全文获取类型
收费全文 | 19646篇 |
免费 | 965篇 |
国内免费 | 141篇 |
专业分类
电工技术 | 329篇 |
综合类 | 33篇 |
化学工业 | 4412篇 |
金属工艺 | 603篇 |
机械仪表 | 646篇 |
建筑科学 | 398篇 |
矿业工程 | 48篇 |
能源动力 | 1404篇 |
轻工业 | 1211篇 |
水利工程 | 152篇 |
石油天然气 | 96篇 |
武器工业 | 1篇 |
无线电 | 2409篇 |
一般工业技术 | 4482篇 |
冶金工业 | 1469篇 |
原子能技术 | 181篇 |
自动化技术 | 2878篇 |
出版年
2024年 | 103篇 |
2023年 | 427篇 |
2022年 | 1018篇 |
2021年 | 1183篇 |
2020年 | 926篇 |
2019年 | 955篇 |
2018年 | 1247篇 |
2017年 | 986篇 |
2016年 | 957篇 |
2015年 | 614篇 |
2014年 | 856篇 |
2013年 | 1563篇 |
2012年 | 923篇 |
2011年 | 1114篇 |
2010年 | 900篇 |
2009年 | 850篇 |
2008年 | 757篇 |
2007年 | 606篇 |
2006年 | 501篇 |
2005年 | 386篇 |
2004年 | 294篇 |
2003年 | 255篇 |
2002年 | 199篇 |
2001年 | 189篇 |
2000年 | 173篇 |
1999年 | 174篇 |
1998年 | 296篇 |
1997年 | 247篇 |
1996年 | 222篇 |
1995年 | 177篇 |
1994年 | 160篇 |
1993年 | 162篇 |
1992年 | 106篇 |
1991年 | 134篇 |
1990年 | 101篇 |
1989年 | 103篇 |
1988年 | 83篇 |
1987年 | 93篇 |
1986年 | 79篇 |
1985年 | 90篇 |
1984年 | 79篇 |
1983年 | 71篇 |
1982年 | 64篇 |
1981年 | 70篇 |
1980年 | 50篇 |
1979年 | 35篇 |
1978年 | 30篇 |
1977年 | 26篇 |
1976年 | 35篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Kalai Selvan Ramalingam Karmegam Karuppiah Shiamala Devi Ramaiya Vivien How Enoch Kumar Perimal Hassan Sadeghi Naeini Sivasankar Sambasivam Kulanthayan KC Mani 《人机工程学与制造业中的人性因素》2019,29(5):426-434
Many occupations require workers to stand for long periods of time without proper interventions, which causes discomfort in the back and lower limbs. Therefore, this study aims to assess the effectiveness in alleviating body muscle discomfort during prolonged standing through the use of a calf massager. This study was conducted among male workers at a manufacturer with production line workers and the list was obtained from the HR Department and simple random sampling was done by number categorization. A total of 100 respondents (50 respondents for both the control and the experimental groups) participated in this study. The experiment took place in a room with a similar setup for the production line. Each respondent was requested to perform the simulated task for 2 hr. For the experimental group, the calf massager was turned on every 15 min. At every 15‐min interval after turning on the calf massager, respondents from both groups were required to evaluate their discomfort level on a Borg's scale CR‐10 questionnaire. The results showed that the level of body discomfort among respondents in the experimental group reduced (20–30%) compared with that of the control group. Multivariate analysis results revealed that the discomfort rating for the lower back, knees, thighs, calves, and feet was significantly lower (p < .05) among the experimental group compared with the control group. For lower body parts, the lower back region was statistically significant (p < .05) at the 90th, 105th, and 120th min; the thigh region was statistically significant (p < .05) at the 120th min; the knee region was statistically significant (p < .05) at the 105th and 120th min; the calf region was statistically significant (p < .05) at all minute intervals except the 15th and 45th min, while the feet region, was statistically significant at the 105th and 120th min. Therefore, this study indicates that calf massage treatment is capable of reducing body muscle discomfort during prolonged standing and highlights the significance of calf massage. 相似文献
43.
44.
45.
46.
