全文获取类型
收费全文 | 474篇 |
免费 | 26篇 |
专业分类
化学 | 415篇 |
晶体学 | 4篇 |
力学 | 6篇 |
数学 | 36篇 |
物理学 | 39篇 |
出版年
2023年 | 5篇 |
2022年 | 18篇 |
2021年 | 24篇 |
2020年 | 15篇 |
2019年 | 14篇 |
2018年 | 10篇 |
2017年 | 15篇 |
2016年 | 25篇 |
2015年 | 13篇 |
2014年 | 24篇 |
2013年 | 29篇 |
2012年 | 30篇 |
2011年 | 34篇 |
2010年 | 17篇 |
2009年 | 25篇 |
2008年 | 35篇 |
2007年 | 16篇 |
2006年 | 21篇 |
2005年 | 31篇 |
2004年 | 24篇 |
2003年 | 15篇 |
2002年 | 8篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1985年 | 1篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1969年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有500条查询结果,搜索用时 15 毫秒
401.
Bogdan Czajka Michał Zieliński Maria Wojciechowska Iwona Tomska-Foralewska 《Journal of Solid State Electrochemistry》2014,18(8):2351-2358
This paper describes the synthesis and texture of the MgF2-MgO system used as an immobilizing agent of the electrolyte (KCl-LiCl-RbCl) for high-temperature cells. Preparations containing 20 and 40 mol% MgF2 were characterized by a mesoporous structure and large specific surface areas. It was demonstrated that pellets containing 40–50 mas.% of MgF2-MgO immobilizing agent were good electrolyte immobilizers. The ionic conductivity of pellets investigated in this work ranged from 0.02 to 0.04 S/cm, and it was about 20 times lower than the value set for the pure electrolyte. The difference is due to the tortuosity of the pellet. This mixture remains dimensionally stable at 400 °C and under 60 kPa and reveals good ionic conductivity during tests in a model cell with a 1.32-Ω resistor. During the discharge of the cell, it was observed that the voltage was not less than 1.5 V and current more than 1 A for approximately 100 s. No leakage of the electrolyte was observed. 相似文献
402.
Kamil Sokołowski Dr. Wojciech Bury Adam Tulewicz Anna M. Cieślak Dr. Iwona Justyniak Dominik Kubicki Elżbieta Krajewska Prof. Anne Milet Prof. Robert Moszyński Prof. Janusz Lewiński 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5496-5503
Organozinc hydroxides, RZnOH, possessing the proton‐reactive alkylzinc group and the CO2‐reactive Zn?OH group, represent an intriguing group of organometallic precursors for the synthesis of novel zinc carbonates. Comprehensive experimental and computational investigations on 1) solution and solid‐state behavior of tBuZnOH ( 1 ) species in the presence of Lewis bases, namely, THF and 4‐methylpyridine; 2) step‐by‐step sequence of the reaction between 1 and CO2; and 3) the effect of a donor ligand and/or an excess of tBu2Zn as an external proton acceptor on the reaction course are reported. DFT calculations for the insertion of carbon dioxide into the dinuclear alkylzinc hydroxide 1 2 are fully consistent with 1H NMR spectroscopy studies and indicate that this process is a multistep reaction, in which the insertion of CO2 seems to be the rate‐determining step. Moreover, DFT studies show that the mechanism of the rearrangement between key intermediates, that is, the primary alkylzinc bicarbonate with a proximal position of hydrogen and the secondary alkylzinc bicarbonate with a distal position of hydrogen, most likely proceeds through internal rotation of the dinuclear bicarbonate. 相似文献
403.
404.
405.
Atomic force microscopy (AFM) was used to measure single interaction forces between corrole (host) and phenol derivatives (guests) in aqueous media. A gold tip was modified with thiol derivatives of corrole via the Au–S covalent bond. Such a tip was used to measure adhesion forces with a planar gold substrate modified with thiol derivatives of phenol and ortho-nitrophenol in aqueous solutions. The mean force between the corrole and ortho-nitrophenol was higher than that between corrole and phenol, probably reflecting stronger hydrogen bond interaction in the former complex. In the presence of a supporting electrolyte (0.1 M K2SO4), the mean force increased, suggesting that electrostatic and π–π interactions play an essential role in the adhesion force. In addition, the adhesion force measured at pH 6.0 was larger than that at pH 10, reflecting the electrostatic repulsion at the higher pH. These behaviours are consistent with the potentiometric responses of a liquid membrane based on corrole to phenolic compounds. Also, the values of forces for the interaction between corrole and phenol derivatives showed the same tendency as energy calculated for these complexes. The Poisson method was used for the calculation of the single force of the chemical bond between the corrole host and the phenolic guests. 相似文献
406.
