全文获取类型
收费全文 | 5951篇 |
免费 | 327篇 |
国内免费 | 50篇 |
专业分类
电工技术 | 86篇 |
综合类 | 76篇 |
化学工业 | 1288篇 |
金属工艺 | 233篇 |
机械仪表 | 225篇 |
建筑科学 | 267篇 |
矿业工程 | 50篇 |
能源动力 | 450篇 |
轻工业 | 855篇 |
水利工程 | 42篇 |
石油天然气 | 61篇 |
武器工业 | 2篇 |
无线电 | 341篇 |
一般工业技术 | 1030篇 |
冶金工业 | 431篇 |
原子能技术 | 78篇 |
自动化技术 | 813篇 |
出版年
2024年 | 22篇 |
2023年 | 81篇 |
2022年 | 151篇 |
2021年 | 206篇 |
2020年 | 220篇 |
2019年 | 212篇 |
2018年 | 284篇 |
2017年 | 256篇 |
2016年 | 270篇 |
2015年 | 164篇 |
2014年 | 243篇 |
2013年 | 592篇 |
2012年 | 341篇 |
2011年 | 350篇 |
2010年 | 278篇 |
2009年 | 354篇 |
2008年 | 318篇 |
2007年 | 261篇 |
2006年 | 199篇 |
2005年 | 135篇 |
2004年 | 135篇 |
2003年 | 154篇 |
2002年 | 185篇 |
2001年 | 139篇 |
2000年 | 83篇 |
1999年 | 69篇 |
1998年 | 158篇 |
1997年 | 84篇 |
1996年 | 60篇 |
1995年 | 33篇 |
1994年 | 35篇 |
1993年 | 27篇 |
1992年 | 24篇 |
1991年 | 26篇 |
1990年 | 18篇 |
1989年 | 15篇 |
1988年 | 10篇 |
1987年 | 14篇 |
1986年 | 18篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1976年 | 8篇 |
1970年 | 3篇 |
1967年 | 3篇 |
1965年 | 3篇 |
排序方式: 共有6328条查询结果,搜索用时 15 毫秒
21.
22.
新型高k栅介质材料研究进展 总被引:5,自引:0,他引:5
随着半导体技术的不断发展,MOSFET(metal-oxide-semiconductor field effect transistor)的特征尺寸不断缩小,栅介质等效氧化物厚度已小至nm数量级。这时电子的直接隧穿效应将非常显著,将严重影响器件的稳定性和可靠性。因此需要寻找新型高k介质材料,能够在保持和增大栅极电容的同时,使介质层仍保持足够的物理厚度来限制隧穿效应的影响。本文综述了研究高k栅介质材料的意义;MOS栅介质的要求;主要新型高k栅介质材料的最新研究动态;展望了高k介质材料今后发展的主要趋势和需要解决的问题。 相似文献
23.
Effect of flexure induced transverse crack and self-healing on chloride diffusivity of reinforced mortar 总被引:2,自引:0,他引:2
Mustafa Şahmaran 《Journal of Materials Science》2007,42(22):9131-9136
Cracks in reinforced concrete are unavoidable. Durability is of increasing concern in the concrete industry, and it is significantly
affected by the presence of cracks. The corrosion of reinforcing steel due to chloride ions in deicing salts or sea-water
is a major cause of premature deterioration of reinforced concrete structures. Although, it is generally recognized that cracks
accelerate the ingress of chlorides in concrete, a lack of consensus on this subject does not yet allow reliable quantification
of their effects. The present work studies the relationship between crack widths and chloride diffusivity. Flexural load was
introduced to generate cracks of width ranging between 29 and 390 μm. As crack width was increased, the effective diffusion
coefficient was also increased, thus reducing the initiation period of corrosion process. For cracks with widths less than
135 μm, the effect of crack widths on the effective diffusion coefficient of mortar was found to be marginal, whereas for
crack widths higher than 135 μm the effective diffusion coefficient increased rapidly. Therefore, the effect of crack width
on chloride penetration was more pronounced when the crack width is higher than 135 μm. Results also indicate that the relation
between the effective diffusion coefficient and crack width was found to be power function. In addition, a significant amount
of self-healing was observed within the cracks with width below 50 μm subjected to NaCl solution exposure. The present research
may provide insight into developing design criteria for a durable concrete and in predicting service life of a concrete structures. 相似文献
24.
