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   260篇
  免费   7篇
电工技术   2篇
综合类   1篇
化学工业   86篇
金属工艺   3篇
机械仪表   3篇
建筑科学   4篇
能源动力   2篇
轻工业   21篇
水利工程   2篇
石油天然气   2篇
无线电   20篇
一般工业技术   53篇
冶金工业   47篇
自动化技术   21篇
  2023年   4篇
  2022年   23篇
  2021年   22篇
  2020年   6篇
  2019年   3篇
  2018年   3篇
  2017年   5篇
  2016年   9篇
  2015年   12篇
  2014年   10篇
  2013年   16篇
  2012年   16篇
  2011年   19篇
  2010年   5篇
  2009年   7篇
  2008年   12篇
  2007年   5篇
  2006年   4篇
  2005年   11篇
  2004年   6篇
  2003年   5篇
  2002年   6篇
  2001年   5篇
  2000年   3篇
  1999年   2篇
  1998年   8篇
  1997年   9篇
  1996年   8篇
  1995年   5篇
  1994年   3篇
  1993年   1篇
  1991年   1篇
  1990年   2篇
  1988年   1篇
  1986年   2篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
  1976年   2篇
  1975年   1篇
  1934年   1篇
排序方式: 共有267条查询结果,搜索用时 15 毫秒
31.
The kink effect in InAlAs/InGaAs/InP composite channel heterojunction field effect transistors (HFETs) was investigated as a function of temperature and optical excitation. Drain source and gate current measurements show that above 325 K the kink effect disappears while the impact ionization process is still present. The kink at low temperatures is suppressed by illumination with photons of energy above 1 eV. These results prove that this parasitic effect is mainly related to the presence of traps in the top layers  相似文献   
32.
When dilemmas require trade-offs between profits and ethics, do leaders high in social dominance orientation (SDO) and followers high in right-wing authoritarianism (RWA) make decisions that are more unethical than those made by others? This issue was explored in 4 studies with female participants performing managerial role-playing tasks. First, dyads comprising a person who was either low or high in SDO and a person who was either low or high in RWA negotiated for a leadership position. People high in SDO were more likely to obtain leader positions than to obtain follower positions. No other effects were significant. Second, leaders high in SDO partnered with an agreeable (confederate) follower made decisions that were more unethical than those of leaders low in SDO. Third, followers high in RWA were more acquiescent to and supportive of an unethical (confederate) leader than were followers low in RWA. Fourth, high SDO leader-high RWA follower dyads made decisions that were more unethical than those made in role-reversed dyads because leaders had more influence. Implications of these results for conceptualizing SDO, RWA, and authoritarian dynamics are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
33.
Complete oxidation of benzene on Co---Cr and Co---Cr oxide catalysts   总被引:1,自引:0,他引:1  
Supported mixture metal oxide systems, Cu---Cr and Co---Cr on γ-A12O3 and γ-A12O3+ SiO2 were prepared and studied. They exhibited catalytic activity in the complete oxidation of benzene.  相似文献   
34.
Medium chain 2-hydroxy fatty acids and 3-hydroxy fatty acids (2-OH-FAs and 3-OH-FAs with 8–20 carbons) are widespread in nature but little was known about the quantities of these minor fatty acids in food. For this reason, the concentrations and composition of 2- and 3-OH-FAs in several foodstuffs (milk and dairy products, animal brains, suet, vegetable oils) and two non-food samples (wool wax and vernix caseosa) were determined by gas chromatography with electron-capture negative ion mass spectrometry in the selected ion monitoring mode. Lipids were isolated from samples by accelerated solvent extraction. After transesterification the obtained fatty acid methyl esters (FAMEs) were separated into OH-FAMEs and non-OH-FAMEs. The OH-FAMEs were converted into pentafluorobenzoyl (PFBO) derivatives (PFBO-O-FAMEs). 2- and 3-OH-FAs were detected in all samples analysed. Chain-length ranged from 8–20 carbons. In general, 3-OH-FAs dominated in milk and dairy products (maximum concentration 17.7 mg/100 g l.w. in goat milk) whereas 2-OH-FAs were more abundant in animal brains and suet. The lowest concentrations were determined in vegetable oils (0.21–2.42 mg/100 g l.w.) whereas the highest concentrations of 2-OH-FAs were determined in wool wax (1180 mg/100 g l.w.) and vernix caseosa (34.5 mg/100 g l.w.).  相似文献   
35.
D. Dubina  M. Georgescu 《Thin》1994,20(1-4):189-201
The present paper continues to compare and analyse the most recent design codes formulae for interactive buckling of thin-walled members. A first analysis was performed using a statistical comparison between theoretical and experimental results and was presented at the SSRC Annual Technical Session, held in Pittsburgh. An analytic comparison between ECCS 1987, EUROCODE 3, AISI and the author's formula is performed. A proposal for a cross-sections classification from the point of view of an ‘erosion factor’ is also presented.  相似文献   
36.
The distribution equilibrium data at 25°C for the extraction of copper from aqueous solutions, containing sodium nitrate or sodium sulphate, by carboxylic acids using toluene, benzene and carbon tetrachloride as diluents have been measured. The carboxylic acids used are n-myristic, n-lauric and n-capric. The results obtained led to the conclusion that the composition of the extracted species corresponds to (CuR2.HR)2, being irrespective of both the nature of organic phase and the aqueous phase. The addition of sodium sulphate, instead of sodium nitrate, decreases the extraction efficiency due to the formation a CuSO4 ion-pair into the aqueous phase. The diluent effect has been related to the activity of the dimerised carboxylic acid in the diluent.  相似文献   
37.
Thyroid cancers     
We have analysed factors that influenced on the patient survival in 195 cases of thyroid cancer. The survival is essentially influenced by the histology, the papillary forms (survival after 15 years: 83.1-93%) and follicular cancers (survival after 15 years: 84-94%) having an excellent evolution. The non-differentiated and mixed cancers have a very severe prognosis that is independent of the complex therapy that have been used (survival after 5 years: 17.1% in non-differentiated forms and 32.5% in mixed ones). The prognosis is better in subjects under the age of 45 and in female subjects. The cancers in the 1-st and 2-nd stage of tumor extension have a better evolution that those in the 3-rd stage. In differentiated cancers, the total or subtotal thyroidectomy followed by radioiodine administration determine the best survival.  相似文献   
38.
39.
In this study, Enterocin 416K1, a bacteriocin produced by Enterococcus casseliflavus IM 416K1, was entrapped in an organic-inorganic hybrid coating applied to a LDPE (low-density polyethylene) film for its potential use in the active food packaging field. The antibacterial activity of the coated film was evaluated against Listeria monocytogenes NCTC 10888 by qualitative modified agar diffusion assay, quantitative determination in listeria saline solution suspension and direct contact with artificially contaminated food samples (frankfurters and fresh cheeses) stored at room and refrigeration temperatures. All investigations demonstrated that enterocin-activated coatings have a good anti-listeria activity. Qualitative tests showed a clear zone of inhibition in the indicator lawn in contact with and around the coated film. During the quantitative antibacterial evaluation the L. monocytogenes viable counts decreased to 1.5 log units compared to the control. The inhibitory capability was confirmed also in food-contact assays. In all food samples packed with coated films we observed a significant decrease in L. monocytogenes viable counts in the first 24 h compared to the control. This difference was generally maintained up to the seventh day and then decreased, with the exception of the cheese samples stored at refrigeration temperature.  相似文献   
40.
Wireless Networks - As mobile devices have become more affordable, easy to use and powerful, the number of mobile users and their bandwidth demands have experienced a significant growth....  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