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排序方式: 共有162条查询结果,搜索用时 15 毫秒
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为探究不同土性地基的SSI效应对层间隔震结构影响机理与动力响应规律,选取一个典型层间隔震结构,对其简化并制作缩尺模型,采用振动台试验的方法,分别在硬土、软土这两种地基上单向输入4条地震波来研究模型的动力响应。结果表明:土体具有明显的放大效应,随着地基土由硬变软,隔震结构周期延长倍数降低。隔震结构在硬土地基上能发挥较好的减震效果,而软土地基上减震效果明显减弱。软土地基上塔楼的动力响应较硬土地基增大,塔楼容易成为薄弱部位,其抗震设计应重点关注。 相似文献
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The preparation of defect-free MoS2 nanosheets is a key challenge and essential for practical applications. Herein the dodecanethiol was firstly performed as the antioxidant and surface modifier to produce the defect-free MoS2 by direct ultrasonication of bulk MoS2 in N,N-dimethylformamide. Incorporating defect-free MoS2 into polyethylene obviously improved the properties of PE/MoS2 nanocomposites. For crystallization under quiescent condition, the half crystallization time (t0.5) of nanocomposites containing 0.2 wt% MoS2 was reduced by 87.0% compared to that of neat PE. A 54.3 °C increase in the temperature of maximum weight loss (Tmax) was observed by inclusion of as low as 0.7 wt% defect-free MoS2 nanosheets. In addition, the uniformly distributed MoS2 can considerably improve the mechanical properties of composites. These observations suggest that the robust nature, dramatic barrier action of defect-free MoS2 and the strong nanosheets/matrix interfacial adhesion would be the motivation to improve the performance of the polymeric nanocomposites. 相似文献
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对室内岩石声发射试验的事件率与应力关系曲线、事件时序分布进行了分析,研究了岩体破裂变形过程与声发射事件时序分布特征之间的相关规律。现场监测结果表明,岩体破裂变形过程中的声发射信号是随机的,非周期性的,随着地质环境等改变而改变;岩体声发射事件主频时序参数突变,由小突然增大,或是在连续增加时突然减少,都是临近破坏的征兆,可作为预测、预报岩体破裂失稳的依据。 相似文献
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《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1987,257(1):69-70
A simple apparatus is described that produces hard carbon coatings by accelerating ions produced by a carbon arc operating in vacuum. Coatings up to 1.1 μm thick have been produced on a variety of metals and semiconductors. 相似文献
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《Composite Structures》1987,8(2):85-103
It is shown that the effect of stress discontinuities from ply-to-ply must be taken into account when curvature terms are included along with shear deformation in the buckling analysis of rectangular, symmetrically-laminated plates. Such ply-stress discontinuities lead to curvature terms in the governing equations which differ considerably from those derived for homogeneous plates. Critical buckling loads are determined for orthotropic laminates subjected to biaxial inplane loading and for cylindrical bending of anisotropic plates subjected to uniaxial compression loading. Simply-supported boundary conditions are considered in conjunction with the rectangular, orthotropic laminate, while simply-supported and clamped boundaries are considered for the case of cylindrical bending of anisotropic plates. Numerical results indicate that the curvature terms have little effect on critical buckling loads for the laminates investigated. The effect of transverse shear deformation is shown to depend on the degree of boundary constraint, laminate stacking geometry, and inplane load ratio. 相似文献
9.
《Journal of Constructional Steel Research》2012,68(12):1912-1921
This paper describes a full scale arch type steel highway bridges, its finite element modelling and Operational Modal Analysis. Eynel Highway Bridge which has arch type structural system with a total length of 336 m and located in the Ayvacık county of Samsun, Turkey is selected as a case study. The bridge connects the villages which are separated with Suat Uğurlu Dam Lake. The three dimensional finite element model is constructed using project drawings and an analytical modal analysis is then performed to generate natural frequencies and mode shapes in the three-orthogonal directions. The ambient vibration tests on the bridge deck under natural excitation such as traffic, human walking and wind loads are conducted using Operational Modal Analysis. Sensitive seismic accelerometers are used to collect signals obtained from the experimental tests. To obtain experimental dynamic characteristics, two output-only system identification methods are employed namely, Enhanced Frequency Domain Decomposition method in the frequency domain and Stochastic Subspace Identification method in time domain. The correlation between the finite element model and experimental results is studied. Good agreement is found between dynamic characteristics in the all measurement test setups performed on the bridge deck. It is demonstrated that the ambient vibration measurements using Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are enough to identify the most significant modes of steel highway bridges. It is seen that there are some differences between analytical and experimental natural frequencies and experimental natural frequencies are generally bigger than the others. 相似文献
10.
Natural stones are generally used as building materials for construction and decoration. Determining the deteriorations of stones after freeze–thaw cycles is important subject for natural building stones used in cold regions exposed excessive freezing and thawing during the year. Freeze–thaw test is conducted for determining the deteriorations of stones due to freeze–thaw cycling. The percentage loss in uniaxial compression strength is an important parameter indicating these deteriorations. However, it is extremely laborious and time consuming tests. Because of this, predicting the percentage loss values in uniaxial compression strengths from intact rock properties was the purpose of this paper. Freeze–thaw tests were applied on nine limestone samples selected from different cold regions of Turkey. All of them except two samples were found to be suitable for use in cold regions. A statistical model was developed for predicting the percentage loss values in uniaxial compression strength from intact tests of impact strength, modulus of elasticity and water absorption. This model equation is very reliable (R2 = 0.95) and can be very useful for predetermination of uniaxial compression strengths of limestones after freeze–thaw test without testing. 相似文献