全文获取类型
收费全文 | 555篇 |
免费 | 31篇 |
专业分类
电工技术 | 25篇 |
化学工业 | 91篇 |
金属工艺 | 15篇 |
机械仪表 | 13篇 |
建筑科学 | 33篇 |
能源动力 | 9篇 |
轻工业 | 85篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 121篇 |
一般工业技术 | 83篇 |
冶金工业 | 68篇 |
原子能技术 | 4篇 |
自动化技术 | 36篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 13篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 14篇 |
2016年 | 15篇 |
2015年 | 20篇 |
2014年 | 25篇 |
2013年 | 31篇 |
2012年 | 27篇 |
2011年 | 25篇 |
2010年 | 20篇 |
2009年 | 29篇 |
2008年 | 36篇 |
2007年 | 23篇 |
2006年 | 24篇 |
2005年 | 21篇 |
2004年 | 26篇 |
2003年 | 24篇 |
2002年 | 16篇 |
2001年 | 12篇 |
2000年 | 16篇 |
1999年 | 20篇 |
1998年 | 29篇 |
1997年 | 20篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有586条查询结果,搜索用时 15 毫秒
91.
Prior studies of two series of segmented polyurethanes based on 2, 4 toluene cliisocyanate (2, 4 TDI) or 2, 8 TDI, butanediol, and a 1000 molecular weight polytetramethyleneoxide (PTMO-1000) soft segment revealed a rapid increase in soft segment glass transition temperature (Tg) with increasing urethane content in the 2, 4 TDI series. The change in Tg couldbe correlated with estimates of hard segment-soft segment phase mixing obtained by infrared analysis of the urethane NH and carbonyl bands. In the present paper, the infrared data have been reevaluated using improved procedures for resolving the carbonyl band into H-bonded and nonbonded components, and the relation between the estimated extent of phase mixing and Tg has been reexamined. The transition behavior in an extensive series of related polymers has also been determined, including 2, 4 TDI arid 2, 6 TDI samples with PTMO2000 as well as polybutyleneadipate (PBA-1000 and PBA-2000) soft segments. The results indicate the effectiveness, of increased soft segment molecular weight in promoting phase segregation, imply that much greater phase mixing occurs in polyester than polyether samples, suggest that anchoring the ends of the soft segments has only a small effect on Tg, and provide some evidence that H-bonding not only increases Tg but can also impede soft segment crystallization. 相似文献
92.
The aim of the present study is to investigate the ultimate strength characteristics of perforated steel plates under edge shear loading, which is a primary action type arising from cargo weight and water pressure in ships and ship-shaped offshore structures. The plates are considered to be simply supported along all (four) edges and kept straight. The cutout is circular and located at the center of the plate. A series of ANSYS nonlinear finite element analyses (FEA) are undertaken with varying the cutout size (diameter) as well as plate dimensions (plate aspect ratio and thickness). By the regression analysis of the FEA results obtained, a closed-form empirical formula for predicting the ultimate shear strength of perforated plates, which can be useful for first-cut strength estimations in reliability analyses or code calibrations, is derived. The accuracy of the ultimate strength formula developed is verified by a comparison with more refined nonlinear FEA results. 相似文献
93.
Jeom Kee Paik 《钢结构》2008,(4)
众所周知,与其他因素相比焊接引起的初始挠曲会极大地影响被焊板的极限强度,这意味着在计算板的极限强度以前判别板的初始挠曲性状是极其重要的。本文旨在研究海洋工程中应用的铝板在焊接过程中产生的初始挠曲特性。研究中共有78个单跨和多跨加劲平板铝结构,其与80m长全铝制高速船的基础结构同尺寸,采用金属惰性气体焊接。然后计算出加劲肋之间的初始挠曲。通过对数据库进行统计分析,得到初始挠曲变化系数。研究结果有助于焊接铝板结构的可靠性分析、极限强度确定和制作工艺控制。 相似文献
94.
Jeom Kee Paik 《钢结构》2008,23(9):81-81
铝夹芯结构非常适合于设计飞机、高速列车和快艇等轻型交通系统。研究目的主要是明确包含铝蜂窝状内芯的铝制夹芯板在理论和试验中的强度特性。对弯曲、轴压和侧向撞击荷载作用下的铝蜂窝夹芯板构件进行了一系列强度试验。在相应荷载作用下,运用简化理论分析蜂窝夹芯板的弯曲变形、屈曲/极限强度和破坏强度。同时也讨论了结构失效模式,并给出了试验数据。 相似文献
95.
