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   480篇
  免费   12篇
  国内免费   4篇
电工技术   8篇
化学工业   66篇
金属工艺   16篇
机械仪表   9篇
建筑科学   14篇
能源动力   6篇
轻工业   58篇
水利工程   6篇
石油天然气   1篇
无线电   35篇
一般工业技术   69篇
冶金工业   117篇
原子能技术   3篇
自动化技术   88篇
  2022年   7篇
  2021年   8篇
  2020年   13篇
  2019年   9篇
  2018年   14篇
  2017年   7篇
  2016年   15篇
  2015年   8篇
  2014年   18篇
  2013年   25篇
  2012年   31篇
  2011年   54篇
  2010年   31篇
  2009年   29篇
  2008年   18篇
  2007年   33篇
  2006年   16篇
  2005年   22篇
  2004年   19篇
  2003年   13篇
  2002年   16篇
  2001年   11篇
  2000年   8篇
  1999年   5篇
  1998年   10篇
  1997年   6篇
  1996年   8篇
  1995年   5篇
  1994年   3篇
  1993年   5篇
  1992年   4篇
  1991年   4篇
  1990年   5篇
  1989年   4篇
  1988年   3篇
  1987年   2篇
  1986年   3篇
  1984年   2篇
  1981年   1篇
  1979年   1篇
排序方式: 共有496条查询结果,搜索用时 640 毫秒
71.
As power costs continue to rise, the world's exisiting motor population will become more and more obsolete. Today's astute textile manufacturing companies wiUl recognize this fact and seek ways of upgrading their machines. Two major alternatives available to these companies are reviewed: replacing motors before they fail, known as retrofitting, and replacing rather than rewinding motors as they fail with high-efficiency motors. Issues related to the alternatives discussed are 1) economics of motor replacement, 2) development of equipment list and data, 3) operating efficiency of existing motors, 4) impact of rewinding on efficiency, 5) verification of efficiency assumptions via on-site testing, 6) determination of changeout labor cost, 7) salvage value of exisiting motors, 8) downtime and its effect on replacement programs, 9) reliabilty enhancement, and 10) warranty implications.  相似文献   
72.
Stable isotope analysis is an established method for detecting honey adulteration. We extend its application to include honey and honeycomb region-of-origin assignment using hydrogen (δ2H) and oxygen (δ18O) isotopes. We observed that liquid honey δ2H and δ18O values had the potential to change because of water absorption and H atom exchange between sugars and water vapour. This suggested that liquid honey has limited use for geo-location, because specimens will record analysis location humidity. Paired liquid honey and honeycomb δ2H values were significantly correlated; therefore, we propose using wax δ2H values for region-of-origin assignment. We observed significant correlations between beeswax δ2H values and both mean annual precipitation and tap water δ2H values predicted for hive locations, suggesting that geographical variation in water δ2H values are recorded by beeswax δ2H values. This survey demonstrates the promise of stable isotopes for region-of-origin assignment, using honeycomb wax δ2H values, which complements carbon isotope analysis to detect adulteration.  相似文献   
73.
The aim of this study was to determine the effects of tumbling at different post-mortem times on the proteolytic features and quality attributes of beef loins (M. longissimus lumborum). Loins (n = 12) were cut into 4 sections and assigned to tumbling at 1, 6 or 11 days post-mortem or non-tumbled control. Upon tumbling, additional ageing was applied to a common post-mortem time of 16 days. In general, tumbling had no considerable impacts on water-holding ability of samples. Tumbling resulted in an immediate decrease in shear force values (WBSF) of beef samples. Tumbling at 1 day post-mortem with no ageing had similar WBSF compared to the non-tumbled controls at 16 days (P > 0.05). With ageing, tumbling increased amounts of protein degradation, myofibrillar fragmentation and calpain-1 autolysis of samples. These results suggest that early post-mortem tumbling coupled with ageing can synergistically impact the tenderness development of beef loins and shorten the necessary ageing period.  相似文献   
74.
75.
76.
The St. Clair-Detroit River System contains a world-class Great Lakes muskellunge (Esox masquinongy) fishery that has avoided the declines observed in many Great Lakes muskellunge populations. Muskellunge are an upper trophic level predator, and therefore a naturally low-density species. Limited fishery-independent data exist on which to base management decisions. To remedy this, we initiated an acoustic telemetry study in May of 2016, in collaboration with the Great Lakes Acoustic Telemetry Observation System. Our objective was to describe patterns of movement of muskellunge in this large and open system to better understand their spatial ecology. We acoustically tagged 133 muskellunge in the Detroit River and Lake St. Clair, and movements of 58 fish that passed our data quality control screens were analyzed. We utilized mixed modelling to assess the effects of sex, length, release location, and season on daily movement rates. We found that movement rates only differed among seasons, with highest movement rates occurring in the fall and lowest movement rates in the winter. Muskellunge tagged at different locations exhibited distinct residency patterns, and fish frequently crossed jurisdictional and waterbody boundaries. Ultimately our study highlights the scope and patterns of muskellunge movement in a large, unimpounded system and demonstrates that management of these fish would benefit from consideration of their full distribution covering multiple management jurisdictions.  相似文献   
77.
In recent years, much attention has been paid to the consumption of meat and processed meat, and their relationship with a healthy diet. This review provides an overview of the potential strategies, which can be used to provide the implications for producing healthy, wholesome and consistently high-quality meat products. Genetic selection, nutrition and feeding management, and gene manipulation techniques have been used as the main strategies to induce beneficial changes in meat and meat composition. Besides, the incorporation of ingredients that play a technological role and are potentially health-enhancing, such as fibre, fat substitutes, natural antioxidants and the reduction of sodium and nitrites, has a high potential in the development of healthier meat products. In this review, we have observed that many strategies have been successfully used to obtain products with low fat, reduced sodium and nitrite content, low cholesterol and absence of synthetic antioxidants. Another point to be highlighted is that some of these strategies also allow obtaining products with positive health effects that can be potential alternatives to improve consumer acceptance.  相似文献   
78.
The paper presents an improved context-based denoising method for gray scale images affected by impulse noise. The proposed algorithm is using Markov chains to replace the detected noise with the intensity having the highest number of occurrences in similar contexts. The context of a noisy pixel consists in its neighbor pixels and is searched in a larger but limited surrounding area. We have analyzed different search methods and different context shapes. The experimental results obtained on the test images have shown that the most efficient model applies the search in form of   “*”  of contexts in form of   “+”. Besides the better denoising performance obtained on all the noise levels, the computational time has been also significantly improved with respect to our previous context-based filter which applied full search of full context. We have also compared this improved Markov filter with other denoising techniques existing in the literature, most of them being significantly outperformed.  相似文献   
79.
80.
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