全文获取类型
收费全文 | 181798篇 |
免费 | 17053篇 |
国内免费 | 9788篇 |
专业分类
电工技术 | 14253篇 |
技术理论 | 8篇 |
综合类 | 18642篇 |
化学工业 | 17636篇 |
金属工艺 | 7961篇 |
机械仪表 | 17140篇 |
建筑科学 | 20618篇 |
矿业工程 | 7051篇 |
能源动力 | 7849篇 |
轻工业 | 13668篇 |
水利工程 | 7601篇 |
石油天然气 | 8464篇 |
武器工业 | 2221篇 |
无线电 | 10926篇 |
一般工业技术 | 17588篇 |
冶金工业 | 7302篇 |
原子能技术 | 2544篇 |
自动化技术 | 27167篇 |
出版年
2024年 | 751篇 |
2023年 | 2210篇 |
2022年 | 4516篇 |
2021年 | 5294篇 |
2020年 | 5539篇 |
2019年 | 4644篇 |
2018年 | 4572篇 |
2017年 | 5640篇 |
2016年 | 6820篇 |
2015年 | 7151篇 |
2014年 | 11694篇 |
2013年 | 11616篇 |
2012年 | 13538篇 |
2011年 | 14868篇 |
2010年 | 10752篇 |
2009年 | 10882篇 |
2008年 | 10239篇 |
2007年 | 12328篇 |
2006年 | 10700篇 |
2005年 | 9012篇 |
2004年 | 7584篇 |
2003年 | 6474篇 |
2002年 | 5238篇 |
2001年 | 4300篇 |
2000年 | 3715篇 |
1999年 | 3054篇 |
1998年 | 2614篇 |
1997年 | 2200篇 |
1996年 | 1801篇 |
1995年 | 1482篇 |
1994年 | 1333篇 |
1993年 | 992篇 |
1992年 | 904篇 |
1991年 | 670篇 |
1990年 | 559篇 |
1989年 | 486篇 |
1988年 | 401篇 |
1987年 | 274篇 |
1986年 | 236篇 |
1985年 | 215篇 |
1984年 | 257篇 |
1983年 | 239篇 |
1982年 | 198篇 |
1981年 | 96篇 |
1980年 | 95篇 |
1979年 | 66篇 |
1978年 | 53篇 |
1977年 | 46篇 |
1976年 | 43篇 |
1959年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
J. B. Quinn G. E. Schumacher L. W. Schultheis 《Journal of Failure Analysis and Prevention》2004,4(1):41-46
Several days after heart surgery, a patient discovered his upper right canine tooth had broken at the root. Such tooth damage,
recognized post-operatively, is usually assumed to be caused by blunt mechanical force from an instrument used by the anesthesiologist
during placement of a breathing tube at the start of surgery.
In this case, the patient had saved the crown portion of the broken tooth, and it was possible to examine the root fracture
characteristics. The curvature and direction of the crack path and natural tooth situation suggested that failure could be
described through a cantilever beam model. This was confirmed when a whole extracted sample tooth was embedded and broken
by a measured force in a manner consistent with the model. The resulting fracture surface matched that of the patient’s broken
canine tooth. However, the high load and force direction necessary to fracture the root was inconsistent with forces applied
during the anesthesia procedure. The failure analysis and further investigation indicated tooth clenching on the breathing
tube during recovery was the likely cause of fracture.
This paper presents an alternate explanation for intubation-related dental injury, demonstrates the practicality of fractographic
analysis of biological materials, and introduces a methodology for simulating in vitro tooth settings for mechanical testing. 相似文献
52.
基于直升机目标旋转部件的调制模型,本文针对防空雷达提出了分析直升机信号特征的一种新方法——WVD法,并对直升机目标旋转部件调制回波信号在不同噪声情况下加以仿真分析,结果表明:用WVD分析雷达回波中直升机信号特征是一种非常有效的方法。 相似文献
53.
硅微机械梳齿静电谐振器的建模与分析 总被引:5,自引:2,他引:3
基于参数化的计算机辅助设计(CAD)软件,对硅微机械梳齿静电谐振器进行了实体建模,以有限元分析软件为工具,进行了谐振器的模态分析,静态分析和谐响应分析,初步揭示了谐振器的静、动态特性,有助于改善设计效率和质量,展示了计算机辅助工程(CAE)技术在微机电系统(MEMS)研究中的重要作用。 相似文献
54.
55.
56.
一种基于三次样条函数求离子浓度的自动算法 总被引:1,自引:0,他引:1
本文提出了一种用三次样条函数模拟双次标准加入法测量方程,直接求解离子浓度的自动算法。比较了三咱不同边界条件下用要池数计算离子浓度的结果。造出节点区间两极端点的二阶导数为零时的三次样条函数为最佳模拟函数。并讨论了该方法在实际分析中误差的来源及消除办法。经对一系列文献数据的验算对比,表明本法完全可代替传统的迭代法和查图法,且能方便地设置在智能化的电位分析系统中。 相似文献
57.
心电地图仪中工频干扰的一种滤除方法 总被引:1,自引:0,他引:1
在心电地图仪中记录到的体表心电信号往往由于电磁的影响而引进工频干扰.基于体表心电信号中工频干扰的特点,作者提出了一种滤除工频干扰的方法,即就单独—胸导联信号通过提高频谱的分辨率来估计工频干扰的频率;基于最小均方误差准则来估计各导联信号中工频干扰的幅度和相位。文中还给出了该算法的流程图和滤波性能分析。模拟结果表明了该算法的有效性。应用该算法对心电地图仪中的工频干扰进行对消,取得了满意的结果。 相似文献
58.
Takeshi Nakajo 《Quality and Reliability Engineering International》1993,9(2):111-119
Work system improvements are implemented in various manufacturing processes to prevent problems caused by human errors. However, they are almost always applied to problems which have already occurred. This paper examines a method of identifying latent human errors existing within the work systems beforehand. A procedure for applying failure mode and effect analysis to this identification problem was defined based on over 1000 empirical errors: a work system decomposition criterion and fundamental error modes for listing latent human errors, and then applied to three practical manufacturing processes in order to evaluate its effectiveness. 相似文献
59.
60.
A mixed mode digital/analog special purpose VLSI hardware implementation of an associative memory with neural architecture is presented. The memory concept is based on a matrix architecture with binary storage elements holding the connection weights. To enhance the processing speed analog circuit techniques are applied to implement the algorithm for the association. To keep the memory density as high as possible two design strategies are considered. First, the number of transistors per storage element is kept to a minimum. In this paper a circuit technique that uses a single 6-transistor cell for weight storage and analog signal processing is proposed. Second, the device precision has been chosen to a moderate level to save area as much as possible. Since device mismatch limits the performance of analog circuits, the impact of device precision on the circuit performance is explicitly discussed. It is shown that the device precision limits the number of rows activated in parallel. Since the input vector as well as the output vector are considered to be sparsely coded it is concluded, that even for large matrices the proposed circuit technique is appropriate and ultra large scale integration with a large number of connection weights is feasible. 相似文献