.%). The sintering behaviors of the porous support and the thin layer were separately characterized by dilatometry to determine the co-fired temperature at which cracking did not occur. A crack-free and thin dense membrane layer, which had about a 15 μm thickness and >95% relative density, was obtained after optimizing the processes of EPD and sintering. The dense/porous interface was well-bonded and the oxygen permeation flux was 2.5 ml (STP) min−1 cm-2 at 850 °C. 相似文献
7.
《International Journal of Hydrogen Energy》2021,46(59):30355-30365
To design inexpensive carbon catalysts and enhance their oxygen reduction reaction (ORR) activity is critical for developing efficient energy-conversion systems. In this work, a novel Fe-N-C hybrid electrocatalyst with carbon nanolayers-encapsulated Fe3O4 nanoparticles is synthesized successfully by utilizing the molecular-level confinement of graphitic C3N4 structures via hemin biomaterial. Benefiting from the Fe-N structure prevalent on the carbon nanosheets and large mesopore-dominated specific surface area, the synthesized catalyst under optimized conditions shows excellent electrocatalytic performance for ORR with an EORR at 1.08 V versus reversible hydrogen electrode (RHE) and an E1/2 at 0.87 V vs. RHE, and outstanding long-term stability, which is superior to commercial Pt/C catalysts (EORR at 1.04 V versus RHE and E1/2 at 0.84 V versus RHE). Moreover, the low hydrogen peroxide yield (<11%) and average electron transfer number (~3.8) indicate a four-electron ORR pathway. Besides, the maximum power density of the home-made Zn-air battery using the obtained catalyst is 97.6 mW cm−2. This work provides a practical route for the synthesis of cheap and efficient ORR electrocatalysts in metal-air battery systems. 相似文献
8.
《Ceramics International》2022,48(16):23051-23060
To obtain both plasticity and toughness of the material at the same time, various manufacturing techniques of ceramic-metal composites and structures have been studied. In this work, a bio-inspired Al2O3 ceramic scaffold with Gyroid structure was designed and prepared by stereolithographic (SL) additive manufacturing, then the Al2O3/Al ceramic-metal hybrid structure was prepared by infiltrating molten Al into the Al2O3 ceramic structure. The performances of the Al2O3 ceramic scaffold and the Al2O3/Al ceramic-metal hybrid structure were compared and analyzed by a quasi-static compression experiment. The quasi-static compressive strength of the pristine Al2O3 scaffold was 14.36 MPa, while that of the Al2O3/Al ceramic-metal hybrid structure was up to 89.06 MPa. Moreover, the plasticity of the Al2O3/Al ceramic-metal hybrid structure was much higher than that of the Al2O3 scaffold. During compression, the Al2O3/Al ceramic-metal hybrid structure had excellent energy absorption, reaching up to 2569.16 KJ/m³, 15 times that of the Al2O3 scaffold. Therefore, this method can obtain materials with excellent ductility and toughness. 相似文献
9.
《Journal of the European Ceramic Society》2022,42(9):3857-3864
The Mn-modified 0.75BiFeO3-0.25BaTiO3 (75BFBTMn) piezoelectric ceramic possesses a high depolarization temperature of 500 °C and a large piezoelectric coefficient of 110 pC/N, showing the potential for high temperature piezoelectric sensors. However, 75BFBTMn ceramic usually suffers dielectric degradation and abrupt drop of piezoelectric coefficient in the range of 300 °C to 500 °C. Combined the high-energy synchrotron X-ray diffraction analysis with Backscatter-SEM results, it is demonstrated that the electrical thermal instability is owing to the existence of chemical inhomogeneity. The Air-annealing treatment is able to decrease the volume fraction of pseudo-cubic phase and the lattice distortion, removes the chemical inhomogeneity in the grain and free Bi2O3 at grain boundary, and then eliminates dielectric anomalies and piezoelectric degradation with temperature. These results indicate that air-annealing is a simple but effective method to eliminate the chemical inhomogeneity in 75BFBTMn ceramics, thereby improving the property thermal stability for high temperature piezoelectric sensor applications. 相似文献
10.
Junling Guo Huayu Pei Ying Dou Siyuan Zhao Guosheng Shao Jinping Liu 《Advanced functional materials》2021,31(18):2010499
Lithium-sulfur batteries (LSBs) are considered a promising next-generation energy storage device owing to their high theoretical energy density. However, their overall performance is limited by several critical issues such as lithium polysulfide (PS) shuttles, low sulfur utilization, and unstable Li metal anodes. Despite recent huge progress, the electrolyte/sulfur ratio (E/S) used is usually very high (≥20 µL mg−1), which greatly reduces the practical energy density of devices. To push forward LSBs from the lab to the industry, considerable attention is devoted to reducing E/S while ensuring the electrochemical performance. To date, however, few reviews have comprehensively elucidated the possible strategies to achieve that purpose. In this review, recent advances in low E/S cathodes and anodes based on the issues resulting from low E/S and the corresponding solutions are summarized. These will be beneficial for a systematic understanding of the rational design ideas and research trends of low E/S LSBs. In particular, three strategies are proposed for cathodes: preventing PS formation/aggregation to avoid inadequate dissolution, designing multifunctional macroporous networks to address incomplete infiltration, and utilizing an imprison strategy to relieve the adsorption dependence on specific surface area. Finally, the challenges and future prospects for low E/S LSBs are discussed. 相似文献