全文获取类型
收费全文 | 2862篇 |
免费 | 245篇 |
国内免费 | 132篇 |
专业分类
电工技术 | 64篇 |
综合类 | 287篇 |
化学工业 | 429篇 |
金属工艺 | 387篇 |
机械仪表 | 197篇 |
建筑科学 | 824篇 |
矿业工程 | 41篇 |
能源动力 | 47篇 |
轻工业 | 9篇 |
水利工程 | 83篇 |
石油天然气 | 52篇 |
武器工业 | 11篇 |
无线电 | 90篇 |
一般工业技术 | 589篇 |
冶金工业 | 43篇 |
原子能技术 | 16篇 |
自动化技术 | 70篇 |
出版年
2024年 | 11篇 |
2023年 | 44篇 |
2022年 | 42篇 |
2021年 | 50篇 |
2020年 | 60篇 |
2019年 | 55篇 |
2018年 | 73篇 |
2017年 | 107篇 |
2016年 | 124篇 |
2015年 | 125篇 |
2014年 | 157篇 |
2013年 | 309篇 |
2012年 | 225篇 |
2011年 | 215篇 |
2010年 | 144篇 |
2009年 | 143篇 |
2008年 | 137篇 |
2007年 | 170篇 |
2006年 | 131篇 |
2005年 | 107篇 |
2004年 | 99篇 |
2003年 | 92篇 |
2002年 | 80篇 |
2001年 | 87篇 |
2000年 | 56篇 |
1999年 | 56篇 |
1998年 | 51篇 |
1997年 | 39篇 |
1996年 | 39篇 |
1995年 | 23篇 |
1994年 | 30篇 |
1993年 | 20篇 |
1992年 | 19篇 |
1991年 | 16篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 17篇 |
1986年 | 10篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 6篇 |
1982年 | 14篇 |
1981年 | 2篇 |
排序方式: 共有3239条查询结果,搜索用时 0 毫秒
41.
针对复合材料沉头螺栓连接结构的强度与损伤问题,开展了两种厚度复合材料层合板凸头与沉头螺栓连接结构挤压强度对比试验研究。试验结果表明,增加层合板厚度会引起连接结构挤压强度下降,但沉头连接结构下降比例小于凸头连接结构。通过数值模拟方法对复合材料中厚板沉头连接结构的强度及损伤失效进行分析。提出一种非线性面内连续损伤与三维混合失效模型,模型考虑了复合材料基体剪切非线性特征并改进了纤维损伤失效判据,有效解决了数值模拟中沉头复合材料连接结构难于收敛的问题。对比分析表明:沉头连接结构的数值计算结果与试验结果吻合良好,极限强度最大计算误差8.62%。 相似文献
42.
High interfacial stresses near the ends of adherends are responsible for debonding failure of bonded joints used extensively in structural engineering and microelectronics packaging. This paper proposes a stress-function variational method for determination of the interfacial stresses in a single-sided strap joint subjected to mechanical and thermal loads. During the process, two interfacial shear and normal (peeling) stress functions are introduced, and the planar stresses of adherends of the joints are expressed in terms of the stress functions according to the static equilibrium equations. Two coupled governing ordinary differential equations (ODEs) of the stress functions are obtained through minimizing the complementary strain energy of the joints and solved explicitly in terms of eigenfunctions. The stress field of the joints based on this method can satisfy all the traction boundary conditions (BCs), especially the shear-free condition near the adherend ends. Compared to results based on finite element method (FEM) and other analytic methods in the literature, the present variational method is capable of predicting highly accurate interfacial stresses. Dependencies of the interfacial stresses upon the adherend geometries, moduli and temperature are examined. Results gained in this study are applicable to scaling analysis of joint strength and examination of solutions given by other methods. The present formalism can be extended conveniently to mechanical and thermomechanical stress analysis of other bonded structures such as adhesively bonded joints, composite joints, and recently developed flexible electronics, among others. 相似文献
43.
