首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   250804篇
  免费   9981篇
  国内免费   5494篇
电工技术   8390篇
技术理论   6篇
综合类   6995篇
化学工业   39065篇
金属工艺   11768篇
机械仪表   9504篇
建筑科学   10097篇
矿业工程   2896篇
能源动力   6550篇
轻工业   25413篇
水利工程   3700篇
石油天然气   6160篇
武器工业   753篇
无线电   28313篇
一般工业技术   40662篇
冶金工业   35644篇
原子能技术   5150篇
自动化技术   25213篇
  2023年   1676篇
  2022年   3522篇
  2021年   4838篇
  2020年   3720篇
  2019年   3311篇
  2018年   4336篇
  2017年   4690篇
  2016年   4529篇
  2015年   5083篇
  2014年   7202篇
  2013年   13016篇
  2012年   10528篇
  2011年   12780篇
  2010年   10754篇
  2009年   11108篇
  2008年   11067篇
  2007年   10618篇
  2006年   9248篇
  2005年   8040篇
  2004年   6840篇
  2003年   6096篇
  2002年   6096篇
  2001年   5813篇
  2000年   5027篇
  1999年   4926篇
  1998年   10844篇
  1997年   7763篇
  1996年   6000篇
  1995年   4508篇
  1994年   3796篇
  1993年   3704篇
  1992年   2738篇
  1991年   2620篇
  1990年   2475篇
  1989年   2484篇
  1988年   2407篇
  1987年   2150篇
  1986年   2087篇
  1985年   2375篇
  1984年   2193篇
  1983年   2022篇
  1982年   1894篇
  1981年   1954篇
  1980年   1816篇
  1979年   1827篇
  1978年   1777篇
  1977年   2110篇
  1976年   2687篇
  1975年   1557篇
  1973年   1608篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
A novel driver-assist stability system for all-wheel-drive electric vehicles is introduced. The system helps drivers maintain control in the event of a driving emergency, including heavy braking or obstacle avoidance. The system comprises a fuzzy logic system that independently controls wheel torque to prevent vehicle spin. Another fuzzy wheel slip controller is used to enhance vehicle stability and safety. A neural network is trained to generate the required reference for yaw rate. Vehicle true speed is estimated by a sensor data fusion method. The intrinsic robustness of fuzzy controllers allows the system to operate in different road conditions successfully. Moreover, the ease of implementing fuzzy controllers gives a potential for vehicle stability enhancement.  相似文献   
93.
A new dual-quantisation sigma-delta modulator is proposed, which introduces an additional feedback path in the input of the second integrator. In this way, unlike other dual-quantisation architectures, larger signal-to-noise ratios can be obtained by means of aggressive noise-shaping, like in a conventional multibit modulator. The proposed modulator is also shown to be more robust against non-idealities than other dual-quantisation architectures.  相似文献   
94.
The design, fabrication, and performance of double-stage taper photodiodes (DSTPs) are reported. The objective of this work is to develop devices compatible with 40-Gb/s applications. Such devices require high efficiency, ultrawide band, high optical power handling capability, and compatibility with low-cost module fabrication. The integration of mode size converters improves both the coupling efficiency and the responsivity with a large fiber mode diameter. Responsivity of 0.6 A/W and 0.45 A/W are achieved with a 6-/spl mu/m fiber mode diameter and cleaved fiber, respectively, providing relaxed alignment tolerances (/spl plusmn/1.6 /spl mu/m and /spl plusmn/2 /spl mu/m, respectively), compatible with cost-effective packaging techniques. DSTPs also offer a wide bandwidth greater than 40 GHz and transverse-electric/transverse-magnetic polarization dependence lower than 0.2 dB. Furthermore, a DSTP saturation current as high as 11 mA results in optical power handling greater than +10 dBm and a high output voltage of 0.8 V. These capabilities allow the photodiode to drive the decision circuit without the need of a broad-band electrical amplifier. The DSTP devices presented here demonstrate higher responsivities with large fiber mode diameter and better optical power handling capabilities and are compared with classical side-illuminated photodiodes.  相似文献   
95.
The problem of computing, in a subband audio coder, the maximum quantisation noise power that can be injected in each band to ensure transparent coding when low selectivity filter banks are used, is addressed. A low complexity strategy, taking into account the frequency responses of the synthesis filter bank, is proposed for achieving an overall distortion due to quantisation noise always below the masking threshold (provided by a psycho-acoustic model) for any length prototype filters.  相似文献   
96.
This short paper discusses the method of effectively canceling equal status normal mode noise not only on a sensor line but also on a transmission line of an optical instrument using a sensor with a sensordummy resistance  相似文献   
97.
1/f noise sources   总被引:2,自引:0,他引:2  
This survey deals with 1/f noise in homogeneous semiconductor samples. A distinction is made between mobility noise and number noise. It is shown that there always is mobility noise with an α value with a magnitude in the order of 10-4. Damaging the crystal has a strong influence on α, α may increase by orders of magnitude. Some theoretical models are briefly discussed none of them can explain all experimental results. The α values of several semiconductors are given. These values can be used in calculations of 1/f noise in devices  相似文献   
98.
The authors survey published results on the application of metal diffraction gratings as laser power or energy dividers when the laser beam is split into two approximately equal pans. The normal incidence of laser radiation on metal diffraction gratings of various profiles in the case of three propagating diffraction orders n=0, ±1 is discussed, along with the case of oblique incidence with only two propagating diffraction orders n=0 and n =–1.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 22–26, February, 1994.  相似文献   
99.
ABSTRACT: The objective of this work was to observe the microstructure of feta cheese using confocal scanning laser microscopy. Low fat cheese and cheese containing capsule-producing cultures were made. The protein network was observed using the reflectance mode of the confocal microscope. Fat was stained by Nile red dye diluted with whey. More even distribution of fat with a larger number of smaller globules was observed in cheese made with noncapsule-forming culture compared to that made with the capsule-forming culture. Nonfat cheese had compact structure when made with noncapsule-forming culture which contrasted with the open structure observed in cheese made with the capsule-forming culture  相似文献   
100.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号