全文获取类型
收费全文 | 78499篇 |
免费 | 8109篇 |
国内免费 | 4672篇 |
专业分类
电工技术 | 5917篇 |
技术理论 | 3篇 |
综合类 | 6760篇 |
化学工业 | 11927篇 |
金属工艺 | 4432篇 |
机械仪表 | 5208篇 |
建筑科学 | 6118篇 |
矿业工程 | 2430篇 |
能源动力 | 2059篇 |
轻工业 | 7579篇 |
水利工程 | 1941篇 |
石油天然气 | 3132篇 |
武器工业 | 869篇 |
无线电 | 8746篇 |
一般工业技术 | 8270篇 |
冶金工业 | 3233篇 |
原子能技术 | 1123篇 |
自动化技术 | 11533篇 |
出版年
2024年 | 468篇 |
2023年 | 1483篇 |
2022年 | 2893篇 |
2021年 | 3803篇 |
2020年 | 2916篇 |
2019年 | 2210篇 |
2018年 | 2501篇 |
2017年 | 2851篇 |
2016年 | 2427篇 |
2015年 | 3516篇 |
2014年 | 4628篇 |
2013年 | 5387篇 |
2012年 | 6055篇 |
2011年 | 6169篇 |
2010年 | 5843篇 |
2009年 | 5339篇 |
2008年 | 5177篇 |
2007年 | 5070篇 |
2006年 | 4421篇 |
2005年 | 3572篇 |
2004年 | 2556篇 |
2003年 | 1980篇 |
2002年 | 1950篇 |
2001年 | 1558篇 |
2000年 | 1391篇 |
1999年 | 1136篇 |
1998年 | 717篇 |
1997年 | 648篇 |
1996年 | 578篇 |
1995年 | 454篇 |
1994年 | 355篇 |
1993年 | 263篇 |
1992年 | 206篇 |
1991年 | 169篇 |
1990年 | 114篇 |
1989年 | 110篇 |
1988年 | 85篇 |
1987年 | 43篇 |
1986年 | 49篇 |
1985年 | 17篇 |
1984年 | 33篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 23篇 |
1980年 | 32篇 |
1979年 | 14篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1959年 | 10篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
53.
织物-树脂复合材料层压板的准静态侵彻机理 总被引:4,自引:1,他引:3
本文利用MTS得到了芳纶和高强维纶织物复合材料层压板受尖头侵彻体穿孔的准静态侵彻曲线 ,比较和分析了不同类型纤维集合体与热固性树脂和热塑性树脂复合材料的破坏模式 ,并考察了芳纶织物复合材料层压板侵彻的逐步破坏过程 ,揭示了复合材料层压板的准静态侵彻机理。 相似文献
54.
The low melting point metallic tin powder or alloy of tin and lead was blended with polypropy-lene. A kind of in situ composite has been prepared. The variations of torque were studied when the composites were mixed in Haake torque rheogeniometer. By way of capillary extrusion, effects upon rheology of the in situ com-posites of the low melting point metals (LMPM) and coupling agent for their different variety and content, were investigated. From flow curves, the results indicate that in situ composites mixed with the LMPM are a kind of pseudoplastic fluid. If the LMPM were melted, the higher the content of the LMPM , the lower apparent viscosity of composites. Meanwhile, when the coupling agent is added into composites, the viscosity of composite will go up first and drop then. This shows that the LMPM have a promoter flow action on the polypropylene. 相似文献
55.
The feasibility of the anodic protection of titanium evaporators in Al2(SO4)3 solution was studied by the measurement of polarization curves, weight loss, solubility of passive film and AC impedance. The protection parameters and efficiency were determined. In addition, the practical technology of anodic protection was studied by screening reference electrodes and auxiliary cathodes. Throwing power was also measured. Four rows of tube-type evaporators of titanium have been anodically protected in situ. Field tests lasting more than one year show satisfactory results. 相似文献
56.
57.
应用色谱—质谱(GC-MS)及裂解色谱-质谱(PGC-MS)测定了乙烯基三甲基硅烷等离子体聚合反应中的气体冷凝物及聚合物,研究推导了等离子体聚合反应历程。单体在气相中被电子撞击,然后扩散到基底,在基底发生链增长和链终止反应。 相似文献
58.
This paper reports a new, highly integrated modular design approach for pulsewidth-modulation AC-AC converters based on a modular phase-bank structure. Novel high-power 3-in-1 integrated bi-directional power modules (IBPM) rated at 1200-V AC and 150 A and the 3-to-1 phase bank circuits have been successfully developed, fabricated and tested. This enables the modularity design of the multiphase converter systems and reduces the critical parasitic inductance. A theoretical analysis of the IBPM's silicon utilization for this new breed of direct power converters has been outlined. A lab prototype at medium power level has been successfully designed, implemented, and tested with good results. A nearly 460-VRMS out voltage at a 1:0.955 voltage transfer ratio, which, perhaps, is the highest performance reported so far in the literature, has been achieved by the novel two-side modulation control system. The converter-fed AC motor system is able to operate over the 0-240 Hz range with inherent regenerative capability and four-quadrant operation. Potential industrial applications are also briefly highlighted in this paper 相似文献
59.
In recent years, three‐dimensionally (3D) braided composites have attracted a great deal of attention because of their high‐impact damage tolerance and fatigue life, superior fracture toughness, and so forth, and have been used in aeronautics, military, and transportation. These advantages make them strong candidates for osteosynthesis devices. In this study, 3D braided carbon fiber–epoxy (C3D/EP) composites were produced via a simple vacuum impregnation technique. The load‐deflection curve, mechanical properties, and influence of fiber volume fraction, braiding angle, and axial reinforcing fibers were examined to determine their suitability for internal fixation devices. It is found that the C3D/EP composites have excellent toughness and do not show brittleness when fractured because of their relatively high void content. The flexural, shear, and impact strengths of the C3D/EP composites are excellent. It was shown that a C3D/EP composite with a stiffness similar to load‐bearing bones can be made while maintaining enough strength. It is concluded that a relatively higher void content and braiding angle is more suitable for the C3D/EP composites from the viewpoint of requirements of fracture fixation materials. The moisture absorption behavior and changes in mechanical properties caused by moisture uptake were evaluated. Results show that absorbed moisture slightly decreases mechanical properties of the C3D/EP composites. Contrary to the unreinforced epoxy, the moisture absorption behavior of the C3D/EP composites cannot be described with Fick's law of diffusion, probably because of the presence of voids and/or 3D fiber structure. The exact mechanisms should be proposed in further investigations. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1031–1039, 2002 相似文献
60.
由于悬空侧壁部分的变形状态是圆锥形零件成形的关键,而径向拉应力是实现悬空部分成形的必要条件,同时也是该部分冲压成形成败的关键为此,经力学分析得出了侧壁部分径向拉应力的解析式和造成圆锥形零件破裂的最大径向拉应力的计算式。同时分析了圆锥形零件的成形载荷。 相似文献