全文获取类型
收费全文 | 975篇 |
免费 | 97篇 |
国内免费 | 35篇 |
专业分类
电工技术 | 70篇 |
综合类 | 65篇 |
化学工业 | 244篇 |
金属工艺 | 64篇 |
机械仪表 | 42篇 |
建筑科学 | 63篇 |
矿业工程 | 23篇 |
能源动力 | 29篇 |
轻工业 | 87篇 |
水利工程 | 37篇 |
石油天然气 | 66篇 |
武器工业 | 18篇 |
无线电 | 89篇 |
一般工业技术 | 93篇 |
冶金工业 | 32篇 |
原子能技术 | 10篇 |
自动化技术 | 75篇 |
出版年
2024年 | 4篇 |
2023年 | 27篇 |
2022年 | 50篇 |
2021年 | 54篇 |
2020年 | 50篇 |
2019年 | 31篇 |
2018年 | 33篇 |
2017年 | 28篇 |
2016年 | 36篇 |
2015年 | 47篇 |
2014年 | 57篇 |
2013年 | 48篇 |
2012年 | 73篇 |
2011年 | 63篇 |
2010年 | 61篇 |
2009年 | 62篇 |
2008年 | 47篇 |
2007年 | 59篇 |
2006年 | 60篇 |
2005年 | 40篇 |
2004年 | 33篇 |
2003年 | 20篇 |
2002年 | 19篇 |
2001年 | 11篇 |
2000年 | 14篇 |
1999年 | 16篇 |
1998年 | 15篇 |
1997年 | 13篇 |
1996年 | 15篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有1107条查询结果,搜索用时 15 毫秒
41.
采用在铸型中放置石墨片,然后浇注低碳合金钢的方法,制造表面耐磨材料。分析了铸造过程中渗碳的效果及机理,讨论了影响组织和渗层深度的因素。 相似文献
42.
Kan Kan Yuan Zheng Shifeng Fu Huiwen Liu Chunxia Yang Xin Zhang 《Journal of Mechanical Science and Technology》2017,31(4):1561-1568
Current research on the stability of tubular pumps is mainly concerned with the transient hydrodynamic characteristics. However, the structural response under the influence of fluid-structure interaction hasn’t been taken fully into consideration. The instability of the structure can cause vibration and cracks, which may threaten the safety of the unit. We used bidirectional fluid-structure interaction to comprehensively analyze the dynamic stress characteristics of the impeller blades of the shaft extension tubular pump device. Furthermore, dynamic stress of impeller blade of shaft extension tubular pump device was solved under different lift conditions of 0° blade angle. Based on Reynolds-average N-S equation and SST k-ω turbulence model, numerical simulation was carried out for three-dimensional unsteady incompressible turbulent flow field of the pump device whole flow passage. Meanwhile, the finite element method was used to calculate dynamic characteristics of the blade structure. The blade dynamic stress distribution was obtained on the basis of fourth strength theory. The research results indicate that the maximum blade dynamic stress appears at the joint between root of inlet side of the blade suction surface and the axis. Considering the influence of gravity, the fluctuation of the blade dynamic stress increases initially and decreases afterwards within a rotation period. In the meantime, the dynamic stress in the middle part of inlet edge presents larger relative fluctuation amplitude. Finally, a prediction method for dynamic stress distribution of tubular pump considering fluid-structure interaction and gravity effect was proposed. This method can be used in the design stage of tubular pump to predict dynamic stress distribution of the structure under different operating conditions, improve the reliability of pump impeller and analyze the impeller fatigue life. 相似文献
43.
Shifeng Liu Yu-Ping Zeng Dongliang Jiang Shifeng Liu 《International Journal of Applied Ceramic Technology》2009,6(5):617-625
Mullitized porous oxidation-bonded SiC (OBSC) ceramics were fabricated with and without preheat-treated aluminosilicate by an in situ reaction-bonding process. The effects of the preheat-treated aluminosilicate on the phase development, microstructure, and mechanical properties of porous SiC ceramics were investigated. With 5.0 wt% preheat-treated aluminosilicate addition, the process of mullitization was significantly promoted. Owing to the enhancement of neck growth by the preheat-treated aluminosilicate, a high flexural strength of 86.9 MPa was achieved at an open porosity of 35.3%, and the porous SiC ceramics maintained good thermal shock resistance. With 5.0 wt% preheat-treated aluminosilicate addition, the average pore size of porous SiC ceramics was enlarged from 2.8 to 4.0 μm. The effects of preheat-treated aluminosilicate content on the oxidation degree of SiC, open porosity, and flexural strength of porous SiC ceramics were also investigated. 相似文献
44.
