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   1381篇
  免费   104篇
电工技术   10篇
综合类   2篇
化学工业   419篇
金属工艺   5篇
机械仪表   30篇
建筑科学   71篇
矿业工程   5篇
能源动力   27篇
轻工业   295篇
水利工程   64篇
石油天然气   5篇
无线电   69篇
一般工业技术   188篇
冶金工业   129篇
原子能技术   13篇
自动化技术   153篇
  2024年   5篇
  2023年   14篇
  2022年   18篇
  2021年   94篇
  2020年   42篇
  2019年   55篇
  2018年   59篇
  2017年   54篇
  2016年   57篇
  2015年   52篇
  2014年   58篇
  2013年   114篇
  2012年   75篇
  2011年   111篇
  2010年   64篇
  2009年   71篇
  2008年   75篇
  2007年   71篇
  2006年   63篇
  2005年   55篇
  2004年   34篇
  2003年   29篇
  2002年   29篇
  2001年   31篇
  2000年   10篇
  1999年   7篇
  1998年   23篇
  1997年   25篇
  1996年   15篇
  1995年   11篇
  1994年   9篇
  1992年   12篇
  1991年   3篇
  1990年   3篇
  1989年   6篇
  1988年   1篇
  1987年   6篇
  1986年   5篇
  1985年   2篇
  1984年   3篇
  1983年   2篇
  1982年   1篇
  1981年   2篇
  1977年   4篇
  1976年   1篇
  1975年   1篇
  1973年   1篇
  1972年   1篇
  1960年   1篇
排序方式: 共有1485条查询结果,搜索用时 62 毫秒
71.
Honeys from different regions of the province of Buenos Aires were stored at ?20°C, and factors that affect crystallization were analyzed. Crystals were observed by light microscopy. Firmness, adhesivity and viscosity of the samples were measured. Honey was characterized by determining the water activity, turbidity, moisture, fructose, and glucose contents. Results show that the viscous characteristics of the samples depend on the number, size, and disposition of crystals. Various honey samples exhibited Newtonian, pseudoplastic, and thixotropic behaviors. Crystallization was favored at higher moisture contents, suggesting that the parameters that affect honey crystallization at room temperature have a different effect at freezing temperatures. Honey that presented higher values of firmness had a moisture content lower than 17%, and a linear inverse relationship was observed between the adhesivity and firmness of honey samples.  相似文献   
72.
The amount of data generated by the infra-red and visible cameras at ITER is expected to be considerably larger than most diagnostics. ITER will have 12 infra-red cameras plus 12 visible cameras in four different equatorial port plugs. Each of the ports will have a Plant System Host (PSH) that will provide a standard image of the plant system to the ITER's Control and Data Access and Communication (CODAC) system.The two key functions of these cameras will be the scientific exploitation with the detection of interesting physics events and the operational protection of the machine, namely the first wall. Already assuming high bandwidth requirements for both audio and video, ITER will provide a separate network for this kind of communication, which will be used to transmit both the experimental and informational data provided by the cameras.This paper presents the current camera plant system design and its interaction with ITER CODAC system and networks. Starting from the camera specifications several alternatives for data collection and compression are discussed. The required inputs from CODAC and a first specification for the internal finite state machine are also presented. Finally, a possible hardware straw man design solution for the plant system hardware is proposed.  相似文献   
73.
Large numbers of households in rural areas in Bangladesh have no access to electricity. Providing these households with electricity by extending the country’s already overloaded grids is neither an economically nor a technically feasible option. Rural electrification strategies therefore, by necessity, need to rely on stand-alone generation systems. One of these is solar home systems (SHS) and the SHS program developed and implemented in Bangladesh has been highly successful, with very large numbers of rural households now participating in the program. What makes the program’s success most remarkable is the fact that it targets households with very low incomes using a purely market-based approach. Those participating in the program pay the full, unsubsidised cost of their SHS using a micro-credit loan facility and are charged high interest rates. Understanding the reasons behind the success of the Bangladeshi program therefore holds potentially valuable lessons for SHS programs being implemented in other developing countries. A comprehensive qualitative and quantitative survey was used to find those factors perceived by program stakeholders as being most critical to the program’s success to date and the factors considered most likely to impact on its future success. The two primary reasons for the program’s success were perceived to be its strong focus on meeting householders’ needs and on its ability to make the solar home systems as affordable as possible. The continued success of the program was considered likely to be determined by a variety of factors, including the ability of program implementers to control increases in the cost of SHS, to maintain the quality of SHS and components and to increase program loan recovery rates, the degree to which the program is integrated into national, energy policy, and the degree to which local banks become involved in the program.  相似文献   
74.
