全文获取类型
收费全文 | 68742篇 |
免费 | 7583篇 |
国内免费 | 4631篇 |
专业分类
电工技术 | 6045篇 |
技术理论 | 2篇 |
综合类 | 6283篇 |
化学工业 | 9669篇 |
金属工艺 | 4265篇 |
机械仪表 | 4621篇 |
建筑科学 | 5535篇 |
矿业工程 | 2272篇 |
能源动力 | 1983篇 |
轻工业 | 6332篇 |
水利工程 | 1841篇 |
石油天然气 | 3004篇 |
武器工业 | 814篇 |
无线电 | 7949篇 |
一般工业技术 | 6327篇 |
冶金工业 | 2761篇 |
原子能技术 | 1566篇 |
自动化技术 | 9687篇 |
出版年
2024年 | 167篇 |
2023年 | 1201篇 |
2022年 | 2603篇 |
2021年 | 3536篇 |
2020年 | 2638篇 |
2019年 | 1842篇 |
2018年 | 1968篇 |
2017年 | 2159篇 |
2016年 | 1784篇 |
2015年 | 2981篇 |
2014年 | 3808篇 |
2013年 | 4281篇 |
2012年 | 5286篇 |
2011年 | 5546篇 |
2010年 | 5116篇 |
2009年 | 4886篇 |
2008年 | 4840篇 |
2007年 | 4660篇 |
2006年 | 4381篇 |
2005年 | 3514篇 |
2004年 | 2438篇 |
2003年 | 1982篇 |
2002年 | 1998篇 |
2001年 | 1831篇 |
2000年 | 1409篇 |
1999年 | 963篇 |
1998年 | 532篇 |
1997年 | 501篇 |
1996年 | 453篇 |
1995年 | 324篇 |
1994年 | 286篇 |
1993年 | 220篇 |
1992年 | 196篇 |
1991年 | 120篇 |
1990年 | 99篇 |
1989年 | 91篇 |
1988年 | 70篇 |
1987年 | 48篇 |
1986年 | 38篇 |
1985年 | 18篇 |
1984年 | 27篇 |
1983年 | 16篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1980年 | 18篇 |
1979年 | 12篇 |
1976年 | 4篇 |
1962年 | 2篇 |
1959年 | 23篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
1.
Nan Wu Xiaodong Li Mu Zhang Yi Ren Qi Zhu Haijun Peng Hongqiang Ru Xudong Sun 《Journal of the European Ceramic Society》2021,41(4):2898-2907
Refining ceramic microstructures to the nanometric range to minimize light scattering provides an interesting methodology for developing novel optical ceramic materials. In this work, we reported the fabrication and properties of a new nanocomposite optical ceramic of Gd2O3-MgO. The citric acid sol-gel combustion method was adopted to fabricate Gd2O3-MgO nanocomposites with fine-grain sizes, dense microstructures and homogeneous phase domains. Nanopowders with low agglomeration and improved sinterability can be obtained by elaborating Φ values. Further refining of the microstructure of the nanocomposites was achieved by elaborating the hot-pressing conditions. The sample sintered at 65 MPa and 1300 °C showed a quite high hardness value of 14.3 ± 0.2 GPa, a high transmittance of 80.3 %–84.7 % over the 3?6 μm wavelength range, due mainly to its extremely fine-grain size of Gd2O3 and MgO (93 and 78 nm, respectively) and high density. 相似文献
2.
3.
Zhongchao Fu Xiaodong Li Mu Zhang Qi Zhu Ji-Guang Li Jiao He Xing'an Wang Xudong Sun 《Journal of the American Ceramic Society》2021,104(6):2689-2701
An easy albeit quite effective deionization suspension treatment was adopted to alleviate the detrimental effects related to the hydrolysis of Y2O3 in an aqueous medium. Fabrication of highly transparent Y2O3 ceramics with a fine grain size via air pre-sintering and post–hot isostatic pressing (HIP) treatment without using any sintering additive was achieved using the treated suspensions. The hydrolysis issue of Y2O3 powder in an aqueous medium was effectively alleviated by using deionization treatment, and a well-dispersed suspension with a low concentration of dissolved Y3+ species was obtained. The dispersed suspensions were consolidated by the centrifugal casting method, and the green bodies derived from the suspension of 35.0 vol% solid loading showed an improved homogeneity with a relative density of 52.1%. Fully dense Y2O3 transparent ceramic with high transparency was obtained by pre-sintering consolidated green compacts at a low temperature of 1400°C for 16 h in air followed by a post-HIP treatment at 1550°C for 2 h under 200 MPa pressure. The sample had a fine average grain size of 690 nm. The in-line transmittance of the sample reached 83.3% and 81.8% at 1100 nm and 800 nm, respectively, very close to the theoretical values of Y2O3. 相似文献
4.
以三只股票的历史数据作原始序列,建立了GM(1,1)模型与ARIMA自适应过滤组合模型.分析两种模型的应用场景,并以ARIMA模型为基础建立股价反转判断模型.实验证明,所建立的模型在短期内的拟合、预测与反转判断效果较为理想. 相似文献
5.
以驻村扶贫点滇西南L县X村的光棍为研究对象,侧重个体精准性,强调个体因果性的特征,运用小数据分析该村光棍的贫困特征和生成原因,基于马斯洛需求层次理论探索光棍内生动力激发机制.研究表明:农村光棍趋于年轻化,形势严峻;光棍成因受到外部资源匮乏的限制,又受到自身资源缺陷的制约,内外因相互影响,但外因只有通过内因才能发挥作用.探讨通过需求原理激发光棍群体的内生动力,构建长效治理机制,让光棍群体最大限度实现人生价值,提升社会获得感和幸福感. 相似文献
6.
Qi Xiao Xinyao Dong Xiumei Yin Hong Wang Hua Zhong Mingming Xing Ying Tian Yao Fu Bin Dong Xixian Luo 《Journal of the American Ceramic Society》2021,104(3):1415-1423
Multicolor upconversion luminescence materials show significantly applications in materials science. In this paper, the novel Yb3+-sensitized Na3La(VO4)2 upconversion luminescence crystals are synthesized by the solid-state reaction method. Three primary colors upconversion luminescence are successfully achieved in Na3La(VO4)2:Yb3+,Tm3+, Na3La(VO4)2:Yb3+,Er3+, and Na3La(VO4)2:Yb3+,Ho3+ crystals excited by the single 980 nm LD. Multicolor upconversion luminescence can be obtained by simply adjusting the combination ratios of these three samples. Luminescence mechanisms of the Yb3+-sensitized system are discussed in detail. In the Na3La(VO4)2 host material, the Yb3+/Ho3+ codoped system exhibits unusual red upconversion luminescence based on the short decay time of Ho3+ ion 5I6 level, which provides the possibility of three primary color luminescence under 980 nm excitation. 相似文献
7.
Zhang Qi Wang Yujing Zhang Xueling Song Jun Li Yinlei Wu Xuehong Yuan Kunjie 《Journal of Materials Science》2022,57(14):7208-7224
Journal of Materials Science - Form-stable composite phase change materials (C-PCMs) prepared by microencapsulation method and porous matrix adsorption method need for compression molding after... 相似文献
10.