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   4050篇
  免费   104篇
  国内免费   1篇
电工技术   16篇
综合类   3篇
化学工业   1614篇
金属工艺   55篇
机械仪表   60篇
建筑科学   96篇
矿业工程   6篇
能源动力   90篇
轻工业   719篇
水利工程   21篇
石油天然气   21篇
无线电   189篇
一般工业技术   625篇
冶金工业   164篇
原子能技术   15篇
自动化技术   461篇
  2024年   57篇
  2023年   94篇
  2022年   423篇
  2021年   367篇
  2020年   147篇
  2019年   146篇
  2018年   140篇
  2017年   151篇
  2016年   149篇
  2015年   112篇
  2014年   163篇
  2013年   225篇
  2012年   241篇
  2011年   253篇
  2010年   182篇
  2009年   198篇
  2008年   183篇
  2007年   156篇
  2006年   125篇
  2005年   102篇
  2004年   80篇
  2003年   70篇
  2002年   65篇
  2001年   37篇
  2000年   31篇
  1999年   35篇
  1998年   38篇
  1997年   31篇
  1996年   28篇
  1995年   25篇
  1994年   9篇
  1993年   13篇
  1992年   3篇
  1991年   7篇
  1989年   4篇
  1987年   4篇
  1986年   3篇
  1985年   5篇
  1984年   5篇
  1983年   5篇
  1982年   6篇
  1981年   4篇
  1980年   3篇
  1979年   6篇
  1977年   4篇
  1975年   3篇
  1974年   4篇
  1973年   2篇
  1971年   4篇
  1969年   2篇
排序方式: 共有4155条查询结果,搜索用时 31 毫秒
51.
Selenium (Se) has a well-known role in prevention of chronic diseases associated with oxidative stress and inflammation. The objective was to produce Se-enriched sauerkraut and to study the effect of selenite addition on indole glucosinolate hydrolysis products, vitamin C, Se biotransformation and microbial quality. The antioxidant activity of sauerkraut and its ability to inhibit NO production in LPS-induced macrophages were also examined. White cabbage was naturally fermented with 0.3 mg of Na2SeO3/kg fresh cabbage (NFSe) or without Se addition (NF). Total Se content reached up to 1.29 μg/g d.m. (0.11 μg/g f.m.). Selenomethylselenocysteine was the major Se form found in NFSe cabbage. Se addition caused a slight reduction of ascorbigen (6%) and vitamin C (5%) contents in sauerkraut (P ? 0.05); however, lactic acid bacteria increased (3%), and the formations of indole-3-carbinol and indole-3-acetonitrile were markedly enhanced (74% and 13%, respectively). NFSe cabbage extracts showed higher (P ? 0.05) antioxidant activity (163 μmol trolox/g d.m.) and inhibition of NO production in LPS-induced macrophages (IC50 = 44.0 μg/ml) than did NF cabbage extracts. Consequently, Se-enriched sauerkraut can be considered as a health-promoting food.  相似文献   
52.
In order to have a deeper insight into the retinol isomerization phenomenon, in this work different milk samples have been analysed for their content of trans retinol and its cis-isomers, by means of reliable HPLC techniques. Levels of the different isomers and the degree of retinol isomerization (13-cis/all-trans ratio, %) have been monitored during milk storage at different temperatures and after addition of specific microorganisms. In raw milk stored at 4 degrees C for 96 h the degree of retinol isomerization shifted from 1.1 to 2.3%, while in raw milk stored at 22 degrees C for 24 h it increased from 1.1 to 12.7%. Among microorganisms tested in pasteurized milk, the most active in causing an increment in the 13-cis/all-trans ratio (%), from 3.4 to 33.4% in 8 h, was Streptococcus thermophilus. The results obtained demonstrated a relationship between microbial evolution and retinol isomerization. Therefore, the determination of retinol isomers is of importance not only for a more precise evaluation of vitamin A activity but also for the evaluation of the microbiological quality of milk.  相似文献   
53.
Foods based on sweet lupin proteins are gaining attention from industry and consumers because of their possible role in the prevention of cardiovascular disease. When promoting lupin-based foods for inclusion in a daily diet, the thermal damage suffered during processing is of relevance to the bioactive and nutritional quality of the food product. N-(2-furoylmethyl)-L-lysine (furosine) quantification demonstrates that currently available sweet lupin protein isolates have a thermal damage comparable to or lower than other traditional food ingredients, and are a good source of lysine in non-dairy products. In lupin-based foods claiming to have cholesterol-lowering potential, shotgun proteomics offers itself as a fast and effective screening method for assessing the biological availability of active peptides. Such a method is readily applicable to other legume-enriched food products.  相似文献   
54.
55.
The effects of the addition of wild legumes (Lathyrus) from the South of Spain on the physical and nutritional properties of extruded products based on whole corn and brown rice were studied. Samples were obtained with a Brabender single screw extruder. The physical characterisation of the expanded products was performed by the measurement of density, expansion, solubility and specific mechanical energy consumption (SMEC). Chemical composition, amino acids content, protein digestibility, total polyphenol content and potential availability of iron and zinc were determined.  相似文献   
56.
57.
         下载免费PDF全文
This paper provides a first insight on tube configurations based on the hexagonal shape (hexagrid) for tall buildings. The idea is to investigate the mechanical properties of hexagrid to assess their applicability in tall buildings and to compare their potential efficiency to the more popular diagrid systems. For the above purposes, a general homogenization approach has been established for dealing with any structural patterns, and a methodology for characterizing the structural patterns from the mechanical point of view has been developed and specified for hexagrids and diagrids. Then on the basis of a simple stiffness criterion, a design procedure has been proposed and applied to a tall building case study, and several structural solutions (both hexagrids and diagrids) have been designed and assessed by varying the major geometrical parameters of the patterns. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
58.
    
What happens when you subvert the standardised repetition of the Modernist grid? In Building the Picture, a series of drawings that architect Elena Manferdini produced for an exhibition at the Art Institute of Chicago that ran during the spring and summer of 2015, visual effects and colour were applied to counteract Mies's highly uniform and modular mass-producible systems.  相似文献   
59.
The promotive effects of cerium oxide on commercial three-way catalysts (TWCs) for purification of motor exhaust gases have been widely investigated in recent years. This work shows the cooperative effects of CeO2–Pd on the kinetics of CO oxidation over Pd/CeO2–ZrO2. Under reducing-to-moderately oxidizing conditions, a zero-order O2 pressure dependence is found which can be interpreted on the basis of a mechanism involving a reaction between CO adsorbed on Pd and surface oxygen from the support. The high oxygen-exchange capability of the CeO2–ZrO2 support, as determined from temperature-programmed reduction/oxygen uptake measurements is suggested as being responsible for such a catalytic behavior.  相似文献   
60.
Photochemically induced grafting and graft-polymerization of 4-(N-ethyl-N-2-acryloxyethyl)amino-4′-nitro-azobenzene I , brought into contact in the solid state with cellulose by evaporation of solvent from monomer solutions, has been investigated kinetically at 30°C. Two constant rate periods were observed. The first one was interpreted on the basis of a self-sensitized grafting mechanism of monomeric or oligomeric species of I , photochemically initiated by hydrogen abstraction from the cellulose surface. The second one was explained as a self-sensitized photochemically induced graft-polymerization of I on the first grafted layer. Some particular features, such as concurrent photodegradation of the first grafted layer at low surface coverage, are discussed in the light of the proposed mechanism.  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