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   218篇
  免费   26篇
  国内免费   2篇
电工技术   2篇
化学工业   57篇
金属工艺   5篇
机械仪表   10篇
建筑科学   4篇
矿业工程   1篇
能源动力   11篇
轻工业   9篇
水利工程   1篇
石油天然气   1篇
无线电   32篇
一般工业技术   66篇
冶金工业   13篇
自动化技术   34篇
  2024年   1篇
  2023年   9篇
  2022年   14篇
  2021年   11篇
  2020年   14篇
  2019年   14篇
  2018年   28篇
  2017年   13篇
  2016年   16篇
  2015年   8篇
  2014年   15篇
  2013年   11篇
  2012年   12篇
  2011年   15篇
  2010年   10篇
  2009年   13篇
  2008年   11篇
  2007年   3篇
  2006年   3篇
  2003年   2篇
  2002年   1篇
  2001年   1篇
  1999年   1篇
  1998年   2篇
  1997年   2篇
  1996年   5篇
  1994年   2篇
  1993年   1篇
  1992年   4篇
  1990年   2篇
  1984年   1篇
  1981年   1篇
排序方式: 共有246条查询结果,搜索用时 15 毫秒
121.
Image fusion has been receiving increasing attention in the research community in a wide spectrum of applications. Several algorithms in spatial and frequency domains have been developed for this purpose. In this paper we propose a novel algorithm which involves the use of fractional Fourier domains which are intermediate between spatial and frequency domains. The proposed image fusion scheme is based on decomposition of source images (or its transformed version) into self-fractional Fourier functions. The decomposed images are then fused by maximum absolute value selection rule. The selected images are combined and inverse transformation is taken to obtain the final fused image. The proposed decomposition scheme and the use of some transformation before the decomposition step offer additional degrees of freedom in the image fusion scheme. Simulation results of the proposed scheme for different transformation of the source images for two different sets of images are also presented. It is observed through the simulation results that the use of taking the transformation before the decomposition step improves the quality of fused image. In particular the results of using the fractional Fourier transform and discrete cosine transform before the decomposition step are encouraging.  相似文献   
122.
This study evaluated the capabilities of a high‐voltage technique for the detection of pinhole leaks by using flexible pouches and semi‐rigid cups for foods. This evaluation was performed by measuring the discharge voltage when high voltages ranging from 0.25 to 10 kV were applied to sample packages. The results showed that package contact surface area, film thickness, food type and electrical conductivity are significant factors affecting the detection of pinhole leaks in flexible pouches by a high‐voltage leak detection (HVLD) system within the ranges tested (p < 0.05). For plastic cups with plastic‐laminated and foil‐laminated lids, the headspace inside a cup had the greatest effect followed by dielectric constant of lid films, electrical conductivity of foods and pinhole diameter (p < 0.01). In general, the HVLD system can detect pinholes as small as 10 µm in both plastic‐laminated and foil‐laminated pouches and lid cups, even at worst‐case scenario conditions, including liquid, semi‐solid and solid foods with 0.85 aw. Because of high voltages applied, however, delamination in foil‐laminated films occurred when an applied voltage was greater than 3.5 kV, which resulted in increased oxygen permeability. Statistical z‐test analysis of results from blind studies showed that the HVLD technique is significantly effective in determining defective pouches and cups with pinhole leaks as small as 10 µm (p < 0.05). Therefore, it can be concluded that the HVLD technique is a promising non‐destructive and on‐line method to detect pinhole defects, which may be applicable to a wide range of hermetically sealed packages. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
123.
Generation deficit in India is in the range of 9% and the scenario is expected to get grimmer in the context of high growth rate of the country. With peak power shortage as high as 15.2% (Source: Annual report FY08, MoP) the nation needs to harness all forms of generation including renewables, which currently has a meager share of 8% of the total generation in the country at present. Shooting price of crude oil reaching up to $135 (May 2008) per barrel along with increasing awareness and concerns about environment, the stage seems to be set for an increased mix of Renewable Energy (RE) into the overall energy requirement in the country. Keeping the concern for environment and energy security for the country in mind, government of India has been putting emphasis on promotion of renewable energy sources. Central and state government policies have always been instrumental in the propagation of capacity additions in renewable energy power. One of the main aims of these policies has been on increasing the private sector participation in this sector. In the pre-reform period, the state governments took policy decisions regarding financial incentives, buy-back tariff and other measures targeting investment in renewable energy. However, the State Electricity Regulatory Commissions (SERCs) are now responsible for many of these tasks. SERCs have come up with a host of initiatives, inline with their functions laid down in the Electricity Act 2003, to increase the share of renewable energy inside their respective States. Despite the efforts of SERCs, large potential of renewable energy generation remains untapped. There is lack of clarity on how to promote renewable energy generation inside states which are not having significant renewable energy generation potential.This paper explores the way in which SERCs can introduce measures to further promote renewable energy generation inside the country. We discuss in detail the framework to promote renewable energy through a framework which puts into place Renewable Purchase Obligation (RPO) mechanism. The framework includes setting of RPO targets, provisions for a surcharge levied upon non-compliance of RPO targets and also a mechanism to meet RPO through trading of certificates.  相似文献   
124.
