全文获取类型
收费全文 | 2541篇 |
免费 | 87篇 |
国内免费 | 22篇 |
专业分类
化学 | 1648篇 |
晶体学 | 9篇 |
力学 | 87篇 |
数学 | 441篇 |
物理学 | 465篇 |
出版年
2024年 | 2篇 |
2023年 | 18篇 |
2022年 | 50篇 |
2021年 | 111篇 |
2020年 | 69篇 |
2019年 | 119篇 |
2018年 | 110篇 |
2017年 | 79篇 |
2016年 | 97篇 |
2015年 | 107篇 |
2014年 | 89篇 |
2013年 | 153篇 |
2012年 | 153篇 |
2011年 | 188篇 |
2010年 | 138篇 |
2009年 | 116篇 |
2008年 | 154篇 |
2007年 | 157篇 |
2006年 | 129篇 |
2005年 | 125篇 |
2004年 | 108篇 |
2003年 | 63篇 |
2002年 | 63篇 |
2001年 | 32篇 |
2000年 | 20篇 |
1999年 | 18篇 |
1998年 | 22篇 |
1997年 | 18篇 |
1996年 | 19篇 |
1995年 | 19篇 |
1994年 | 10篇 |
1993年 | 14篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有2650条查询结果,搜索用时 156 毫秒
91.
92.
Dmitry I. Bugaenko Alexey A. Volkov Dr. Mikhail V. Livantsov Prof. Dr. Marina A. Yurovskaya Dr. Alexander V. Karchava 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(54):12502-12506
The visible-light-induced arylation of tertiary phosphines with aryl(mesityl)iodonium triflates to produce the quaternary phosphonium salts occurs under mild, metal, and catalyst-free conditions. Photo-excited EDA complexes between diaryliodonium salts and phosphines supposedly enable this transformation, which is difficult to achieve through the traditional ground-state reactions. Demonstrating high functional group tolerance, broad scope, and complete selectivity of the aryl group transfer, the method is particularly compatible with sterically congested phosphines, which are challenging under metal-based catalytic methods. 相似文献
93.
94.
Mikhail P. Koroteev Vitalii K. Belskii Anna R. Bekker Eduard E. Nifantyev 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract Previously we synthesized and examined in detail 1,2- alkylideneglucofuanose 3,5,6-bicyclophosphites; mono- and bicyclophosphates with peculiar chemical and physiological activity were obtained on their base [1]. During the study of their structural dependence, we modified the hydrocarbonic moiety, synthesiz-ed 1,2,3- and 3,5,6-bicyclophosphites and cyclophosphates of gulofuanose, and correlated their features with those of glucose analogues. Furthermore, an additional phosphonate moiety (obtained by a stereoselective reaction of an appropriate ketonic sugar with silylphosphites) was introduced into the glucofuranose 3,5,6-bicyclophosphite molecule to the third carbon atom. As a result, the monosaccharide matrix gained two functional groups containing tri- and fourcoordinated phosphorus. 相似文献
95.
Martin I. Kabachnik Tatyana A. Mastryukova Andrei B. Ou-Rwpin Mikhail I. Kadyko Pavel V. Petrovskii Erlen I. Fedin 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract The enantiomeric ratio in non-racemic mixtures of 2-anilino-2-oxo-1,3,2-oxazaphospho-rinane (I) and 3-(α-rnethylbenzyl)-(I)1 enantiomers was determined by measurement of the integral intensity ratio of two 31P-NMR signals, assigned to enantiomers and differentiated due to the effect of statistically controlled associate-diastereoisomerim (scada), 2 when association occurs under conditions of fast exchange. 相似文献
96.
97.
98.
99.
Dr. Zhijia Wang Mikhail Ivanov Dr. Yuting Gao Laura Bussotti Prof. Paolo Foggi Huimin Zhang Prof. Nino Russo Prof. Bernhard Dick Prof. Jianzhang Zhao Prof. Mariangela Di Donato Dr. Gloria Mazzone Prof. Liang Luo Prof. Matvey Fedin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(5):1091-1102
Spin–orbit charge-transfer intersystem crossing (SOCT-ISC) is useful for the preparation of heavy atom-free triplet photosensitisers (PSs). Herein, a series of perylene-Bodipy compact electron donor/acceptor dyads showing efficient SOCT-ISC is prepared. The photophysical properties of the dyads were studied with steady-state and time-resolved spectroscopies. Efficient triplet state formation (quantum yield ΦT=60 %) was observed, with a triplet state lifetime (τT=436 μs) much longer than that accessed with the conventional heavy atom effect (τT=62 μs). The SOCT-ISC mechanism was unambiguously confirmed by direct excitation of the charge transfer (CT) absorption band by using nanosecond transient absorption spectroscopy and time-resolved electron paramagnetic resonance (TREPR) spectroscopy. The factors affecting the SOCT-ISC efficiency include the geometry, the potential energy surface of the torsion, the spin density for the atoms of the linker, solvent polarity, and the energy matching of the 1CT/3LE states. Remarkably, these heavy atom-free triplet PSs were demonstrated as a new type of efficient photodynamic therapy (PDT) reagents (phototoxicity, EC50=75 nm ), with a negligible dark toxicity (EC50=78.1 μm ) compared with the conventional heavy atom PSs (dark toxicity, EC50=6.0 μm, light toxicity, EC50=4.0 nm ). This study provides in-depth understanding of the SOCT-ISC, unveils the design principles of triplet PSs based on SOCT-ISC, and underlines their application as a new generation of potent PDT reagents. 相似文献
100.