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   589篇
  免费   57篇
电工技术   10篇
化学工业   137篇
金属工艺   14篇
机械仪表   8篇
建筑科学   17篇
能源动力   31篇
轻工业   48篇
水利工程   10篇
无线电   46篇
一般工业技术   159篇
冶金工业   25篇
原子能技术   10篇
自动化技术   131篇
  2024年   1篇
  2023年   13篇
  2022年   15篇
  2021年   32篇
  2020年   22篇
  2019年   18篇
  2018年   24篇
  2017年   30篇
  2016年   31篇
  2015年   25篇
  2014年   30篇
  2013年   62篇
  2012年   38篇
  2011年   71篇
  2010年   35篇
  2009年   45篇
  2008年   44篇
  2007年   28篇
  2006年   24篇
  2005年   18篇
  2004年   11篇
  2003年   5篇
  2002年   5篇
  2000年   2篇
  1998年   2篇
  1997年   2篇
  1995年   1篇
  1994年   1篇
  1993年   3篇
  1992年   2篇
  1991年   3篇
  1983年   1篇
  1981年   1篇
  1977年   1篇
排序方式: 共有646条查询结果,搜索用时 15 毫秒
21.
The main objective of the present project was the purification of brown flaxseed meal from coloring pigments in order to improve its potential use as ingredient in food formulations. Thus, this work was aimed to study the bleaching of non-defatted brown flaxseed meal in dilute hydrogen peroxide solutions. Bleaching was evaluated according to the Hunter L, (a), and (b) color scale as function of the hydrogen peroxide concentration (1%, 2%, and 3% v/v), the meal concentration (2.5%, 5%, and 10% w/w), the bleaching time (10, 20, and 30?min), and the pH (3, 7, and 9). Effect of all the independent variables was significant. The L value was the most significantly affected parameter and increased as the concentration of hydrogen peroxide increased, but decreased as the concentration of flaxseed meal increased. The L value was observed to be higher at pH?9 than at pH?3 and 7. The b value, which represents the yellowness, was significantly increased from 18.70?±?0.01 (control sample) to 35.45?±?0.04 after the meal was treated with a 3% hydrogen peroxide solution at pH?9. Total phenolics content significantly decreased when the meal was treated with 3% (v/v) hydrogen peroxide solution. This concentration yielded the higher L color value (highly bleached meal).  相似文献   
22.
23.
Benchmarking is comparing the output of different systems for a given set of input data in order to improve the system’s performance. Faced with the lack of realistic and operational benchmarks that can be used for testing optimization methods and control systems in flexible systems, this paper proposes a benchmark system based on a real production cell. A three-step method is presented: data preparation, experimentation, and reporting. This benchmark allows the evaluation of static optimization performances using traditional operation research tools and the evaluation of control system's robustness faced with unexpected events.  相似文献   
24.
25.
26.
The final geometry of 3D warp interlock fabric needs to be check during the 3D forming step to ensure the right locations of warp and weft yarns inside the final structure. Thus, a new monitoring approach has been proposed based on sensor yarns located in the fabric thickness. To ensure the accuracy of measurements, the observation of the surface deformation of the 3D warp interlock fabric has been joined to the sensor yarns measurements. At the end, it has been revealed a good correlation between strain measurement done globally by camera and locally performed by sensor yarns. Additionally, sensor yarns located in the two directions of the 3D warp interlock fabric have revealed a different forming behaviour depending on the architecture and the different slope values of the punch.  相似文献   
27.
