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71.
AbstractCryptographic attacks are typically constructed by black-box methods and combinations of simpler properties, for example in [Generalised] Linear Cryptanalysis. In this article, we work with a more recent white-box algebraic-constructive methodology. Polynomial invariant attacks on a block cipher are constructed explicitly through the study of the space of Boolean polynomials which does not have a unique factorisation and solving the so-called Fundamental Equation (FE). Some recent invariant attacks are quite symmetric and exhibit some sort of clear structure, or work only when the Boolean function is degenerate. As a proof of concept, we construct an attack where a highly irregular product of seven polynomials is an invariant for any number of rounds for T-310 under certain conditions on the long term key and for any key and any IV. A key feature of our attack is that it works for any Boolean function which satisfies a specific annihilation property. We evaluate very precisely the probability that our attack works when the Boolean function is chosen uniformly at random. 相似文献
72.
A. Reddy D. B. Hovis A. H. Heuer A. P. Paulikas B. W. Veal 《Oxidation of Metals》2007,67(3-4):153-177
Synchrotron radiation has been used to study in situ the evolution of growth strains in an Al2O3 scale (the so-called TGO or thermally grown oxide) on a model bond-coat alloy (Ni-19.7 Cr-19.2 Al-0.1 Y at.%) as oxide growth
proceeds in air at 950–1100°C, and the changes in these strains due to thermal-expansion mismatch as the samples are cooled.
Tensile growth stresses develop in the oxide scales during the initial stages of oxidation, a result of initially formed transition
aluminas converting to the stable α-Al2O3 form, but large residual compressive stresses are present at room temperature due to thermal-expansion mismatch between the
scale and the bond-coat. 相似文献
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Sorin-Cristian Vlădescu Alessandra Ciniero Khizer Tufail Arup Gangopadhyay Tom Reddyhoff 《摩擦学汇刊》2018,61(3):522-531
It has recently been shown that rectangular surface pockets are effective in reducing friction in a piston–liner type contact, providing that they are oriented with their long axis transverse to the sliding direction so that entrained features fit completely within the contact area (Vl?descu, et al., Tribology International, 82, 28–42, 2015; Vl?descu, et al., Tribology International, 115, 140–153, 2017). The aim of the current study was to identify the optimal geometric parameters of theses rectangular features. To do this, a friction rig that simulated a piston–liner contact under highly controlled conditions was used to test a series of textured specimens with pockets of different depth, breadth and density. Each of these geometric parameters was varied and tested independently, while keeping the other two constant. Experimental conditions were set in order to place the contact in different lubrication regimes.Results were analyzed to determine a set of criteria for the optimum pocket geometry; however, this was shown to change depending on the test conditions and should therefore be adjusted depending on the position along the stroke. Specifically, at low speed when the contact is operating under boundary lubrication, pockets should be deep, wide, and densely spaced. This confirms recent findings, which suggested that, in this regime, pocket volume is often a more critical parameter than depth, width, or spacing individually. Conversely, under mixed lubrication toward the transition to the full film regime, pockets should be narrow and sparsely spaced. These results also explain the difficulties encountered in several previous studies that attempted to define a single optimum pocket geometry.Finally, the impact of pocket position relative to reversal was assessed for various lubrication conditions. This revealed how pockets should be placed close to, but not directly at, top and bottom dead center to provide a beneficial squeeze film, which is present at reversal. 相似文献
75.
More realistic and useful models of piston ring lubrication can only be achieved if there is a better understanding of the complex mechanisms by which oil flows in this region of the engine. The volume of oil in the piston assembly and its residence time in this high-temperature environment are crucial in determining the quantity and quality of oil available to lubricate the piston rings. Typically models of piston ring pack lubrication focus upon the oil flowing through the piston ring/cylinder interface. However, a number of additional oil flow paths and interactions with gas blow-by have been observed in the piston assembly. This paper presents a model that includes a number of such mechanisms and evaluates their influence on the lubrication of a piston ring pack from a typical automotive gasoline engine. The results indicate that such additional mechanisms are needed to give improved predictions of oil transport they highlight the relative importance of several of these mechanisms and help guide future research. 相似文献
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白河为黄河源区典型弯曲河流,2016年和2017年对白河9处典型河湾进行了考察采样。分析表明,白河河湾凸岸植被呈环形条带状分布,一般有2~3个植被群落;湾顶从前至后的树木尺寸显示出明显的由低矮到高大的梯度变化。对凸岸树芯和圆盘样本进行年轮分析,获取了树木的分布和树龄数据,提出了通过树木年轮和距离计算河湾迁移速率的方法。通过绘制树龄分布云图找出关键样本,测算白河河湾迁移速率为0.38~6.1 m/a,与遥感影像估算得出的迁移速率基本一致。对白河河湾迁移速率与水流流速、河宽、滩高等数据进行回归分析,建立多元线性回归模型,结果表明水流流速和比降是白河河湾迁移速率的主要影响因素,迁移速率与流速和比降均成正比。 相似文献
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80.
Euan Smith Rodney L. Heckaman Karl Lang John Penczek Johan Bergquist 《Journal of the Society for Information Display》2020,28(6):548-556
Historically displays used three colorants in an additive system. During that time, the CIE chromaticity diagram adequately illustrated color capability. Modern displays are not constrained by this additive architecture, and the diagram can fail in its purpose. This is demonstrated by analysis and a large number of display measurements. A device‐independent methodology using CIE 1976 L*a*b* color gamut volume is described that provides a robust means to determine the size of the color gamut. This methodology is then extended to the ‘gamut rings’ diagram as a solution for visualizing color capability that directly correlates to color gamut volume. It is further shown how the methodology can be applied to determine the intersection between two gamut volume boundaries. 相似文献