全文获取类型
收费全文 | 27495篇 |
免费 | 902篇 |
国内免费 | 776篇 |
专业分类
电工技术 | 1734篇 |
技术理论 | 1篇 |
综合类 | 1303篇 |
化学工业 | 2779篇 |
金属工艺 | 1705篇 |
机械仪表 | 3414篇 |
建筑科学 | 1462篇 |
矿业工程 | 636篇 |
能源动力 | 2239篇 |
轻工业 | 1147篇 |
水利工程 | 502篇 |
石油天然气 | 829篇 |
武器工业 | 212篇 |
无线电 | 1945篇 |
一般工业技术 | 1579篇 |
冶金工业 | 1068篇 |
原子能技术 | 624篇 |
自动化技术 | 5994篇 |
出版年
2024年 | 23篇 |
2023年 | 202篇 |
2022年 | 341篇 |
2021年 | 460篇 |
2020年 | 473篇 |
2019年 | 355篇 |
2018年 | 357篇 |
2017年 | 460篇 |
2016年 | 540篇 |
2015年 | 632篇 |
2014年 | 1343篇 |
2013年 | 1352篇 |
2012年 | 1534篇 |
2011年 | 2142篇 |
2010年 | 1526篇 |
2009年 | 1445篇 |
2008年 | 1354篇 |
2007年 | 1886篇 |
2006年 | 1783篇 |
2005年 | 1713篇 |
2004年 | 1405篇 |
2003年 | 1343篇 |
2002年 | 1109篇 |
2001年 | 800篇 |
2000年 | 682篇 |
1999年 | 756篇 |
1998年 | 613篇 |
1997年 | 490篇 |
1996年 | 437篇 |
1995年 | 374篇 |
1994年 | 266篇 |
1993年 | 222篇 |
1992年 | 152篇 |
1991年 | 117篇 |
1990年 | 106篇 |
1989年 | 82篇 |
1988年 | 82篇 |
1987年 | 37篇 |
1986年 | 24篇 |
1985年 | 37篇 |
1984年 | 31篇 |
1983年 | 12篇 |
1982年 | 20篇 |
1981年 | 13篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 13篇 |
1977年 | 6篇 |
1975年 | 3篇 |
1964年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
In polyolefin processes the melt index (MI) is the most important control variable indicating product quality. Because of
the difficulty in the on-line measurement of MI, a lot of MI estimation and correlation methods have been proposed. In this
work a new dynamic MI estimation scheme is developed based on system identification techniques. The empirical MI estimation
equation proposed in the present study is derived from the 1
st
-order dynamic models. Effectiveness of the present estimation scheme was illustrated by numerical simulations based on plant
operation data including grade change operations in high density polyethylene (HDPE) processes. From the comparisons with
other estimation methods it was found that the proposed estimation scheme showed better performance in MI predictions. The
virtual sensor model developed based on the estimation scheme was combined with the virtual on-line analyzer (VOA) to give
a quality control system to be implemented in the actual HDPE plant. From the application of the present control system, significant
reduction of transition time and the amount of off-spec during grade changes was achieved 相似文献
52.
C. Athanassiou G. Pekridis N. Kaklidis K. Kalimeri S. Vartzoka G. Marnellos 《International Journal of Hydrogen Energy》2007
In the present work, the prospects and trends of solid electrolyte membrane reactors (SEMRs) towards hydrogen production, are discussed. Initially, an overview of the principles, the properties and the techniques related to the usage of the SEMRs, are presented. In the following, a literature survey covering earlier and recent developments of the various methods (e.g. reforming or partial oxidation or dehydrogenation of hydrocarbons, steam electrolysis) employed in the SEMRs for the production of hydrogen, is performed. Finally, the current status of this research field is analyzed and future research topics are proposed. 相似文献
53.
We measured the sensitivities of five hot-cathode ionization gauges for ambient laboratory temperatures between 23 and 31 °C. All of the ionization gauges exhibited very similar behavior, and the sensitivity could be adequately modeled with a linear function of temperature. The slopes of the fits were smaller than one would expect due to changes in the calibration chamber number density. The thermal transpiration effect, due to local heating of the gauge structures, can account for this, and a characteristic gauge tube temperature can be inferred from the temperature dependence of the sensitivity. A recent comparison of the high vacuum standards of several National Metrology Institutes (NMIs) was performed over the range of 10−6-10−3 Pa using hot-cathode and spinning rotor gauges as transfer standards. Among the participants, laboratory temperatures varied by as much as 5 °C. It is necessary to know how laboratory temperature affects the sensitivity of the hot-cathode transfer standards (spinning rotor gauges explicitly account for the gas temperature) so that individual laboratory results can be corrected to a common temperature. 相似文献
54.
FloorControl是在大型网络实时交互平台下对共享资源进行控制管理的一项技术。FloorControl的概念分为机制和策略两个部分,协议属于机制,而策略则是具体的控制办法。本文着重介绍了在共享应用中使用FloorControl的技术要点,分析了目前常用的FloorControl协议,并给出了若干具体的FloorControl策略,这些策略的共同作用结果是具有公平、灵活和协同性。 相似文献
55.
57.
国内3G网络共享问题之研究 总被引:2,自引:0,他引:2
随着国内3G时代的来临,3G网络共享问题越来越受到人们的关注。本文结合国内移动通信的现状,着重分析了3G网络共享的模式及经济效益,论述了3G网络共享的相应策略。 相似文献
58.
针对用单片机控制机电一体化设备必须解决的抗干扰问题,提出了一些对策,旨在提高控制系统的自适应能力,从而做到可靠运行。 相似文献
59.
Controllability of One Spin and Two Interacting Spins 总被引:1,自引:0,他引:1
Mathematics of Control, Signals, and Systems - ?We consider the problem of steering control for the systems of one spin ½ particle and two interacting spin ½ particles in an... 相似文献
60.
A good understanding of environmental effects on structural modal properties is essential for reliable performance of vibration-based damage diagnosis methods. In this paper, a method of combining principal component analysis (PCA) and support vector regression (SVR) technique is proposed for modeling temperature-caused variability of modal frequencies for structures instrumented with long-term monitoring systems. PCA is first applied to extract principal components from the measured temperatures for dimensionality reduction. The predominant feature vectors in conjunction with the measured modal frequencies are then fed into a support vector algorithm to formulate regression models that may take into account thermal inertia effect. The research is focused on proper selection of the hyperparameters to obtain SVR models with good generalization performance. A grid search method with cross validation and a heuristic method are utilized for determining the optimal values of SVR hyperparameters. The proposed method is compared with the method directly using measurement data to train SVR models and the multivariate linear regression (MLR) method through the use of long-term measurement data from a cable-stayed bridge. It is shown that PCA-compressed features make the training and validation of SVR models more efficient in both model accuracy and computational costs, and the formulated SVR model performs much better than the MLR model in generalization performance. When continuously measured data is available, the SVR model formulated taking into account thermal inertia effect can achieve more accurate prediction than that without considering thermal inertia effect. 相似文献