全文获取类型
收费全文 | 3614篇 |
免费 | 396篇 |
国内免费 | 132篇 |
专业分类
电工技术 | 242篇 |
综合类 | 190篇 |
化学工业 | 762篇 |
金属工艺 | 132篇 |
机械仪表 | 185篇 |
建筑科学 | 173篇 |
矿业工程 | 131篇 |
能源动力 | 117篇 |
轻工业 | 186篇 |
水利工程 | 55篇 |
石油天然气 | 118篇 |
武器工业 | 15篇 |
无线电 | 509篇 |
一般工业技术 | 551篇 |
冶金工业 | 254篇 |
原子能技术 | 38篇 |
自动化技术 | 484篇 |
出版年
2024年 | 13篇 |
2023年 | 53篇 |
2022年 | 112篇 |
2021年 | 151篇 |
2020年 | 103篇 |
2019年 | 66篇 |
2018年 | 94篇 |
2017年 | 100篇 |
2016年 | 128篇 |
2015年 | 161篇 |
2014年 | 204篇 |
2013年 | 251篇 |
2012年 | 224篇 |
2011年 | 234篇 |
2010年 | 223篇 |
2009年 | 179篇 |
2008年 | 229篇 |
2007年 | 163篇 |
2006年 | 192篇 |
2005年 | 131篇 |
2004年 | 104篇 |
2003年 | 116篇 |
2002年 | 137篇 |
2001年 | 110篇 |
2000年 | 78篇 |
1999年 | 79篇 |
1998年 | 71篇 |
1997年 | 69篇 |
1996年 | 51篇 |
1995年 | 47篇 |
1994年 | 31篇 |
1993年 | 26篇 |
1992年 | 24篇 |
1991年 | 35篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1976年 | 12篇 |
1975年 | 5篇 |
1970年 | 4篇 |
1965年 | 3篇 |
1964年 | 3篇 |
排序方式: 共有4142条查询结果,搜索用时 15 毫秒
991.
非金属掺杂类金刚石膜的研究进展 总被引:3,自引:0,他引:3
非金属掺杂类金刚石(DLC)膜可以优化纯类金刚石膜的一些性能.例如:掺磷DLC膜电阻率小,还可以明显提高其血液相容性;掺氮DLC膜不仅电阻率小,可作为半导体材料.还具有热稳定性好的优点;掺氟DLC膜在憎水性、耐蚀性、热稳定性和降低介电常数等方面更为优异;硅掺杂使膜中氢含量减少、内应力减小、粗糙度和摩擦系数降低.对非金属掺杂DLC膜的进展做了概括及分析,展现出其广泛的应用前景. 相似文献
992.
大气、海水及生物组织等都属于浑浊介质,浑浊介质的光学特性表征是近年来的研究热点.从浑浊介质光散射特性的散斑表征、散斑偏振技术的应用及在医学生物学中的应用三个方面综述了浑浊介质光学特性的激光散斑表征方法及其进展. 相似文献
993.
994.
Tai Sun Jian Liu Yi Jia Hui Wang Dalin Sun Min Zhu Xiangdong Yao 《International Journal of Hydrogen Energy》2012
LiBH4 has been attracted tremendous research interest as a hydrogen storage material for mobile applications due to its very high gravimetric hydrogen capacity of 18.6 wt%. However, its real use is heavily hindered by the high operational temperature that is required above 350 °C to release hydrogen with various recent improvements. This is obviously much higher than the ambient temperature of about 100 °C. In this paper, we report the synthesis of LiBH4 confined by SBA-15 template, which achieves fast hydrogen release of LiBH4 at ∼100 °C. The confined LiBH4 system starts to release hydrogen at only 45 °C and can release 8.5 wt% hydrogen (on the basis of LiBH4 itself) within 10 min at 105 °C, which opens a new window and overcome the most challenging barrier to realize practical hydrogen storage of LiBH4. 相似文献
995.
