全文获取类型
收费全文 | 183280篇 |
免费 | 19792篇 |
国内免费 | 11812篇 |
专业分类
电工技术 | 15596篇 |
技术理论 | 4篇 |
综合类 | 15743篇 |
化学工业 | 25226篇 |
金属工艺 | 11346篇 |
机械仪表 | 12537篇 |
建筑科学 | 15319篇 |
矿业工程 | 6301篇 |
能源动力 | 5517篇 |
轻工业 | 14727篇 |
水利工程 | 4725篇 |
石油天然气 | 8824篇 |
武器工业 | 2313篇 |
无线电 | 22072篇 |
一般工业技术 | 18153篇 |
冶金工业 | 7316篇 |
原子能技术 | 2205篇 |
自动化技术 | 26960篇 |
出版年
2024年 | 934篇 |
2023年 | 3011篇 |
2022年 | 6139篇 |
2021年 | 8364篇 |
2020年 | 6262篇 |
2019年 | 4828篇 |
2018年 | 5336篇 |
2017年 | 6350篇 |
2016年 | 5522篇 |
2015年 | 8278篇 |
2014年 | 10426篇 |
2013年 | 12400篇 |
2012年 | 14487篇 |
2011年 | 15119篇 |
2010年 | 14034篇 |
2009年 | 13146篇 |
2008年 | 12964篇 |
2007年 | 12400篇 |
2006年 | 11133篇 |
2005年 | 8683篇 |
2004年 | 6069篇 |
2003年 | 5088篇 |
2002年 | 4814篇 |
2001年 | 4290篇 |
2000年 | 3395篇 |
1999年 | 2596篇 |
1998年 | 1629篇 |
1997年 | 1347篇 |
1996年 | 1234篇 |
1995年 | 1058篇 |
1994年 | 867篇 |
1993年 | 536篇 |
1992年 | 439篇 |
1991年 | 320篇 |
1990年 | 262篇 |
1989年 | 226篇 |
1988年 | 157篇 |
1987年 | 103篇 |
1986年 | 97篇 |
1985年 | 42篇 |
1984年 | 39篇 |
1983年 | 33篇 |
1982年 | 43篇 |
1981年 | 51篇 |
1980年 | 53篇 |
1979年 | 36篇 |
1977年 | 19篇 |
1965年 | 17篇 |
1959年 | 25篇 |
1951年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
The molecular design of short peptides to achieve a tailor-made functional architecture has attracted attention during the past decade but remains challenging as a result of insufficient understanding of the relationship between peptide sequence and assembled supramolecular structures. We report a hybrid-resolution model to computationally explore the sequence–structure relationship of self-assembly for tripeptides containing only phenylalanine and isoleucine. We found that all these tripeptides have a tendency to assemble into nanofibers composed of laterally associated filaments. Molecular arrangements within the assemblies are diverse and vary depending on the sequences. This structural diversity originates from (1) distinct conformations of peptide building blocks that lead to different surface geometries of the filaments and (2) unique sidechain arrangements at the filament interfaces for each sequence. Many conformations are available for tripeptides in solution, but only an extended β-strand and another resembling a right-handed turn are observed in assemblies. It was found that the sequence dependence of these conformations and the packing of resulting filaments are determined by multiple competing noncovalent forces, with hydrophobic interactions involving Phe being particularly important. The sequence pattern for each type of assembly conformation and packing has been identified. These results highlight the importance of the interplay between conformation, molecular packing, and sequences for determining detailed nanostructures of peptides and provide a detailed insight to support a more precise design of peptide-based nanomaterials. 相似文献
103.
Jialong Tian M. Babar Shahzad Wei Wang Lichang Yin Zhouhua Jiang Ke Yang 《材料科学技术学报》2018,34(9):1671-1675
The effect of Co addition on the formation of Ni-Ti clusters in maraging stainless steel was studied by three dimensional atom probe (3DAP) and first-principles calculation. The cluster analysis based on the maximum separation approach showed an increase in size but a decrease in density of Ni-Ti clusters with increasing the Co content. The first-principles calculation indicated weaker Co-Ni (Co-Ti) interactions than Co-Ti (Fe-Ti) interactions, which should be the essential reason for the change of distribution characteristics of Ni-Ti clusters in bcc Fe caused by Co addition. 相似文献
104.
Yejun Wu Bowen Yan Juan Zhou Huizhang Lian Xiaojun Yu Jianxin Zhao Hao Zhang Wei Chen Daming Fan 《Journal of food science》2020,85(10):3282-3292
105.
106.
Li Wei Ren Yinghui Li Chenfang Li Zhipeng Li Maojun 《The International Journal of Advanced Manufacturing Technology》2020,106(3):921-935
The International Journal of Advanced Manufacturing Technology - The wear of micro-grinding tools less than 1 mm in diameter is crucial for achieving acceptable surface quality and accurate... 相似文献
107.
BDI模型能够很好地解决在特定环境下的Agent的推理和决策问题,但在动态和不确定环境下缺少决策和学习的能力。强化学习解决了Agent在未知环境下的决策问题,却缺少BDI模型中的规则描述和逻辑推理。针对BDI在未知和动态环境下的策略规划问题,提出基于强化学习Q-learning算法来实现BDI Agent学习和规划的方法,并针对BDI的实现模型ASL的决策机制做出了改进,最后在ASL的仿真平台Jason上建立了迷宫的仿真,仿真实验表明,在加入Q-learning学习机制后的新的ASL系统中,Agent在不确定环境下依然可以完成任务。 相似文献
108.
Microsystem Technologies - Recently, nonlinear system identification has received increasingly more attention due to its promising applications in engineering fields. It has become a challenging... 相似文献
109.
Xiangrong Ma Rui Dang Ning Yang Xiao Li Ya zhang Ying Gong Zhipan Liu Wei Guo Yuanyuan Zhang Chunyan Li 《International Journal of Hydrogen Energy》2021,46(44):22842-22851
The high cost of noble metal catalysts has been a great bottleneck for the catalyst industry. Using the noble metal at a single-atom level for catalytic applications could dramatically decrease the cost. The impacts of single Pt atoms on the photocatalytic performance of Ag3VO4 have been investigated and reported. In this report, single Pt atoms were anchored on the surface of Ag3VO4 (AVO) as a cocatalyst, and the resultant composite photocatalyst has been studied for photocatalytic H2 production from water driven by visible light. The as-prepared AVO particles are hollow nanospheres in the monoclinic phase with a bandgap of 2.20 eV. The light absorption edge of AVO/Pt is slightly red-shifted compared to that of the pristine AVO, indicating more visible light absorption of AVO/Pt. The XPS peaks of Ag, V, and Pt exhibit a significant shift after AVO and Pt get into contact, suggesting the strong interaction between the surface Ag and V atoms, and single Pt atoms. After 3-h illumination, the photocatalytic H2 evolution amount from AVO/Pt is improved up to 1400 μmol, which is 2.8 times that on the bare AVO. Such efficient photocatalytic H2 evolution on AVO/Pt is still maintained after five reaction cycles. The better photocatalytic performance of AVO/Pt has been attributed to the more efficient visible light utilization and the lower interfacial charge transfer resistance, as demonstrated in the DRS and EIS spectra. The presence of the surface Pt atoms also leads to a higher amount of reactive radicals, which could efficiently promote the surface redox reactions. 相似文献
110.