Conceptual damage-sensitive features for structural health monitoring: Laboratory and field demonstrations 总被引:2,自引:0,他引:2
F. Necati Catbas Mustafa Gul Jason L. Burkett 《Mechanical Systems and Signal Processing》2008,22(7):1650-1669
The use of damage-sensitive features to evaluate structural condition or health is a very critical aspect of structural health monitoring. The purpose of this paper is to investigate the potential of two different damage-sensitive features for detecting damage. Different damage scenarios are simulated on a large-scale laboratory structure and a three-span highway bridge for demonstration. The features presented in this paper are the modal flexibility-based deflection and curvature both of which are obtained directly from dynamic properties. In the literature, flexibility associated with mode shapes and mode shapes curvatures have been mostly explored. In this study, multi-input–multi-output dynamic data are used to obtain modal flexibility, which is a close approximation to the actual flexibility. A main novelty is that the curvature is calculated from the deflected shapes using the modal flexibility as opposed to using modal vectors. In this paper, the theory of the methodology is explained and then experimental studies and results are presented. For the experimental studies, the laboratory specimen and the three-span bridge were gradually damaged. It is shown that both deflection and curvature are conceptual and physically meaningful features for damage detection and localization. The issues and the requirements for these features to perform successfully are also presented. 相似文献
25.
26.
27.
Nilgün Kzlcan Belks Ustamehmetolu Nesrin
z A. Sezai Sara Ahmet Akar 《应用聚合物科学杂志》2003,89(11):2896-2901
Soluble and processable conductive copolymers of silicone tegomers and pyrrole were developed. This was easily accomplished by the oxidative polymerization of pyrrole monomer by Ce(IV) salt in the presence of silicone tegomers with hydroxyl chain ends. The resulting copolymers were soluble in dimethylformamide. The products were characterized by Fourier transform infrared, 1H‐NMR, and four‐point probe conductivity, and their surface properties were investigated with contact‐angle measurements. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2896–2901, 2003 相似文献
28.
A study is made of boron removal from Kizildere/Turkey geothermal waste water using the boron selective resin Amberlite IRA 743. The resin in salt form has no boron removal capacity if the solution is unable to neutralize the released acid during the exhaustion period. In the case of Kizildere waste water, with a pH value of 8.9 and high HCO3− content, single stage regeneration is feasible and the exhausted resin can be regenerated economically. According to a preliminary estimate, the electricity production cost would rise by 1 ¢/kWh. 相似文献
29.
Jale Müslehiddinolu Paul Lobben Simon Leung Lori Spangler San Kiang 《Catalysis Today》2007,123(1-4):164-170
Hydrogenolysis of a carbobenzyloxy group (CBz) was studied utilizing molecular hydrogen in the presence of carbon-supported palladium catalyst. It was demonstrated that the kinetics of the reaction are greatly influenced by the presence of the CO2 by-product. It was found out that the presence of CO2 determines whether the reaction is first or zero order since it causes deactivation of the catalyst via inhibition. The effect of potassium carbonate (K2CO3) and triethylamine (TEA) as additives was investigated. A considerable solvent effect was also observed that may be explained by the variation of dispersion of the catalyst from one solvent to another. 相似文献
30.
本文对国内外微机在玻璃工业中的应用现状进行了综述与评价 ,主要讨论微机应用对玻璃工业的影响 ,并初步探讨了玻璃工业中微机应用的前景 相似文献