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排序方式: 共有1282条查询结果,搜索用时 31 毫秒
21.
Kimiyasu Sato Miyuki Kawai Yuji Hotta Takaaki Nagaoka Koji Watari 《Journal of the American Ceramic Society》2007,90(4):1319-1322
Because the pyrolysis of organic substances can result in the emission of harmful pollutant gases, a reduction in the use of organic binders is one aim of today's ceramics industry. A novel ceramic-forming process was developed that requires considerably less organic binder than conventional techniques. The process involves immobilizing reactive molecules on the surfaces of the particles, which on subsequent irradiation with microwaves, form bridges that bind the entire particle assembly together. The chemical forces involved produce strong bonds, resulting in a significant reduction in the amount of organic binder that is required to maintain the shape of the ceramic green body. This method will help to decrease emissions of harmful gases produced from pyrolysis of the binder. 相似文献
22.
Summary A study was made of the degree of splitting of coconut and soybean oils by the Twitchell process at 35±0.1°C. with no shaking
or stirring, using an agent consisting mainly of tetrabutyl naphthalene sulfonic acid with water or dilute sulfuric acid.
The degree of splitting was greater with sulfuric acid than with water. In general, the degree of splitting of soybean oil
was greater when the sulfonic acid was dissolved in the oil layer than when it was in water. The reverse was true with coconut
oil. Although addition of glycerol had no effect on the degree of splitting, addition of glacial acetic acid to the coconut
oil system decreased fat splitting to a considerable extent. Addition of coconut fatty acids to the coconut oil system had
little effect, but soybean fatty acids added to the soybean oil system markedly increased the degree of splitting.
For the first time it has been demonstrated that, at 35±0.1°C., splitting of a fat by the Twitchell process occurs in a stepwise
way. Coconut oil in contact with 1N sulfuric acid containing the sulfonic acid, corresponding to 1% by the weight of the oil, was about 90% split in 15 to 30
days, depending on the area of contact of the two layers. The diglyceride concentration reached a maximum during the early
days of the reaction and then decreased somewhat. Monoglyceride concentration appeared to reach a maximum more slowly and
then continued at that level as the concentrations of free fatty acids and glycerol steadily increased.
Presented at the symposia on fat of the Chemical Society of Japan, Nov. 10, 1954, and Nov. 8, 1955, Nagoya, Japan; and the
8th annual meeting of the Chemical Society of Japan, Apr. 2, 1955, Tokyo, Japan. 相似文献
23.
The crystallization kinetics of the running filament in melt spinning have been studied for three cases: isothermal crystallization of an isotropic melt, non-isothermal crystallization of an isotropic melt, and non-isothermal crystallization of a non-isotropic melt. Both the temperature and the orientation dependences of nucleation rate and growth rate are estimated for polypropylene. Calculated curves for non-isothermal crystallization of a non-isotropic melt with partial high orientation closely approximate the experimental data. In particular, the experimental data are best explained by crystallization with two-dimensional growth. The crystallization processes in melt spinning may be governed by localized molecular orientation of the supercooled melt in the initial stage. 相似文献
24.
A unique class of conjugated compounds composed of the derivative of condensed polycyclic aromatic compound with the phenyl group and diphenyldiacetylene oligomer was synthesized by annealing of diphenyldiacetylene under elevated pressure. The effect of annealing pressure on the conductivity of the compounds was studied. The total conductivity of the compound decreased with a decrease of frequency, approaching a constant value (dc conductivity: Cdc). The dc conductivity of the compound increased from below 10?15 to 10 S cm?1 with increasing annealing pressure. The dc conductivity of the oligomer was below 10?15 S cm?1 and that of the derivative increased from 10?8 to 10 S cm?1 with decreasing H/C (H/C:0.45–0.04). The conduction of the conjugated compound was electronic. The temperature coefficient of those dc conductivities was positive, with an approximately linear relation between In (CdcT0.5) and (1/T)0.25, where T is the temperature. The ac conductivities Cac were proportional to temperature and frequency f and had the following equation Cac = TfS, S = 0.67–0.75. These results showed that the conduction mechanism can be explained by the hopping in a manifold of states at the Fermi level. © 1994 John Wiley & Sons, Inc. 相似文献
25.
Annadanam V. Sesha Sainath Takashi Inoue Yoshiharu Hatakeyama Masahiro Shishido Kenzo Okamoto Seigou Kawaguchi Takashi Kuriyama Kiyohito Koyama 《大分子材料与工程》2004,289(3):264-268
Summary: Polyacrylonitrile (PAN) particles with micro‐size ranges (0.15–2 μm) were prepared by emulsion and dispersion polymerizationa and in supercritical carbon dioxide media. The PAN particles were blended with Nylon 6 (PA6) at 220 °C by using a miniature mixer; it was found that melt‐mixing was possible for PAN‐rich compositions as high as 70 wt.‐%. Blends were characterized by scanning electron microscopy, IR, viscosity measurements, differential scanning calorimetry, and dynamic mechanical thermal analysis (DMTA). The size and shape of original PAN particles were retained in PAN/PA6 blends. The useful range to blend PAN particles size was less than 1 μm in terms of shape retention of the PAN particles in blends. Blends with 40 wt.‐% PAN content were found to be melt‐processable. The elastic modulus was higher for PAN/PA6 blends than pure PA6.
