全文获取类型
收费全文 | 15741篇 |
免费 | 234篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 186篇 |
综合类 | 3篇 |
化学工业 | 1991篇 |
金属工艺 | 361篇 |
机械仪表 | 339篇 |
建筑科学 | 512篇 |
矿业工程 | 60篇 |
能源动力 | 306篇 |
轻工业 | 1213篇 |
水利工程 | 89篇 |
石油天然气 | 119篇 |
无线电 | 1511篇 |
一般工业技术 | 2334篇 |
冶金工业 | 5418篇 |
原子能技术 | 159篇 |
自动化技术 | 1396篇 |
出版年
2021年 | 97篇 |
2019年 | 102篇 |
2018年 | 135篇 |
2017年 | 101篇 |
2016年 | 94篇 |
2015年 | 107篇 |
2014年 | 224篇 |
2013年 | 571篇 |
2012年 | 304篇 |
2011年 | 407篇 |
2010年 | 332篇 |
2009年 | 336篇 |
2008年 | 450篇 |
2007年 | 439篇 |
2006年 | 433篇 |
2005年 | 386篇 |
2004年 | 323篇 |
2003年 | 362篇 |
2002年 | 310篇 |
2001年 | 321篇 |
2000年 | 315篇 |
1999年 | 409篇 |
1998年 | 1556篇 |
1997年 | 947篇 |
1996年 | 677篇 |
1995年 | 472篇 |
1994年 | 412篇 |
1993年 | 431篇 |
1992年 | 281篇 |
1991年 | 253篇 |
1990年 | 270篇 |
1989年 | 224篇 |
1988年 | 225篇 |
1987年 | 213篇 |
1986年 | 202篇 |
1985年 | 260篇 |
1984年 | 208篇 |
1983年 | 205篇 |
1982年 | 201篇 |
1981年 | 179篇 |
1980年 | 195篇 |
1979年 | 128篇 |
1978年 | 135篇 |
1977年 | 245篇 |
1976年 | 347篇 |
1975年 | 136篇 |
1974年 | 125篇 |
1973年 | 107篇 |
1972年 | 78篇 |
1970年 | 83篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
991.
Kean P.N. Smith K. Sinclair B.D. Sibbett W. Rowe C.J. Reid D.C.J. 《Electronics letters》1987,23(23):1241-1243
We have constructed a completely integrated fibre Raman oscillator using two fibre grating reflectors. This was synchronously mode-locked using a CW mode-locked Nd:YAG laser operating at 1.06?m. Spectral and temporal characteristics of the Raman oscillator are presented. 相似文献
992.
Tench R. Delavaux J.-M. Tzeng L. Smith R. Buhl L. Alferness R. 《Lightwave Technology, Journal of》1987,5(4):492-501
This article describes the fabrication and performance evaluation ofX -cut andZ -cut Ti:LiNbO3 traveling wave waveguide phase modulators designed for coherent systems applications at 1.3 and 1.5 μm. Details of device fabrication and measurements of phase shift as a function of optical wavelength, input polarization, modulation voltage, and modulation frequency are reported. Phase modulator performance in a 40-Mbit/s self-heterodyne coherent DPSK experiment is also discussed. 相似文献
993.
994.
995.
Don C. Smith 《Refocus》2001,2(7):48
Despite early indications from the Bush Administration that renewable energy was neither a top priority nor to be funded at levels seen in the Clinton Administration, there appears to be a slow back peddling on this issue. President George W. Bush's proposed energy programme has been encountering mounting hostility on Capitol Hill in Washington as well as significantly growing opposition among many Americans. Don Smith, US correspondent for Refocus magazine reports. 相似文献
996.
997.
ABSTRACT Feedback from a pressure transducer at the pump output is used to activate a stepper motor to adjust an air regulator that controls the pump pressure. Control within 2.4% at 615 psig was obtained. In addition, linear pressure programs at flow rates between 0.2 and 2 cc/min were performed. Control or programming was limited only by the inherent range of the pressure transducer. 相似文献
998.
999.
Laura J. Turbini Brian A. Smith James Brokaw John Williams Jürgen Gamalski 《Journal of Electronic Materials》2000,29(10):1164-1169
Wireless devices such as pagers and cellular phones are becoming common consumer items. These products require low loss RF
signal propagation which is affected by material choices and processing conditions. This paper examines the effect of a series
of no-clean solder pastes on signal integrity using an RF test circuit which sends a broadband signal through a gallium arsenide
antenna switch and measures its transmission using a network analyzer. The test circuit also measures signal leakage. This
paper reports on two different test vehicles, one that uses a 900 MHz antenna switch, and the other that uses a 2.0 GHz antenna
switch. The transmission and leakage readings were taken daily for 16–21 days while the test vehicles were under accelerated
aging conditions of 85°C and 85% RH. Average values for the readings for each solder paste were plotted to provide comparison
among the pastes. The comparison data clearly distinguish solder pastes that provide consistency throughout the test period
from those which do not. 相似文献
1000.