全文获取类型
收费全文 | 51760篇 |
免费 | 5559篇 |
国内免费 | 3192篇 |
专业分类
电工技术 | 3911篇 |
技术理论 | 2篇 |
综合类 | 4348篇 |
化学工业 | 7750篇 |
金属工艺 | 2994篇 |
机械仪表 | 3331篇 |
建筑科学 | 4449篇 |
矿业工程 | 1600篇 |
能源动力 | 1424篇 |
轻工业 | 4368篇 |
水利工程 | 1255篇 |
石油天然气 | 2415篇 |
武器工业 | 570篇 |
无线电 | 5593篇 |
一般工业技术 | 5631篇 |
冶金工业 | 2459篇 |
原子能技术 | 715篇 |
自动化技术 | 7696篇 |
出版年
2024年 | 287篇 |
2023年 | 924篇 |
2022年 | 1694篇 |
2021年 | 2253篇 |
2020年 | 1852篇 |
2019年 | 1534篇 |
2018年 | 1598篇 |
2017年 | 1842篇 |
2016年 | 1639篇 |
2015年 | 2422篇 |
2014年 | 3054篇 |
2013年 | 3422篇 |
2012年 | 3723篇 |
2011年 | 3739篇 |
2010年 | 3462篇 |
2009年 | 3183篇 |
2008年 | 3292篇 |
2007年 | 3116篇 |
2006年 | 2957篇 |
2005年 | 2262篇 |
2004年 | 1771篇 |
2003年 | 1651篇 |
2002年 | 1949篇 |
2001年 | 1700篇 |
2000年 | 1153篇 |
1999年 | 862篇 |
1998年 | 551篇 |
1997年 | 480篇 |
1996年 | 436篇 |
1995年 | 353篇 |
1994年 | 265篇 |
1993年 | 165篇 |
1992年 | 171篇 |
1991年 | 118篇 |
1990年 | 84篇 |
1989年 | 71篇 |
1988年 | 68篇 |
1987年 | 39篇 |
1986年 | 50篇 |
1985年 | 19篇 |
1984年 | 18篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 25篇 |
1980年 | 34篇 |
1979年 | 14篇 |
1977年 | 10篇 |
1976年 | 23篇 |
1975年 | 10篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
111.
Bong Ban S. Baker Curtis L. Long Dale D. 《IEEE transactions on bio-medical engineering》1976,(1):75-77
A stimulator circuit is presented which is capable of generating pulse train waveforms suitable for neurophysiological experiments are available, as well as special test conditions such as dishabituation. Digital and linear integrated circuits are used to provide precise control over the stimulus parameters. 相似文献
112.
课堂教学质量的综合量化评估研究 总被引:1,自引:0,他引:1
张青 《武汉理工大学学报(信息与管理工程版)》2006,28(5):187-189,192
结合所设计的两层结构的课堂教学质量综合评价指标集,应用模糊数学理论,设计提出了一种课堂教学质量综合量化评估方法。并将该方法应用到实际,结果证明所提出的方法能科学、客观、公正、准确地反映出课堂教学的综合质量,为提高高校教学质量,加强教学管理提供了量化依据。 相似文献
113.
Qing Dai Menzies D. Qiang Wang Ostafin A. E. Brown S. N. Meisel D. Maginn E. J. 《Nanotechnology, IEEE Transactions on》2006,5(6):677-682
A novel technique to monitor the synthesis process of encapsulated acetylacetonatocarbonyl triphenylphosphinerhodium within a microsilica nanoshell has been studied using inductively coupled plasma (ICP) techniques. Nanospheres sized around 50-100 nm were obtained and ICP was used to quantify the exact composition of rhodium, phosphorous, and silicon with differing digestion solvents. In addition, ICP was used to detect rhodium and phosphorous in the nano core-shell catalysts as a quality control procedure 相似文献
114.
The development, operation, and applications of two configurations of an integrated plasma-aided nanofabrication facility (IPANF) comprising low-frequency inductively coupled plasma-assisted, low-pressure, multiple-target RF magnetron sputtering plasma source, are reported. The two configurations of the plasma source have different arrangements of the RF inductive coil: a conventional external flat spiral “pancake” coil and an in-house developed internal antenna comprising two orthogonal RF current sheets. The internal antenna configuration generates a “unidirectional” RF current that deeply penetrates into the plasma bulk and results in an excellent uniformity of the plasma over large areas and volumes. The IPANF has been employed for various applications, including low-temperature plasma-enhanced chemical vapor deposition of vertically aligned single-crystalline carbon nanotips, growth of ultra-high aspect ratio semiconductor nanowires, assembly of optoelectronically important Si, SiC, and Al1-xInxN quantum dots, and plasma-based synthesis of bioactive hydroxyapatite for orthopedic implants. 相似文献
115.
116.
La0.7 Ca0.3 CrO3 powder consisting of superfine and uniform particles ( 100-200 nm ) were synthesized using a glycine-nitrate process ( GNP ). The sintering and electronic conducting properties of La0.7 Ca0.3 CrO3 were invetigated in the sintering temperature range of 1 200-1 450 ℃. The desired morphology of the powder significantly improved its sinterability. La0.7 Ca0.3 CrO3 ceramics sintered at 1 250-1 450 ℃ show high relative densities above 95 % . The ceramics sintered at 1 250-1 400 ℃ have very similar electronic conduct- ing properties, providing electronic conductivities around 55 Ω^-1 cm^-1 at a measuring temperature of 800 ℃ . Further increasing the sintering temperature to 1450 ℃ led to an apparent degradation of electronic conducting properties. This research demonstrates the advantage of the GNP in producing La0.7 Ca0.3 CrO3 with respect to the enhanced sintering properties and superior electronic conducting properties. 相似文献
117.
118.
加工配送是当前一种新型的钢材物流服务方式,在营销战略方面已经越来越受到钢铁企业的高度重视。对当前国内钢材加工配送的市场状况的成因进行了分析,对部分生产企业的基本特点进行了描述,并对钢材加工配送未来的发展方向进行了阐述。 相似文献
119.
Paul F. Mlakar Donald O. Dusenberry James R. Harris Gerald Haynes Long T. Phan Mete A. Sozen 《Canadian Metallurgical Quarterly》2005,19(3):197-205
On September 11, 2001, an airliner was intentionally crashed into the Pentagon. It struck at the first elevated slab on the west wall, and slid approximately 310?ft (94.5?m) diagonally into the building. The force of the collision demolished numerous columns and the fa?ade of the exterior wall, and induced damage to first-floor columns and the first elevated slab over an area approximately 90?ft (27.4?m) wide and 310?ft (94.5?m) long. None of the building collapsed immediately. The portion that remained standing, even after an intense fire, sustained substantial damage at the first-floor level. 相似文献
120.
Often quantitative data in the social sciences have only ordinal justification. Problems of interpretation can arise when least squares multiple regression (LSMR) is used with ordinal data. Two ordinal alternatives are discussed, dominance-based ordinal multiple regression (DOMR) and proportional odds multiple regression. The Q2 statistic is introduced for testing the omnibus null hypothesis in DOMR. A simulation study is discussed that examines the actual Type I error rate and power of Q2 in comparison to the LSMR omnibus F test under normality and non-normality. Results suggest that Q2 has favorable sampling properties as long as the sample size-to-predictors ratio is not too small, and Q2 can be a good alternative to the omnibus F test when the response variable is non-normal. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献