全文获取类型
收费全文 | 2458篇 |
免费 | 192篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 21篇 |
综合类 | 3篇 |
化学工业 | 600篇 |
金属工艺 | 127篇 |
机械仪表 | 161篇 |
建筑科学 | 41篇 |
能源动力 | 140篇 |
轻工业 | 209篇 |
水利工程 | 21篇 |
石油天然气 | 5篇 |
武器工业 | 2篇 |
无线电 | 363篇 |
一般工业技术 | 510篇 |
冶金工业 | 112篇 |
原子能技术 | 54篇 |
自动化技术 | 286篇 |
出版年
2024年 | 3篇 |
2023年 | 28篇 |
2022年 | 41篇 |
2021年 | 97篇 |
2020年 | 62篇 |
2019年 | 64篇 |
2018年 | 87篇 |
2017年 | 87篇 |
2016年 | 89篇 |
2015年 | 80篇 |
2014年 | 120篇 |
2013年 | 165篇 |
2012年 | 220篇 |
2011年 | 252篇 |
2010年 | 158篇 |
2009年 | 187篇 |
2008年 | 137篇 |
2007年 | 90篇 |
2006年 | 99篇 |
2005年 | 88篇 |
2004年 | 70篇 |
2003年 | 61篇 |
2002年 | 49篇 |
2001年 | 53篇 |
2000年 | 53篇 |
1999年 | 44篇 |
1998年 | 66篇 |
1997年 | 25篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 15篇 |
1993年 | 11篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有2655条查询结果,搜索用时 15 毫秒
951.
A combined biological denitrification and sulfate precipitation process was developed to treat and reuse the spent brine produced by a nitrate exchange system. Although the spent brine contained a relatively high salt concentration, more than 80% of NO3(-)-N fed into the denitrification reactors was removed at a nitrate-N loading rate of 2.2 g NO3(-)-N/l x day, regardless of the presence or absence of sulfate up to 8,000 mg/l. Sulfate present in the spent brine was successfully removed by the addition of BaCl2 and the settling velocity of BaSO4 suspension was remarkably enhanced by FeCl3 coagulation. Since most of the chloride consumed in regenerating the exhausted resins was replaced during chemical treatment with BaCl2 and FeCl3, it was possible to reuse the treated spent brine as a regenerant after compensating for the small amount of unreplaced NaCl. 相似文献
952.
Byoung-Chan Bae Dong-Soo Park Young-Wook Kim Wonjoong Kim Byoung-Dong Han Hai-Doo Kim Chan Park 《Journal of the American Ceramic Society》2003,86(6):1008-1013
Silicon nitride ceramics seeded with 3 wt%β-Si3 N4 whiskers of two different sizes were prepared by a modified tape casting and gas pressure sintering. The fine whiskers had a higher aspect ratio than the coarse whiskers. Quantitative texture analysis including calculation of the orientation distribution function (ODF) was used for obtaining the degrees of preferred orientation of sintered samples. The maximum multiples of random distribution (mrd) values of samples seeded with the fine and coarse whiskers were large, greater than 15 and 9, respectively. Meanwhile, the mrd value of a sample seeded with fine whiskers was only 9 when it was prepared by conventional tape casting. The microstructures and the XRD data revealed that the well-aligned whiskers grew significantly after sintering and dominated the texture. Differences among the degrees of preferred orientation of the samples were explained using Jeffrey's model on rotation of elliptical particles carried by a viscous fluid. 相似文献
953.
Kyu -Seop Park Dong -Sik Bae Hyo -Jong Kim Chang -Yong Kang Sung-Keun Lee 《Metals and Materials International》2006,12(5):447-451
To determine the optimum method of producing TiAl intermetallic compounds with an oriented lamellar microstructure the authors
applied reactive diffusion and high-temperature deformation in a two-phase state on Ti-43 mol.%Al and Ti-46 mol.%Al. The reactive
diffusion process produces an α single-phase state with orientations that reflect the texture of the starting titanium foils;
the high-temperature deformation aims to rotate the lamellar interface by means of preferential activation of the crystal
slip systems that are parallel to the interface. The reactive diffusion process can effectively control the texture in an
α single-phase state, though many voids are formed at the initial stages of reactive diffusion. Furthermore, after the heating
process for the construction of the lamellar microstructure, uniaxial compression at 1323 K is quite effective for ensuring
that the lamellar interface is rotated parallel to the compression plane. Finally, the deformation causes about one half of
all the lamellae to be arranged within 20 degrees of the compression plane. 相似文献
954.
Luminescence properties of Y2−xGdxO3:Eu3+ (x = 0 to 2.0) thin films are investigated by site-selective laser excitation spectroscopy. The films were grown by pulsed laser deposition method on SiO2 (100) substrates. Cubic phase Y2O3 and Gd2O3 and monoclinic phase Gd2O3 are identified in the excitation spectrum of the 7F0 → 5D0 transition of Eu3+. The emission spectra of the 5D0 → 7FJ (J = 1 and 2) transition from individual Eu3+ centers were obtained by tuning the laser to resonance with each excitation line. The excitation line at around 580.60 nm corresponds to the line from Eu3+ with C2 site symmetry of cubic phase. New lines at 578.65 and 582.02 nm for the CS sites of Gd2O3 with monoclinic phase are observed by the incorporation of Gd in Y2O3 lattice. Energy transfer occurs between Eu3+ ions at the CS sites and from Eu3+ ions at the CS sites to those at the C2 site in Y2−xGdxO3. 相似文献
955.
