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61.
Masashi Shou Hiroyuki Takekawa Dong-Ying Ju Tokio Hagiwara Da-ling Lu Ken-ichi Tanaka 《Catalysis Letters》2006,108(3-4):119-124
Catalytic activity of a 1 wt% Au/TiO2 catalyst is markedly improved by loading a large amount of FeOx, on which the oxidation of CO in excess H2 is selectively promoted at temperature lower than 60 °C. Oxidation of CO with O2 on the FeOx/Au/TiO2 catalyst is markedly enhanced by H2, and H2O moisture also enhances the oxidation of CO but its effect is not so large as the promotion by H2. We deduced that activation of Au/TiO2 catalyst by loading FeOx is not caused by the size effect of Au particles but a new reaction path via hydroxyl carbonyl intermediate is responsible
for the superior activity of the FeOx/Au/TiO2 catalyst. 相似文献
62.
考察了助剂Mg、Ce修饰的纳米A l2O3负载N i催化剂对CH4、CO2重整反应制合成气的反应性能影响,采用正交实验筛选催化剂。结果表明,N i含量在9%~13%时,催化剂表现出较好的活性;随Mg含量的增加,反应活性基本呈下降趋势,说明Mg降低了催化剂体系的反应性能;Ce的加入总体上提高了反应活性,但是当Ce含量为3%时,反应活性最好;从不经预还原实验和低温点反应实验推断出,CH4和CO2重整反应中关键反应步骤是CH4的裂解;助剂Ce有利于提高催化剂的稳定性,而Mg却会使催化剂的稳定性下降很快。 相似文献
63.
Sutarawadee Monyanon Sangobtip Pongstabodee Apanee Luengnaruemitchai 《Journal of the Chinese Institute of Chemical Engineers》2007,38(5-6):435-441
The objective of this paper was to study a preferential oxidation (PROX) of carbon monoxide over monometallic catalysts including Pt, Au and Pt–Au bimetallic catalyst supported on ceria in hydrogen-rich reformate. Single step sol–gel method (SSG) and impregnation on sol–gel method (ISG) were chosen for the preparation of the catalysts. The characteristics of these catalysts were investigated by X-ray diffractometer (XRD), Brunauer–Emmet–Teller (BET) method, transmission electron microscope (TEM), scanning electron microscope (SEM) and temperature-programmed reduction (TPR). The XRD patterns of the catalysts showed only the peaks of ceria crystallite and no metal peak appeared. From TEM images, the active components were seen to be dispersed throughout the ceria support. The TPR patterns of PtAu/CeO2 catalyst prepared by SSG showed the reduction peaks were within a low temperature range and therefore, the catalysts prepared by SSG exhibited excellent catalytic activity for preferential oxidation of CO. Bimetallic Pt–Au catalyst improved the activity (90% conversion and 50% selectivity at 90 °C) because of the formation of a new phase. When the metal content of (1:1) PtAu/CeO2 catalyst prepared by SSG was increased, the CO conversion did not change much while the selectivity decreased in the low temperature range (50–90 °C). The CO conversion increased with increasing W/F ratio. The presence of CO2 and H2O had a negative effect on CO conversion and selectivity due to blocking of carbonate and water on active sites. 相似文献
64.
65.
Using TiO2 as carrier, CuO/TiO2 catalysts with different CuO loading were prepared by the impregnation method. The catalytic activities in NO+CO reaction
were examined with a micro-reactor gas chromatography reaction system and the methods of TPR, XPS and NO-TPD. It was found
that the catalytic activities were affected by pretreatment atmosphere, i.e. H2 atmosphere > reduction–reoxidation > 10%CO/He > reaction gas (fresh sample). NO decomposition was better by low-valence Cu
species than by high-valence Cu species, i.e. Cu0>Cu+>Cu2+. The XPS results indicated that Cu species on CuO/TiO2 were Cu0, Cu+, normal Cu2+(Cu2+(I)) and chain-structured Cu2+(Cu2+(II)) as –Cu–O–Ti–O–. The activities of Cu2+(II) were much higher than that of Cu2+(I), but both species were very unstable in the reaction atmosphere and easily reduced by CO, which accounted for the variable
activities of fresh catalysts with increasing reaction temperature. In NO+CO reaction, the redox process was a cycle of Cu+–Cu2+(I) at low reaction temperature but was a cycle of Cu0–Cu+ at high reaction temperature. As shown by NO-TPD, high catalytic activities could be attributed to the following factors,
e.g. oxygen caves on the catalyst’s surface after pretreatment with H2 and reduction–reoxidation, formation of Cu0 after pretreatment with H2, and increment of Cu species dispersion and formation of Cu2+(II) after pretreatment with reduction–reoxidation. 相似文献
66.