Iwona Dams Michał Chodyński Małgorzata Krupa Anita Pietraszek Marta Zezula Piotr Cmoch Monika Kosińska Andrzej Kutner 《Tetrahedron》2013,69(5):1634-1648
The 16-(3-trifluoromethyl)phenoxy PGF2α analogue travoprost (8a) has potent topical ocular activity. A novel convergent synthesis of 13,14-en-15-ol PGF2α analogues was developed employing Julia–Lythgoe olefination of the structurally advanced prostaglandin phenylsulfone (5Z)-(+)-15 with a new enantiomerically pure aldehyde ω-chain synthon (S)-(?)-16a. Subsequent hydrolysis of protecting groups and final esterification of fluprostenol (7a) yielded travoprost (8a). The main advantages are the preparation of high purity travoprost (8a) and the application of comparatively cheap reagents. The novel convergent strategy allows the synthesis of a whole series of 13,14-en-15-ol PGF2α analogues from a common and structurally advanced prostaglandin intermediate 15. The preparation and identification of two synthetic impurities, 15-epi isomer (8b) of travoprost and a new prostaglandin related ester (5Z)-(+)-18, are also described. 相似文献
407.
Dariusz Wyrzykowski Iwona Inkielewicz‐Stępniak Justyna Czupryniak Dagmara Jacewicz Tadeusz Ossowski Michal Woźniak Lech Chmurzyński 《无机化学与普通化学杂志》2013,639(10):1795-1799
The reactivity of superoxide free radicals (O2 · –) generated electrochemically towards the oxydiacetate metal complexes, namely [VO(oda)(H2O)2], [Co(oda)(H2O)2] · H2O, and [Ni(oda)(H2O)3] · 1.5H2O (oda = oxydiacetate) was examined by cyclic voltammetry. The measurements were carried out in DMSO solution using a platinum electrode. Based on the height of the anodic peak Ea that corresponds to electrochemical oxidation O2 · – → O2 + e, in the absence and in the presence of the compounds in the mixture, their O2 · – scavenge ability was assessed. The influence of the type of the complex was briefly discussed. H2O2 was used to induce cellular injury in a mouse hippocampal cell line (HT22). The cytoprotection of chemical compounds was tested at the mitochondrial (MTT test) and plasma membrane level (LDH leakage). Dose‐dependent effect (10 and 100 μM of the complex) of investigated compounds was observed. 相似文献
408.
Radosaw Kotuniak Marc J. F. Strampraad Karolina Bossak‐Ahmad Urszula E. Wawrzyniak Iwona Ufnalska Peter‐Leon Hagedoorn Wojciech Bal 《Angewandte Chemie (International ed. in English)》2020,59(28):11234-11239
The amino‐terminal copper and nickel/N‐terminal site (ATCUN/NTS) present in proteins and bioactive peptides exhibits high affinity towards CuII ions and have been implicated in human copper physiology. Little is known, however, about the rate and exact mechanism of formation of such complexes. We used the stopped‐flow and microsecond freeze‐hyperquenching (MHQ) techniques supported by steady‐state spectroscopic and electrochemical data to demonstrate the formation of partially coordinated intermediate CuII complexes formed by glycyl–glycyl–histidine (GGH) peptide, the simplest ATCUN/NTS model. One of these novel intermediates, characterized by two‐nitrogen coordination, t1/2≈100 ms at pH 6.0 and the ability to maintain the CuII/CuI redox pair is the best candidate for the long‐sought reactive species in extracellular copper transport. 相似文献
409.
Radosław Kotuniak Marc J. F. Strampraad Karolina Bossak-Ahmad Dr. Urszula E. Wawrzyniak Iwona Ufnalska Dr. Peter-Leon Hagedoorn Prof. Wojciech Bal 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(28):11330-11335
The amino-terminal copper and nickel/N-terminal site (ATCUN/NTS) present in proteins and bioactive peptides exhibits high affinity towards CuII ions and have been implicated in human copper physiology. Little is known, however, about the rate and exact mechanism of formation of such complexes. We used the stopped-flow and microsecond freeze-hyperquenching (MHQ) techniques supported by steady-state spectroscopic and electrochemical data to demonstrate the formation of partially coordinated intermediate CuII complexes formed by glycyl–glycyl–histidine (GGH) peptide, the simplest ATCUN/NTS model. One of these novel intermediates, characterized by two-nitrogen coordination, t1/2≈100 ms at pH 6.0 and the ability to maintain the CuII/CuI redox pair is the best candidate for the long-sought reactive species in extracellular copper transport. 相似文献
410.
Grabowska Katarzyna Grabowski Janusz Ravanpak Zohreh 《Annals of Global Analysis and Geometry》2022,62(1):235-284
Annals of Global Analysis and Geometry - Motivated by properties of higher tangent lifts of geometric structures, we introduce concepts of weighted structures for various geometric objects on a... 相似文献