Hyun Kyoung Yang Ye Ran Jeong Byung Chun Choi Jong Seong Bae Jung Hwan Kim 《Thin solid films》2008,516(7):1613-1616
The mechanism of enhancement of the red emission efficiency from CaTiO3:Pr3+ thin film by Al addition has been investigated. Al-ions have been attracting interest as a sensitizer to improve the luminescent efficiency of phosphors. Also, influence of Al-doping on the crystallization, surface morphology and luminescent properties of CaTiO3:Pr3+ thin films have been discussed. CaTiO3:Pr3+ and Al-doped CaTiO3:Pr3+ films were grown using pulsed laser deposition technique on Al2O3 (0001) substrates under different substrate temperatures and oxygen pressures. The crystalline phase and surface morphology of the films were very dependent on the oxygen pressure and substrate temperature and they affected the luminescent brightness of the films. The crystalline structure and microstructure of these films have been characterized by X-ray diffraction and electron microscopy and their luminescent properties have been evaluated at room temperature using a luminescence spectrometer and excitation by a broadband incoherent ultraviolet light source with a dominant excitation wavelength of 325 nm. In particular, the incorporation of Al3+ ions into CaTiO3 lattice could induce a remarkable increase of photoluminescence. The enhancement of luminescence for Al-doped films may result not only from the improved crystallinity but also from the reduced internal reflections caused by rougher surfaces. Also, the luminescent intensity and surface roughness of the films exhibited similar behavior as a function of oxygen pressure. 相似文献
956.
Safety climate survey was sent to 642 plants in 2003 to explore safety climate practices in the Korean manufacturing plants, especially in hazardous chemical treating plants. Out of 642 plants contacted 195 (30.4%) participated in the surveys. Data were collected by e-mail using SQL-server and mail. The main objective of this study was to explore safety climate practices (level of safety climate and the underlying problems). In addition, the variables that may influence the level of safety climate among managers and workers were explored. The questionnaires developed by health and safety executive (HSE) in the UK were modified to incorporate differences in Korean culture. Eleven important factors were summarized. Internal reliability of these factors was validated. Number of employees in the company varied from less than 30 employees (9.2%) to over 1000 employees (37.4%). Both managers and workers showed generally high level of safety climate awareness. The major underlying problems identified were inadequate health and safety procedures/rules, pressure for production, and rule breaking. The length of employment was a significant contributing factor to the level of safety climate. In this study, participants showed generally high level of safety climate, and length of employment affected the differences in the level of safety climate. Managers' commitment to comply safety rules, procedures, and effective safety education and training are recommended. 相似文献
957.
958.
The influence of CO2 on the deactivation of Co/γ-Al2O3 Fischer–Tropsch (FT) catalyst in CO hydrogenation has been investigated. The presence of CO2 in the feed stream reveals a negative effect on catalyst stability and in the formation of heavy hydrocarbons. The CO2 acts as a mild oxidizing agent on cobalt metal during Fischer–Tropsch synthesis. During FT synthesis on Co/γ-Al2O3 of 70 h, the CO conversion and C5+ selectivity in the presence of CO2 decreased more significantly than in the absence of CO2. CO2 is found to be responsible for the partial oxidation of surface cobalt metal at FT synthesis environment with the co-existence of generated water. 相似文献
959.
Inyong Kang Sangho Yoon Gyujong Bae Jung Hyun Kim Joongmyeon Bae Daehoon Lee Younghoon Song 《Catalysis Today》2008,136(3-4):249
This study investigated two factors affecting the performance of diesel autothermal reforming (ATR): the reforming activity of selected catalysts and the effect of devised fuel delivery apparatuses. When fluorite and perovskite-structured ceramic materials were used as substrates, H2 yields were higher than when an inert Al2O3 substrate was used at 700–800 °C. Gadolinium (Gd)-doped CeO2 (CGO) had the highest H2 production rate in the selected substrates. Platinum (Pt) showed better performance than rhodium (Rh) and ruthenium (Ru) when CGO was used as the substrate. Although the nickel (Ni)-added Pt catalyst (Pt–Ni) showed high H2 yield, carbon deposition over this catalyst was more severe than with Pt. Oxygen ion (O2−) vacancies generated by Gd dopants can enhance the reforming activity of CeO2. When using a microchannel catalyst bed, the performance degradation at high gas flowrates can be compared to a packed catalyst bed of pellet type. For effective fuel delivery, we have introduced an ultrasonic injector (UI) and a plasma injector (PI). The UI-reforming showed greater long-term stability than non-UI reforming because the generation of carbon precursors was suppressed. On the other hand, the PI-reformer had low conversion efficiency, although it had high H2 selectivity. 相似文献
960.
Cycloadditive reaction of fullerene[C60] with various 2'-azidoethyl per-O-acetyl glycopyranoside of D-mannose, D-galactose, D-glucose, D-xylose and D-maltose, respectively gave the glycosyl fullerene[C60] derivatives 2a-2e such as alpha-D-mannosyl fullerene[C60] under ultrasonication. Based on analyses using 1H- and 13C-NMR, UV-vis, FT-IR, and FAB-MS spectroscopies of the glycosyl fullerene[C60] derivatives, the products were composed of a mixture of [5,6]- and [6,6]-junction isomers which were predominantly the closed [5,6]-junction isomer. 相似文献