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1.
To evaluate the fill of internal resorption cavities obturated with thermoplasticized gutta‐percha and GuttaFlow2 using CT scan. Twenty human maxillary anterior teeth were selected and root canals were prepared using ProTaper system to size F3. Irrigation was performed with 5 ml of 2.5% sodium hypochlorite (NaOCl) and 5 ml of 17% ethylenediaminetetraacetic acid (EDTA). Each root was then sectioned horizontally into two halves and semicircular cavities were prepared around the periphery of the root canal opening of each root half, using a round bur. Both the root halves were then fixed using cyanoacrylate glue. All the specimens were subjected to preoperative CT scan analysis to determine the volume of internal cavities. The samples were then randomly divided into two groups. In Group 1, the specimens were obturated with thermoplasticized gutta‐percha (E&Q system) and specimens in Group 2 were obturated using GuttaFlow2. All specimens were then subjected to postoperative CT scan analysis. The volume of voids in internal resorptive cavities were calculated, which was then used to estimate the amount of gutta‐percha filled. There was no significant difference in volume of internal resorptive cavities between thermoplasticized gutta‐percha and GuttaFlow2 groups before obturation (p = 0.466). However, after obturation there was a significant difference between both the groups, in which GuttaFlow2 demonstrated better fill (p = .014). Thermoplasticized gutta‐percha filled 81% of internal resorptive cavity while GuttaFlow2 filled 91%, respectively. GuttaFlow2 showed better fill than thermoplasticized gutta‐percha in the filling of internal resorptive cavities.  相似文献   
2.
Ethylene diamine bisborane (EDB) was synthesized in a single step as the hydrogen storage material. The synthesized compound was firstly used in the literature for the production of hydrogen gas by catalytic hydrolysis reaction. Cu, Co and Ni nanoparticles with average sizes of 75–150 nm formed in p(acrylicacid-co-vinylimidazole) hydrogel network structures were used as catalysts for the hydrolysis reaction. The effect of the parameters such as catalyst type, EDB concentration, catalyst concentration, temperature and solvent environment on the catalytic hydrolysis reaction of EDB was investigated. In the activity tests for the catalyst, it was determined that the catalyst had a loss of only 15% in activity even at the end of 5 cycles. The activation energies of hydrolysis reaction were calculated as 39.42 kJmol–1, 44.77 kJmol–1 and 47.48 kJmol–1 for Cu, Co and Ni hydrogel composite catalyst, respectively.  相似文献   
3.
介绍了几种制备低介电常数聚酰亚胺(PI)材料的方法及其研究进展,包括引入氟原子降低极化率、引入硅氧烷增大自由体积、引入孔洞降低密度以及多种方法相结合共同降低介电常数等,指出了低介电常数PI制备方法的未来发展方向。  相似文献   
4.
含环氧基有机硅氧烷是一类兼具环氧与硅氧烷两种结构特性的化合物,因其优异的机械性能、环境稳定性和环氧基团的反应性能得到研究学者的广泛关注。以环氧基在化学结构中的不同位置为线路,系统地介绍了近年来国内外有关不同类型的含环氧基有机硅氧烷的多种制备工艺,并对其物化性能及应用情况进行了详细的介绍。研究开发高性能的含环氧基团有机硅氧烷,对于改性环氧树脂和满足高功率LED对封装材料日益提升的性能要求具有重要意义。  相似文献   
5.
为探讨姜黄素对荧光假单胞菌的光动力灭活(photodynamic inactivation,PDI)作用,提高光动力杀菌效果,本研究以乙二胺四乙酸(ethylene diamine tetraacetic acid,EDTA)为协同剂,对PDI的应用条件进行优化,探讨姜黄素联合EDTA对荧光假单胞菌生物膜的PDI作用,并进一步将姜黄素联合EDTA应用于新鲜猪肉的保鲜。结果表明,与空白组相比,0.5%(质量分数,下同)EDTA与75 μmol/L 姜黄素经光照(功率密度200 mW/cm2、波长460 nm、光照时间20 min),荧光假单胞菌的菌落数对数值减小了6.40(lg(CFU/mL)),玻璃及丙烯腈二乙烯丁二烯树脂(acrylonitrile-butadiene-styrene,ABS)板表面生物膜中荧光假单胞菌菌落数对数值分别减小4.57、6.60(lg(CFU/mL)),均显著高于单独使用姜黄素组的灭活效果(P<0.05)。新鲜猪肉经75 μmol/L姜黄素和0.5% EDTA处理并光照后(功率密度100 mW/cm2、波长460 nm、光照时间20 min),与空白组相比,保存到第10天其表面荧光假单胞菌菌落数对数值减小3.05(lg(CFU/mL)),质量损失率为2.14%,色差ΔE随姜黄素浓度增加而增大;且处理后的猪肉随贮藏时间的延长pH值变化缓慢。说明PDI处理对猪肉的感官品质影响较小,能较好地维持猪肉pH值,对猪肉表面荧光假单胞菌有显著抑制作用。结论:姜黄素联合EDTA的PDI处理显著延长了猪肉的保鲜期,本研究可为光动力技术在食品杀菌及贮藏保鲜中的应用提供新的理论参考和技术支持。  相似文献   
6.
