全文获取类型
收费全文 | 252926篇 |
免费 | 2791篇 |
国内免费 | 870篇 |
专业分类
电工技术 | 4807篇 |
综合类 | 193篇 |
化学工业 | 36134篇 |
金属工艺 | 9507篇 |
机械仪表 | 7549篇 |
建筑科学 | 6081篇 |
矿业工程 | 880篇 |
能源动力 | 7225篇 |
轻工业 | 21095篇 |
水利工程 | 2202篇 |
石油天然气 | 3230篇 |
武器工业 | 15篇 |
无线电 | 34279篇 |
一般工业技术 | 49990篇 |
冶金工业 | 48568篇 |
原子能技术 | 5077篇 |
自动化技术 | 19755篇 |
出版年
2021年 | 2172篇 |
2020年 | 1560篇 |
2019年 | 1915篇 |
2018年 | 3270篇 |
2017年 | 3308篇 |
2016年 | 3402篇 |
2015年 | 2219篇 |
2014年 | 3956篇 |
2013年 | 11478篇 |
2012年 | 6236篇 |
2011年 | 8573篇 |
2010年 | 6905篇 |
2009年 | 7885篇 |
2008年 | 8402篇 |
2007年 | 8297篇 |
2006年 | 7365篇 |
2005年 | 6497篇 |
2004年 | 6282篇 |
2003年 | 6555篇 |
2002年 | 6037篇 |
2001年 | 6515篇 |
2000年 | 5973篇 |
1999年 | 6389篇 |
1998年 | 16490篇 |
1997年 | 11415篇 |
1996年 | 8796篇 |
1995年 | 6608篇 |
1994年 | 5908篇 |
1993年 | 5844篇 |
1992年 | 4134篇 |
1991年 | 4020篇 |
1990年 | 3857篇 |
1989年 | 3648篇 |
1988年 | 3561篇 |
1987年 | 3017篇 |
1986年 | 2944篇 |
1985年 | 3207篇 |
1984年 | 2929篇 |
1983年 | 2829篇 |
1982年 | 2638篇 |
1981年 | 2544篇 |
1980年 | 2463篇 |
1979年 | 2308篇 |
1978年 | 2108篇 |
1977年 | 2605篇 |
1976年 | 3566篇 |
1975年 | 1768篇 |
1974年 | 1731篇 |
1973年 | 1665篇 |
1972年 | 1466篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
The main principles of a measurement procedure are given and its implementation with the aid of an IR-imager AGA-780 is shown.State Institute of Applied Optics, Kazan. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 63, No. 1, pp. 109–113. July, 1992. 相似文献
992.
On the Theory of Electrical Phenomena in Combustion of Heterogeneous Systems with Condensed Products
V. K. Smolyakov A. I. Kirdyashkin Yu. M. Maksimov 《Combustion, Explosion, and Shock Waves》2002,38(6):675-680
The effect of the electromotive force arising in combustion of heterogeneous systems with condensed products is explained. A convective mechanism of arising regions with different charge densities due to charge transfer by the gas filtered in the pores is formulated on the basis of the developed physical concepts, estimates, and analysis of experimental data. Key words: combustion, electron emission, filtration, electromotive force. 相似文献
993.
Novel high voltage pumping circuits for low supply voltages are proposed. Utilising a small pumping circuit and the new substrate-connected techniques can enhance charge transfer efficiency and eliminate the body effect at low supply voltages. Furthermore, a diode-connected transistor technique can improve the reverse charge sharing phenomenon when the output has a load current. With this technique high boosted voltages can be obtained at low supply voltages 相似文献
994.
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
995.
996.
A simple method (based on Floquet theory) for obtaining the characteristic equation (and hence stability) of periodic discrete-time systems is presented. Using this method it is shown that 2-periodic controllers can be used to relocate the zeros of SISO plants. Some examples are considered to illustrate the use of 2-periodic controllers for robust control of finite gain margin problems 相似文献
997.
998.
999.
Jingkuang Chen Wise K.D. Hetke J.F. Bledsoe S.C. Jr. 《IEEE transactions on bio-medical engineering》1997,44(8):760-769
A bulk-micromachined multichannel silicon probe capable of selectively delivering chemicals at the cellular level as well as electrically recording from and stimulating neurons in vivo has been developed. The process buries multiple flow channels in the probe substrate, resulting in a hollow-core device, Microchannel formation requires only one mask in addition to those normally used for probe fabrication and is compatible with on-chip signal-processing circuitry. Flow in these microchannels has been studied theoretically and experimentally. For an effective channel diameter of 10 μm, a channel length of 4 mm, and water as the injected fluid, the flow velocity at 11 torr is about 1.3 mm/s, delivering 100 pl in 1 s. Intermixing of chemicals, with the tissue fluid due to natural diffusion through the outlet orifice becomes significant for dwell times in excess of about 30 min, and a shutter is proposed for chronic use. The probe has been used for acute monitoring of the neural responses to various chemical stimuli in guinea pig superior and inferior colliculus 相似文献
1000.
We have examined the applicability of this simple and effective test to polymer systems widely used in the medical industry. First, it was found that not every polymer examined exhibited a distinct onset of autocatalytic oxidation detectable by DSC. However, for cases where distinct onsets are found, powerful insights can be obtained. These included activation energy of the degradation, thermal oxidative shelf life prediction, and correlation, with product performances. Actual examples are presented to illustrate the utility of the test. 相似文献