全文获取类型
收费全文 | 360047篇 |
免费 | 35868篇 |
国内免费 | 22110篇 |
专业分类
电工技术 | 52987篇 |
技术理论 | 31篇 |
综合类 | 36432篇 |
化学工业 | 25783篇 |
金属工艺 | 11414篇 |
机械仪表 | 26490篇 |
建筑科学 | 25924篇 |
矿业工程 | 12802篇 |
能源动力 | 10602篇 |
轻工业 | 12676篇 |
水利工程 | 9047篇 |
石油天然气 | 11781篇 |
武器工业 | 5203篇 |
无线电 | 41023篇 |
一般工业技术 | 21040篇 |
冶金工业 | 12619篇 |
原子能技术 | 3824篇 |
自动化技术 | 98347篇 |
出版年
2024年 | 735篇 |
2023年 | 3989篇 |
2022年 | 7861篇 |
2021年 | 11539篇 |
2020年 | 10054篇 |
2019年 | 7910篇 |
2018年 | 7493篇 |
2017年 | 10421篇 |
2016年 | 12881篇 |
2015年 | 14888篇 |
2014年 | 23928篇 |
2013年 | 20953篇 |
2012年 | 26063篇 |
2011年 | 27157篇 |
2010年 | 20930篇 |
2009年 | 20763篇 |
2008年 | 21572篇 |
2007年 | 27254篇 |
2006年 | 24673篇 |
2005年 | 21877篇 |
2004年 | 17480篇 |
2003年 | 15790篇 |
2002年 | 12040篇 |
2001年 | 9717篇 |
2000年 | 8149篇 |
1999年 | 6253篇 |
1998年 | 4673篇 |
1997年 | 3835篇 |
1996年 | 3308篇 |
1995年 | 2844篇 |
1994年 | 2359篇 |
1993年 | 1666篇 |
1992年 | 1320篇 |
1991年 | 1011篇 |
1990年 | 846篇 |
1989年 | 706篇 |
1988年 | 505篇 |
1987年 | 343篇 |
1986年 | 251篇 |
1985年 | 288篇 |
1984年 | 241篇 |
1983年 | 233篇 |
1982年 | 179篇 |
1981年 | 144篇 |
1980年 | 127篇 |
1979年 | 99篇 |
1978年 | 56篇 |
1977年 | 61篇 |
1962年 | 74篇 |
1959年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Lauren Folk Kiara Gonzales John Gales Michael Kinsey Elisabetta Carattin Tim Young 《火与材料》2020,44(4):585-606
Practitioners are continuing to develop egress modelling software for the design of the built environment. These models require data about human behaviour and factors for calibration, validation and verification. This study aims to address the specific data and knowledge gap: emergency egress of the elderly. Such data are difficult to collect given privacy and consent concerns, with strong relationships generally being required between residences and researchers. Through the observation of nine fire drills at six Canadian long-term care (LTC) and retirement homes, specific evacuation actions and behaviour were observed for 37 staff members and information about the evacuation of 56 residents was collected. These drills demonstrated that emergency egress in LTC and retirement homes is highly staff dependent with 72% of residents recorded requiring full assistance at all stages of movement in evacuation, and that the type of announced/unannounced drill and level of resident care will affect the type of data collected. The development of travel speed and pre-movement is discussed subject to limitation with qualitative behavioural insights of residents that were observed. This study provides valuable methodological discussion on how to conduct behavioural studies in similar highly restricted research environments. Specific attention is given to understanding the considerations that must be made when using fire drills as data sources, and the impact that these can have on using such data for modelling. This study may inform the initial setup and programming of evacuation models from an actions and behavioural perspectives of staff members and residents. 相似文献
73.
模拟量模块采用RS485通讯网路,将分散的现场数据点的模拟量经AD变换传输到主机或由PC控制远程主站点。模拟量模块具有计量数据采集、测量数据采集、设备开关状态采集和对外逻辑控制等多项功能,主要用作各种测控终端的数据采集、控制和显示设备,适用于各行业的自动化、信息化系统。本文介绍了一种模拟量模块的应用。 相似文献
74.
75.
76.
AbstractData mining techniques have been successfully utilized in different applications of significant fields, including medical research. With the wealth of data available within the health-care systems, there is a lack of practical analysis tools to discover hidden relationships and trends in data. The complexity of medical data that is unfavorable for most models is a considerable challenge in prediction. The ability of a model to perform accurately and efficiently in disease diagnosis is extremely significant. Thus, the model must be selected to fit the data better, such that the learning from previous data is most efficient, and the diagnosis of the disease is highly accurate. This work is motivated by the limited number of regression analysis tools for multivariate counts in the literature. We propose two regression models for count data based on flexible distributions, namely, the multinomial Beta-Liouville and multinomial scaled Dirichlet, and evaluated the proposed models in the problem of disease diagnosis. The performance is evaluated based on the accuracy of the prediction which depends on the nature and complexity of the dataset. Our results show the efficiency of the two proposed regression models where the prediction performance of both models is competitive to other previously used regression models for count data and to the best results in the literature. 相似文献
77.
