全文获取类型
收费全文 | 1608篇 |
免费 | 33篇 |
专业分类
电工技术 | 16篇 |
综合类 | 1篇 |
化学工业 | 133篇 |
金属工艺 | 6篇 |
机械仪表 | 18篇 |
建筑科学 | 18篇 |
矿业工程 | 1篇 |
能源动力 | 15篇 |
轻工业 | 72篇 |
水利工程 | 2篇 |
石油天然气 | 13篇 |
无线电 | 27篇 |
一般工业技术 | 105篇 |
冶金工业 | 1140篇 |
原子能技术 | 5篇 |
自动化技术 | 69篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 18篇 |
2021年 | 16篇 |
2020年 | 17篇 |
2019年 | 16篇 |
2018年 | 21篇 |
2017年 | 13篇 |
2016年 | 17篇 |
2015年 | 15篇 |
2014年 | 19篇 |
2013年 | 49篇 |
2012年 | 31篇 |
2011年 | 37篇 |
2010年 | 24篇 |
2009年 | 19篇 |
2008年 | 18篇 |
2007年 | 20篇 |
2006年 | 19篇 |
2005年 | 14篇 |
2004年 | 15篇 |
2003年 | 10篇 |
2002年 | 16篇 |
2001年 | 10篇 |
2000年 | 11篇 |
1999年 | 39篇 |
1998年 | 349篇 |
1997年 | 219篇 |
1996年 | 126篇 |
1995年 | 57篇 |
1994年 | 58篇 |
1993年 | 55篇 |
1992年 | 17篇 |
1991年 | 15篇 |
1990年 | 20篇 |
1989年 | 23篇 |
1988年 | 16篇 |
1987年 | 17篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1978年 | 8篇 |
1977年 | 24篇 |
1976年 | 69篇 |
1975年 | 4篇 |
1954年 | 1篇 |
排序方式: 共有1641条查询结果,搜索用时 31 毫秒
31.
Daniel Dominguez Gouvêa Cyro de A. Assis D. Muniz Gilson A. Pinto Alberto Avritzer Rosa Maria Meri Leão Edmundo de Souza e Silva Morganna Carmem Diniz Vittorio Cortellessa Luca Berardinelli Julius C. B. Leite Daniel Mossé Yuanfang Cai Michael Dalton Lucia Happe Anne Koziolek 《Software and Systems Modeling》2013,12(4):765-787
In this paper, we report on our experience with the application of validated models to assess performance, reliability, and adaptability of a complex mission critical system that is being developed to dynamically monitor and control the position of an oil-drilling platform. We present real-time modeling results that show that all tasks are schedulable. We performed stochastic analysis of the distribution of task execution time as a function of the number of system interfaces. We report on the variability of task execution times for the expected system configurations. In addition, we have executed a system library for an important task inside the performance model simulator. We report on the measured algorithm convergence as a function of the number of vessel thrusters. We have also studied the system architecture adaptability by comparing the documented system architecture and the implemented source code. We report on the adaptability findings and the recommendations we were able to provide to the system’s architect. Finally, we have developed models of hardware and software reliability. We report on hardware and software reliability results based on the evaluation of the system architecture. 相似文献
32.
In this paper, we introduce a multiscale operator which, together with some morphological tools, can be used to reconnect broken components of fingerprint images. This operator, which can be applied to both binary and gray-scale pictures, extracts the orientation field of an image by taking into account information parameters of sets of pixels in a given neighborhood and located in different directions. It has proved to be very robust to noise and outperforms the gradient- and directional mask-based methods, generally used for orientation field definition. Although we illustrate its application in the fingerprint domain, the approach described here can be easily extended to images whose components exhibit well-defined directional information. 相似文献
33.
To make health care more responsive to patient needs, insight into patient priorities is needed. A systematic literature review, using electronic and manual searches, was made of studies on patient priorities with regard to primary health care. Data-extraction was performed by two researchers, followed by systematic analyses of study features. 57 studies were included. The aspects of care and methods used showed a wide variation. Aspects most often included were "informativeness", "humaneness" and "competence/accuracy". Based on an analysis of 19 studies, the following aspects were seen by patients as most important in more than 50% of the studies that included them: "humaneness", "competence/accuracy", "patients' involvement in decisions", "time for care", "other aspects of availability/accessibility", "informativeness", "exploring patients' needs", "other aspects of relation and communication" and "availability of special services". 相似文献
34.
