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71.
The oxidation behavior of Ni—20Cr foils of 100- and 200-m thickness wasstudied in air between 500 and 900°C. Simultaneously, the morphology,microstructure, and composition of the oxide layers were determined byscanning and transmission electron microscopies. Depending on thetemperature, the oxide layer differed significantly. The scale formedat all temperatures was complex, with an outer NiO layer having columnargrains, and an inner layer of equiaxedNiCr2O4+NiO+Cr2O3 grains. At low temperatures (500 and 600°C),the chromium content was insufficient to form a continuousCr2O3 layer, while such a continuous layer formed at theinner interface at oxidation temperatures of 700 to 900°C. At 600°C,internal oxidation of chromium occurred in the substrate. The oxidationmechanism is described taking into account these morphologies and theoxidation kinetics. The observation of no significant differences betweenthe oxidation behavior of thin strips and thick materials is related to thelimited exposure times of the study. 相似文献
72.
73.
G. X. Zhao M. Zheng X. H. Lv X. H. Dong H. L. Li 《Metals and Materials International》2005,11(2):135-140
The corrosion behavior of 13Cr martensitic stainless steel in a CO2 environment in a stimulated oilfield was studied with potentiodynamic polarization and the impedance spectra technique. The
results showed that the microstructure of the surface scale clearly changed with temperature. This decreased the sensitivity
of pitting corrosion and increased the tendency toward general (or uniform) corrosion. The capacitance, the charge transfer
resistance, and the polarization resistance of the corrosion product scale decrease with increasing temperature from 90 to
120 °C, and thus the corrosion is a thermal activation controlled process. Charge transfer through the scale is difficult
and the corrosion is controlled by a diffusion process at a temperature of 150 °C. Resistance charge transfer through the
corrosion product layer is higher than that in the passive film. 相似文献
74.
75.
在以前的研究中,发现熔渣中陶瓷材料的腐蚀主要依赖于渣的粘度和陶瓷与熔渣之间的碱性缝隙。本研究是在腐蚀测试的基础上,推荐用渣的粘度和碱性缝隙函数方程来预测陶瓷材料在熔渣中的腐蚀率。Cr2O3-Al2O3陶瓷材料是放在SiO2-CaO-B2O3碱性熔渣中进行测试的。 相似文献
76.
Unni Olsbye Anastasia Virnovskaia Øystein Prytz Stan J. Tinnemans Bert M. Weckhuysen 《Catalysis Letters》2005,103(1-2):143-148
A Cr/Al2O3 alkane dehydrogenation catalyst exhibits a maximum in ethylene yield during an ethane dehydrogenation cycle. Isotopic labelling experiments with monolabelled 13C-ethane and deuterium were used to elucidate whether the initial activity increase could be due to formation of an active, larger hydrocarbon intermediate on the surface. The results strongly indicate that this is not the case, and instead point to a traditional reaction cycle involving adsorption of ethane to form an ethyl species, followed by desorption of ethene and hydrogen. Transient kinetic data suggest that ethane adsorption is the rate-determining step of reaction. 相似文献
77.
Spectroscopic evidence for the interaction of hydroxyl groups and chromium ions was obtained using a catalyst prepared from chromyl chloride. A new OH peak, observed at 3705 cm–1 after pumping away CO gas, is attributed to the direct interaction of OH with the low-valent chromium. This peak shifts to 3590 cm–1 on contact with O2 at room temperature and it is assigned to a hydroxyl interacting with the oxidized chromium. New assignments are also proposed for IR bands of CO presorbed on the catalyst. The peak due to CO at 2188 cm–1 decreases as the OH intensity at 3705 cm–1 increases, suggesting that the former peak arises from adsorption on Cr(II) species to which two oxygen atoms are attached. 相似文献
78.
研究了HF +HCl消解样品 ,试液用ICP -AES法同时测定TAM胶粘剂中铅、镉、汞、铬、砷的新方法。在选定的最佳条件下测铅、镉、汞、铬、砷的检出限分别为 0 .0 0 15、0 .0 0 0 8、0 .0 0 11、0 .0 0 17、0 .0 0 0 9μg·L- 1 ,回收率为 93 .5 %~ 10 8.3 % ,RSD为 0 .62 %~ 5 .65 %。该法准确、快速、简便 ,应用于TAM胶粘剂的测定 ,结果满意 相似文献
79.
Tz. Boiadjieva D. Kovacheva K. Petrov S. Hardcastle A. Sklyarov M. Monev 《Journal of Applied Electrochemistry》2004,34(3):315-321
The effect of polyethylene glycol (PEG 1500) as additive and of deposition conditions on Zn—Cr alloy electrodeposition from an acidic sulfate electrolyte at room temperature, without agitation was investigated. PEG polarizes the overall cathodic reaction and inhibits Zn deposition. Cr codeposition with Zn starts at a cathodic potential of about –1,95 V vs Hg/Hg2SO4, which is reached at current density of about 20 A dm–2 in galvanostatic conditions. Zn—Cr alloy coatings containing up to 28 at % Cr were obtained depending on the plating conditions. SEM observations showed an island-like structure, formed by the local growth of crystals, which covered the surface during further deposition. In the first stages of electrodeposition the powder diffraction spectra contain lines of b.c.c. -(Zn,Cr) phase (a
3.02 Å). After 30 s deposition time weak lines of Zn-based phase (a
2.67 Å, c
4.90 Å) appear, and become clearly visible in coatings deposited for 90 s. The average Cr content in the alloy coatings decreases with advancing deposition. The as-plated surface contains C in organic compounds and Zn(OH)2. After 50 min sputtering, Zn and a mixture of Cr, Cr2O3 and Cr7C3 were found. The presence of organic C and O, probably from inclusions of PEG, were also detected. 相似文献
80.
00C r22N i5M o3N不锈钢是双相不锈钢,它的固溶组织中α铁素体相和γ奥氏体相约各占一半。经过试验分析它的击破电位,保护电位,室内化学浸泡试验结果都证明它具有优良的耐点腐蚀性能;通过试验还证明它同时具有优良的耐均匀腐蚀和缝隙腐蚀的性能。 相似文献