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81.
Michael W. Anderson 《Topics in Catalysis》1996,3(1-2):195-220
The power of solid-state NMR for the interrogation of porous catalytic materials is illustrated using three examples. First,
for the investigation of catalytic processes occurring within the confines of a microporous catalyst NMR is shown to reveal
both the details of shape-selectivity and the nature of internal surface species. Second, NMR is shown to be a powerful short-range
tool to reveal precise structural information on highly disordered microporous titanosilicates. Despite long-range disorder
the short-range order is maintained and can be easily studied. Finally, the same utility of probing short-range chemical phenomena
is shown to be crucial for the investigation of novel-ordered-amorphous-mesoporous materials known generically as M41S. This
class of material is currently one of the most important with potential catalytic application. 相似文献
82.
制备轻油蒸汽转化制氢镍催化剂新的共浸法 总被引:2,自引:0,他引:2
用一种新的共浸法制备一批轻油蒸汽转化催化剂样品。运用TG、DTG、DSC和XRD进行的研究发现,与一般共浸法相比,这种着重提高组份间相互作用的新制法有利于提高镍催化剂的活性、抗积炭性、稳定性和金属镍的分散度,并发现用新法制备的催化剂样品,在水热初期约30小时的过程中,出现了镍晶粒先聚集再分散的新现象。 相似文献
83.
84.
Cu ion co-ordination-location in zeolites of MFI, erionite, mordenite matrices has been determined and the activity of the individual Cu sites compared for NO decomposition and its selective reduction by hydrocarbons or ammonia. It appears that Cu ions in the vicinity of one framework Al (site II), able to form stable Cu+-dinitrosyl complexes, and abundant in MFI structure, are responsible for high activity in NO decomposition. The Cu ions neighbouring two framework Al atoms (site I), and forming mostly mononitrosyl complexes, which dominate in erionite structure, provide a high activity in selective reduction of NO. 相似文献
85.
通过对活性炭载体进行不同条件的超声波处理获得了具有不同表面化学性质的载体,使用比表面积(BET)、酸碱滴定等技术手段对载体的物理化学性质进行了表征。将经过超声波处理的活性炭载体制备成Pt/C催化剂,并将催化剂直接用于催化反应,考察了活性炭载体的不同超声波处理条件对Pt/C催化剂性能的影响。实验发现,活性炭载体经过超声波处理后,表面灰分含量、pH值和中孔孔容有较大的变化;使用经过60min超声波处理后中孔孔容较大的活性炭作为载体制备的Pt/C催化剂,在催化加氢反应性能测试中显示了最高的催化活性。在此基础上,就活性炭载体的超声波处理对Pt/C催化剂活性的影响进行了讨论。 相似文献
86.
Two commercial SCR catalysts, with a nominal W content of about 9 wt.% and a V nominal content of 0.55 and 1.8 wt.%, respectively, were contacted with different amounts of Na and K and with HCl vapours in order to simulate poisoning by species more specifically contained in exhaust gases from MSW combustion. Catalysts were characterised using XRD analysis, SEM/EDX analysis, BET and pore size distribution measurements, NH3 TPD, TG analysis. Poisoning agents do not cause loss of surface area nor pore occlusion. A significant loss of surface acidity was observed upon alkali metals poisoning whereas a decreasing of vanadium content was observed for the more concentrated catalysts upon HCl poisoning. Catalysts deactivation is proportional to the number of acid sites neutralised by alkali metals adsorbing ammonia in the temperature range typical of SCR process. HCl promotes the formation of new acid sites showing a lower activity compared to the original one. 相似文献
87.
The influence of 0.1-0.6 at.-%RE additions (RE= La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Yb) on themechanical properties of Pd was studied. All above RE additions increased not only the strengthproperties at ambient temperature but also the tensile strength, creep rupture time and activation en-ergy at high temperatures, simultaneously increased the elongation of Pd. In the range of dilute con-centration, the strength properties of Pd-RE alloy enhanced linearly with RE concentration. Whenthe strength properties of Pd-RE alloys were normalized at 0.1 at.-%RE, it was found that light REelements had stronger effect on the properties of Pd than heavy RE, whereas Eu, Yb, Ce had anoma-lous effect. In all Pd-RF alloys, Pd-Eu alloy had the highest strength properties, successively Pd-Yband Pd-Ce alloy. The effect mechanisms of RE in alloy, such as purifying impurities, increasingrecrystallization temperature, refining grain size. expanding crystal lattice, increasing dislocation den-sity and decreasing stacking fault energy, forming stable RE oxidation by internal oxidation, and soon, were observed. They were strengthening sensitive factors. The influence of the factors onstrength properties and elongation of Pd was discussed. 相似文献
88.
A series of 0.6 wt% Pt/BaL catalysts with different alkali cations have been tested for heptane reforming at 440 ° C, 0.16 atm heptane, 0.95 atm H2, 6.7 atm He, 3 to 5 h of reaction, and conversions between 2 and 10%. As the cations in the zeolite are progressively changed from lithium to cesium, the turnover rates for hydrogenolysis and dehydrocyclization increase by about 5–10 times, while the turnover rate for isomerization remains unchanged. Since the turnover rates for hydrogenolysis and dehydrocyclization are similarly affected, exchanging lighter alkali cations for heavier ones increases the aromatics selectivity by a small amount, from 72 to 82%. These results indicate that metal-support interactions have a moderate effect on the heptane reforming activity, but only a weak effect on the selectivity. 相似文献
89.
乙烯直接氧化合成乙酸 总被引:2,自引:0,他引:2
用常规固定床反应器考察了Pd-SiW12/SiO2催化剂还原条件对乙烯直接氧化合成乙酸催化性能的影响。催化剂用H2在200-300℃还原后Pd 的分散度较高,其催化活性远高于肼在液相中还原的催化剂,在乙烯气相氧化合成乙酸反应的原料气中,适量1,2-二氯乙烷的存在有助于提高乙酸的选择性和时空产率,初步考察了Pd-Se-SiW12/SiO2催化剂连续206h运转的稳定性,结果表明,催化剂中Pd晶粒的长大和硅钨酸的流失是造成催化剂失活的主要原因。 相似文献
90.