全文获取类型
收费全文 | 6253篇 |
免费 | 828篇 |
国内免费 | 522篇 |
专业分类
电工技术 | 618篇 |
综合类 | 689篇 |
化学工业 | 157篇 |
金属工艺 | 123篇 |
机械仪表 | 468篇 |
建筑科学 | 152篇 |
矿业工程 | 50篇 |
能源动力 | 125篇 |
轻工业 | 151篇 |
水利工程 | 32篇 |
石油天然气 | 42篇 |
武器工业 | 91篇 |
无线电 | 2415篇 |
一般工业技术 | 559篇 |
冶金工业 | 205篇 |
原子能技术 | 107篇 |
自动化技术 | 1619篇 |
出版年
2024年 | 17篇 |
2023年 | 77篇 |
2022年 | 124篇 |
2021年 | 160篇 |
2020年 | 218篇 |
2019年 | 180篇 |
2018年 | 178篇 |
2017年 | 238篇 |
2016年 | 257篇 |
2015年 | 281篇 |
2014年 | 384篇 |
2013年 | 496篇 |
2012年 | 447篇 |
2011年 | 452篇 |
2010年 | 343篇 |
2009年 | 355篇 |
2008年 | 384篇 |
2007年 | 442篇 |
2006年 | 363篇 |
2005年 | 336篇 |
2004年 | 293篇 |
2003年 | 261篇 |
2002年 | 206篇 |
2001年 | 189篇 |
2000年 | 155篇 |
1999年 | 115篇 |
1998年 | 93篇 |
1997年 | 99篇 |
1996年 | 78篇 |
1995年 | 62篇 |
1994年 | 59篇 |
1993年 | 44篇 |
1992年 | 38篇 |
1991年 | 29篇 |
1990年 | 26篇 |
1989年 | 12篇 |
1988年 | 24篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1965年 | 6篇 |
1964年 | 4篇 |
1963年 | 4篇 |
1962年 | 3篇 |
1956年 | 3篇 |
排序方式: 共有7603条查询结果,搜索用时 15 毫秒
31.
32.
P. Kristiansson C. M. Nilsson H. Busk L. Malmqvist M. Elfman K. G. Malmqvist J. Pallon K. A. Sj land R. J. Utui C. Yang 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1997,130(1-4):303-307
A technique for measuring optical dot gain, i.e. the relative difference between the actual screen dot and the optically perceived one, is presented. By combining measurements from the non-optical nuclear microprobe with data from image analyzing technique the optical dot gain can be determined. The procedure to reach pixel by pixel correlation on a micrometer scale is discussed. In the newsprint sample studied in this investigation a typical optical dot gain between 15 and 20% was deduced. The variation in the optical dot gain was correlated with other characteristic parameters of the print and newsprint and especially a positive correlation to the mass density of the newsprint was observed. 相似文献
33.
The semiconductor thin disk laser is a new type of semiconductor laser. This work gives the basic operation function of the semiconductor disk laser, and analyses the heat effect by the experimentally measured photoluminescence spectrum of the laser chip at different pump power and different temperatures. We can see that: with increasing pump power, the thermal effect of the gain material becomes seriously and causes the saturation of carrier lifetime, so the electron-hole pair created in the absorbtion lay... 相似文献
34.
模拟乘法器的简易分析方法 总被引:1,自引:0,他引:1
刘淑英 《电气电子教学学报》2002,24(5):56-57,60
提出了一种模拟乘法器工作原理的简易分析方法,与通用的一般方法相比,这种方法避开了较复杂的数学推导,采用大学熟悉的公式从而使分析过程简便易懂。 相似文献
35.
36.
Kallie Christopher S.; Schrater Paul R.; Legge Gordon E. 《Canadian Metallurgical Quarterly》2007,33(1):183
Walking without vision results in veering, an inability to maintain a straight path that has important consequences for blind pedestrians. In this study, the authors addressed whether the source of veering in the absence of visual and auditory feedback is better attributed to errors in perceptual encoding or undetected motor error. Three experiments had the following results: No significant differences in the shapes of veering trajectories were found between blind and blindfolded participants; accuracy in detecting curved walking paths was not correlated with simple measures of veering behavior; and explicit perceptual cues to initial walking direction did not reduce veering. The authors present a model that accounts for the major characteristics of participants' veering behavior by postulating 3 independent sources of undetected motor error: initial orientation, consistent biases in step direction, and, most important, variable error in individual steps. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
37.
38.
39.
Previous work on transmitter antenna diversity has shown that the use of multiple transmitter antennas at the base station results in improved performance due to increase of diversity (path diversity). This happens with no bandwidth cost, even when the signal quality along several paths is poor, but the receiver estimates the channel with accuracy. This paper evaluates the effects of channel estimation errors in the performance of the schemes designated as Space-Time Transmitter Diversity (STTD) and Selective Transmitter Diversity (STD). We consider low to medium signal to noise ratios characteristic of Wideband Code Division Multiple Access (WCDMA) networks. Different fading channel models are considered for comparison between the two schemes. The improvement due to convolutional coding associated with these techniques is also evaluated. 相似文献
40.