全文获取类型
收费全文 | 275733篇 |
免费 | 4419篇 |
国内免费 | 887篇 |
专业分类
电工技术 | 5197篇 |
综合类 | 276篇 |
化学工业 | 41664篇 |
金属工艺 | 10171篇 |
机械仪表 | 8078篇 |
建筑科学 | 7434篇 |
矿业工程 | 1002篇 |
能源动力 | 7761篇 |
轻工业 | 23888篇 |
水利工程 | 2409篇 |
石油天然气 | 3290篇 |
武器工业 | 16篇 |
无线电 | 35802篇 |
一般工业技术 | 55357篇 |
冶金工业 | 49485篇 |
原子能技术 | 5258篇 |
自动化技术 | 23951篇 |
出版年
2022年 | 1763篇 |
2021年 | 2820篇 |
2020年 | 2027篇 |
2019年 | 2379篇 |
2018年 | 4069篇 |
2017年 | 4085篇 |
2016年 | 4308篇 |
2015年 | 2956篇 |
2014年 | 4901篇 |
2013年 | 13308篇 |
2012年 | 7441篇 |
2011年 | 10041篇 |
2010年 | 8084篇 |
2009年 | 9053篇 |
2008年 | 9596篇 |
2007年 | 9461篇 |
2006年 | 8221篇 |
2005年 | 7199篇 |
2004年 | 6901篇 |
2003年 | 7137篇 |
2002年 | 6587篇 |
2001年 | 6939篇 |
2000年 | 6358篇 |
1999年 | 6679篇 |
1998年 | 16753篇 |
1997年 | 11682篇 |
1996年 | 9017篇 |
1995年 | 6829篇 |
1994年 | 6085篇 |
1993年 | 6028篇 |
1992年 | 4281篇 |
1991年 | 4158篇 |
1990年 | 3980篇 |
1989年 | 3771篇 |
1988年 | 3671篇 |
1987年 | 3121篇 |
1986年 | 3027篇 |
1985年 | 3378篇 |
1984年 | 3117篇 |
1983年 | 2954篇 |
1982年 | 2750篇 |
1981年 | 2676篇 |
1980年 | 2578篇 |
1979年 | 2415篇 |
1978年 | 2210篇 |
1977年 | 2692篇 |
1976年 | 3652篇 |
1975年 | 1875篇 |
1974年 | 1798篇 |
1973年 | 1752篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Emma Layton Anna-Marie Fairhurst Sam Griffiths-Jones Richard K. Grencis Ian S. Roberts 《International journal of molecular sciences》2020,21(23)
In eukaryotes, microRNAs (miRNAs) have roles in development, homeostasis, disease and the immune response. Recent work has shown that plant and mammalian miRNAs also mediate cross-kingdom and cross-domain communications. However, these studies remain controversial and are lacking critical mechanistic explanations. Bacteria do not produce miRNAs themselves, and therefore it is unclear how these eukaryotic RNA molecules could function in the bacterial recipient. In this review, we compare and contrast the biogenesis and functions of regulatory RNAs in eukaryotes and bacteria. As a result, we discovered several conserved features and homologous components in these distinct pathways. These findings enabled us to propose novel mechanisms to explain how eukaryotic miRNAs could function in bacteria. Further understanding in this area is necessary to validate the findings of existing studies and could facilitate the use of miRNAs as novel tools for the directed remodelling of the human microbiota. 相似文献
32.
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
33.
34.
35.
36.
37.
38.
39.
Breslavs’kyi D. V. Metel’yov V. O. Morachkovs’kyi O. K. Tatarinova O. A. 《Strength of Materials》2019,51(5):753-760
Strength of Materials - Creep constitutive equations have been derived for the materials that exhibit the properties of orthotropy (transversal isotropy) and transient creep under cyclic loading. A... 相似文献
40.
Microsystem Technologies - The strategy for analysis of noise generated in the analog circuit is presented here. Further, methodology for optimization of noise to improve the performance of the... 相似文献