全文获取类型
收费全文 | 20880篇 |
免费 | 1756篇 |
国内免费 | 39篇 |
专业分类
电工技术 | 252篇 |
综合类 | 26篇 |
化学工业 | 4963篇 |
金属工艺 | 813篇 |
机械仪表 | 1070篇 |
建筑科学 | 438篇 |
矿业工程 | 12篇 |
能源动力 | 786篇 |
轻工业 | 2017篇 |
水利工程 | 77篇 |
石油天然气 | 28篇 |
武器工业 | 1篇 |
无线电 | 3256篇 |
一般工业技术 | 4593篇 |
冶金工业 | 2074篇 |
原子能技术 | 219篇 |
自动化技术 | 2050篇 |
出版年
2023年 | 233篇 |
2022年 | 368篇 |
2021年 | 599篇 |
2020年 | 455篇 |
2019年 | 514篇 |
2018年 | 644篇 |
2017年 | 716篇 |
2016年 | 801篇 |
2015年 | 711篇 |
2014年 | 977篇 |
2013年 | 1450篇 |
2012年 | 1341篇 |
2011年 | 1722篇 |
2010年 | 1226篇 |
2009年 | 1183篇 |
2008年 | 1052篇 |
2007年 | 863篇 |
2006年 | 711篇 |
2005年 | 621篇 |
2004年 | 607篇 |
2003年 | 540篇 |
2002年 | 458篇 |
2001年 | 380篇 |
2000年 | 367篇 |
1999年 | 361篇 |
1998年 | 719篇 |
1997年 | 479篇 |
1996年 | 326篇 |
1995年 | 228篇 |
1994年 | 232篇 |
1993年 | 224篇 |
1992年 | 151篇 |
1991年 | 119篇 |
1990年 | 111篇 |
1989年 | 115篇 |
1988年 | 82篇 |
1987年 | 64篇 |
1986年 | 75篇 |
1985年 | 84篇 |
1984年 | 79篇 |
1983年 | 57篇 |
1982年 | 47篇 |
1981年 | 48篇 |
1980年 | 49篇 |
1979年 | 44篇 |
1978年 | 35篇 |
1977年 | 60篇 |
1976年 | 91篇 |
1975年 | 42篇 |
1973年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
11.
12.
13.
14.
Properties and applications of β‐glycosidase from Bacteroides thetaiotaomicron that specifically hydrolyses isoflavone glycosides 下载免费PDF全文
Da‐Hye Byun Hye‐Jeong Choi Hye‐Won Lee Hye‐Yeon Jeon Woo‐Jae Choung Jae‐Hoon Shim 《International Journal of Food Science & Technology》2015,50(6):1405-1412
To modify the glycan part of glycosides, the gene encoding β‐glycosidase was cloned from Bacteroides thetaiotaomicron VPI‐5482. The cloned gene, bt_1780, was expressed in Escherichia coli MC1061 and the expressed enzyme was purified using Ni‐NTA affinity chromatography. The purified enzyme, BTBG, showed optimal activity at 50 °C and pH 5.5. Interestingly, this enzyme did not have any hydrolysing activity on ordinary β‐linkage–containing substrates such as xylobiose, lactose and cello‐oligosaccharide, but specifically hydrolysed isoflavone glycosides such as daidzin, genistin and glycitin. Compared to a commercial beta glucosidase, BTBG selectively hydrolysed isoflavone glycosides in soybean extract mixture solution. These results suggest that BTBG may be a specialized enzyme for the hydrolysis of glycosides and that the substrate specificity of BTBG is applicable for the bioconversion of isoflavone glycosides in the food industry. 相似文献
15.
Steffen Vojacek Lukas Schulig Nathalie Wössner Norman Geist Prof. Dr. Walter Langel Prof. Dr. Manfred Jung Prof. Dr. Dennis Schade Prof. Dr. Andreas Link 《ChemMedChem》2019,14(8):853-864
Indoles are privileged structures in medicinal and bioorganic chemistry that are particularly well suited to serve as platforms for diversity. Among many other therapeutic areas, the indole scaffold has been used to design aromatic compounds useful to interfere with enzymes engaged in the regulation of substrate acylation status, such as sirtuins. However, the planarity of the indole ring is not necessarily optimal for all target enzymes, especially when functionalization with aromatic side chains is required. Replacement of flat scaffolds by nonplanar molecular cores dominated by sp3 hybridization is a common strategy to avoid the disadvantages associated with poor solubility and high promiscuity, while covering less-well-explored areas of chemical space. Thus, we synthesized fragment-like tetrahydroindoles suitable for fragment-based drug discovery as well as a well-characterized small library intended as multipurpose screening compounds. For proof of principle, these compounds were screened against sirtuins 1–3, enzymes known to be addressable by indoles. We found that 2,6,6-trimethyl-4-oxo-4,5,6,7-tetrahydro-1H-indole-3-carboxamides are potent and selective SIRT2 inhibitors. Compound 16 t displayed an IC50 value of 0.98 μm and could serve as exquisite starting point for hit-to-lead profiling. 相似文献
16.
Hwang Seongil Park Sang Hyun Jin Maolin Kang Sang Hoon 《Intelligent Service Robotics》2021,14(3):471-484
Intelligent Service Robotics - A robust control designed for multiple degrees-of-freedom (DOF) robot manipulators performing complex tasks requiring frequent physical interaction with unknown... 相似文献
17.
18.
19.
20.
Mani Balamurugan Hui‐Yun Jeong Venkata Surya Kumar Choutipalli Jung Sug Hong Hongmin Seo Natarajan Saravanan Jun Ho Jang Kang‐Gyu Lee Yoon Ho Lee Sang Won Im Venkatesan Subramanian Sun Hee Kim Ki Tae Nam 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(25)
The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons is a challenging task because of the issues in controlling the efficiency and selectivity of the products. Among the various transition metals, copper has attracted attention as it yields more reduced and C2 products even while using mononuclear copper center as catalysts. In addition, it is found that reversible formation of copper nanoparticle acts as the real catalytically active site for the conversion of CO2 to reduced products. Here, it is demonstrated that the dinuclear molecular copper complex immobilized over graphitized mesoporous carbon can act as catalysts for the conversion of CO2 to hydrocarbons (methane and ethylene) up to 60%. Interestingly, high selectivity toward C2 product (40% faradaic efficiency) is achieved by a molecular complex based hybrid material from CO2 in 0.1 m KCl. In addition, the role of local pH, porous structure, and carbon support in limiting the mass transport to achieve the highly reduced products is demonstrated. Although the spectroscopic analysis of the catalysts exhibits molecular nature of the complex after 2 h bulk electrolysis, morphological study reveals that the newly generated copper cluster is the real active site during the catalytic reactions. 相似文献