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Prevention of steel corrosion in concrete exposed to seawater with submerged sacrificial anodes 总被引:2,自引:0,他引:2
Luca Bertolini Matteo GastaldiMariaPia Pedeferri Elena Redaelli 《Corrosion Science》2002,44(7):1497-1513
This paper presents the results of a study of the effectiveness of submerged sacrificial anodes in preventing the onset of pitting corrosion in the emerged part of marine piles. Experimental tests were carried out on reinforced concrete columns with steel embedded both in chloride free concrete and chloride contaminated concrete in order to compare the effects of sacrificial anodes on passive steel and on corroding steel. Results have shown, at least under the present testing conditions, that sacrificial anodes may be more effective in preventing corrosion initiation (i.e. in providing cathodic prevention) than in controlling ongoing pitting corrosion (i.e. in guaranteeing cathodic protection). Monitoring criteria for this type of prevention are also discussed. 相似文献
74.
鄱阳湖湿地重金属污染地质累积指数与潜在生态危害指数评价 总被引:2,自引:0,他引:2
本文用地质累积指数和潜在生态危害指数对鄱阳湖重金属污染进行评价,结果表明:(1)评价结果表明鄱阳湖区重金属污染主要为Cu污染。鄱阳湖重金属污染的主要来源是德兴铜矿,其中Cu当然是主要污染物,因此,评价结果与实际情况是吻合的。(2)Cu、Zn、Cd污染源相同且来源于德兴铜矿,Pb表现为面源污染。湖区Cu、Zn、Cd分布均表现出从饶河段至湖口逐步降低的趋势,且Cu、Zn、Cd在土壤中的含量呈现显著的相关性和偏相关性,可以推论Cu、Zn、Cd污染源相同且来源于德兴铜矿。Pb在湖区均匀分布表现为面源污染,这可能与湖区Pb污染来源于船舶燃油有关。 相似文献
75.
Yujin Hwang Jae-Keun Lee Jong-Ku Lee Young-Man Jeong Seong-ir Cheong Young-Chull Ahn Soo H. Kim 《Powder Technology》2008,186(2):145-153
This paper presents an experimental study on the homogeneous dispersion of nanoparticles in nanofluids. In this study, various physical treatment techniques based on two-step method, including stirrer, ultrasonic bath, ultrasonic disruptor, and high-pressure homogenizer were systematically tested to verify their versatility for preparing stable nanofluids. Initially carbon black and silver nanoparticles dispersed in base fluids with the presence of surfactant were found to be highly agglomerated with the hydrodynamic diameter of 330 nm to 585 nm, respectively. After both CB and Ag nanofluids were treated by various two-step methods, stirrer, ultrasonic bath, and ultrasonic disrupter was found to do a poor performance in deagglomeration process for the initial particle clusters. However, the high-pressure homogenizer produced the average diameter of the CB and Ag particles of 45 nm and 35 nm, respectively, indicating that among various physical treatment techniques employed in this study, the high-pressure homogenizer was the most effective method to break down the agglomerated nanoparticles suspended in base fluids. In order to prepare another nanofluid with much smaller primary nanoparticles, we also employed a modified magnetron sputtering system, in which the sputtered nanoparticles were designed to directly mix with the running surfactant-added silicon oil thin film formed on a rolling drum (i.e. one-step method). We observed that Ag nanoparticles produced by the modified magnetron sputtering system were homogeneously dispersed and long-term stable in the silicon oil-based fluid, and the average diameter of Ag nanoparticles was found to be ~ 3 nm, indicating that the modified magnetron sputtering system is also an effective one-step method to prepare stable nanofluids. 相似文献
76.
The inhibition effect of 2-mercaptothiazoline (2MT) on the corrosion behavior of mild steel (MS) in 0.5 M HCl solution was studied in both short and long immersion times (120 h) using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. For long-term tests, hydrogen gas evolution (VH2−t) and the change of the open circuit potential with immersion time (Eocp − t) were also measured in addition to the former three techniques. The surface morphology of the MS after its exposure to 0.5 M HCl solution with and without 1.0 × 10−2 M 2MT with the different immersion times was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal stability of the inhibitor film was investigated by thermogravimetric analysis (TGA). The value of activation energy (Ea) for the MS corrosion and the thermodynamic parameters such as adsorption equilibrium constant (Kads), free energy of adsorption (ΔGads), adsorption heat (ΔHads) and adsorption entropy (ΔSads) values were calculated and discussed. The potential of zero charge (PZC) of the MS in inhibited solution was studied by the EIS method, and a mechanism for the adsorption process was proposed. The results showed that 2MT performed excellent inhibiting effect for the corrosion of the MS. Finally, the high inhibition efficiency was discussed in terms of adsorption of inhibitor molecules and protective film formation on the metal surface. TGA results also indicated that the inhibitor film on the surface had a relatively good thermal stability. 相似文献
77.
Stable YAG (Y3Al5O12) aqueous slurry with ammonium polyacrylate (NH4PAA) polyelectrolytes as dispersant was prepared by ball mill method. The effects of polyelectrolyte concentration and pH value on the stability of the suspension is described here, and the stability maps are constructed at different pH value and polymer concentration. The rheological behavior of YAG slips of different solid loading (60–70%) has been studied by measuring their viscosity and shear stress as a function of shear rate and pH of the slurry. An optimal amount of dispersant and pH value for the suspension was found. YAG suspension displays a maximum in zeta potential values and a minimum viscosity in pH range of 9–11. Slips behaved as near Newtonian at the pH value up to a solid loading of 60 wt% and as non-Newtonian with thixotropic behaviors above this solid loading value. The density and the green as well as sintered microstructure of the cast products bear a direct relationship to the state of this slips induced by the alternation in the pH and the concentration of the dispersant as well as solid loading. 相似文献
78.
在分析了液压系统常见的能耗问题的基础上,以现有的某型号液压挖掘机动臂液压系统为研究对象,设计了新型动臂势能回收系统,并建立该系统的AMESim模型。通过仿真分析得出新液压系统的能源利用率比不采用任节能措施的液压系统提高了34.8%,有良好的节能效果。 相似文献
79.
《Measurement》2016
The field signature method (FSM) is a nondestructive testing (NDT) method based on the potential drop (PD) technique and has been applied to online metal pipe corrosion monitoring for nearly three decades. The many advantages and benefits of the method have been reported in a number of studies, but few have reported on its limitations or shortcomings. However, the detection accuracy for pitting corrosion in FSM is very low. In this paper, the reasons for the low pitting corrosion detection accuracy of FSM were analyzed and it was found that different corrosion pits, which have different sizes, depths or positions, generally have differing influences on the potentials of nearby electrode pairs. Therefore, a new method using a subdivided resistor network to assess pitting corrosion is proposed and verified. When compared with the traditional method, the most important parameter, namely the pitting corrosion depth detection accuracy, can be significantly improved. 相似文献
80.