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   327083篇
  免费   5483篇
  国内免费   727篇
电工技术   6534篇
综合类   625篇
化学工业   50857篇
金属工艺   10849篇
机械仪表   9259篇
建筑科学   8916篇
矿业工程   991篇
能源动力   8913篇
轻工业   33316篇
水利工程   2675篇
石油天然气   3694篇
武器工业   8篇
无线电   40875篇
一般工业技术   63105篇
冶金工业   57139篇
原子能技术   5589篇
自动化技术   29948篇
  2021年   2730篇
  2020年   2048篇
  2019年   2509篇
  2018年   4286篇
  2017年   4111篇
  2016年   4321篇
  2015年   3205篇
  2014年   5227篇
  2013年   15772篇
  2012年   8332篇
  2011年   11290篇
  2010年   8867篇
  2009年   9980篇
  2008年   10556篇
  2007年   10498篇
  2006年   9151篇
  2005年   8391篇
  2004年   8192篇
  2003年   7902篇
  2002年   7760篇
  2001年   7861篇
  2000年   7478篇
  1999年   7754篇
  1998年   17830篇
  1997年   13022篇
  1996年   10250篇
  1995年   8030篇
  1994年   7323篇
  1993年   7007篇
  1992年   5393篇
  1991年   5161篇
  1990年   5014篇
  1989年   4846篇
  1988年   4740篇
  1987年   3944篇
  1986年   4057篇
  1985年   4847篇
  1984年   4413篇
  1983年   4114篇
  1982年   3690篇
  1981年   3874篇
  1980年   3548篇
  1979年   3491篇
  1978年   3305篇
  1977年   3868篇
  1976年   4908篇
  1975年   2854篇
  1974年   2710篇
  1973年   2732篇
  1972年   2247篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Potential mGAT4 inhibitors derived from the lead substance (S)-SNAP-5114 have been synthesized and characterized for their inhibitory potency. Variations from the parent compound included the substitution of one of its aromatic 4-methoxy and 4-methoxyphenyl groups, respectively, with a more polar moiety, including a carboxylic acid, alcohol, nitrile, carboxamide, sulfonamide, aldehyde or ketone function, or amino acid partial structures. Furthermore, it was investigated how the substitution of more than one of the aromatic 4-methoxy groups affects the potency and selectivity of the resulting compounds. Among the synthesized test substances (S)-1-{2-[(4-formylphenyl)bis(4-methoxyphenyl)-methoxy]ethyl}piperidine-3-carboxylic acid, that features a carbaldehyde function in place of one of the aromatic 4-methoxy moieties of (S)-SNAP-5114, was found to have a pIC50 value of 5.89±0.07, hence constituting a slightly more potent mGAT4 inhibitor than the parent substance while showing comparable subtype selectivity.  相似文献   
72.
JOM - Alpha-radiation damage in metals is a concern for long-term radioactive storage and systems that produce nuclear energy. Accurate prediction of irradiated material properties and failure...  相似文献   
73.
74.
75.
76.
The work reported involved the fabrication of an electrospun tubular conduit of a gelatin and polycaprolactone (PCL) blend as an adventitia‐equivalent construct. Gelatin was included as the matrix for increased biocompatibility with the addition of PCL for durability. This is contrary to most of the literature available for biomaterials based on blends of gelatin and PCL where PCL is the major matrix. The work includes the assiduous selection of key electrospinning parameters to obtain smooth bead‐free fibres with a narrow distribution of pore size and fibre diameter. Few reports elucidate the optimization of all electrospinning parameters to fabricate tubular conduits with a focus on obtaining homogeneous pores and fibres. This stepwise investigation would be unique for the fabrication of gelatin–PCL electrospun tubular constructs. The fabricated microfibrous gelatin–PCL constructs had pores of size ca 50–100 μm reportedly conducive for cell infiltration. The measured value of surface roughness of 57.99 ± 17.4 nm is reported to be favourable for protein adhesion and cell adhesion. The elastic modulus was observed to be similar to that of the tunica adventitia of the native artery. Preliminary in vitro and in vivo biocompatibility tests suggest safe applicability as a biomaterial. Minimal cytotoxicity was observed using MTT assay. Subcutaneous implantation of the scaffold demonstrated acute inflammation which decreased by day 15. The findings of this study could enable the fabrication of smooth bead‐free microfibrous gelatin–PCL tubular construct as viable biomaterial which can be included in a bilayer or a trilayer scaffold for vascular tissue engineering. © 2019 Society of Chemical Industry  相似文献   
77.
78.
79.
80.
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