全文获取类型
收费全文 | 21658篇 |
免费 | 1322篇 |
国内免费 | 56篇 |
专业分类
电工技术 | 311篇 |
综合类 | 25篇 |
化学工业 | 4792篇 |
金属工艺 | 882篇 |
机械仪表 | 1301篇 |
建筑科学 | 426篇 |
矿业工程 | 7篇 |
能源动力 | 865篇 |
轻工业 | 1851篇 |
水利工程 | 91篇 |
石油天然气 | 16篇 |
无线电 | 3651篇 |
一般工业技术 | 4629篇 |
冶金工业 | 1541篇 |
原子能技术 | 292篇 |
自动化技术 | 2356篇 |
出版年
2024年 | 11篇 |
2023年 | 264篇 |
2022年 | 304篇 |
2021年 | 685篇 |
2020年 | 470篇 |
2019年 | 496篇 |
2018年 | 699篇 |
2017年 | 661篇 |
2016年 | 768篇 |
2015年 | 602篇 |
2014年 | 939篇 |
2013年 | 1390篇 |
2012年 | 1459篇 |
2011年 | 1791篇 |
2010年 | 1300篇 |
2009年 | 1332篇 |
2008年 | 1213篇 |
2007年 | 940篇 |
2006年 | 813篇 |
2005年 | 708篇 |
2004年 | 638篇 |
2003年 | 589篇 |
2002年 | 594篇 |
2001年 | 517篇 |
2000年 | 437篇 |
1999年 | 423篇 |
1998年 | 709篇 |
1997年 | 420篇 |
1996年 | 396篇 |
1995年 | 257篇 |
1994年 | 169篇 |
1993年 | 151篇 |
1992年 | 113篇 |
1991年 | 100篇 |
1990年 | 75篇 |
1989年 | 88篇 |
1988年 | 74篇 |
1987年 | 63篇 |
1986年 | 51篇 |
1985年 | 43篇 |
1984年 | 36篇 |
1983年 | 28篇 |
1982年 | 31篇 |
1981年 | 26篇 |
1980年 | 29篇 |
1979年 | 13篇 |
1977年 | 22篇 |
1976年 | 33篇 |
1975年 | 17篇 |
1974年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
861.
Hyun Soon Park Yasukazu Murakami Keiichi Yanagisawa Tsuyoshi Matsuda Ryosuke Kainuma Daisuke Shindo Akira Tonomura 《Advanced functional materials》2012,22(16):3434-3437
Peculiar magnetic domain walls produced in Heusler alloys, which have attracted renewed interest due to their potential application to actuators and spintronic devices, are studied here using electron holography. The observations reveal unexpectedly narrow magnetic domain walls, the width of which showed perfect agreement with that of the antiphase boundaries (APB, e.g., only 3 nm). While the results can be explained by the significant depression of ferromagnetism due to the local chemical disorder, the electron phase shift indicates that ferromagnetic correlation still remains in the APB region. 相似文献
862.
Various expert system development approaches were proposed but most of them cannot deal with two problems: the difficulty of analysis and maintenance. Rather than to spend time waiting any longer, it is better to find an alternative solution from other research fields. In computer software development area, researchers have been suffering from the difficulty of maintenance and analysis, just as the researchers in the expert system development field. To solve this issue, researchers in the software used both agile software development and business rules approach: agile software development is for overcoming the the difficulty of analysis, and business rules approach is for reducing issues in the maintenance. There is a big opportunity that those two approaches can also be solve the two issues in the expert system development field. The paper describes requirements of the approach based on agile software development and the business rules approach. As a result, we consider and specify why the Multiple Classification Ripple Down Rules is the novel approach for the expert system development. 相似文献
863.
Influencing quality factors, related to the user and system, need to be considered when building a well-designed multimodal interaction system. User groups, access to input modes and tasks were defined as the user and system factors to examine effective factors of multimodal interaction with a smart TV, and its input modes consisted of voice, arrow key, and motion-based pointer modes and their combinations. User group 1 had experience of multimodal interaction with another device, while user group 2 had only experience of unimodal interaction. In addition, the sequential/simultaneous input modes and simple/complex tasks were considered as the system factors. Depending on the task complexity, two experiments were conducted. Nine input modes (three unimodes and six multimodes), sequentially and simultaneously given to both user groups, were investigated for the simple task of menu traversal and the complex task of manipulating broadcasting content, menu traversal, and web content navigation. A subjective rating of the level of preference was recorded in the sequential input mode using a modified Likert-type rating scale, while each participant’s preferred mode was observed in the simultaneous scenario. Additionally, the completion time and error rate were measured in both experiments. When performing the simple task, user group 1 used multimodes more so than group 2. However, in the complex task, both user groups preferred multimodes when modes were simultaneously presented. Considering effective quality factors, input modes of a smart TV should be simultaneously provided with a voice and motion-based pointer multimode. 相似文献
864.
