全文获取类型
收费全文 | 2000篇 |
免费 | 95篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 16篇 |
综合类 | 1篇 |
化学工业 | 343篇 |
金属工艺 | 113篇 |
机械仪表 | 39篇 |
建筑科学 | 41篇 |
矿业工程 | 2篇 |
能源动力 | 109篇 |
轻工业 | 127篇 |
水利工程 | 5篇 |
石油天然气 | 3篇 |
无线电 | 226篇 |
一般工业技术 | 511篇 |
冶金工业 | 161篇 |
原子能技术 | 24篇 |
自动化技术 | 379篇 |
出版年
2024年 | 7篇 |
2023年 | 33篇 |
2022年 | 67篇 |
2021年 | 60篇 |
2020年 | 52篇 |
2019年 | 73篇 |
2018年 | 92篇 |
2017年 | 80篇 |
2016年 | 90篇 |
2015年 | 58篇 |
2014年 | 71篇 |
2013年 | 163篇 |
2012年 | 112篇 |
2011年 | 126篇 |
2010年 | 98篇 |
2009年 | 100篇 |
2008年 | 105篇 |
2007年 | 88篇 |
2006年 | 63篇 |
2005年 | 54篇 |
2004年 | 52篇 |
2003年 | 36篇 |
2002年 | 37篇 |
2001年 | 27篇 |
2000年 | 23篇 |
1999年 | 22篇 |
1998年 | 22篇 |
1997年 | 30篇 |
1996年 | 20篇 |
1995年 | 24篇 |
1994年 | 26篇 |
1993年 | 23篇 |
1992年 | 17篇 |
1991年 | 17篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 17篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 18篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1971年 | 5篇 |
排序方式: 共有2100条查询结果,搜索用时 15 毫秒
41.
Kavita Krishnaswamy Ravi Kuber Tim Oates 《Universal Access in the Information Society》2016,15(4):609-627
Limb repositioning is necessary for individuals with severe physical disabilities to sustain muscle strength and prevent pressure sores. As robotic technologies become ubiquitous, these tools offer promise to support the repositioning process. However, research has yet to focus on ways in which individuals with severe physical disabilities can control robots for these tasks. This paper presents a study that examines the needs and attitudes of potential users with physical disabilities to control a robotic aid for limb repositioning. Subjects expressed interest in using brain–computer interface (BCI) and speech recognition technologies for purposes of executing robotic tasks. The performance of four subjects controlling arm movements on an avatar through the keyboard, mouse, BCI, and Dragon NaturallySpeaking speech recognition was evaluated. Although BCI and speech technologies may limit physical fatigue, more challenges were faced using BCI and speech conditions compared to the keyboard and mouse. This research promotes accessibility into mainstream robotic technologies and represents the first step in the development of a robotic prototype using a BCI and speech recognition technologies for limb repositioning. 相似文献
42.
43.
Ravi Shankar 《International Journal of Communication Systems》2023,36(16):e5585
In this work, a deep learning (DL)-based massive multiple-input multiple-output (mMIMO) orthogonal frequency division multiplexing (OFDM) system is investigated over the tapped delay line type C (TDL-C) model with a Rayleigh fading distribution at frequencies ranging from 0.5 to 100 GHz. The proposed bi-directional long short-term memory (Bi-LSTM) channel state information (CSI) estimator uses online learning during training and offline learning during the practical implementation phase. The design of the estimator takes into account situations in which prior knowledge of channel statistics is limited and targets excellent performance, even with limited pilot symbols (PS). Three separate loss functions (mean square logarithmic error [MSLE], Huber, and Kullback–Leibler Distance [KLD]) are assessed in three classification layers. The symbol error rate (SER) and outage probability performance of the proposed estimator are evaluated using a number of optimization techniques, such as stochastic gradient descent (SGD), momentum, and the adaptive gradient (AdaGrad) algorithm. The Bi-LSTM-based CSI estimator is trained considering a specific number of PS. It can be readily seen that by incorporating a cyclic prefix (CP), the system becomes more resilient to channel impairments, resulting in a lower SER. Simulations show that the SGD optimization approach and Huber loss function-trained Bi-LSTM-based CSI estimator have the lowest SER and very high estimation accuracy. By using deep neural networks (DNNs), the Bi-LSTM method for CSI estimation achieves a superior channel capacity (in bps/Hz) at 10 dB than long short-term memory (LSTM) and other conventional CSI estimators, such as minimum mean square error (MMSE) and least squares (LS). The simulation results validate the analytical results in the study. 相似文献
44.
