全文获取类型
收费全文 | 4252篇 |
免费 | 587篇 |
国内免费 | 637篇 |
专业分类
化学 | 4037篇 |
晶体学 | 72篇 |
力学 | 23篇 |
综合类 | 30篇 |
数学 | 4篇 |
物理学 | 756篇 |
无线电 | 554篇 |
出版年
2024年 | 17篇 |
2023年 | 117篇 |
2022年 | 85篇 |
2021年 | 143篇 |
2020年 | 196篇 |
2019年 | 127篇 |
2018年 | 124篇 |
2017年 | 132篇 |
2016年 | 203篇 |
2015年 | 197篇 |
2014年 | 233篇 |
2013年 | 376篇 |
2012年 | 275篇 |
2011年 | 279篇 |
2010年 | 203篇 |
2009年 | 240篇 |
2008年 | 266篇 |
2007年 | 277篇 |
2006年 | 300篇 |
2005年 | 211篇 |
2004年 | 231篇 |
2003年 | 209篇 |
2002年 | 186篇 |
2001年 | 94篇 |
2000年 | 109篇 |
1999年 | 104篇 |
1998年 | 88篇 |
1997年 | 77篇 |
1996年 | 79篇 |
1995年 | 65篇 |
1994年 | 41篇 |
1993年 | 31篇 |
1992年 | 43篇 |
1991年 | 22篇 |
1990年 | 22篇 |
1989年 | 19篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 1篇 |
排序方式: 共有5476条查询结果,搜索用时 15 毫秒
61.
Ben Salah M Vilminot S André G Richard-Plouet M Bourée-Vigneron F Mhiri T Kurmoo M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(8):2048-2057
[Mn(3)(OH)(2)(SO(4))(2)(H(2)O)(2)] and its deuterated analogue were synthesized by a hydrothermal technique and characterized by differential thermal analysis, thermogravimetric analysis, and IR spectroscopy. Its nuclear structure, determined by single-crystal X-ray analysis and Rietveld analysis of neutron powder-diffraction data, consists of a 3D network of chains of edge-sharing Mn(1)O(6), running along the c axis, connected by the apices of Mn(2)O(6) and SO(4) units. It is isostructural to the nickel analogue. Determination of the magnetic structure and measurements of magnetization and heat capacity indicate the coexistence of both magnetic long-range ordering (LRO) and short-range ordering (SRO) below a Néel temperature of 26 K, while the SRO is retained at higher temperatures. The moments of the two independent Mn atoms lie in the bc plane, and that of Mn(1) rotates continuously by 54 degrees towards the c axis on decreasing the temperature from 25 to 1.4 K. While the SRO may be associated with frustration of the moments within a Mn(3) trimer, the LRO is achieved by antiparallel alignment of the four symmetry-related trimers within the magnetic unit cell. A spin-flop field, measured by dc and ac magnetization on a SQUID, is observed at 15 kOe. 相似文献
62.
The structures, energies, and natural atomic charges of 2-dimethylaminophenol oxide, 2-Me2N-(O)C6H4OH, and 2-dimethylphosphinylphenol, 2-Me2P(O)C6H4OH, in three different conformations were computed at the ab initio MP2/6-31G* level. Computed natural charges indicate distributions of electron density in amine oxides and phosphine oxides that are quite different from what is normally assumed on the basis of the formal charges in the usual representations of these compounds. The charges on nitrogen and phosphorus in these compounds are typically computed to be approximately zero on nitrogen and +2 on phosphorus, and the oxygen is considerably more negative in the phosphine oxide than in the amino oxide. Electronegativity differences thus play a larger role and formal charges a smaller one in determining atomic charges in these compounds than is generally believed. Despite the more negative oxygen in phosphine oxides, amine oxides are computed to be considerably more basic when participating in hydrogen bonding. Calculations treating the computed natural charges on these six conformations as point charges for classical approximations of the coulombic energies support the idea that the quantum mechanically computed relative energies are largely determined by coulombic interactions. 相似文献
63.
Changmin Lee Youngjae Hong Dongho Kim Younghwan Lim Jang Wook Choi Sung-Yoon Chung 《Advanced functional materials》2023,33(44):2303763
Protons in aqueous electrolytes can perform as an additional type of charge carrier for insertion/extraction in addition to the primary carrier cations in aqueous rechargeable batteries. Despite many diverse claims regarding the effect of protons, mutually conflicting experimental results and their interpretations without direct evidence have been reported over the last decade. Systematic examinations and analyses are thus imperative to clarify the conditions of proton insertion in aqueous rechargeable batteries. Utilizing V2O5 as a model cathode and beaker-type cells with a sufficient amount of ZnSO4 aqueous electrolytes in this work, it is demonstrated that protons are inserted into the cathode prior to Zn-ions in low-pH conditions (pH ≤ 3.0). In stark contrast, the influence of protons on the discharge voltage and capacity is insignificant, when either the pH becomes higher (pH ≥ 4.0) or the electrolyte volume is considerably low in coin-type cells. Similar behavior of pH-dependent proton insertion is also verified in Na–, Mg–, and Al-ion electrolytes. Providing a resolution to the controversy regarding proton insertion, the present study emphasizes that the influence of protons substantially varies depending on the pH and relative volume of electrolytes in aqueous batteries. 相似文献
64.
