全文获取类型
收费全文 | 4826篇 |
免费 | 354篇 |
国内免费 | 32篇 |
专业分类
电工技术 | 84篇 |
综合类 | 25篇 |
化学工业 | 1343篇 |
金属工艺 | 166篇 |
机械仪表 | 251篇 |
建筑科学 | 177篇 |
矿业工程 | 13篇 |
能源动力 | 264篇 |
轻工业 | 378篇 |
水利工程 | 110篇 |
石油天然气 | 71篇 |
武器工业 | 3篇 |
无线电 | 398篇 |
一般工业技术 | 825篇 |
冶金工业 | 164篇 |
原子能技术 | 36篇 |
自动化技术 | 904篇 |
出版年
2024年 | 17篇 |
2023年 | 69篇 |
2022年 | 101篇 |
2021年 | 237篇 |
2020年 | 267篇 |
2019年 | 319篇 |
2018年 | 418篇 |
2017年 | 365篇 |
2016年 | 329篇 |
2015年 | 208篇 |
2014年 | 366篇 |
2013年 | 584篇 |
2012年 | 397篇 |
2011年 | 412篇 |
2010年 | 261篇 |
2009年 | 251篇 |
2008年 | 137篇 |
2007年 | 117篇 |
2006年 | 79篇 |
2005年 | 42篇 |
2004年 | 40篇 |
2003年 | 26篇 |
2002年 | 26篇 |
2001年 | 13篇 |
2000年 | 17篇 |
1999年 | 21篇 |
1998年 | 9篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1995年 | 14篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1984年 | 6篇 |
1982年 | 5篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有5212条查询结果,搜索用时 15 毫秒
101.
Reza Shokrani Hossein Ajamein Mozaffar Abdollahifar 《Particulate Science and Technology》2018,36(2):217-225
Fuel cell-grade hydrogen production has been studied via steam reforming of methanol (SRM) over a series of CuO/ZnO/Al2O3 nanocatalysts fabricated by the combustion method. The effect of sonication and urea/nitrate ratio on the characteristics and catalytic properties of the prepared catalysts has been investigated. The synthesized catalysts were characterized by x-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Particle Size Distribution (PSD), energy dispersive x-ray (EDX), Brunauer-Emmett-Teller (BET) and FTIR analyses XRD patterns showed positive influence of urea/nitrate ratio on CuO and ZnO crystallite sizes. The ultrasonic mixing of primary gel compared with conventional mixing led to lower crystallite size. FESEM images showed that the sample mixed by sonication with a urea/nitrate ratio of 1 had more homogeneous morphology with narrow particle size distribution. EDX results proved the presence of all metals on the surface of the nanocatalysts and better consistence between the gel and surface composition of elements in samples prepared by sonication. Catalytic performance showed that sonication during the mixing of primary gel dramatically increased the methanol conversion. It was also proved that increasing the amount of urea led to lower catalytic activity. The ultrasound-treated nanocatalyst with urea/nitrate?=?1 was the best sample in terms of activity and selectivity. It was stable in the SRM for 1200?min without considerable change in methanol conversion and product selectivity. 相似文献
102.
Multimedia Tools and Applications - Medical image fusion aims at preserving salient image features, reducing the redundancy, and increasing the interpretation quality of images in clinical... 相似文献
103.
Multimedia Tools and Applications - A new supervised feature extraction method appropriate for small sample size situations is proposed in this work. The proposed method is based on the first-order... 相似文献
104.
Postpartum depression (PPD) is a prevalent mood disorder estimated to affect 20%–40% of women worldwide after childbirth. In recent studies, the effect of vitamin D on prevention of mood disorders and depression has been investigated, but it is still unclear how vitamin D may affect PPD. The evidence on the relevance between vitamin D deficiency and PPD is inconsistent, and assessment of the recent literature has not previously been carried out. Moreover, there are few clinical studies on PPD and vitamin D supplementation. Five studies have so far assessed the relationship between the levels of vitamin D and PPD. Findings from cohort studies suggest that vitamin-D deficiency is related to the incidence of PPD and vitamin D may play a significant role in the recovery of women with PPD, but it is uncertain whether these actions are the effect of vitamin D on the function of hypothalamic-pituitary-adrenal (HPA) axis, the levels of estradiol, serotonin, pro-inflammatory cytokines, and/or of other mechanisms involved in PPD. 相似文献
105.
World Wide Web - Social networks are constantly expanding and attracting more and more users. The users of these networks share plenty of information with their friends, many of which are... 相似文献
106.
Ahmadi Hossein Arji Goli Shahmoradi Leila Safdari Reza Nilashi Mehrbakhsh Alizadeh Mojtaba 《Universal Access in the Information Society》2019,18(4):837-869
Universal Access in the Information Society - The Internet of Things (IoT) is an ecosystem that integrates physical objects, software and hardware to interact with each other. Aging of population,... 相似文献
107.
Mohammad Reza Taghizadeh Yazdi Mohammad Mahdi Mozaffari Seyed Mohammad Asadzadeh 《控制论与系统》2018,49(3):151-169
Workplace spirituality has gained attention as it is proven to be a contributor to organizational performance improvement. This paper aims to assess the impact of human resource spirituality on the success of organizational strategic change projects. The success of the projects is measured by the well-known criterion of deviation from the planned budget cost. Data collection is based on a questionnaire survey of 252 personnel in 36 large and medium-scale organizational change projects in power industry. The paper proposes an integrated algorithm of fuzzy data envelopment analysis (FDEA) and adaptive network-based fuzzy inference system (ANFIS) for measuring the pure effect of human resource spirituality on the success of organizational change projects in the power industry. It also achieves a verified tool capable of addressing complexity, nonlinearity, ambiguity, and fuzziness for measuring spirituality of human resources in the projects. Results show that spirituality of the project team has a significant effect on project success. 相似文献
108.
Microsystem Technologies - An alternative actuator for MEMS/NEMS device is proposed and analyzed. The actuator is based on the paired-wires (PW) carrying current concept, which makes the actuator... 相似文献
109.
Piri Reza Ghasemi Behrooz Yousefpour Mardali 《Metallurgical and Materials Transactions A》2018,49(3):938-945
Metallurgical and Materials Transactions A - In this study, samples with ferritic–bainitic dual phase structures consisting of 62 pct bainite were obtained from the AISI 4140 steel... 相似文献
110.
Mahmood Ghoranneviss Ahmad Salar Elahi Mojgan Tajdidzadeh Siamak Mohammadi Reza Arvin Mahgam Gheydi Ali Abbaspour Tehrani Fard 《Journal of Fusion Energy》2010,29(5):467-470
The first results of the movable electrode biasing experiments performed on the IR-T1 tokamak are presented. For this purpose,
a movable electrode biasing system was designed, constructed, and installed on the IR-T1 tokamak, and then the positive voltage
applied to an electrode inserted inside the tokamak limiter and the plasma current, poloidal and radial components of the
magnetic fields, loop voltage, and diamagnetic flux in the absence and presence of the biased electrode were measured. Results
compared and discussed. 相似文献