全文获取类型
收费全文 | 663232篇 |
免费 | 56211篇 |
国内免费 | 25455篇 |
专业分类
电工技术 | 36610篇 |
技术理论 | 92篇 |
综合类 | 42609篇 |
化学工业 | 117681篇 |
金属工艺 | 35466篇 |
机械仪表 | 40792篇 |
建筑科学 | 51813篇 |
矿业工程 | 20930篇 |
能源动力 | 18222篇 |
轻工业 | 45188篇 |
水利工程 | 11582篇 |
石油天然气 | 41655篇 |
武器工业 | 4979篇 |
无线电 | 73641篇 |
一般工业技术 | 78481篇 |
冶金工业 | 34350篇 |
原子能技术 | 6180篇 |
自动化技术 | 84627篇 |
出版年
2024年 | 2314篇 |
2023年 | 8863篇 |
2022年 | 16108篇 |
2021年 | 22900篇 |
2020年 | 18559篇 |
2019年 | 16489篇 |
2018年 | 18876篇 |
2017年 | 21338篇 |
2016年 | 20093篇 |
2015年 | 26347篇 |
2014年 | 33082篇 |
2013年 | 40330篇 |
2012年 | 40917篇 |
2011年 | 45134篇 |
2010年 | 40123篇 |
2009年 | 38180篇 |
2008年 | 37213篇 |
2007年 | 35921篇 |
2006年 | 36993篇 |
2005年 | 32669篇 |
2004年 | 22077篇 |
2003年 | 20107篇 |
2002年 | 18777篇 |
2001年 | 17121篇 |
2000年 | 16888篇 |
1999年 | 18308篇 |
1998年 | 14367篇 |
1997年 | 12060篇 |
1996年 | 11390篇 |
1995年 | 9445篇 |
1994年 | 7781篇 |
1993年 | 5380篇 |
1992年 | 4321篇 |
1991年 | 3342篇 |
1990年 | 2603篇 |
1989年 | 2125篇 |
1988年 | 1756篇 |
1987年 | 1155篇 |
1986年 | 887篇 |
1985年 | 576篇 |
1984年 | 427篇 |
1983年 | 353篇 |
1982年 | 304篇 |
1981年 | 199篇 |
1980年 | 213篇 |
1979年 | 105篇 |
1978年 | 54篇 |
1977年 | 64篇 |
1976年 | 86篇 |
1975年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
本文研究了采用锁定放大相干检测技术的等离子体光发射谱检测系统。用该系统检测了仅用CF4作为刻蚀气体刻蚀非晶硅基薄膜的等离子体光发射谱。分析了检测结果和刻蚀机理。 相似文献
994.
995.
Li W. Aiken M. 《IEEE transactions on systems, man and cybernetics. Part C, Applications and reviews》1998,28(2):288-294
Many real-world decision-making problems fall into the general category of classification. Algorithms for constructing knowledge by inductive inference from example have been widely used for some decades. Although these learning algorithms frequently address the same problem of learning from preclassified examples and much previous work in inductive learning has focused on the algorithms' predictive accuracy, little attention has been paid to the effect of data factors on the performance of a learning system. An experiment was conducted using five learning algorithms on two data sets to investigate how the change in labeling the class attribute can alter the behavior of learning algorithms. The results show that different preclassification rules applied on the training examples can affect either the classification accuracy or classification structure 相似文献
996.
对数型产量衰减曲线方程的建立与应用 总被引:4,自引:0,他引:4
在产量衰减曲线方程的基础上,通过数学推导,得到了一种对数型产量减曲线方程。方程既可以用来预测油气田整个开发阶段的指标,又可以比较准确的测算油气田的可采集量。对国内外一些油田的实际应用表明,对数型产量衰减曲线方程是十分实用和有效的。 相似文献
997.
Yi-Min Wang Hua Lee Dipali V. Apte 《International journal of imaging systems and technology》1992,4(3):201-206
The matrix pencil (MP) method, based on the singular value decomposition (SVD), is applied to quantitative NMR spectroscopy. Its relationship to other SVD-based methods is also presented. Simulations and applications are given to demonstrate the capability of superior performance.©1993 John Wiley & Sons Inc 相似文献
998.
Air cleaning as a means of mitigating the risks arising from exposure to indoor radon progeny has been evaluated in a single-family house in the north eastem US. using an automated, semi-continuous activity-weighted size distribution measurement system. The measurements included radon concentration, condensation nuclei count, and activity-weighted size distribution of radon decay products. Measurements were made in the house with and without an operating air filtration system and with various particle sources common to normal indoor activities operating. Aerosols were generated by running water in a shower, candle burning, cigarette smoking, vacuuming, opening doors, and cooking. Using a room model, the changes in attachment rates, average attachment diameters, and deposition rates of the unattached fraction with and without the air cleaning system were calculated. In the presence of active aerosol sources, the air filtration unit typically reduced the concentration of particles within the hour following the end of particle generation. After candle burning, cigarette smoking, and vacuuming in the bedroom, the reductions of PAEC by air filtration are about 60% with the air filtration system operating in the bedroom. During cooking in the kitchen, the reductions of PAEC in the bedroom with the air filtration system were about 40%. However, for all cases the dose reductions were smaller than the particle and PAEC reductions. For those particles that were generated within the bedroom, there was a 20% to 50% reduction in dose. In the case of cooking where the door was open and particles infiltrated from the rest of the house, the dose reduction was only 5% on average and appears to be insignificant. Thus, the dose reductions were h e r than the reductions in activity concentration, but there were no cases where the estimated dose actually increased. 相似文献
999.
中药大蜜丸及所用包装材料软、粘、轻、小、光,较难实现机械化自动包装。通常的监控方法不适合蜜丸的自动包装。采用红外线光电控制器,解决了自动包装蜜丸时出现的瞬间无纸、无丸等自动控制。 相似文献
1000.
受中国电信委托、原邮电部经济技术发展研究中心在全国进行一次农村电信市场调查,以了解当前农村通信市场发展潜力,本文公布了此次调查的结果,从经济能力、资费和潜在市场等方面提出了发展农话的建议 。 相似文献