全文获取类型
收费全文 | 81940篇 |
免费 | 961篇 |
国内免费 | 754篇 |
专业分类
化学 | 27038篇 |
晶体学 | 834篇 |
力学 | 6932篇 |
综合类 | 23篇 |
数学 | 32405篇 |
物理学 | 16423篇 |
出版年
2023年 | 109篇 |
2022年 | 171篇 |
2021年 | 183篇 |
2020年 | 164篇 |
2019年 | 147篇 |
2018年 | 10529篇 |
2017年 | 10331篇 |
2016年 | 6233篇 |
2015年 | 1032篇 |
2014年 | 527篇 |
2013年 | 574篇 |
2012年 | 4088篇 |
2011年 | 10819篇 |
2010年 | 5833篇 |
2009年 | 6246篇 |
2008年 | 6830篇 |
2007年 | 8970篇 |
2006年 | 430篇 |
2005年 | 1479篇 |
2004年 | 1673篇 |
2003年 | 2104篇 |
2002年 | 1122篇 |
2001年 | 342篇 |
2000年 | 374篇 |
1999年 | 263篇 |
1998年 | 288篇 |
1997年 | 231篇 |
1996年 | 284篇 |
1995年 | 192篇 |
1994年 | 128篇 |
1993年 | 123篇 |
1992年 | 88篇 |
1991年 | 93篇 |
1990年 | 72篇 |
1989年 | 75篇 |
1988年 | 78篇 |
1987年 | 76篇 |
1986年 | 70篇 |
1985年 | 55篇 |
1984年 | 57篇 |
1983年 | 40篇 |
1982年 | 45篇 |
1981年 | 41篇 |
1980年 | 55篇 |
1979年 | 46篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Yijia Shao Zhiyuan Lu Luoqian Li Yanni Liu Lijun Yang Ting Shu Xiuhua Li Shijun Liao 《Molecules (Basel, Switzerland)》2022,27(7)
Lithium-rich manganese-based layered cathode materials are considered to be one of the best options for next-generation lithium-ion batteries, owing to their ultra-high specific capacity (>250 mAh·g−1) and platform voltage. However, their poor cycling stability, caused by the release of lattice oxygen as well as the electrode/electrolyte side reactions accompanying complex phase transformation, makes it difficult to use this material in practical applications. In this work, we suggest a molybdenum surface modification strategy to improve the electrochemical performance of Li1.2Mn0.54Ni0.13Co0.13O2. The Mo-modified Li1.2Mn0.54Ni0.13Co0.13O2 material exhibits an enhanced discharge specific capacity of up to 290.5 mAh·g−1 (20 mA·g−1) and a capacity retention rate of 82% (300 cycles at 200 mA·g−1), compared with 261.2 mAh·g−1 and a 70% retention rate for the material without Mo modification. The significantly enhanced performance of the modified material can be ascribed to the formation of a Mo-compound-involved nanolayer on the surface of the materials, which effectively lessens the electrolyte corrosion of the cathode, as well as the activation of Mo6+ towards Ni2+/Ni4+ redox couples and the pre-activation of a Mo compound. This study offers a facile and effective strategy to address the poor cyclability of lithium-rich manganese-based layered cathode materials. 相似文献
993.
Seddique M. Ahmed 《Journal of solution chemistry》2008,37(7):919-932
The chromaticity of poly(o-anisidine) (POAN) doped with different acids (HA), HA-doped POAN, has been studied by the spectrophotometric technique and
the results were substantiated by molecular mechanics (MM+) calculations. The observed absorbance decrease (λ around 720 nm, dark green coloration) with increasing concentration of the inorganic oxidizing agent (KMnO4) can be attributed to the oxidative hydrolysis mechanism. The oxidative hydrolysis constant (K
h) is highly dependent on the strength of the acid used. The HClO4-doped POAN matrix has the ability to store about 128.878 kJ⋅g−1 chromogenic energy (CE) at the wavelength 720 nm in a condensed lightweight form. MM+ calculations suggest that the potential
energy (PE) in kJ⋅mol−1 of the optimum molecular geometric (OMG) structure of the HClO4-doped POAN matrix is at least two (2.052) times more stable than the OMG of the base form (POAN-EB) of the POAN matrix. Kinetic
parameters of the oxidative hydrolysis reaction of the HA-doped POAN matrix were deduced from absorbance variations with time.
