全文获取类型
收费全文 | 6109篇 |
免费 | 220篇 |
国内免费 | 24篇 |
专业分类
电工技术 | 80篇 |
综合类 | 8篇 |
化学工业 | 1200篇 |
金属工艺 | 195篇 |
机械仪表 | 178篇 |
建筑科学 | 131篇 |
矿业工程 | 7篇 |
能源动力 | 448篇 |
轻工业 | 542篇 |
水利工程 | 73篇 |
石油天然气 | 88篇 |
武器工业 | 2篇 |
无线电 | 688篇 |
一般工业技术 | 1297篇 |
冶金工业 | 766篇 |
原子能技术 | 61篇 |
自动化技术 | 589篇 |
出版年
2023年 | 104篇 |
2022年 | 205篇 |
2021年 | 238篇 |
2020年 | 218篇 |
2019年 | 189篇 |
2018年 | 279篇 |
2017年 | 242篇 |
2016年 | 226篇 |
2015年 | 150篇 |
2014年 | 222篇 |
2013年 | 456篇 |
2012年 | 237篇 |
2011年 | 292篇 |
2010年 | 220篇 |
2009年 | 230篇 |
2008年 | 222篇 |
2007年 | 167篇 |
2006年 | 163篇 |
2005年 | 99篇 |
2004年 | 84篇 |
2003年 | 90篇 |
2002年 | 74篇 |
2001年 | 57篇 |
2000年 | 72篇 |
1999年 | 85篇 |
1998年 | 218篇 |
1997年 | 145篇 |
1996年 | 127篇 |
1995年 | 96篇 |
1994年 | 80篇 |
1993年 | 83篇 |
1992年 | 62篇 |
1991年 | 60篇 |
1990年 | 49篇 |
1989年 | 60篇 |
1988年 | 46篇 |
1987年 | 43篇 |
1986年 | 52篇 |
1985年 | 66篇 |
1984年 | 48篇 |
1983年 | 55篇 |
1982年 | 57篇 |
1981年 | 56篇 |
1980年 | 50篇 |
1979年 | 44篇 |
1978年 | 26篇 |
1977年 | 39篇 |
1976年 | 46篇 |
1974年 | 28篇 |
1973年 | 23篇 |
排序方式: 共有6353条查询结果,搜索用时 15 毫秒
991.
The catalytic oxidation of volatile organic compounds (VOCs) into mainly CO2 and H2O appears promising in the context of the abatement of atmospheric gaseous pollutants and is the subject of this paper. The catalytic oxidation of toluene and m-xylene was carried out in a tubular reactor on a phenolic resin based activated carbon fiber (ACF) impregnated with nitrates of Co, Cr, Ni, and Cu at the reaction temperatures below 300 °C. The extent of the removal (i.e. conversion) of toluene and m-xylene was examined through the breakthrough curves and was found to strongly depend on the types and loading of the metal precursors. The experimental results showed that the reaction rate was significantly affected by O2 concentration below 3% (v/v). The performance of the ACFs impregnated with 5% (w/w) of Ni oxide was found to be superior to that of other metal oxides at reaction temperature between 170 and 290 °C. A surface kinetic mechanism for the catalytic oxidation of volatile organic compound was proposed and incorporated in a transport model developed to explain the experimental breakthrough data. 相似文献
992.
993.
Conductivity of molten Mg(NO3)2. 6H2O + NH4NO3 system containing up to 80 mole percent of the latter was measured in the temperature range 320–400 K. Temperature dependence of conductivity exhibited Arrhenian behaviour. Conductivity—composition isotherms were non-linear indicating weak ordering tendencies. Equivalent conductivity data did not obey Markov equation; deviations have been interpreted in terms of the Tobolsky parameter (θ). Constancy of θ indicate that the water of hydration in the system remains with Mg2+ ions and is unaffected by the addition of NH+4 ions. 相似文献
994.
