全文获取类型
收费全文 | 1157篇 |
免费 | 137篇 |
国内免费 | 53篇 |
专业分类
电工技术 | 82篇 |
综合类 | 66篇 |
化学工业 | 186篇 |
金属工艺 | 57篇 |
机械仪表 | 78篇 |
建筑科学 | 158篇 |
矿业工程 | 29篇 |
能源动力 | 24篇 |
轻工业 | 53篇 |
水利工程 | 41篇 |
石油天然气 | 57篇 |
武器工业 | 20篇 |
无线电 | 164篇 |
一般工业技术 | 126篇 |
冶金工业 | 22篇 |
原子能技术 | 12篇 |
自动化技术 | 172篇 |
出版年
2024年 | 3篇 |
2023年 | 29篇 |
2022年 | 54篇 |
2021年 | 60篇 |
2020年 | 50篇 |
2019年 | 28篇 |
2018年 | 45篇 |
2017年 | 41篇 |
2016年 | 37篇 |
2015年 | 47篇 |
2014年 | 59篇 |
2013年 | 56篇 |
2012年 | 81篇 |
2011年 | 80篇 |
2010年 | 85篇 |
2009年 | 74篇 |
2008年 | 73篇 |
2007年 | 64篇 |
2006年 | 64篇 |
2005年 | 54篇 |
2004年 | 36篇 |
2003年 | 33篇 |
2002年 | 22篇 |
2001年 | 19篇 |
2000年 | 38篇 |
1999年 | 29篇 |
1998年 | 14篇 |
1997年 | 16篇 |
1996年 | 8篇 |
1995年 | 13篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1990年 | 7篇 |
1989年 | 1篇 |
1979年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有1347条查询结果,搜索用时 0 毫秒
941.
942.
利用自主设计的介质阻挡-电晕放电耦合装置进行脱除NO的实验研究,在N2/O2/NO体系中,考察加入不同钠添加剂(Na2CO3、NaOH、CH3COONa)对尿素脱除NO的影响,同时探讨其在脱除NO过程中的作用机理。结果表明:在研究范围内,仅添加尿素时,NO脱除率随尿素含量的增加而增大,当输入电流为0.83A,尿素分解产生氨气的体积分数为0.3%时,NO脱除率为64.23%,此时体系中有CO生成且随尿素含量的增加而增加;少量钠添加剂的加入可显著提高NO脱除率,且脱除率随钠添加剂含量的增加而增大,此时CO生成量得到有效抑制。在加入量相同的条件下,各种钠添加剂对尿素脱除NO均有促进作用,促进作用大小依次为:NaOH > Na2CO3 > CH3COONa,当加入氢氧化钠与尿素质量比为10∶10时,输入电流仅为0.83A时,脱除率可达90.71%;电流为5A,脱除率达95.71%,此时体系中几乎无CO生成。 相似文献
943.
LUO Cheng YANG Weishun XIE Wenjun LI Changchun CHAI Zhen ZHU Xiaorong LIU Jianlong JIAO Jiqiang WAN Yapeng LIN Xiaojian MA Xiangli ZHANG Xiping MENG Jun CHEN Shuping 《原子能科学技术》1959,54(11):2245-2251
Heavy Ion Medical Machine (HIMM), developed by the Institute of Modern Physics, Chinese Academy of Sciences, is the first medical heavy ion accelerator with independent intellectual property rights in China. Because the RAMPING mode was used for high frequency pulse dipole magnets of HIMM and the rising rate of magnetic field is 1.6 T/s, the vacuum chamber installed in the high frequency pulsed magnet is a thin-wall stainless vacuum chamber with reinforcing ribs to reduce the influence of eddy current on the ion beam stability. However, the gap size of magnet occupied by thin-wall stainless vacuum chamber with reinforcing ribs is too large, and it not only causes the high cost of magnets, but also greatly improves the maintenance cost. Based on these reasons, a new thin-wall vacuum chamber (0.3 mm) with ceramic lining was put forward and the prototype was designed and manufactured. The test results show that the obtained pressure of the prototype is in the order magnitude of 10-10 Pa, and the magnet gap can be effectively reduced. And it is the development direction of thin-wall vacuum chamber of accelerator in the future. 相似文献
944.
945.
Qinlun Xu Guang-Yao Meng Dong Yu Xiaojian Pan Xiao Wei Lu Zhiqiang Mao Yi Dong Zhaojia Chen Jiang Lu Cheng-gao Fan Guien Zhou Yuheng Zhang 《Journal of Superconductivity and Novel Magnetism》1990,3(2):183-187
A nearly pure 2223 phase of the ceramic superconductor Bi1.8Pb0.3Sb0.1Sr2Ca2Cu3O10?δ was obtained by solid-state reaction in air. The samples showed a semiconducting behavior when the temperature was higher than 140 K. The electrical resistance began to drop at 140 K and went to zero at 92 K. Their a.c. magnetic susceptibility showed two transitions at 130 and 89 K, but the 110 K transition was absent. These transitions were stable during cycling for three times from 77 K to room temperature. X-ray diffraction revealed that there was no 2212 or 2201 phase in these samples but only a small amount of monoclinic phase before and after cycling from 77 K to room temperature. SEM images showed that the grains of the monoclinic phase segregated on the surface of the sample and at the grain boundaries inside the sample, which is the reason for the sample's poor superconductivity and the decrease in zero resistance. Evidence from TEM and SEM equipped with a wavelength dispersive meter indicated distortion of the 2223 phase. These distorted 2223 crystals may be responsible for the 130 K superconductivity. 相似文献
946.
为MARPOSSE_3量仪配置数据管理系统的软件用TurboC编制,并以追求良好的用户界面及满足低成本软件配置的要求原则.本文介绍软件设计中的主要技术措施,包括:(1)西文DOS下汉字输出的实现;(2)“光条”技术的实现;(3)高速汉字下拉式菜单的实现;(4)通过过程控制函数化大程序为若干小程序;(5)克服286低挡配置对软件设计产生的影响. 相似文献
947.
948.
Qingping Sun Zhijun Zhao Weizhe Chen Xinglin Qing Xiaojian Xu Fuloon Dai 《Journal of the American Ceramic Society》1994,77(5):1352-1356
Stress-induced martensitic transformation plastic zones in ceria-stabilized tetragonal zirconia polycrystalline ceramics (Ce-TZP), under loading conditions of uniaxial tension, compression, and three-point bending, are studied by experiments. The transformed monoclinic phase volume fraction distribution and the corresponding plastic strain distribution and the surface morphology (surface uplift) are measured by means of moire interferometry, Raman microprobe spectroscopy, and the surface measurement system. The experimental results from the above three kinds of specimens and methods consistently show that the stress-induced transformation at room temperature of the above specimen is not uniform within the transformation zone and that the plastic deformation is concentrated in some narrow band; i.e., macroscopic plastic flow localization proceeds during the initial stage of plastic deformation. Flow localization phenomena are all observed in uniaxial tension, compression, and three-point bending specimens. Some implications of the flow localization to the constitutive modeling and toughening of transforming thermoelastic polycrystalline ceramics are explored. 相似文献
949.
本文介绍了七种测定P-S-N曲线的方法。并且用五种材料的实验数据对上述测定方法作了分析比较。在比较了几种方法的优缺点的基础上,提出了选择试验方法的建议和结论。 相似文献
950.
35kV电缆接地故障处理及分析 总被引:3,自引:0,他引:3
针对2007年4月三峡施工电网一回35kV电缆线路出现的3次单相接地击穿故障进行检查分析,找出存在的问题,并提出相应的处理措施. 相似文献