全文获取类型
收费全文 | 666篇 |
免费 | 153篇 |
国内免费 | 106篇 |
专业分类
化学 | 464篇 |
晶体学 | 11篇 |
力学 | 39篇 |
综合类 | 16篇 |
数学 | 68篇 |
物理学 | 327篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 7篇 |
2020年 | 23篇 |
2019年 | 14篇 |
2018年 | 10篇 |
2017年 | 14篇 |
2016年 | 22篇 |
2015年 | 27篇 |
2014年 | 30篇 |
2013年 | 51篇 |
2012年 | 59篇 |
2011年 | 60篇 |
2010年 | 57篇 |
2009年 | 43篇 |
2008年 | 68篇 |
2007年 | 45篇 |
2006年 | 38篇 |
2005年 | 35篇 |
2004年 | 31篇 |
2003年 | 44篇 |
2002年 | 54篇 |
2001年 | 49篇 |
2000年 | 28篇 |
1999年 | 29篇 |
1998年 | 15篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1966年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有925条查询结果,搜索用时 31 毫秒
1.
Journal of Optimization Theory and Applications - In this paper, we investigate an inexact quasisubgradient method with extrapolation for solving a quasiconvex optimization problem with a closed,... 相似文献
2.
Ye Xu Dr. Huifeng Yao Lijiao Ma Ling Hong Jiayao Li Qing Liao Yunfei Zu Jingwen Wang Mengyuan Gao Prof. Long Ye Prof. Jianhui Hou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):9089-9095
Decreasing the energy loss is one of the most feasible ways to improve the efficiencies of organic photovoltaic (OPV) cells. Recent studies have suggested that non-radiative energy loss ( ) is the dominant factor that hinders further improvements in state-of-the-art OPV cells. However, there is no rational molecular design strategy for OPV materials with suppressed . Herein, taking molecular surface electrostatic potential (ESP) as a quantitative parameter, we establish a general relationship between chemical structure and intermolecular interactions. The results reveal that increasing the ESP difference between donor and acceptor will enhance the intermolecular interaction. In the OPV cells, the enhanced intermolecular interaction will increase the charge-transfer (CT) state ratio in its hybridization with the local exciton state to facilitate charge generation, but simultaneously result in a larger . These results suggest that finely tuning the ESP of OPV materials is a feasible method to further improve the efficiencies of OPV cells. 相似文献
3.
Yao Xiao Yan‐Fang Zhu Wei Xiang Zhen‐Guo Wu Yong‐Chun Li Jing Lai Shi Li Enhui Wang Zu‐Guang Yang Chun‐Liu Xu Ben‐He Zhong Xiao‐Dong Guo 《Angewandte Chemie (International ed. in English)》2020,59(4):1491-1495
Demands for large‐scale energy storage systems have driven the development of layered transition‐metal oxide cathodes for room‐temperature rechargeable sodium ion batteries (SIBs). Now, an abnormal layered‐tunnel heterostructure Na0.44Co0.1Mn0.9O2 cathode material induced by chemical element substitution is reported. By virtue of beneficial synergistic effects, this layered‐tunnel electrode shows outstanding electrochemical performance in sodium half‐cell system and excellent compatibility with hard carbon anode in sodium full‐cell system. The underlying formation process, charge compensation mechanism, phase transition, and sodium‐ion storage electrochemistry are clearly articulated and confirmed through combined analyses of in situ high‐energy X‐ray diffraction and ex situ X‐ray absorption spectroscopy as well as operando X‐ray diffraction. This crystal structure engineering regulation strategy offers a future outlook into advanced cathode materials for SIBs. 相似文献
4.
5.
Bingjie Chen Dr. Lianhai Zu Dr. Yao Liu Dr. Ruijing Meng Yutong Feng Prof. Chengxin Peng Feng Zhu Tianzi Hao Jiajia Ru Prof. Yonggang Wang Prof. Jinhu Yang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(8):3161-3166
Incorporating nanoscale Si into a carbon matrix with high dispersity is desirable for the preparation of lithium-ion batteries (LIBs) but remains challenging. A space-confined catalytic strategy is proposed for direct superassembly of Si nanodots within a carbon (Si NDs⊂C) framework by copyrolysis of triphenyltin hydride (TPT) and diphenylsilane (DPS), where Sn atomic clusters created from TPT pyrolysis serve as the catalyst for DPS pyrolysis and Si catalytic growth. The use of Sn atomic cluster catalysts alters the reaction pathway to avoid SiC generation and enable formation of Si NDs with reduced dimensions. A typical Si NDs⊂C framework demonstrates a remarkable comprehensive performance comparable to other Si-based high-performance half LIBs, and higher energy densities compared to commercial full LIBs, as a consequence of the high dispersity of Si NDs with low lithiation stress. Supported by mechanic simulations, this study paves the way for construction of Si/C composites suitable for applications in future energy technologies. 相似文献
6.
