全文获取类型
收费全文 | 2241篇 |
免费 | 153篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 29篇 |
综合类 | 1篇 |
化学工业 | 495篇 |
金属工艺 | 44篇 |
机械仪表 | 76篇 |
建筑科学 | 119篇 |
矿业工程 | 2篇 |
能源动力 | 170篇 |
轻工业 | 390篇 |
水利工程 | 15篇 |
石油天然气 | 9篇 |
无线电 | 137篇 |
一般工业技术 | 455篇 |
冶金工业 | 76篇 |
原子能技术 | 19篇 |
自动化技术 | 361篇 |
出版年
2024年 | 8篇 |
2023年 | 23篇 |
2022年 | 56篇 |
2021年 | 97篇 |
2020年 | 92篇 |
2019年 | 97篇 |
2018年 | 112篇 |
2017年 | 95篇 |
2016年 | 129篇 |
2015年 | 80篇 |
2014年 | 104篇 |
2013年 | 208篇 |
2012年 | 137篇 |
2011年 | 183篇 |
2010年 | 124篇 |
2009年 | 156篇 |
2008年 | 134篇 |
2007年 | 112篇 |
2006年 | 80篇 |
2005年 | 65篇 |
2004年 | 55篇 |
2003年 | 40篇 |
2002年 | 42篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 27篇 |
1998年 | 25篇 |
1997年 | 13篇 |
1996年 | 18篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1970年 | 2篇 |
排序方式: 共有2398条查询结果,搜索用时 15 毫秒
991.
The effect of high temperature on the mechanical properties of high-strength mortar was investigated. Specimens were heated up to elevated temperatures (300, 600, 900 °C ) without loading. After being exposed to these oven temperatures, the residual modulus of elasticity, flexural strength and compressive strength of the specimens were determined. The effect of the rate of heating, duration of exposure to maximum temperature and the role of graphite powder, which is known as a high-temperature refractory material on the behavior of the mortar specimens, were observed. Temperatures up to 600 °C resulted in considerable losses in mechanical properties, and at 900 °C, specimens lost almost all of their strength. Higher rate of heating and exposure to the maximum temperature for a shorter period of time resulted in higher residual properties. The useful effect of graphite addition on the residual compressive strength and modulus of elasticity of the mortar specimens as percentages of initial values for each of the heating cycles are clearly observed. 相似文献
992.
Mehmet Akar Kumpati S. Narendra 《International Journal of Adaptive Control and Signal Processing》2002,16(10):729-751
Necessary and sufficient conditions for the existence of a common quadratic Lyapunov function (CQLF) are given for two second‐order linear time‐invariant discrete‐time systems. These conditions are later extended to an arbitrary number of systems. The conditions are readily verifiable both analytically and graphically. The paper also provides a constructive procedure for computing a CQLF when it exists. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
993.
Ehmen H Haesner M Steinke I Dorn M Gövercin M Steinhagen-Thiessen E 《Applied ergonomics》2012,43(3):582-587
In the area of product design and usability, most products are developed for the mass-market by technically oriented designers and developers for use by persons who themselves are also technically adept by today's standards. The demands of older people are commonly not given sufficient consideration within the early developmental process. In the present study, the usability and acceptability of four different devices meant to be worn for the measurement of heart rate or ECG were analyzed on the basis of qualitative subjective user ratings and structured interviews of twelve older participants. The data suggest that there was a relatively high acceptance concerning these belts by older adults but none of the four harnesses was completely usable. Especially problematic to the point of limiting satisfaction among older subjects were problems encountered while adjusting the length of the belt and/or closing the locking mechanism. The two devices intended for dedicated heart rate recording yielded the highest user ratings for design, and were clearly preferred for extended wearing time. Yet for all the devices participants identified several important deficiencies in their design, as well as suggestions for improvement. We conclude that the creation of an acceptable monitoring device for older persons requires designers and developers to consider the special demands and abilities of the target group. 相似文献
994.
In this study, we propose a knowledge-based approach for detection and isolation of sensor faults in fault tolerant control (FTC) of the three-tank system. Farthest first traversal algorithm (FFTA) of data mining is used first-time for the classification of faults in an FTC system. The sliding window is used to detect signal changes, which contain possible transients due to faults. The variance-changing ratio is calculated to extract the features of the sensor signal in each window. Then, FFTA is utilized for the isolation of sensor faults. In order to demonstrate the efficiency of the proposed method, seven types of artificial faults were applied to closed-loop fault tolerant control system in certain periods. All faults were detected and isolated immediately after they occurred. Moreover, fault isolation was achieved when multiple faults occurred simultaneously. 相似文献
995.
We describe the design of a system for fast and reliable HTTP service which we call Web++. Web++ achieves high reliability
by dynamically replicating web data among multiple web servers. Web++ selects the available server that is expected to provide
the fastest response time. Furthermore, Web++ guarantees data delivery given that at least one server containing the requested
data is available. After detecting a server failure, Web++ client requests are satisfied transparently to the user by another
server. Furthermore, the Web++ architecture is flexible enough for implementing additional performance optimizations. We describe
implementation of one such optimization, batch resource transmission, whereby all resources embedded in an HTML page that
are not cached by the client are sent to the client in a single response. Web++ is built on top of the standard HTTP protocol
and does not require any changes either in existing web browsers or the installation of any software on the client side. In
particular, Web++ clients are dynamically downloaded to web browsers as signed Java applets. We implemented a Web++ prototype;
performance experiments indicate that the Web++ system with 3 servers improves the response time perceived by clients on average
by 36.6%, and in many cases by as much as 59%, when compared with the current web performance. In addition, we show that batch
resource transmission can improve the response time on average by 39% for clients with fast network connections and 21% for
the clients with 56 Kb modem connections.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
996.