Tianhao Wu Xu Zhang Yinzhong Wang Nian Zhang Haifeng Li Yong Guan Dongdong Xiao Shiqi Liu Haijun Yu 《Advanced functional materials》2023,33(4):2210154
As one of the high-energy cathode materials of lithium-ion batteries (LIBs), lithium-rich-layered oxide with “single-crystal” characteristic (SC-LLO) can effectively restrain side reactions and cracks due to the reduced inner boundaries and enhanced mechanical stabilities. However, there are still high challenges for SC-LLO with diverse performance requirements, especially on their cycle stability improvement. Herein, a novel concentration gradient “single-crystal” LLO (GSC-LLO), with gradually decreasing Mn and increasing Ni contents from center to surface, is designed and prepared by combining co-precipitation and molten-salt sintering methods, yielding a capacity retention of 97.6% and an energy density retention of 95.8% within 100 cycles at 0.1 C. The enhanced performance is mostly attributed to the gradient-induced stabilized structure, free of cracks and less spinel-like structure formation after long-term cycling. Furthermore, the gradient design is also beneficial to the safety of LLOs as suggested by the improved thermal stability and reduced gas release. This study provides an effective strategy to prepare high-energy, high-stability, and high-safety LLOs for advanced LIBs. 相似文献
65.
Xiaobin Zou Haikuan Liang Yan Li Yichao Zou Fei Tian Yong Sun Chengxin Wang 《Advanced functional materials》2023,33(18):2213807
Following logic in the silicon semiconductor industry, the existence of native oxide and suitable fabrication technology is essential for 2D semiconductors in planar integronics, which are surface-sensitive to typical coating technologies. To date, very few types of integronics are found to possess this feature. Herein, the 2D Bi2O2Te developed recently is reported to possess large-area synthesis and controllable thermal oxidation behavior toward single-crystal native oxides. This shows that surface-adsorbed oxygen atoms are inclined to penetrate across [Bi2O2]n2n+ layers and bond with the underlying [Te]n2n− at elevated temperatures, transforming directly into [TeO4]n2n− with the basic architecture remaining stable. The oxide can be adjusted to form in an accurate layer-by-layer manner with a low-stress sharp interface. The native oxide Bi2TeO6 layer (bandgap of ≈2.9 eV) exhibits visible-light transparency and is compatible with wet-chemical selective etching technology. These advances demonstrate the potential of Bi2O2Te in planar-integrated functional nanoelectronics such as tunnel junction devices, field-effect transistors, and memristors. 相似文献
66.
Zepan Wang Peiyuan Wu Xubing Zou Sheng Wang Lei Du Ting Ouyang Zhao-Qing Liu 《Advanced functional materials》2023,33(16):2214275
By using the more electro-negative Mn3+ ion to partially replace Co3+ at the octahedral site of spinel ZnCo2O4, i.e., forming ternary Zn–Mn–Co spinel oxide, the electrocatalytic oxygen reduction/evolution activity is found to be significantly increased. Considering the physical characterization and theoretical calculations, it demonstrated that the bond competition played a key role in regulating the cobalt valence state and the electrocatalytic activity. The partial replacement of octahedral-site-occupied Co3+ by Mn3+ can effectively modulate the adjacent Co–O bond and induce the Jahn–Teller effect, thus changing the originally stable crystal structure and optimizing the binding strength between the active center and reaction intermediates. Certainly, the Mn-substituted ZnMn1.4Co0.6O4/NCNTs exhibit higher electrocatalytic oxygen reduction reaction (ORR) activity than that of ZnCo2O4/NCNTs and ZnMn2O4/NCNTs, supporting that the Co–O bond covalency determines the ORR activity of spinel ZnCo2O4. This study offers the competition between adjacent Co–O and Mn–O bonds via the BOh–O–BOh edge-sharing geometry. The ion substitution at octahedral sites by less electronegative cations can be a new and effective way to improve the electrocatalytic performance of cobalt-based spinel oxides. 相似文献
67.
