全文获取类型
收费全文 | 296296篇 |
免费 | 11821篇 |
国内免费 | 6135篇 |
专业分类
电工技术 | 10777篇 |
技术理论 | 7篇 |
综合类 | 7802篇 |
化学工业 | 40524篇 |
金属工艺 | 18625篇 |
机械仪表 | 16365篇 |
建筑科学 | 13009篇 |
矿业工程 | 4400篇 |
能源动力 | 7067篇 |
轻工业 | 14837篇 |
水利工程 | 3917篇 |
石油天然气 | 9435篇 |
武器工业 | 891篇 |
无线电 | 36366篇 |
一般工业技术 | 55739篇 |
冶金工业 | 36533篇 |
原子能技术 | 3770篇 |
自动化技术 | 34188篇 |
出版年
2024年 | 603篇 |
2023年 | 2245篇 |
2022年 | 3958篇 |
2021年 | 5512篇 |
2020年 | 4231篇 |
2019年 | 3783篇 |
2018年 | 13445篇 |
2017年 | 14606篇 |
2016年 | 9425篇 |
2015年 | 6119篇 |
2014年 | 7208篇 |
2013年 | 11374篇 |
2012年 | 12685篇 |
2011年 | 20484篇 |
2010年 | 18403篇 |
2009年 | 17452篇 |
2008年 | 17103篇 |
2007年 | 19107篇 |
2006年 | 10015篇 |
2005年 | 12645篇 |
2004年 | 8962篇 |
2003年 | 7942篇 |
2002年 | 6360篇 |
2001年 | 5790篇 |
2000年 | 5728篇 |
1999年 | 6188篇 |
1998年 | 12009篇 |
1997年 | 8376篇 |
1996年 | 6811篇 |
1995年 | 4943篇 |
1994年 | 4259篇 |
1993年 | 3787篇 |
1992年 | 2495篇 |
1991年 | 2278篇 |
1990年 | 1990篇 |
1989年 | 1739篇 |
1988年 | 1522篇 |
1987年 | 1098篇 |
1986年 | 1051篇 |
1985年 | 1012篇 |
1984年 | 867篇 |
1983年 | 741篇 |
1982年 | 761篇 |
1981年 | 720篇 |
1980年 | 602篇 |
1979年 | 486篇 |
1978年 | 417篇 |
1977年 | 533篇 |
1976年 | 958篇 |
1975年 | 299篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
ABSTRACT This study investigates the effects of strain, strain rates, and forming directions (RD-rolling direction, TD-transverse direction, and ND-normal direction) on adiabatic shear, via dynamic impact compression tests using the Split Hopkinson Pressure Bar (SHPB) apparatus. A modified Johnson-Cook (J-C) constitutive model is proposed, which used to analyse the influence of the constitutive parameters on the sensitivity of adiabatic shear, employing a finite element software. The different sensitivities of adiabatic shear under different directions are explained by combining microscopic analysis and results from mechanical responses. The results show that the sensitivity of adiabatic shear can be related to the time of stress collapse in the following trend: ND?>?TD?>?RD; the sensitivities of these constitutive parameters on adiabatic shear are calculated and compared. 相似文献
62.
63.
64.
Ming-Puu Chen Asta Y. Z. Lord Yu-Yao Cheng Ku-Chou Tai Wen-Harn Pan 《Journal of Computer Assisted Learning》2020,36(3):383-396
Reflective judgement is crucial for medical-related practitioners in dealing with controversial issues. However, the conformity phenomenon is likely to occur and interfere with reflective judgement learning during interactive activities. Effective strategies are required to moderate the conformity behaviour tendency (CBT) and improve reflective judgement performance (RJP). This study demonstrates two significant results: (a) Compared with the guided self-reflection learning strategy, the online collective reflection (OCR) learning strategy effectively weakened the learners' general CBT while dealing with professional controversial issues; and (b) a significantly negative correlation between the RJP achieved and the change of CBT in online environment was detected in the OCR group. The implications and potential applications in higher education were discussed. Further studies are needed to confirm the long-term effects and the extending application to other professional studies. 相似文献
65.
Yong Xu Yun Li Songlin Li Francis Balestra Gerard Ghibaudo Wenwu Li Yen‐Fu Lin Huabin Sun Jing Wan Xinran Wang Yufeng Guo Yi Shi Yong‐Young Noh 《Advanced functional materials》2020,30(20)
Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field‐effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate‐dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research. 相似文献
66.
Ionomics is a novel multidisciplinary field that uses advanced techniques to investigate the composition and distribution of all minerals and trace elements in a living organism and their variations under diverse physiological and pathological conditions. It involves both high-throughput elemental profiling technologies and bioinformatic methods, providing opportunities to study the molecular mechanism underlying the metabolism, homeostasis, and cross-talk of these elements. While much effort has been made in exploring the ionomic traits relating to plant physiology and nutrition, the use of ionomics in the research of serious diseases is still in progress. In recent years, a number of ionomic studies have been carried out for a variety of complex diseases, which offer theoretical and practical insights into the etiology, early diagnosis, prognosis, and therapy of them. This review aims to give an overview of recent applications of ionomics in the study of complex diseases and discuss the latest advances and future trends in this area. Overall, disease ionomics may provide substantial information for systematic understanding of the properties of the elements and the dynamic network of elements involved in the onset and development of diseases. 相似文献
67.
Dr. Jiayao Y. Wang Dr. Jiaqi Q. Li Prof. Dr. Yumei M. Xiao Prof. Dr. Bin Fu Prof. Dr. Zhaohai H. Qin 《ChemMedChem》2020,15(5):404-410
Mitochondrial oxidative damage and dysfunction contribute to a wide range of human diseases. Considering the limitation of conventional antioxidants and that mitochondria are the main source of reactive oxygen species (ROS) which induce oxidative damage, mitochondria-targeted antioxidants which can selectively block mitochondrial oxidative damage and prevent various types of cell death have been widely developed. As a lipophilic cation, triphenylphosphonium (TPP) has been commonly used in designing mitochondria-targeted antioxidants. Conjugated with the TPP moiety, antioxidants can achieve more than 1000-fold higher mitochondrial concentration depending on cell membrane potentials and mitochondrial membrane potentials. Herein we discuss the deficiencies of conventional antioxidants and the advantages of mitochondrial targeting, and review various types of TPP-based mitochondria-targeted antioxidants. These provide theoretical and background support for the design of new anti-oxidant. 相似文献
68.
69.
V. I. Zubkov O. V. Kucherova I. N. Yakovlev A. V. Solomonov 《Russian Microelectronics》2015,44(3):203-209
An automated system for integrated electrophysical and optical studies of semiconductor nanoheterostructures, which operates in a wide temperature range from 15 to 475 K, is designed. The setup is intended to measure the temperature and frequency admittance and electroluminescence spectra of light-emitting diode and laser chips formed on substrates of diameter up to 50.2 mm, and the distribution of parameters over the wafer. The setup includes the closed-cycle helium cryogenic station, LCR meter, and temperature controller. The characterization results of nanoheterostructures with InGaN/GaN multiple quantum wells, which are used for creating highly efficient white and blue light-emitting diodes, are presented. 相似文献
70.