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141.
The magneto-mechanical memory (MMM) method, that is often referred to as the metal magnetic memory method, has been reported to be a non-destructive testing technique capable of quantifying stress concentrations and detecting defects in ferromagnetic materials. The underlying mechanism behind MMM has been explained in the literature, but the sensitivity to stress concentration has not been satisfactorily investigated. In this paper, both the normal and tangential components of the stress-induced MMM signal were measured by permanently installed magnetic sensor arrays on specimens made from three grades of L80 alloy steel and 20 other structural steels; tests were also carried out on a pipe made from the 4140-L80 steel. As expected, the stress history affects the MMM signal, but the experimental results show that significant irreversible change of magnetization always occurs only in the first cycle of loading regardless whether the deformation is purely elastic or partially plastic. If the peak stress level is increased at a given point during cycling, the immediately following next cycle acts as a new “first” cycle at that peak stress level and causes additional significant irreversible change of magnetization, but there is no evidence that plastic deformation might build up a cumulative magnetization. The MMM effect is very small in the steel samples tested, indicating that it will not be useful in field applications. In un-notched specimens the irreversible change in magnetization caused a proportional change in the measured external magnetic field on the order of only 5–10 A/m, while in the case of notched specimens the leakage field was on the order of 30–60 A/m. 相似文献
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Md Anisur Rahman Yun-Zhuo Lu Qiang Luo Shou-Jiang Qu Feng-Xia Ye Yi-Xuan Wu Jun Shen 《金属学报(英文版)》2016,29(9):834
Fe_(43)M_5Cr_(15)Mo_(14)C_(15)B_6Y_2 (M=Mn,Co,Ni,and Cu in at.%)bulk metallic glasses(BMGs)are synthesized using the suction casting technique,and the glass-forming ability(GFA),microstructure,and thermal and magnetic properties of these glasses are extensively examined using X-ray diffraction,differential scanning calorimeter,and vibrating sample magnetometer techniques.Among the four BMG alloys,Fe_(43)Ni_5Cr_(15)Mo_(14)C_(15)B_6Y_2 exhibits the lowest coercivity and the highest saturation magnetization,Curie temperature,effective magnetic moment,and GFA.By contrast,Fe_(43)Mn_5Cr_(15)Mo_(14)C_(15)B_6Y_2 presents the poorest magnetic properties,such as the highest coercivity and the lowest saturation magnetization,Curie temperature,and effective magnetic moment.Fe_(43)Cu_5Cr_(15)Mo_(14)C_(15)B_6Y_2 demonstrates the lowest thermal stability and GFA.The observed thermal,structural,and magnetic properties of these BMG alloys are discussed in terms of the kinetics of BMG synthesization and the formation of different ferromagnetic,ferrimagnetic,and antiferromagnetic phases. 相似文献
144.
阐述了电压互感器实际运行中,磁化曲线对于判断电压互感器的运行状态非常重要,通过对磁化曲线的分析,可以知道电压互感器运行在哪个工作点,从而可以推出电压互感器是否处于最佳运行状态,以及运行中可能出现哪些问题。介绍了两种获得电压互感器的磁化曲线的方法,目的在于通过磁化曲线判断吨压互感器的工作点,对实际运行中电压互感器的状态分析起到积极的意义。 相似文献
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Boris B. Krichevtsov Sergei V. Gastev Sergey M. Suturin Vladimir V. Fedorov Alexander M. Korovin Viktor E. Bursian 《Science and Technology of Advanced Materials》2013,14(1):351-363
AbstractThin (4–20 nm) yttrium iron garnet (Y3Fe5O12, YIG) layers have been grown on gadolinium gallium garnet (Gd3Ga5O12, GGG) 111-oriented substrates by laser molecular beam epitaxy in 700–1000 °C growth temperature range. The layers were found to have atomically flat step-and-terrace surface morphology with step height of 1.8 Å characteristic for YIG(111) surface. As the growth temperature is increased from 700 to 1000 °C the terraces become wider and the growth gradually changes from layer by layer to step-flow regime. Crystal structure studied by electron and X-ray diffraction showed that YIG lattice is co-oriented and laterally pseudomorphic to GGG with small rhombohedral distortion present perpendicular to the surface. Measurements of magnetic moment, magneto-optical polar and longitudinal Kerr effect (MOKE), and X-ray magnetic circular dichroism (XMCD) were used for study of magnetization reversal for different orientations of magnetic field. These methods and ferromagnetic resonance studies have shown that in zero magnetic field magnetization lies in the film plane due to both shape and induced anisotropies. Vectorial MOKE studies have revealed the presence of an in-plane easy magnetization axis. In-plane magnetization reversal was shown to occur through combination of reversible rotation and abrupt irreversible magnetization jump, the latter caused by domain wall nucleation and propagation. The field at which the flip takes place depends on the angle between the applied magnetic field and the easy magnetization axis and can be described by the modified Stoner–Wohlfarth model taking into account magnetic field dependence of the domain wall energy. Magnetization curves of individual tetrahedral and octahedral magnetic Fe3+ sublattices were studied by XMCD. 相似文献
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149.
CY Kung SL Young HZ Chen MC Kao L Horng YT Shih CC Lin TT Lin CJ Ou 《Nanoscale research letters》2012,7(1):372
ABSTRACT: One-dimensional pure zinc oxide (ZnO) and Y-doped ZnO nanorod arrays have been successfully fabricated on the silicon substrate for comparison by a simple hydrothermal process at the low temperature of 90°C. The Y-doped nanorods exhibit the same c-axis-oriented wurtzite hexagonal structure as pure ZnO nanorods. Based on the results of photoluminescence, an enhancement of defect-induced green-yellow visible emission is observed for the Y-doped ZnO nanorods. The decrease of E2(H) mode intensity and increase of E1(LO) mode intensity examined by the Raman spectrum also indicate the increase of defects for the Y-doped ZnO nanorods. As compared to pure ZnO nanorods, Y-doped ZnO nanorods show a remarked increase of saturation magnetization. The combination of visible photoluminescence and ferromagnetism measurement results indicates the increase of oxygen defects due to the Y doping which plays a crucial role in the optical and magnetic performances of the ZnO nanorods. 相似文献
150.
磁化曲线的连续可导拟合方法 总被引:1,自引:0,他引:1
为了满足磁场储能迭代计算的需要,提出了磁化曲线的连续可导拟合方法。磁化曲线具有高度非线性,难以用一个函数来逼近,根据其特点,提出了线性插值和二次插值相结合的方法,分为三段来拟合。根据曲线连接点处的约束关系,通过求解约束方程获得拟合函数的待定系数,保证了整条曲线的连续可导。由拟合结果给出了磁导率随磁通密度的函数关系及其导函数关系。最后给出了一个具体的拟合算法实例,验证了拟合精度。 相似文献