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81.
实验以MgO/MCM-22为催化剂,在气相连续流动固定床反应器上催化苯与草酸二乙酯(DEO)烷基化,合成乙苯(EB)。考察了MgO负载量变化和工艺条件的影响。以硝酸镁为前驱体通过等体积浸渍法制备了MgO/MCM-22催化剂,并以低温N_2吸附脱附、X射线衍射、NH_3-TPD、吡啶吸附IR等,对催化剂进行了表征。实验结果表明:随MgO负载量的增加,苯的转化率逐渐下降,而乙苯的选择性明显提高,这主要是由于负载MgO后催化剂的酸性位数量下降引起的。以MCM-22为催化剂,在最佳反应条件下:温度653 K,空速为2 h~(-1),原料配比n(苯):n(DEO)=4:1,苯的转化率为37.5%,乙苯选择性为80.3%。 相似文献
82.
基于松下FP2-PLC和运动控制模块PP41,采用步进电机和编码器方式实现了位置的闭环控制,将三轴的轴向位置精度控制在0.5μm以内。使位置闭环系统能够在低成本下实现。 相似文献
83.
A. O. Bianchi M. Campanati P. Maireles-Torres E. Rodriguez Castellon A. Jimenz Lpez A. Vaccari 《Applied Catalysis A: General》2001,220(1-2):105-112
Si/Zr mesoporous MCM-41 catalysts were investigated in the vapour phase synthesis of 7-ethylindole (7-ETI) starting from 2-ethylaniline (2-ETAN) and ethylene glycol (EG). The catalysts were prepared from the corresponding alkoxides in the presence of a cationic surfactant, which acts as a structure-directing agent. After removal of the surfactant, the resulting mesoporous solids were characterised by X-ray diffraction, N2 adsorption–desorption, temperature programmed desorption (TPD) of NH3 and pyridine adsorption coupled with FTIR spectroscopy. As the amount of ZrO2 increased in the catalysts, the BET surface area decreased, while an enhancement of the acidity took place. The activation of EG to 2-hydroxyacetaldehyde and its attack on 2-ETAN, leading to the formation of 7-ETI, was favoured by increasing the amount of ZrO2 The maximum yield for the catalyst was obtained with ca. 50 wt.% of ZrO2, which promoted the presence of Lewis and Brönsted acid sites of suitable strength and concentration, although mesoporous catalysts exhibited very good regenerability. 相似文献
84.
85.
This paper reviews a series of results, partly published recently, on niobosilicate mesoporous molecular sieves of MCM-41 type modified with noble metals (Pt, Au). Platinum is introduced to MCM-41 by impregnation technique, whereas gold is incorporated by two methods: during the synthesis by co-precipitation (COP) and by impregnation (IMP). Three fundamental features of the prepared materials have been considered: (i) texture/structure, (ii) noble metal state and dispersion, and (iii) catalytic activity. The latter has been tested in selective reduction of NO by propene, methanol oxidation and WGS process. The role of niobium, as well as the effect of the nature of noble metals and the preparation method on the physicochemical and catalytic properties of the final materials based on NbMCM-41 (in comparison with siliceous MCM-41) is demonstrated. 相似文献
86.
Mesoporous MCM-41 type silica spheres having a sub-micrometer size were synthesized following an adaptation of Stöber's method. This parent material was then functionalized with 3-aminopropyl triethoxysilane and with 3-propanonitrile triethoxysilane, followed by oxidation of the cyano-group to the corresponding carboxy-group. After proper characterization, the samples were loaded with cisplatin and subjected to in vitro tests in order to obtain the corresponding drug release profile. The carboxy-functionalized MCM-41 sample was found to show a release kinetics that should facilitate controlled drug delivery over a significantly larger time period (about 140 h) than both, unmodified MCM-41 and amino-functionalized MCM-41 samples. 相似文献
87.
In this work, the thermal stability of mesoporous structure of MCM-41 materials with different zirconium contents (Zr-MCM-41) was investigated. The results show that the obtained Zr-MCM-41 materials retain a relatively good long range order of mesopores up to 1000 °C. Increasing the calcining temperature to 1050 °C, the mesopore openings become anisotropic and a few new pores with dozens of nanometers are formed due to thermal stress effect. After calcination at 1100 °C, the mesopores structure of all the samples collapse completely and some tetragonal zirconia can be also detected in the sample with high zirconium content (15 ≤ Si/Zr ≤ 40). The synthesized Zr-MCM-41 materials with good thermal stability are expected to be used as the support of catalytic activators under process conditions. 相似文献
88.
K. Vidya S. E. Dapurkar P. Selvam S. K. Badamali N. M. Gupta 《Microporous and mesoporous materials》2001,50(2-3):173-179
A method based on direct template-ion-exchange was employed for the entrapment of UO22+ ions in MCM-41 and MCM-48 molecular sieves via swapping of cetyltrimethylammonium cations present in the mesoporous channels by the UO22+ ions in an aqueous solution. The samples were characterized by XRD, FT-IR, and ICP-AES techniques. The entrapment of UO22+ ions is facilitated by the large pore size vis-a-vis the high surfactant content in the as-synthesized host materials. A higher loading of UO22+ ions was achieved in MCM-48 as compared to MCM-41, which could be attributed to its three-dimensional pore system and higher surfactant-to-silica ratio. FT-IR results provide an evidence of a strong binding of UO22+ groups with the defect silica sites of mesoporous molecular sieves. 相似文献
89.
90.
SiW12/MCM-41催化剂的合成及对三醋酸甘油酯反应的影响 总被引:6,自引:1,他引:6
制备了负载H3SiW12O40(SiW12)杂多酸的SiW12/MCM-41催化剂,用XRD等方法对其结构进行了表征.以SiW12/MCM-41为催化剂对合成三醋酸甘油酯的反应进行了研究,并与其它几种分子筛催化剂HMCM-41、Hβ、BAPO-5、SAPO-5的催化性能进行了对比,筛选出合成三醋酸甘油酯的反应性能较好的负载型催化剂SiW12/MCM-41.然后在SiW12/MCM-41催化剂下通过单因素实验对SiW12的负载量、催化剂的活化温度、酸醇摩尔比等因素考察,并对冰醋酸和甘油的酯化反应进行了优化.得出最佳操作条件SiW12/MCM-41催化剂的最佳负载质量分数为50%,催化剂焙烧温度为300 ℃,醇酸摩尔比为1∶5,反应温度为125 ℃,反应时间为4~5 h. 相似文献