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851.
Characterization of plasma sprayed Fe-17Cr-38Mo-4C amorphous coatings crystallizing at extremely high temperature 总被引:5,自引:0,他引:5
A Fe-17Cr-38Mo-4C alloy powder was plasma sprayed by three processes: an 80 kW low-pressure plasma spray (LPPS), a 250 kW
high-energy plasma spray (HPS), and a 40 kW conventional plasma spray (APS). The as-sprayed coating obtained by the LPPS process
is composed of only amorphous phase. As-sprayed coatings obtained by the HPS and APS processes are a mixture of amorphous
and crystalline phases. The three as-sprayed coatings exhibit a high hardness of 1000 to 1100 DPN. The amorphous phase in
these coatings crystallizes at a high temperature of about 920 K. A very fine structure composed of hard ϰ-phase and carbides
is formed after crystallization. The hardness of the coating obtained by LPPS reaches a maximum of 1450 DPN just after crystallization
on tempering and retains a high hardness more than 1300 DPN after tempering at high temperatures of 1173 or 1273 K. The corrosion
potential of the amorphous coating is the highest among the three coatings and higher than that of a SUS316L stainless steel
coating. The anodic polarization measurements infer that the corrosion resistance of the amorphous coating is superior or
comparable to SUS316L stainless steel coating in H2SO4 solution. 相似文献
852.
金属磁性液体的制取方法研究 总被引:2,自引:2,他引:2
研究了采用在油介质中连续分解五羰基铁蒸气的方法一步制得饱和磁化强度达到767×10^-4T的金属铁磁性液体。该方法也可应用于金属镍、钴等磁性液体的制取。 相似文献
853.
The effect of segregation of alloying elements on the phase transformation of ductile iron during austempering was investigated.
Four heats, each containing 0.4%Mn, 1% Cu, 1.5% Ni, or 0.4% Mo (wt%) separately, were melted; then three different sizes of
casting bars (3,15, and 75 mm diameter) were poured from each heat. The distribution and the degree of segregation of certain
elements were quantitatively analyzed using an electron microprobe. A personal computer (PC)-controlled heat treating system
was used to measure electrical resistivity, and the information on resistivity variations was used to analyze the effect of
segregation on phase transformations during austempering. Also, Charpy impact and Rockwell hardness tests were performed to
determine the effect of segregation on properties.
Results of the electron microprobe analysis showed that the degree of segregation of alloy elements increases with an increase
in diameter of the casting bars (i.e., an increase of solidification time of castings). The degree of segregation of alloy
elements, represented by segregation ratio (SR) (the maximum concentration of element in cell divided by the minimum concentration
of element in cell), varied linearly with the casting modulus (M) (volume of casting divided by surface area of casting).
Regarding the segregating tendency among alloy elements, positive segregating elements Mn and Mo showed more segregation than
the negative segregating elements Si, Cu, and Ni. In addition, segregation of Mo was more significant than Mn, and that for
Cu was greater than Ni and Si.
Between the time of finishing the first stage and beginning the second stage of bainite reaction in ductile irons, there is
a significant “processing window,” At;, for austempering to obtain optimum mechanical properties. From the electrical resistivity
data, it was observed that the austempering temperature plays a major role in the processing window. There was a narrow window
at 400 ‡C but a larger one at 350 ‡C. Additionally, the microsegregation of alloying elements led to variation of the time
of phase transformation for various regions in the grain cells of ductile iron which caused the processing window to decrease.
The span of the processing window decreased with an increase in degree of segregation.
There was no significant difference in the hardness of the alloys in various diameter specimens. However, the impact toughness
was significantly affected by the segregation. The impact values in 15 mm specimens with less degree of segregation were greater
than those in 75 mm specimens with significant segregation.
The Ni, Cu, and Mn alloys that were austempered to complete the first stage of bainite formation had approximately the same
impact values for all diameter samples. The Mo alloy upon austempering produced no bainite, but it had much untransformed
retained austenite in the intercellular regions and, therefore, had lower impact values. 相似文献
854.
855.
856.
857.
选用CCY-84型磁测应力仪来测定铸铁轧辊工作层残余应力,轻便价廉,但须先获得磁测应为灵敏系数。笔者对铬相冷硬球墨复合铸铁轧辊白口层材料的灵敏系数进行了标定,结果表明这种材料的灵敏系数α为11电流字,/MPa。 相似文献
858.
859.
Fe/HCl体系中缓蚀剂吸脱附诱导的电流/电位振荡 总被引:2,自引:0,他引:2
研究了HCl介质中活性电位区有机缓蚀剂在Fe电极表面吸脱附诱导产生的电化学振荡现象,及缓蚀剂浓度、电极电位和溶液搅拌等因素对振荡行为的影响。结果表明,在HCl介质中Fe电极的活性电位区同样得到了规整的电流振荡波,但相同条件下的振荡行为要弱于H2SO4介质中,随缓蚀剂浓度升高,振荡波的周期变长,振荡 减弱;由阴极到阳极,电流振荡波形不同,周期也有所增长,搅拌对电流振荡无明显影响,同时报道了该缓蚀体系中恒电流电位振荡的新现象。 相似文献
860.
用负压铸渗工艺制备了WC/HT300基表面复合材料,研究了WC体积分数和冲蚀磨损浆料中的颗粒粒度对复合材料的抗冲蚀磨损性能的影响。对于同一种WC颗粒体积分数的复合材料,当浆料中的石英砂粒度大时,复合材料的体积磨损率较大,抗冲蚀磨损性能降低。WC体积分数为27%和36%的表面复合材料具有比其他WC体积分数复合材料优越的耐磨损性能;在磨料粒度为40~70目的工况下,WC体积分数为36%的复合材料,具有比体积分数为27%的复合材料优越的耐磨性能;但在磨料粒度增大到20~40目时,WC体积分数为27%的复合材料,具有比WC体积分数为36%的复合材料优越的耐磨损性能。 相似文献