赵雨航  郭蕾  马青松 《硅酸盐通报》2022,41(4):1395-1403
有机聚合物衍生陶瓷技术具有聚合物分子可设计性强、成型容易和制备温度低等优点,已经成为陶瓷及其复合材料的主要制备技术之一。裂解是陶瓷先驱体实现从有机到无机转化的关键步骤,对目标陶瓷的组成、结构和性能有着决定性的影响。在陶瓷先驱体中添加过渡金属进行催化裂解,可以改变其裂解行为,进而调控和拓展裂解产物的结构和性能。本文从不同过渡金属对陶瓷先驱体的催化裂解作用入手,总结了陶瓷先驱体催化裂解的研究现状,探讨了催化机理,并就后续深化研究与应用提出了发展建议。  相似文献   
7.
以α,ω-二羟基聚甲基三氟丙基硅氧烷为基胶、烃基三乙酰氧基硅烷为交联剂、气相法二氧化硅为补强填料、氧化铁红为耐热添加剂、γ-(2,3环氧丙氧)丙基三甲氧基硅烷(KH 560)为增粘剂、二月桂酸二丁基锡为催化剂,制成脱酸型单组分室温硫化(RTV-1)氟硅密封剂。探讨了基胶黏度、气相法二氧化硅用量、交联剂结构及用量对密封剂工艺性能和力学性能的影响。确定的较佳配方为100份黏度19 000 mPa·s的基胶、15份甲基三乙酰氧基硅烷、20份气相法二氧化硅、5份氧化铁红、2份KH 560、1份二月桂酸二丁基锡。按此配方得到的脱酸型RTV-1氟硅密封剂的工艺性能、常温力学性能、耐高温性能、耐油性能达到或超过国外同类产品的水平。  相似文献   
8.
首先,以全氟(2-甲基-3-氧杂己基)氟化物(六氟环氧丙烷二聚体)和N-(β-氨乙基)-γ-氨丙基三甲氧基硅烷(KH792)为原料制备一种氟化硅氧烷,用FTIR和1HNMR表征其结构.然后,将氟化硅氧烷与聚醚胺共同固化环氧树脂DGEBA(双酚A型二缩水甘油醚),测试了改性环氧树脂复合材料的性能.结果表明,与未改性环氧树脂相比,加入氟化硅氧烷使含氟量1%(以DGEBA质量计)改性环氧树脂复合材料的表面静态水接触角由72.0°增至103.2°,表面能由(42.08±2.17)mN/m降至(20.55±1.45)mN/m,40 d吸水率由1.75%降至1.38%,有效提高了材料的疏水性;介电常数由3.83降低至3.63;材料热分解5%温度由339℃升高至347℃;拉伸及弯曲力学性能分别提高了8.5%及7.7%.含氟量为1%时,改性环氧树脂复合材料的综合性能最佳,差式量热扫描和动态力学性能测试结果表明,少量改性剂可以促进环氧树脂的固化反应,提高固化度和交联密度;当氟化硅氧烷添加量增加时,材料内部发生显著的微相分离并导致性能逐渐下降.  相似文献   
9.
A new series of poly(azomethine-imide)s having siloxane moities in backbone was prepared using different dianhydrides.Thermal, optical, and morphological properties of these polymers were clarified. Also, bulky  CO and  CF3 group effects and meta or para-substituted aldeyhde effects on the mentioned properties were evaluated. The structural characterization of poly(azomethine-imide)s was carried out using a FT-IR spectroscopy. The optical properties of the polymers were performed via an UV–Vis spectrophotometer. Optical band gap of the poly(imide)s containing azomethine was calculated between 2.20 and 2.33 eV. Thermal behavior of poly(azomethine-imide)s was also studied using TG-DTA, DSC, and DMA techniques. The onset degradation temperature and percentage char values of the polyimides were found in the range from 429 to 545 °C and 22 to 35%, respectively. Thermal stability results demonstrated that benzophenone bearing poly(azomethine-imide)s have higher onset temperature, percentage char, and the glass transition temperature than poly(azomethine-imide)s derived from hexafluoroisopropylidene. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48364.  相似文献   
10.
Polysiloxane elastomers represent a widely utilized soft material with excellent rubber‐like elasticity, biocompatibility, and biodurability; however, there is a lack of an effective and straightforward approach to manipulate the material's viscoelastic response. A facile hydrosilylation reaction is employed to integrate ureidopyrimidinone hydrogen‐bonding side‐groups into linear and crosslinked siloxane polymers to achieve biocompatible soft materials with a highly tunable viscoelastic relaxation timescale. Stacking of H‐bonded moieties is avoided in the designed macromolecular architectures with tight, side‐groups substituents. The obtained siloxane network features the presence of both covalent crosslinks and truly thermoreversible crosslinks, and can be formulated across a broad material design space including elastic solids, recoverable viscoelastic solids, and viscous liquids. The elastomers exhibit unique temperature‐dependent shape‐memory capability and show good cytocompatibility. Importantly, a deformed material's shape‐recovery occurs regardless of external triggering, and through manipulation of network formulations, the shape‐recovery timescale can be easily tuned from seconds to days, opening new possibilities for biomedical, healthcare, and soft material applications.  相似文献   
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