全文获取类型
收费全文 | 46743篇 |
免费 | 5726篇 |
国内免费 | 2592篇 |
专业分类
电工技术 | 3274篇 |
技术理论 | 10篇 |
综合类 | 6796篇 |
化学工业 | 2968篇 |
金属工艺 | 1059篇 |
机械仪表 | 3260篇 |
建筑科学 | 3708篇 |
矿业工程 | 1531篇 |
能源动力 | 1432篇 |
轻工业 | 617篇 |
水利工程 | 1163篇 |
石油天然气 | 984篇 |
武器工业 | 654篇 |
无线电 | 4307篇 |
一般工业技术 | 4964篇 |
冶金工业 | 2273篇 |
原子能技术 | 378篇 |
自动化技术 | 15683篇 |
出版年
2025年 | 487篇 |
2024年 | 1345篇 |
2023年 | 1320篇 |
2022年 | 1436篇 |
2021年 | 1655篇 |
2020年 | 1563篇 |
2019年 | 1443篇 |
2018年 | 1416篇 |
2017年 | 1597篇 |
2016年 | 1754篇 |
2015年 | 1790篇 |
2014年 | 2488篇 |
2013年 | 3100篇 |
2012年 | 2934篇 |
2011年 | 3093篇 |
2010年 | 2463篇 |
2009年 | 2605篇 |
2008年 | 2687篇 |
2007年 | 2763篇 |
2006年 | 2583篇 |
2005年 | 2230篇 |
2004年 | 1805篇 |
2003年 | 1517篇 |
2002年 | 1281篇 |
2001年 | 1072篇 |
2000年 | 923篇 |
1999年 | 830篇 |
1998年 | 658篇 |
1997年 | 596篇 |
1996年 | 487篇 |
1995年 | 477篇 |
1994年 | 386篇 |
1993年 | 327篇 |
1992年 | 299篇 |
1991年 | 220篇 |
1990年 | 185篇 |
1989年 | 198篇 |
1988年 | 159篇 |
1987年 | 77篇 |
1986年 | 102篇 |
1985年 | 76篇 |
1984年 | 79篇 |
1983年 | 52篇 |
1982年 | 63篇 |
1981年 | 47篇 |
1980年 | 37篇 |
1979年 | 36篇 |
1978年 | 31篇 |
1977年 | 29篇 |
1955年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
982.
Kaili Wu;Chaojie Lyu;Jiarun Cheng;Zhonglu Guo;Hongyu Li;Xixi Zhu;Woon-Ming Lau;Jinlong Zheng; 《Small (Weinheim an der Bergstrasse, Germany)》2024,20(9):2304390
Exploring and developing novel strategies for constructing heterostructure electrocatalysts is still challenging for water electrolysis. Herein, a creative etching treatment strategy is adopted to construct NiSe2/Ni0.85Se heterostructure. The rich heterointerfaces between NiSe2 and Ni0.85Se emerge strong electronic interaction, which easily induces the electron transfer from NiSe2 to Ni0.85Se, and tunes the charge-state of NiSe2 and Ni0.85Se. In the NiSe2/Ni0.85Se heterojunction nanomaterial, the higher charge-state Ni0.85Se is capable of affording partial electrons to combine with hydrogen protons, inducing the rapid formation of H2 molecule. Accordingly, the lower charge-state NiSe2 in the NiSe2/Ni0.85Se heterojunction nanomaterial is more easily oxidized into high valence state Ni3+ during the oxygen evolution reaction (OER) process, which is beneficial to accelerate the mass/charge transfer and enhance the electrocatalytic activities towards OER. Theoretical calculations indicate that the heterointerfaces are conducive to modulating the electronic structure and optimizing the adsorption energy toward intermediate H* during the hydrogen evolution reaction (HER) process, leading to superior electrocatalytic activities. To expand the application of the NiSe2/Ni0.85Se-2h electrocatalyst, urea is served as the adjuvant to proceed with the energy-saving hydrogen production and pollutant degradation, and it is proven to be a brilliant strategy. 相似文献
983.
Meiling Pan;Xiuhua Cui;Qun Jing;Haiming Duan;Fangping Ouyang;Rong Wu; 《Small (Weinheim an der Bergstrasse, Germany)》2024,20(27):2308416
Developing efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) bifunctional electrocatalysts is attractive for rechargeable metal–air batteries. Meanwhile, single metal atoms embedded in 2D layered transition metal chalcogenides (TMDs) have become a very promising catalyst. Recently, many attentions have been paid to the 2D ReS2 electrocatalyst due to its unique distorted octahedral 1T’ crystal structure and thickness-independent electronic properties. Here, the catalytic activity of different transition metal (TM) atoms embedded in ReS2 using the density functional theory is investigated. The results indicate that TM@ReS2 exhibits outstanding thermal stability, good electrical conductivity, and electron transfer for electrochemical reactions. And the Ir@ReS2 and Pd@ReS2 can be used as OER/ORR bifunctional electrocatalysts with a lower overpotential for OER (ηOER) of 0.44 V and overpotentials for ORR (ηORR) of 0.26 V and 0.27 V, respectively. The excellent catalytic activity is attributed to the optimal adsorption strength for oxygen intermediates coming from the effective modulation of the electronic structure of ReS2 after Ir/Pd doping. The results can help to deeply understand the catalytic activity of TM@ReS2 and develop novel and highly efficient OER/ORR electrocatalysts. 相似文献
984.
