首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1225篇
  免费   55篇
  国内免费   5篇
电工技术   48篇
化学工业   287篇
金属工艺   16篇
机械仪表   32篇
建筑科学   46篇
矿业工程   1篇
能源动力   63篇
轻工业   98篇
水利工程   9篇
石油天然气   1篇
无线电   148篇
一般工业技术   229篇
冶金工业   149篇
原子能技术   10篇
自动化技术   148篇
  2024年   4篇
  2023年   19篇
  2022年   33篇
  2021年   67篇
  2020年   44篇
  2019年   38篇
  2018年   45篇
  2017年   42篇
  2016年   38篇
  2015年   31篇
  2014年   46篇
  2013年   64篇
  2012年   62篇
  2011年   73篇
  2010年   57篇
  2009年   59篇
  2008年   68篇
  2007年   32篇
  2006年   40篇
  2005年   37篇
  2004年   30篇
  2003年   21篇
  2002年   23篇
  2001年   24篇
  2000年   32篇
  1999年   19篇
  1998年   31篇
  1997年   16篇
  1996年   25篇
  1995年   25篇
  1994年   15篇
  1993年   11篇
  1992年   12篇
  1991年   12篇
  1990年   5篇
  1989年   4篇
  1988年   9篇
  1987年   10篇
  1986年   12篇
  1985年   3篇
  1984年   9篇
  1983年   4篇
  1982年   2篇
  1981年   3篇
  1980年   8篇
  1979年   4篇
  1976年   6篇
  1975年   2篇
  1970年   1篇
  1955年   2篇
排序方式: 共有1285条查询结果,搜索用时 62 毫秒
21.
The Journal of Supercomputing - This paper designs and develops a computational intelligence-based framework using convolutional neural network (CNN) and genetic algorithm (GA) to detect COVID-19...  相似文献   
22.
Electromagnetic wideband absorption is still perceived as a critical and formidable challenge to address with an unambiguous photonic absorber. Subwavelength metamaterial (MM) unit cells with unique and controlled features have recently gained considerable interest. However, meta-atoms, generated using a quantum-inspired pattern distribution, are underwhelming in existing literature to design photonic absorbers and their potential application to manufacture solar sails is still quite uncommon. In this article, to create a flexible, polarization-insensitive, ultrathin, and broadband MM absorber, quantum interference pattern-inspired design is utilized. Herein, a novel approach to fabricating solar sails for the space exploration incorporates the proposed broadband photonic absorber rather than conventional reflectors. The quantum-inspired meta-absorber (QIMA) exhibits an absorption of over 91% for the visible domain, i.e., 380–800 nm under a conventional plane-polarized source. It is shown in the study that broadband absorbers are almost equivalent to excellent reflectors to design the solar sails in terms of the time-averaged force calculated by utilizing the Maxwell stress tensor method. Thus, the QIMA has the potential to be a viable alternative to reflectors in the design of futuristic solar sails for space exploration. The interference theory model is also utilized to assure the dependability of calculated data, and additionally, the standard AM1.5 solar spectrum is utilized to demonstrate the QIMA's solar-harvesting potentiality.  相似文献   
23.
Colon cancer is the second major cause of cancer related deaths in industrial nations. Computed tomographic colonography (CTC) has emerged in the last decade as a new less invasive colon diagnostic alternative to the usually practiced optical colonoscopy. The overall goal is to increase the effectiveness of virtual endoscopic navigation of the existing computer-aided detection (CAD) system. The colonic/haustral folds serve as important landmarks for various associated tasks in the virtual endoscopic navigation like prone–supine registration, colonic polyp detection and tenia coli extraction. In this paper, we present two different techniques, first in isolation and then in synergism, for the detection of haustral folds. Our input is volumetric computed tomographic colonography (CTC) images. The first method, which uses a combination of heat diffusion and fuzzy c-means algorithm (FCM), has a tendency of over-segmentation. The second method, which employs level sets, suffers from under-segmentation. A synergistic combination, where the output of the first is used as an input for the second, is shown to improve the segmentation quality. Experimental results are presented on digital colon phantoms as well as real patient scans. The combined method has a total erroneous (over-segmentation plus under-segmentation) detection of (6.5 ± 2)% of the total number of folds per colon as compared to (12.5 ± 5)% for the diffusion-FCM-based method and (11.5 ± 3)% for the level set-based method. The p-values obtained from the associated ANOVA tests indicate that the performance improvements are statistically significant.  相似文献   
24.
