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排序方式: 共有419条查询结果,搜索用时 46 毫秒
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Dialkyl dithiophosphate ester (DDPE) used as an extreme pressure/antiwear (EP/AW) additive in mineral base oil (BO) was introduced to a steel–aluminum contact in this study. The tribological performance of DDPE was explored by means of a universal tribotester under different loads and durations. The worn aluminum surface topographies were observed and photographed via laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM). Tribochemical interactions between the additive and aluminum surface were investigated using energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The distinction of chemical structure between lubricant untapped and the counterpart retrieved after a 3-h sliding process was detected by Fourier transform infrared spectroscopy (FTIR). The friction coefficient of a BO + DDPE-lubricated friction pair under 300 N shows the lowest value. LSCM and SEM images show that the aluminum surface lubricated with BO + DDPE was well protected under a high loading condition of 300 N, and the 3-h sliding process deteriorated the surface topography. However, DDPE was not able to offer an effective lubricating film under a mild condition of 50 N. EDS results of S and P elements on the worn surface indicate that a tribochemical film was generated under 300 N in the sliding process. XPS results further show that the chemical compounds in the tribochemical film included Al2S3, Al2(SO4)3, AlPO4, and Al2O3. The P-containing compound in the tribofilm acted as a sacrificial layer, whereas the S-containing compounds were more durable. FTIR analyses demonstrate that the phosphorus–sulfur double bond was broken up due to the tribochemical interactions. 相似文献
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The last decade has seen a growing interest in hybrid electrically conducting nanocomposites. This article aims to provide a detailed overview of the present status of research in carbon nanotube–polyaniline (CNT/PANI) composites, from processing to structural and property evaluations. CNT/PANI are synthesized by electrochemical and chemical processing. When chemical methods are used, the main challenge is to obtain processable CNT/PANI in the emeraldine salt (ES) form composites. Stable dispersions of ES–CNT in organic media are prepared using the post doping method, inverse emulsion polymerization, or ex situ polymerizations. On the contrary, stable water dispersions of CNT/ES are prepared using hydrophilization of a preformed CNT/ES composite, direct synthesis of micelle–CNT hybrid templates, interfacial polymerization, covalent functionalization of CNT with a water soluble polymer, or using electrostatic interactions between two oppositely charged ES and CNT aqueous colloids. Moreover, the strategies for the synthesis of ternary CNT/PANI composites incorporating noble metal nanoparticles, metal oxide, or graphene sheets are also presented and analyzed in depth. Finally, we give a review of potential applications, including chemical sensors, capacitors, fuel cells and electronic devices. 相似文献
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介绍了一种应用FPGA(EP2C70)和AT89C51设计的高精度温度采集系统。该系统能够实现PN结、热电阻、热电偶3种方式的温度采集,能测量不同的范围、不同的测量精度及不同场合的温度。数据处理采用FPGA(EP2C70),它极高的程序运算速度使得系统响应更快更精确。 相似文献
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以苯并噁嗪(BZ)作为氰酸酯(CE)-环氧树脂(EP)-双马来酰亚胺(BMI)基胶粘剂的改性剂,探讨了BZ含量对改性胶粘剂的力学性能、介电性能、耐热性、耐水性和可操作性等影响。结果表明:当w(BZ)=2%时,改性胶粘剂的综合性能较好,其常温剪切强度(24.98 MPa)和高温(200℃)剪切强度(21.24 MPa)分别比未改性胶粘剂提高了16.9%和32.7%、介电系数低于3.0、吸水25 h后的吸水率仍低于1.2%且耐热性能未受到影响;170℃时凝胶时间为71 min,说明改性胶粘剂的可操作性较强,并且满足使用期的要求;改性胶粘剂在电子电器行业中具有良好的应用前景。 相似文献
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防锈油中酸性物质含量的控制有着重要的意义。通过研究电位滴定法测定酸值的原理和滴定过程中各项参数对测试结果的影响,最终确定并建立一组适用于防锈油品的酸值的测试方法。满足了材料性能的检测和质量监控的需要。 相似文献
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Six alternatives for the conversion of an average Colombian palm oil mill (30 t h−1 of fresh fruit bunches (FFB) into biorefineries were evaluated. The alternatives studied were: (C1) Production of biogas from the Palm Oil Mill Effluents (POME), (C2) Composting of empty fruit bunches (EFB) and fiber, (C3) Biomass combustion for high pressure steam combined heat and power, (C4) Pellets production, (C5) Biochar production and, (C6) Biochar and bio-oil production. The available biomass could result in up to 125 kWh of electricity, 207 kg of compost, 125 kg of pellet, 44 kg of biochar and 63 kg of bio-oil per metric ton of FFB. The global warming potential (GWP), eutrophication potential (EP), net energy ratio (NER), capital expenditures (CAPEX), operational costs (OPEX), net present value (NPV) and internal rate of return (IRR) were calculated for all the alternatives. GHG reductions of more than 33% could be achieved. Anaerobic digestion and composting contributed to 30% reduction of the EP. The CAPEX for all of the biorefinery alternatives studied varies between 0.7 $ t−1 and 2.8 $ t−1 of FFB. The OPEX varies between 1.6 $ t−1 and 7.3 $ t−1 of FFB. The NPV for viable scenarios ranged between 2.5 million and 13.9 million US dollars. The IRR calculated varied between 3% and 56% and the payback periods were between 3 and 8 years. The total extra incomes reached values up to 15.2 $ t−1 of FFB. Overall the pellets production biorefinery was the preferred alternative. 相似文献
10.
In this work, the influence of pulse current parameters on springback and bending force of magnesium alloy during electropulse-assisted(EPA) V-bending was investigated. The experimental results showed that pulse current can effectively reduce the springback and the bending force compared to the experiments without current. The frequency has a more significant influence on bending force and springback than electric current density. Electroplastic(EP) effect begins to work when pulse current parameters reach a threshold value. To explore the mechanism of EPA V-bending, the microstructure evolution and fracture surface of the bending specimen were studied. It was found that pulse current can promote the occurrence of dynamic recrystallization(DRX) of magnesium alloy compared to traditional hot forming process. The fracture mode of AZ31B under EPA V-bending evolves from brittle fracture to ductile fracture with increasing pulse current parameters. Based on the discussion of athermal and thermal effects of EP effect, the mechanism of pulse current to promote DRX is studied and athermal effect is proved to exist. 相似文献