全文获取类型
收费全文 | 14437篇 |
免费 | 670篇 |
国内免费 | 516篇 |
专业分类
电工技术 | 353篇 |
综合类 | 375篇 |
化学工业 | 1297篇 |
金属工艺 | 293篇 |
机械仪表 | 405篇 |
建筑科学 | 243篇 |
矿业工程 | 56篇 |
能源动力 | 882篇 |
轻工业 | 195篇 |
水利工程 | 46篇 |
石油天然气 | 160篇 |
武器工业 | 15篇 |
无线电 | 2355篇 |
一般工业技术 | 1290篇 |
冶金工业 | 72篇 |
原子能技术 | 52篇 |
自动化技术 | 7534篇 |
出版年
2024年 | 20篇 |
2023年 | 729篇 |
2022年 | 580篇 |
2021年 | 658篇 |
2020年 | 766篇 |
2019年 | 676篇 |
2018年 | 596篇 |
2017年 | 1299篇 |
2016年 | 1299篇 |
2015年 | 1034篇 |
2014年 | 1406篇 |
2013年 | 843篇 |
2012年 | 742篇 |
2011年 | 725篇 |
2010年 | 593篇 |
2009年 | 704篇 |
2008年 | 363篇 |
2007年 | 539篇 |
2006年 | 512篇 |
2005年 | 307篇 |
2004年 | 155篇 |
2003年 | 188篇 |
2002年 | 249篇 |
2001年 | 209篇 |
2000年 | 133篇 |
1999年 | 180篇 |
1998年 | 62篇 |
1997年 | 16篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
1.
In the recent advancements in image and video analysis, the detection of salient regions in the image becomes the initial step. This plays a crucial role in deciding the performance of such algorithms. In this work, a Multi-Resolution Feature Extraction (MRFE) technique that makes use of Discrete Wavelet Convolutional Neural Network (DWCNN) for generating features is employed. An Enhanced Feature Extraction (EFE) module extracts additional features from the high level features of the DWCNN, which are used to frame both channel as well as spatial attention models for yielding contextual attention maps. A new hybrid loss function is also proposed, which is a combination of Balanced Cross Entropy (BCE) loss and Edge based Structural Similarity (ESSIM) loss that effectively identifies and segments the salient regions with clear boundaries. The method is tested exhaustively with five different benchmark datasets and is proved superior to the existing state-of-the-art methods with a minimum Mean Absolute error (MAE) of 0.03 and F-measure of 0.956. 相似文献
2.
3.
El-Shafiey Mohamed G. Hagag Ahmed El-Dahshan El-Sayed A. Ismail Manal A. 《Multimedia Tools and Applications》2022,81(13):18155-18179
Multimedia Tools and Applications - Nowadays, heart diseases are significantly contributing to deaths all over the world. Thus, heart-disease prediction has garnered considerable attention in the... 相似文献
4.
Flash cosintering of a lanthanum strontium cobalt ferrite nanofibre/Gd-doped ceria bilayer structure
《Journal of the European Ceramic Society》2022,42(6):2870-2878
For solid oxide fuel cells, an important structural requirement is that the electrolyte layer needs to be dense and the electrode layer porous, which is difficult to obtain by conventional cosintering. In this work, flash cosintering of a double layer structure consisting of a Gd-doped ceria substrate with a lanthanum strontium cobalt ferrite nanofibre coating is investigated. Experimental and finite element modelling results reveal that when the LSCF layer is connected to the electrode, the heat is concentrated in the LSCF layer, which leads to a huge temperature gradient and introduces severe cracking. When the LSCF layer is electrically isolated from the electrode, the heat is concentrated in the GDC layer, and the temperature gradient is dramatically reduced. In this situation, the density of GDC can reach 92.86% while a high porosity of 52.26% is maintained in the LSCF layer, which is higher than that of the conventional cosintered sample. 相似文献
5.
《Journal of the European Ceramic Society》2022,42(6):2879-2891
In this study, seven different filler materials in different proportions were added to a Ba-Ca-Si glass matrix “H” to investigate new sealant with higher thermal expansion coefficient (CTE) value and good sealing performance for application in oxygen transport membrane (OTM). SrTi0.75Fe0.25O3-δ (STF25) was used as an OTM, and the sealing partners were ferritic steel Aluchrom and pre-oxidized Aluchrom. Compatibility tests were carried out to investigate the feasibility of the composites. Higher CTE values were found in dilatometer tests on composite samples by adding 40 wt% Ag (HAg40) and 30 wt% Ni-Cr (HNC30). Gas-tightness measurements of sandwiched samples produced appropriate helium leakage rates in the range of 10?6 mbar·l·s?1. Sealing behaviour of sealants HAg40 and HNC30 were investigated by joining STF25 and as-delivered/pre-oxidized Aluchrom together. Scanning electron microscopy (SEM) on cross-sections of the joints revealed a homogeneous microstructure and good adherence of the glass sealants to support metals and STF25. 相似文献
6.