Cem??zdemir Ayse?Nilgün?Akin Ramazan?YildirimEmail author 《Korean Journal of Chemical Engineering》2003,20(5):840-843
The maximization of the total surface area of Pt-SnO2/Al2O3 catalyst was studied by using the Taguchi method of experimental design. The catalysts were prepared by sol-gel method. The
effects of HNO3, H2O and aluminum nitrate concentrations and the stirring rate on the total surface area were studied at three levels of each.
L9 orthogonal array leading nine experiments was used in the experimental design. The parameter levels that give maximum total
surface area were determined and experimentally verified. In the range of conditions studied it was found that, medium levels
of HNO3 and H2O concentration and lower levels of aluminum nitrate concentration and stirring rate maximize the total surface area. 相似文献
67.
为了减少CO爆炸给国民经济造成的巨大损伤,提出了一种能够快速地监测环境空气中痕量CO的气体传感器。由于CO分子基频吸收谱带的吸收线强要比泛频带和组合频带的吸收线强高出2~3个数量级,选择激射中心波长为4.65μm中红外量子级联激光器(QCL)作为光源,同时再配合长光程Herriott气室提高了CO体积分数检测下限。同时,该传感器采用单光源双探测器差分光学结构,消除了电调制光源所带来的不稳定性。实验表明:该传感器CO体积分数检测下限为2×10-6,并且操作人员可以通过替换在不同波长下运行的中红外QCL来测量其它气体。 相似文献
68.
Yong-Zhao Wang Yong-Xiang Zhao Chun-Guang Gao Dian-Sheng Liu 《Catalysis Letters》2007,116(3-4):136-142
Without use of any surfactant or oxidant, a series of Co3O4 catalysts have been prepared from cobalt nitrate aqueous solution via a very simple liquid-precipitation method with ammonium
acid carbonate followed by calcination at various temperatures. The catalytic performance of the Co3O4 for CO oxidation has been studied with a continuous flowing laboratory microreactor system. The results show that the CO
conversion of all the samples can reach 100% at ambient temperature. The catalyst calcined at 300 °C is able to maintain its
activity for CO complete oxidation more than 500 min at 25 °C and about 240 min even at −78 °C. High reaction temperature
results in a high catalytic stability, while the catalytic stability decreases with further increasing the reaction temperature.
Characterizations with X-ray powder diffraction and transmission electron microscopy suggest that all the samples exist as
a pure Co3O4 phase with the spinel structure, the samples are apt to aggregate and the specific surface area gradually decreases with
increasing the calcination temperature, which directly leads to the decrease of catalytic stability. Furthermore, the amount
of active oxygen species measured by CO titration experiments appears to be critical for catalytic performance. 相似文献
69.
吡啶为助剂合成甲酸甲酯的动力学研究 总被引:1,自引:0,他引:1
在60~90℃对以吡啶为助催化剂由一氧化碳合成甲酸甲酯的反应进行了动力学研究。结果表明该反应为2级反应,速率方程rυ=-dpco/dt=k[MOH]pco,无助催化剂时反应活化能Ea=67.63kJ/mol,反应速率常数k=9.66×106exp(-67.63×103/RT)(mol-1·L·min-1);当有助催化剂存在时,反应活化能为Ea=61.19kJ/mol,反应速率常数k=8.82×106exp(-61.19×103/RT)(mol-1·L·min-1)。并对助催化剂吡啶的助催化机理进行了探讨。 相似文献
70.
Various commercial supported palladium hydrogenation catalysts were studied by XPS and treated at ambient pressure with hydrogen and air. Unused catalysts exhibit a significant fraction of divalent Pd (oxide) which is reduced by hydrogen treatment at room temperature. Exposure to air in systems with carbonate, alumina, silica or active carbon as support causes the formation of a solid solution of oxygen in Pd characterized by a Pd 3d chemical shift of ca. + 0.4 eV. The absolute binding energy of Pd depends strongly on the matrix, indicating a significant contribution of extra-atomic screening, which prevents a direct comparison of reference samples and supported catalysts. Using the oxidation of CO to CO2 at 300 K as in situ chemical probe it was confirmed that Pd supported on carbonate, silica and alumina exists in the same metallic state which could be activated for the test reaction irrespective of the variation in XPS binding energies. 相似文献