全文获取类型
收费全文 | 5266篇 |
免费 | 565篇 |
国内免费 | 339篇 |
专业分类
电工技术 | 311篇 |
综合类 | 420篇 |
化学工业 | 1013篇 |
金属工艺 | 522篇 |
机械仪表 | 417篇 |
建筑科学 | 286篇 |
矿业工程 | 187篇 |
能源动力 | 225篇 |
轻工业 | 154篇 |
水利工程 | 91篇 |
石油天然气 | 83篇 |
武器工业 | 401篇 |
无线电 | 434篇 |
一般工业技术 | 1011篇 |
冶金工业 | 201篇 |
原子能技术 | 89篇 |
自动化技术 | 325篇 |
出版年
2024年 | 19篇 |
2023年 | 96篇 |
2022年 | 185篇 |
2021年 | 194篇 |
2020年 | 156篇 |
2019年 | 129篇 |
2018年 | 159篇 |
2017年 | 193篇 |
2016年 | 191篇 |
2015年 | 185篇 |
2014年 | 300篇 |
2013年 | 323篇 |
2012年 | 328篇 |
2011年 | 390篇 |
2010年 | 267篇 |
2009年 | 263篇 |
2008年 | 276篇 |
2007年 | 356篇 |
2006年 | 289篇 |
2005年 | 257篇 |
2004年 | 257篇 |
2003年 | 212篇 |
2002年 | 181篇 |
2001年 | 178篇 |
2000年 | 135篇 |
1999年 | 99篇 |
1998年 | 82篇 |
1997年 | 80篇 |
1996年 | 76篇 |
1995年 | 61篇 |
1994年 | 53篇 |
1993年 | 40篇 |
1992年 | 28篇 |
1991年 | 24篇 |
1990年 | 35篇 |
1989年 | 15篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1984年 | 3篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1974年 | 2篇 |
1964年 | 4篇 |
1963年 | 3篇 |
1959年 | 2篇 |
1958年 | 2篇 |
1957年 | 3篇 |
1956年 | 3篇 |
1955年 | 2篇 |
1954年 | 2篇 |
排序方式: 共有6170条查询结果,搜索用时 15 毫秒
151.
Yinjun Wang Xuguang Wang Shilong Yah 《北京科技大学学报(英文版)》2006,13(2):102-107
The desensitization degree of emulsion explosives (EE) was calculated with the peak pressure of explosion shock waves tested in water. To an explosive, the less the desensitization degree, the better the compression resistance, so the compression resistance of an explosive can be compared and analyzed quantificationally with the desensitization degree. The influence of an emulsifier on the pressure desensitization of EE was studied, including the content and category of emulsifiers. Three kinds of emulsifiers (Span-80, compound emulsifier, and T-152) were used in the tests. The experimental results show that both the content and category of emulsifiers make a great effect on the pressure desensitization of EE. The desensitization degree of EE reduces with the emulsifier content being increased, but there is an optimal content of an emulsifier for the compression resistance of EE. While the content of Span-80 reaches 4wt%, the desensitization degree of EE becomes a minimal value, and augments somewhat if the emulsifier content is increased more. That is to say, the compression resistance of EE becomes the highest while the content of Span-80 is 4wt%, and the compression resistance will decline if the content of Span-80 is increased more. The compression resistance of the explosive emulsified by compound emulsifier is the highest among all the explosives, when the content of the whole components and manufacturing engineering are kept invariable. 相似文献
152.
Aiming at two intense shock events on October 28 and 29, 2003, this paper presents a two-step method, which combines synoptic analysis of space weather ——“observing” and quantitative prediction ——“palpating”, and then uses it to test predictions. In the first step of “observing”, on the basis of observations of the solar source surface magnetic field, interplanetary scintillation (IPS) and ACE spacecraft, we find that the propagation of the shocks is asymmetric relative to the normal direction of their solar sources, and the Earth is located near the direction of the fastest speed and the greatest energy of the shocks. As the two fast ejection shock events, the fast explosion of coronal mass of the extremely high temperature, the strong magnetic field, and the high speed background solar wind are also helpful to their rapid propagation. In the second step of “palpating”, we adopt a new membership function of the fast shock events for the ISF method. The predicted results show that for the onset time of the geomagnetic disturbance, the relative errors between the observational and the predicted results are 1.8% and 6.7%; and for the magnetic disturbance magnitude, the relative errors are 4.1% and 3.1%, re- spectively. Furthermore, the comparison among the predicted results of our two-step method with those of five other prevailing methods shows that the two-step method is advantageous. The results tell us that understanding the physical features of shock propagation thoroughly is of great importance in improving the prediction precision. 相似文献
153.
爆炸冲击的激光多普勒远距离测量技术的研究 总被引:1,自引:0,他引:1
利用激光多普勒效应和数字信号处理方法,获取爆炸冲击过程中的高速变形参数,以此作为对爆炸强度分析的依据。根据爆炸变形的特点,设计了外差式纵向激光多普勒测量系统,提出了相应的数字滤波和频谱分析的信号处理方法,实现了爆炸变形的动态测量。系统测量的位移量程为±30mm,速度量程为-10~+20m/s,测量距离为4.5m。与振动台的试验对比,位移测量相对误差小于1%。给出了圆筒钢制爆炸容器在300gTNT当量炸药爆炸过程中弹性变形的测量结果。 相似文献
154.
155.
During the last ten years, Micro-electromechanicalSystems (MEMS) technology developed very rapidlyand with that came great achievements. Currently, theMEMS devices are different types of sensors, which areusually applied to measure physical quantities such aspressure, the acoustic signal, mass, motion, accelera-tion, rotation, velocity of flow, chemical reaction, vi-bration, and so on. Additionally, some sensors havebeen manufactured[1]. MEMS packaging technologydevelops slowly due to the… 相似文献
156.
157.
158.
159.
160.
碰撞引起的宇航设备冲击响应仿真分析 总被引:1,自引:0,他引:1
利用运动学、动力学原理、有限元等分析方法对宇航设备在碰撞过程中的碰撞速度、撞击力、静强度、动力学响应等进行了仿真分析,由于碰撞力无法直接测量,应用碰撞理论和简化假设处理,计算得到碰撞力的分布函数,通过应用有限元理论和通用有限元程序NASTRAN,建立了研究对象的有限元模型,计算得到结构力学响应并结合以往的环境试验结果,验证了局部应力过高导致次结构破坏的现象,得出了主结构内部无法检测部件的环境适应性结论。还将理论仿真结果与模拟试验测量结果进行了对比分析,计算结果与实测结果有较好的一致性。分析表明,利用运动学和碰撞的有关理论可以较好地模拟文中设备的碰撞过程,对于撞击力的分布服从半正弦分布的假设在工程实践中是可行的。计算结构频率耦合作用而产生的结构内部放大或衰减效应。 相似文献