The rapid deployment of digital technologies drives the conventional product service system (PSS) to shift into a new paradigm known as smart PSS. Empowered with smart capabilities, smart PSS has great potential in creating positive user experience (UX). The requirements analysis is an essential task for successful development of smart PSS with strong UX. Nevertheless, there is still a lack of research on the requirement analysis of smart PSS by incorporating smart-enabled UX perspective. Hence, this paper proposes a framework of user experience-oriented smart service requirement (UXO-SSR) analysis for smart PSS development. At first, the relevant factors (e.g., user personas and activity journey) are integrated to conceptualize the UX in smart PSS context. Second, a four-phase model is proposed for identifying UXO-SSR, which can provide an effective tool for acquiring UX requirements of smart PSS from holistic perspective. Third, a novel asymmetric trapezium cloud-based uncertain linguistic BWM approach is developed to evaluate the priority of the identified UXO-SSRs. The approach can appropriately handle the hybrid uncertainties (i.e., hesitancy, fuzziness and randomness) of linguistic evaluation information, thereby improving the accuracy of evaluation results. Finally, a case study of smart sleep service system is presented to demonstrate the feasibility and reliability of the proposed framework. 相似文献
7.
8.
This work investigated incorporation of Nannochloropsis salina into renneted dairy gels and curd. Whole and ruptured microalgal cells did not impair κ-casein macropeptide cleavage by the rennet enzyme. However, insoluble components of ruptured cells impeded gelation, presumably by hindering interactions between renneted casein micelles. Confocal imaging showed that whole cells were retained and homogenously distributed within the protein network of the gels and cooked curd, whereas ruptured algae formed large aggregates that altered the protein matrix. Eicosapentaenoic acid (EPA) in the whole microalgal cells was incorporated within the curds, with considerably less EPA retained for ruptured cells. Soluble algal debris did not impair gelation, however EPA wasn't retained in the curd. The study demonstrates that nutrient enrichment of renneted dairy products is possible by incorporating whole microalgal cells to displace milk fat with protein and the beneficial long-chain omega-3 fatty acid EPA. Future research into the optimisation of product organoleptic properties is required. 相似文献
9.
Machine learning algorithms have been widely used in mine fault diagnosis. The correct selection of the suitable algorithms is the key factor that affects the fault diagnosis. However, the impact of machine learning algorithms on the prediction performance of mine fault diagnosis models has not been fully evaluated. In this study, the windage alteration faults (WAFs) diagnosis models, which are based on K-nearest neighbor algorithm (KNN), multi-layer perceptron (MLP), support vector machine (SVM), and decision tree (DT), are constructed. Furthermore, the applicability of these four algorithms in the WAFs diagnosis is explored by a T-type ventilation network simulation experiment and the field empirical application research of Jinchuan No. 2 mine. The accuracy of the fault location diagnosis for the four models in both networks was 100%. In the simulation experiment, the mean absolute percentage error (MAPE) between the predicted values and the real values of the fault volume of the four models was 0.59%, 97.26%, 123.61%, and 8.78%, respectively. The MAPE for the field empirical application was 3.94%, 52.40%, 25.25%, and 7.15%, respectively. The results of the comprehensive evaluation of the fault location and fault volume diagnosis tests showed that the KNN model is the most suitable algorithm for the WAFs diagnosis, whereas the prediction performance of the DT model was the second-best. This study realizes the intelligent diagnosis of WAFs, and provides technical support for the realization of intelligent ventilation. 相似文献
10.
《Journal of the European Ceramic Society》2022,42(13):5684-5690
In this work, Zn-Ni co-modified LiMg0.9Zn0.1-xNixPO4 (x = 0–0.1) microwave dielectric ceramics were fabricated using a solid state synthesis route. Rietveld refinement of the XRD data revealed that all ceramic samples have formed a single phase with olivine structure. SEM images showed that the samples have a dense microstructure, that agrees with the measured relative density of 97.73 %. Based on the complex chemical bond theory, Raman and infrared reflectance spectra, we postulate that εr is mainly affected by the ionic polarizability, lattice and bond energy, while P-O bond plays a decisive role in Q×f and τf value. Optimum properties of Q×f ~ 153,500 GHz, εr ~ 7.13 and τf ~ ?59 ppm/°C were achieved for the composition LiMg0.9Zn0.06Ni0.04PO4 sintered at 875 ℃ for 2 h. This set of properties makes these ceramics an excellent candidate for LTCC, wave-guide filters and antennas for 5 G/6 G communication applications. 相似文献