全文获取类型
收费全文 | 19616篇 |
免费 | 1942篇 |
国内免费 | 1010篇 |
专业分类
电工技术 | 1355篇 |
综合类 | 1290篇 |
化学工业 | 2850篇 |
金属工艺 | 1332篇 |
机械仪表 | 1311篇 |
建筑科学 | 1585篇 |
矿业工程 | 703篇 |
能源动力 | 501篇 |
轻工业 | 1529篇 |
水利工程 | 379篇 |
石油天然气 | 1304篇 |
武器工业 | 174篇 |
无线电 | 2316篇 |
一般工业技术 | 2268篇 |
冶金工业 | 967篇 |
原子能技术 | 170篇 |
自动化技术 | 2534篇 |
出版年
2024年 | 127篇 |
2023年 | 378篇 |
2022年 | 656篇 |
2021年 | 897篇 |
2020年 | 688篇 |
2019年 | 559篇 |
2018年 | 582篇 |
2017年 | 723篇 |
2016年 | 567篇 |
2015年 | 818篇 |
2014年 | 1057篇 |
2013年 | 1196篇 |
2012年 | 1304篇 |
2011年 | 1330篇 |
2010年 | 1218篇 |
2009年 | 1134篇 |
2008年 | 1089篇 |
2007年 | 1056篇 |
2006年 | 1129篇 |
2005年 | 1058篇 |
2004年 | 650篇 |
2003年 | 588篇 |
2002年 | 561篇 |
2001年 | 441篇 |
2000年 | 421篇 |
1999年 | 422篇 |
1998年 | 360篇 |
1997年 | 320篇 |
1996年 | 277篇 |
1995年 | 236篇 |
1994年 | 187篇 |
1993年 | 122篇 |
1992年 | 98篇 |
1991年 | 75篇 |
1990年 | 63篇 |
1989年 | 54篇 |
1988年 | 42篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1959年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
铝合金电火花线切割加工工艺研究 总被引:2,自引:0,他引:2
通过对铝合金高速走丝电火花线切割加工的工艺设计,探讨了其加工的工艺特点,分析了不同的进给速度、工作液及电参数对加工工艺指标的影响,并提出了改善铝合金高速走丝线切割加工工艺性能的措施。 相似文献
65.
66.
The iron rhenate was compounded by chemical method, which may be generated during wear process of Fe-Re alloys at elevated
temperature. The friction coefficient of iron rhenate has been determined by a pin-on-disc device. The results show that iron
rhenate plays role of lubricating at RT-600 °C. The lubricating behavior is related to the matching pairs. The hardness of
the materials of matching pairs, compatibility of iron rhenate with materials of matching pairs and surface roughness of disc
affect the lubricating behavior of iron rhenate mostly. The principle of matching pairs is proposed.
Project supported by the National Natural Science Foundation of China
Synopsis of the first author Xiong Dangsheng. associated professor, born in 1960. Current research fields include high-temperature self-lubricating alloys
and tribological properties of material. 相似文献
67.
It is stated in the above-mentioned comment that the main result of the paper Xiong, Zhang, et al. [(2006). Performance evaluation of UKF-based nonlinear filtering. Automatica 42(2), 261-270] can be extended to a class of filters, such as the extended Kalman filter (EKF). As we show here, this belief can be justified in a rigorous way, even for the nonlinear stochastic system with a nonlinear measurement equation. 相似文献
68.
Zixiang Xiong Ramchandran K. Herley C. Orchard M.T. 《Signal Processing, IEEE Transactions on》1997,45(2):333-345
Addresses the problem of finding the best time-varying filter bank tree-structured representation for a signal. The tree is allowed to vary at regular intervals, and the spacing of these changes can be arbitrarily short. The question of how to choose tree-structured representations of signals based on filter banks is considered. Wavelets and their adaptive version, known as wavelet packets, represent one approach that is popular. Wavelet packets are subband trees where the tree is chosen to match the characteristics of the signal. Variations where the tree varies over time have been proposed as the double tree and the time-frequency tree algorithms. Time-variation adds a further level of adaptivity. In all of the approaches proposed so far, the tree must be either fixed for the whole duration of the signal or fixed for its dyadic subintervals. The solution that we propose, as it allows more flexible variation, is an advance on the wavelet packet algorithm, the double tree algorithm, and the recently proposed time-frequency tree algorithm. Our solution is based on casting it in a dynamic programming (DP) setting. Focusing on compression applications, we use a Lagrangian cost of distortion +λ×rate as the objective function and explain our algorithm in detail, pointing out its relation to existing approaches to the problem. We demonstrate that the new algorithm indeed searches a larger library of representations than previously possible and that overcoming the constraint of dyadic time segmentations gives a significant improvement in practice 相似文献
69.
双极性步进电机细分驱动器的设计与实现 总被引:1,自引:0,他引:1
论述了一种双极性步进电动机驱动器的工作原理,该驱动器能较好地改善步进电动机的运行性能,具有实用性强,结构简单,成本低的优点。针对实际调试中出现的问题进行分析后,提出了对策;最后给出了试验结果。 相似文献
70.
激光焊接超细基胎体金刚石薄壁钻 总被引:6,自引:1,他引:5
采用激光焊接超细预合金粉胎体,开发了新的薄壁钻产品,通过对与现有的产品工艺、性能测试以及实际使用分析对比,结果表明:激光焊接与普通钎焊相比结合强度提高2-3倍,克服了胎体脱落问题,胎体耐磨性提高了50%-120%,其中轴向磨损速率提高1.2倍;钻削速度提高30.4%,工矿适应性增加,使用寿命提高25%-108%。 相似文献