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71.
Earlier studies have shown that sulfur dioxide and metal-support interaction can strongly influence propane oxidation over platinum. In particular, oxidation activity is enhanced when platinum is supported on sulfated -alumina or zirconia compared to -alumina. Therefore, it is of interest to compare the performance of palladium under the same experimental conditions. Four model catalysts were examined: Pt/-alumina, Pt/zirconia, Pd/-alumina and Pd/zirconia. The metal loading was kept at or below 0.05 wt% to emphasize changes in activity attributable to metal-support interaction. Reaction rates were measured with and without sulfur dioxide. Surface sulfation was analyzed by measuring acid strength and evaluating spectra obtained by Fourier-transform infrared spectroscopy. In contrast to platinum, sulfation does not promote propane oxidation on Pd/-alumina, and Pd/zirconia is less active than Pd/-alumina. 相似文献
72.
The insecticidal nonprotein amino acid S-(-carboxyethyl)-cysteine (S-CEC) is the major free amino acid in the seeds of severalCalliandra spp. where it accounts for up to 2.9 % of dry weight. Lesser amounts of other related S-containing amino acids and an array of nonprotein imino acids derived from pipecolic acid are other constituents. High concentrations of imino acids, which also show insecticidal activity, are maintained in the mature leaves, but sulfur compounds are lacking. In this study the disappearance of S-CEC from the germinating seeds and young seedlings ofC. rubescens was monitored over time. After 10 weeks, S-CEC continues to be found in high concentrations in the stems and new leaves. As young leaves mature, sulfur compounds quickly decrease in concentration. Traces of S-CEC are found in new leaves of plants up to nine months after germination. Whether high concentration of S-CEC in young leaves is due to transportation from the seed or de novo synthesis is unclear. The ecological implications are discussed. 相似文献
73.
李正西 《硫磷设计与粉体工程》2003,(2):8-12
硫磺是生产硫酸的主要原料,我国从石油和天然气中回收硫及硫的成形技术正在日益发展。介绍了融熔硫磺的各种成形方法,建议国内今后应朝着水小粒法、空气小料法的成形技术发展。 相似文献
74.
The behavior of sulfur transformation during rapid hydropyrolysis of coal was investigated using a pressurized, continuous free fall pyrolyzer under the conditions of temperature ranging from 923 to 1123 K and hydrogen pressure up to 5 MPa. The yields of sulfur converted to gas, tar and char were determined, together with the analyses of sulfur form distributions in coals and chars. The results showed that the decomposition of inorganic sulfur species was affected only by the temperature, while the increases in temperature and hydrogen pressure obviously enhanced the removal of organic sulfur from coal. The extent of organic sulfur removal was proportional to the coal conversion, depending on coal type. A significant retention of gaseous sulfur products by the organic matrix of the char was observed during hydropyrolysis of a Chinese coal above 1023 K, even under the pressurized hydrogen atmosphere. The kinetic analysis indicates that the rate of organic sulfur removal from coal was 0.2th-order with respect to the hydrogen pressure, and the activation energy for total sulfur removal and organic sulfur removal is 17-26 and 13-55 kJ/mol, respectively. The low activation energies suggest that the transformation and removal of sulfur from coal might be controlled by the diffusion and/or thermodynamic equilibrium during hydropyrolysis under the pressurized conditions. 相似文献
75.
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78.
根据国家标准GB/T1792-88《馏分燃料中硫醇硫含量测定法(电位滴定法)》的试验方法.考察评估了该项分析的测量不确定度。 相似文献
79.
Due to their superior thermal and chemical stability, polyimides are often used as adhesives in harsh environments. This study examines the effect on bond strength of thioether sulfur in the polyimide backbone. Bonds were made using steel that was believed to catalyze the oxidation of sulfur. In addition, non-sulfur containing polyimides with similar Tg were also studied for comparison. The polymer/metal interface was studied using both the T-peel and wedge tests. No apparent effect was observed in the T-peel test with steel where the T-peel strengths of non-sulfur and sulfur containing polyimides were similar. In the wedge test, however, the sulfur-containing BDSDA/ODA bonded to steel had the smallest initial crack length of 34 mm. However, the BTDA/APB bonds tested in a dry environment had the smallest crack growth. The sulfur-containing BTDA/ASD performed best of the bonds tested in a wet environment. Metal-catalyzed oxidation of sulfur was observed to take place in the steel case, but not to an extent to have a noticeable effect on peel strength. 相似文献
80.
J. A. Rodriguez X. Wang P. Liu W. Wen J. C. Hanson J. Hrbek M. Pérez J. Evans 《Topics in Catalysis》2007,44(1-2):73-81
Synchrotron-based techniques (high-resolution photoemission, in-situ X-ray absorption spectroscopy, and time-resolved X-ray diffraction) have been used to study the destruction of SO2 and the water-gas shift (WGS, CO + H2O → H2 + CO2) reaction on a series of gold/ceria systems. The adsorption and chemistry of SO2 was investigated on Au/CeO2(111) and AuO
x
/CeO2 surfaces. The heat of adsorption of the molecule on Au nanoparticles supported on stoichiometric CeO2(111) was 4–7 kcal/mol larger than on Au(111). However, there was negligible dissociation of SO2 on the Au/CeO2(111) surfaces. The full decomposition of SO2 was observed only after introducing O vacancies in the ceria support. AuO
x
/CeO2 surfaces were found to be much less chemically active than Au/CeO2(111) or Au/CeO2−x
(111) surfaces. In a separate set of experiments, in-situ time-resolved X-ray diffraction and X-ray absorption spectroscopy were used to monitor the behavior of nanostructured {Au + AuO
x
}–CeO2 catalysts under the WGS reaction. At temperatures above 250 °C, a complete AuO
x
→ Au transformation was observed with high catalytic activity. Photoemission results for the oxidation and reduction of Au
nanoparticles supported on rough ceria films or a CeO2(111) single crystal corroborate that cationic Auδ+ species cannot be the key sites responsible for the WGS activity at high temperatures. The active sites in {Au + AuO
x
}/ceria catalysts should involve pure gold nanoparticles in contact with O vacancies of the oxide. 相似文献