全文获取类型
收费全文 | 29965篇 |
免费 | 2759篇 |
国内免费 | 1342篇 |
专业分类
电工技术 | 1830篇 |
技术理论 | 4篇 |
综合类 | 2043篇 |
化学工业 | 4901篇 |
金属工艺 | 1858篇 |
机械仪表 | 2034篇 |
建筑科学 | 2319篇 |
矿业工程 | 912篇 |
能源动力 | 853篇 |
轻工业 | 2324篇 |
水利工程 | 565篇 |
石油天然气 | 2097篇 |
武器工业 | 243篇 |
无线电 | 3245篇 |
一般工业技术 | 3380篇 |
冶金工业 | 1305篇 |
原子能技术 | 337篇 |
自动化技术 | 3816篇 |
出版年
2024年 | 183篇 |
2023年 | 629篇 |
2022年 | 1117篇 |
2021年 | 1469篇 |
2020年 | 1197篇 |
2019年 | 880篇 |
2018年 | 977篇 |
2017年 | 1064篇 |
2016年 | 921篇 |
2015年 | 1334篇 |
2014年 | 1519篇 |
2013年 | 1772篇 |
2012年 | 1858篇 |
2011年 | 2068篇 |
2010年 | 1764篇 |
2009年 | 1599篇 |
2008年 | 1665篇 |
2007年 | 1537篇 |
2006年 | 1593篇 |
2005年 | 1363篇 |
2004年 | 873篇 |
2003年 | 838篇 |
2002年 | 890篇 |
2001年 | 784篇 |
2000年 | 669篇 |
1999年 | 733篇 |
1998年 | 530篇 |
1997年 | 452篇 |
1996年 | 405篇 |
1995年 | 346篇 |
1994年 | 273篇 |
1993年 | 186篇 |
1992年 | 153篇 |
1991年 | 97篇 |
1990年 | 85篇 |
1989年 | 61篇 |
1988年 | 43篇 |
1987年 | 42篇 |
1986年 | 24篇 |
1985年 | 20篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1959年 | 1篇 |
1953年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
随着航空技术和微电子技术的发展,航空电子系统朝着综合化、智能化、模块化、标准化和系统化的方向发展,CAN总线由于其低成本、协议开放、实现简单、速率快、挂接节点多的特点得到了广泛应用,而这又对其可靠性提出了新的要求;由于飞行器上的众多设备均作为节点挂在CAN总线上,如果总线出现故障会对飞行器的安全带来灾难性的后果;作者在对CAN总线模型进行分析的基础上提出一种双余度CAN总线模型,并给出了实现方法,经过实践验证,该方法切实可行,并显著提高了系统可靠性. 相似文献
72.
Sheng Tian 《哈尔滨工业大学学报(英文版)》2015,22(3):101-106
Full frontal impact theory needs researching and exploring to satisfy the primary safety design of occupant restraint system,avoiding the increasingly "engineering"trend in order to develop and design safety vehicle. After occupant restraint system is simulated by using linear elastic stiffness k,the occupant-vehicle frontal rigid barrier impact model is established. Dynamic equation of dummy chest coupling vehicle is built for full frontal impact based on ordinary vehicle deceleration by Hooke law,and the equation is solved by comparing coefficient and satisfying boundary qualifications. While relative vehicle characteristic parameters are kept unchanging,the actual vehicle deceleration is fitted to the simplified equivalent square wave( ESW),tipped equivalent square wave( TESW) and equivalent dual trapezoids wave( EDTW). Phase angle and amplitude A of dynamic equations based on ESW,TESW and EDTW are calculated and deduced. The results show that: the dynamic equation of dummy chest coupling vehicle can be well utilized to instruct the primary safety design of full frontal impact for objective vehicle to satisfy chest deceleration demands and the equation based on TESW is best for this design. 相似文献
73.
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
74.
Shuixian Yang Hetuo Chen Jianmin Li Hao Guo Xiaojian Mao Run Tian Jian Zhang Shiwei Wang 《Journal of the American Ceramic Society》2021,104(2):1040-1046
The oxidation behavior and mechanism of aluminum oxynitride (AlON) powder exposed to air at elevated temperatures between 800°C and 1300°C was investigated by X-ray diffractometry (XRD), scanning electron microscope (SEM), electron spin resonance (ESR), nuclear magnetic resonance (NMR), and simultaneous thermogravimetry, differential thermal analysis, and mass spectrometry techniques (TG-DTA-MS). The weight of AlON gradually increases to a maximum value at 1150°C and then decreases with further heating. Meanwhile, AlON powder undergoes chemical changes, as evidenced by lattice expansion, and turns eventually into alumina. ESR spectra reveal the occurrence of lone pair electrons in the oxidized products and the intensity of corresponding resonance signal increases before disappearing with the increase in temperature. Combined with the results of NMR and TG-DTA-MS, the measured data suggest that Al-N in [AlO3N] tetrahedron and [AlO5N] octahedron are gradually oxidized into Al-O-N group with lone pair electrons, which causes continuous weight gain and lattice expansion. Further oxidation at higher temperatures results in alumina and N2. 相似文献
75.
76.
77.
78.
GAO Wenli SUI Zhitong North East University of Technology Shenyang China LU Ke LI Shuling WANG Jingtang State Key Laboratory for RSA Institute of Metal Research Academia Sinica Shenyang China Institute of Metal Research Academia Sinica Shenyang China 《金属学报(英文版)》1993,6(7):16-20
The crystallization kinetics of Pd-Cu-Si glass was studied by means of diferential scanningcalorimetry-Ⅱ.According to Kissinger peak shift meth(?)d and Arrhenius equation,theapparent activation energy was calculated.The crystallization kinetics follows Johnson-Mehl-Avrami equation with n=3.0 within 0.15相似文献
79.
80.
基于数字光处理(DLP)的数字微镜器件(DMD)灰度控制主要针对视频应用,故帧频较低,只有约60~120 Hz,而用DMD实现的伯努利矩阵作为压缩感知测量矩阵,是0-1二值矩阵,不需要灰度控制,且帧频要求通常在数千帧每秒.研制了基于Xilinx公司Virtex-5 FPGA的DMD控制系统来实现伯努利矩阵,系统由随机数发生器(RNG)、DDR2 SDRAM控制器、DMD控制器等模块组成.随机数发生器产生的随机数存储在DDR2 SDRAM中,实现与DMD的高速数据传输.经验证,该系统可实现二值高速显示,帧频可达到2 kHz. 相似文献