Jinsun Yoon Hong-kyu Song Sungjin Park Jongok Won Yong Soo Kang 《Polymer Bulletin》2014,71(8):2053-2065
We have investigated the effects of localized surface plasmons (LSPs) on the performance of quasi-solid-state dye-sensitized solar cells (DSSCs). Ag and Au nanoparticles (NPs) were prepared by photoreduction in the presence of generation 5 polyester hydroxyl acetylene bis(hydroxymethyl)propanoic acid dendrons (Dendron) as a stabilizer. The plasmon-enhanced DSSCs were achieved by incorporating metal@Dendron NPs into TiO2 photoanodes. The presence of dendrons prevents the photoelectrons from recombining on the surface of TiO2 semiconductor and improves the stability of metal NPs. With the addition of Ag@Dendron NPs, the photocurrent and the power conversion efficiency of quasi-solid-state DSSCs increased due to the LSP effect of metal NPs and the barrier effect of dendron, which were confirmed by the increased incident photon-to-photocurrent efficiency and by electrochemical impedance spectroscopy analysis. 相似文献
865.
Communication technologies have been hailed as having a potential to promote democracy and freedom, and this paper aims to examine these claims in a comparative, international context. Our analysis focuses on the mediating role of horizontal communication networks (i.e., telephone, mobile telephone and the Internet) in the relationship between culture and political development. Using cultural value indicators of the World Values Survey and the measures of communication technology development, this study tests the mediating path from culture to communication technologies and to political development. The results suggest that cultural values have a role in shaping the structural characteristics of horizontal networks such as accessibility and decentralization, and that these features of horizontal networks are positively related to institutional and effective democracy as well as to economic competitiveness of nations. 相似文献
866.
Huiyoun Shin Dongseon Jang Youngil Jang Myungju Cho Kyuho Park 《Journal of Materials Science: Materials in Electronics》2013,24(10):3744-3748
CdSe/ZnS core–shell structured nano-crystal quantum dots (QDs) are ideal candidates for light-emission applications due to their high quantum efficiency, narrow-band, and particle-size-tunable photoluminescence. In particular, their small size results in the quantum confinement of semiconductor nano-crystals, which widens their energy gaps. In general, high resolution imaging analyses of QDs using a transmission electron microscope are very difficult due to their significantly small size. Successful imaging depends on the capabilities of TEM equipment and the contrast of the QDs sample relative to the supporting film. In this work, all imaging analyses were performed on a TEM equipped with a probe Cs corrector. The samples for observing QDs were prepared by drying each QDs solution on a lacey carbon Cu (300 mesh) grid previously coated with an ultra-thin graphene monolayer (thickness = 0.3 nm), due to the need to minimize the effect of the supported film. 相似文献
867.
868.
869.
Park Ji-Woo Ku Tae-Wan Kim Jeong Kim Kwang-Ho Kang Beom-Soo 《Journal of Mechanical Science and Technology》2016,30(5):2203-2210
Journal of Mechanical Science and Technology - Flexible forming technology such as Multi-point dieless forming (MDF) has benefits for the sheet metal field because it can implement a variety of... 相似文献
870.
Junghun Kim Sangkyu Park Heecheon Cho Junsang Kim Jae Young Choi 《Telematics and Informatics》2017,34(2):540-547
South Korea has the highest expenditure on telecommunications among OECD countries, drawing national attention to the issue of reducing high prices. In response, the Korean government enacted the Mobile Device Distribution Improvement (MDDI) Act to eliminate information asymmetry by limiting mobile carriers’ mobile handset subsidies to consumers. This study examined factors affecting public trust in the MDDI based by analyzing responses to a questionnaire survey using the ordered probit model. The results show that the knowledge, expectations, and perceived effects of the MDDI have a meaningful effect on public trust in the policy. The results of this study confirm that it is essential for governments to promote their policies by continuously educating the public, especially in this case because the policy has a direct effect on telecommunications expenditures. 相似文献