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排序方式: 共有846条查询结果,搜索用时 12 毫秒
91.
针对传统的Active Shape Model(ASM)方法的缺陷与不足,提出了几点改进的方法。传统的ASM方法利用人脸检测提供的初始位置进行特征搜索;在改进算法中,利用了瞳孔定位的方法进行初始化,并采取了边缘约束,自适应步长等改进方法,有效地改善了ASM方法的性能。实验结果表明,改进的ASM方法在准确性和鲁棒性上有较大提高。 相似文献
92.
建立正面碰撞乘员约束系统空间模型,通过实车碰撞试验验证了模型的正确性.结合均匀试验设计方法,分别建立3种人工神经网络拟合乘员伤害,网络结构经过优化和训练后使用遗传算法寻优,优化后的参数使得约束系统的保护性能得到显著改善.优化结果表明:RBF网络和GRNN网络对乘员约束系统的拟合效果较好,预测精度较高. 相似文献
93.
T接线路行波差动保护 总被引:1,自引:0,他引:1
由于传统的行波差动保护无法应用于T接输电线路,文中研究了一种新的行波差流表达式,理论推导了其在区内故障时的差流特征。为有效躲过线路空充等各种运行工况和区外故障引起的暂态不平衡行波差流,引入电流行波制动量,提出一种具有轻微比例制动特性的行波差动保护实用方案,在区内高阻故障时能够保持很高的灵敏度。理论分析及EMTP仿真计算表明,该方案灵敏度高,动作速度快,对装置采样和通信速率没有过高的要求,能够在现有技术条件下实现,具有较高的实用价值。 相似文献
94.
Stice Eric; Presnell Katherine; Lowe Michael R.; Burton Emily 《Canadian Metallurgical Quarterly》2006,18(1):95
In T. van Strien, R. C. M. E. Engels, W. van Staveren, and C. P. Herman's (see record 2006-03905-010) comment, they contested the conclusion that dietary restraint scales are invalid measures of acute dietary restriction (E. Stice, M. Fisher, & M. R. Lowe, 2004). The authors respond to their concerns and conclude that researchers should (a) not have to work this hard to find evidence that these scales correlate with dieting restriction, (b) not settle for scales with only weak validity, and (c) use scales that are consistently valid across settings. The authors also discuss new evidence that most weight loss dieters are not achieving the negative energy balance necessary for weight loss, which seems to explain why these scales do not correlate inversely with caloric intake and why those with the highest dietary restraint scores gain more weight over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
95.
基于对虚拟装配环境中装配零件的几何约束关系分析,分别对几何约束的判别、几何约束的确认和装配运动的定位导航进行了深入研究,通过共线约束和共面约束的产生,对装配零件的运动方向和运动空间进行约束,实现了产品虚拟装配过程中的快速精确定位,减轻了操作者虚拟装配操作的难度。 相似文献
96.
为了考察受轴向约束的型钢混凝土柱的耐火性能,以荷载比、偏心率和含钢率为参数,开展了7根轴向约束型钢混凝土柱的耐火试验。采用恒载升温模式,研究了火灾下受轴向约束的型钢混凝土柱的温度分布、位移、变形、耐火极限及破坏形态。试验结果表明:荷载比相同时,施加在轴心受压柱顶的竖向荷载大于偏心受压柱。对于轴心受压柱,高温下柱首先缓慢膨胀,然后逐渐压缩破坏;由于轴向约束分担了柱的竖向荷载,压缩变形随时间变化较为缓和,轴向约束延长了柱的耐火极限。对于偏心受压柱,高温下其膨胀变形大于轴心受压柱,且膨胀变形先增加再减小;轴向约束增加了柱的竖向荷载,缩短了柱的耐火极限。荷载比对轴向约束型钢混凝土柱耐火极限影响显著,荷载比越大,耐火极限越小。当荷载比不大于0.5时,偏心率越大,柱的耐火极限会相应增大。含钢率增加,会在一定程度上延长柱的耐火极限。 相似文献
97.
98.
Le Thi Nhu Trang 《热应力杂志》2018,41(4):418-438
Buckling, postbuckling, and nonlinear responses of composite cylindrical panels reinforced by single-walled carbon nanotubes (CNTs), supported by an elastic foundation, exposed to elevated temperature and axially compressed by uniform load are investigated in this article. Distribution of CNTs is uniform or graded in the thickness direction and the effective properties of CNT-reinforced composite are assumed to be temperature dependent, and are estimated by extended rule of mixture through a micromechanical model. Governing equations are established based on thin shell theory taking von Kármán–Donnell nonlinearity, initial geometrical imperfection, Pasternak-type elastic foundation and tangential elastic constraints of boundary edges into consideration. Approximate solutions of deflection and stress functions are assumed to satisfy simply supported boundary conditions, and Galerkin method is applied to derive explicit expressions of load–deflection relation from which critical buckling loads can be obtained. Unlike works in the literature, the present study accounts for elasticity of tangential restraint of two unloaded straight edges in model of cylindrical panel. The study also gives conditions for which bifurcation type buckling response can occur and novel findings in numerical examples. 相似文献
99.
Rajkishore Nayak Rajiv Padhye Kanesalingam Sinnappoo Lyndon Arnold Bijoy Kumar Behera 《Textile Progress》2013,45(4):209-301
In recent years, safety systems such as seat belts and airbags have been one of the fast-growing sectors within the automotive industry. Seat belts and airbags have made driving substantially safer since their introduction. Airbags are safety systems used to cushion the driver or passenger during a collision and reduce bodily injuries. The technology involved in the manufacturing and working of airbags is complex. Since the early stages of development, airbag technology has been undergoing continual evolution in terms of design, materials and performance. Airbags are typically made from woven fabric, which may be coated or uncoated but must be impermeable to gases and flame resistant. In terms of their operation, modern airbags are smart restraint systems, which can tailor the deployment of the airbag according to the crash severity, body size of the occupant and proximity of the occupant to the airbag system prior to deployment. The future of airbags is extremely promising because there are many diverse applications ranging from motorcycle helmets to aircraft seating. In this article, an outline is given of the historical development of airbags and their value in saving lives is illustrated by supporting statistical data. The essential parameters required for airbag yarn and fabric components are discussed in detail. In addition, the processes involved in the manufacture, assembly and testing of airbag systems are explained. The mechanisms and chemical reactions involved in the deployment of different types of airbags are also discussed, and recent developments in airbag design and their possible future applications are reported. 相似文献
100.