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31.
Annealing effect of amorphous carbon thin films on Si(1 0 0) substrates is studied by normal incidence and angle dependent carbon K-edge X-ray absorption near-edge structure (XANES) spectroscopy. The angle dependence of the XANES signal shows that the graphitic basal planes are oriented perpendicular to the surface when the film is annealed at 1000 °C. Micro-Raman spectroscopy reveals two well-separated bands the D band at 1355 cm−1 and G band at ∼1600 cm−1, and their ID/IG intensity ratio indicates the formation of more graphitic film at higher annealing temperatures. X-ray diffraction pattern of 1000 °C temperature annealed film confirms the formation of graphite structure. 相似文献
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Using a sol‐gel method Pb0.8Ba0.2ZrO3 (PBZ) thin film with a thickness of ~320 nm was fabricated on Pt(111)/TiOx/SiO2/Si substrate. The analysis results of XRD, SEM, and dielectric properties revealed that this thin film is a (111)‐oriented nano‐scaled antiferroelectric and ferroelectric two‐phase coexisted relaxor. Calculations of dielectric tunability (η) and figure‐of‐merit (FOM) at room temperature display a maximum value of 75% at E = 560 kV/cm and ~236, respectively. High‐temperature stability (η > 75% and FOM > 230 at 560 kV/cm in the range from 300 to 380 K) and high breakdown dielectric strength (leakage current < 1 nA at 598 kV/cm) make the PBZ thin film to be an attractive material for applications of tunable devices. 相似文献
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Rong Hua Zhang De An Shi Chi Pong Tsui Chak Yin Tang Sie Chin Tjong Robert Kwok Yiu Li 《Polymer Engineering and Science》2011,51(2):403-410
Compatibilized polypropylene (PP)/polyamide (PA6) blends with and without β nucleating agent (β‐NA) are prepared, and are designated as Blend‐0.3 and Blend‐0, respectively. The melting and crystallization characteristic of the blends crystallized under different cooling rates and different crystallization temperatures are studied. It is observed that high β‐PP content can be developed in Blend‐0.3 only at slow cooling rates (<5°C/min), whereas high α‐PP content is formed at fast cooling rates. Isothermal crystallization analysis of Blend‐0 indicates that PA6 is an effective NA for α‐PP in the lower temperature range, whereas the α‐nucleating effect disappears in the higher temperature range. Blend‐0.3 can, therefore, be viewed as a system containing both α‐ and β‐NAs, simultaneously. PA6 is competing with β‐NA in inducing PP crystallization. Under the normal injection of Blend‐0.3, the melt will be cooled through the higher temperature that favors the effectiveness of β‐NA rapidly because of the faster cooling rate. However, the α‐nucleation effect from PA6 predominate at the lower temperature. This explains the difficulty in obtaining high β‐PP content in Blend‐0.3 from injection molding. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers 相似文献
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Huiqing Fan Gun-Tae Park Jong-Jin Choi Hyoun-Ee Kim 《Journal of the American Ceramic Society》2002,85(8):2001-2004
A sol–gel-derived Pb(Mg1/3 Nb2/3 )0.7 Ti0.3 O3 (PMNT) thin film was prepared using spin coating and a PbO cover coat technique. The amount of lead excess in the precursor solution had significant effects on the phase development and microstructure of the PMNT film. The PbO cover coat proved to be effective on suppressing the formation of pyrochlore phases. PMNT thin films with a pure perovskite structure were obtained by adding 30 mol% excess lead in the precursor solution and coating the PbO layer on the top of the film. The remnant polarization ( P r ), the dielectric constant (ɛr ), and the dissipation factor (tan δ) of these thin films, which had a thickness of 150 nm, were determined to be 9 μC/cm2 , 1370, and 0.031, respectively. 相似文献
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以癸二酸和乙二醇单丁醚为原料,用HZSM-5分子筛催化合成环保耐寒性增塑剂癸二酸二丁氧基乙酯。考察了催化剂的硅铝比、催化剂用量、带水剂用量、原料配比、反应时间对酯化率的影响。最佳工艺条件为:醇酸摩尔比为2.5∶1,催化剂用量为酸质量的5%,带水剂用量为酸质量的15%,反应时间为3.5 h,反应温度为170~200 ℃,该工艺条件下酯化率可达91.91%。经过5次使用后,酯化率仍在90%以上。同时建立了该酯化合成的表观动力学模型,得到反应速率方程为: 。 相似文献
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肾性贫血药物罗沙司他是在中国本土孵化、率先在中国获批的新药。利用溶液结晶法制备了罗沙司他-烟酰胺共晶(RDXT-N)、罗沙司他-肉桂酰胺共晶(RDXT-C)、罗沙司他-苯甲酰胺共晶(RDXT-B)以及罗沙司他-脯氨酸共晶(RDXT-P)四种共晶,并通过X射线粉末衍射(XRD)、差示扫描量热仪(DSC)、热重分析(TGA)、傅里叶变换红外光谱仪(FTIR)和核磁共振氢谱分析法(1H NMR)来表征四种共晶。对罗沙司他四个共晶的固有溶出速率、溶解度和稳定性等性质进行了研究。固有溶出速率实验表明,在pH 4.5缓冲介质中这四个共晶的溶出速率均快于罗沙司他晶型A,其中罗沙司他-肉桂酰胺共晶的溶出速率最快,接近罗沙司他晶型A的10倍。平衡溶解度实验表明,在纯水中37℃条件下溶解度最大是罗沙司他-脯氨酸共晶,是晶型A的5.3倍。影响因素稳定性实验证明,罗沙司他-肉桂酰胺共晶和罗沙司他-烟酰胺共晶有着良好的湿热稳定性和光稳定性。因此,这些罗沙司他共晶可以为新剂型设计提供选择方案。 相似文献
40.
The fiber spinning methods determine the formation of the physical structures of polyacrylonitrile (PAN) fibers which further affect stabilization reactions and the mechanical performances of the resultant carbon fibers. In this study, PAN fibers were prepared by both dry-jet gel spinning (g-PAN) and dry-jet wet spinning (w-PAN), and their stabilization behaviors were compared. While the stabilized w-PAN fibers show sheath-core structures, the stabilized g-PAN fibers exhibit relatively uniform stabilized structures along the radial direction. Additionally, the stabilization reactions of g-PAN fibers occur faster than that of w-PAN fibers, and the cyclization, oxidation, and crosslinking reaction activation energies of g-PAN fibers are lower than that of w-PAN fibers, respectively. Moreover, the carbon yield of g-PAN is higher than that of w-PAN fibers. We believe that above changes are possibly ascribed to the formation of different PAN sheath structures and oriented chain structures during dry-jet wet spinning and dry-jet gel spinning. It is concluded that gel spinning could significantly reduce the sheath-core difference of PAN fibers and the stabilized fibers as compared with wet spinning, which leads to a faster stabilization and more uniform stabilized structures. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48671. 相似文献