全文获取类型
收费全文 | 2556篇 |
免费 | 84篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 45篇 |
综合类 | 5篇 |
化学工业 | 453篇 |
金属工艺 | 87篇 |
机械仪表 | 54篇 |
建筑科学 | 40篇 |
能源动力 | 93篇 |
轻工业 | 151篇 |
水利工程 | 18篇 |
石油天然气 | 7篇 |
无线电 | 188篇 |
一般工业技术 | 505篇 |
冶金工业 | 714篇 |
原子能技术 | 5篇 |
自动化技术 | 285篇 |
出版年
2023年 | 34篇 |
2022年 | 54篇 |
2021年 | 73篇 |
2020年 | 81篇 |
2019年 | 76篇 |
2018年 | 94篇 |
2017年 | 78篇 |
2016年 | 74篇 |
2015年 | 51篇 |
2014年 | 82篇 |
2013年 | 156篇 |
2012年 | 93篇 |
2011年 | 127篇 |
2010年 | 76篇 |
2009年 | 81篇 |
2008年 | 99篇 |
2007年 | 63篇 |
2006年 | 66篇 |
2005年 | 55篇 |
2004年 | 40篇 |
2003年 | 47篇 |
2002年 | 45篇 |
2001年 | 33篇 |
2000年 | 37篇 |
1999年 | 50篇 |
1998年 | 195篇 |
1997年 | 129篇 |
1996年 | 113篇 |
1995年 | 52篇 |
1994年 | 64篇 |
1993年 | 56篇 |
1992年 | 23篇 |
1991年 | 23篇 |
1990年 | 25篇 |
1989年 | 25篇 |
1988年 | 23篇 |
1987年 | 22篇 |
1986年 | 22篇 |
1985年 | 20篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1977年 | 9篇 |
1976年 | 16篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1971年 | 4篇 |
排序方式: 共有2650条查询结果,搜索用时 265 毫秒
61.
R. Ramesh M. A. Mannan A. N. Poo 《International Journal of Machine Tools and Manufacture》2003,43(4):435
Thermal error in machine tools has been observed to be closely linked to the temperature of critical elements of the machine. It was found, in the experiments conducted herein, that there was a significant increase in the axis positioning error on account of an increase in the temperature of the machine elements due to continuous operation. However, it was also observed that the specific operating parameters of the test cycles carried out also significantly affected the positioning error. Different sets of operating parameters generated significantly different error values even though the temperature of the machine elements generated by those operating conditions was similar. As such, this observation forms a very important consideration in the development of a generic thermal error compensation system. It appears to indicate that such a system needs to be capable of evaluating the compensation depending upon the temperature values of the machine elements as well as account for the effect that different operating parameters induce upon the positioning error under the same thermal condition of the machine. This paper attempts to analyse the thermal behaviour of a three-axis vertical machining centre under the influence of various operating parameters and, through the experimental results obtained, point out and explain the effect of these parameters on the axis positioning error. This behaviour forms the basis of an improved modelling methodology that is presented separately in Part II of this paper. 相似文献
62.
E. Titus N. Ali G. Cabral J. Gracio P. Ramesh Babu M. J. Jackson 《Journal of Materials Engineering and Performance》2006,15(2):182-186
This article reports key findings on the chemical functionalization of carbon nanotubes (CNT). The functionalization of chemical
vapor-deposited CNT was carried out by treating tubes with polyvinyl alcohol through ultrasonication in water with the aid
of a surfactant. The surfactant is expected to promote the unbundling of aggregated CNT. The characterization of functionalized
samples using thermogravimetric analysis, Fourier transform infrared spectroscopy, and Raman spectroscopy revealed that the
CNT were functionalized by the interaction of carboxylic acid and hydroxyl groups. From the characterization studies, it is
apparent that there is a strong interaction between these functional groups and the covalently bonded carbon in the CNT network.
The functionalization process enabled good CNT dispersion in the solution, and the CNT remained in suspension for many days.
To support the effective functionalization of the tubes, the interaction of functionalized CNT with Ni ions is also demonstrated.
This paper was presented at the fourth International Surface Engineering Congress and Exposition held August 1–3, 2005 in
St. Paul, MN. 相似文献
63.