Huimin Yu Deyu Wang Huanyu Jin Pan Wu Xuan Wu Dewei Chu Yi Lu Xiaofei Yang Haolan Xu 《Advanced functional materials》2023,33(24):2214828
Improving interfacial solar evaporation performance is crucial for the practical application of this technology in solar-driven seawater desalination. Lowering evaporation enthalpy is one of the most promising and effective strategies to significantly improve solar evaporation rate. In this study, a new pathway to lower vaporization enthalpy by introducing heterogeneous interactions between hydrophilic hybrid materials and water molecules is developed. 2D MoN1.2 nanosheets are synthesized and integrated with rGO nanosheets to form stacked MoN1.2-rGO heterostructures with massive junction interfaces for interfacial solar evaporation. Molecular dynamics simulation confirms that atomic thick 2D MoN1.2 and rGO in the MoN1.2-rGO heterostructures simultaneously interact with water molecules, while the interactions are remarkably different. These heterogeneous interactions cause an imbalanced water state, which easily breaks the hydrogen bonds between water molecules, leading to dramatically lowered vaporization enthalpy and improved solar evaporation rate (2.6 kg m−2 h−1). This study provides a promising strategy for designing 2D-2D heterostructures to regulate evaporation enthalpy to improve solar evaporate rate for clean water production. 相似文献
68.
Lingcai Zeng Haoyan Liang Bao Qiu Zhepu Shi Sijie Cheng Kaixiang Shi Quanbing Liu Zhaoping Liu 《Advanced functional materials》2023,33(25):2213260
Li-rich layered oxides (LLOs) have been considered as the most promising cathode materials for achieving high energy density Li-ion batteries. However, they suffer from continuous voltage decay during cycling, which seriously shortens the lifespan of the battery in practical applications. This review comprehensively elaborates and summarizes the state-of-the-art of the research in this field. It is started from the proposed mechanism of voltage decay that refers to the phase transition, microscopic defects, and oxygen redox or release. Furthermore, several strategies to mitigate the voltage decay of LLOs from different scales, such as surface modification, elemental doping, regulation of components, control of defect, and morphology design are summarized. Finally, a systematic outlook on the real root of voltage decay is provided, and more importantly, a potential solution to voltage recovery from electrochemistry. Based on this progress, some effective strategies with multiple scales will be feasible to create the conditions for their commercialization in the future. 相似文献
69.
Chengyun Zhang Min Ji Xilin Zhou Xiaohu Mi Huan Chen Baobao Zhang Zhengkun Fu Zhenglong Zhang Hairong Zheng 《Advanced functional materials》2023,33(2):2208561
All-optical responsive nanomaterials, which can rapidly switch between two stable states, have been regarded as the next-generation memories due to their potential to realize binary information storage and implement on-chip, integrated photonic neuromorphic systems. Rare earth oxides are preeminent candidates owing to their extraordinary luminescent stability and narrow optical transitions. However, due to the lack of simple and effective optical switches, it is difficult to realize all-optical data storage, encoding, and retrieval by pure rare earth-doped luminescent nanoparticles. Here, a rapid and high-contrast of 104 luminescent switching of Y2O3:Eu3+ nanoparticle between the enhancement and quenching states is achieved by employing the strong light confinement and ultrafast thermal response of localized surface plasmon resonance. A self-encrypted all-optical memory is presented with optical information writing, encryption, reading, and re-writing, and a high-sensitivity synaptic response of emitters to frequency and light intensity flux, which can be harnessed to encrypt information flows and promote convenient and high-security information encryption. Such a convenient and secure plasmonic thermally assisted self-encrypting luminescent switch paves the way for constructing high-performance stimuli-responsive rare earth oxide crystals on demand and expanding their applications in various data encryption, anti-counterfeiting, and rewritable colouration devices. 相似文献
70.
Congcong Cai Xinyuan Li Ping Hu Ting Zhu Jiantao Li Hao Fan Ruohan Yu Tianyi Zhang Sungsik Lee Liang Zhou Liqiang Mai 《Advanced functional materials》2023,33(24):2215155
Introducing anionic redox in layered oxides is an effective approach to breaking the capacity limit of conventional cationic redox. However, the anionic redox reaction generally suffers from excessive oxidation of lattice oxygen to O2 and O2 release, resulting in local structural deterioration and rapid capacity/voltage decay. Here, a Na0.71Li0.22Al0.05Mn0.73O2 (NLAM) cathode material is developed by introducing Al3+ into the transition metal (TM) sites. Thanks to the strong Al–O bonding strength and small Al3+ radius, the TMO2 skeleton and the holistic TM–O bonds in NLAM are comprehensively strengthened, which inhibits the excessive lattice oxygen oxidation. The obtained NLAM exhibits a high reversible capacity of 194.4 mAh g-1 at 20 mA g-1 and decent cyclability with 98.6% capacity retention over 200 cycles at 200 mA g−1. In situ characterizations reveal that the NLAM experiences phase transitions with an intermediate OP4 phase during the charge–discharge. Theoretical calculations further confirm that the Al substitution strategy is beneficial for improving the overlap between Mn 3d and O 2p orbitals. This finding sheds light on the design of layered oxide cathodes with highly reversible anionic redox for sodium storage. 相似文献