全文获取类型
收费全文 | 27257篇 |
免费 | 962篇 |
国内免费 | 610篇 |
专业分类
电工技术 | 728篇 |
综合类 | 967篇 |
化学工业 | 5660篇 |
金属工艺 | 4695篇 |
机械仪表 | 971篇 |
建筑科学 | 780篇 |
矿业工程 | 264篇 |
能源动力 | 258篇 |
轻工业 | 1634篇 |
水利工程 | 111篇 |
石油天然气 | 336篇 |
武器工业 | 124篇 |
无线电 | 2037篇 |
一般工业技术 | 7342篇 |
冶金工业 | 514篇 |
原子能技术 | 286篇 |
自动化技术 | 2122篇 |
出版年
2024年 | 32篇 |
2023年 | 144篇 |
2022年 | 430篇 |
2021年 | 573篇 |
2020年 | 352篇 |
2019年 | 311篇 |
2018年 | 358篇 |
2017年 | 483篇 |
2016年 | 836篇 |
2015年 | 1467篇 |
2014年 | 1625篇 |
2013年 | 1621篇 |
2012年 | 1513篇 |
2011年 | 2776篇 |
2010年 | 2216篇 |
2009年 | 2174篇 |
2008年 | 1793篇 |
2007年 | 1661篇 |
2006年 | 1177篇 |
2005年 | 1206篇 |
2004年 | 1209篇 |
2003年 | 1252篇 |
2002年 | 1115篇 |
2001年 | 429篇 |
2000年 | 333篇 |
1999年 | 362篇 |
1998年 | 247篇 |
1997年 | 211篇 |
1996年 | 160篇 |
1995年 | 127篇 |
1994年 | 98篇 |
1993年 | 65篇 |
1992年 | 61篇 |
1991年 | 37篇 |
1990年 | 36篇 |
1989年 | 33篇 |
1988年 | 32篇 |
1987年 | 19篇 |
1986年 | 24篇 |
1985年 | 24篇 |
1984年 | 25篇 |
1983年 | 14篇 |
1982年 | 21篇 |
1981年 | 33篇 |
1980年 | 72篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1975年 | 5篇 |
1973年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
The aim of this research is to investigate how ammonia treatment of the surface can influence the activity of a viscose-based activated carbon cloth (ACC) for the oxidative retention of H2S and SO2 in humid air at 25 °C. Surface basic nitrogen groups were introduced either by treatment with ammonia/air at 300 °C or with ammonia/steam at 800 °C. The pore structure of the samples so prepared was examined by adsorption measurements. Changes in the surface chemistry were assessed by X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and temperature programmed desorption (TPD). The change of ACC activity could not be merely attributed to surface nitrogen groups but to other changes in the support. Ammonia/steam treatment improved ACC performance the most, not only by introducing nitrogen surface groups, but also by extending the microporosity and by modifying the distribution of surface oxygen groups. Successive adsorption-regeneration cycles showed important differences between oxidative retention of H2S and SO2 and the subsequent catalyst/support regeneration process. 相似文献
143.
本文在介绍激光共聚焦生物芯片扫描仪结构原理基础上,论述了基于DSP的PC测控采集技术、基于PCI总线的PC与DSP通信技术等关键技术。 相似文献
144.
8bit嵌入式单片机系统A/D变换的两个关键指标是有效分辨率和信噪比(SNR)。通过对过采样(Over sample)和求均值(Average)理论的分析,得出“对噪声源的特性为白噪声的信号,每增加一位分辨率可以通过用4倍的过采样频率进行采样来达到。而分辨率每增加一位将使SNR增加6dB”的结论。进而采用8bit徽处理器内嵌12bit ADC成功实现了16bit ADC的精度,即小数点后两位(25.99℃)的温度测量,和小数点后四位(2.4299 V)的直流电压测量. 相似文献
145.
文章对国内外开展微区薄层电阻测试的方法进行了综述,特别对改进范德堡四探针技术方法的测试原理、测试过程与测试结果进行了论述与分析,对微区电阻测试方法的进一步发展提出了一种可操作的方法,并研制出新型四探针测试样机。 相似文献
146.
147.
148.
Substituted uracils were tested as corrosion inhibitors of copper in 3% NaCl medium using electrochemical polarisation, impedance measurements and non-electrochemical techniques (weight loss, IR and UV-visible). This study permitted to follow the evolution of the inhibitory effect of the uracil derivatives, according to their substituents, on copper in 3% NaCl medium. Comparison of results showed that dithiouracil (DTUr) was the best inhibitor. The maximum inhibition efficiency reached 98% at 10−3 M. DTUr adsorbs on the copper surface according to the Frumkin isotherm model. 相似文献
149.
150.
Hauke Harms Hans-Peter Volkland Andreas Hiltpolt Alexander J.B Zehnder 《Corrosion Science》2003,45(8):1717-1732
To study the effect of strong iron-ligands on steel corrosion, mild steel electrodes were immersed in solutions containing 20 mM phosphate buffer (pH=7.2) and between 0.01 mM and 1 M of either the iron(II)-chelators 2,2′-bipyridine or FerroZine, or the iron(III)-chelators citrate or acetylacetonate. Resulting surface reactions were investigated by quantifying the electrochemical potential (E), the electrochemical polarization resistance (Rp), the corrosion current (Icorr) and the release of iron into solution. The surface was further analyzed by scanning electron microscopy (SEM/SEM-EDAX) and atomic force microscopy. Concentrations of 0.1 mM of any of the chelators led to slight, temporary changes in E, Icorr and Rp. Concentrations of 10 mM resulted in characteristic changes of E, which were the same for all chelators and in the precipitation of FePO4 in the case of citrate and acetylacetonate, or vivianite [Fe3(PO4)2 · 8H2O] in the case of bipyridine and FerroZine. Concentrations of 1 mM of both iron(III)-chelators led to a temporary drop of E similar to that found with 0.1 mM chelator. With iron(II)-chelators, E dropped to about −500 mV before oscillating for several days. The amplitudes of the oscillations were up to 200 mV with periods of 30 and 20-25 min for bipyridine and FerroZine, respectively. 相似文献