全文获取类型
收费全文 | 10666篇 |
免费 | 1042篇 |
国内免费 | 569篇 |
专业分类
电工技术 | 562篇 |
技术理论 | 1篇 |
综合类 | 662篇 |
化学工业 | 1831篇 |
金属工艺 | 632篇 |
机械仪表 | 703篇 |
建筑科学 | 854篇 |
矿业工程 | 299篇 |
能源动力 | 292篇 |
轻工业 | 976篇 |
水利工程 | 243篇 |
石油天然气 | 638篇 |
武器工业 | 87篇 |
无线电 | 1050篇 |
一般工业技术 | 1187篇 |
冶金工业 | 509篇 |
原子能技术 | 146篇 |
自动化技术 | 1605篇 |
出版年
2024年 | 23篇 |
2023年 | 147篇 |
2022年 | 357篇 |
2021年 | 479篇 |
2020年 | 382篇 |
2019年 | 295篇 |
2018年 | 345篇 |
2017年 | 392篇 |
2016年 | 341篇 |
2015年 | 502篇 |
2014年 | 530篇 |
2013年 | 671篇 |
2012年 | 702篇 |
2011年 | 817篇 |
2010年 | 665篇 |
2009年 | 603篇 |
2008年 | 583篇 |
2007年 | 559篇 |
2006年 | 523篇 |
2005年 | 478篇 |
2004年 | 355篇 |
2003年 | 283篇 |
2002年 | 270篇 |
2001年 | 212篇 |
2000年 | 296篇 |
1999年 | 291篇 |
1998年 | 246篇 |
1997年 | 179篇 |
1996年 | 185篇 |
1995年 | 140篇 |
1994年 | 85篇 |
1993年 | 77篇 |
1992年 | 60篇 |
1991年 | 45篇 |
1990年 | 39篇 |
1989年 | 24篇 |
1988年 | 29篇 |
1987年 | 10篇 |
1986年 | 20篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1977年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
4.
Fire Technology - Fire dynamic characteristics in multi-compartments are still not very clear. This paper presents a spreading fire test in a full-scale two-storey steel framed building to... 相似文献
5.
Yuanyuan Chen Jian Peng Tian Sheng Ruixuan Qin Shuqi Dai Zaifa Shi Zichao Tang Laisen Wang Qinghua Zhang Bin Han Liping Sun Jun Xu Jian Weng 《Advanced functional materials》2021,31(42):2104246
Radicals are closely related to human life and health and have been widely used in biology, chemistry, functional materials, etc. However, the high reactivity, disorder, and short half-lives limit their wide applications. Therefore, it remains a great challenge to prepare stable and ordered radicals. Herein, radicals are prepared with protective umbrellas (diethylmethyleneamine, DEMA) that are integrated on the surface of 2D layered materials to isolate water and oxygen and enhance the stability of radicals. Taking 2D black phosphorus (BP) as an example: triethylamine reacts with dichloromethane to form quaternary ammonium salts with further Hoffmann elimination to produce DEMA radicals that could react with one electron of a lone pair electrons in P on the surface of BP to produce P radicals, which shows a prolonged half-life of 21 days at room temperature. First-principle calculations and electron paramagnetic resonance fitting confirm that the steric hindrance constructed by dense DEMA passivation layer acts as a protective umbrella and the 2D coupling of P radicals and other P atoms in 2D BP plane to enhance the stability and strong superexchange interaction of P radicals. Furthermore, it is a general strategy to produce stable radicals integrated on the 2D plane. 相似文献
6.
针对呼吸道系统疾病与大气 PM2:5、 SO2 浓度序列的相关性特征, 应用多重分形消除趋势波动分析法
(MF-DCCA), 对张家界市永定区呼吸道系统疾病患病人数与大气 PM2:5、 SO2 浓度序列进行了研究。结果发现该地区
呼吸道系统疾病患病人数与大气 PM2:5、 SO2 浓度的相关性具有长期持续特征和多重分形特征。随后对它们相关性
多重分形特征的动力来源进行了分析, 通过随机重排和相位随机处理, 结果表明在不同时间尺度上的长期持续性影响
是其主要动力来源。进一步研究发现该地区呼吸道系统疾病与大气 PM2:5、 SO2 浓度序列的相关性在四个季节均具
有长期持续性的多重分形特征, 且夏季多重分形特征相对强于其他季节。 相似文献
7.
Catalysis Letters - In this paper, five recombinant strains: GS115-LacA, GS115-LacB, GS115-LacC, KM71H-Lcc1 and GS115-Lcc2 were selected to produce laccase isozymes with high activities, which... 相似文献
8.
9.
10.
Dr. Katie R. Witkin Dr. Nicholas R. Vance Colleen Caldwell Dr. Quinn Li Dr. Liping Yu Prof. M. Ashley Spies 《ChemMedChem》2020,15(4):376-384
Glutamate racemases (GR) are members of the family of bacterial enzymes known as cofactor-independent racemases and epimerases and catalyze the stereoinversion of glutamate. D-amino acids are universally important for the proper construction of viable bacterial cell walls, and thus have been repeatedly validated as attractive targets for novel antimicrobial drug design. Significant aspects of the mechanism of this challenging stereoinversion remain unknown. The current study employs a combination of MD and QM/MM computational approaches to show that the GR from H. pylori must proceed via a pre-activation step, which is dependent on the enzyme's flexibility. This mechanism is starkly different from previously proposed mechanisms. These findings have immediate pharmaceutical relevance, as the H. pylori GR enzyme is a very attractive allosteric drug target. The results presented in this study offer a distinctly novel understanding of how AstraZeneca's lead series of inhibitors cripple the H. pylori GR's native motions, via prevention of this critical chemical pre-activation step. Our experimental studies, using SPR, fluorescence and NMR WaterLOGSY, show that H. pylori GR is not inhibited by the uncompetitive mechanism originally put forward by Lundqvist et al.. The current study supports a deep connection between native enzyme motions and chemical reactivity, which has strong relevance to the field of allosteric drug discovery. 相似文献