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   1524篇
  免费   49篇
电工技术   45篇
综合类   3篇
化学工业   312篇
金属工艺   26篇
机械仪表   38篇
建筑科学   25篇
矿业工程   1篇
能源动力   82篇
轻工业   75篇
水利工程   14篇
石油天然气   4篇
无线电   196篇
一般工业技术   343篇
冶金工业   142篇
原子能技术   12篇
自动化技术   255篇
  2024年   8篇
  2023年   27篇
  2022年   46篇
  2021年   57篇
  2020年   48篇
  2019年   48篇
  2018年   56篇
  2017年   68篇
  2016年   67篇
  2015年   37篇
  2014年   44篇
  2013年   122篇
  2012年   63篇
  2011年   91篇
  2010年   78篇
  2009年   71篇
  2008年   32篇
  2007年   45篇
  2006年   53篇
  2005年   46篇
  2004年   29篇
  2003年   29篇
  2002年   28篇
  2001年   15篇
  2000年   17篇
  1999年   18篇
  1998年   32篇
  1997年   28篇
  1996年   24篇
  1995年   14篇
  1994年   24篇
  1993年   18篇
  1992年   16篇
  1991年   14篇
  1990年   11篇
  1989年   10篇
  1988年   10篇
  1987年   13篇
  1986年   7篇
  1985年   8篇
  1984年   7篇
  1983年   7篇
  1982年   8篇
  1981年   8篇
  1980年   9篇
  1979年   9篇
  1977年   8篇
  1976年   13篇
  1971年   5篇
  1970年   5篇
排序方式: 共有1573条查询结果,搜索用时 12 毫秒
41.
A new necessary and sufficient condition for t-diagnosability of a system is proposed. It is shown that the new scheme is computationally more efficient than the existing one for checking the diagnosability of a system.  相似文献   
42.
The present study was carried out to fabricate the food grade vitamin E acetate nanoemulsion using edible mustard oil and to evaluate its improved bioactivities. A food-grade vitamin E acetate nanoemulsion was fabricated using the edible mustard oil and surfactant Tween-80. Flocculation was not observed for 15 days. The nanoemulsion was characterized for droplet morphology and size distribution using atomic force microscope and zetasizer, respectively. We observe a stable nanoemulsion of spherical morphology and a size distribution of 86.45 ± 3.61 nm. Further, the high-performance liquid chromatography method was used to determine the vitamin E acetate concentration and encapsulation efficiency for the stable nanoemulsion. These nanoemulsions showed improved bioactivity, antioxidant, and antimicrobial activity and could be potentially used to increase the shelf life of fruit juice.  相似文献   
43.
In recent decades, bioactive peptides have attracted increasing interest as health promoting functional foods. A variety of naturally formed bioactive peptides have been found in fermented dairy products such as yogurt, sour milk, and cheese. Initially these peptides are inactive within the sequence of the parent protein molecule and can be generated by gastrointestinal digestion of milk, fermentation of milk with proteolytic starter cultures, and/or hydrolysis by proteolytic enzymes. Milk derived peptides exert a number of health beneficial activities, even upon oral administration. Bioactive peptides have a great impact on major body systems including the digestive, nervous, endocrine, cardiovascular, diabetes type II, obesity, and immune systems. Antimicrobial peptides are also an important ingredient of innate immunity, especially at mucosal surfaces such as lungs and small intestine that are constantly exposed to a range of potential pathogens. Therefore, it plays an important role in boosting natural immune protection by reducing the risk of chronic diseases. Bioactive peptides are considered as potent drugs with well-defined pharmacological residues and also used to formulate health-enhancing nutraceuticals.  相似文献   
44.
In this paper, the relationship between the number of unit-cells used in the design of a frequency selective surface (FSS) and its expected directivity is established. The relationship between the number of FSS unit-cells and the directivity is based on the planer microstrip patch array antenna design concept where the unit-cell is treated as the superstrate illuminated by the source. To validate the proposed technique, the analytical value of the directivity has been compared with that of ray-tracing method. The directivity of antenna is calculated for two different planar array configurations at 600 GHz. The results of numerical analysis are compared to that of the full-wave electromagnetic simulator CST Microwave Studio and results are comparable. Further, the directivity computed by this proposed technique has also been compared with that of the reported in literatures.  相似文献   
45.
