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   617篇
  免费   42篇
电工技术   25篇
化学工业   105篇
金属工艺   17篇
机械仪表   17篇
建筑科学   34篇
能源动力   13篇
轻工业   88篇
水利工程   2篇
石油天然气   1篇
无线电   136篇
一般工业技术   98篇
冶金工业   71篇
原子能技术   4篇
自动化技术   48篇
  2024年   1篇
  2023年   9篇
  2022年   12篇
  2021年   9篇
  2020年   17篇
  2019年   11篇
  2018年   14篇
  2017年   19篇
  2016年   16篇
  2015年   22篇
  2014年   32篇
  2013年   34篇
  2012年   37篇
  2011年   38篇
  2010年   26篇
  2009年   30篇
  2008年   37篇
  2007年   25篇
  2006年   23篇
  2005年   21篇
  2004年   27篇
  2003年   25篇
  2002年   18篇
  2001年   12篇
  2000年   18篇
  1999年   20篇
  1998年   29篇
  1997年   20篇
  1996年   5篇
  1995年   7篇
  1994年   7篇
  1993年   5篇
  1992年   6篇
  1991年   2篇
  1990年   1篇
  1989年   4篇
  1988年   4篇
  1987年   3篇
  1985年   1篇
  1983年   1篇
  1981年   1篇
  1979年   2篇
  1978年   1篇
  1977年   2篇
  1976年   3篇
  1969年   1篇
  1968年   1篇
排序方式: 共有659条查询结果,搜索用时 52 毫秒
21.
Healthcare facilities are often complex and overwhelming for visitors, and wayfinding in healthcare facilities can be challenging. As there is an increasing number of global citizens who travel to seek medical care in another country, it is critical to make wayfinding easy for visitors who are not familiar with the language in a foreign country. Among many wayfinding aids, symbols are helpful for those visitors who have limited ability to understand written language. This study tested universal healthcare symbols in the United States, South Korea, and Turkey to compare the comprehension of symbols cross-country and identify predictors of the correct comprehension. To explore statistically significant relationships between symbol comprehension and countries, Pearson's Chi-square tests, logistic regression, and ANOVA were conducted. The test results showed that ten symbols among 14 tested have significant relationship with countries. Results of this study demonstrate that symbol comprehension can be varied significantly in different countries.  相似文献   
22.
Food Science and Biotechnology - Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is mainly transmitted through respiratory droplets....  相似文献   
23.
An antimicrobial peptide produced by Bacillus subtilis KU25, KU43, and KU44 was isolated from traditional Korean fermented foods and characterized. It was named as subtilin KU25, KU43, and KU44. Subtilin KU25, KU43, and KU44 were sensitive against α-chymotrypsin, protease XIII, and various proteinase enzymes, respectively. B. subtilis KU43 was selected as the producer with the broadest antimicrobial spectrum. Subtilin KU43 was stable at a pH range of 3 to 9 for 4 h, and withstood exposure to temperatures of 50–90°C for 30 min. The mode of inhibition against Listeria monocytogenes ATCC 15313 involved a bactericidal effect by a reduction in the cell numbers and breakage of the indicator cell membranes. The molecular mass of subtilin KU43 was measured at approximately 3.5 kDa. These results demonstrate the development of novel strains from traditional Korean fermented foods, and illustrate the possibility that some of these strains might generate a natural preservative compound.  相似文献   
24.
Li0.33La0.55TiO3 solid electrolytes with a pure phase were synthesized by the citric acid-supported sol-gel method and then sintered under controlled redox atmospheres of air, argon and hydrogen. Although of similar morphology and relative density, Li0.33La0.55TiO3 samples sintered under reduction atmosphere such as argon and hydrogen exhibited a tetragonal structure with lattice distortion. The distortion and volume expansion of the crystal lattice was identified as originating from the transformation of the Ti valence state, and this was more clearly observed under sintering of the hydrogen atmosphere. The qualitative analysis of the Ti valence state using an X-ray Photoelectron Spectroscopy experiment was performed and indicated that the largest amount of Ti3+(18.6%) was formed in the Li0.33La0.55TiO3 samples sintered under hydrogen atmosphere. The relationship between the lattice distortion and the lithium ion conductivity of the Li0.33La0.55TiO3 sintered under different atmospheres is also discussed on the basis of the lattice distortion.  相似文献   
25.
Food Science and Biotechnology - The purpose of this study was to evaluate the anti-inflammatory and anti-genotoxic activity of branched-chain amino acids (BCAAs) in lipopolysaccharide (LPS)...  相似文献   
26.
Thermoelastic characteristics of thermal barrier coatings (TBCs) with vertical cracks were analyzed through mathematical approaches to investigate the thermoelastic behaviors of TBCs in a service temperature. TriplexPro?-200 system was applied to prepare the relatively dense TBC using METECO 204NS powder. The microstructure of top coat in the TBC was just controlled to create vertical type cracks by reheating without powder feeding in same equipment and rapid cooling process. A couple of governing partial differential equations were derived based on the thermoelastic theory, and a finite volume model was developed to the governing equations to evaluate the thermoelastic characteristics, such as temperature distribution profile, displacement, and stress, inducing a thermal fatigue. For the specimen with two or more vertical type cracks, smaller displacement appears to longitudinal direction and larger displacement to radial direction as the number of crack increases. In the longitudinal stress distribution profiles to z-direction, the tensile stress at the interface between the bond coat and the substrate converts into the compressive stress when the specimen has vertical cracks more than two, while larger magnitude undulation develops for the specimen with smaller number of crack in the radial stress distribution profiles. The results obtained demonstrate that multiple vertical cracks enhance the thermal durability and extend the lifetime of TBCs.  相似文献   
27.
Journal of Mechanical Science and Technology - The main objective of the present study is to design a bubble collecting section for use in ventilated supercavitation experiments. The large amounts...  相似文献   
28.
Based on the integrated consideration and engineering of both conjugated backbones and flexible side chains, solution‐processable polymeric semiconductors consisting of a diketopyrrolopyrrole (DPP) backbone and a finely modulated branching side chain (ε‐branched chain) are reported. The subtle change in the branching point from the backbone alters the π?π stacking and the lamellar distances between polymer backbones, which has a significant influence on the charge‐transport properties and in turn the performances of field‐effect transistors (FETs). In addition to their excellent electron mobilities (up to 2.25 cm2 V?1 s?1), ultra‐high hole mobilities (up to 12.25 cm2 V?1 s?1) with an on/off ratio (Ion/Ioff) of at least 106 are achieved in the FETs fabricated using the polymers. The developed polymers exhibit extraordinarily high electrical performance with both hole and electron mobilities superior to that of unipolar amorphous silicon.  相似文献   
29.
Electronics that are capable of destroying themselves, on demand and in a harmless way, might provide the ultimate form of data security. This paper presents materials and device architectures for triggered destruction of conventional microelectronic systems by means of microfluidic chemical etching of the constituent materials, including silicon, silicon dioxide, and metals (e.g., aluminum). Demonstrations in an array of home‐built metal‐oxide‐semiconductor field‐effect transistors that exploit ultrathin sheets of monocrystalline silicon and in radio‐frequency identification devices illustrate the utility of the approaches.  相似文献   
30.
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