Salunkhe Satish S. Pal Shelendra Agrawal Abhishek Rai Ravi Mole S. S. Sreeja Jos Bos Mathew 《The Journal of supercomputing》2022,78(6):8493-8508
The Journal of Supercomputing - This study offers a neural network-based deep learning method for energy optimization modeling in electric vehicles (EV). The pre-processed driving cycle is... 相似文献
45.
D. Raja Satish Fitsum Feyissa D. Ravi Kumar 《Materials and Manufacturing Processes》2017,32(12):1345-1352
Cryorolling is a severe plastic deformation (SPD) process used to obtain ultrafine-grained aluminum alloy sheets along with higher strength and hardness than in conventional cold rolling, but it results in poor formability. An alternative method to improve both strength and formability of cryorolled sheets by warm forming after cryorolling without any post-heat treatment is proposed in this work. The formability of cryorolled AA6061 Al alloy sheets in the warm working temperature range is characterized in terms of forming limit diagrams (FLDs) and limiting dome height (LDH). Strain distributions and thinning in biaxially stretched samples are studied. Hardness of the formed samples is correlated with ultimate tensile strength to estimate post-forming mechanical properties. The limit strains and LDH have been found to be higher than in the case of the conventional processing route (cold rolled, annealed and formed at room temperature), making this hybrid route capable of producing sheet metal parts of aluminum alloys with high strength and formability. In order to combine the advantages of enhanced formability and better post-forming strength than the conventional cold rolled and annealed sheets, warm forming at 250°C has been found to be suitable for this alloy in the temperature range that has been studied. 相似文献
46.
E. Vetrivendan G. Thendral A. Ravi Shankar C. Mallika 《Materials and Manufacturing Processes》2017,32(12):1435-1441
The insulation resistance of conventional atmospheric plasma-sprayed alumina coatings with 10–15% porosity is ~1011 Ω. The presence of pores, lamellae boundaries, and other non-fillings dampens the insulation resistance of the coating. In the present study, aluminum phosphate was used to seal the surface of plasma-sprayed alumina coating and evaluate the effect of sealing on the insulation resistance and its thermal cycling response. Sealing was carried out with three concentrations of sealant (P/Al molar ratio of 3, 10, and 15). Characterization by X-ray diffraction and scanning electron microscopy revealed the primary sealing phase as aluminum metaphosphate and effective sealing of the pores by the aluminum phosphate phases. Insulation resistance is improved by two orders of magnitude after sealing the coated samples. Sealing with P/Al molar ratio 3 exhibited maximum insulation resistance of ~1013 Ω at room temperature. Thermal cycling studies between 650°C and 200°C on the sealed samples showed deterioration in thermal cycling life after sealing. 相似文献
47.
Alumina ceramic is well documented as a much-demanded advanced ceramic in the present competitive structure of manufacturing and industrial applications owing to its excellent and superior properties. The current article aimed to experimentally investigate the influence of several process variables, namely: spindle speed, feed rate, coolant pressure, and ultrasonic power, on considered machining characteristics of interest, i.e., chipping size and material removal rate in the rotary ultrasonic machining of alumina ceramic. Response surface methodology has been employed in the form of a central composite rotatable design to design the experiments. Variance analysis testing has also been performed with a view to observing the consequence of the considered parameters. The microstructure of machined rod samples was evaluated and analyzed using a scanning electron microscope. This analysis has revealed and confirmed the presence of plastic deformation that caused removal of material along with brittle fractures in rotary ultrasonic machining of alumina ceramic. The validity and competence of the developed mathematical model have been verified with test results. The multi-response optimization of machining responses (material removal rate and chipping size) has also been attempted by employing a desirability approach, and at an optimized parametric setting the obtained experimental values for material removal rate and chipping size were 0.4166?mm3/s and 0.5134?mm, respectively, with a combined desirability index value of 0.849. 相似文献
48.
