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AbstractIn order to study the effect of the phase boundary between austenite and ferrite phases on the nucleation and propagation behaviours of microcracks in nuclear grade Z3CN20-09M stainless steel, an in situ scanning electron microscopy (SEM) tensile technique was used to study the deformation, nucleation and propagation of microcracks during tension. The fractography was subsequently observed by SEM. The results indicated that, during tension, the deformation first occurred in the austenitic grains followed by in the ferrite, and the microcracks were subsequently preferential formed at the phase boundary between austenite and ferrite phases. In the case of the phase boundary perpendicular to the loading direction, microcracks nucleated and subsequently propagated along the phase boundary. In the case of the phase boundary parallel to the loading direction, microcacks nucleated at the intersection of slip bands and the phase boundary and propagated perpendicularly to the phase boundary, resulting in deflection of the main crack. The phase boundary played a hindrance effect on crack propagation. 相似文献
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Abstract. We study an at‐most‐one‐change time‐series model with an abrupt change in the mean and dependent errors that fulfil certain mixing conditions. We obtain confidence intervals for the unknown change‐point via bootstrapping methods. Precisely, we use a block bootstrap of the estimated centred error sequence. Then, we reconstruct a sequence with a change in the mean using the same estimators as before. The difference between the change‐point estimator of the resampled sequence and the one of the original sequence can be used as an approximation of the difference between the real change‐point and its estimator. This enables us to construct confidence intervals using the empirical distribution of the resampled time series. A simulation study shows that the resampled confidence intervals are usually closer to their target levels and at the same time smaller than the asymptotic intervals. 相似文献
75.
《Journal of Building Performance Simulation》2013,6(2):105-124
This article investigates how to use UK probabilistic climate-change projections (UKCP09) in rigorous building energy analysis. Two office buildings (deep plan and shallow plan) are used as case studies to demonstrate the application of UKCP09. Three different methods for reducing the computational demands are explored: statistical reduction (Finkelstein-Schafer [F-S] statistics), simplification using degree-day theory and the use of metamodels. The first method, which is based on an established technique, can be used as reference because it provides the most accurate information. However, it is necessary to automatically choose weather files based on F-S statistic by using computer programming language because thousands of weather files created from UKCP09 weather generator need to be processed. A combination of the second (degree-day theory) and third method (metamodels) requires only a relatively small number of simulation runs, but still provides valuable information to further implement the uncertainty and sensitivity analyses. The article also demonstrates how grid computing can be used to speed up the calculation for many independent EnergyPlus models by harnessing the processing power of idle desktop computers. 相似文献
76.
本文通过对糠醛装置换热设备腐蚀的情况、机理进行分析,尝试采用低合金钢09Cr2AlMoRE来提高换热设备的抗腐蚀能力,效果很好。 相似文献
77.
从134株海洋微生物中筛选得到放线菌JWH-09,其发酵代谢产物具有较好的抗植物病原真菌活性.根据生物活性跟踪测试,采用硅胶柱层析、薄层层析以及制备高效液相色谱等技术对JWH-09发酵产物中的抗菌活性组分进行分离纯化,得到了一种抗真菌活性化合物JWH-09-A,经ESI-MS、EI-MS、1H NMR、13C NMR、2D NMR等谱图分析,确定该活性物质的结构为1-菲羧,1,2,3,4,4a,9,10,10a-八氢-1,4a-二甲基-7-(1-甲基乙基),俗名脱氢松香酸(dehydroabietic acid).经盆栽试验证明该化合物对水稻纹枯病、黄瓜白粉病和灰霉病具有较好的防治效果. 相似文献
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采用7A09铝合金过热处理工艺实验,研究其过热显微组织形态;采用4种锻造温度(440、460、480、500℃)对应3种变形程度ε(45%、68.3%、76.7%)进行了锻造实验,分析了锻造温度和变形程度对锻后晶粒组织的影响。过热处理工艺实验研究表明,随着加热温度的升高、保温时间的延长,晶粒变大;在加热温度440℃保温时间6 h后锻件的显微组织图上出现了织构组织,在加热温度500℃保温时间10 h后过烧现象明显;锻造工艺实验研究表明,获得锻后晶粒细小组织的最佳锻造工艺参数是锻造温度440℃和变形程度76.7%。 相似文献
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Principal manifolds serve as useful tool for many practical applications. These manifolds are defined as lines or surfaces passing through “the middle” of data distribution. We propose an algorithm for fast construction of grid approximations of principal manifolds with given topology. It is based on analogy of principal manifold and elastic membrane. First advantage of this method is a form of the functional to be minimized which becomes quadratic at the step of the vertices position refinement. This makes the algorithm very effective, especially for parallel implementations. Another advantage is that the same algorithmic kernel is applied to construct principal manifolds of different dimensions and topologies. We demonstrate how flexibility of the approach allows numerous adaptive strategies like principal graph constructing, etc. The algorithm is implemented as a C++ package elmap and as a part of stand-alone data visualization tool VidaExpert, available on the web. We describe the approach and provide several examples of its application with speed performance characteristics. 相似文献