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排序方式: 共有682条查询结果,搜索用时 31 毫秒
41.
Beam-shape correction in deployable phased arrays 总被引:1,自引:0,他引:1
Yonezawa R. Konishi Y. Chiba I. Katagi T. 《Antennas and Propagation, IEEE Transactions on》1999,47(3):482-486
Deployable phased-array antennas-antennas that are receiving great attention-have a major problem in that they possess the possibility of an incomplete deployment and antenna shape distortion. These effects cause a displacement of the element antenna positions that results in deviation of the phase distribution on the antenna aperture, eventually causing antenna beam deflection. We have investigated how to correct this beam deflection by observing the phased-array antenna from certain directions. There are cases when more than one observation point is necessary to carry out the proposed method depending on the extent of the antenna shape distortion and the number of the points is consulted. This correction method makes it possible to correct the deflection of the main beam and also to determine the displacement of relative element positions 相似文献
42.
A rapid liquid flow into a tank may impinge on the free surface, making it swell partially. The returning flow branches off from the free surface and re-submerges at the border of the swollen surface. If the flow velocity along the swollen surface is high enough, gas bubbles are formed at the border and entrained by the liquid flow. The conditions necessary for gas entrainment in a simple system are examined experimentally, using water and air as working fluids. The effect of surface tension is examined by adding a surface active agent to the water. The results show that gas entrainment inception is determined by the flow pattern in the system and the product of the Froude and Weber numbers based on the local velocity at the bubble formation point. 相似文献
43.
44.
This study investigated the role of the basal forebrain cholinergic system (BFCS) in rats' performance of a visuospatial attention task. Muscimol was infused bilaterally and unilaterally into the BFCS to inhibit cholinergic projections to the cortex. Muscimol slowed responding without significantly affecting side-bias. Bilateral infusions increased accuracy for all targets, whereas unilateral infusions reduced accuracy for targets contralateral to the infusion and increased accuracy for targets ipsilateral to the infusion. After a low unilateral dose of muscimol, invalid cues impaired detection of contralateral targets and spared detection of ipsilateral targets. A high unilateral dose of muscimol impaired detection of contralateral targets independently of cueing. These results suggest that interhemispheric imbalance in cortical activity by pharmacological manipulation of the BFCS can impair the detection of lateralized visual stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
45.
A 1.7 GHz-based class-F GaAs FET amplifier is proposed. To achieve high-efficiency performance, a precisely adjustable terminating circuit constructed with lumped elements is introduced. Power-added efficiency of 68% at 1.5 W output is attained with the amplifier. 相似文献
46.
Barium titanium trioxide (BaTiO3) thin films were deposited on fused silica or silicon wafer substrate from barium dipivaloylmethanate (II) (Ba(dpm)2) and titanium tetraisopropoxide (IV) (TTIP) used as precursors in an oxygen microwave plasma. The substrates were dielectrically heated and the substrate temperatures were around 900 K during the film deposition. The deposition was performed for 15 min and the deposits were identified as BaTiO3 by means of X-ray diffraction, X-ray photoelectron spectroscopy, infrared spectroscopy, and ellipsometry. Oxygen and barium atoms and TiO and CO molecules were identified in the plasma. These species would produce higher deposition rates at lower substrate temperatures than those did in the usual thermal metalorganic chemical vapor deposition (MOCVD). The dielectric constant of the BaTiO3 thin film that was directly deposited on the silicon wafer substrate was as low as 101 order of magnitude. Because the deposit reacted with the substrate and an interdiffusional layer was formed, the platinum layer was coated on the silicon wafer substrate in order to prevent the formation of an interdiffusional layer. The dielectric constant then increased to 103 order of magnitude. 相似文献
47.
In this paper, we present new strategies of vibration suppression in flexible shaft of a motor with active and passive magnetic forces. Shaft magnetic damping originates from the principle of a bearingless motor having a radial magnetic force generation. Radial force is used for shaft vibration suppression to go through the first critical speed. Simplifications are described in a suppression force system. We propose the elimination of a power source with self-excitation, as well as the elimination of sensors, controllers, and inverters, although the effectiveness is limited. 相似文献
48.
Human calicivirus Sapporo (SV) has typical calicivirus morphology and causes acute gastroenteritis in children. The nucleotide sequence of 3.2 kb of the 3' end of SV was determined from a cloned cDNA. The 3' end of the SV genome is predicted to encode the RNA-dependent RNA polymerase region, the capsid protein and two small open reading frames. The nonstructural and capsid protein coding sequences in the SV genome are fused in a single open reading frame. The organization of these proteins in the SV sequence is similar to that of rabbit hemorrhagic disease virus and the recently described Manchester virus, and distinct from the genome organization of the prototype human calicivirus, Norwalk virus, that lacks typical calicivirus morphology and has been described as a small round structured virus (SRSV). Sequence analysis of the predicted capsid region showed that the SV capsid is longer by approximately 30 amino acids than the capsid of any of the SRSVs, and multiple sequence alignments showed that these additional amino acids are located in the variable region of the capsid protein. Expression of the capsid protein of SV in insect cells resulted in the self-assembly of virus-like particles that have a morphology similar to that of the native virus. This result shows that calicivirus morphology is determined by the primary sequence of the capsid protein. 相似文献
49.
Quartz glass rods, 5.5 mm in diameter, were immersed in ternary Fe-S-O melts and quaternary Cu-Fe-S-O melts at 1493 K, and
the decrease in rod diameter was measured. The rate of slag formation increased with the rotating speed of the rod and the
FeO activity of the molten matte. A thin film of slag was formed on the rod surface when the FeO activity of the molten matte
was higher than that of silica-saturated slag. The mass transfer coefficient of the FeO component in the boundary layer of
the molten matte on the slag film was calculated on the assumption that the rate of slag formation was controlled by the mass
transfer, and the results showed a dependency on the rotating speed of the rod close to the reported value. The rate of slag
formation also increased with the Cu content of the molten matte, probably due to an accelerated upward movement of slag along
the rod surface. At the time of lower FeO activity of the matte, the SiO2 rod was thought to dissolve in the matte, and the rate of dissolution increased with the FeO activity and Cu content of the
matte.
Y. CHIBA, formerly Graduate Student. 相似文献
50.
The inhibitory effects of cultured milk using 76 strains of lactic acid bacteria isolated from milk products were investigated on the mutagenicity of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P2), a tryptophan pyrolysate for Salmonella typhimurium TA98. Each cultured milk sample displayed its characteristic antimutagenic effect against the mutagenicity of Trp-P2. The milk cultured with Lactobacillus acidophilus LA106 (LA2) showed the highest inhibition of 82.1% among the strains used. Milk samples cultured with Lactococcus lactis subsp. lactis, Lll103 (10-3) and Lll102 (KM) also exhibited higher inhibition percentages. 相似文献