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41.
Graphitic porous carbon sheets (GPCS), which were synthesized at a low temperature of 900°C by KOH chemical activation technique, possess a specific surface area of 1246 m2 g-1 with high pore volume. The size of the pores varied in micro-mesopore regions and exhibited three-dimensional sheet-like morphology composed of multilayered graphene sheets with an inter planar distance of 0.360 nm. The GPCS material was tested as anode for Li-ion battery (LIB) application in half cell mode (vs Li+/Li). The fabricated GPCS electrode shows excellent electrochemical properties in comparison with commercial graphite such as a high discharge specific capacity of 1022 mA h g-1 after 10 cycles at 100 mA g-1 and excellent specific capacity retention of 170 mA h g-1 at a very high current rate of 8000 mA g-1 and also retains a high capacity of 541 mA h g-1 after 250 cycles at 500 mA g-1, which suggests that GPCS material can be a promising electrode for LIB application. A brief comparison with commercial graphite and various carbonaceous materials from literature demonstrated that the GPCS electrode was potential material for high rate LIBs. 相似文献
42.
《International Journal of Hydrogen Energy》2019,44(8):4167-4176
Dry reforming of methane was carried out using isotopic 13CO2 and C18O2 gases over a Ni-based pyrochlore catalyst that was synthesized using the modified Pechini method. In this method, 1 wt% Ni was doped into the La2Zr2O7 pyrochlore structure. The catalyst was characterized by H2-TPR, TPO, and XRD and tested for its methane reforming activity under CO2 dry-reforming reaction conditions.The results of repeated TPR/TPO cycles up to 950 °C showed that the consecutive TPR profiles were nearly identical, indicating that the catalyst was stable at high temperatures, and that the nickel oxidation/reduction processes were reversible. The dry-reforming experimental results using labelled 13CO2 gas showed the syngas production for this material proceeded through the activation of CH4 with O that came from breaking one of the CO bonds of CO2 with the latter reaction (CO2 activation) likely occurring at oxygen vacancies at or near the Ni particle-pyrochlore interface. It was also found that only a small portion of the CO originated from CH4. A variation of the same experimental test, but using 12C18O2, revealed only 12C18O was formed and no 12C16O was detected, ruling out the possibility of reaction with the lattice oxygen in the catalyst structure with this material. Over this catalyst, the activated CH4 appeared to dissociate to elemental carbon on the catalyst surface, which was determined to be the source of carbon from a post reaction TPO of the catalyst that was exposed to the 13CO212CH4 mixture. No carbon deposition appeared to originate from 13CO2. 相似文献
43.
Activation of Candida antarctica lipase B in pressurized fluids for the synthesis of esters 下载免费PDF全文
44.
Novel dynamic semiempirical proton exchange membrane fuel cell model incorporating component voltages 下载免费PDF全文
This paper introduces a novel dynamic semiempirical model for the proton exchange membrane fuel cell (PEMFC). The proposed model not only considers the stack output voltage but also provides valid waveforms of component voltages, such as the no‐load, activation, ohmic, and concentration voltages of the PEMFC stack system. Experiments under no‐load, ramping load, and dynamic load conditions are performed to obtain various voltage components. According to experimental results, model parameters are optimised using the lightning search algorithm by providing valid theoretical ranges of parameters to the lightning search algorithm code. In addition, the correlation between the vapour and water pressures of the PEMFC is obtained to model the component voltages. Finally, all component voltages and the stack output voltage are validated by using the experimental/theoretical waveforms mentioned in previous research. The proposed model is also compared with a recently developed semiempirical model of PEMFC through particle swarm optimisation. The proposed dynamic model may be used in future in‐depth studies on PEMFC behaviour and in dynamic applications for health monitoring and fault diagnosis. 相似文献
45.
研究了不同的热处理工艺对C-276合金冷轧无缝管晶粒长大行为的影响。结果表明:在同一保温时间下,随热处理温度的升高,C-276合金的晶粒尺寸逐渐增大,且不同保温时间下的晶粒长大趋势相同。当热处理温度为1040~1080 ℃时,晶粒长大较快;在1080~1160 ℃时放缓;在1160~1200 ℃时又加快。在1040~1200 ℃下保温10 min后C-276合金的晶界迁移表观激活能为313.77 kJ/mol。当热处理温度为1040~1080 ℃时,随保温时间的延长晶粒长大较为缓慢;温度为1120~1160 ℃时,当保温时间在10 min内,晶粒长大较快,当保温时间大于10 min后晶粒长大减慢;温度升高到1200 ℃时,随保温时间的延长晶粒长大趋势较为平缓。热处理温度在1040~1200 ℃范围内,随温度的升高,C-276合金的晶粒长大动力学时间指数η先增大后减小。 相似文献
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48.
Chiamaka Obianyor Gary Newnam Bryce E. Clifton Prof. Martha A. Grover Prof. Nicholas V. Hud 《Chembiochem : a European journal of chemical biology》2020,21(23):3359-3370
Chemical ligation is an important tool for the generation of synthetic DNA structures, which are used for a wide range of applications. Surprisingly, reported chemical ligation yields can range from 30 to 95 % for the same chemical activating agent and comparable DNA structures. We report a systematic study of DNA ligation by using a well-defined bimolecular test system and a water-soluble carbodiimide (EDC) as a phosphate-activating agent. Our results emphasize the interplay between template-substrate complex stability and the rates of the chemical steps of ligation, with 3′ phosphate substrates providing yields near 100 % after 24 hours for particularly favorable reaction conditions. Ligation rates are also shown to be sensitive to the identity of the base pairs flanking a nick site, with as much as threefold variation. Finally, the observation that DNA substrates are modified by EDC at rates that can be comparable with ligation rates emphasizes the importance of considering side reactions when designing protocols to maximize ligation yields. 相似文献
49.
过氧单硫酸盐(PMS)及过二硫酸盐(PDS)在工业污染场地修复中应用广泛,通过活化作用能够产生氧化性更强的· 自由基,从而更好地氧化降解有机污染物。本文比较了几种典型活化方式,包括紫外(UV)、碱、过渡金属、热以及含碳物质,并分析了它们的优缺点及适用条件;讨论了过硫酸盐活化机理及动力学过程;分析了无机阴离子(Cl-、 、 、 、 、 )与· 自由基相互作用及其对有机污染物氧化降解的影响;针对活化过硫酸盐在工业污染场地修复领域的应用,对过硫酸盐活化方法的发展趋势进行了展望。理论研究和实践表明,过硫酸盐不同活化方式为工业污染场地修复提供了多样选择,多种活化方式协同作用将是过硫酸盐高效活化氧化降解有机污染物的发展方向。由于Cl-、 抢夺· 的能力较强,认为这些无机盐与有机物复合的污染场地或土壤采用PDS修复需格外谨慎选择活化方法。 相似文献