全文获取类型
收费全文 | 7204篇 |
免费 | 386篇 |
国内免费 | 70篇 |
专业分类
电工技术 | 120篇 |
综合类 | 64篇 |
化学工业 | 1325篇 |
金属工艺 | 299篇 |
机械仪表 | 346篇 |
建筑科学 | 173篇 |
矿业工程 | 33篇 |
能源动力 | 306篇 |
轻工业 | 539篇 |
水利工程 | 57篇 |
石油天然气 | 35篇 |
武器工业 | 7篇 |
无线电 | 1450篇 |
一般工业技术 | 1364篇 |
冶金工业 | 563篇 |
原子能技术 | 109篇 |
自动化技术 | 870篇 |
出版年
2024年 | 8篇 |
2023年 | 79篇 |
2022年 | 124篇 |
2021年 | 203篇 |
2020年 | 125篇 |
2019年 | 150篇 |
2018年 | 191篇 |
2017年 | 191篇 |
2016年 | 225篇 |
2015年 | 194篇 |
2014年 | 276篇 |
2013年 | 515篇 |
2012年 | 436篇 |
2011年 | 536篇 |
2010年 | 369篇 |
2009年 | 423篇 |
2008年 | 372篇 |
2007年 | 306篇 |
2006年 | 270篇 |
2005年 | 275篇 |
2004年 | 190篇 |
2003年 | 217篇 |
2002年 | 192篇 |
2001年 | 139篇 |
2000年 | 146篇 |
1999年 | 135篇 |
1998年 | 259篇 |
1997年 | 149篇 |
1996年 | 152篇 |
1995年 | 130篇 |
1994年 | 92篇 |
1993年 | 92篇 |
1992年 | 67篇 |
1991年 | 56篇 |
1990年 | 51篇 |
1989年 | 48篇 |
1988年 | 32篇 |
1987年 | 32篇 |
1986年 | 24篇 |
1985年 | 24篇 |
1984年 | 23篇 |
1983年 | 19篇 |
1982年 | 22篇 |
1981年 | 13篇 |
1980年 | 17篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 13篇 |
1975年 | 9篇 |
排序方式: 共有7660条查询结果,搜索用时 0 毫秒
991.
Man Chang Tae-Wook Kim Joonmyoung Lee Minseok Jo Seonghyun Kim Seungjae Jung Hyejung Choi Takhee Lee Hyunsang Hwang 《Microelectronic Engineering》2009,86(7-9):1804-1806
We investigated the impact of charge injection and metal gates (Al and Pt) on the data retention characteristics of metal–alumina–nitride–oxide–silicon (MANOS) devices for NAND flash memory application. Through the theoretical and experimental results, the highly injected charge (ΔVTH) could cause the band bending of Al2O3, which reduced the tunneling distance across Al2O3. Thus, the dominant charge loss path is not only toward SiO2 but also toward Al2O3 direction. Compared to low-metal work function (ФM), ONA stack with high-ФM showed better data retention characteristics, even if ΔVTH is high. This could be explained by Fermi level alignment for different ФM, which results in the reduction of electric field across the Al2O3 compensated by the ΔФM (ФPt ? ФAl). 相似文献
992.
Joobong Hyun Dong‐Choon Hwang Dong‐Hak Shin Byung‐Gook Lee Eun‐Soo Kim 《ETRI Journal》2009,31(2):105-110
In this paper, we propose a curved projection integral imaging system to improve the horizontal and vertical viewing angles. The proposed system can be easily implemented by additional use of a large‐aperture convex lens in conventional projection integral imaging. To obtain the simultaneous display of 3D images through real and virtual image fields, we propose a computer‐generated pickup method based on ray optics and elemental images, which are synthesized for the proposed system. To show the feasibility of the proposed system, preliminary experiments are carried out. Experimental results indicate that our system improves the viewing angle and displays 3D images simultaneously in real and virtual image fields. 相似文献
993.
Ren‐Hung Hwang Cheng‐Chang Hoh Chiung‐Ying Wang 《Wireless Communications and Mobile Computing》2010,10(7):875-887
As digital devices with communication capability become more pervasive, we are entering the era of ubiquitous computing, as predicted by Mark Weiser. In ubiquitous environments, distributed context management servers are deployed everywhere to provide information and computing resources for users anytime and anywhere. Smart handheld computing devices with context‐aware applications may retrieve context information from the nearest server. This study investigates the problem of routing packets to the nearest server in a ubiquitous environment. An anycast routing protocol based on swarm intelligence, referred to as ARPSI, is proposed to route packets dynamically to a nearby server in a mobile, ad hoc, wireless network. Based on swarm intelligence, ARPSI is able to find a short path to a neighboring server efficiently and quickly. Simulations are conducted to evaluate the performance of ARPSI and our simulation results show that ARPSI achieves a higher packet delivery ratio, shorter routing path to anycast servers, and lower control packet overhead than the AODV‐based anycast protocol (A‐AODV) protocol. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
994.
