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821.
The adsorption, decomposition of CH3 and its reactions with CO2 were followed by means of Fourier transform infrared spectroscopy combined with mass spectrometry. Methyl radicals were produced
by the pyrolysis of azomethane. Absorption bands, observed at room temperature adsorption, were attributed to adsorbed CH3 and CH3O species. The decomposition of adsorbed CH3 in vacuum started above 400 K and was accelerated by CO2. In the study of the interaction of methane with titania, activated in different ways, we found no convincing spectroscopic
evidence for the activation of methane at 300 K.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
822.
Methane conversion to higher hydrocarbons in a “one‐step” process under non‐oxidative conditions at low temperature was here
first introduced and investigated over Co–Pd/SiO2 catalysts at 250°C as a function of hydrogen concentration in helium and of catalyst composition. A maximum in the production
of C2+ hydrocarbons including aromatics (benzene and toluene) was observed at 1.3 vol% H2/He mixture in which one pulse of methane was introduced. Additional hydrogenation with the same H2/He mixture at 400°C was efficient to remove the larger hydrocarbon fragments already existing on the surface. On pure Pd/SiO2 the one‐step process is not so efficient as on cobalt‐rich samples, but in the latter case the hydrocarbon removal is the
most efficient during high‐temperature hydrogenation. It was found that methane conversion in the one‐step process is at least
2.5 times greater than that measured in the “two‐step” process and, in some cases, 80% of the methane introduced is converted
to larger hydrocarbons. The results are discussed in terms of the hydrogen coverage ensuring the optimum hydrogen content
in the surface CHx species leading to chain growth.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
823.
824.
825.
甲烷在固体氧化物燃料电池阳极氧化性能研究 总被引:4,自引:4,他引:0
报告了甲烷在固体氧化物燃料电池(SOFC)阳极直接氧化的实验结果。试验表明,甲烷在阳极的氧化过程存在多种反应机制,反应机制取决于电池工作温度和反应空速等。随着温度的升高,甲烷转化率提高,H2和CO生成量也不断增加。在SOFC中甲烷不是按完全氧化反应方式进行,而是部分氧化反应过程。随着反应空速的增大,甲烷转化量及H2和CO的生成量呈下降趋势。研究发现,干甲烷气作为燃料时,阳极表面可能产生积碳。当电池中通入氧气或水蒸汽时可以消除积碳。在考察NEMCA效应对SOFC电性能的影响时发现,当外加与电池内部电场同向的电场时,能促进O2-溢流到阳极表面,改变催化剂的表面功函,改善SOFC电性能。 相似文献
826.
Eric M. Kennedy Kai Li Behdad Moghtaderi Bogdan Z. Dlugogorski 《Chemical Engineering Communications》1999,176(1):195-200
We report the results of an experimental and kinetic modeling study of gas-phase reaction between methane and halon 1301 (CBrF3). At 1000 K, with an equimolar feed of CH4 and CBrF3 and at a residence time of 1 second, CHF3 and CH3Br are produced at selectivities in excess of 90%. Other reaction products detected include C2H2F2, C2H2, C2H2, and CHBrF2. Very good agreement between kinetic modeling and experimental results was obtained. 相似文献
827.
Tomoyuki Inui 《Catalysis Today》1999,51(3-4):361-368
Recent advances in catalysis for solving the energy and environmental problems are summarized. For these purposes, rapid conversion and selective reaction even under conditions deviating extremely from reaction stoichiometry must be indispensable requisites. In order to realize these requisites, changes in the state of catalyst surface during the reaction were studied, and the catalyst structures on which the optimum reaction performance occurs were determined. An ultra-rapid reforming of methane to syngas with a space–time yield (STY) of 25 000 mol/l h was achieved by using a Rh-modified Ni–Ce2O3–Pt catalyst in which the Rh played the role of portholes for hydrogen spillover and prevents coke deposition on the catalyst surface. As a result, a stable state of the catalyst and the high reaction rate were exhibited. A new catalyst composed of Cu–Zn–Cr–Al–Ga oxides modified with supported Pd exerted a high activity with a high STY of methanol, 6700 g/l h. The catalyst components, Pd and Ga, controlled the reduction state of the catalyst surface by their role on normal and inverse spillover of hydrogen, respectively. The methanol thus produced was then totally converted selectively on a metallosilicate catalyst containing Ga or Fe into an aromatics-lean gasoline using an STY of 1860 g/l h. Finally, non-linear reaction mechanism is used to explain the elimination of NO on metallosilicate catalysts under O2-excess conditions. 相似文献
828.
中国煤储层岩石物理学因素控气特征及机理 总被引:20,自引:1,他引:19
基于全国主要矿区或勘探区统计资料,总结了煤级、煤岩类型、显微组分组成等煤的岩石物理学因素与煤层含气量、吸附性、渗透性等之间的关系,探讨了煤储层岩石物理学特征的控气作用机理.发现煤级-含气量的“包络线”具有阶段性演化规律,最大含气量的显著变化与煤化作用阶跃高度一致,煤储层含气量较高的地区沿纬向等间距展布且与较高煤级煤分布区吻合,煤的兰氏体积与镜质组含量关系中存在一个镜质组含量临界值.指出不同煤化作用阶段控气作用的实质在于煤物理结构和化学结构的演化,沉积作用控气的思路对煤储层渗透率非均质性预测具有一定实践意义. 相似文献
829.
甲烷排放源及减排对策 总被引:11,自引:0,他引:11
甲烷是一种比较重要的温室气体,它对温室效应的作用仅次于二氧化碳。据估计,目前全球每年排放的甲烷总量为535Mt,其中,通过石油与天然气工业,煤炭开采、固体废物堆存,污水处理、水稻种植、反刍家畜饲养以及生物质燃烧等人类活动排放的甲烷约占70%,根据国际能源署的有关调查与研究资料,比较系统地介绍了上述各种主要甲烷排放源及相应的减排对策。 相似文献
830.
The induction period of dehydrogenation and aromatization of methane over Mo/HZSM-5 was studied by combining a pulse reaction
method with TPSR, UV laser Raman, and 13C CPMAS NMR techniques. BET and XRD results showed that Mo species were well dispersed on/in the zeolite. TPSR in CH4 stream revealed that Mo species were reduced in at least two different stages before the formation of benzene. TPR results
were in agreement with TPSR results. The two stages might be attributed to the reduction of two kinds of Mo6+ species to low valence Mo species. One was polymolybdate MoO3, and the other was crystalline MoO3. UV Raman spectra showed the existence of octahedrally coordinated polymolybdate species. XRD, however, did not detect any
crystalline MoO3, possibly because they were too small to be detected with this technique. Pulse reaction results indicated that pre-reduction
of the catalyst and formation of carbonaceous deposit could shorten the induction period. It is concluded that the formation
of active sites during the induction period via partial reduction of Mo6+ species and formation of carbonaceous deposit on partially reduced Mo species is of significance for methane aromatization
over Mo/HZSM-5.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献