Calcium hexa-aluminate (CaO·6Al2 O3 ) has been prepared from calcium nitrate and aluminum sulfate solutions in the temperature range of 1000°–1400°C. A 0.3 mol/L solution of aluminum sulfate was prepared, and calcium nitrate was dissolved in it in a ratio that produced 6 mol of Al2 (SO4 )3 ·16H2 O for each mole of Ca(NO3 )2 ·4H2 O. It was dried over a hot magnetic stirrer at ∼70°C and fired at 1000°–1400°C for 30–360 min. The phases formed were determined by XRD. It was observed that CaO·Al2 O3 and CaO·2Al2 O3 were also formed as reaction intermediates in the reaction mix of CaO·6Al2 O3 . The kinetics of the formation of CaO·6Al2 O3 have been studied using the phase-boundary-controlled equation 1 − (1 − x )1/3 = K log t and the Arrhenius plot. The activation energy for the low-temperature synthesis of CaO·6Al2 O3 was 40 kJ/mol. 相似文献
995.
To obtain new polymeric materials for environmental management, we used pine needles from the huge forest of the Western Himalayas as a source of cellulose. Cellulose was derivatized to hydroxypropyl cellulose (HPC), a useful water‐soluble cellulose ether. HPC was graft‐copolymerized with acrylamide (AAm) with benzoyl peroxide as the initiator. At optimum grafting conditions, five different concentrations of the comonomers glycidyl methacrylate, acrylic acid, 2‐hydroxyethyl methacrylate, and acrylonitrile were grafted with AAm. Networks of HPC and AAm were also synthesized by crosslinking reactions with glutaraldehyde as a crosslinker over a range of four different concentrations of crosslinker under acidic conditions. Crosslinked networks of HPC with AAm and a comonomer at one comonomer concentration were also synthesized. Graft copolymers were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and swelling behavior. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 545–555, 2004 相似文献
996.
Enzyme-assisted aqueous extraction of peanut oil 总被引:13,自引:0,他引:13
Aparna Sharma S. K. Khare M. N. Gupta 《Journal of the American Oil Chemists' Society》2002,79(3):215-218
Enzyme-assisted aqueous extraction of oil from oilseeds is a relatively recent technique. In the present study, peanut oil
was extracted under optimized aqueous extraction conditions using Protizyme™, which is predominantly a mixture of acid, neutral, and alkaline proteases. The optimal conditions were: enzyme concentration
of 2.5% (w/w) in 10 g of peanut seeds, pH 4.0, 40°C, and 18 h incubation with constant shaking at 80 rpm. Centrifuging the
mixture at 18,000 × g for 20 min separated the oil with a recovery of 86–92%. The merits of this process over existing solvent extraction and/or
mechanical pressing methods are discussed. 相似文献
997.
Sabin Kumar Mishra Pradeep Kumar Jha Satish Chandra Sharma Satish Kumar Ajmani 《北京科技大学学报(英文版)》2011,18(5):535-542
In a multistrand,the outlet near the inlet produces short circuiting flow.This leads to the formation of dead zones inside the tundish,and consequently,the mean residence time decreases.In the present study,numerical investigation of mixing inside a delta shaped tundish with sloping boundaries was carried out by solving the Navier-Stokes equation and employing the standard turbulence model.To decrease the dead zone volume inside the tundish,the effect of closing the outlet near the inlet for a small amount of time and further opening it on the mixing behavior of the tundish was studied.The outlets near the inlet were closed for varying amount of time,and the transient analysis of fluid flow and the tracer dispersion study were carried out to find the mixing parameters of the tundish,namely,mean residence time and the ratio of mixed to dead volume of the tundish.An optimum closure time of the near outlet has been found,which yields best mixing inside the tundish.The numerical code was validated against the experimental observation by performing the tracer dispersion study inside a multistrand tundish and the reasonably good match between the experimental and numerical results in terms of residence time distribution (RTD)curves.The results obtained from the present study confirm the strong role of choosing the right time for opening and closing the outlets to get improved characteristics for the fluid flow and mixing behavior of the tundish.The educational version of computational fluid dynamics(CFD)soft ware PHOENICS was used to solve the governing equations and interpret the results in different forms. 相似文献
998.
