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91.
Electrochemical ferrate generation for waste water treatment using cast irons with high silicon contents 总被引:5,自引:0,他引:5
This paper deals with the electrochemical preparation of ferrate in 15 M NaOH media, with a view to treatment of waste waters. Grey cast irons with high silicon contents were shown to allow current yields in the range 20–40% depending on the applied current density, up to 34 mA cm–2. Ferrate solutions with contents up to 0.08 M could be produced in a divided cell of simple design, and provided with flat or packed-bed electrodes. Deactivation of the anode surface was shown to be of moderate significance for hour-long runs. The ferrate produced was tested for treatment of industrial liquid wastes: coagulation efficiency of the suspended matter was comparable with that of an electrocoagulation process with sacrificial Al anodes. The potential of waste water treatment by addition of ferrate is discussed. 相似文献
92.
In previous work, we developed a highly active bimetallic platinum–ruthenium catalyst supported on a very high surface area activated carbon substrate. In fixed bed reactors, this catalyst proved capable of the continuous long-term deep oxidation of a variety of aqueous organic contaminants associated with spacecraft wastewater streams at 121 °C. This work was extended to the mineralization of more typical environmental contaminants, including halocarbons and aromatics. The primary weakness of this catalyst was the tendency toward relatively high rates of chemical decomposition. To overcome this limitation, methods were developed for the production of a silicon carbide coating over the surface of the activated carbon, yielding a reasonable trade-off between increasing resilience and decreasing surface area. Here we report the catalytic decomposition of dissolved organic contaminants at 130 °C using this silicon carbide/activated carbon supported bimetallic catalyst. 相似文献
93.
94.
Ye Cai ré Zimmermann Arndt Bauer Fritz Aldinger 《Journal of the American Ceramic Society》2003,86(9):1598-1600
Precursor-derived Si-C-N ceramics after creep testing in air were characterized using X-ray diffractometry (XRD) and transmission electron microscopy (TEM). XRD analysis showed that the crept Si-C-N ceramics were covered by an α-cristobalite layer. TEM observations revealed that the precipitated nanocrystallites in the crept Si-C-N ceramics were β-SiC. Between α-cristobalite and crept Si-C-N ceramic, there was an intermediate zone in which Si2 N2 O nanocrystallites were distributed homogeneously. Moreover, Si2 N2 O nanocrystallites were often found covering the surface of nanosized gas channels in the crept Si-C-N ceramics, where no α-cristobalite phase was detected. Based on these observations, a two-step oxidation mechanism of Si-C-N ceramics during creep testing in air was proposed. 相似文献
95.
96.
金属铝诱导法低温制备多晶硅薄膜 总被引:4,自引:0,他引:4
以氢气稀释的硅烷(SiH4)和硼烷(B2H6)为气源,利用等离子体增强化学气相沉积法(PECVD)制备出p型a-Si薄膜.采用铝诱导晶化技术对不同厚度的铝膜对a-Si薄膜晶化的影响进行了研究.实验中发现,铝膜溅射为10 s的非晶硅薄膜样品在450℃下退火10 min后,p型a-Si结构仍为非晶态,铝膜溅射为20 s的非晶硅薄膜在450℃下退火20 min后,p型a-Si薄膜开始晶化为polySi薄膜,并且铝膜厚度越厚,则a-Si薄膜晶化程度越强. 相似文献
97.
用放电等离子烧结(spark plasma sintering,SPS)技术,以质量分数(下同)为9%氮化铝(A1N),3%氧化镁(MgO)为烧结助剂,在1850℃烧结5min,成功制备了半透明氮化硅(Si3N4)陶瓷.半透明Si3N4陶瓷在中红外波段表现出良好的透过率,最大透过率为66.4%.SPS的快速致密化过程保证了烧结体具有良好的晶体结构,有利于提高透过率.SPS快速的烧结过程和A1N和MgO的加入能够有效抑制烧结过程中Si3N4陶瓷由α相向β相的转变,是制备光学性能良好的Si3N4陶瓷的关键.报道了半透明Si3N4陶瓷的其他性能.光学性能与其他性能的结合,势必大大拓宽Si3N4陶瓷的应用领域. 相似文献
98.
Composites consisting of a fine-grained, polycrystalline zinc oxide matrix and <10 vol% coarse, rigid silicon carbide inclusions were prepared by the same mixing procedure and then compacted to produce samples with matrix densities of 0.45 and 0.68 of the theoretical. The samples were sintered under identical temperature profiles in separate experiments that employed either a constant rate of heating of 4°C/min or near isothermal heating at 735°C. The ratio of the densification rate of the composite matrix to the densification rate of the unreinforced zinc oxide was found to be independent of the initial matrix density. This ratio increased significantly with temperature in the constant-heating-rate experiments but was relatively constant in the isothermal experiments. The results indicate that microstructural coarsening may be an important mechanism for explaining the reduced sinterability of polycrystalline matrix composites. 相似文献
99.
Arun K. Bhattacharya John J. Petrovic 《Journal of the American Ceramic Society》1991,74(10):2700-2703
The indentation technique has been used to evaluate the hardness and fracture toughness of SiC-reinforced MoSi2 composites made by hot-pressing. It is seen that the toughness increases with increasing indentation crack length (under increasing load) and a probable mechanism responsible for this behavior is described. It is also observed that there is an optimum volume fraction of SiC particles for which the maximum fracture toughness of the composite can be achieved. 相似文献
100.
压痕残余应力对氮化硅基复合材料阻力曲线行为的影响 总被引:3,自引:1,他引:3
通过压痕小裂纹直接量测法获得了TiC,TiN/Si3N4复合材料的阻力曲线,采用更具合理性的指数经验公式拟合处理实验数据,初步探讨了K∞,K^*R,ΔC,等参数的物理意义。对压痕残余应力消除前 实验结果进行比较,发现压痕残余应力的消除,提高了材料的极限断裂韧性值K^*R,却大大减少了裂纹稳态生长的容限,使得材料的脆性行为更为突出。 相似文献