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   2435篇
  免费   24篇
电工技术   27篇
综合类   2篇
化学工业   158篇
金属工艺   19篇
机械仪表   21篇
建筑科学   8篇
矿业工程   1篇
能源动力   19篇
轻工业   68篇
水利工程   3篇
石油天然气   4篇
无线电   50篇
一般工业技术   74篇
冶金工业   1948篇
原子能技术   4篇
自动化技术   53篇
  2024年   3篇
  2022年   19篇
  2021年   23篇
  2020年   13篇
  2019年   22篇
  2018年   19篇
  2017年   9篇
  2016年   17篇
  2015年   12篇
  2014年   22篇
  2013年   18篇
  2012年   27篇
  2011年   20篇
  2010年   23篇
  2009年   27篇
  2008年   28篇
  2007年   28篇
  2006年   11篇
  2005年   12篇
  2004年   16篇
  2003年   17篇
  2002年   10篇
  2001年   14篇
  2000年   16篇
  1999年   68篇
  1998年   642篇
  1997年   356篇
  1996年   241篇
  1995年   108篇
  1994年   93篇
  1993年   121篇
  1992年   14篇
  1991年   36篇
  1990年   23篇
  1989年   27篇
  1988年   21篇
  1987年   26篇
  1986年   21篇
  1985年   27篇
  1983年   8篇
  1982年   5篇
  1981年   9篇
  1980年   19篇
  1979年   2篇
  1978年   6篇
  1977年   41篇
  1976年   98篇
  1975年   5篇
  1974年   4篇
  1973年   4篇
排序方式: 共有2459条查询结果,搜索用时 15 毫秒
1.
Alcohol-free beer with isotonic properties is getting more popular and its production can be carried out by different production strategies; however, interrupted fermentation is still a challenge. Therefore, the objective of this study was to develop a low-alcohol isotonic beer (<0.5% v/v) by interrupted fermentation. Moreover, the major objective is to compare the developed product to commercial beverages (sports drinks, ‘Pilsen' regular beer, alcohol-free beers and low-alcohol isotonic beer). The beverages were evaluated based on pH, alcohol content (% v/v), total titratable acidity (mEq L−1), osmolality (mOsmol kg−1), bitterness International Bitterness Units, colour European Brewery Convention, total phenolic compounds (mg L−1 gallic acid), reducing and total sugars (%) and Na and K contents (mg L−1). The developed low-alcohol isotonic beer presented characteristics similar to sports drinks, with the advantage of being richer in phenolic compounds and suitable osmolality. Despite salts were added in its formulation, the grades attributed to all beers employed in the sensory evaluation, as well as the purchase intention did not present significant differences.  相似文献   
2.
3.
In this work, we investigated a procedure which exploits microwave ovens to produce SiC- based components by reactive melt infiltration of silicon into graphite preforms. The employed oven is designed to grant optical access to the sample surface, which allows to measure its temperature evolution though a noncontact pyrometer. This signal was used as a feedback to control the power provided to the preform and as an experimental output whose analysis provides insight into the reaction mechanism. Specifically, it is found that complete infiltration is achieved much before the end of the reaction. The latter is not fully self-sustained as the global reaction rate continuously decreases with time until it is no more able to keep the temperature above the silicon solidification value. At that point, the reaction stops. The analysis of the processed samples proved that this procedure allows producing fully infiltrated samples without material failure by adjusting the heat provided during the infiltration stage rather than by tuning the preform structure and composition, which is the usual approach. The proposed method is less time and energy consuming than the standard one.  相似文献   
4.
Guest Editorial: Wireless Mobile Internet   总被引:1,自引:0,他引:1  
  相似文献   
5.
The factors contributing to the duration of a motor unit action potential (MUAP) are believed to be well known, with both manual measurements and computer simulations agreeing with respect to MUAP durations approaching 10 ms. In this investigation, it is clearly demonstrated that use of a wide-open amplifier bandpass combined with signal-to-noise ratio enhancement results in MUAP durations approaching 30 ms recorded with either a macro or single-fiber electrode. Why the clinically recorded MUAP duration differs significantly from these physiologic durations is discussed. A hypothesis is presented whereby the major contributing factor toward MUAP duration is the total time of action potential transmembrane current flow along the muscle fiber from end-plate zone to musculotendinous junction.  相似文献   
6.
7.
8.
This paper presents results of reliability investigation of 20 V N-Drift MOS transistor in 0.13 μm CMOS technology. Due to high performances required for CMOS applications, adding high voltage devices becomes a big challenge to guarantee the reliability criteria. In this context, new reliability approaches are needed. Safe Operating Area are defined for switch, Vds limited and Vgs limited applications in order to improve circuit designs. For Vds limited applications, deep doping dose effects in drift area are investigated in correlation to lifetime evaluations based on device parameter shifts under hot carrier stressing. To further determine the amount and locations of hot carriers injections, accurate 2D technological and electrical simulations are performed and permit to select the best compromise between performance and reliability for N-Drift MOS transistor.  相似文献   
9.
We have used a variety of methods to characterize the genome of the archaeon Methanosarcina thermophila TM-1. Pulsed-field gel analysis indicates a genome size of 2.8 Mb. We have constructed a bacterial artificial chromosome (BAC) library of M. thermophila and have used it to generate physical maps for this organism. The library is made up of 384 clones with an average insert size of 58 kb representing 8.0 genome equivalents. The utility of the library for low-resolution physical mapping was shown by identifying NotI linking clones and using these to order the NotI macrorestriction fragments of M. thermophila into a 2.8 Mb map. Hybridization of nine single copy genes and a 16S rRNA sequence to these macrorestriction fragments forms the basis for the first genetic map in this organism. High-resolution physical maps, consisting of overlapping clones, have been created using HindIII fingerprints of BAC clones. In this way, we identified a minimal path of five clones that span a 270 kb NotI fragment. The ease of manipulating BAC clones makes the BAC system an excellent choice for the construction of low-resolution and high-resolution physical and genetic maps of archaeal genomes. It also provides a substrate for future genome-sequencing efforts.  相似文献   
10.
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