Fuzzy hypersemigroups   总被引:1,自引:0,他引:1  
We introduce the notions of fuzzy hypersemigroup, fuzzy hypergroup, fuzzy hyperideal, homomorphism, hyper congruence, fuzzy homomorphism, fuzzy hypercongruence. The purpose of this note is the study of some characterization of fuzzy hypersemigroup, fuzzy hyperideal of a fuzzy hypersemigroup and homomorphism and hypercongruence on a hypersemigroup.  相似文献   
25.
The chlorination of drinking water forms various disinfection by-products (DBPs), some of which present potential risks to humans. This study investigates occurrences, trends, and regional and seasonal variability of DPBs in two Canadian provinces: Ontario and Quebec. The findings demonstrate that trihalomethanes (THMs) and haloacetic acids (HAAs) can be represented better by region-based analysis than by province-based analysis. THMs in summer months are much higher than in cold months, while HAAs show variable results. The seasonal and regional variability of DBPs can have implications for the selection of DBP sampling locations, sampling frequency, regulatory limitations of DBPs, exposure analysis and risk characterization.  相似文献   
26.
ABSTRACT

Water is one of the top priority item s i relief activities but the appropriateness and effectiveness of this activity may be questioned. Water and sanitation (WS) are inseparable and together they play major roles in the transmission of the pathogen of diarrhoeal disease. Thousands of people die or suffer from WS-related diseases during postdisaster periods. Here we present WS-related experiences gained after Bangladesh's 1991 cyclone and the views of participants in a regional and a national (local) workshop on this matter held in Bangladesh. About 63 per cent of the water purifying tablets (WPTs) distributed after the 1991 cyclone were found to have lost potency Relief personnel lack basic knowledge about WS practices and the management of WS provision. Participants in the two workshops documented serious problems i this field at both regional and national levels. Major issues for research may include: an appropriate environmental preparedness plan; appropriate waste disposal technologies; appropriate water treatment methods; self- help activities during vulnerable periods; and health education related to WS in disaster situations.  相似文献   
27.
An SOI based hyperbolic paraboloid geometry capacitive micromachined ultrasonic transducer (CMUT) array has been fabricated to realize a frequency independent constant beamwidth broadband beamforming capability. Detailed fabrication and packaging techniques are presented along with measurement results on individual CMUT cells for transient and steady-state response using a Polytec laser Doppler vibrometer. The measurement results are compared with analytical and 3-D electromechanical finite element analysis using IntelliSuite?. The measured results are in excellent agreement with analytical and FEA results. Measurement results also show that the CMUTs exhibit a flat bandwidth within the specified frequency range. SEM inspection also shows very close agreement between mask features and fabricated geometry that ensures reproducibility of the device with a high degree of fidelity. The CMUT array has been designed for automotive blindspot detection application and works in the 113–167?kHz range.  相似文献   
28.
A new dinuclear complex [Cu2(OAc)2(OH)(dpa)2] PF6 · H2O (1) is prepared and structurally and magneto-structurally characterized. The monocationic core contains one acetate in familiar bidentate η112-bridge and another in the rare monoatomic bridge along with one hydroxo intermediary. 1 packs through N–H…O and O–H…O hydrogen bonds and π…π interaction resulting a 3D supramolecular continuum and displays high-energy intraligand 1(π − π*) fluorescence and intraligand 3(π − π*) phosphorescence in glassy solution.  相似文献   
29.
A novel approach has been taken to produce (1) spherical Al2O3 particles by decarbonisation and (2) spherical AlN particles by nitridation and subsequent decarbonisation of C@Al2O3 composite particles. C@Al2O3 composite particles have been prepared by heterogeneous nucleation and crystallisation of Al(NO3)3 on surfactant encapsulated carbon nano particles followed by evaporative decomposition of the nitrate. Overpressure (0.4 MPa) of nitrogen and a temperature range (1723–1873 K) have been used for nitridation. Whiskers as well as spherical particles of AlN have been observed in the final product. The final product has been characterised by X-Ray Diffraction, Scanning Electron Microscope and Carbon–Hydrogen–Nitrogen content analysis by Elemental Analyser and the mechanism of the nitridation reaction has been analysed. The average size of the spherical AlN particles consisting of crystallites in nano-dimensions (30–50 nm) could be varied from 100 nm to 8 μm by changing the composition of the sol.  相似文献   
30.
Displacement Following of Hidden Objects in a Video Sequence   总被引:1,自引:0,他引:1  
In a video sequence, computing the motion of an object requires the continuity of the apparent velocity field. This property does not hold when the object is hidden by an occlusion during its motion. The minimization of an energy functional leads to a simple algorithm which allows the recovery of the most likely trajectory of the occluded object from optical flow data at the border of the occlusion. Optical flow used for developing our method is an improvement on any variational technique of computing it. This improvement is based on a multichannel segmentation.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号