Traditionally, in supervised machine learning, (a significant) part of the available data (usually 50%-80%) is used for training and the rest—for validation. In many problems, however, the data are highly imbalanced in regard to different classes or does not have good coverage of the feasible data space which, in turn, creates problems in validation and usage phase. In this paper, we propose a technique for synthesizing feasible and likely data to help balance the classes as well as to boost the performance in terms of confusion matrix as well as overall. The idea, in a nutshell, is to synthesize data samples in close vicinity to the actual data samples specifically for the less represented (minority) classes. This has also implications to the so-called fairness of machine learning. In this paper, we propose a specific method for synthesizing data in a way to balance the classes and boost the performance, especially of the minority classes. It is generic and can be applied to different base algorithms, for example, support vector machines, k-nearest neighbour classifiers deep neural, rule-based classifiers, decision trees, and so forth. The results demonstrated that (a) a significantly more balanced (and fair) classification results can be achieved and (b) that the overall performance as well as the performance per class measured by confusion matrix can be boosted. In addition, this approach can be very valuable for the cases when the number of actual available labelled data is small which itself is one of the problems of the contemporary machine learning. 相似文献
78.
By leveraging the secret data coding using the remainder storage based exploiting modification direction (RSBEMD), and the pixel change operation recording based on multi-segment left and right histogram shifting, a novel reversible data hiding (RHD) scheme is proposed in this paper. The secret data are first encoded by some specific pixel change operations to the pixels in groups. After that, multi-segment left and right histogram shifting based on threshold manipulation is implemented for recording the pixel change operations. Furthermore, a multiple embedding policy based on chess board prediction (CBP) and threshold manipulation is put forward, and the threshold can be adjusted to achieve adaptive data hiding. Experimental results and analysis show that it is reversible and can achieve good performance in capacity and imperceptibility compared with the existing methods. 相似文献
79.
Perfluorocarbon gas is widely used in the semiconductor industry. However, perfluorocarbon has a
negative effect on the global environment owing to its high global warming potential (GWP) value.
An alternative solution is essential. Therefore, we evaluated the possibility of replacing conventional
perfluorocarbon etching gases such as CHF3 with C6F12O, which has a low GWP and is in a liquid
state at room temperature. In this study, silicon oxynitride (SiON) films were plasma-etched using
inductively coupled CF4 +C6F12O+O2 mixed plasmas. Subsequently, the etching characteristics
of the film, such as etching rate, etching profile, selectivity over Si, and photoresist, were investigated.
A double Langmuir probe was used and optical emission spectroscopy was performed for plasma
diagnostics. In addition, a contact angle goniometer and x-ray photoelectron spectroscope were used
to confirm the change in the surface properties of the etched SiON film surface. Consequently, the
etching characteristics of the C6F12O mixed plasma exhibited a lower etching rate, higher SiON/Si
selectivity, lower plasma damage, and more vertical etched profiles than the conventional CHF3 mixed plasma. In addition, the C6F12O gas can be recovered in the liquid state, thereby decreasing
global warming. These results confirmed that the C6F12O precursor can sufficiently replace the
conventional etching gas. 相似文献
80.
Hot-dip galvanizing is a standard technology to produce coated steel strips. The primary objective of the galvanizing process is to establish a homogeneous zinc layer with a defined thickness. One condition to achieve this objective is a uniform transverse distance between the strip and the gas wiping dies, which blow off excessive liquid zinc. Therefore, a flat strip profile at the gas wiping dies is required. However, strips processed in such plants often exhibit residual curvatures which entail unknown flatness defects of the strip. Such flatness defects cause non-uniform air gaps and hence an inhomogeneous zinc coating thickness. Modern hot-dip galvanizing lines often use electromagnets to control the transverse strip profile near the gas wiping dies. Typically, the control algorithms ensure a flat strip profile at the electromagnets because the sensors for the transverse strip displacement are also located at this position and it is unfeasible to mount displacement sensors directly at the gas wiping dies. This brings along that in general a flatness defect remains at the gas wiping dies, which in turn entails a suboptimal coating.In this paper, a model-based method for a feedforward control of the strip profile at the position of the gas wiping dies is developed. This method is based on a plate model of the axially moving strip that takes into account the flatness defects in the strip. First, an estimator of the flatness defects is developed and validated for various test strips and settings of the plant. Using the validated mathematical model, a simulation study is performed to compare the state-of-the-art control approach (flat strip profile at the electromagnets) with the optimization-based feedforward controller (flat strip profile at the gas wiping dies) proposed in this paper. Moreover, the influence of the distance between the gas wiping dies and the electromagnets is investigated in detail. 相似文献