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81.
82.
A. Goldman 《Journal of Materials Engineering and Performance》1995,4(4):395-400
Iron-based metallic strip materials such as iron, silicon-iron, and amorphous metal are used for low frequency (50–60 Hz.
line) power applications. Low-loss Nickel-based alloys as high permeability strip or insulated powder cores are the choices
for stable, low-level higher frequency applications. Iron-based powder cores offer low cost as power supply filter chokes.
Ceramic ferrites combine highest frequency operation with low cost and reduced component size as transformers and chokes in
telecommunication and high frequency power supply applications. 相似文献
83.
Reinhold Ludwig Sergey Makarov Diran Apelian 《Journal of Nondestructive Evaluation》1998,17(3):153-166
This paper investigates electrostatic voltage distributions around a surface-breaking flaw due to an injected current of known
strength. The direct 3-D solution of the voltage behavior over the flawed surface is obtained numerically by the use of a
boundary integral formulation. A novel iteration method is applied to solve the resulting electrostatic integral equation
for the unknown surface voltage distribution. In addition to investigating the sensitivity of different flaw sizes to the
observed surface voltage distribution, important issues such as suitable probe spacing and current flow orientation are studied.
For sufficiently small surface-breaking flaws, a simple image source model is developed to evaluate the voltage response of
hairline cracks. The model is tested by comparing it with the developed numerical solution. Experiments aimed at establishing
the validity of the modeling approach show remarkable agreement with the theoretical model. 相似文献
84.
Process monitoring in additive manufacturing may allow components to be certified cheaply and rapidly and opens the possibility of healing defects, if detected. Here, neural networks (NNs) and convolutional neural networks (CNNs) are trained to detect flaws in layerwise images of a build, using labeled XCT data as a ground truth. Multiple images were recorded after each layer before and after recoating with various lighting conditions. Classifying networks were given a single image or multiple images of various lighting conditions for training and testing. CNNs demonstrated significantly better performance than NNs across all tasks. Furthermore, CNNs demonstrated improved generalizability, i.e., the ability to generalize to more diverse data than either the training or validation data sets. Specifically, CNNs trained on high-resolution layerwise images from one build showed minimal loss in performance when applied to data from an independent build, whereas the performance of the NNs degraded significantly. CNN accuracy was also demonstrated to be a function of flaw size, suggesting that smaller flaws may be produced by mechanisms that do not alter the surface morphology of the build plate. CNNs demonstrated accuracies of 93.5 % on large (>200 μm) flaws when testing and training on components from the same build and accuracies of 87.3 % when testing on a previously unseen build. Finally, evidence linking the formation of large lack-of-fusion defects to the presence of process ejecta is presented. 相似文献
85.
A unique substrate MCPM (Mitsubishi Copper Polyimide Metal-base) technology has been developed by applying our basic copper/polyimide
technology.1 This new substrate technology MCPM is suited for a high-density, multi-layer, multi-chip, high-power module/package, such
as used for a computer. The new MCPM was processed using a copper metal base (110 × 110 mm), full copper system (all layers)
with 50-μm fine lines. As for pad metallizations for the IC assembly, we evaluated both Ni/Au for chip and wire ICs and solder
for TAB ICs. The total number of assembled ICs is 25. To improve the thermal dispersion, copper thermal vias are simultaneously
formed by electro-plating. This thermal via is located between the IC chip and copper metal base, and promotes heat dispersion.
We employed one large thermal via (4.5 mm?) and four small vias (1.0 mm?) for each IC pad. The effect of thermal vias and/or base metal is simulated by a computer analysis and compared with an alumina
base substrate. The results show that the thermal vias are effective at lowering the temperature difference between the IC
and base substrate, and also lowering the temperature rise of the IC chip. We also evaluated the substrate’s reliability by
adhesion test, pressure cooker test, etc. 相似文献
86.
制备了基于一种简单的金属铜配合物2,4-二羟基苯甲酸铜(Ⅱ)(Cu(Ⅱ)DHBA)为载体的PVC膜硫氰酸根离子(SCN-)选择性电极。该电极在1.0×10-1~1.0×10-6mol/LSCN-浓度范围内呈现斜率为-59.5mV/dec的近Nernst电位响应,检测下限为9.1×10-7mol/L。利用紫外可见光谱及交流阻抗技术初步探讨了电极对SCN-呈现的选择性电位响应机理。该电极作为直接电位分析法的指示电极,成功运用于实验室废水中硫氰酸盐含量的测定。 相似文献
87.
利用“球化效应”激光扫描制备球形Ti粉的研究 总被引:1,自引:0,他引:1
利用“球化效应”,在SLS设备上探索将异形Ti粉转化为高性能球形粉末的可行途径。通过系统地改变激光功率、扫描速度,以及选取合适的激光扫描间距,探明了形成“球化效应”的工艺条件,并在激光功率为600W,扫描速度为30mm/s时,获得了较为理想的球形Ti粉。通过对球化过程进行理论分析,得出了选取激光扫描制备球形Ti粉工艺参数的准则。 相似文献
88.
89.
90.
NIU Jitai GUO Wei ZHANG Xinmei and LIU Xingqiu) State Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin China) State Key Laboratory of Metal Matrix Composite Shanghai Jiao Tong University Shanghai China 《稀有金属(英文版)》2003,22(4)
Through the vacuum diffusion welding SiCp/ZL101 aluminum with Cu interlayer,the effect of welding parame-ter and the thickness of Cu on the welded joint property was investigated,and the optimal welding parameters were putforward at the same time.The microstructure of joint was analyzed by means of optical-microscope,scanning electron mi-croscope in order to study the relationship between the macro-properties of joint and the microstructure.The results showthat diffusion welding with Cu interlayer could be used for welding aluminum matrix composites SiCp/ZL101 successfully. 相似文献