全文获取类型
收费全文 | 55880篇 |
免费 | 5369篇 |
国内免费 | 2729篇 |
专业分类
电工技术 | 3622篇 |
技术理论 | 4篇 |
综合类 | 3713篇 |
化学工业 | 8991篇 |
金属工艺 | 3342篇 |
机械仪表 | 3824篇 |
建筑科学 | 4242篇 |
矿业工程 | 1779篇 |
能源动力 | 1726篇 |
轻工业 | 4009篇 |
水利工程 | 1202篇 |
石油天然气 | 2987篇 |
武器工业 | 559篇 |
无线电 | 6258篇 |
一般工业技术 | 6623篇 |
冶金工业 | 2689篇 |
原子能技术 | 827篇 |
自动化技术 | 7581篇 |
出版年
2024年 | 279篇 |
2023年 | 1002篇 |
2022年 | 1765篇 |
2021年 | 2438篇 |
2020年 | 1855篇 |
2019年 | 1612篇 |
2018年 | 1807篇 |
2017年 | 1931篇 |
2016年 | 1791篇 |
2015年 | 2394篇 |
2014年 | 2980篇 |
2013年 | 3467篇 |
2012年 | 4001篇 |
2011年 | 4195篇 |
2010年 | 3661篇 |
2009年 | 3511篇 |
2008年 | 3322篇 |
2007年 | 3083篇 |
2006年 | 2927篇 |
2005年 | 2450篇 |
2004年 | 1846篇 |
2003年 | 1678篇 |
2002年 | 1736篇 |
2001年 | 1527篇 |
2000年 | 1227篇 |
1999年 | 1194篇 |
1998年 | 816篇 |
1997年 | 651篇 |
1996年 | 607篇 |
1995年 | 532篇 |
1994年 | 373篇 |
1993年 | 317篇 |
1992年 | 248篇 |
1991年 | 175篇 |
1990年 | 140篇 |
1989年 | 89篇 |
1988年 | 102篇 |
1987年 | 50篇 |
1986年 | 58篇 |
1985年 | 28篇 |
1984年 | 24篇 |
1983年 | 16篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1977年 | 7篇 |
1975年 | 5篇 |
1970年 | 6篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
为改善复合泡沫塑料的介电性能,采用金属氧化物粒子填充改性双马来酰亚胺空芯玻璃微球复合泡沫塑料得到了高介电常数、低介质损耗因数、低密度、力学性能良好的电介质材料。 相似文献
33.
PdOx/MnO2 has been examined as a catalyst for CO oxidation using a conventional flow reactor at reaction temperatures between 50 and 150°C. In the reaction conditions of GHSV (gashourlyspacevelocity) of 1.22 × 105/h and CO concentration of 2000 ppm, PdOx/MnO2 showed higher catalytic activity compared with PdOx/Mn2O3, which had been previously reported as an effective catalyst due to the cooperative action of Pd and Mn2O3 for this reaction. The reason for higher activity of PdOx/MnO2 than PdOx/Mn2O3 has been investigated using TPR (temperatureprogrammed reduction) and XPS studies. TPR showed that PdOx/MnO2 could be reduced by CO at much lower temperature than PdOx/Mn2O3. During the experiment of reduction and oxidation, XPS showed that the valence of Mn in the PdOx/MnO2 was between 4+ and 3+, which is higher than that of Mn in the PdOx/Mn2O3 catalyst of which the valence has been reported to be between 3+ and 2+. It is known that in this catalyst system the support supplies oxygen onto Pd, where the oxidation occurs with adsorbed CO, and the ability of the support to provide oxygen improves the performance of the catalyst. Therefore, it was concluded that the readiness of MnO2 to be reduced with maintaining a higher oxidation state showed higher CO oxidation activity than Mn2O3 as support for PdOx. 相似文献
34.
CeO2 particles confined within the pores of an SBA-15 mesoporous silica host were prepared by incipient wetness impregnation (IMP)
and deposition precipitation (DP) methods. The materials were characterized by XRD, N2-adsorption and temperature programmed reduction (TPR) to evaluate the structure, texture, and redox properties. The preparation
procedure had significant impact on the assembling mode of CeO2 inside the SBA-15 mesopores. A high dispersion of CeO2 particles was achieved via DP, whereas the dispersion of CeO2 prepared by IMP was found to be inhomogeneous and CeO2 partially blocked the pores. The CO conversion in the water-gas-shift reaction was enhanced over 1 wt% Pt supported on CeO2-modified SBA-15 obtained by DP. 相似文献
35.
介绍了用火焰原子吸收法测定工业硅粉中微量铜的具体方法和过程,同时也给出了最佳实验条件。实验中采用新的样品处理方法,得到了令人满意的结果。其中样品回收率为99.8%—104.0%,相对标准偏差为0.31%—0.38%。本方法在实际应用过程中,简单、快速、 相似文献
36.
37.
AADL 测试模型的构造研究 总被引:1,自引:0,他引:1
目前,结构分析和设计语言AADL在任务关键嵌入式系统领域有着良好的应用.为了保障任务关键软件的质量,文章提出基于AADL测试模型对AADL设计模型进行测试,以发现设计模型中存在的错误.研究给出了体现系统拓扑结构的AADL测试模型的形式定义及由AADL构造该测试模型的算法,基于该测试模型可以对AADL设计模型中构件交互的输入、输出端口序列和连接的正确性进行测试,并以飞行控制系统的AADL设计模型为例,阐释了研究成果. 相似文献
38.
Based on the dual-phase-lagging(DPL)heat conduction model,the Cattaneo-Vernotte(CV)model and the improved CV model we investigate the one-dimensional heat conduction in gold films with nano-scale thickness exposed to an ultra-fast laser heating.The influence of system parameters on the temperature field is explored.We find that for all the non-Fourier heat conduction models considered in this work,a larger Knudsen number normally leads to a higher temperature.For the DPL model,the large ratio of the phase lag of temperature gradient to the phase lag of heat flux reduces the maximum temperature and shortens the time for the system to reach its steady state.The CV model and the improved CV model lead to the similar thermal wave behavior of the temperature field,but the thermal wave speeds for these two models are different,especially for large Knudsen numbers.When the phase lag of temperature gradient is smaller,the difference between the DPL model and the improved CV model is not significant,but for the large phase lag of temperature gradient the difference becomes quite significant,especially for the large Knudsen number.In addition,the effect of the surface accommodation coefficient,which is a parameter in the slip boundary condition,on the temperature field of the gold film heated by ultra-fast laser pulses is investigated based on the DPL model. 相似文献
39.
本文提出了双回转送进二辊冷轧管机凸轮理论轮廓曲线的新设计方法 ,其轮廓曲线加速度与跃度呈梯形 ,且跃度边界连续 ,给出了针对双回转送进二辊冷轧管机的两个过渡段具有等加速度和跃度的设计准则 相似文献
40.