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以高性能混凝土用胶凝材料为研究对象,研究了粉煤灰、矿粉在不同养护湿度和温度下对水泥浆体变形性能的影响规律。结果表明:饱水养护时,粉煤灰的掺入降低了水泥浆体的水养膨胀变形;养护温度升高、粉煤灰掺量增加,水泥浆体水养膨胀变形降低幅度增大,但不同水养温度下掺入矿粉对水泥浆体膨胀变形无明显影响;密封养护时,掺入粉煤灰可有效抑制水泥浆体的自收缩,但矿粉掺入会增大水泥浆体自收缩;干燥养护时,掺入粉煤灰对水泥浆体有一定的减缩作用,而矿粉的掺入会增大水泥浆体的干燥收缩。 相似文献
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《矿业科学技术学报(英文版)》2021,31(3):495-505
Large and super-large section chamber groups in coal mines are frequently affected by dynamic loads resulting from production activities such as roadway driving and blasting. The stability of the surrounding rock is poor, and it is difficult to control. In this paper, a similar simulation test was used to study the deformation and evolution laws of the surrounding rock of a triangle-shaped chamber group under different dynamic loads. The results showed that under dynamic loading, the vertical stress of the surrounding rock of the chamber group increased in an oscillatory form. The maximum stress concentration coefficient reached 4.09. The damage degree of the roof was greater than that of the two sides. The deformation of the roof was approximately 1.2 times that of the two sides. For the chamber closer to the power source, the stress oscillation amplitude of the surrounding rock was larger, and the failure was more serious. The force of the anchorage structure showed a phased increasing characteristic; additionally, the force of the anchorage structure on the adjacent side of the chambers was greater than that on the other side. This study reveals the deformation and failure evolution laws of the surrounding rock of large section chamber groups under dynamic loading. 相似文献
4.
Uniaxial tensile tests were carried out at room temperature (RT) and 250 °C, respectively, to investigate the effect of short-range ordering (SRO) on the mechanical properties and deformation micromechanism of fine-grained (FG) Cu-Mn alloys with high stacking fault energy. The results show that at RT, with the increase in SRO degree, the strength of FG Cu-Mn alloys is improved without a loss of ductility, and corresponding deformation micromechanism is mainly manifested by a decrease in the size of dislocation cells. In contrast, at a high temperature of 250 °C, the SRO degree becomes violently enhanced with increasing Mn content, and the deformation microstructures thus transform from dislocation cells to planar slip bands and even to deformation twins, significantly enhancing the work hardening capacity of the alloys and thus achieving a better strength-ductility synergy of FG Cu-Mn alloys. 相似文献
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采用Gleeble-1500热力模拟机对铸态Ti-48Al-2Nb-2Cr合金进行高温变形热压缩试验,变形温度范围为1050~1200℃,应变速率范围为0.001~0.1s^-1,压缩变形量为60%。研究该合金高温变形温度和应变速率与流变应力之间的关系,计算了合金激活能,并建立了Ti-48Al-2Nb-2Cr合金的Arrhenius本构模型和多元线性回归的本构模型。结果表明,该合金的激活能随温度升高和应变速率增大而增大;Arrhenius本构模型的相关系数为0.98228,平均相对误差为9.97%,相对误差在10%以内的点只占62.0%;而采用多元线性回归本构模型的相关系数为0.99566,平均相对误差为4.76%,相对误差在10%以内的点占92.6%,本构精度较高。 相似文献
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《Mechatronics》2015
Taking into account the effect of structural compliance, inverse dynamics of the active over-constrained parallel manipulator 6PUS–UPU with five degrees of freedom is solved in this article. Firstly, the relationship between driving forces and actuated force screws of each limb is derived. Then the coordination of elastic deformation between limbs which consider the effect of gravity and inertia is acquired. Finally the unique solution of driving forces for the active over-constrained parallel manipulator is derived by incorporating the force equilibrium equation of the moving platform. To validate the theoretical derivation, dynamics simulation model of manipulator based on rigid–flexible mixed structure is shown and numerical examples are given. Comparison with the traditional method of dynamics based on pseudo-inverse is also made. Finally, a feasible experimental method, as an effective test to the theoretical calculation, is proposed and applied on the prototype. 相似文献
8.
环境复杂"三下"矿床开采引发的岩层变形威胁到地表建构筑物的安全。以典型的"三下"矿山金口岭深部矿体开采为例,采用定量与定性相结合的方式,对金口岭深部矿体上行式开采25组不同采场结构参数下地表变形特性进行了数值模拟。结果表明,上行式盘区点柱式上向分层充填采矿法对保护地表建构筑物安全极为有利,当采用盘区长度为70 m、顶柱厚度为6 m、间柱宽度为6 m、点柱尺寸为4 m×4 m、点柱间距为12 m的结构参数时,地表倾斜值为-0.18 mm/m,曲率值为-0.003×10-3/m,水平变形值为0.11 mm/m,参照《GB 50771—2012有色金属采矿设计规范》,均小于地表建构筑物所允许的变形值。 相似文献
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采用Gleeble-3800热模拟试验机进行了DIN 1.2738塑料模具钢(/%:0.35~0.46C,0.20-0.40Si,1.30~1.60Mn,1.80~2.20Cr,0.90~1.20Ni,0.15~0.23Mo)的热压缩实验,获得了该钢在850~1250℃、应变速率在0.01~30的应力-应变曲线。基于得到的热变形数据,建立了该钢的峰值应力以及应变补偿的热变形本构方程和热加工图,并结合热加工图的结果分析了该钢合理的热加工参数范围。结果表明,DIN 1.2738钢的热变激活能为354.21 kJ/mol,利用建立的应变补偿的双曲正弦本构方程可对塑料模具钢的热变形曲线进行准确预测,通过加工图的分析可得DIN 1.2738塑料模具钢的最佳的热变形工艺参数范围为:(1)温度950~1 150℃,应变速率0.01~0.7 s-1;(2)温度1170~1200℃,应变速率0.01~1 s-1。 相似文献
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