全文获取类型
收费全文 | 184676篇 |
免费 | 1762篇 |
国内免费 | 1297篇 |
专业分类
电工技术 | 3986篇 |
综合类 | 229篇 |
化学工业 | 21338篇 |
金属工艺 | 12494篇 |
机械仪表 | 9220篇 |
建筑科学 | 3501篇 |
矿业工程 | 968篇 |
能源动力 | 3734篇 |
轻工业 | 7523篇 |
水利工程 | 1855篇 |
石油天然气 | 2213篇 |
武器工业 | 15篇 |
无线电 | 23577篇 |
一般工业技术 | 42976篇 |
冶金工业 | 31998篇 |
原子能技术 | 2651篇 |
自动化技术 | 19457篇 |
出版年
2022年 | 501篇 |
2021年 | 792篇 |
2020年 | 560篇 |
2019年 | 730篇 |
2018年 | 10192篇 |
2017年 | 10813篇 |
2016年 | 6251篇 |
2015年 | 1549篇 |
2014年 | 1655篇 |
2013年 | 4887篇 |
2012年 | 5522篇 |
2011年 | 12880篇 |
2010年 | 11725篇 |
2009年 | 11095篇 |
2008年 | 10961篇 |
2007年 | 13345篇 |
2006年 | 3896篇 |
2005年 | 7338篇 |
2004年 | 5394篇 |
2003年 | 4840篇 |
2002年 | 3421篇 |
2001年 | 3118篇 |
2000年 | 2918篇 |
1999年 | 3177篇 |
1998年 | 9709篇 |
1997年 | 6324篇 |
1996年 | 4893篇 |
1995年 | 3264篇 |
1994年 | 2905篇 |
1993年 | 2824篇 |
1992年 | 1702篇 |
1991年 | 1678篇 |
1990年 | 1563篇 |
1989年 | 1375篇 |
1988年 | 1211篇 |
1987年 | 899篇 |
1986年 | 938篇 |
1985年 | 965篇 |
1984年 | 847篇 |
1983年 | 730篇 |
1982年 | 731篇 |
1981年 | 716篇 |
1980年 | 602篇 |
1979年 | 503篇 |
1978年 | 439篇 |
1977年 | 557篇 |
1976年 | 1010篇 |
1975年 | 313篇 |
1974年 | 288篇 |
1973年 | 268篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
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
24.
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
25.
26.
A method for estimating the sway angle using an observer has already been proposed. The state observer estimates the sway angle accurately and must use the detected sway angle value. However, the estimated sway angle has an error owing to rope length error, friction force, and wind. Moreover, the container mass cannot be determined, and therefore the observer parameter is not suitable. We already proposed robust antisway control for overcoming rope length error without adding a new sensor. Further, we designed a friction disturbance observer to cancel out the influence of the friction force. In this paper, we first propose a container mass estimation method when a crane system performs rolling up control. The observer parameter can be selected using the estimated mass value. Second, in crane parallel shift control, we propose a robust antisway control even when there is a wind disturbance. We design a wind disturbance observer and propose a wind disturbance estimator to separate the friction observer output from the wind disturbance observer output. We confirm through experiments that the proposed method can reduce vibration. 相似文献
27.
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
28.
I. N. Andronov Yu. I. Ryabkov N. P. Bogdanov N. A. Severova A. N. Danilov I. V. Churilina 《Russian Metallurgy (Metally)》2015,2015(10):778-784
The influence of the thermal cycling conditions on the thermal-cycling creep of a TN-1 alloy and the related irreversible deformations is studied. The conditions under which an anomalous increase in the irreversible deformations begins are determined. The structural mechanism of the irreversible deformations of an equiatomic alloy is shown to be analogous to the structural mechanism of metal creep at high temperatures: it predominantly has a dislocation character. It is proposed to use the effect of anomalous increase in the deformation of materials with reversible martensitic transformations for forming parts made of these materials at low temperatures. 相似文献
29.
Tomoya Suzuki Kento Shiota Yu-ichiro Izato Masahiro Komori Koichi Sato Yasuyuki Takai Takayuki Ninomiya Atsumi Miyake 《International Journal of Hydrogen Energy》2021,46(11):8329-8343
Although hydrogen refueling stations (HRSs) are becoming widespread across Japan and are essential for the operation of fuel cell vehicles, they present potential hazards. A large number of accidents such as explosions or fires have been reported, rendering it necessary to conduct a number of qualitative and quantitative risk assessments for HRSs. Current safety codes and technical standards related to Japanese HRSs have been established based on the results of a qualitative risk assessment and quantitative effectiveness validation of safety measures over ten years ago. In the last decade, there has been much development in the technologies of the components or facilities used in domestic HRSs and much operational experience as well as knowledge to use hydrogen in HRSs safely have been gained through years of commercial operation. The purpose of the present study is to conduct a quantitative risk assessment (QRA) of the latest HRS model representing Japanese HRSs with the most current information and to identify the most significant scenarios that pose the greatest risks to the physical surroundings in the HRS model. The results of the QRA show that the risk contours of 10?3 and 10?4 per year were confined within the HRS boundaries, whereas the risk contours of 10?5 and 10?6 per year are still present outside the HRS. Comparing the breakdown of the individual risks (IRs) at the risk ranking points, we conclude that the risk of jet fire demonstrates the highest contribution to the risks at all of the risk ranking points and outside the station. To reduce these risks and confine the risk contour of 10?6 per year within the HRS boundaries, it is necessary to consider risk mitigation measures for jet fires. 相似文献
30.
Spinel LiSr0·1Cr0·1Mn1·8O4 was synthesised by high temperature solid state method in order to enhance the electrochemical performance. The LiSr0·1Cr0·1Mn1·8O4 (LSCMO) materials were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. The XRD and SEM studies confirm that LSCMO had spinel crystal structure with a space group of Fd3m, and the particle of LSCMO shows irregular shape. The cyclic voltammetry data illustrated that the heavy current charge–discharge performance of LMO was improved by Sr2+ and Cr3+ doping. The galvanostatic charge–discharge of LSCMO cathode materials was measured at 1, 5, 10 and 20 C. The results indicated that LSCMO improved the capacity retention. 相似文献