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   1599761篇
  免费   36557篇
  国内免费   12880篇
电工技术   42236篇
技术理论   9篇
综合类   15062篇
化学工业   289161篇
金属工艺   70419篇
机械仪表   50230篇
建筑科学   54621篇
矿业工程   14687篇
能源动力   53334篇
轻工业   118874篇
水利工程   17210篇
石油天然气   43352篇
武器工业   1229篇
无线电   209571篇
一般工业技术   294615篇
冶金工业   154135篇
原子能技术   35535篇
自动化技术   184918篇
  2022年   14305篇
  2021年   20957篇
  2020年   15851篇
  2019年   17759篇
  2018年   19705篇
  2017年   19549篇
  2016年   24770篇
  2015年   22058篇
  2014年   34427篇
  2013年   94451篇
  2012年   42790篇
  2011年   55813篇
  2010年   49622篇
  2009年   57783篇
  2008年   50999篇
  2007年   47660篇
  2006年   50135篇
  2005年   44191篇
  2004年   44734篇
  2003年   44645篇
  2002年   43720篇
  2001年   40136篇
  2000年   38002篇
  1999年   36650篇
  1998年   41840篇
  1997年   37717篇
  1996年   34783篇
  1995年   30867篇
  1994年   28909篇
  1993年   28447篇
  1992年   26623篇
  1991年   23530篇
  1990年   23746篇
  1989年   22697篇
  1988年   21189篇
  1987年   19457篇
  1986年   18788篇
  1985年   22057篇
  1984年   22325篇
  1983年   20283篇
  1982年   19236篇
  1981年   19311篇
  1980年   17893篇
  1979年   18493篇
  1978年   17705篇
  1977年   17193篇
  1976年   17748篇
  1975年   15965篇
  1974年   15539篇
  1973年   15590篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
A layer-by-layer analysis of the structures, the phase compositions, and the defect substructures of differentially hardened rails has been carried by optical and transmission electron microscopy. It is found that the material volume of the rail head fillet is cooled faster than the volume located along the central axis.  相似文献   
23.
24.
25.
Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product.  相似文献   
26.
27.
Cable‐shaped supercapacitors (SCs) have recently aroused significant attention due to their attractive properties such as small size, lightweight, and bendability. Current cable‐shaped SCs have symmetric device configuration. However, if an asymmetric design is used in cable‐shaped supercapacitors, they would become more attractive due to broader cell operation voltages, which results in higher energy densities. Here, a novel coil‐type asymmetric supercapacitor electrical cable (CASEC) is reported with enhanced cell operation voltage and extraordinary mechanical‐electrochemical stability. The CASECs show excellent charge–discharge profiles, extraordinary rate capability (95.4%), high energy density (0.85 mWh cm−3), remarkable flexibility and bendability, and superior bending cycle stability (≈93.0% after 4000 cycles at different bending states). In addition, the CASECs not only exhibit the capability to store energy but also to transmit electricity simultaneously and independently. The integrated electrical conduction and storage capability of CASECS offer many potential applications in solar energy storage and electronic gadgets.  相似文献   
28.
29.
30.
Here we report some recent biophysical issues on the preparation of solute-filled lipid vesicles and their relevance to the construction of “synthetic cells.” First, we introduce the “semi-synthetic minimal cells” as the liposome-based cell-like systems, which contain a minimal number of biomolecules required to display simple and complex biological functions. Next, we focus on recent aspects related to the construction of synthetic cells. Emphasis is given to the interplay between the methods of synthetic cell preparation and the physics of solute encapsulation. We briefly introduce the notion of structural and compositional “diversity” in synthetic cell populations.  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