全文获取类型
收费全文 | 1716篇 |
免费 | 82篇 |
国内免费 | 116篇 |
专业分类
电工技术 | 28篇 |
综合类 | 124篇 |
化学工业 | 316篇 |
金属工艺 | 238篇 |
机械仪表 | 66篇 |
建筑科学 | 145篇 |
矿业工程 | 35篇 |
能源动力 | 44篇 |
轻工业 | 101篇 |
水利工程 | 34篇 |
石油天然气 | 58篇 |
武器工业 | 5篇 |
无线电 | 95篇 |
一般工业技术 | 175篇 |
冶金工业 | 76篇 |
原子能技术 | 145篇 |
自动化技术 | 229篇 |
出版年
2024年 | 3篇 |
2023年 | 21篇 |
2022年 | 51篇 |
2021年 | 84篇 |
2020年 | 44篇 |
2019年 | 31篇 |
2018年 | 43篇 |
2017年 | 34篇 |
2016年 | 51篇 |
2015年 | 81篇 |
2014年 | 54篇 |
2013年 | 79篇 |
2012年 | 54篇 |
2011年 | 98篇 |
2010年 | 71篇 |
2009年 | 96篇 |
2008年 | 78篇 |
2007年 | 86篇 |
2006年 | 69篇 |
2005年 | 48篇 |
2004年 | 67篇 |
2003年 | 55篇 |
2002年 | 53篇 |
2001年 | 210篇 |
2000年 | 70篇 |
1999年 | 47篇 |
1998年 | 20篇 |
1997年 | 26篇 |
1996年 | 30篇 |
1995年 | 17篇 |
1994年 | 18篇 |
1993年 | 25篇 |
1992年 | 23篇 |
1991年 | 11篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 3篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1963年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1914条查询结果,搜索用时 15 毫秒
11.
12.
铜硅取代的酞青材料LB膜气敏传感器的研究 总被引:2,自引:0,他引:2
采用LB膜技术对沉积在石英晶振的铜硅取代的酞青材料的气体敏感性进行了系统研究,结果表明,该方法所获得的敏感膜敏感度高,反应迅速,稳定性较好。 相似文献
13.
采用自行研制的LB自动提膜装置,制备出大面积(10×8cm2)、高质量的PMMA超薄抗蚀剂膜,并将其用于高分辨率铬掩模版的研制。通过电子束曝光,湿法蚀刻,制作了分辨率优于0.5μm,特征线宽0.38μm的4(100mm)铬掩模版。 相似文献
14.
A series of nanocomposite thin films, composed of Nd2Fe14B and α-Fe, has been prepared by DC-magnetron sputtering combined ion beam sputtering onto Si (100) substrates. The effects of post annealing on the microstructure and magnetic properties of [NdFeB/α-Fe/NdFeB]-type thin films have been investigated. The X-ray diffraction (XRD) study showed that annealing of the films for 30min at temperatures 550,600,650,700℃ resulted in the appearance of diffraction peaks, characteristic for Nd2Fe14B tetragonal structure, α-Fe and Nd2O3 phases. The investigation using the Vibrating Sample Magnetometer (VSM) with a maximum applied field of 2 T indicated that with the increase of the annealing temperature, the magnetic properties of the multilayer films were improved and reached peak value at 650℃ (Hci=41.72kA·m-1, Mr/Ms=0.4, (BH)max=30.35kJ·m-3), after which the magnetic properties were decreased greatly. Along with the increase of the thickness of α-Fe layer from Tα-Fe16nm, the coercivity Hci, saturation magnetization Ms, and remanence ratio Mr/Ms all declined. As the Atomic Force Microscope (AFM) indicated, after being annealed at 650℃ for 30min, the sample was showed fine surface morphology with grain size 60nm≤dα-Fe≤80nm and 100nm≤dNdFeB≤150nm. 相似文献
15.
Daniel Nedvd Petr Hoek Petr Klíma Klra Hoyerov 《International journal of molecular sciences》2021,22(7)
Cytokinins are a class of phytohormones, signalling molecules specific to plants. They act as regulators of diverse physiological processes in complex signalling pathways. It is necessary for plants to continuously regulate cytokinin distribution among different organs, tissues, cells, and compartments. Such regulatory mechanisms include cytokinin biosynthesis, metabolic conversions and degradation, as well as cytokinin membrane transport. In our review, we aim to provide a thorough picture of the latter. We begin by summarizing cytokinin structures and physicochemical properties. Then, we revise the elementary thermodynamic and kinetic aspects of cytokinin membrane transport. Next, we review which membrane-bound carrier proteins and protein families recognize cytokinins as their substrates. Namely, we discuss the families of “equilibrative nucleoside transporters” and “purine permeases”, which translocate diverse purine-related compounds, and proteins AtPUP14, AtABCG14, AtAZG1, and AtAZG2, which are specific to cytokinins. We also address long-distance cytokinin transport. Putting all these pieces together, we finally discuss cytokinin distribution as a net result of these processes, diverse in their physicochemical nature but acting together to promote plant fitness. 相似文献
16.
LUO Yang JI Qigen ZHANG Ning SU Xiujin Central Iron Steel Research Institute Ministry of Metallurgical Industry Beijing ChinaSUN Daliang Shandong University Jinan China senior engineer Department of Precious Alloys Central Iron Steel Research Institute Beijing China 《金属学报(英文版)》1989,2(7):27-32
Based on the observation of temperature variation of both domain structure and magnetic con-trast.the thermal demagnetization and randomness of domain nucleation was discussed. 相似文献
17.
18.
研究了00Crl7Nil4M02不锈钢材料的机械性能、焊接性能和耐腐蚀性能,从用户和研究开发的角度探讨了其在压力容器、化工装置、化肥装置、海洋装置和建筑业等领域的应用。 相似文献
19.
2A14-T6铝合金大规格棒材时效制度的研究 总被引:2,自引:0,他引:2
2A14铝合金大规格棒材性能不稳定,在生产中抗拉强度常达不到国家标准要求。经过一系列热处理工艺试验,确定了2A14-T6合金大规格棒材的人工时效制度。 相似文献
20.
CHENFei ZHAHGYue-fei LiuYu TANGBin PANJun-de 《材料热处理学报》2004,25(5):401-404
This paper introduces a new titanium alloys surface strengthening treatment by using the arc-added glow discharge plasmas non-hydrogen carburization technique. High purity and high strength graphite is selected as cooling cathode arc source for supplying carbon atoms and particle, which migrate to the titanium alloy(Ti6Al4V) surface and form modified layer. Thus, the hydrogen embrittlement is avoided while the tfibological behavior of the titanium alloy surface is improved in the respects of anti-friction and anti-wear ability.The tribological behavior of the modified layer under dry sliding against SAE52100 steel was evaluated on a ball-on-disc test rig. The results showed that the modified layer obtained a thickness of 30μm at 980℃, 30minutes. The microhardness of the Ti6Al4V alloy surface attained 936 HV, which was much larger than that of the Ti6AI4V alloy. The Ti6AI4V alloy was characterized by adhesion wear and scuffing under dry sliding against the steel, while the surface modified layer experienced much abated adhesion wear and scuffing under the same testing condition. This could be attributed to the carbon dement with different modalities exists in the modified layer.The modified layer showed good friction-reducing and fair anti-wear ability in dry sliding against the steel. Using the SEM,XRD and XPS, the phase structure and morphology of the carburization modified layer was analyzed. 相似文献