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   1483826篇
  免费   27659篇
  国内免费   6967篇
电工技术   34104篇
综合类   6483篇
化学工业   270148篇
金属工艺   63847篇
机械仪表   41050篇
建筑科学   45670篇
矿业工程   11360篇
能源动力   50518篇
轻工业   108792篇
水利工程   14828篇
石油天然气   37511篇
武器工业   137篇
无线电   195549篇
一般工业技术   277784篇
冶金工业   158538篇
原子能技术   33794篇
自动化技术   168339篇
  2021年   15819篇
  2020年   12010篇
  2019年   14874篇
  2018年   14934篇
  2017年   14255篇
  2016年   21042篇
  2015年   17432篇
  2014年   28900篇
  2013年   88179篇
  2012年   34690篇
  2011年   46268篇
  2010年   41727篇
  2009年   50455篇
  2008年   43346篇
  2007年   40187篇
  2006年   43786篇
  2005年   38250篇
  2004年   40815篇
  2003年   40782篇
  2002年   40118篇
  2001年   37026篇
  2000年   35350篇
  1999年   34412篇
  1998年   44110篇
  1997年   38476篇
  1996年   34779篇
  1995年   30364篇
  1994年   28479篇
  1993年   28491篇
  1992年   25918篇
  1991年   23031篇
  1990年   23382篇
  1989年   22429篇
  1988年   20901篇
  1987年   19175篇
  1986年   18542篇
  1985年   21927篇
  1984年   22192篇
  1983年   20130篇
  1982年   19197篇
  1981年   19305篇
  1980年   17852篇
  1979年   18402篇
  1978年   17676篇
  1977年   17270篇
  1976年   17941篇
  1975年   15929篇
  1974年   15450篇
  1973年   15492篇
  1972年   12988篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Multimedia Tools and Applications - Discovering the relevant web services for specific applications in the dynamically changing business world becomes very critical. Researchers have used many...  相似文献   
142.
Journal of Materials Science - For transformers and inductors to meet the world’s growing demand for electrical power, more efficient soft magnetic materials with high saturation magnetic...  相似文献   
143.
Mobile Networks and Applications - 5G/6G communication are first generation high speed wireless communication network which integrates the aerial data, terrestrial data and maritime data via...  相似文献   
144.
145.
Studies related to biomaterials that stimulate the repair of living tissue have increased considerably, improving the quality of many people's lives that require surgery due to traumatic accidents, bone diseases, bone defects, and reconstructions. Among these biomaterials, bioceramics and bioactive glasses (BGs) have proved to be suitable for coating materials, cement, scaffolds, and nanoparticles, once they present good biocompatibility and degradability, able to generate osteoconduction on the surrounding tissue. However, the role of biomaterials in hard tissue engineering is not restricted to a structural replacement or for guiding tissue regeneration. Nowadays, it is expected that biomaterials develop a multifunctional role when implanted, orchestrating the process of tissue regeneration and providing to the body the capacity to heal itself. In this way, the incorporation of specific metal ions in bioceramics and BGs structure, including magnesium, silver, strontium, lithium, copper, iron, zinc, cobalt, and manganese are currently receiving enhanced interest as biomaterials for biomedical applications. When an ion is incorporated into the bioceramic structure, a new category of material is created, which has several unique properties that overcome the disadvantages of primitive material and favors its use in different biomedical applications. The doping can enhance handling properties, angiogenic and osteogenic performance, and antimicrobial activity. Therefore, this review aims to summarize the effect of selected metal ion dopants into bioceramics and silicate-based BGs in bone tissue engineering. Furthermore, new applications for doped bioceramics and BGs are highlighted, including cancer treatment and drug delivery.  相似文献   
146.
Theoretical Foundations of Chemical Engineering - The effect of the electrolyte composition, mass-transfer conditions, pore diameter, interpore distance, and electric parameters on the formation of...  相似文献   
147.
Fluoro-substituted and heteroaromatic compounds are valuable intermediates for a variety of applications in pharma- and agrochemistry and synthetic chemistry. This study investigates the chemoenzymatic preparation of chiral alcohols bearing a heteroaromatic ring with an increasing degree of fluorination in α-position. Starting from readily available picoline derivatives prochiral α-halogenated acyl moieties were introduced with excellent selectivity and 64–95 % yield. The formed carbonyl group was subsequently reduced to the corresponding alcohols using the alcohol dehydrogenase from Lactobacillus kefir, yielding an enantiomeric excess of 95–>99 % and up to 98 % yield.  相似文献   
148.
Journal of Inorganic and Organometallic Polymers and Materials - This paper reports the performance of alizarin based SnO2 dye-sensitized solar cells. A novel template assisted method has been...  相似文献   
149.
Applied Composite Materials - Determining the impact behavior of adhesive joints allows the designing of high-strength joints. Therefore, the dynamic behavior of adhesive joints has recently become...  相似文献   
150.
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