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71.
针对现有 30kg 银锭浇铸工艺银锭产品存在四周棱角锋利、表面有缩坑、凹凸不平等问题,分析了银锭外观质量影响因素,开展了针对性优化改造。改造后,银锭表面无缩坑,底面、侧面平整,四周菱角圆滑,彻底解决了银锭外观质量问题。 相似文献
72.
Andrew Darnell Richard Wise John Quaranta 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2016,38(4):503-511
The Marcellus Shale formation contains large natural gas reserves, which are increasingly being extracted using horizontal drilling techniques. Concerns about environmental effects have prompted studies regarding Marcellus operations, including the safety of pits and impoundments containing frac fluids and freshwater. A subset of these structures in West Virginia was evaluated using a risk-based field data collection tool, which revealed recurring problems. A probability-based method was developed to determine the likelihood of these problems occurring in larger sample sizes. Applying this method to portfolios of pits and impoundments would benefit the industry by identifying areas of improvement for construction and inspection. 相似文献
73.
三门核电循环水泵房基坑为超深基坑(最深处为32.3m),处于基岩面埋藏较浅且上部覆盖较厚淤泥层和回填石层的特殊区域。本工程依据地层条件,将基坑边坡划分为完全基岩边坡、基岩埋深浅且无淤泥地层的边坡、基岩埋深较大且有较厚淤泥层的边坡3种类型。分别采用3种支护型式:放坡、排桩+岩锚、排桩+深搅重力墙+岩锚,有效解决了滨海软土区的地下水位高,淤泥质软土黏聚力及内摩擦角小,基坑侧壁受水平荷载大、易失稳等难题。典型断面计算结果表明,锚拉力最大为361.84kN;基坑侧壁最大水平位移为19.26mm,支护桩最大正负弯矩值为711.36kN·m和-787.52kN·m,基坑顶部最大沉降量为50mm,均满足设计与规范要求。 相似文献
74.
A series of coal-based activated carbons representing a wide range of mesopore content, from 16.7 to 86.9%, were investigated as an electrode in electric double layer capacitors (EDLCs) in 1 mol l−1 H2SO4 and 6 mol l−1 KOH electrolytic solutions. The activated carbons (ACs) used in this study were produced from chemically modified lignite, subbituminous and bituminous coals by carbonization and subsequent activation with steam. The BET surface area of ACs studied ranged from 340 to 1270 m2 g−1. The performance of ACs as EDLC electrodes was characterized using voltammetry, galvanostatic charge/discharge and impedance spectroscopy measurements. For the carbons with surface area up to 1000 m2 g−1, the higher BET surface area the higher specific capacitance (F g−1) for both electrolytes. The surface capacitance (μF cm−2) increases also with the mesopore content. The optimum range of mesopore content in terms of the use of ACs studied for EDLCs was found to be between 20 and 50%. A maximum capacitance exceeding 160 F g−1 and a relatively high surface capacitance about 16 μF cm−2 measured in H2SO4 solution were achieved for the AC prepared from a sulfonated subbituminous coal. This study shows that the ACs produced from coals exhibit a better performance as an electrode material of EDLC in H2SO4 than in KOH electrolytic solutions. For KOH, the capacitance per unit mesopore surface is slightly lower than that referred to unit micropore surface (9.1 versus 10.1 μF cm−2). However, in the case of H2SO4 the former capacitance is double and even higher compared with the latter (23.1 versus 9.8 μF cm−2). On the other hand, the capacitance per micropore surface area is the same in both electrolytes used, about 10.0 μF cm−2. 相似文献
75.
In the paper a change of material (mechanical) parameters of NiTi shape memory alloy subjected to ion implantation treatment is investigated. The spherical indentation tests in micro- and nano-scale and tension test have been performed to study an evolution of local superelastic effect in different volumes of nonimplanted and nitrogen ion implanted NiTi alloy. The differential scanning calorimetry has been applied to measure the change of characteristic temperatures due to ion implantation treatment. The structure of implanted material has been investigated using electron microscopy technique. It has been found that the ion implantation process changes the properties not only in a thin surface layer but also in bulk material. In the layer the pseudoelastic effect is destroyed, and in the substrate is preserved, however its parameters are changed. The characteristic phase transformation temperatures in substrate are also modified. 相似文献
76.
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78.
The present paper deals with the problem of assessing the fatigue lifetime of high‐strength steel wires containing corrosion pits, with this investigation being based on a large number of experimental data selected from the technical literature. To evaluate the stress concentration phenomena characterising corroded metallic wires, according to the state‐of‐the‐art knowledge, pits were modelled either as semi‐ellipsoidal cavities or as hemispherical notches. The stress concentration factors, Kt, associated with these simplified pit geometries were calculated numerically by solving numerous three‐dimensional FE models. Subsequently, the Kt values being determined according to this standard numerical procedure were post‐processed systematically to derive simple analytical solutions suitable for estimating, in situations of engineering interest, the stress concentration factors associated with pitting corrosion. Finally, after making some assumptions to derive the necessary fatigue properties, the Theory of Critical Distances was used in the form of the Point Method and the Line Method to reanalyse the literature data being collected. This systematic validation exercise allowed us to prove that the Theory of Critical Distances is successful also in assessing the fatigue lifetime of high‐strength metallic cables containing corrosion pits, with the obtained estimates falling within an error factor of 3. Therefore, as far as wires weakened by corrosion pits are concerned, it was demonstrated that the Theory of Critical Distances can be used to post‐process the local linear‐elastic stress fields when they are not only determined numerically but also estimated by using those standard analytical solutions which are strictly valid solely for conventional notches. 相似文献
79.
Fractal Characteristic of Pits Distribution on 304 Stainless Steel Corroded Surface and Its Application in Corrosion Diagnosis 总被引:1,自引:1,他引:1
梁成浩 《武汉理工大学学报(材料科学英文版)》2007,22(3):389-393
Electrochemical techniques and fractal theory were employed to study the corrosion behaviors and pits distribution characteristics on the corroded surfaces of 304 stainless steel exposed in FeCl3 solution. Fractal features of pits distribution over the corroded surfaces were observed and described by the fractal dimension. A 5-8-2 back-propagation (BP) artificial neural network model for the diagnoses of the pitting corrosion rate and pits deepness of 304 stainless steel under various conditions was developed by considering the fractal dimension as a key parameter for describing the pitting corrosion characteristics. The predicted results are well in agreement with the experimental data of pitting corrosion rate and pit deepness. The max relative errors between their experimental and simulation data are 6.69% and 4.62%, respectively. 相似文献
80.
本文介绍了电镀污水处理系统的组成及工作原理,给出了基于C8051F单片机监测控制系统的硬件及软件实现方案,该设计能够准确控制电镀污水处理的质量,运行结果表明该设计方案合理可靠。 相似文献