Kumari Asha Neeraj Kumar Biswas Sakshi Saxena Vibha Rani Satsangi Rohit Shrivastav Rama Kant Sahab Dass 《International Journal of Hydrogen Energy》2021,46(40):20858-20870
The present study attempts quantitative determination of changes in the morphological surface features viz. fractal dimension, lower and upper cut off length scale through Power Spectral Density analysis prior to and after irradiation of 100 KeV Ar+ ion beam at incidence angles of 0°, 40° and 60° on ZnO thin films. All the unirradiated and irradiated samples are subjected to photoelectrochemical characterization and a correlation between photoelectrochemical performance and morphological parameters is established. Sample irradiated at 40° angle at the fluence of 5 × 1016 ions/cm2 is found to possess maximum fractal dimension of 2.72, lower and upper cut off length scale of 3.16 nm and 63.00 nm respectively. This sample exhibits maximum photocurrent density of 3.19 mA/cm2 and applied bias photon-to-current efficiency of 1.12% at 1.23 V/RHE. Hydrogen gas collected for duration of 1 h for the same sample was ~4.83 mLcm?2. 相似文献
47.
Thakur Divyansh Kumar Yugal Kumar Arvind Singh Pradeep Kumar 《Wireless Personal Communications》2019,104(1):471-489
Wireless Personal Communications - Data security is currently become a serious concern in wireless communication system for both the users and providers. Without a secure medium, the data... 相似文献
48.
Jagadeesh Babu Sriramoju Murthy Muniyappa Navya Rani Marilingaiah Chetana Sabbanahalli Manjunath Shetty Ravi Mudike Chitrabanu C.P Prasanna D. Shivaramu Nagaraju G Kanchugarakoppal S. Rangappa Ananda Kumar C.S Dinesh Rangappa 《Ceramics International》2021,47(7):10314-10321
Application of brown titanium dioxide (TiO2-x) and its modified composite forms in the photocatalytic decomposition of organic pollutants in the environment is a promising way to provide solutions for environmental redemption. Herein, we report the synthesis of effective and stable TiO2-x nanoparticles with g-C3N4, RGO, and multiwalled carbon nanotubes (CNTs) using a simple hydrothermal method. Among all the as-synthesized samples, excellent photocatalytic degradation activity was observed for RGO-TiO2-x nanocomposite with high rate constants of 0.075 min?1, 0.083 min?1 and 0.093 min?1 for methylene blue, rhodamine-B, and rosebengal dyes under UV–Visible light irradiation, respectively. The altered bandgap (1.8 eV) and the large surface area of RGO-TiO2-x nanocomposite impacts on both absorption of visible light and efficiency of photogenerated charge electron (e?)/hole (h+) pair separation. This resulted in enhanced photocatalytic property of carbon-based TiO2-x nanocomposites. A systematic study on the influence of different carbon nanostructures on the photocatalytic activity of brown TiO2-x is carried out. 相似文献
49.
Wireless Networks - A novel approach is proposed to detect protocol misbehavior using state-of-the-art machine learning frameworks and entropy. Nodes in Vehicular Ad Hoc Networks (VANETs) use... 相似文献
50.
Manika Chaudhary Milan Singh Ashwani Kumar Yogendra K. Gautam Anil K. Malik Yogesh Kumar Beer Pal Singh 《Ceramics International》2021,47(2):2094-2106
The current research work presents a facile and cost–effective co-precipitation method to prepare doped (Co & Fe) CuO and undoped CuO nanostructures without usage of any type of surfactant or capping agents. The structural analysis reveals monoclinic crystal structure of synthesized pure CuO and doped-CuO nanostructures. The effect of different morphologies on the performance of supercapacitors has been found in CV (cyclic voltammetry) and GCD (galvanic charge discharge) investigations. The specific capacitances have been obtained 156 (±5) Fg?1, 168(±5) Fg?1 and 186 (±5) Fg?1 for CuO, Co-doped CuO and Fe-doped CuO electrodes, respectively at scan rate of 5 mVs?1, while it is found to be 114 (±5) Fg?1, 136 (±5) Fg?1 and 170 (±5) Fg?1 for CuO, Co–CuO and Fe–CuO, respectively at 0.5 Ag-1 as calculated from the GCD. The super capacitive performance of the Fe–CuO nanorods is mainly attributed to the synergism that evolves between CuO and Fe metal ion. The Fe-doped CuO with its nanorods like morphology provides superior specific capacitance value and excellent cyclic stability among all studied nanostructured electrodes. Consequently, it motivates to the use of Fe-doped CuO nanostructures as electrode material in the next generation energy storage devices. 相似文献