A common scenario in Third World countries is that with the overriding social, economic and political implications being so complex and vast, the actual resolution to urban problems and issues is often lost and the planning process stalls at the problem identification stage. The key to the resolution of the urban decline affecting the central business district of Bombay, Fort, is in accepting and understanding its cultural and architectural significance to the city, its potential to continue as the financial centre with the influx of multinational offices being set up in the city, and to stop the degeneration of a district which already has large-scale formal and informal sector investment. The main argument of the paper is that time is ripe for an innovative conservation strategy. The proposed strategy begins with an action plan that would be essential should a program for conservation be accepted by the city's decision makers. It is a move away from the current piecemeal approach of identifying singular buildings for preservation, and pursues a more holistic approach to protect, regulate and retain the built, economic and social fabric of Fort. Encouraged by the Kanga Commission's initiatives, the proposed approach shows the steps towards a bold but manageable long-term solution.  相似文献   
125.
We present a theoretical design of an all-optical reconfigurable logic unit based on optically controlled microcavity switches, for realization of all-optical computing circuits. It can execute different logic and arithmetic operations such as half and full adder or subtractor, by only changing the control inputs on the same circuit. Theoretical designs considering bacteriorhodopsin (BR) protein coated microcavities in tree architecture have been presented. The combined advantages of high Q-factor, tunability, compactness, switching of near-IR signals at telecom wavelengths (1310/1550 nm) with low-power control signals, and flexibility of cascading switches to form circuits, makes the designs promising for practical applications. They combine the ultrahigh sensitivity of both BR and microresonators to define a novel paradigm of all-optical computing based on hybrid nanobiophotonic integration.  相似文献   
126.
The magnesium doped zinc oxide is a promising optical material to enhance the luminescence for possible application in solid state lighting. Magnesium doped zinc oxide thin films (Zn0.85Mg0.15O) were deposited by sol-gel route on p-type silicon and annealed at different temperatures in oxygen environment for an hour. The doping of magnesium in zinc oxide was confirmed by X-Ray diffraction and the samples were found to have wurtzite crystal structure with (002) preferred orientation. The films were characterized by Hall-effect, atomic force microscopy, UV-VIS spectroscopy, photoluminescence (PL) and work function measurements. The different studies exhibited an anomalous behavior for the film annealed at 900 °C. The Hall effect, work function measurements and UV-VIS spectroscopy indicated that the resistivity, work function and optical band gap increased as a function of annealing temperature (from 300 °C to 700 °C) however these parameters were found to decrease for the films annealed above 700 °C. The particle size increased with the annealing but for the samples annealed at 900 °C, the shape of the grains changed and became elongated like fibers as observed by the atomic force microscopy. The PL measurements displayed the existence of oxygen vacancies defects for the samples annealed at and above 600 °C. The possible mechanism for this anomaly has been discussed in this work.  相似文献   
127.
Energy supplies particularly in remote and far-flung rural areas are in pathetic situation. Leave aside other needs, most of the rural communities still use wood as a source of energy for cooking. Burning of wood is not only an inefficient method, but also hazardousness for the person working on the stove. People have been working for cleaner and efficient means of cooking for decades. Solar cooker- and biogas-based cook stoves are two of the successfully implemented technologies in this area. Although solar cooker requires no maintenance, the initial investment is quite high for a cluster of villages. In addition to this, the intermittency involved in solar energy makes this an unreliable source.

In this paper, a cluster of villages of Narendra Nagar block of Tehri Garhwal district of Uttarakhand, India, has been studied in terms of their thermal requirements. The potential of solar energy and biomass energy has been estimated. An integrated solar–biogas system has been proposed to satisfy this cooking demand. To obtain the optimal sizes of solar cooker and biogas generator, MATLAB codes have been developed. It was found that this system is more economical and much reliable than the other two cases.  相似文献   

128.
Fiber treatments and coupling agents have been applied by composites researchers to improve the functionality in the flexural loading of natural fiber reinforced composites. This paper reviews how fiber treatments upshot to flexural strength and modulus of natural fiber composites during 2000–2016. Chemical treatments improved fiber interface bonding with matrix and impart more strengths to composites. Coupling agents also ameliorate flexural properties and the combination of treatments is equally supercilious. The negative impact of fiber’s physical treatments on flexural properties of natural fiber composites also reviewed. Eventually, a number of perspectives have been concluded with the hope that our work will succor to further betterment in flexural strength of natural fiber composites.  相似文献   
129.
130.
Axial-suspension-plasma spraying (ASPS) is a fairly recent thermal spray technology which enables production of ceramic top coats in TBCs, incorporating simultaneously the properties of both the conventional-plasma sprayed (highly insulating porous structures) and electron-beam-physical-vapor-deposited (strain-tolerant columnar structures) top coats. TBCs are required to insulate the hot components in a gas turbine engine against high temperature and harsh operating conditions. Periodic heating and cooling of turbine engines during operation can create severe thermal cyclic fatigue conditions which can degrade the performance of these coatings eventually leading to the failure. An in-depth experimental investigation was performed to understand the failure behavior of columnar TBCs subjected to thermal cyclic fatigue (TCF) test at 1100?C. The study revealed that the TCF performance was influenced to an extent, by the top coat microstructure, but was primarily affected by the severity of thermally grown oxide (TGO) growth at the bond coat-top coat interface. Mixed failure modes comprising crack propagation through the bond coat-TGO interface, through TGO and within the top coat were identified. Based on the analysis of the experimental results and thorough discussion a novel design of microstructure for the high TCF performance columnar TBC is proposed.  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