75.
This study investigated, with the aim of obtaining more flexible and hydrophobic proteins, the attachment of a low chain fatty acid, decanoic acid, to alkaline and acid soybean proteins; and the effect on their conformational and functional properties. The extent of esterification was high at acid pH and also increased with heating. Protein solubility decreased, mainly at the highest temperature (60 °C). Increasing levels of fatty acid formed a complex with a slightly more soluble protein with less surface hydrophobicity. Esterified proteins exhibited aggregation/dissociation and were stabilized by different protein subunits belonging to 7S and 11S globulins. Denaturation of these soybean protein fractions (7S and 11S) were also detected in these complexes. The highest level of fatty acids favored formation of a more ordered protein structure.  相似文献   
76.
Modeling of industrial accidents with liquefied toxic and flammable gases is considered. Propagation of nonreacting heavy gas clouds over complex terrains is described by a two-dimensional model with averaging over the cloud height. A numerical simulation of a toxic accident initiated by the release of chlorine in the urban environment has been performed and the number of injured people has been computed. A two-dimensional axisymmetric model based on the Favre-averaged Navier-Stokes equations is used to model the fireballs occurring upon combustion of hydrocarbon fuel-air clouds. Zones of various thermal hazards for people have been obtained.  相似文献   
77.
78.
The Gas-cooled Fast Reactor is one of the reactor concepts selected by the Generation IV International Forum for the next generation of innovative nuclear energy systems. Several fuel design concepts are being investigated. Burnup depletion of mixed fuel of uranium and plutonium, cooled with gas in a fast neutron energy spectrum must be simulated. Various codes are being developed and/or adapted to improve the quality of the results, and also to reduce the computing time required for the simulations.  相似文献   
79.
We studied the molar ratio effects of niobium and potassium precursors on the structure and morphology of potassium niobate powders prepared via microwave-assisted hydrothermal synthesis (MaHS). KNbO3 nanostructures in the form of nanotowers and nanocubes were obtained at reduced synthesis times (30–240 min). The products were characterized via XRD, Raman spectroscopy, SEM, and TEM; band gap calculations used diffuse reflectance data. The results indicate that KNbO3 nanostructures were obtained with crystallite sizes ranging from 33 to 52 nm. An orthorhombic crystalline structure was formed from the increase of KOH at a molar ratio Nb2O5:KOH (1:8 to 1:16 M). The band-gap of 3.1–3.3 eV has potential use in photodegradation applications.  相似文献   
80.
Tools and methods developed during the era of quality and optimization have shown their limitations and become inappropriate in the context of the requirements of innovation. Nowadays the need to rebuild design practices in enterprises is strongly felt both in terms of human skills and methodological expertise. In part, a way to face the innovation era's difficulties has been provided through the theory of inventive problem solving. This theory represents a significant breakthrough in driving problem statement and solving in a direction that is expressed through the idea that technical systems are driven by objective laws. A second postulate concerns the notion of contradiction, but so far only few contributions have addressed the relations between laws and contradictions. This paper, through a qualitative approach, presents a solution to this limitation and proposes a possible use of laws within the choice of the appropriate conflicting pair, prior to the use of any TRIZ solving techniques. Tests to observe the impact of the proposed approach were conducted in a French engineering ‘grande école’ during three semesters with 180 engineers. The contribution of this paper is twofold. On the one hand, there is a theoretical contribution to the theory of inventive problem solving. In addition, the proposed method offers especially TRIZ practitioners new ways for problem understanding and problem formulation.  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