全文获取类型
收费全文 | 84706篇 |
免费 | 1068篇 |
国内免费 | 411篇 |
学科分类
工业技术 | 86185篇 |
出版年
2023年 | 28篇 |
2022年 | 59篇 |
2021年 | 110篇 |
2020年 | 87篇 |
2019年 | 77篇 |
2018年 | 14528篇 |
2017年 | 13434篇 |
2016年 | 10013篇 |
2015年 | 646篇 |
2014年 | 289篇 |
2013年 | 301篇 |
2012年 | 3188篇 |
2011年 | 9456篇 |
2010年 | 8321篇 |
2009年 | 5576篇 |
2008年 | 6800篇 |
2007年 | 7805篇 |
2006年 | 141篇 |
2005年 | 1228篇 |
2004年 | 1131篇 |
2003年 | 1181篇 |
2002年 | 537篇 |
2001年 | 104篇 |
2000年 | 184篇 |
1999年 | 60篇 |
1998年 | 74篇 |
1997年 | 40篇 |
1996年 | 51篇 |
1995年 | 21篇 |
1994年 | 21篇 |
1993年 | 12篇 |
1992年 | 14篇 |
1991年 | 25篇 |
1988年 | 12篇 |
1969年 | 24篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1964年 | 11篇 |
1963年 | 28篇 |
1962年 | 22篇 |
1961年 | 18篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Mobile Networks and Applications - Blockchain applications have continuously improved ever since its first debut on cryptocurrency. From then on, its uses have branched out from the financial... 相似文献
3.
Iqbal Ahmad Syed Mujtaba Shah Muhammad Nadeem Zafar Muhammad Naeem Ashiq Wei Tang Uzma Jabeen 《Ceramics International》2021,47(3):3760-3771
Ferrites are materials of interest due to their broad applications in high technological devices and a lot of research has been focused to synthesize new ferrites. In this regard, an effort has been devoted to synthesize spinel Pr–Ni co-substituted strontium ferrites with a nominal formula of Sr1-xPrxFe2-yNiyO4 (0.0 ≤ x ≤ 0.1, 0.0 ≤ y ≤ 1.0). The cubic structure of pure and Pr–Ni co-substituted strontium ferrite samples calcinated at 1073 K for 3 h has been confirmed through X-ray diffraction (XRD). Average sizes of crystallites (18–25 nm) have been estimated from XRD analysis and nanometer particle sizes of synthesized ferrites have been further verified by scanning electron microscopy (SEM). SEM results have also shown that particles are mostly agglomerated and all the samples possess porosity. It has been observed that at 298 K, the values of resistivity (ρ) increase, while that of AC conductivity, dielectric loss, and dielectric constants decrease with increasing amounts of Pr3+ and Ni2+ ions. The values of dielectric parameters initially decrease with frequency and later become constant and can be explained on the basis of dielectric polarization. Electrochemical impedance spectroscopy (EIS) studies show that the charge transport phenomenon in ferrite materials is mainly controlled via grain boundaries. Overall, synthesized ferrite materials own enhanced resistivity values in the range of 1.38 × 109–1.94 × 109 Ω cm and minimum dielectric losses, which makes them suitable candidates for high frequency devices applications. 相似文献
4.
AbstractIndustry 4.0 aims at providing a digital representation of a production landscape, but the challenges in building, maintaining, optimizing, and evolving digital models in inter-organizational production chains have not been identified yet in a systematic manner. In this paper, various Industry 4.0 research and technical challenges are addressed, and their present scenario is discussed. Moreover, in this article, the novel concept of developing experience-based virtual models of engineering entities, process, and the factory is presented. These models of production units, processes, and procedures are accomplished by virtual engineering object (VEO), virtual engineering process (VEP), and virtual engineering factory (VEF), using the knowledge representation technique of Decisional DNA. This blend of the virtual and physical domains permits monitoring of systems and analysis of data to foresee problems before they occur, develop new opportunities, prevent downtime, and even plan for the future by using simulations. Furthermore, the proposed virtual model concept not only has the capability of Query Processing and Data Integration for Industrial Data but also real-time visualization of data stream processing. 相似文献
5.
Izyan Najwa Mohd Norsham Siti Nor Atika Baharin Muggundha Raoov Syed Shahabuddin Jaroon Jakmunee Kavirajaa Pandian Sambasevam 《Polymer Engineering and Science》2020,60(12):3170-3182
A simple, cost-effective, and novel chemical sensor for ammonia (NH3) gas detection was developed from polyaniline (PANI)/quail eggshell (QES) composites. QES is a natural waste enriched in calcium carbonate. In this work, pure PANI was synthesized from chemical oxidation method and PANI/QES composites were prepared from physical mixing of QES with the synthesized PANI at different mass ratio. A series of complementary techniques including Fourier transform infrared and ultraviolet-visible spectrometers, scanning electron microscope with energy dispersive detection coupled with mapping, thermogravimetric analysis, and X-ray diffractometer were used to characterize the physicochemical and textural properties of the biocomposites. From the results, PANI/QES composite with a mass ratio of 1 exhibited the lowest NH3 detection limit of 5.24 ppm with a linear correlation coefficient (R2) of close to unity (0.9932) between the signal and NH3 gas concentration. As a whole, the PANI/QES biocomposites synthesized from this work exhibited excellent selectivity toward NH3 gas even in the presence of other gas impurities, such as acetone, ethanol, and hexane. For the sensor reusability, the PANI/QES biocomposites can be reused in the application of NH3 gas detection for at least 4 cycles. 相似文献
6.
Maktabdar Oghaz Mahdi Maarof Mohd Aizaini Rohani Mohd Foad Zainal Anazida Shaid Syed Zainudeen Mohd 《Neural computing & applications》2019,31(6):1835-1853
Neural Computing and Applications - Texture analysis is devised to address the weakness of color-based image segmentation models by considering the statistical and spatial relations among the group... 相似文献
7.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms. 相似文献
8.
A Synthetic Transcriptional Activator of Genes Associated with the Retina in Human Dermal Fibroblasts 下载免费PDF全文
9.
This paper presents an integrated passive damping approach in hybrid metal-CFRP parts for structural applications. In this concept a viscoelastic material is embedded in the joint zone of the hybrid component. To examine the connection strength single-lap-joint specimens were produced and tested and the influence of the used material combinations, different surface structures, and different process parameters i.e. the moment of cross-linking were evaluated. Afterwards, the metal-CFRP hybrids were tested in quasi-static tests to assess their connection strength and failure behaviour. Dynamic cyclic tensile tests with step-wise increased loading conditions were performed to determine the specimens damping behaviour and to estimate their fatigue performance. Finally, these results are compared to a state of the art metal-CFRP hybrid with rivets connecting both materials. 相似文献
10.
Husain Syed Sameed Ong Eng-Jon Bober Miroslaw 《International Journal of Computer Vision》2021,129(5):1432-1450
International Journal of Computer Vision - We propose a novel CNN architecture called ACTNET for robust instance image retrieval from large-scale datasets. Our key innovation is a learnable... 相似文献