Tsung-Han Ho Hann-Jang Hwang Jeng-Yueh Shieh Ming-Chin Chung 《Reactive and Functional Polymers》2009,69(3):176-182
Two phosphorus-containing advanced epoxy resins were obtained by chain-extension of diglycidyl ether of bisphenol-A epoxy (DGEBA) resin with 2-(6-oxido-6H-dibenz(c,e)(1,2)-oxaphosphorin-6-yl)-1,4-benzenediol (DOPOBQ), at different stoichiometric ratios. The phosphorus-containing advanced epoxy was separately cured with various dicyanate esters to form flame-retardant epoxy/cyanate ester systems. The effects of phosphorus content and dicyanate ester structure were studied, and compared with those of the control (advanced bisphenol-A epoxy) system. The DOPOBQ-containing epoxy/cyanate ester systems exhibited higher glass transition temperatures, better dimensional stability and better thermal stability. 相似文献
995.
A field study conducted in workplaces and residences in Taiwan is carried out to clarify two questions in detail: (1) do people in the tropical climate regions demonstrate a correlation between thermal sensation and thermal dissatisfaction the same as the PMV–PPD formula in the ISO 7730; and (2) does the difference in opportunities to choose from a variety of methods to achieve thermal comfort affects thermal perceptions of occupants? A new predicted formula of percentage of dissatisfied (PD) relating to mean thermal sensation votes (TSVs) is proposed for hot and humid regions. Besides an increase in minimum rate of dissatisfied from 5% to 9%, a shift of the TSV with minimum PD to the cool side of sensation scale is suggested by the new proposed formula. It also reveals that the limits of TSV corresponding to 80% acceptability for hot and humid regions are −1.45 and +0.65 rather than −0.85 and +0.85 suggested by ISO 7730. It is revealed in the findings that the effectiveness, availability and cost of a thermal adaptation method can affect the interviewees' thermal adaptation behaviour. According to the discussion of interviewees' idea about the trade-off between thermal comfort and energy saving, it is found that an energy-saving approach at the cost of sacrificing occupant's thermal comfort is difficult to set into action, but those ensure the occupant's comfort are more acceptable and can be easily popularized. 相似文献
996.
997.
Ha Soo Hwang Jae Hyun Bae In Park Jong Myung Park Kwon Taek Lim 《The Journal of Supercritical Fluids》2009,50(3):292-296
Amine functional polymeric spheres were prepared via the dispersion polymerization of 2-dimethylaminoethyl methacrylate and methylmethacrylate in supercritical carbon dioxide, and they were employed efficiently as templates for the fabrication of hollow silica particles. A small amount of divinyl benzene was used as a crosslinking agent to control the morphology of the copolymeric particles from clumpy solid to spherical shape. The assembly of the polymeric spheres with tetraethylorthosilicate (TEOS) through hydrothermal methods produced core-shell type hybrid particles. The whole process required neither surface treatment for the polymeric particles nor addition of any acidic or basic catalyst for the hydrolysis of silica precursor because dimethylamino groups of the copolymeric spheres were able to absorb water and catalyze the hydrolysis of TEOS for the deposition of the silica gel network. The polymeric cores were completely removed by calcination process and silica hollow particles with well-defined structure were obtained finally. The silica hollow particles were characterized by scanning electron microscopy and transmission electron microscopy, which clearly revealed that the silica spheres had the hollow structure with 151 nm wall thickness. 相似文献
998.
Sung‐Kyung Lee Sang‐Hyun Lee Kyung‐Won Min Byoung‐Wook Moon Kyung‐Jo Youn Jae‐Seung Hwang 《The Structural Design of Tall and Special Buildings》2009,18(1):105-115
Since the force generated by a magneto‐rheological (MR) damper has large nonlinearity, the performance of an MR damper is dependent on response characteristics such as frequency and amplitude. Soil–structure interaction (SSI) is generally known to have a large effect on the seismic response of a building structure. In this study, the performance of an MR damper in mitigating the seismic response of a building structure is evaluated considering the SSI effects. First, the performance variance of an MR damper due to the change of the structural natural period is investigated by constructing its normalized response spectrum through the numerical analysis of many earthquake wave records and the natural period of a structure. The variable friction force of an MR damper is normalized by the structural base shear force, and its amplitude and decrement of response are quantitatively evaluated. Then, the response characteristics of the SSI system due to the lengthening of the structural natural period and various soil conditions are numerically evaluated based on the response spectrum analysis. Finally, the numerical results with and without considering the SSI effects are comparatively evaluated for the building structure with an MR damper. The comparison results show that the SSI effect should be considered in order that the undesirable effect of an MR damper on the structural control would not be neglected. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
999.
夯扩桩扩大头直径计算的试验研究 总被引:7,自引:1,他引:7
在人工均匀填筑的平潭标准砂中,针对不同密度,分别进行夯扩桩半模夯扩试验,生动地展示了扩大头的形成过程,其最终形状近似为椭球体,在此基础上,定义分项系数Fc和Fr,提出了扩大头计算直径的修正公式,此公式经兄弟单位全模试验及现场试验成果的检验表明,它比应用其他文献中的公式,计算结果更接近于实测值。 相似文献
1000.