全文获取类型
收费全文 | 1559篇 |
免费 | 47篇 |
国内免费 | 9篇 |
专业分类
化学 | 860篇 |
晶体学 | 8篇 |
力学 | 31篇 |
数学 | 310篇 |
物理学 | 406篇 |
出版年
2023年 | 10篇 |
2021年 | 14篇 |
2020年 | 29篇 |
2019年 | 28篇 |
2018年 | 25篇 |
2017年 | 12篇 |
2016年 | 41篇 |
2015年 | 38篇 |
2014年 | 42篇 |
2013年 | 77篇 |
2012年 | 81篇 |
2011年 | 106篇 |
2010年 | 61篇 |
2009年 | 41篇 |
2008年 | 84篇 |
2007年 | 87篇 |
2006年 | 78篇 |
2005年 | 77篇 |
2004年 | 65篇 |
2003年 | 55篇 |
2002年 | 60篇 |
2001年 | 14篇 |
2000年 | 13篇 |
1999年 | 13篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 18篇 |
1995年 | 14篇 |
1994年 | 13篇 |
1993年 | 17篇 |
1992年 | 17篇 |
1991年 | 18篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 11篇 |
1984年 | 23篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1979年 | 13篇 |
1978年 | 10篇 |
1977年 | 20篇 |
1976年 | 10篇 |
1975年 | 13篇 |
1974年 | 23篇 |
1973年 | 12篇 |
排序方式: 共有1615条查询结果,搜索用时 15 毫秒
1.
2.
Dr. Long Zhao Dr. Bo Xu Dr. Utuq Ablikim Dr. Wenchao Lu Dr. Musahid Ahmed Mikhail M. Evseev Prof. Dr. Eugene K. Bashkirov Prof. Dr. Valeriy N. Azyazov A. Hasan Howlader Prof. Dr. Stanislaw F. Wnuk Prof. Dr. Alexander M. Mebel Prof. Dr. Ralf I. Kaiser 《Chemphyschem》2019,20(6):791-797
For the last decades, the hydrogen-abstraction−acetylene-addition (HACA) mechanism has been widely invoked to rationalize the high-temperature synthesis of PAHs as detected in carbonaceous meteorites (CM) and proposed to exist in the interstellar medium (ISM). By unravelling the chemistry of the 9-phenanthrenyl radical ([C14H9].) with vinylacetylene (C4H4), we present the first compelling evidence of a barrier-less pathway leading to a prototype tetracyclic PAH – triphenylene (C18H12) – via an unconventional hydrogen abstraction–vinylacetylene addition (HAVA) mechanism operational at temperatures as low as 10 K. The barrier-less, exoergic nature of the reaction reveals HAVA as a versatile reaction mechanism that may drive molecular mass growth processes to PAHs and even two-dimensional, graphene-type nanostructures in cold environments in deep space thus leading to a better understanding of the carbon chemistry in our universe through the untangling of elementary reactions on the most fundamental level. 相似文献
3.
Tong Su Yafei Wang Yi Liu William G. Branton Eugene Asahchop Christopher Power Bei Jiang Linglong Kong Niansheng Tang 《Entropy (Basel, Switzerland)》2020,22(11)
Distance weighted discrimination (DWD) is an appealing classification method that is capable of overcoming data piling problems in high-dimensional settings. Especially when various sparsity structures are assumed in these settings, variable selection in multicategory classification poses great challenges. In this paper, we propose a multicategory generalized DWD (MgDWD) method that maintains intrinsic variable group structures during selection using a sparse group lasso penalty. Theoretically, we derive minimizer uniqueness for the penalized MgDWD loss function and consistency properties for the proposed classifier. We further develop an efficient algorithm based on the proximal operator to solve the optimization problem. The performance of MgDWD is evaluated using finite sample simulations and miRNA data from an HIV study. 相似文献
4.
Panpan Li Quanbin Liang Eugene Yau-Hin Hong Chin-Yiu Chan Yat-Hin Cheng Ming-Yi Leung Mei-Yee Chan Kam-Hung Low Hongbin Wu Vivian Wing-Wah Yam 《Chemical science》2020,11(42):11601
A class of acceptor–donor–acceptor chromophoric small-molecule non-fullerene acceptors, 1–4, with difluoroboron(iii) β-diketonate (BF2bdk) as the electron-accepting moiety has been developed. Through the variation of the central donor unit and the modification on the peripheral substituents of the terminal BF2bdk acceptor unit, their photophysical and electrochemical properties have been systematically studied. Taking advantage of their low-lying lowest unoccupied molecular orbital energy levels (from −3.65 to −3.72 eV) and relatively high electron mobility (7.49 × 10−4 cm2 V−1 s−1), these BF2bdk-based compounds have been employed as non-fullerene acceptors in organic solar cells with maximum power conversion efficiencies of up to 4.31%. Moreover, bistable resistive memory characteristics with charge-trapping mechanisms have been demonstrated in these BF2bdk-based compounds. This work not only demonstrates for the first time the use of a boron(iii) β-diketonate unit in constructing non-fullerene acceptors, but also provides more insights into designing organic materials with multi-functional properties.Boron(iii) β-diketonates have been demonstrated to serve as multi-functional materials in NFA-based OPVs and organic resistive memories. 相似文献
5.
6.
7.
8.
9.
Postnikov Eugene B. Pikalov Ivan Yu. Chora̧żewski Mirosław 《Journal of solution chemistry》2022,51(11):1311-1333
Journal of Solution Chemistry - Recently ionic liquids have been considered as prospective substances for application as heat transfer fluids, which requires accurate knowledge of their thermal... 相似文献
10.
Observation of the multiple halogenation of peptides in the electrospray ionization source 下载免费PDF全文
Yury Kostyukevich Ekaterina Zhdanova Alexey Kononikhin Igor Popov Eugene Kukaev Eugene Nikolaev 《Journal of mass spectrometry : JMS》2015,50(7):899-905
The chlorination of peptides and proteins is an important posttranslational modification, which is a physiological signature of an enzyme myeloperoxidase and can serve as a potential biomarker of some diseases (Parkinson's disease, Alzheimer's disease, etc.). The quantification of the chlorinated peptides has been very challenging in part due to their low levels and artifacts associated with sample preparation. One of the most convenient and promising methods to detect and investigate the chlorinated peptides in the biological samples is the electrospray ionization (ESI) mass spectrometry coupled to the fragmentation techniques (collision‐induced dissociation and electron capture dissociation/electron transfer dissociation). We have shown that if the chlorine anions are present in the solution, then the peptide can undergo the chlorination during the ESI ionization. The effect was found to depend on the values of electric potentials of metal parts of the ESI interface. It was found that the grounding of ESI syringe results in the formation of an additional electric loop leading to the electrolytic production of Cl2 and as a consequence the hypochlorous acid inside the ESI needle. Hypochlorous acid reacts with amino groups of peptides and proteins producing chloramine or causing the protein cleavage. In the paper, it is shown on the example of the solution of the several peptides in the presence of HCl that by manipulating the ESI syringe potential, it is possible to create complexes with up to five Cl atoms for sample peptides when the ESI is operated in the positive mode. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献