全文获取类型
收费全文 | 159364篇 |
免费 | 24121篇 |
国内免费 | 17314篇 |
专业分类
化学 | 83020篇 |
晶体学 | 1518篇 |
力学 | 7865篇 |
综合类 | 882篇 |
数学 | 14426篇 |
物理学 | 46383篇 |
无线电 | 46705篇 |
出版年
2024年 | 364篇 |
2023年 | 3535篇 |
2022年 | 3979篇 |
2021年 | 5681篇 |
2020年 | 5847篇 |
2019年 | 5522篇 |
2018年 | 4703篇 |
2017年 | 4673篇 |
2016年 | 6719篇 |
2015年 | 7103篇 |
2014年 | 8690篇 |
2013年 | 11213篇 |
2012年 | 13325篇 |
2011年 | 13922篇 |
2010年 | 10296篇 |
2009年 | 10151篇 |
2008年 | 10717篇 |
2007年 | 9834篇 |
2006年 | 9259篇 |
2005年 | 7895篇 |
2004年 | 5632篇 |
2003年 | 4723篇 |
2002年 | 4257篇 |
2001年 | 3540篇 |
2000年 | 3215篇 |
1999年 | 3467篇 |
1998年 | 2955篇 |
1997年 | 2537篇 |
1996年 | 2765篇 |
1995年 | 2232篇 |
1994年 | 2089篇 |
1993年 | 1682篇 |
1992年 | 1548篇 |
1991年 | 1359篇 |
1990年 | 1065篇 |
1989年 | 745篇 |
1988年 | 628篇 |
1987年 | 472篇 |
1986年 | 467篇 |
1985年 | 401篇 |
1984年 | 295篇 |
1983年 | 224篇 |
1982年 | 183篇 |
1981年 | 124篇 |
1980年 | 106篇 |
1979年 | 70篇 |
1978年 | 63篇 |
1977年 | 51篇 |
1976年 | 49篇 |
1974年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Du Yongbo Yu Pengfei Wang Junxiong Zhang Jinping Wang Chang’an Che Defu 《Journal of Thermal Analysis and Calorimetry》2021,143(1):327-334
Journal of Thermal Analysis and Calorimetry - Coal O2/CO2 combustion is a promising carbon capture and storage technology for coal-fired power plant. Char consumption rate prediction is essential... 相似文献
72.
This minireview describes the strategies for synthesis of fiuorinated surfactants potentially nonbioaccumulable.Various strategies have been focused on(Ⅰ) reducing the length of the perfluorocarbon chain,(Ⅱ) introducing hetero atoms into the fluorocarbon chain,(Ⅲ) introducing branch(herein and after branch means the fluoro-carbon chain section is not straight).In most cases,the surface tensions versus the surfactant concentrations have been assessed.These above strategies led to various highly fiuorinated(perfluorinated or not perfluorinated) surfactants whose chemical changes enabled to obtain novel alternatives to perfluorooctanoic acid(PFOA) and perfluorooctane sulphonate(PFOS). 相似文献
73.
74.
Rajkumar P. Diwakar K. Subadevi R. Gnanamuthu R. M. Wang Fu-Ming Liu Wei-Ren Sivakumar M. 《Journal of Solid State Electrochemistry》2021,25(3):939-948
Journal of Solid State Electrochemistry - The “shuttle effect” of polysulfides is a serious issue, resulting in a decrease in the life-cycle of lithium-sulfur (Li-S) batteries. To... 相似文献
75.
76.
以4-羟基吲哚为原料,经吲哚环4位乙酰基化、3位亲电取代、酰胺化和还原加氢等反应合成目标化合物7.通过核磁共振氢谱及碳谱对化合物进行结构表征,并对目标化合物进行体外抗氧化生物活性测试.初步生物活性测试结果表明,化合物7a,7b,7c和7d对DPPH·均有很强的清除作用(清除率为85.25%~90.73%),7e,7f,7g,7h作用较差;目标化合物与Vc相比,对·OH的清除作用稍差,最高清除率25.66%(Vc的最高清除率为34.67),但各化合物整体水平相当;在清除O-2·能力上化合物7a,7d,7g,7h最大清除率(分别为19.34,35.35,27.93和31.74)均强于同等浓度的Vc(17.58). 相似文献
77.
Bo Wang Edison Huixiang Ang Yang Yang Yufei Zhang Hongbo Geng Minghui Ye Cheng Chao Li 《Advanced functional materials》2020,30(28)
Orthorhombic molybdenum trioxide (MoO3) is one of the most promising anode materials for sodium‐ion batteries because of its rich chemistry associated with multiple valence states and intriguing layered structure. However, MoO3 still suffers from the low rate capability and poor cycle induced by pulverization during de/sodiation. An ingenious two‐step synthesis strategy to fine tune the layer structure of MoO3 targeting stable and fast sodium ionic diffusion channels is reported here. By integrating partially reduction and organic molecule intercalation methodologies, the interlayer spacing of MoO3 is remarkably enlarged to 10.40 Å and the layer structural integration are reinforced by dimercapto groups of bismuththiol molecules. Comprehensive characterizations and density functional theory calculations prove that the intercalated bismuththiol (DMcT) molecules substantially enhanced electronic conductivity and effectively shield the electrostatic interaction between Na+ and the MoO3 host by conjugated double bond, resulting in improved Na+ insertion/extraction kinetics. Benefiting from these features, the newly devised layered MoO3 electrode achieves excellent long‐term cycling stability and outstanding rate performance. These achievements are of vital significance for the preparation of sodium‐ion battery anode materials with high‐rate capability and long cycling life using intercalation chemistry. 相似文献
78.
Yong Xu Yun Li Songlin Li Francis Balestra Gerard Ghibaudo Wenwu Li Yen‐Fu Lin Huabin Sun Jing Wan Xinran Wang Yufeng Guo Yi Shi Yong‐Young Noh 《Advanced functional materials》2020,30(20)
Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field‐effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate‐dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research. 相似文献
79.
本文对国内外的电视技术发展现状进行了充分的研究和分析,并对超高清电视系统的相关图像技术参数进行了分析和介绍。 相似文献
80.
We investigate terahertz radiation(T-rays) from a pentacene organic diode at room temperature. The quantum chemistry calculation for frequency-related Huang–Rhys factor of pentacene is also carried out. The results demonstrate that the T-rays can come from a bending vibration of pentacene skeleton after the energy of pentacene exciton transferring to the vibrational excited state via electron–phonon coupling. Frequency and natural bond orbital analytics of pentacene and its derivatives are performed in order to explain the result and develop new materials to get higher emission. This work provides a new way to produce T-rays with a simple device at room temperature. 相似文献