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   225959篇
  免费   3862篇
  国内免费   720篇
电工技术   3823篇
综合类   376篇
化学工业   33861篇
金属工艺   8654篇
机械仪表   6635篇
建筑科学   5733篇
矿业工程   1392篇
能源动力   6006篇
轻工业   20826篇
水利工程   2517篇
石油天然气   4189篇
武器工业   14篇
无线电   25072篇
一般工业技术   43812篇
冶金工业   42951篇
原子能技术   5294篇
自动化技术   19386篇
  2021年   2364篇
  2020年   1677篇
  2019年   2155篇
  2018年   3236篇
  2017年   3403篇
  2016年   3477篇
  2015年   2330篇
  2014年   3896篇
  2013年   10288篇
  2012年   6253篇
  2011年   8531篇
  2010年   6685篇
  2009年   7498篇
  2008年   7482篇
  2007年   7394篇
  2006年   6301篇
  2005年   6008篇
  2004年   5844篇
  2003年   5655篇
  2002年   5268篇
  2001年   5295篇
  2000年   5066篇
  1999年   5204篇
  1998年   13205篇
  1997年   9314篇
  1996年   7249篇
  1995年   5231篇
  1994年   4711篇
  1993年   4549篇
  1992年   3418篇
  1991年   3333篇
  1990年   3079篇
  1989年   3130篇
  1988年   3014篇
  1987年   2543篇
  1986年   2464篇
  1985年   2890篇
  1984年   2622篇
  1983年   2426篇
  1982年   2197篇
  1981年   2309篇
  1980年   2138篇
  1979年   2202篇
  1978年   2191篇
  1977年   2497篇
  1976年   3400篇
  1975年   1910篇
  1974年   1801篇
  1973年   1819篇
  1972年   1473篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Russian Engineering Research - The theoretically possible reconfigurable parallel mechanisms are classified, in terms of the layout of guides on the base. Formulas are derived for the...  相似文献   
103.
104.
105.
Lameness is one of the most prevalent diseases affecting the welfare of cows in modern dairy production. Lameness leads to behavioral changes in severely lame cows, which have been investigated in much detail. For early detection of lameness, knowledge of the effects of moderate lameness on cow behavior is crucial. Therefore, the behavior of nonlame and moderately lame cows was compared on 17 Swiss dairy farms. On each farm, 5 to 11 nonlame (locomotion score 1 of 5) and 2 to 7 moderately lame (locomotion score 3 of 5) cows were selected for data collection in two 48-h periods (A, B) separated by an interval of 6 to 10 wk. Based on visual locomotion scoring, 142 nonlame and 66 moderately lame cows were examined in period A and 128 nonlame and 53 moderately lame cows in period B. Between these 2 periods, the cows underwent corrective hoof trimming. Lying behavior, locomotor activity, and neck activity were recorded by accelerometers (MSR145 data logger, MSR Electronics GmbH, Seuzach, Switzerland), and feeding and rumination behaviors by noseband sensors (RumiWatch halter, ITIN + HOCH GmbH, Liestal, Switzerland). Furthermore, visits to the brush and the concentrate feeder, and the milking order position were recorded. In comparison with nonlame cows, moderately lame cows had a longer lying duration, a longer average lying bout duration, and a greater lateral asymmetry in lying duration. Average locomotor activity, locomotor activity during 1 h after feed delivery or push-ups, and average neck activity were lower in moderately lame cows. Eating time and the number of eating chews (jaw movements) were reduced in moderately lame compared with nonlame cows, whereas no effect of moderate lameness was evident for ruminating time, number of ruminating chews and boluses, and average number of ruminating chews per bolus. Moderately lame cows visited the concentrate feeder and the brush less frequently, and they were further back in the milking order compared with nonlame cows. In conclusion, nonlame and moderately lame cows differed in a biologically relevant way in many of the behavioral variables investigated in this study. Therefore, the use of these behavioral changes seems to be promising to develop a tool for early lameness detection.  相似文献   
106.
107.
Personal and Ubiquitous Computing - This article presents a study concerning the evaluation of a smart home control system for elderly people with a sample of 10 users in a city in the interior of...  相似文献   
108.
109.
An experimental methodology for inferring brine dissolution rate in monoethylene glycol (MEG) solutions at different temperatures using a webcam combined with a mathematical model is presented. The measurement system is designed to track the RGB (red, green, and blue) colour variations during the dissolution process. A dynamic model augmented with the population balance equation is applied to describe the dissolution process. Moreover, the dissolution rate is consistently related to the temperature and MEG concentration through the driving force based on the Gibbs energy and chemical affinity. The applied low-cost measurement apparatus proved to be a useful resource for tracking the dissolution dynamics in a wide range of undersaturation.  相似文献   
110.
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