Ruyin Wang Shifeng Wang Yong Zhang Chaoying Wan Piming Ma 《Polymer Engineering and Science》2009,49(1):26-33
Biodegradable polymer blends consisting of poly(L ‐lactic acid) (PLLA) and poly(butylene succinate) (PBS) were prepared in the presence of dicumyl peroxide (DCP). The effects of DCP content on the mechanical properties, thermal and rheological behavior, phase morphology as well as the toughening mechanism of the blends were investigated. The notched Izod impact strength of PLLA/PBS (80/20) blend significantly increased after the addition of 0.05–0.2 phr DCP, but the strength and modulus monotonically decreased with increasing DCP content. PBS acted as a nucleating agent at the environmental temperature below its melting temperature and accelerated the crystallization rate of PLLA but had little effect on its final degree of crystallinity. The degree of crystallinity of PBS and the cold crystallization ability of PLLA gradually reduced with increasing DCP content. The addition of DCP induced an increase in viscosity of the blends at low frequencies as well as finer dispersion of PBS particles and better interfacial adhesion between PLLA and PBS, indicating the in situ compatibilization occurred between the two components. The optical clarity of PLLA/PBS blends was significantly improved after the addition of DCP, which was in accordance with the crystallization behavior and phase structure of the blends. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers 相似文献
45.
FTIR是从傅立叶级数转换而来的红外定性和定量分析法的缩写,能有效监测淬火油在使用过程中的老化过程和监控基础油的质量,对于稳定淬火剂质量和监测淬火剂在使用过程的变化具有重要作用。 相似文献
46.
镁合金表面镀镍被广泛运用于镁合金工件防腐,而镀层的起泡和脱落严重影响工件的使用寿命。本实验以ZK60镁合金为研究对象,分析了不同工件基底表面质量对镀镍层性能的影响机制。研究表明:基底表面存在的划痕和点蚀坑会显著降低镀镍层质量,引起镀层的起泡和脱落。基底表面的划痕会被保留到镀镍层中,引发镀层变薄,应力集中等问题,增加镀层开裂的几率。点蚀坑中的杂质与镁基底有不同的电化学特性,会导致镀层减薄和结合不牢。因此,提高镁合金工件基底表面光洁度、清除基底表面点蚀坑是提高镁合金镀镍层性能的必要措施。 相似文献
47.
48.
49.
采用流变学方法研究了苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)/高岭土改性沥青的流变性能,并用Carreau两段黏度模型对流变性能进行了模拟.结果表明,在实验温度范围内,基质沥青为简单牛顿流体,SBS改性沥青为非牛顿流体;SBS改性沥青存在着2个剪切变稀区域,且星形SBS改性沥青较线型SBS改性沥青的2个剪切变稀区域更为明显,随着SBS用量的增加,剪切变稀越明显.在低频区,Carreau两段黏度模型模拟曲线与实验曲线重合;随着SBS含量的增加或加入高岭土,第一时间参数值增大,高岭土与SBS的预先共混促使SBS在改性沥青中的表观份数有所增加. 相似文献
50.
胶凝砂砾石材料是一新型筑坝材料,拥有广阔的发展前景。用水量是影响胶凝砂砾石强度的重要因素。通过抗压强度试验分析用水量对胶凝砂砾石抗压强度的影响,得出:最优用水量随胶凝材料掺量的增大而增大,随砂率的增大而增大,最优用水量为85~125 kg/m~3;最优水胶比随胶凝材料用量的增加而减小,随龄期的增加呈减小的趋势,最优水胶比为0.95~1.35。用水量对抗压强度的影响仅次于水泥用量,在施工过程中,应将其作为胶凝砂砾石材料的一项重要参数来控制,以保证胶凝砂砾石材料的性能。 相似文献