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   23783篇
  免费   1512篇
  国内免费   74篇
电工技术   340篇
综合类   30篇
化学工业   5051篇
金属工艺   941篇
机械仪表   1462篇
建筑科学   520篇
矿业工程   12篇
能源动力   958篇
轻工业   1999篇
水利工程   107篇
石油天然气   26篇
无线电   4001篇
一般工业技术   5128篇
冶金工业   1731篇
原子能技术   319篇
自动化技术   2744篇
  2024年   16篇
  2023年   278篇
  2022年   166篇
  2021年   750篇
  2020年   530篇
  2019年   587篇
  2018年   769篇
  2017年   735篇
  2016年   868篇
  2015年   693篇
  2014年   1040篇
  2013年   1563篇
  2012年   1621篇
  2011年   1969篇
  2010年   1440篇
  2009年   1453篇
  2008年   1340篇
  2007年   1052篇
  2006年   917篇
  2005年   793篇
  2004年   709篇
  2003年   668篇
  2002年   656篇
  2001年   565篇
  2000年   483篇
  1999年   454篇
  1998年   737篇
  1997年   447篇
  1996年   393篇
  1995年   284篇
  1994年   178篇
  1993年   160篇
  1992年   120篇
  1991年   109篇
  1990年   89篇
  1989年   101篇
  1988年   82篇
  1987年   73篇
  1986年   62篇
  1985年   55篇
  1984年   43篇
  1983年   37篇
  1982年   40篇
  1981年   33篇
  1980年   31篇
  1979年   16篇
  1977年   23篇
  1976年   38篇
  1975年   19篇
  1973年   15篇
排序方式: 共有10000条查询结果,搜索用时 453 毫秒
1.
Food Science and Biotechnology - Various hilling materials (rice hulls, pine sawdust, and perlite) were compared to produce sprout vegetables using beach silvertop (Glehnia littoralis Fr. Schm. ex...  相似文献   
2.
International Journal of Information Security - Machine learning techniques have been widely used and shown remarkable performance in various fields. Along with the widespread utilization of...  相似文献   
3.
4.
5.
The esophagus is a tubular-shaped muscular organ where swallowed fluids and muscular contractions constitute a highly dynamic environment. The turbulent, coordinated processes that occur through the oropharyngeal conduit can often compromise targeted administration of therapeutic drugs to a lesion, significantly reducing therapeutic efficacy. Here, magnetically guidable drug vehicles capable of strongly adhering to target sites using a bioengineered mussel adhesive protein (MAP) to achieve localized delivery of therapeutic drugs against the hydrodynamic physiological conditions are proposed. A suite of highly uniform microparticles embedded with iron oxide (IO) nanoparticles (MAP@IO MPs) is microfluidically fabricated using the genipin-mediated covalent cross-linking of bioengineered MAP. The MAP@IO MPs are successfully targeted to a specific region and prolongedly retained in the tubular-structured passageway. In particular, orally administered MAP@IO MPs are effectively captured in the esophagus in vivo in a magnetically guidable manner. Moreover, doxorubicin (DOX)-loaded MAP@IO MPs exhibit a sustainable DOX release profile, effective anticancer therapeutic activity, and excellent biocompatibility. Thus, the magnetically guidable locomotion and robust underwater adhesive properties of the proteinaceous soft microbots can provide an intelligent modular approach for targeted locoregional therapeutics delivery to a specific lesion site in dynamic fluid-associated tubular organs such as the esophagus.  相似文献   
6.
7.
Food Science and Biotechnology - Aluminum based reflective nanolens arrays were developed via a series of aluminum electropolishing and anodization steps with subsequent selective dissolution of...  相似文献   
8.
9.
A series of anionic conjugated polyelectrolytes (CPEs) is synthesized based on poly(fluorene-co-phenylene) by varying the side-chain ionic density from two to six per repeat units (MPS2-TMA, MPS4-TMA, and MPS6-TMA). The effect of MPS2, 4, 6-TMA as interlayers on top of a hole-extraction layer of poly(bis(4-phenyl)-2,4,6-trimethylphenylamine (PTAA) is investigated in inverted perovskite solar cells (PeSCs). Owing to the improved wettability of perovskites on hydrophobic PTAA with the CPEs, the PeSCs with CPE interlayers demonstrate a significantly enhanced device performance, with negligible device-to-device dependence relative to the reference PeSC without CPEs. By increasing the ionic density in the MPS-TMA interlayers, the wetting, interfacial defect passivation, and crystal growth of the perovskites are significantly improved without increasing the series resistance of the PeSCs. In particular, the open-circuit voltage increases from 1.06 V for the PeSC with MPS2-TMA to 1.11 V for the PeSC with MPS6-TMA. The trap densities of the PeSCs with MPS2,4,6-TMA are further analyzed using frequency-dependent capacitance measurements. Finally, a large-area (1 cm2) PeSC is successfully fabricated with MPS6-TMA, showing a power conversion efficiency of 18.38% with negligible hysteresis and a stable power output under light soaking for 60 s.  相似文献   
10.
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