Meng Wen Zu‐Ping Xiao Chun‐Ya Wang Xi‐He Huang 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(2):136-139
The title compound, {[Zn4(C8H4O4)3(OH)2(C12H6N2O2)2]·2H2O}n, has been prepared hydrothermally by the reaction of Zn(NO3)2·6H2O with benzene‐1,4‐dicarboxylic acid (H2bdc) and 1,10‐phenanthroline‐5,6‐dione (pdon) in H2O. In the crystal structure, a tetranuclear Zn4(OH)2 fragment is located on a crystallographic inversion centre which relates two subunits, each containing a [ZnN2O4] octahedron and a [ZnO4] tetrahedron bridged by a μ3‐OH group. The pdon ligand chelates to zinc through its two N atoms to form part of the [ZnN2O4] octahedron. The two crystallographically independent bdc2− ligands are fully deprotonated and adopt μ3‐κO:κO′:κO′′ and μ4‐κO:κO′:κO′′:κO′′′ coordination modes, bridging three or four ZnII cations, respectively, from two Zn4(OH)2 units. The Zn4(OH)2 fragment connects six neighbouring tetranuclear units through four μ3‐bdc2− and two μ4‐bdc2− ligands, forming a three‐dimensional framework with uninodal 6‐connected α‐Po topology, in which the tetranuclear Zn4(OH)2 units are considered as 6‐connected nodes and the bdc2− ligands act as linkers. The uncoordinated water molecules are located on opposite sides of the Zn4(OH)2 unit and are connected to it through hydrogen‐bonding interactions involving hydroxide and carboxylate groups. The structure is further stabilized by extensive π–π interactions between the pdon and μ4‐bdc2− ligands. 相似文献
7.
Lianghui Gao Mengjie Gong Fanbo Kong Ting Yuan Xiaohong Li Lili Zu Yunchao Li Louzhen Fan 《大学化学》2020,35(5):81-87
During the fight against the new coronavirus epidemic, the "Physical Chemistry" team of Beijing Normal University used various network platforms and tools, such as MOOC of China University, Rain Classroom and WeChat Group in the teaching process. The exploration and practice of online learning of "Physical Chemistry" is carried out based on MOOC teaching, with student learning as the center and teacher guidance as the support. Taking the most difficult chapter of "fundamentals for statistical thermodynamic" as an example, we designed a complex teaching program that includes previews, watching MOOC videos in class, real-time online exercises, teachers' answers, and after-class reflection and questioning. The students were encouraged to learn independently through the reserved information, designed activities and assignments. Practice shows that the online course has cultivated the students' self-management ability, trained their critical thinking skills, and achieved good teaching results. 相似文献
8.
Hong‐Xin Tang Yu‐Xiao Zhang Chao Zhuo Rui‐Biao Fu Hua Lin Zu‐Ju Ma Xin‐Tao Wu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):3864-3868
A novel niobium oxyiodate sulfate, Nb2O3(IO3)2 (SO4), was fabricated by a rational multi‐component design under moderate hydrothermal conditions. This multi‐component design is inspired by an interesting niobium oxysulfate reaction, which opens a new door for synthetic method to effectively introduce refractory metals such as Nb into crystal structures by hydrothermal synthesis. Nb2O3(IO3)2(SO4) features a cube‐like topological structure with a large phase‐matching second harmonic generation (SHG) response (6×KDP), a wide transparency window (0.38–8 μm), and a high laser damage threshold (LDT) (20×AgGaS2). It has the highest thermostability (stable up to 580 °C under air) among reported non‐centrosymmetric (NCS) iodates and sulfates and is stable in water and even concentrated H2SO4. Furthermore, Nb2O3(IO3)2(SO4) is a unique nonlinear optical (NLO) material among iodates and sulfates, because its SHG effect is mainly caused by the MO6 units rather than the IO3 or SO4 units, which is demonstrated by density functional theory (DFT) calculations. 相似文献
9.
Yao‐Zu Zhang Dong‐Sheng Sun Ji‐Xing Gao Xiu‐Ni Hua Xiao‐Gang Chen Guang‐Quan Mei Wei‐Qiang Liao 《化学:亚洲杂志》2019,14(7):1028-1033
Piezoelectric materials are a class of important functional materials applied in high‐voltage sources, sensors, vibration reducers, actuators, motors, and so on. Herein, [(CH3)3S]3[Bi2Br9]( 1 ) is a brilliant semiconducting organic–inorganic hybrid perovskite‐type non‐ferroelectric piezoelectric with excellent piezoelectricity. Strikingly, the value of the piezoelectric coefficient d33 is estimated as ≈18 pC N?1. Such a large piezoelectric coefficient in non‐ferroelectric piezoelectric has been scarcely reported and is comparable with those of typically one‐composition non‐ferroelectric piezoelectrics such as ZnO (3pC N?1) and much greater than those of most known typical materials. In addition, 1 exhibits semiconducting behavior with an optical band gap of ≈2.58 eV that is lower than the reported value of 3.37 eV for ZnO. This discovery opens a new avenue to exploit molecular non‐ferroelectric piezoelectric and should stimulate further exploration of non‐ferroelectric piezoelectric due to their high stability and low loss characteristics. 相似文献
10.
Ma Lijiao Xu Ye Zu Yunfei Liao Qing Xu Bowei An Cunbin Zhang Shaoqing Hou Jianhui 《中国科学:化学(英文版)》2020,63(1):21-27
In order to meet the requirements for making organic solar cells(OSCs) through solution printing techniques, great efforts have been devoted into developing high performance OSCs with relatively thicker active layers. In this work, a thick-film(300 nm)ternary OSC with a power conversion efficiency of 14.3% is fabricated by introducing phenyl-C_(61)-butyric-acid-methyl ester(PC_(61)BM) into a PBDB-T-2Cl:BTP-4 F host blend. The addition of PC_(61)BM is found to be helpful for improving the hole and electron mobilities, and thus facilitates charge transport as well as suppresses charge recombination in the active layers, leading to the improved efficiencies of OSCs with relatively thicker active layers. Our results demonstrate the feasibility of employing fullerene derivative PC_(61)BM to construct a high-efficiency thick-film ternary device, which would promote the development of thick layer ternary OSCs to fulfill the requirements of future roll to roll production. 相似文献