全文获取类型
收费全文 | 18722篇 |
免费 | 1136篇 |
国内免费 | 514篇 |
专业分类
电工技术 | 1620篇 |
综合类 | 1366篇 |
化学工业 | 1523篇 |
金属工艺 | 864篇 |
机械仪表 | 2802篇 |
建筑科学 | 2408篇 |
矿业工程 | 995篇 |
能源动力 | 1950篇 |
轻工业 | 332篇 |
水利工程 | 669篇 |
石油天然气 | 1958篇 |
武器工业 | 63篇 |
无线电 | 856篇 |
一般工业技术 | 1791篇 |
冶金工业 | 514篇 |
原子能技术 | 215篇 |
自动化技术 | 446篇 |
出版年
2024年 | 59篇 |
2023年 | 162篇 |
2022年 | 340篇 |
2021年 | 416篇 |
2020年 | 447篇 |
2019年 | 263篇 |
2018年 | 290篇 |
2017年 | 346篇 |
2016年 | 478篇 |
2015年 | 584篇 |
2014年 | 1166篇 |
2013年 | 990篇 |
2012年 | 1407篇 |
2011年 | 1563篇 |
2010年 | 1128篇 |
2009年 | 1133篇 |
2008年 | 967篇 |
2007年 | 1338篇 |
2006年 | 1227篇 |
2005年 | 1038篇 |
2004年 | 919篇 |
2003年 | 845篇 |
2002年 | 705篇 |
2001年 | 512篇 |
2000年 | 472篇 |
1999年 | 325篇 |
1998年 | 267篇 |
1997年 | 219篇 |
1996年 | 207篇 |
1995年 | 174篇 |
1994年 | 101篇 |
1993年 | 65篇 |
1992年 | 37篇 |
1991年 | 33篇 |
1990年 | 24篇 |
1989年 | 29篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 2篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1982年 | 17篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
随着我国经济的迅速发展,能源消耗不断增加,节约能源、降低能源消耗势在必行,余热利用是节约能源的一个重要环节,冶金行业高炉冲渣水作为采暖热媒可以节约大量能源。 相似文献
12.
13.
14.
Because the oceanaut plays a significant role in safety and capability during manned deep-diving scientific tasks, preventing oceanaut performance decline is of paramount importance. However, the factors responsible for oceanaut performance are almost entirely unexplored. To address the preceding issues, a quantitative method of fuzzy integrated Bayesian network (FIBN) was modeled within the limits of oceanaut operating procedures. To quantify the probabilities of the influencing factors, the probability of each node in the FIBN was calculated using integrated expert judgement, fuzzy logic theory, and Bayesian network. By considering a total of 28 factors related to oceanaut performance in the “Jiaolong” manned submersible, this study found that difficult sampling, long sampling times, cabin equipment failure, oceanaut physical decline, and declining decision-making ability are important factors that affect oceanaut performance. The FIBN proposed in our study fused the qualitative and quantitative methods and can be developed into a versatile tool for analysis of comprehensive systems that contain both static and dynamic factors.Relevance to industryThe results provide a powerful basis for the design of manned submersible and assignment of tasks to oceanauts, while the fuzzy integrated Bayesian network (FIBN) method proposed can be effectively applied to various quantitative assessment fields which direct researchers to deal with analysis problems of complex systems. 相似文献
15.
16.
Fault detection and isolation in rotating machinery is very important from an industrial viewpoint as it can help in maintenance activities and significantly reduce the down-time of the machine, resulting in major cost savings. Traditional methods have been found to be not very accurate. Soft computing based methods are now being increasingly employed for the purpose. The proposed method is based on a genetic programming technique which is known as gene expression programming (GEP). GEP is somewhat a new member of the genetic programming family. The main objective of this paper is to compare the classification accuracy of the proposed evolutionary computing based method with other pattern classification approaches such as support vector machine (SVM), Wavelet-GEP, and proximal support vector machine (PSVM). For this purpose, six states viz., normal, bearing fault, impeller fault, seal fault, impeller and bearing fault together, cavitation are simulated on centrifugal pump. Decision tree algorithm is used to select the features. The results obtained using GEP is compared with the performance of Wavelet-GEP, support vector machine (SVM) and proximal support vector machine (PSVM) based classifiers. It is observed that both GEP and SVM equally outperform the other two classifiers (PSVM and Wavelet-GEP) considered in the present study. 相似文献
17.
18.
《Expert systems with applications》2014,41(2):622-634
This paper presents a low power and low phase noise CMOS integer-N frequency synthesizer based on the charge-pump Phase Locked Loop (PLL) topology. The frequency synthesizer can be used for IEEE 802.16 unlicensed band of WiMAX (World Interoperability for Microwave Access). The operation frequency of the proposed design is ranged from 5.13 to 5.22 GHz. The proposed Voltage-Controlled Oscillator (VCO) achieves low power consumption and low phase noise. The high speed divider is implemented by an optimal extended true single phase clock (E-TSPC) prescaler. It can achieve higher operating frequency and lower power consumption. A new frequency divider is also proposed to eliminate the hardware overhead of the S counter in the conventional programmable divider. The proposed frequency synthesizer consists of a phase-frequency detector (PFD), a charge pump, a low-pass loop filter, a VCO, and a frequency divider. The simulated phase noise of the proposed VCO is −121.6 dBc/Hz at 1 MHz offset from the carrier frequency. The proposed frequency synthesizer consumes 13.1 mW. The chip with an area of 1.048 × 1.076 mm2 is fabricated in a TSMC 0.18 μm CMOS 1P6M technology process. 相似文献
19.
20.
王会云 《煤炭加工与综合利用》2004,(1):13-15
辛置选煤厂针对原煤煤质变化后的特点 ,采用有压给料三产品重介旋流器为核心的高效选煤工艺系统分选 5 0~ 0mm原煤 ;对旋流器一段及二段中心管的直径和插入深度、二段底流口的直径等进行了优化调整 ,同时调整了介质泵的工作频率及悬浮液密度等参数 ,取得了分选效率高、产品质量稳定等显著效果 相似文献