Microsystem Technologies - This paper reports the development of a novel electronic micro-viscometer capable of measuring viscosity of different Newtonian fluids using less than 100 µl which...  相似文献   
46.
Wireless Personal Communications - In this paper a combination of rectangular and elliptical fractal geometry is applied on a regular hexagonal wide slot antenna fabricated using a FR4 substrate to...  相似文献   
47.
Bio‐diesel has been accepted as a renewable liquid biofuel worldwide. In order to ensure customers' acceptance, standardisation and quality assurance are the key factors to the market introduction of bio‐diesel as a transport fuel. Lubricity of bio‐diesel is an important issue and it is well reported that 1–2% bio‐diesel is sufficient to maintain the lubricity of diesel even of very poor lubricity. However, a wide variation in lubricity performance of bio‐diesel from different vegetable oils and sources has been noticed. In addition, on critical examination, it was noticed that the variation in the lubricating performance of bio‐diesel could be better linked to its residual acidity than to variation in fatty acid composition. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
48.
Glass fiber-reinforced epoxy composites were prepared from the matrix resins tetraglycidyl diaminodiphenylmethane
  • 1 Systematic name: N,N,N′,N′-Tetrakis(2,3-epoxypropyl)-4,4′-diaminodiphenylmethane.
  • (TGDDM) and tetraglycidyl bis(o-toluidino)-methane
  • 2 Systematic name: N,N,N′,N′-Tetrakis(2,3-epoxypropyl)-4,4′-bis(o-toluidino)methane.
  • (TGMBT) using various amines like 4,4′-diaminodiphenylmethane (DDM), 4,4′-diaminodiphenylsulfone (DDS) and diethylene triamine (DETA) as curing agents. The fabricated laminates were evaluated for their mechanical and dielectrical properties and chemical resistance. The composites prepared using an epoxy fortifier (20 phr) showed significant improvement in the mechanical properties.  相似文献   
    49.
    This paper reports the result of studies on flocculation and dewatering of kaolin suspensions by cationic polyacrylamide (PAM-C) flocculants in presence of surfactants. The surfactants used were namely anionic sodium dodecyl sulphate (SDS), cationic cetyl trimethyl ammonium bromide (CTAB) and non-ionic TritonX 100, which is a polyoxyethylenic ether compound. The unflocculated kaolin has a very slow settling rate of about 0.03 cm/s and can be improved by more than ten times using PAM-C as a flocculating agent. PAM-C adsorbs on kaolin primarily through electrostatic attraction and the flocculation is governed mainly by charge neutralisation and bridging. Partial pre-coating of kaolin with all three surfactants leads to both physical adsorption as well as chemisorption at PAM-C. Pretreating the kaolin with surfactants can further increase or decrease settling rate depending on the type of surfactant used. However, the flocs thus formed shows better filtration and dewatering behaviour estimated in terms of reduction in specific resistance to filtration (SRF) and cake moisture. The minimum SRF occurs under conditions corresponding to far lower adsorption of PAM-C than that for best flocculation. Simultaneous addition of PAM-C and each of the three surfactants decreases settling rate and sediment volume markedly and does not reduce SRF any further but they all reduce cake moisture substantially. The reduction in cake moisture for different PAM-C: surfactant mixture is in the following order: PAM-C: SDS (1:1)>PAM-C: TX 100(1:1)>PAM-C: CTAB(1:1). Low cake moisture in comparison with PAM-C alone, may be a result of reduction in entrapment of excess water in the smaller flocs formed by simultaneous addition with surfactants and to some extent due to hydrophobicity caused by adsorption of surfactants.  相似文献   
    50.
    The mixed ester polyol (MEP) is obtained from refined soybean oil on treatment with glycerol at 210°C in presence of lithrage. The probable structure of MEP was established by IR spectra. The polyurethane synthesized from MEP and diphenyl methane diisocyanate (DPMDI) with varying NCO:OH ratios were reacted with cardanol-o-aminophenol dye using ethyleneglycol dimethacrylate (EGDM) as a cross-linking agent and benzoyl peroxide as initiator. The PU was thoroughly characterized by IR spectroscopy. The thermal behavior of the Interpenetrating polymer networks was characterized by TG and the Morphology was studied by XRD studies.  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