全文获取类型
收费全文 | 17725篇 |
免费 | 1438篇 |
国内免费 | 344篇 |
专业分类
电工技术 | 79篇 |
综合类 | 713篇 |
化学工业 | 12129篇 |
金属工艺 | 272篇 |
机械仪表 | 117篇 |
建筑科学 | 176篇 |
矿业工程 | 159篇 |
能源动力 | 203篇 |
轻工业 | 1773篇 |
水利工程 | 9篇 |
石油天然气 | 1227篇 |
武器工业 | 42篇 |
无线电 | 244篇 |
一般工业技术 | 2008篇 |
冶金工业 | 106篇 |
原子能技术 | 140篇 |
自动化技术 | 110篇 |
出版年
2024年 | 66篇 |
2023年 | 258篇 |
2022年 | 384篇 |
2021年 | 787篇 |
2020年 | 492篇 |
2019年 | 492篇 |
2018年 | 406篇 |
2017年 | 482篇 |
2016年 | 519篇 |
2015年 | 574篇 |
2014年 | 841篇 |
2013年 | 894篇 |
2012年 | 1086篇 |
2011年 | 1076篇 |
2010年 | 854篇 |
2009年 | 962篇 |
2008年 | 881篇 |
2007年 | 1033篇 |
2006年 | 1138篇 |
2005年 | 940篇 |
2004年 | 824篇 |
2003年 | 752篇 |
2002年 | 590篇 |
2001年 | 538篇 |
2000年 | 440篇 |
1999年 | 428篇 |
1998年 | 328篇 |
1997年 | 280篇 |
1996年 | 194篇 |
1995年 | 176篇 |
1994年 | 171篇 |
1993年 | 158篇 |
1992年 | 124篇 |
1991年 | 83篇 |
1990年 | 45篇 |
1989年 | 51篇 |
1988年 | 25篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 24篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 24篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
22.
Tomonari Tanaka Ayane Matsuura Yuji Aso Hitomi Ohara 《Journal of Applied Glycoscience》2020,67(4):119
Glycopolymers have attracted increased attention as functional polymeric materials, and simple methods for synthesizing glycopolymers remain needed. This paper reports the aqueous one-pot and chemoenzymatic synthesis of four types of glycopolymers via two reactions: the β-galactosidase-catalyzed glycomonomer synthesis using 4,6-dimetoxy triazinyl β-D-galactopyranoside and hydroxy group-containing (meth)acrylamide and (meth)acrylate derivatives as the activated glycosyl donor substrate and as the glycomonomer precursors, respectively, followed by radical copolymerization of the resulting glycomonomer and excess glycomonomer precursor without isolating the glycomonomers. The resulting glycopolymers bearing galactose moieties exhibited specific and strong interactions with the lectin peanut agglutinin as glycoclusters. 相似文献
23.
Luc Rochette Loubna Mazini Gabriel Malka Marianne Zeller Yves Cottin Catherine Vergely 《International journal of molecular sciences》2020,21(23)
The potential use of stem cell-based therapies for the repair and regeneration of various tissues and organs is a major goal in repair medicine. Stem cells are classified by their potential to differentiate into functional cells. Compared with other sources, adipose-derived stem cells (ADSCs) have the advantage of being abundant and easy to obtain. ADSCs are considered to be tools for replacing, repairing, and regenerating dead or damaged cells. The capacity of ADSCs to maintain their properties depends on the balance of complex signals in their microenvironment. Their properties and the associated outcomes are in part regulated by reactive oxygen species, which mediate the oxidation-reduction state of cells as a secondary messenger. ADSC therapy has demonstrated beneficial effects, suggesting that secreted factors may provide protection. There is evidence that ADSCs secrete a number of cytokines, growth factors, and antioxidant factors into their microenvironment, thus regulating intracellular signaling pathways in neighboring cells. In this review, we introduce the roles of ADSCs in the protection of cells by modulating inflammation and immunity, and we develop their potential therapeutic properties. 相似文献
24.
Slim Salhi Jihen Mahfoudh Souhir Abid Leonard‐Ionut Atanase Marcel Popa Christelle Delaite 《Polymer International》2020,69(11):1161-1168
A series of random polyesteramides (PEAs) with a range of molar composition from 90/10 to 50/50 were synthesized by direct melt polycondensation of ε‐caprolactone and l ‐alanine. Their structure was fully characterized by Fourier transform IR and NMR spectroscopy. The resulting copolymers are completely amorphous with the exception of PEA‐90/10 which possesses a semicrystalline structure. These PEAs present increasing glass transition temperatures at increasing l ‐alanine contents and exhibit fairly good thermal stability with 10% mass loss temperatures reaching 315 °C. © 2020 Society of Industrial Chemistry 相似文献
25.
A facile and effective method was proposed to prepare the molecularly imprinted fluorescence sensor with carbon quantum dots, which were modified vinyl groups by acrylic acid on the surface. The obtained fluorescence composite material was investigated by transmission electron microscope and Fourier transform infrared spectra. After the experimental conditions were optimized, a linear range of 1.0–60 μmol L−1 was obtained and the detection limit was 0.17 μmol L−1. The novel fluorescence sensor can be successfully used to detect tetracycline in real samples. This study provides a convenient strategy for selective recognition and rapid detection of tetracycline in the complex environment. 相似文献
26.
Isopimaric acid is a typical rosin compound and can account for 30% of the total mass of slash pine rosin. The molecular structure of isopimaric acid derivatives features an unsaturated double bond at the C13 position, opening up the possibility of their industrial polymerization. In this study, isopimaric acid (95.4%), methyl isopimarate (99.5%), and allyl isopimarate (95.1%) were prepared as highly pure monomers. New experimental results are presented and mechanisms based on the investigation of free-radical polymerization under UV irradiation are proposed. New rosin monomers for potential value-added utilization of woody biomass are also identified. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47817. 相似文献
27.
28.
29.
溶胶-凝胶法制备Na_2WO_4~-Mn/SiO_2催化剂及其甲烷氧化偶联反应性能的研究 总被引:3,自引:3,他引:0
采用溶胶-凝胶法制备了一系列5%Na2WO4-2%Mn/SiO2催化剂;用XRD、XPS、BET、O2-TPD和CO2-TPD等方法对催化剂进行了表征,并考察了对甲烷氧化偶联反应的催化性能。结果表明,与常规浸渍法相比,采用溶胶-凝胶法制备的Na2WO4-Mn/SiO2催化剂中W和Mn的原子浓度在催化剂表面和体相分布较为接近,而且两种制备方法所得的催化剂具有相似的催化性能,Na2WO4与α-方石英之间的相互作用,催化剂释放晶格氧的能力,碱性强弱是影响甲烷氧化偶联活性的关键因素。 相似文献
30.
几种酚类抗氧剂在润滑油中的应用 总被引:2,自引:0,他引:2
采用旋转氧弹法、高压差示扫描量热法等方法研究了5种酚类抗氧剂对6种润滑油基础油氧化安定性的改善效果。结果表明:向加氢基础油中加入0.25%(质量分数)抗氧剂2246-S和RHY510(含硫酚类抗氧剂),可使HVIWH125,HVIWH150,HVIWH500,KN4006,KN40105种润滑油基础油的诱导期由27~88min提高到226~397min;使HVIWH125,HVIWH150,HVIWH300,HVIWH500,KN4006,KN40106种润滑油基础油的起始氧化温度由193.34~198.90℃提高到205.48~230.27℃。 相似文献