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91.
92.
王绍强 《山东建筑工程学院学报》1990,(2)
本文深入分析了古城曲阜的历史发展和特色,认为这座独具特色的历史文化名城的个性特征,表现为:悠久的历史文化、独特的城市格局、丰富的文化遗存和古朴的城市风貌等方面。并深入探讨和提出了古城保护规划的指导思想和各项保护措施。 相似文献
93.
介绍了太原汾河景区的设计概况,分析了河流在防洪、水资源以及水景三方面功能的合理利用,保持了城市景区良好的自然生态,在水资源的综合利用方面取得了显著效果。 相似文献
94.
Yusong Wang Ana Belén Serrano Kadir Sentosun Sara Bals Luis M. Liz‐Marzán 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(34):4314-4320
Surface chemistry plays a pivotal role in regulating the morphology of nanoparticles, maintaining colloidal stability, and mediating the interaction with target analytes toward practical applications such as surface‐enhanced Raman scattering (SERS)‐based sensing and imaging. The use of a binary ligand mixture composed of 1,4‐benzenedithiol (BDT) and hexadecyltrimethylammonium chloride (CTAC) to provide gold nanostars with long‐term stability is reported. This is despite BDT being a bifunctional ligand, which usually leads to bridging and loss of colloidal stability. It is found however that neither BDT nor CTAC alone are able to provide sufficient colloidal and chemical stability. BDT‐coated Au nanostars are additionally used as seeds to direct the encapsulation with a gold outer shell, leading to the formation of unusual nanostructures including semishell‐coated gold nanostars, which are characterized by high‐resolution electron microscopy and electron tomography. Finally, BDT is exploited as a probe to reveal the enhanced local electric fields in the different nanostructures, showing that the semishell configuration provides significantly high SERS signals as compared to other core–shell configurations obtained during seeded growth, including full shells. 相似文献
95.
96.
测量高斯光分布半宽度的光电共轭方法 总被引:2,自引:2,他引:0
测量光电信号与参考光电信号来自同一光电器件,形成一对共轭函数。调整参考光电信号 放大器的正电源电平,使之等于测量信号的峰值,此时两函数共轭交点之间的距离即对应于光束的半宽。测量过程中,被测光束能量的缓慢变化并不对结果造成影响,因此稳定性较好,实验重复精度至±2mm。 相似文献
97.
Sixteen years of research on the properties of 'contact spots' of ductile materials in 'adhesive' wear are surveyed. They are the locations (typically occupying less than 1% of the macroscopic area of contact) at which solids ale in load-bearing contact during wear. Their properties determine the coefficient of friction, and friction and Joule heat are generated at them. It was found that the mechanical behavior of contact spots is governed by ordinary dislocation plasticity. They remain elastic if the local pressure falls short of the indentation hardness of the softer side. In that case (almost) no wear occurs. Elastic contact spots are promoted by light loads and fine polishing. Ordinarily, wear particles are detached through tangential shearing-off where, statistically, the two sides at contact spots momentarily interlock. The Holm-Archard wear 'law' is a simple direct result of this mechanism. However, quite typically the bulk of sliding takes place within adsorbed moisture films which are ubiquitous in our daily surroundings. Outside of contact spots the adsorbed moisture behaves much like ordinary water. At the typical contact spot the moisture is squeezed down to but two monomolecular layers; and the relative motion between sliding solids overwhelmingly takes place between these. This causes the prevalence of friction coefficients about μ 0.3 in our surroundings. The complex behavior of the adsorbed water can cause stick-slip. As water is desorbed at 170 °C, the determination of flash temperatures at contact spots is critical. A corresponding theory was developed and verified in connection with experiments on graphite lubrication which depends on the presence of adsorbed moisture. Further, plastic contact spots and solid lubrication have been simulated by means of a Bridgman anvil apparatus. The results show that the same work-hardening behavior applies at contact spots as known from the bulk. They also proved that at contact spots intimate mixing of the materials of the two sides gives rise to a finely mixed layer which can amorphize by much the same dislocation mechanism as is believed to cause melting. The amorphous material promptly recrystallizes at least in the Cu-Ag system. It is proposed to try and inhibit such recrystallization by selected lubricants, so as to promote beneficial wear-resistant tribo-films. 相似文献
98.
测量高功率激光束衍射光斑阵列位置的图象处理方法 总被引:3,自引:0,他引:3
介绍了测量高功率激光束射光斑阵列的各光斑中心位置的计算机图象处理方法。讨论了TIFF图象格式的全用技巧,利用灰度级确定各衍射光斑光强中心以及去除噪声光点的计算机处理方法,用计算机软件实现了常规Hartmann-Shack传感器中子透镜阵列的子光束聚焦过程。 相似文献
99.
讨论环形孔径高斯光束的远场光斑能量分布,并给出拟合表达式。首先推导光束没有抖动时远场光斑的光能分布表达式,然后研究各种不同中心遮拦和不同光束截断比,在有以及没有激光束抖动的情况下,对高斯光束的远场环围能量分布变化的影响。 相似文献
100.