全文获取类型
收费全文 | 373篇 |
免费 | 32篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 9篇 |
综合类 | 1篇 |
化学工业 | 57篇 |
金属工艺 | 17篇 |
机械仪表 | 22篇 |
建筑科学 | 16篇 |
矿业工程 | 4篇 |
能源动力 | 20篇 |
轻工业 | 91篇 |
水利工程 | 4篇 |
石油天然气 | 2篇 |
无线电 | 23篇 |
一般工业技术 | 55篇 |
冶金工业 | 34篇 |
自动化技术 | 51篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 12篇 |
2021年 | 23篇 |
2020年 | 21篇 |
2019年 | 19篇 |
2018年 | 21篇 |
2017年 | 19篇 |
2016年 | 17篇 |
2015年 | 21篇 |
2014年 | 13篇 |
2013年 | 39篇 |
2012年 | 21篇 |
2011年 | 24篇 |
2010年 | 24篇 |
2009年 | 17篇 |
2008年 | 11篇 |
2007年 | 16篇 |
2006年 | 13篇 |
2005年 | 12篇 |
2004年 | 13篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1991年 | 4篇 |
1989年 | 3篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 1篇 |
排序方式: 共有406条查询结果,搜索用时 15 毫秒
61.
How to design the pilot tones that are used in channel estimation has a significant effect on the estimation performance. To achieve good performance in least square (LS) algorithm, we propose the artificial bee colony (ABC) algorithm for optimizing the placement of pilot tones in MIMO–OFDM systems. We also derive the upper bound of mean square error of LS estimation with the help of Gerschgorin disc theorem for fitness function of ABC algorithm. The results show that designing pilot tones using the ABC algorithm outperforms other considered placement strategies in terms of high system performance and low computational complexity. 相似文献
62.
Muhammet Koksal 《International Journal of Circuit Theory and Applications》2013,41(3):319-329
In this article, a general all‐pole current transfer function synthesis procedure using current backward transconductance amplifiers (CBTAs) is proposed. The proposed configuration uses n current backward transconductance amplifiers and n grounded capacitors as the only type of passive elements. The circuit is eligible to realize any all‐pole transfer characteristics with a given strictly Hurwitz (stable) denominator polynomial. Further, it is straightforward to find the values of the passive elements from the coefficients of this polynomial by using the Routh–Hurwitz algorithm as in the realization of a two‐element kind passive network synthesis. In this sense and as far as the author's knowledge, it is the only active structure that can be synthesized like a passive two‐element kind Cauer circuit. The simulations that are performed using PSPICE exhibit satisfactory results coherent with the theory. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
63.
Daniel N. Farhey Razi Naghavi Alper Levi Aniruddha M. Thakur Mark A. Pickett Douglas K. Nims A. Emin Aktan 《Canadian Metallurgical Quarterly》2000,5(1):39-48
Diagnostic truck-load tests and microstructural analysis were applied for structural deterioration assessment of a steel truss bridge and its rehabilitation design. The feasibility and potential benefits of using advanced field experimental techniques within a structural-identification framework have been demonstrated. Experimental information, coupled with visual inspection, engineering experience, and intuition, increased the level of confidence in the results of the condition-assessment process, permitting a more rational and cost-effective rehabilitation design. Based on the condition assessment, a two-step rehabilitation is recommended for the bridge: Restoration for a safe service life of 5–7 years, and a subsequent effort for preservation beyond. 相似文献
64.
65.
66.
This paper describes the removal of Cd(II), Pb(II), Cu(II), and Ni(II) ions from aqueous solutions using chemically modified pine barks (Pinus nigra). In this article, effects of chemical modification methods on the adsorption capacity have been investigated. Changes of the surface properties were examined by the FTIR, SEM and zeta potential analyses. HCl, NaOH, Fenton reactive, polymerization, acetone, ethanol, chloroform, tetra ethylene glycol, diethyl ether and glycol were used for modification processes. Maximum adsorption capacities were obtained by modification with NaOH (13-20 mg/g), Fenton (12-17 mg/g) and polymerization (12-16.5 mg/g). These modification processes also decreased Chemical Oxygen Demand of water from 1820 mg/L for raw pine barks to 35 mg/L for NaOH modified barks. Adsorption capacities of adsorbents increased from 2 mg/g to 20 mg/g as a result of modification that accordingly increase adsorbent surface activity. 相似文献
67.
Metal Science and Heat Treatment - Methods of electron microscopy and x-ray diffractometry are used to study the structure of a titanium coating deposited on a magnesium substrate by high-velocity... 相似文献
68.
S leyman ZEN Muhammet G khan ALTUN Ali MARDANI-AGHABAGLOU Kambiz RAMYAR 《Frontiers of Structural and Civil Engineering》2020,14(6):1573
Despite the large variations in the behaviors of water-reducing admixtures upon changes in their structures, most previous reports on the cement-admixture compatibility did not provide sufficient information on the structure of the admixture. Hence, the evaluation and generalization of the reports on the cement-admixture compatibility are challenging. In this study, three different polycarboxylate-ether-based water-reducing admixtures with the same free nonionic content, anionic/nonionic molar ratio, and main chain length and different side chain lengths were produced. The compatibility of these admixtures with a CEM I 42.5R-type cement was investigated. In addition, an analysis of variance was performed on the experiment results to evaluate the contributions of the admixture type, admixture/cement ratio, and elapsing time to the Marsh funnel flow time, mini-slump, slump flow, and compressive strength. The water-reducing admixtures having long or short side chains reduced the initial flow characteristics of the cementitious systems. However, the admixture having the shortest side chain was better with regard to flow retention. The side chain length of the admixture did not have significant effects on the compressive strength and water absorption capacity of the mortar mixtures and mini-slump performances of the cement paste mixtures. Regarding the behaviors of the admixtures in the cementitious systems, an optimal admixture side chain molecular weight is proposed. 相似文献
69.
70.