P. Šebo P. Švec D. Jani?kovi?E. Illeková Yu. Plevachuk 《Materials Science and Engineering: A》2011,528(18):5955-5960
Influence of antimony and copper in Sn-Sb-Cu solder on the melting and solidification temperatures and on the microstructure of the interface between the solder and copper substrate after wetting the substrate at 623 K for 1800 s were studied. Microstructure of the interface between the solder and copper substrates in Cu-solder-Cu joints prepared at the same temperature for 1800 s was observed and shear strength of the joints was measured. Influence of the atmosphere - air with the flux and deoxidising N2 + 10H2 gas - was taken into account. Thermal stability and microstructure were studied by differential scanning calorimetry (DSC), light microscopy, scanning electron microscopy (SEM) with energy-dispersive spectrometry (EDS) and X-ray diffraction (XRD). Melting and solidification temperatures of the solders were determined. An interfacial transition zone was formed by diffusion reaction between solid copper and liquid solder. At the interface Cu3Sn and Cu6Sn5 phases arise. Cu3Sn is adjacent to the Cu substrate and its thickness decreases with increasing the amount of copper in solder. Scallop Cu6Sn5 phase is formed also inside the solder drop. The solid solution Sn(Sb) and SbSn phase compose the interior of the solder drop. Shear strength of the joints measured by push-off method decreases with increasing Sb concentration. Copper in the solder shows even bigger negative effect on the strength. 相似文献
44.
引入微分概念和复合材料铺层刚度分配原则,形成一种改进的求解复合材料斜面对接结构胶层应力的半解析方法 MAM(Modified semi-Analytical Method)。首先,针对铺层角度及铺层数不一致的情况,采用有限元法(FEM)平面应变模型对MAM进行验证;然后,分别用平均剪应力法、FEM及MAM预测了复合材料斜接结构的承载能力并与试验值进行对比;最后,利用MAM分析工程应用问题,考虑了被粘结体刚度不匹配及胶层厚度的变化。研究结果表明:MAM适于设计复合材料斜接结构;采用MAM能得到胶层应力的尖峰值,且应力分布与FEM计算一致。 相似文献
45.
S. Babu G.D. Janaki Ram P.V. Venkitakrishnan G. Madhusudhan Reddy K. Prasad Rao 《材料科学技术学报》2012,28(5):414-426
Friction stir lap welds were produced in 3 mm thick Alclad sheets of Al alloy 2014-T4 using two different tools (with triangular and threaded taper cylindrical pins). The effects of tool geometry on weld microstructure, lap-shear performance and failure mode were investigated. The pin profile was found to significantly influence the hook geometry, which in turn strongly influenced the joint strength and the failure mode. Welds produced in alloy 2014-T4 Alclad sheets by using triangular and threaded taper cylindrical tools exhibited an average lap-shear failure load of 16.5 and 19.5 kN, respectively, while the average failure load for standard riveted joints was only 3.4 kN. Welds produced in alloy 2014-T6 Alclad sheets and in alloy 2014-T4 bare sheets (i.e., no Alclad) were comparatively evaluated with those produced in alloy 2014-T4 Alclad sheets. While the welds made (with threaded taper cylindrical tool) in T6 and T4 conditions showed very similar lap-shear failure loads, the joint efficiency of the welds made in T6 condition (43%) was considerably lower (because of the higher base material strength) than those made in T4 condition (51%). The Alclad layers were found to present no special problems in friction stir lap welding. Welds made with triangular tool in alloy 2014-T4 Alclad and bare sheets showed very similar lap-shear failure loads. The present work provides some useful insights into the use of friction stir welding for joining Al alloys in lap configuration. 相似文献
46.
文中介绍了两种模拟拱坝径向横缝的力学模型,应用非直接对接的自由子结构方法,在模态子空间内建立了拱坝地震反应分析的非线性动力方程,提出了考虑动水压力影响的近似计算方法。最后通过算例说明不同径向横缝模型对拱坝地震反应的影响。 相似文献
47.
48.
49.
50.
射频连接器与射频电缆被广泛应用于军民品的通信设备中,其关键工序射频电缆芯线与射频连接器插针的连接常采用手钳式阻焊工具。由于射频电缆较细,手钳式阻焊工具在阻焊操作时,要求电装工双手不能抖动,否则易产生废品。通过对手钳式阻焊工具进行技术改进,重新设计了一种预压紧方式的阻焊装置,并通过试验确定了电阻焊接头的结构形式和尺寸,提高了手工阻焊成品率和生产效率,降低了对电装工的技能要求。 相似文献