Geraniol produced by grape is the main precursor of terpenols which play a key role in the floral aroma of white wines. We investigated the fate of geraniol during wine fermentation by Saccharomyces cerevisiae. The volatile compounds produced during fermentation of a medium enriched with geraniol were extracted by Stir-bar sorptive extraction and analysed by GC–MS. We were able to detect and quantify geranyl acetate but also citronellyl- and neryl-acetate. The presence of these compounds partly explains the disparition of geraniol. The amounts of terpenyl esters are strain dependant. We demonstrated both by gene overexpression and gene-deletion the involvement of ATF1 enzyme but not ATF2 in the acetylation of terpenols. The affinity of ATF1 enzyme for several terpenols and for isoamyl alcohol was compared. We also demonstrated that OYE2 is the enzyme involved in geraniol to citronellol reduction. Fermenting strain deleted from OYE2 gene produces far less citronellol than wild type strain. Moreover lab strain over-expressing OYE2 allows 87% geraniol to citronellol reduction in bioconversion experiment compared to about 50% conversion with control strain.  相似文献   
28.
New solution processable organic semiconductors, consisting of pyrromelitic, naphthalene or perylene bisimide core and triarylamine N-substituents, have been synthesized. All three compounds are electrochemically active and undergo quasi-reversible oxidation and reduction as evidenced by cyclic voltammetry investigations. The oxidation process involves the transformation of the triarylamine substituents into radical cations as proven spectroscopically and spectroelectrochemically. The reduction process occurs at the arylene bisimide core leading to the formation of a radical anion and eventually a dianion in the second step. These findings are in perfect agreement with the DFT calculations which show that in the synthesized molecules the HOMO orbital is located on the triarylamine moiety whereas the LUMO one on the bisimide core. In all molecules studied the electrochemically determined ionization potential (IP) is slightly higher than 5.0 eV whereas in naphthalene and perylene derivatives the electron affinity (EA) is close to ?3.9 eV. These values fulfill the requirements for n-type (electron) semiconductors in air operating n-channel field effect transistors (FETs) as well as for p-type (hole) conductors in p-channel FETs. To verify whether the newly synthesized compounds exhibit the expected electrical transport properties all organic (CYTOP dielectric) test transistors were fabricated. All three semiconductors showed no field effect in the n-channel configuration. To the contrary, they could be used in p-channel FETs showing, in the saturation regime, the hole mobility approaching 10?4 cm2 V?1 s?1 – the value which slightly exceeds that measured for low molecular weight, amorphous triarylamine semiconductors.  相似文献   
29.
Magnetosome biomineralization and chain formation in magnetotactic bacteria are two processes that are highly controlled at the cellular level in order to form cellular magnetic dipoles. However, even if the magnetosome chains are well characterized, controversial results about the microstructure of magnetosomes were obtained and its possible influence in the formation of the magnetic dipole is to be specified. For the first time, the microstructure of intracellular magnetosomes was investigated using high-resolution synchrotron X-ray diffraction. Significant differences in the lattice parameter were found between intracellular magnetosomes from cultured magnetotactic bacteria and isolated ones. Through comparison with abiotic control materials of similar size, we show that this difference can be associated with different oxidation states and that the biogenic nanomagnetite is stoichiometric, i.e. structurally pure whereas isolated magnetosomes are slightly oxidized. The hierarchical structuring of the magnetosome chain thus starts with the formation of structurally pure magnetite nanoparticles that in turn might influence the magnetic property of the magnetosome chains.  相似文献   
30.
In packaging science, the study of transport is important in determining the viability of a package/product pair. Many load breaks occur (e.g. handling and storage) along a supply chain. Transport also generates various physical stresses (e.g. shocks, shakes and vibrations). These physical phenomena can be recorded using a variety of customized sensors (e.g. tri‐axial accelerometers, temperature sensors and pressure sensors). This study focuses on a transport phase that has not been studied in depth to date. Transportation operations on tarmacs include many handling and transportation machines, which are characterized by typical constraints that are often more stringent than airlift phase constraints. For comparison, acceleration distributions were estimated and analysed for the tarmac phase and road phase. Severity indicators were calculated based on existing methods. The second part of this study addresses the study of shakes. The shake distributions at 90 and 95% were another indicator of the shakes' severity and probability of occurrence. These elements allow us to characterize the impact of the tarmac area during air transport.  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