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791.
Li-Piin Sung Joan Jasmin Xiaohong Gu Tinh Nguyen Jonathan W. Martin 《Journal of Coatings Technology and Research》2004,1(4):267-276
Laser scanning confocal microscopy (LSCM) has been used to characterize the changes in film thickness and local surface morphology
of polymer coatings during the UV degradation process. With the noninvasive feature of LSCM, one can obtain thickness information
directly and nondestructively at various exposure times without destroying the specimens or deriving the thickness values
from IR measurement by assuming uniform film ablation. Two acrylic polymer coatings were chosen for the study, and the physical
and chemical changes of the two systems at various exposure times were measured and analyzed. Those measurable physical changes
caused by UV exposure include film ablation, formation of pits and other surface defects, and increases in surface roughness.
It was found in both coatings that changes in measured film thickness by LSCM were not correlated linearly to the predicted
thickness loss using the changes in the CH band obtained by the Fourier Transform Infrared (FTIR) spectroscopy measurements
in the later degradation stages. This result suggested it was not a uniform film ablation process during the UV degradation.
At later stages, where surface deformation became severe, surface roughness and profile information using LSCM were also proven
to be useful for analyzing the surface degradation process
Presented at the 81st Annual Meeting of the Federation of Societies for Coatings Technology, November 13–14, 2004 in Philadelphia,
PA. 相似文献
792.
吸附型固载二氧化氯释放特性的测定与应用研究 总被引:2,自引:1,他引:2
通过实验研究 ,定义并测定了吸附型固载二氧化氯的释放特性参数 ,并以临界释放速率UC =0 .0 0 5μg/(h·cm3)作为释放终点 ,将其分为长效、快速和中速释放 3种类型。长效型释放速率峰值Umax <2 0 μg/(h·cm3) ,峰值时间τmax >360h ,有效释放时间τcs >60d ;快速释放型Umax >60 μg/(h·cm3) ,τmax <1 2h ,τcs <7d ;中速释放型则处于两者之间。讨论了固载二氧化氯释放特性的控制方法和不同类型产品的适用范围 ,为产品释放特性的定量研究和应用开发提供了依据。 相似文献
793.
794.
Rare earth exchanged Na–Y zeolites, H-mordenite, K-10 montmorillonite clay and amorphous silica-alumina were effectively employed
for the continuous synthesis of nitriles. Dehydration of benzaldoxime and 4-methoxybenzaldoxime were carried out on these
catalysts at 473 K. Benzonitrile (dehydration product) was obtained in near quantitative yield with benzaldoxime whereas;
4-methoxybenzaldoxime produces both Beckmann rearrangement (4-methoxyphenylformamide) as well as dehydration products (4-methoxy
benzonitrile) in quantitative yields. The production of benzonitrile was near quantitative under heterogeneous reaction conditions.
The optimal protocol allows nitriles to be synthesized in good yields through the dehydration of aldoximes. Time on stream
(TOS) studies show decline in the activity of the catalysts due to neutralization of acid sites by the basic reactant and
product molecules and water formed during the dehydration of aldoximes. 相似文献
795.
通过大量试验分析了HPMC-E50和HPMC-F50在氯乙烯悬浮聚合中对PVC树脂的影响,从而确定了复合分散体系的质量分数以及分散剂的配比。结果表明,PVA和HPMC-E50复合分散体系的分散能力优于PVA和HPMC-F50复合分散体系;在悬浮聚合中,PVA和HPMC-E50复合分散体系与VCM的比例以0.05%~0.06%为宜;在PVA和HPMC-E50复合分散体系中,HPMC-E50所占比例以40%~60%为宜。 相似文献
796.
797.
798.
A novel method was developed for the fabrication of activated carbon fiber (ACF) with wet spinning polyvinyl alcohol (PVA) fibers as the precursors. Through a combination of preoxidation, dehydration, carbonization and activation under a certain tension, PVA-based ACFs (PVA-ACFs) with high yields and good mechanical properties were obtained. The surface and cross-section morphologies, pore structures, surface geometries, surface functional groups and crystal structures of the PVA-ACFs were characterized using field emission scanning electron microscopy, low temperature nitrogen adsorption, Fourier transformed infrared spectrophotometry, X-ray photoelectron spectroscopy and X-ray power diffraction. All the PVA-ACF samples prepared had lotus root-like axially meso- and macroporous structures with the domination of micropores. Fractal geometries of PVA-ACFs deduced from nitrogen adsorption isotherms indicates that capillary force dominated in the interactions between nitrogen and the PVA-ACFs. The surface functional groups of the PVA-ACFs depend on the activating agents. Graphitoidal crystal structures were observed for the PVA-ACFs. The small crystal size and short range ordering between the crystallites ensured a high specific surface area of the PVA-ACFs. 相似文献
799.
采用绿色合成法,在水相条件下,在Pd/C催化剂的作用下用苯甲酸催化氢化合成环己基甲酸.通过一系列的实验,得到了较好的合成环己基甲酸的工艺条件,在该条件下,能够得到比较纯的产物和较好的产物收率. 相似文献
800.
Summary Polysilanes with an optically active alkoxy group, i.e., (S)-(+)-2-butoxy, (R)-(-)-2-butoxy, (S)-(-)-2-methyl-1-butoxy, and (S)-(+)-3,7-dimethyl-1-octoxy, at the terminal positions, the chiral carbon centers of which were located at the α, β, and γ
positions relative to the oxygen, respectively, were prepared, and the effect of the position of chiral center of the terminal
optically active group on the induction of optical activity in polysilanes was investigated. The circular dichroism (CD) spectra
of these polymers showed positive Cotton signals around 340 nm at temperatures below -20 °C, but the intensities were small,
indicating that the optically active groups at the terminal positions have some ability, albeit small, to induce optical activity
to the polysilanes. Further, the optically active (S)-(+)-2-butoxy and (R)-(-)-2-butoxy groups did not control the helical sense direction of the polymers, despite the different chiral stimuli from
the 2-butoxy groups introduced to the terminal positions. To control the helical structure of polysilanes by the use of optically
active terminal groups, appropriate optically active groups are required. 相似文献