《钢铁研究学报(英文版)》2024,31(10)
Brazing,an important welding and joining technology,can achieve precision joining of materials in advanced manufacturing.And the first principle calculation is a new material simulation method in high-throughput computing.It can calculate the interfacial structure,band structure,electronic structure,and other properties between dissimilar materials,predicting various properties.It plays an important role in assisting practical research and guiding experimental designs by predicting material properties.It can largely improve the quality of welded components and joining efficiency.The relevant theoretical foundation is reviewed,including the first principle and density functional theory.Exchange-correlation functional and pseudopotential plane wave approach was also introduced.Then,the latest research progress of the first principle in brazing was also summarized.The application of first principle calculation mainly includes formation energy,adsorption energy,surface energy,adhesion work,interfacial energy,interfacial contact angle,charge density differences,density of states,and mulliken population.The energy,mechanical,and electronic properties were discussed.Finally,the limitations and shortcomings of the research in the first principle calculation of brazed interface were pointed out.Future developmental directions were presented to provide reference and theoretical basis for realizing high-throughput calculations of brazed joint interfaces. 相似文献
985.
Ruidong Zhang;Zelin Guo;Hai Huan; 《Expert Systems》2024,41(3):e13511
The purpose of text classification is to label the text with known labels. In recent years, the method based on graph neural network (GNN) has achieved good results. However, the existing methods based on GNN only regard the text as the set of co-occurring words, without considering the position information of each word in the statement. At the same time, the method mainly extracts the node features in the graph, and the edge features between the nodes are not used enough. To solve these problems, a new text classification method, graph convolutional network using positions and edges, is proposed. In the word embedding section, a positional encoding input representation is employed to enable the neural network to learn the relative positional information among words. Meanwhile, the dimension of the adjacency matrix is increased to extract the multi-dimensional edge features. Through experiments on multiple text classification datasets, the proposed method is shown to be superior to the traditional text classification method, and has achieved a maximum improvement of more than 4%. 相似文献
986.
Marco Rüth;Maria Jansen;Kai Kaspar; 《Journal of Computer Assisted Learning》2024,40(5):1987-2008
Online exams have become a more common form of assessment at universities due to the Covid-19 pandemic. However, cheating behaviour in online exams is widespread and threatens exam validity as well as student learning and well-being. 相似文献
987.
Shang Shanshan;Geng Sen; 《Journal of Computer Assisted Learning》2024,40(4):1941-1958
Artificial intelligence–generated content (AIGC) has stepped into the spotlight with the emergence of ChatGPT, making effective use of AIGC for education a hot topic. 相似文献
988.
Adam Shearer;John C. Mauro; 《International Journal of Applied Glass Science》2024,15(3):195-202
Topological constraint theory has emerged as a rapid, predictive method to quantify the relationship between structural rigidity and glass properties. Understanding the structure of telluro-vanadate (TeO2–V2O5) glasses has remained difficult owing to their complex mixture of structural units. Here, we propose a topological model that accurately captures the glass structure and can be used to predict properties such as glass transition temperature and hardness. The experimentally obtained properties are in agreement with predicted properties by the model suggesting that this simplified structural model accurately describes the V2O5–TeO2 structure. 相似文献
989.
Poly Rose;Jeevan Kumar Pallagani;Seshu Bai Vummethala;Rajasekharan T; 《International Journal of Applied Ceramic Technology》2024,21(6):4063-4072
This paper brings out an innovation in fabricating porous magnesia-stabilized zirconia components by infiltrating free-flowing suspension into polyurethane foam. The process enables the production of samples with different levels of porosity and pore structure by easily controlling the amount of slurry infiltrated into the foam. The process uses Isobam, a nontoxic binder, which makes the fabrication simple and environment-friendly. Samples with five different levels of total porosity ranging from 41.7% to 62.4% were fabricated. Microstructural studies revealed multimodal pore structure comprising both open and closed porosities. Measurements on thermal properties and compressive strength of the samples showed that the sample with the lowest porosity exhibited a thermal conductivity of 0.495 W/mK and a compressive strength of 45.7 MPa. The measured values of thermal conductivity of the samples with different porosity levels could be described by modified effective medium theory. Present work opens up enormous possibilities for economical industrial production of porous magnesia-stabilized zirconia components for biomedical and thermal insulation applications. 相似文献
990.