全文获取类型
收费全文 | 259877篇 |
免费 | 9444篇 |
国内免费 | 4829篇 |
专业分类
电工技术 | 9641篇 |
技术理论 | 4篇 |
综合类 | 5296篇 |
化学工业 | 35293篇 |
金属工艺 | 11172篇 |
机械仪表 | 9822篇 |
建筑科学 | 9326篇 |
矿业工程 | 3006篇 |
能源动力 | 6416篇 |
轻工业 | 18873篇 |
水利工程 | 3283篇 |
石油天然气 | 5928篇 |
武器工业 | 997篇 |
无线电 | 34917篇 |
一般工业技术 | 43235篇 |
冶金工业 | 47921篇 |
原子能技术 | 4427篇 |
自动化技术 | 24593篇 |
出版年
2023年 | 1320篇 |
2022年 | 2915篇 |
2021年 | 4478篇 |
2020年 | 3231篇 |
2019年 | 3050篇 |
2018年 | 4094篇 |
2017年 | 4290篇 |
2016年 | 4134篇 |
2015年 | 4483篇 |
2014年 | 6239篇 |
2013年 | 12200篇 |
2012年 | 9629篇 |
2011年 | 11458篇 |
2010年 | 9770篇 |
2009年 | 10401篇 |
2008年 | 10635篇 |
2007年 | 10188篇 |
2006年 | 9376篇 |
2005年 | 8463篇 |
2004年 | 7329篇 |
2003年 | 6469篇 |
2002年 | 6189篇 |
2001年 | 6412篇 |
2000年 | 5929篇 |
1999年 | 6259篇 |
1998年 | 16093篇 |
1997年 | 10740篇 |
1996年 | 8332篇 |
1995年 | 6139篇 |
1994年 | 5252篇 |
1993年 | 5212篇 |
1992年 | 3561篇 |
1991年 | 3363篇 |
1990年 | 3306篇 |
1989年 | 3097篇 |
1988年 | 2837篇 |
1987年 | 2269篇 |
1986年 | 2333篇 |
1985年 | 2619篇 |
1984年 | 2323篇 |
1983年 | 2067篇 |
1982年 | 1912篇 |
1981年 | 2057篇 |
1980年 | 1804篇 |
1979年 | 1663篇 |
1978年 | 1660篇 |
1977年 | 2022篇 |
1976年 | 2705篇 |
1975年 | 1422篇 |
1974年 | 1371篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
Nitrile rubber (NBR) blends with excellent performance have always been a hot research topic in petroleum field. Due to the excellent performance and compatibility of polyamide 6 (PA6), it provides an opportunity for the preparation of high-performance NBR/PA6 blends. In this article, NBR/PA6 blends were prepared by the three-step molding process. Experimentally, it was found that PA6 has a prominent reinforcement effect in NBR matrix. The variation of this mechanical property was investigated from different aspects of the crystal structure, crystallinities, phase morphology, and so on. It can be cleared that the formation of fibrous structure of PA6 phase is the main factor for reinforcement of the polymer blends. Meanwhile, the formation mechanism of the special phase structure induced by the three-step process is deeply expounded and its structural evolution schematic is established. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47472. 相似文献
53.
Akopdzhanyan T. G. Chemagina E. A. Borovinskaya I. P. 《Russian Journal of Non-Ferrous Metals》2020,61(6):686-690
Russian Journal of Non-Ferrous Metals - The synthesis and sintering of the (AlN)x(SiC)1 – x solid solution have been studied under conditions of self-propagating high-temperature synthesis... 相似文献
54.
Zavadiuk S.V. Loboda P.I. Soloviova T.O. Trosnikova I.Iu. Karasevska O.P. 《Powder Metallurgy and Metal Ceramics》2020,59(1-2):22-28
Powder Metallurgy and Metal Ceramics - The properties of sintered and heat-treated steels produced from the Catamold 8740 material by powder injection molding were examined. Parts made of the... 相似文献
55.
56.
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
57.
58.
59.
60.