In this paper, Adaptive Neural Fuzzy Inference System (ANFIS) and Multiple Linear Regression (MLR) models are discussed to determine peak pressure load measurements of the 0, 0.2, 0.4 and 0.6% glass fibers (by weight) reinforced concrete pipes having 200, 300, 400, 500 and 600 mm diameters. For comparing the ANFIS, MLR and experimental results, determination coefficient (R2), root mean square error (RMSE) and standard error of estimates (SEE) statistics were used as evaluation criteria. It is concluded that ANFIS and MLR are practical methods for predicting the peak pressure load (PPL) values of the concrete pipes containing glass fibers and PPL values can be predicted using ANFIS and MLR without attempting any experiments in a quite short period of time with tiny error rates. Furthermore ANFIS model has the predicting potential better than MLR. 相似文献
997.
Estimation of global solar radiation using ANN over Turkey 总被引:1,自引:0,他引:1
The main objective of the present study is to develop an artificial neural network (ANN) model based on multi-nonlinear regression (MNLR) method for estimating the monthly mean daily sum global solar radiation at any place of Turkey. For this purpose, the meteorological data of 31 stations spread over Turkey along the years 2000-2006 were used as training (27 stations) and testing (4 stations) data. Firstly, all independent variables (latitude, longitude, altitude, month, monthly minimum atmospheric temperature, maximum atmospheric temperature, mean atmospheric temperature, soil temperature, relative humidity, wind speed, rainfall, atmospheric pressure, vapor pressure, cloudiness and sunshine duration) were added to the Enter regression model. Then, the Stepwise MNLR method was applied to determine the most suitable independent (input) variables. With the use of these input variables, the results obtained by the ANN model were compared with the actual data, and error values were found within acceptable limits. The mean absolute percentage error (MAPE) was found to be 5.34% and correlation coefficient (R) value was obtained to be about 0.9936 for the testing data set. 相似文献
998.
Sumeyye Bayrakdar Ibrahim Yucedag Mehmet Simsek Ibrahim Alper Dogru 《International Journal of Communication Systems》2020,33(11)
As social networks are getting more and more popular day by day, large numbers of users becoming constantly active social network users. In this way, there is a huge amount of data produced by users in social networks. While social networking sites and dynamic applications of these sites are actively used by people, social network analysis is also receiving an increasing interest. Moreover, semantic understanding of text, image, and video shared in a social network has been a significant topic in the network analysis research. To the best of the author's knowledge, there has not been any comprehensive survey of social networks, including semantic analysis. In this survey, we have reviewed over 200 contributions in the field, most of which appeared in recent years. This paper not only aims to provide a comprehensive survey of the research and application of social network analysis based on semantic analysis but also summarizes the state‐of‐the‐art techniques for analyzing social media data. First of all, in this paper, social networks, basic concepts, and components related to social network analysis were examined. Second, semantic analysis methods for text, image, and video in social networks are explained, and various studies about these topics are examined in the literature. Then, the emerging approaches in social network analysis research, especially in semantic social network analysis, are discussed. Finally, the trending topics and applications for future directions of the research are emphasized; the information on what kind of studies may be realized in this area is given. 相似文献
999.
KangJu Lee Yumeng Xue Junmin Lee Han‐Jun Kim Yaowen Liu Peyton Tebon Einollah Sarikhani Wujin Sun Shiming Zhang Reihaneh Haghniaz Betül elebi‐Saltik Xingwu Zhou Serge Ostrovidov Samad Ahadian Nureddin Ashammakhi Mehmet R. Dokmeci Ali Khademhosseini 《Advanced functional materials》2020,30(23)
Mesenchymal stem cells (MSCs) have been widely used for regenerative therapy. In most current clinical applications, MSCs are delivered by injection but face significant issues with cell viability and penetration into the target tissue due to a limited migration capacity. Some therapies have attempted to improve MSC stability by their encapsulation within biomaterials; however, these treatments still require an enormous number of cells to achieve therapeutic efficacy due to low efficiency. Additionally, while local injection allows for targeted delivery, injections with conventional syringes are highly invasive. Due to the challenges associated with stem cell delivery, a local and minimally invasive approach with high efficiency and improved cell viability is highly desired. In this study, a detachable hybrid microneedle depot (d‐HMND) for cell delivery is presented. The system consists of an array of microneedles with an outer poly(lactic‐co‐glycolic) acid shell and an internal gelatin methacryloyl (GelMA)‐MSC mixture (GMM). The GMM is characterized and optimized for cell viability and mechanical strength of the d‐HMND required to penetrate mouse skin tissue is also determined. MSC viability and function within the d‐HMND is characterized in vitro and the regenerative efficacy of the d‐HMND is demonstrated in vivo using a mouse skin wound model. 相似文献
1000.
A new student performance analysing system using knowledge discovery in higher educational databases
Knowledge discovery is a wide ranged process including data mining, which is used to find out meaningful and useful patterns in large amounts of data. In order to explore the factors having impact on the success of university students, knowledge discovery software, called MUSKUP, has been developed and tested on student data. In this system a decision tree classification is employed as a data mining technique. With this software system all the tasks involved in the knowledge discovery process are kept together. The advantage of this approach is to have access to all the functionalities of SQL server and Analysis Services through single software. The study was carried out on the data from university students. According to results of the study, the types of registration to the university and the income levels of the students’ family were found to be associated with student success. 相似文献