The commercial finite element program LS-DYNA was employed to evaluate the response and energy absorbing capacity of cylindrical
metal tubes that are externally wrapped with composite. The numerical simulation elucidated the crushing behaviors of these
tubes under both quasi-static compression and axial dynamic impact loading. The effects of composite wall thickness, loading
conditions and fiber ply orientation were examined. The stress–strain curves under different strain rates were used to determine
the dynamic impact of strain rate effects on the metal. The results were compared with those of a simplified analytical model
and the mean crushing force thus predicted agreed closely with the numerical simulations. The numerical results demonstrate
that a wrapped composite can be utilized effectively to enhance the crushing characteristics and energy absorbing capacity
of the tubes. Increasing the thickness of the composite increases the mean force and the specific energy absorption under
both static and dynamic crushing. The ply pattern affects the energy absorption capacity and the failure mode of the metal
tube and the composite material property is also significant in determining energy absorption efficiency. 相似文献
996.
Qilong Tai Richard K.K. Yuen Wei Yang Zhihua QiaoLei Song Yuan Hu 《Composites Part A》2012,43(3):415-422
This paper presents a preliminary investigation on the effects of organically modified iron-montmorillonite (Fe-OMT) and zinc borate (ZnB) on thermal degradation behaviors and flame retardancy of melamine polyphosphate (MPP) flame-retarded glass fiber reinforced polyamide 6 (GFPA6). The samples were characterized using limiting oxygen index (LOI), UL-94 tests, thermogravimetric analysis (TGA), Fourier transform infrared coupled with the thermogravimetric analyzer (TG-FTIR) and Microscale Combustion Calorimeter (MCC) measurements. The residue after LOI test was also analyzed by Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and Raman spectroscopy. A substitution of a certain fraction of MPP with ZnB or Fe-OMT can significantly improve the UL-94 rating of GFPA6/MPP composites from no rating to V0 rating, exhibiting excellent flame retardacny. Based on the investigations, different flame retardant mechanisms were proposed for the two effective flame-retardant formulations. 相似文献
997.
Zhu Y Li W Zhang Y Li J Liang L Zhang X Chen N Sun Y Chen W Tai R Fan C Huang Q 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(11):1771-1779
Nanodiamonds (NDs) possess many excellent physical and chemical properties that make them attractive materials for applications in biomedicine. In this paper, the adsorption and delivery of a large amount of sodium ions into the cell interior by NDs in serum-free medium is demonstrated. The excess sodium ions inside the cells induce osmotic stresses followed by cell swelling and an increase in the intracellular levels of calcium and reactive oxygen species (ROS), which leads to severe cellular damage. In complete culture medium, however, serum proteins wrapped around the NDs effectively prevent the sodium ions from adsorbing onto the NDs, and thus the NDs show no cytotoxicity. This work is the first to elaborate on the correlation between the sodium ions adsorbed on the nanomaterials and their bio-effects. Excessive ions delivered into cells by NDs might have potential applications in tumor therapy. 相似文献
998.
999.
The effect of twisting on the electrical resistance of a raw single-walled carbon nanotube (SWCNT) rope was investigated and found to increase with increasing number of twists, varying from 28.7 Ω initially to 35.2 Ω after 12 twists. There are two reasons for this. One is that the twisting generated more contact points between the SWCNTs and catalytic nanoparticles, resulting in a high density of high local resistance points. The other is that the protrusion of SWCNTs in a rope twisted a large number of times (12–15 twists) partially interrupted the conducting path. By using a 9-V battery, ignition of the rope could be produced at a threshold resistance between 17.5 and 21.1 Ω, and this could be used to ignite ferrocene with the process lasting for several minutes. 相似文献
1000.
LA Tai YT Kang YC Chen YC Wang YJ Wang YT Wu KL Liu CY Wang YF Ko CY Chen NC Huang JK Chen YF Hsieh TR Yew CS Yang 《Analytical chemistry》2012,84(15):6312-6316
Transmission electron microscopy (TEM) is a unique and powerful tool for observation of nanoparticles. However, due to the uneven spatial distribution of particles conventionally dried on copper grids, TEM is rarely employed to evaluate the spatial distribution of nanoparticles in aqueous solutions. Here, we present a microchip nanopipet with a narrow chamber width for sorting nanoparticles from blood and preventing the aggregation of the particles during the drying process, enabling quantitative analysis of their aggregation/agglomeration states and the particle concentration in aqueous solutions. This microchip is adaptable to all commercial TEM holders. Such a nanopipet proves to be a simple and convenient sampling device for TEM image-based quantitative characterization. 相似文献