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   1469980篇
  免费   27118篇
  国内免费   6994篇
电工技术   34338篇
综合类   6469篇
化学工业   267127篇
金属工艺   64174篇
机械仪表   41836篇
建筑科学   45485篇
矿业工程   11436篇
能源动力   50192篇
轻工业   109326篇
水利工程   14683篇
石油天然气   37743篇
武器工业   153篇
无线电   195580篇
一般工业技术   278282篇
冶金工业   145589篇
原子能技术   34021篇
自动化技术   167658篇
  2021年   15424篇
  2020年   11778篇
  2019年   14553篇
  2018年   15540篇
  2017年   14844篇
  2016年   21078篇
  2015年   17266篇
  2014年   28586篇
  2013年   87600篇
  2012年   34554篇
  2011年   46798篇
  2010年   42144篇
  2009年   50780篇
  2008年   43839篇
  2007年   40991篇
  2006年   43984篇
  2005年   38768篇
  2004年   40980篇
  2003年   40864篇
  2002年   40122篇
  2001年   36525篇
  2000年   35157篇
  1999年   33798篇
  1998年   38980篇
  1997年   35487篇
  1996年   32908篇
  1995年   29356篇
  1994年   27651篇
  1993年   27535篇
  1992年   25855篇
  1991年   22832篇
  1990年   23295篇
  1989年   22348篇
  1988年   20778篇
  1987年   19136篇
  1986年   18478篇
  1985年   21847篇
  1984年   22185篇
  1983年   20161篇
  1982年   19175篇
  1981年   19250篇
  1980年   17898篇
  1979年   18454篇
  1978年   17690篇
  1977年   17312篇
  1976年   17941篇
  1975年   15982篇
  1974年   15503篇
  1973年   15593篇
  1972年   13057篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
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   
142.
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   
143.
144.
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   
145.
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   
146.
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   
147.
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   
148.
149.
Xanthohumol (XH) is an important prenylated flavonoid that is found within the inflorescence of Humulus lupulus L. (Hop plant). XH is an important ingredient in beer and is considered a significant bioactive agent due to its diverse medicinal applications, which include anti-inflammatory, antimicrobial, antioxidant, immunomodulatory, antiviral, antifungal, antigenotoxic, antiangiogenic, and antimalarial effects as well as strong anticancer activity towards various types of cancer cells. XH acts as a wide ranging chemopreventive and anticancer agent, and its isomer, 8-prenylnaringenin, is a phytoestrogen with strong estrogenic activity. The present review focuses on the bioactivity of XH on various types of cancers and its pharmacokinetics. In this paper, we first highlight, in brief, the history and use of hops and then the chemistry and structure–activity relationship of XH. Lastly, we focus on its prominent effects and mechanisms of action on various cancers and its possible use in cancer prevention and treatment. Considering the limited number of available reviews on this subject, our goal is to provide a complete and detailed understanding of the anticancer effects of XH against different cancers.  相似文献   
150.
In flash sintering experiments, the thermal history of the sample is key to understanding the mechanisms underlying densification rate and final properties. By combining robust temperature measurements with current-ramp-rate control, this study examined the effects of the thermal profile on the flash sintering of yttria-stabilized zirconia, with experiments ranging from a few seconds to several hours. The final density was maximized at slower heating rates, although processes slower than a certain threshold led to grain growth. The amount of grain growth observed was comparable to a similar conventional thermal process. The bulk electrical conductivity correlated with the maximum temperature and cooling rate. The only property that exhibited behavior that could not be attributed to solely the thermal profile was the grain boundary conductivity, which was consistently higher than conventional in flash sintered samples. These results suggest that, during flash sintering, athermal electric field effects are relegated to the grain boundary.  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