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911.
使用不同的立方氮化硼刀具材料(PCBN)和刀具结构,在相同加工参数下,对硼铸铁进行切削加工试验,并对比其加工效果。结果表明:同粗粒度的PCBN刀具相比,细粒度的PCBN刀具加工所得的工件表面粗糙度较低,且刀具本身的耐磨性较高;在切削过程中,随着进给量的增大,工件表面粗糙度也增大;PCBN刀具的负倒棱宽度对加工硼铸铁的切削温度和后刀面磨损有较大影响,负倒棱宽度增加,切削温度和刀具磨损增加,而倒棱角度对刀具和切削过程影响有限。 相似文献
912.
碱金属硫酸盐沉积引起的铁基合金在中温下的热腐蚀 总被引:4,自引:0,他引:4
研究工业纯铁、Fe-Cr和Fe-Al合金有表面Na_2SO_4或Na_2SO_4-K_2SO_4沉积物时在含SO_3的富氧气氛中于中等温度区间的热腐蚀行为。研究结果表明,铁基合金在实验条件下发生的热腐蚀是由液态Na_2SO_4—Fe_2(SO_4)_3或Na_2SO_4-K_2SO_4-Fe_2(SO_4)_3共晶所致,其腐蚀行为与温度、气体组成、合金元素含量、沉积物组成有关。腐蚀形貌的观察表明,铁基合金热腐蚀的发展伴随着疏松的Fe_2O_3层的增厚和紧靠合金表面相对致密的氧化层的快速成长。在合金/氧化物 相似文献
913.
本文是为开发一种磨球成型新工艺——水平连铸白口铸铁棒材料轧成球所做的基础研究。本文研究了锰白口铸铁的塑性变形能力,测定了温度与临界变形率的关系曲线,并对锰白口铸铁成型能力做了试验。结果表明:锰白口铸铁具有较宽的变形温度区间,在850℃时变形量已超过55%,显示出良好的热塑性变形能力,经高温塑性变形后碳化物成孤立块状分布在基体中,从而使得冲击韧性由铸态的3J/cm~2提高到10J/cm~2。 相似文献
914.
915.
An alloy of Fe-10Cr-13P-7C was thermally sprayed by three different processes: (1) 80 kW low-pressure plasma spraying (LPPS),
(2) high-velocity oxyfuel (HVOF) spraying, and (3) 250 kW high-energy plasma spraying (HPS). The as-sprayed coating obtained
by the LPPS process was composed of an amorphous phase. In contrast, the as-sprayed coatings obtained by the HVOF and HPS
processes were a mixture of amorphous and crystalline phases. The as-sprayed coatings showed a high hardness of 700 DPN. A
very fine structure composed of ferrite, carbide, and phosphide was formed, producing a maximum hardness of greater than 1000
DPN in the LPPS coating just after crystallization on tempering. The corrosion re-sistance of the amorphous coating was superior
to a SUS316L stainless steel coating in 1N H2SO4 solution and 1N HC1 solution. Furthermore, the amorphous coating underwent neither general nor pitting corro sion in1NUCI solution and 6% FeCl3 6H2O solution containing 0.05N HCl, whereas the SUS316L stain less steel coating was attacked aggressively. 相似文献
916.
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
917.
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
918.
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
919.
920.