全文获取类型
收费全文 | 205339篇 |
免费 | 25267篇 |
国内免费 | 11931篇 |
专业分类
电工技术 | 23319篇 |
技术理论 | 6篇 |
综合类 | 21011篇 |
化学工业 | 25307篇 |
金属工艺 | 11909篇 |
机械仪表 | 18342篇 |
建筑科学 | 14137篇 |
矿业工程 | 10303篇 |
能源动力 | 8310篇 |
轻工业 | 9191篇 |
水利工程 | 6191篇 |
石油天然气 | 10193篇 |
武器工业 | 4509篇 |
无线电 | 17860篇 |
一般工业技术 | 17814篇 |
冶金工业 | 6924篇 |
原子能技术 | 2442篇 |
自动化技术 | 34769篇 |
出版年
2024年 | 712篇 |
2023年 | 2994篇 |
2022年 | 6333篇 |
2021年 | 8475篇 |
2020年 | 6822篇 |
2019年 | 5449篇 |
2018年 | 5575篇 |
2017年 | 7344篇 |
2016年 | 9401篇 |
2015年 | 10481篇 |
2014年 | 14413篇 |
2013年 | 13512篇 |
2012年 | 15048篇 |
2011年 | 15162篇 |
2010年 | 11937篇 |
2009年 | 11877篇 |
2008年 | 11130篇 |
2007年 | 14289篇 |
2006年 | 12924篇 |
2005年 | 10785篇 |
2004年 | 8538篇 |
2003年 | 7434篇 |
2002年 | 5808篇 |
2001年 | 4918篇 |
2000年 | 4117篇 |
1999年 | 3191篇 |
1998年 | 2370篇 |
1997年 | 2036篇 |
1996年 | 1810篇 |
1995年 | 1494篇 |
1994年 | 1212篇 |
1993年 | 840篇 |
1992年 | 696篇 |
1991年 | 590篇 |
1990年 | 472篇 |
1989年 | 394篇 |
1988年 | 275篇 |
1987年 | 198篇 |
1986年 | 183篇 |
1985年 | 156篇 |
1984年 | 175篇 |
1983年 | 126篇 |
1982年 | 127篇 |
1981年 | 76篇 |
1980年 | 89篇 |
1979年 | 54篇 |
1977年 | 34篇 |
1964年 | 37篇 |
1962年 | 66篇 |
1959年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
《Journal of the European Ceramic Society》2022,42(5):2429-2440
A ring-on-ring (ROR) test is a prevailing test method for evaluating the equi-biaxial strength of glass materials. However, current ROR test standards limit the strength and size of glass to prevent a nonlinear behavior. In this study, the feasibility of ROR testing for non-standard, high-strength glass, such as tempered or ion-exchanged rectangular glass is investigated. To this end, ROR simulation based on theory and experiment is conducted for thirty non-standard glasses with widths of 100–300 mm and aspect ratios of 1.0–2.0. As a result, the maximum measurable stress was about 215.6 MPa for 100 × 200 mm glass and 481.3 MPa for 300 × 600 mm glass with a 3% deviation, which is well above the strength of regular tempered glass. The main purpose of this work is to understand the range of aspect ratio of horizontal and vertical widths of a glass plate that can be evaluated by the standard ROR test. 相似文献
12.
13.
Anna Stasiowicz Natalia Rosiak Ewa Tykarska Maciej Kozak Jacek Jenczyk Piotr Szulc Joanna Kobus-Cisowska Kornelia Lewandowska Anita Paziska Wojciech Paziski Judyta Cielecka-Piontek 《International journal of molecular sciences》2021,22(8)
Piperine is an alkaloid that has extensive pharmacological activity and impacts other active substances bioavailability due to inhibition of CYP450 enzymes, stimulation of amino acid transporters and P-glycoprotein inhibition. Low solubility and the associated low bioavailability of piperine limit its potential. The combination of piperine with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) causes a significant increase in its solubility and, consequently, an increase in permeability through gastrointestinal tract membranes and the blood–brain barrier. X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) were used to characterize interactions between piperine and HP-β-CD. The observed physicochemical changes should be combined with the process of piperine and CD system formation. Importantly, with an increase in solubility and permeability of piperine as a result of interaction with CD, it was proven to maintain its biological activity concerning the antioxidant potential (2,2-diphenyl-1-picryl-hydrazyl-hydrate assay), inhibition of enzymes essential for the inflammatory process and for neurodegenerative changes (hyaluronidase, acetylcholinesterase, butyrylcholinesterase). 相似文献
14.
15.
互联网通讯采取标准化模式主要以TCP/IP协议为载体,通讯的优越特性体现在同时具备便捷性与开放性,为办公提供很大的便利,但基于网络系统也会入侵病毒、也会给信息数据与办公体系安全性造成威胁,直接影响企业综合稳定发展。据此,为保障办公工作的顺利开展,本文对计算机网络办公自动化及安全策略进行详细分析。 相似文献
17.
18.
Mehdi Hosseini Abadshapoori 《亚洲传热研究》2021,50(2):1056-1072
Increasing the heat capacity of heat exchangers is a crucial need for modern devices. The thermal conductivity of the usual fluids and the Nusselt (Nu) number of flows containing such fluids are two bottlenecks in the way of increasing heat delivery in the heat exchangers. For this reason, nanofluids have been introduced. The effect of utilizing a Cu-water nanofluid as a coolant of two hot pipes in a square cavity is investigated numerically with a two-component lattice Boltzmann method. The volume fraction of nanoparticles is assumed to be constant (0.03) while the Richardson (Ri) number varies from 0.02 to 20. Results show that the effectiveness of nanoparticles is better observed in the natural convection mode. However, sedimentation is also very probable at high Ri numbers, which significantly reduces the effectiveness of the nanoparticles. Configurations which produce a natural convection stream similar to the forced convection one as well as the configurations with high spacing and hence, low heat stream interactions, are the best choices for a uniform heat rate from the pipes. 相似文献
19.
为研究金针菇多糖(polysaccharide from Flammulina velutipes,FVP)对微冻大黄鱼及鱼片在贮藏期间肌原纤维蛋白性质的变化及水分分布的影响,实验分别选用0.03、0.06、0.09 g/L FVP浸渍处理大黄鱼和鱼片,以无菌水处理为对照组,分析微冻贮藏期间样品的感官指标得分、总挥发性盐基氮含量、总巯基含量、Ca2+-ATPase活性、蛋白流变学性质以及水分迁移变化规律。结果表明:FVP可有效抑制整鱼总挥发性盐基氮含量上升和感官得分的下降;减缓整鱼及鱼片在微冻过程中总巯基含量、Ca2+-ATPase活性下降和水分流失;此外FVP还能够延缓大黄鱼因腐败而出现的蛋白凝胶能力减弱。在本实验选取的多糖浓度范围内,0.09 g/L FVP处理组保鲜效果较强。该研究结果可为FVP用于水产品贮运保鲜提供理论参考。 相似文献
20.