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991.
Haiding Sun Somak Mitra Ram Chandra Subedi Yi Zhang Wei Guo Jichun Ye Mohammad Khaled Shakfa Tien Khee Ng Boon S. Ooi Iman S. Roqan Zihui Zhang Jiangnan Dai Changqing Chen Shibing Long 《Advanced functional materials》2019,29(48)
High‐quality epitaxy consisting of Al1?xGaxN/Al1?yGayN multiple quantum wells (MQWs) with sharp interfaces and emitting at ≈280 nm is successfully grown on sapphire with a misorientation angle as large as 4°. Wavy MQWs are observed due to step bunching formed at the step edges. A thicker QW width accompanied by a greater accumulation of gallium near the macrostep edge than that on the flat‐terrace is observed on 4° misoriented sapphire, leading to the generation of potential minima with respect to their neighboring QWs. Consequently, a significantly enhanced photoluminescence intensity (at least ten times higher), improved internal quantum efficiency (six times higher at low excitation laser power), and a much longer carrier lifetime are achieved. Importantly, the wafer‐level output‐power of the ultraviolet light emitting diodes on 4° misoriented substrate is nearly increased by 2–3 times. This gain is attributed to the introduction of compositional inhomogeneities in AlGaN alloys induced by gallium accumulation at the step‐bunched region thus forming a lateral potential well for carrier localization. The experimental results are further confirmed by a numerical modeling in which a 3D carrier confinement mechanism is proposed. Herein, the compositional modulation in active region arising from the substrate misorientation provides a promising approach in the pursuit of high‐efficient ultraviolet emitters. 相似文献
992.
Mohammad Abu Yousuf Yoshinori Kobayashi Yoshinori Kuno Keiichi Yamazaki Akiko Yamazaki 《IEEJ Transactions on Electrical and Electronic Engineering》2019,14(12):1823-1835
The purpose of this study is to develop a mobile museum guide (MG) robot capable of creating and controlling spatial formations with visitors in different situations. Although much research has already been conducted in the area of nonverbal communication between guide robots and humans, the creation and controlling of spatial formations with multiple visitors is a fundamental function for MG robots that remains unexplored. Drawing upon psychological and sociological studies on the spatial relationships between humans, it is evident that to be effective MG robots should also possess the capability to create and control spatial formations in various situations. A MG robot needs to establish a spatial formation to initiate interaction with the visitors; a spatial formation is a prerequisite before the robot can begin explaining an exhibit. Moreover, the guide robot must be able to identify interested bystanders and invite them into an ongoing explanation session, necessitating a reconfiguring of the spatial formation. Finally, the robot must be able to do this while continuing to explain multiple exhibits in a cohesive fashion. To devise a system capable of meeting these needs, we began by observing and videotaping scenes of actual museum galleries. Based on analyzing these data, we found that MG creates spatial formation with the visitors in a systematic way. We then developed a mobile robot system able to create and control spatial formations while guiding multiple visitors. A particle filter framework is employed to track the visitors' positions and body orientations and the orientations of their heads. We then evaluated the guide robot system in a series of experiments that focused on different situations where a guide robot creates a spatial formation with visitors. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
993.
Khadije Abdolmaleki Mohammad Amin Mohammadifar Zhian Sheikhi Golshan Matinfar Kooshan Nayebzadeh 《Journal of the American Oil Chemists' Society》2019,96(7):795-803
Different emulsions based on six types of vegetable oils (sunflower, canola, sesame, olive, coconut, and palm olein) were studied to investigate the role of the oil phase in the stability and physicochemical characteristics of oil-in-water emulsions prepared with gum tragacanth. The results indicated that the stability, rheological parameters, and size distribution of emulsions were dependent on the oil type. Based on the interfacial tension value, the type of oil did not have a significant effect on the gum tragacanth-emulsifying properties. The formulation based on sunflower and coconut oil led to producing more stable emulsion and a sample containing palm olein resulted in an unstable emulsion. Rheological analysis revealed that the sample based on palm olein showed the lowest consistency coefficient (2.10 ± 0.05 Pas n), elastic modulus (3.90 ± 0.21 Pa), and energy of cohesion (80.87 ± 1.1 J m−3). This study revealed that using oils with lower viscosity and higher density led to the higher stability of the emulsion samples. 相似文献
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Nooshin Saadatkhah Seyedfoad Aghamiri Mohammad Reza Talaie Gregory S. Patience 《加拿大化工杂志》2019,97(8):2299-2308
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Seyed Mohammad Reza Paran Henri Vahabi Maryam Jouyandeh Franck Ducos Krzysztof Formela Mohammad Reza Saeb 《应用聚合物科学杂志》2019,136(20):47483
Thermally stable thermoplastic elastomer nanocomposites based on polyamide 6 (PA6), acrylonitrile butadiene rubber (NBR), and halloysite nanotubes (HNTs) were dynamically vulcanized, and their nonisothermal decomposition kinetics were examined. The Friedman, Kissinger–Akahira–Sunose (KAS), Ozawa–Wall–Flynn (FWO), and modified Coats–Redfern (m-CR) isoconversional models were used to obtain information about the kinetics of the thermal decomposition of PA6–NBR–HNTs in terms of the activation energy per partial mass loss monitored through thermogravimetric analyses performed at different heating rates. An erratic trend was due to the Friedman model, especially for systems having higher HNT loadings, whereas the KAS, FWO, and m-CR models revealed very similar meaningful thermal decomposition kinetics. A relatively high activation energy corroborating a reliable thermal stability was obtained by the addition of HNTs to PA6–NBR, and the resistance against decomposition was higher for systems containing more HNT. This signified the role of the HNTs as thermal stability modifiers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47483. 相似文献
1000.
Md. Hafezur Rahaman Md. Masud Rana Mohammad Abdul Gafur Anika Amir Mohona 《应用聚合物科学杂志》2019,136(18):47424
α-Cellulose extracted from jute fiber was grafted with oligo( d -lactic acid) (ODLA) via a graft polycondensation reaction in the presence of para-toluene sulfonic acid and potassium persulfate in toluene at 130 °C for 9 h under 380 mmHg. ODLA was synthesized by the ring-opening polymerization of d -lactides in the presence of stannous octoate (0.03 wt % lactide) and d -lactic acid at 140 °C for 10 h. Composites of poly( l -lactic acid) (PLLA) with the ODLA-grafted α-cellulose were prepared by the solution-mixing and film-casting methods. The grafting of ODLA onto α-cellulose was confirmed by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The analysis of the composites was performed with FTIR spectroscopy, SEM, wide-angle X-ray diffraction, and thermogravimetric analysis. The distribution of the grafted α-cellulose in the composites was uniform and showed better compatibility with PLLA through intermolecular hydrogen bonding. Only homocrystalline structures of PLLA were present in the composites, and the thermal stability increased with increasing percentage of grafted α-cellulose. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47424. 相似文献