全文获取类型
收费全文 | 1267篇 |
免费 | 82篇 |
专业分类
电工技术 | 7篇 |
综合类 | 4篇 |
化学工业 | 443篇 |
金属工艺 | 12篇 |
机械仪表 | 22篇 |
建筑科学 | 53篇 |
能源动力 | 17篇 |
轻工业 | 162篇 |
水利工程 | 11篇 |
石油天然气 | 1篇 |
无线电 | 61篇 |
一般工业技术 | 208篇 |
冶金工业 | 210篇 |
自动化技术 | 138篇 |
出版年
2024年 | 1篇 |
2023年 | 23篇 |
2022年 | 71篇 |
2021年 | 93篇 |
2020年 | 45篇 |
2019年 | 45篇 |
2018年 | 35篇 |
2017年 | 42篇 |
2016年 | 36篇 |
2015年 | 51篇 |
2014年 | 38篇 |
2013年 | 70篇 |
2012年 | 80篇 |
2011年 | 100篇 |
2010年 | 75篇 |
2009年 | 67篇 |
2008年 | 82篇 |
2007年 | 69篇 |
2006年 | 55篇 |
2005年 | 34篇 |
2004年 | 39篇 |
2003年 | 35篇 |
2002年 | 26篇 |
2001年 | 23篇 |
2000年 | 16篇 |
1999年 | 11篇 |
1998年 | 18篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有1349条查询结果,搜索用时 0 毫秒
91.
92.
93.
This paper draws a state of the art of synthetic aperture radar (sar) data compression. Both raw data and synthesized image compression have been investigated. Compression of radar raw signal and sar image are considered separately since those two cases are specific. Also, Radar raw/image compression remains different from optical image compression and has to be considered with specific strategies that are adapted to the context. 相似文献
94.
Cherif M. Azzaz Luiz H. C. Mattoso Nicole R. Demarquette Ricardo J. Zednik 《应用聚合物科学杂志》2021,138(10):49959
Considerable effort has been devoted to improving the properties of PVDF (polyvinylidene fluoride), arguably the most technologically important piezoelectric polymer. Electrospinning has been found to be a particularly effective method of producing PVDF nanofibers with superior piezoelectric properties due to the resulting exceptionally high fraction of the piezoelectrically active crystalline β-phase. It is typically assumed that the high external electric fields applied during electrospinning enhance the formation of this β-phase, with the confused literature offering various unsatisfactory mechanistic explanations. However, by comparing PVDF nanofibers produced by two different processes (electrospinning and blowspinning), we show that the electric field is entirely unnecessary; indeed, the crystallization dynamics are principally driven by the applied mechanical stress, as evidenced by structurally identical 200 nm diameter PVDF fibers produced with and without external electric fields. 相似文献
95.
Nicole Basaraba Owen Conlan Jennifer Edmond Peter Arnds 《New Review of Hypermedia and Multimedia》2013,19(1-2):1-30
ABSTRACTGalleries, libraries, archives and museums (GLAMs) are increasingly using digital technologies for storytelling and creating mobile applications (apps) for cultural heritage content, but how apps are used in practice to communicate information to users has not been widely studied. A team of people from a heritage organisation, a university, and mobile app development group plan to create a bespoke heritage trail app for Ireland, but to date design conventions/recommendations for this genre are lacking. This article applies a systematic approach to digital narrative content analysis to better understand how apps are being used specifically for heritage trails with the aim of identifying what the common features are, which modalities and narrative techniques are used. The selected corpus included 55 apps downloaded from the Google Play Store. The results of this content analysis—based on the App Walkthrough Method (Light, B., Burgess, J., & Duguay, S. (2018). The walkthrough method: An approach to the study of apps. New Media & Society, 20(3), 881–900)—show that there is a gap between academic research themes/trends and how digital narrative is actually being communicated in the current market, and it aims to inform the future development of heritage trail apps by including a list of design and content features common to this genre. 相似文献
96.
97.
This paper reports early steps in research that seeks to clarify how publications of scientists interact dynamically with
citations and reputation in shaping the evolution of scientific fields. We assume that Lotka's modified law holds for scientific
fields. A primary approach to model publication productivity was published by Yablonsky. In contrast to Yablonsky's unfinished
mathematical approach, our simulation approach is not predominantly driven by insight into the formal generation mechanisms
of certain processes but more theory driven. It considers the evolution of publication and citation distributions over the
histories of scientific fields using both simulated and real historical data. 相似文献
98.
Nicole Schmidt 《Datenschutz und Datensicherheit - DuD》2009,33(2):107-109
Der BGH hat am 16.07.2008 (DuD 2008, 751) die Einwilligungsl?sung für die Zusendung von Werbung per Post, SMS oder E-Mail
von Unternehmen an Kunden im Zusammenhang mit der Kundenkarte Payback bewertet. Als Konsequenz ist nun der Gesetzgeber gefordert,
einen einheitlichen Einwilligungsstandard festzulegen. 相似文献
99.
Eric S. Toberer Alexandra Zevalkink Nicole Crisosto G. Jeffrey Snyder 《Advanced functional materials》2010,20(24):4375-4380
Understanding transport in Zintl compounds is important due to their unusual chemistry, structural complexity, and potential for good thermoelectric performance. Resistivity measurements indicate that undoped Ca5Al2Sb6 is a charge‐balanced semiconductor with a bandgap of 0.5 eV, consistent with Zintl–Klemm charge counting rules. Substituting divalent calcium with monovalent sodium leads to the formation of free holes, and a transition from insulating to metallic electronic behavior is observed. Seebeck measurements yield a hole mass of ~2me, consistent with a structure containing both ionic and covalent bonding. The structural complexity of Zintl compounds is implicated in their unusually low thermal conductivity values. Indeed, Ca5Al2Sb6 possesses an extremely low lattice thermal conductivity (0.6 W mK?1 at 850 K), which approaches the minimum thermal conductivity limit at high temperature. A single parabolic band model is developed and predicts that Ca4.75Na0.25Al2Sb6 possesses a near‐optimal carrier concentration for thermoelectric power generation. A maximum zT > 0.6 is obtained at 1000 K.Beyond thermoelectric applications, the semiconductor Ca5Al2Sb6 possesses a 1D covalent structure which should be amenable to interesting magnetic interactions when appropriately doped. 相似文献
100.
Why people benefit from e-learning differently: The effects of psychological processes on e-learning outcomes 总被引:1,自引:0,他引:1
Using social cognitive theory, we opened up the black box of psychological processes in which e-learners engage. We believed that prior experience with ICT and virtual competence were two influential factors that affected e-learning and had a positive influence on its outcomes. We tested our hypotheses on a sample of 383 Chinese students participating in online courses. Our findings confirmed the effect of virtual competence and revealed a nuanced mechanism by which experiences with ICT affected e-learning outcomes. We discussed the implications of this in e-learning practice. 相似文献