Isolation enhancement between tightly spaced compact unidirectional patch‐antennas on multilayer EBG surfaces 下载免费PDF全文
In this article, ultracompact unidirectional patch antennas are used in different two‐antenna systems for biomedical applications at 5.2 GHz. Multilayer mushroom type electromagnetic bandgap (EBG) structures are designed as slow‐wave medium to reduce the size of the individual patch antennas to 0.1λ0 by 0.18λ0. Various techniques are investigated herein to improve antenna isolation for an enhanced Multiple‐Input Multiple‐Output (MIMO) performance. First, the coupling between 0.3λ0‐spaced antennas is verified to occur dominantly through radiation and near‐field coupling between the patches rather than through substrate‐bound modes. Second, various configurations are proposed to suppress antenna coupling. These approaches include reorientation of the antennas and employment of parasitic radiators between the patches. A novel design is presented in which a unidirectional parasitic slot radiator on an EBG reflector is inserted between the antennas to decouple them. Measurement results confirm efficacy of these approaches in mitigating antenna coupling by more than 11 dB in the operating bandwidth of the antennas. The compact patch antennas maintain efficiency values of higher than 70%. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:30–38, 2015. 相似文献
64.
We advocate the use of quickly‐adjustable, computer‐controlled color spectra in photography, lighting and displays. We present an optical relay system that allows mechanical or electronic color spectrum control and use it to modify a conventional camera and projector. We use a diffraction grating to disperse the rays into different colors, and introduce a mask (or LCD/DMD) in the optical path to modulate the spectrum. We analyze the trade‐offs and limitations of this design, and demonstrate its use in a camera, projector and light source. We propose applications such as adaptive color primaries, metamer detection, scene contrast enhancement, photographing fluorescent objects, and high dynamic range photography using spectrum modulation. 相似文献
65.
Khorassani Kawthar Shafie Chen Chen-Chun Ramesh Bharath Shafi Aamir Subramoni Hari Panda Dhabaleswar K. 《计算机科学技术学报》2023,38(1):128-145
Journal of Computer Science and Technology - The Slingshot interconnect designed by HPE/Cray is becoming more relevant in high-performance computing with its deployment on the upcoming exascale... 相似文献
66.
Pal Tumpa Saha Ramesh Biswas Suparna 《International Journal of Wireless Information Networks》2022,29(3):373-392
International Journal of Wireless Information Networks - In this work, energy efficient routing protocol variants considering different sink mobility in hierarchical cluster based wireless sensor... 相似文献
67.
Ayman Altameem Jaideep Singh Sachdev Vijander Singh Ramesh Chandra Poonia Sandeep Kumar Abdul Khader Jilani Saudagar 《计算机系统科学与工程》2022,42(3):1095-1107
Brain-computer interfaces (BCIs) records brain activity using electroencephalogram (EEG) headsets in the form of EEG signals; these signals can be recorded, processed and classified into different hand movements, which can be used to control other IoT devices. Classification of hand movements will be one step closer to applying these algorithms in real-life situations using EEG headsets. This paper uses different feature extraction techniques and sophisticated machine learning algorithms to classify hand movements from EEG brain signals to control prosthetic hands for amputated persons. To achieve good classification accuracy, denoising and feature extraction of EEG signals is a significant step. We saw a considerable increase in all the machine learning models when the moving average filter was applied to the raw EEG data. Feature extraction techniques like a fast fourier transform (FFT) and continuous wave transform (CWT) were used in this study; three types of features were extracted, i.e., FFT Features, CWT Coefficients and CWT scalogram images. We trained and compared different machine learning (ML) models like logistic regression, random forest, k-nearest neighbors (KNN), light gradient boosting machine (GBM) and XG boost on FFT and CWT features and deep learning (DL) models like VGG-16, DenseNet201 and ResNet50 trained on CWT scalogram images. XG Boost with FFT features gave the maximum accuracy of 88%. 相似文献
68.
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
69.
Ferroelectrically Gated Atomically Thin Transition‐Metal Dichalcogenides as Nonvolatile Memory 下载免费PDF全文
70.
Sanjay B. Bansode Ramesh S. Kapadnis Abu S. Ansari Vasant G. Wagh Anil N. Kulkarni Sampat S. Kale Habib M. Pathan 《Journal of Materials Science: Materials in Electronics》2016,27(12):12351-12356
Films of indium selenide was deposited onto glass and indium tin oxide coated glass substrates in acidic medium using chemical bath deposition at room temperature. Indium sulphate and sodium selenosulphate were used as precursors of In3+ and Se2?, respectively. The structural, surface morphological and optical properties of the deposited films were studied. Diffractograms in structural study revealed the deposited material is In2Se3 films. Controlled bath conditions resulted in the evolution of the In2Se3 microrod-like morphology. The optical band gap of the film was found to be 1.7 eV. 相似文献