Electrodes: Ferromagnetic,Folded Electrode Composite as a Soft Interface to the Skin for Long‐Term Electrophysiological Recording (Adv. Funct. Mater. 40/2016) 下载免费PDF全文
Kyung‐In Jang Han Na Jung Jung Woo Lee Sheng Xu Yu Hao Liu Yinji Ma Jae‐Woong Jeong Young Min Song Jeonghyun Kim Bong Hoon Kim Anthony Banks Jean Won Kwak Yiyuan Yang Dawei Shi Zijun Wei Xue Feng Ungyu Paik Yonggang Huang Roozbeh Ghaffari John A. Rogers 《Advanced functional materials》2016,26(40):7280-7280
96.
Eui-Hak Lee Hwan-Jun Choi Jong-Ho Paik Dong-Sun Kim Hyoung-Kyu Song 《Wireless Personal Communications》2016,88(4):1015-1025
In this paper, the hierarchical space time cyclic delay diversity (H-STCDD) scheme is proposed. Proposed scheme uses hierarchical modulation and achieves approximately full rate. It also uses a cyclic delay diversity scheme, which improves the benefit of channel coding particularly in high SNR environment between source to relay and source to destination. According to simulation result, proposed scheme has up to 2.2 dB better BER performance than conventional cooperative scheme at BER of 10?3 and has similar BER performance with the STCDD scheme particularly in high SNR environment between source to relay and source to destination. Throughput of the proposed scheme is better than those of other cooperative schemes. Therefore proposed scheme is more efficient than other cooperative scheme and can be efficiently used in high SNR environment between source to relay and source to destination. 相似文献
97.
98.
Han-Jun Oh In-Ki Kim Kyung-Wook Jang Jong-Ho Lee Seunghyun Lee Choong-Soo Chi 《Metals and Materials International》2012,18(4):673-677
The effects of electrolyte and applied potentials on TiO2 nanotube morphologies were investigated. The specific surface area of the TiO2 nanotubes was measured to be 57 m2/g for titania nanotubes formed in HF, and 147 m2/g formed in organic electrolyte, respectively. The results of adsorption-desorption isotherms agree with the morphology of TiO2 nanotubes. The length and average diameter of nanotubes were influenced by electrolyte and anodic potentials. The multilayered TiO2 nanotube arrays can be fabricated by changing the electrolyte composition during anodization. 相似文献
99.
Lee JH Yoon SM Park SJ Cha IS Shin HJ Choi JY Kim JM Paik U 《Journal of nanoscience and nanotechnology》2012,12(2):1569-1572
The doping behavior of single-walled carbon nanotubes (SWCNTs) was investigated with an emphasis on the control of the conformation of sodium dodecylbenzene sulfonate (NaDDBS) with sulfonate groups acting as an electro-withdrawing group. The conformation of adsorbed NaDDBS on SWCNTs was controlled as a function of the amount of NaDDBS. The doping behavior of SWCNTs was significantly affected by the dosing amount of NaDDBS due to the conformational change of NaDDBS adsorbed on the SWCNT surface, which affected the spatial distance between the SWCNT surface and the sulfonate groups in NaDDBS. At a higher concentration, the spatial distance between the sulfonate group in NaDDBS and SWCNT was not sufficiently close enough to dope SWCNT due to the repulsive forces between the sulfonate groups in NaDDBS. Alternatively, at a lower concentration, NaDDBS acted as a p-type dopant for SWCNTs. To this end, this paper demonstrates a new tendency of doping that is related to the adsorbed behavior of a dispersant. 相似文献
100.
In this paper, the global nonlinear Galerkin method is used to perform an accurate and efficient analysis of the large deflection behavior of a simply-supported rectangular plate under combined loads. Through applying the Galerkin method to the governing nonlinear partial differential equations (PDEs) of the plate, we derive a system of coupled third order nonlinear algebraic equations (NAEs). However, the resultant system of NAEs is thought to be hard to tackle because one has to find the one physical solution from among the possible multiple solutions. Therefore, a suitable initial guess is required to lead to the real solution for given load conditions. The feature of this paper is that we apply the global nonlinear Galerkin method to the governing PDEs and solve the resultant NAEs directly in each load step. To keep track of the physical solution, the initial guess for the current load step is provided by taking the solution of the NAEs for the last step as the initial guess. Besides, the size of the NAEs grows dramatically larger, with the increase of the number of terms of the trial functions, which will cost much more computational efforts. An exponentially convergent scalar homotopy algorithm (ECSHA) is introduced to solve the large set of NAEs. The approach in the present paper is more direct and simpler than either the incremental global Galerkin method, or the incremental local Galerkin method (finite element method) based on a symmetric incremental weak-form; both of which methods lead to the inversion of tangent stiffness matrices and Newton-Raphson iterations in each load step. The present method of exponentially convergent scalar homotopy of directly solving the NAEs is much better than the quadratically convergent Newton-Raphson method. Several numerical examples are provided to validate the feasibility and efficiency of the proposed scheme. 相似文献