Sanjay Sahare Ravi Kant Choubey Gurunath Jadhav Tejashree M. Bhave Samrat Mukherjee Sunil Kumar 《Journal of Superconductivity and Novel Magnetism》2017,30(6):1439-1446
In this report, we studied various structural and optical properties of pure and copper-doped cadmium oxide (CdO) thin films. Nanostructured Cu-doped CdO films were deposited using sol–gel spin-coating technique. The structural and morphological changes have been observed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM) studies. The optical and electrical properties of the pure and Cu-doped CdO thin films were studied by UV–vis spectroscopy and four-point probe method, respectively. The XRD peaks show the formation of nanocrystalline CdO with cubic face-centered crystal structure. The band gaps of the as deposited films were found in the range of 2.32–2.73 eV, while after doping, it decreases due to structural deformation. The electrical resitivity was found to decrease approximately ~10 in Cu-doped CdO thin films. 相似文献
49.
Jayaprakash Vandana Kaliyur Ravi Shri Aishvarya Vinni Novi Swaroopini Ramachandran Hridya Radhakrishnan Vaidyanathan Vinoth Kumar 《IET nanobiotechnology / IET》2017,11(6):690
The present study deals with the production of 5‐hydroxymethyl furfural (HMF) from fructose by chemo‐conversion method using chemical catalyst, conventionally achieved by microwave‐assisted dehydration process. Five different chemical catalysts, namely oxalic acid, phosphotungstic acid and mesoporous titanium dioxide nanoparticles (TNPs) were compared at constant conditions of which TNPs yielded a maxima of 33.95%. The optimum temperature and catalyst loading were found to be 200°C and 20%, respectively, at a 5% optimum substrate concentration during 15 min optimum reaction time to yield 61.53% HMF. The efficiency of synthesised TNPs was investigated further through reusability studies. TNPs were properly recycled and the catalytic activity recovery was good even after a 14 batch reactions. The specific surface area of the TNP obtained is about 105.46 m2 /g and its pore‐volume is about 0.42 cm3 /g according to single point adsorption. A large accessible surface area combined with a minimal pore size (15.92 nm) obtained with mesoporous TNPs is desirable for better catalyst loading, high‐yield HMF, retention and reduced diffusion constraints.Inspec keywords: mesoporous materials, recycling, production management, dissociation, nanoparticles, nanotechnologyOther keywords: mesoporous titanium dioxide nanocatalyst, recyclable approach, one‐pot synthesis, 5‐hydroxymethyl furfural production, HMF, chemo‐conversion method, chemical catalyst, microwave‐assisted dehydration process, oxalic acid, phosphotungstic acid, mesoporous titanium dioxide nanoparticles, TNP 相似文献
50.
Rashmi Mahajan Akhshay Singh Bhadwal Nishant Kumar Mukil Madhusudanan Ramesh Namdeo Pudake Ravi Mani Tripathi 《IET nanobiotechnology / IET》2017,11(4):360
The present study reports a novel, facile, biosynthesis route for the synthesis of carbon nanodots (CDs) with an approximate quantum yield of 38.5%, using Musk melon extract as a naturally derived‐precursor material. The synthesis of CDs was established by using ultraviolet–visible (UV–vis) spectroscopy, Dynamic light scattering, photoluminescence spectroscopy, X‐ray diffraction, transmission electron microscopy and Fourier transform infrared (FTIR) spectroscopy. The as‐prepared CDs possess an eminent fluorescence under UV–light (λ ex = 365 nm). The size range of CDs was found to be in the range of 5–10 nm. The authors further explored the use of such biosynthesised CDs as a photocatalyst material for removal of industrial dye. Degradation of methylene blue dye was performed in a photocatalytic reactor and monitored using UV–vis spectroscopy. The CDs show excellent dye degradation capability of 37.08% in 60 min and reaction rate of 0.0032 min−1. This study shows that synthesised CDs are highly stable in nature, and possess potential application in wastewater treatment.Inspec keywords: carbon, nanostructured materials, nanofabrication, catalysis, photochemistry, ultraviolet spectra, visible spectra, photoluminescence, X‐ray diffraction, transmission electron microscopy, Fourier transform infrared spectra, fluorescence, dyesOther keywords: green synthesis, highly stable CD, photocatalytic performance, biosynthesis route, carbon nanodots, quantum yield, Musk melon extract, naturally derived‐precursor material, ultraviolet‐visible spectroscopy, dynamic light scattering, photoluminescence spectroscopy, X‐ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, FTIR spectroscopy, fluorescence, biosynthesised CD, photocatalyst material, industrial dye, methylene blue dye degradation, photocatalytic reactor, UV‐vis spectroscopy, wastewater treatment, size 5 nm to 10 nm, time 60 min 相似文献