Dharmendra Singh Yadav Dheeraj Sharma Sukeshni Tirkey Varun Bajaj 《Journal of Computational Electronics》2018,17(1):118-128
This paper presents a comparative analysis of the combined effects of gate underlapping and dual work functionality with hetero gate dielectric engineering for a charge plasma tunnel field-effect transistor (CP TFET). Ultrathin nanoscale devices, despite their size and cost advantage, present serious issues, including doping control, random dopant fluctuation and fabrication complexity. Given these concerns, the concept of charge plasma is introduced to avoid the need for conventional doping for the formation of the source and drain regions, which makes the device resistive to process variation. Conduction for negative gate bias (ambipolarity), excess Miller capacitance (gate-to-drain capacitance) and poor RF performance in TFETs are addressed by the use of gate underlapping from the drain side. In addition, enhanced ON-state current is obtained by work function shifting (dual work functionality). This shift in work function can be accomplished by nitrogen doping of the gate electrode for experimental levels [1]. The combined effects of the underlap and dual work function are seen in the device having a single gate dielectric. However, the ON-state current remains lower in the case of \(\mathrm{SiO}_{2}\) as the gate dielectric. Therefore, a hetero gate dielectric \(\mathrm{SiO}_{2}\) on the drain side and \(\mathrm{HfO}_{2}\) on the source side are considered in order to improve the RF parameters and enhance the ON-current concept, respectively. Finally, the combined effects of gate underlap with work function shift and hetero dielectric are analyzed in CP TFETs. The results show that proper underlap length and gate work function provide a significant improvement in device performance. Therefore, optimization of the underlap length and work function is performed to determine the specific work function that provides overall enhancement of DC and analog/RF performance of the device. In addition, optimization of the dual work function gate length is demonstrated. 相似文献
999.
Suman Jangra Bharti Sharma Rahul Jangra Vinod Chhokar Surender Duhan 《Journal of Porous Materials》2018,25(4):945-953
In this study, first time a nanoformulation, saponin-loaded SBA-15 has been developed for an improved and continuous release. The SBA-15 nanopowder was synthesized by a hydrothermal process. Saponin was introduced into the mesoporous channels of SBA-15 and its concentration in SBA-15 was measured by UV–visible spectrophotometry. The pristine SBA-15 and saponin-loaded SBA-15 were characterized by small-angle XRD, FESEM, HRTEM, TGA, FTIR. N2 adsorption–desorption isotherms were used to measure the specific surface area and pore channel structure parameters of pristine and loaded SBA-15. Saponin release was studied in phosphate buffered saline (pH 7.4), which revealed that the release rate could be effectively controlled. The controlled drug release is highly desired for cancer treatment. The cytotoxicity of pristine and loaded SBA-15 was analyzed on Panc-I cancer cells. Both the pristine SBA-15 and saponin-loaded SBA-15 nanoparticles showed specific toxicity on the cancer cells. The preliminary results showed that saponin-loaded SBA-15 could be an effective therapeutic agent for Panc-I cancer cells. 相似文献
1000.
Approaches in Cultural Computing: A Survey and Inference from Social Computing with Dynamics of Mind
Cultural computing is mainly viewed as the integration of computing technology with the culture. Being inherently interdisciplinary and multidimensional, it requires an explicit comprehension as the way it developed as well as expanded from the history of technological areas. This article addresses the need for cultural computing as well as comprehensively studies existing cultural computing approaches and models from different perspectives. An insight towards dynamics of mind and its incorporation in the virtual world of Internet and social computing has been provided. The article concludes with a summary providing useful suggestions for future developments. 相似文献