The results of computer-oriented kinetic analysis indicate that the rate-controlling step for HA-doped POAN oxidative hydrolysis
is governed by the Ginstling-Bronshein equation that represents three-dimensional diffusion (D4). Activation parameters for
the oxidative hydrolysis of the HClO4-doped POAN matrix were computed and discussed. 相似文献
994.
995.
996.
A density functional and ab initio theory investigation on M@B9 and M@B10 molecular wheels containing planar nona- and deca-coordinate heavy group 11, 12 and 13 metals (M=Ag, Au, Cd, Hg, In, Ti)
has been performed. These unusual clusters all prove to be true minima on the potential energy surfaces of the systems and
σ+π double aromatic in nature. The first two vertical one-electron detachment energies of M@B10− (M=Ag, Au) anions and first two ionization potentials of M@B9 (M=Ag, Au) and M@B10 (M=Cd, Hg) neutrals were calculated to aid future experiments. The cluster complexes designed in this work may expend the
domain of planar hyper-coordinate elements to include heavy group 11, 12, and 13 metals and serve as interesting candidates
to be targeted in experiments.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.
Supported by the National Natural Science Foundation of China (Grant No. 20873117) 相似文献
997.
It was found that the interface effects in viscous capillary flow influenced the process of viscosity measurement greatly,and the abnormal viscosity behaviors of polyelectrolytes as well as neutral polymers in dilute solution region were ascribed to interface effect.According to this theory,we have reviewed the previous viscosity data of derivatives of poly-2- vinylpyridine reported by Maclay and Fuoss first.Then,the abnormal viscosity behaviors of a series of sodium polystyrene sulfonate samples with various molecular weights in dilute aqueous solutions were studied further.The solute adsorption behaviors and structural information of polymers have been discussed carefully. 相似文献
998.
Anguo Ying Ming Zheng Haidan Xu Fangli Qiu Changhua Ge 《Research on Chemical Intermediates》2011,37(8):883-890
An efficient and facile protocol for aza-Michael addition of aliphatic and aromatic amines to electron-deficit alkenes using
[TMG][Lac] as catalyst under solvent-free conditions was established. 相似文献
999.
1000.
Jian-Kun Sun Linlin Zhang Liang Yue Tang Tang Wen-Jie Jiang Yun Zhang Zhenxiao Pan Xinhua Zhong Jin-Song Hu Li-Jun Wan 《中国科学:化学(英文版)》2018,61(10):1338-1344
Developing efficient counter electrodes (CEs) and quantum dots made of earth-abundant and non-toxic elements is essential but still challenging for quantum dot-sensitized solar cells (QDSSCs). Here, we report a facile strategy to prepare self-supported and robust CoS2 and NiS nanocrystals-assembled nanosheets directly grown on carbon paper (MSx NS@CP) as efficient counter electrodes for QDSSCs. Such CEs integrate the merits of fast electron transfer from interconnected conductive scaffold, efficient mass transfer from hierarchically vertical nanosheet on 3D open substrate, as well as abundant highly active catalytic sites from metal sulphide nanocrystal units. As a result, QDDSCs based on such CoS2 NS@CP and NiS NS@CP CEs achieve a PCE of 8.88% and 7.53%, respectively. The detailed analyses suggest that CoS2 NS@CP has the highest catalytic activity and shows the lowest charger transfer resistance, leading to the highest PCE. These findings may inspire the design and exploration of other self-supported efficient CEs by integrating highly active catalysts onto 3D conductive networks for efficient QDSSCs. 相似文献