Diego Q. Leite Julio C. Duarte Luiz P. Neves Jauvane C. de Oliveira Gilson A. Giraldi 《Multimedia Tools and Applications》2017,76(20):20423-20455
This paper presents a real-time framework that combines depth data and infrared laser speckle pattern (ILSP) images, captured from a Kinect device, for static hand gesture recognition to interact with CAVE applications. At the startup of the system, background removal and hand position detection are performed using only the depth map. After that, tracking is started using the hand positions of the previous frames in order to seek for the hand centroid of the current one. The obtained point is used as a seed for a region growing algorithm to perform hand segmentation in the depth map. The result is a mask that will be used for hand segmentation in the ILSP frame sequence. Next, we apply motion restrictions for gesture spotting in order to mark each image as a ‘Gesture’ or ‘Non-Gesture’. The ILSP counterparts of the frames labeled as “Gesture” are enhanced by using mask subtraction, contrast stretching, median filter, and histogram equalization. The result is used as the input for the feature extraction using a scale invariant feature transform algorithm (SIFT), bag-of-visual-words construction and classification through a multi-class support vector machine (SVM) classifier. Finally, we build a grammar based on the hand gesture classes to convert the classification results in control commands for the CAVE application. The performed tests and comparisons show that the implemented plugin is an efficient solution. We achieve state-of-the-art recognition accuracy as well as efficient object manipulation in a virtual scene visualized in the CAVE. 相似文献
35.
In this work, we address the problem of transforming seismic reflection data into an intrinsic rock property model. Specifically, we present an application of a methodology that allows interpreters to obtain effective porosity 3D maps from post-stack 3D seismic amplitude data, using measured density and sonic well log data as constraints. In this methodology, a 3D acoustic impedance model is calculated from seismic reflection amplitudes by applying an L1-norm sparse-spike inversion algorithm in the time domain, followed by a recursive inversion performed in the frequency domain. A 3D low-frequency impedance model is estimated by kriging interpolation of impedance values calculated from well log data. This low-frequency model is added to the inversion result which otherwise provides only a relative numerical scale. To convert acoustic impedance into a single reservoir property, a feed-forward Neural Network (NN) is trained, validated and tested using gamma-ray and acoustic impedance values observed at the well log positions as input and effective porosity values as target. The trained NN is then applied for the whole reservoir volume in order to obtain a 3D effective porosity model. While the particular conclusions drawn from the results obtained in this work cannot be generalized, such results suggest that this workflow can be applied successfully as an aid in reservoir characterization, especially when there is a strong non-linear relationship between effective porosity and acoustic impedance. 相似文献
36.
Luiz Marcio Cysneiros Julio Cesar Sampaio do Prado Leite Jaime de Melo Sabat Neto 《Requirements Engineering》2001,6(2):97-115
The development of complex information systems calls for conceptual models that describe aspects beyond entities and activities.
In particular, recent research has pointed out that conceptual models need to model goals, in order to capture the intentions
which underlie complex situations within an organisational context. This paper focuses on one class of goals, namely non-functional
requirements (NFR), which need to be captured and analysed from the very early phases of the software development process.
The paper presents a framework for integrating NFRs into the ER and OO models. This framework has been validated by two case
studies, one of which is very large. The results of the case studies suggest that goal modelling during early phases can lead
to a more productive and complete modelling activity. 相似文献
37.
F Markwardt HP Kl?cking K Sedlarik J Perlewitz J Drawert J Hoffmann 《Canadian Metallurgical Quarterly》1976,35(2):193-203
The purpose of this investigation was to explore the feasibility of enhancing the electrochemical stability of dental amalgam restorations by a process of "selective interfacial amalgamation." If dental amalgam restorations can be selectively alloyed at the tooth-amalgam interface, to a minor thickness as compared with the dimensions of the bulk amalgam, so as to present a more electrochemically stable phase than psi2 to the oral environment, corrosion will be reduced and desirable qualities of existing amalgams can be utilized. It was found that selective interfacial amalgamation was indeed possible and that it could be readily accomplished using a silver suspension as a cavity liner. By then placing a conventional silver-tin amalgam according to ordinary dental techniques, mercury expressed during hand condensing reacted with the silver in the liner resulting in the formation of an integral amalgam restoration with the more noble psi1 phase adjacent to tooth structure. In vitro corrosion tests of samples so prepared exhibited corrosion resistance far superior to unlined control samples. 相似文献
38.
A group of 344 cervices, produced by conisation within a period of 5 1/2 years, were examined for specific effects of contraceptives. In half of all women, who used oral contraceptives, specific lesions such as "siebartige polypoide Hyperplasie" (cribriform polypoid hyperplasia) were found. The findings and their etiology and importance are discussed. 相似文献
39.
40.
Wide parabolic wells can be created by properly controlling the Al content during the growth of successive Ga1–xAlxAs thin layers. Under a tilted magnetic field these systems present interesting transport properties, which are associated to their composition dependent g-factor. We present an exact solution for the eigenstates of an electron gas inside such a quantum well. We calculate the renormalized cyclotron frequencies as functions of the angle of tilt, as well as the density of states, and the Fermi level. We discuss the conditions for the existence of spin-polarized charge. 相似文献