26.
Takaaki Tsurumi Young-Bae Kil Kouhei Nagatoh Hirofumi Kakemoto Satoshi Wada Sadayuki Takahashi 《Journal of the American Ceramic Society》2002,85(8):1993-1996
The material coefficients of "soft" and "hard" lead zirconate titanate (PZT) ceramics were determined as complex values by the nonlinear least-squares-fitting of immittance data measured for length-extensional bar resonators. The piezoelectric d -constant should be a complex value to obtain a best fitting between observed and calculated results. Because the elastic, dielectric, and piezoelectric losses determined in this process were not "intrinsic" losses, a calculation process to evaluate the "intrinsic" losses was proposed. It was confirmed that the intrinsic losses were smaller than the corresponding extrinsic losses. The intrinsic piezoelectric loss existed in both soft and hard PZTs; ∼50% of the loss of piezoelectric d -constant was derived from the elastic and dielectric losses. The most notable difference between the soft and hard PZTs was observed in their elastic losses. 相似文献
27.
Changho Jung Hideyuki Tsuboi Michihisa Koyama Momoji Kubo Ewa Broclawik Akira Miyamoto 《Catalysis Today》2006,111(3-4):322-327
CO adsorption over Pd4 and Pt4 cluster supported by c-ZrO2(1 1 1) and CeO2(1 1 1) catalyst systems was investigated using periodic density functional method in order to clarify the support effect on CO activation. We found that the support increases the CO activation for bridge and three-fold sites but decreases for the atop site. Moreover, it was found that the support changes the site preference for the CO adsorption. Bridge site on both the Pt4/c-ZrO2 and Pt4/CeO2 show larger CO adsorption energies than those on the other sites while the atop site is energetically preferable on isolated Pt4 cluster. c-ZrO2 supported Pd shows the largest CO activation with large charge transfer from the catalyst to the CO molecule. This reveals that ZrO2 supported Pd can be a good catalyst for CO activation because of its higher probability to the three-fold site CO adsorption. We also found that positively charged M4 clusters on the support keep their strong electron-donating properties and have enough charge density to contribute to the activation of an adsorbed CO molecule by a charge transfer. 相似文献
28.
The diffusion and adsorption of C.I. Direct Yellow 12 and Blue 15 in water-swollen ordinary cellophane sheets were examined at various ionic strengths. The concentration dependence of apparent diffusion coefficients, Dc, for these dyes was obtained from the diffusion profiles in the substrate, which were measured by the use of the cylindrical film roll method. The decrease of apparent porosity with an increase in the amounts of adsorption was observed. To explain the diffusion/adsorption behaviors of these systems, a variable porosity model was proposed and was applied to analyze the concentration dependence of Dc's. The diffusion/adsorption behaviors of these dyes could be quantitatively described by this model at relatively low ionic strengths. At higher ionic strengths and/or lower values of C, i.e., at the large values of Cim/Cm, where the C's are the concentrations of immobilized (suffix im) and mobile (suffix m) species, it needed to introduce the concept of dynamic equilibria which occurred simultaneously with diffusion but deviated from the true equiliblia measured by the adsorption experiments. 相似文献
29.
Masahiko Shimada Ken'ichi Matsushita Shusei Kuratani Taira Okamoto Mjtsue Koizumi Koji Tsukuma Takaaki Tsukidate 《Journal of the American Ceramic Society》1984,67(2):23-C-
The temperature dependence of Young's modulus and internal friction (Q−1 )in alumina, silicon nitride, and partially stabilized zirconia (Y-PSZ) ceramics was studied. Little change in Q−1 was found for alumina, whereas Q−1 for silicon nitride ceramics increased above 700°C. The Q−1 of Y-PSZ increased markedly with increasing temperature up to a peak at ∼200°C. 相似文献
30.
In order to develop an energy-saving copper recycling process from wastes, electrochemical measurements were conducted in ammoniacal alkaline solutions containing Cu(I) ions and an ammonium salt of sulfate, chloride or nitrate. The results of each system were then compared. The polarization measurements suggested that the voltage required for the electrode process is lower in the chloride and nitrate systems than that in the sulfate system. The cathode current efficiency during the copper electrodeposition varied from 39 to 97% and increased with current density in the chloride and sulfate systems. In the nitrate system, the lowest cathode current efficiency of 30% was observed because of nitrate ion reduction. Based on these results, the power consumption required for the electrowinning stage of the copper recycling process was calculated. Among these three systems, the chloride system showed the lowest power consumption of 500 kWh t−1 at the current density of 200 A m−2, which is about 25% of the conventional copper electrowinning process from a copper sulfate-sulfuric acid solution. 相似文献