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   247906篇
  免费   1915篇
  国内免费   260篇
电工技术   4032篇
综合类   89篇
化学工业   39595篇
金属工艺   15141篇
机械仪表   10049篇
建筑科学   4161篇
矿业工程   3752篇
能源动力   3882篇
轻工业   9585篇
水利工程   4085篇
石油天然气   13001篇
武器工业   28篇
无线电   20219篇
一般工业技术   62751篇
冶金工业   32156篇
原子能技术   11136篇
自动化技术   16419篇
  2021年   2743篇
  2019年   2732篇
  2018年   5429篇
  2017年   5715篇
  2016年   6049篇
  2015年   3052篇
  2014年   5325篇
  2013年   10084篇
  2012年   7305篇
  2011年   8928篇
  2010年   7297篇
  2009年   8107篇
  2008年   8177篇
  2007年   7857篇
  2006年   6357篇
  2005年   5563篇
  2004年   5482篇
  2003年   5303篇
  2002年   5135篇
  2001年   4949篇
  2000年   4938篇
  1999年   4257篇
  1998年   7185篇
  1997年   5839篇
  1996年   4426篇
  1995年   3655篇
  1994年   3424篇
  1993年   3608篇
  1992年   3201篇
  1991年   3344篇
  1990年   3469篇
  1989年   3341篇
  1988年   3245篇
  1987年   3243篇
  1986年   3137篇
  1985年   3302篇
  1984年   3239篇
  1983年   3124篇
  1982年   2973篇
  1981年   3022篇
  1980年   3058篇
  1979年   3244篇
  1978年   3477篇
  1977年   3449篇
  1976年   3902篇
  1975年   3206篇
  1974年   3291篇
  1973年   3329篇
  1972年   2986篇
  1971年   2747篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
121.
The authors have determined the causes of drop in performance of induced block caving using fans of blastholes 105 mm in diameter and single blastholes 250 mm in diameter, as well as the sources of increased drilling cost and expansion of start-up time of production blocks in Abakan underground mine. Alternatives of improvement in drilling efficiency under current conditions are discussed.  相似文献   
122.
123.
WO3 is a potential material candidate for construction of photoanode for solar driven water splitting. In this work, μm-thick porous WO3 photoanode is prepared by depositing a stable ink made of WO3 nanoparticles and Aristoflex velvet polymer in water using the doctor blade technique, followed by a sintering in air. The nature of WO3 nanoparticles, its loading mass on F-doped tin oxide electrode as well as sintering temperature are examined in order to optimize the photocatalytic activity of the resultant WO3 photoanode. The operation of WO3 photoanode is investigated by varying the light illumination direction and light incident intensity as well as changing the nature of the electrolyte. Dissolved tungsten in electrolyte is quantified by ICP-MS providing insights into the influences of electrolyte nature and operating conditions to the corrosion of WO3. It is proposed that the H2O2 and OH. radical generated as by-products of the photo-driven water oxidation on the photoanode surface are harmful species that accelerate the dissolution of WO3.  相似文献   
124.
Russian Engineering Research - Thin-film vacuum technology permits the creation of new electrode materials on the basis of a flexible carbon matrix with a highly developed surface. Supercapacitor...  相似文献   
125.
Refractories and Industrial Ceramics - The effect of the addition of 2 and 5 mol.% Dy2O3 during spark-plasma sintering at a compaction loading of 60 MPa in the range of 1200 – 1600°C on...  相似文献   
126.
Refractories and Industrial Ceramics - Results of studying the rheotechnological properties of moldable refractory mixes based on bauxite suspensions plasticized with refractory clay are presented....  相似文献   
127.
The influence of phase composition and microstructure of Ti42.75Zr27Mn20.25V10 alloy on its hydrogenation kinetic and phase composition of hydrogenated product was studied. It is established that the process of dissociation of hydrogen molecules begins on the surface of Laves phase crystallites. The dissolution of atomic hydrogen in the material volume leads to the formation of cracks in the intermetallic crystallites, which further appear as additional centers of dissociation of hydrogen molecules and noticeably accelerate the diffusion of hydrogen into the bulk material. It was shown that the Laves phase acts as a donor of atomic hydrogen for the BCC solid solution during hydrogenation of two-phase structure, initiating intensive hydrogenation of the BCC phase at room temperature.  相似文献   
128.
Power Technology and Engineering - The major results from the survey and geotechnical monitoring during the leveling of the model foundation of the Zagorsk PSP-2 in test site No. 3 are presented....  相似文献   
129.
Russian Engineering Research - The machining precision in grinding a flexible shaft by sharp and blunt wheels is compared for a CNC system with a specified cycle of radial supply velocities. To...  相似文献   
130.
The demand for food production has been constantly increasing due to rising population. In developed countries, for example, the emergence of regional production of old grains that are rarely utilized, along with the production of commonly consumed grains, has gained importance in recent years. These grains, known collectively as ancient or heirloom grains, have offered both farmers and consumers novel ways of cultivation and products with interesting taste, characteristics and nutritional value. Among the 30 000 plant species known, only five cereals currently provide more than 50% of the world's energy intake – bread wheat (Triticum aestivum), rice (Oryza sativa), sorghum (Sorghum bicolor), millets (Panicum sp.) and maize (Zea mays). The excessive utilization of these selected species has a great potential to cause genetic losses and difficulty in bridging future agricultural demands. Teff (Eragrostis tef), an ancient grain extensively cultivated in countries like Eritrea and Ethiopia, provides promising alternatives for new food uses since its nutritional value is significantly higher than most others cereal grains. The absence of gluten allows flexibility in food utilization since it can be directly substituted to gluten-containing products. The grain also offers an excellent balance of essential amino acids and minerals, which can fulfil the recommended daily intake and eliminates the need for fortification and enrichment. This review provides a general overview of the physical properties and nutritional composition of teff grains related to processing and applications in the food and feed industries. The current status of teff utilization, as well as the challenges in production and commercialization, and future opportunities is presented and discussed.  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