全文获取类型
收费全文 | 1284篇 |
免费 | 124篇 |
国内免费 | 2篇 |
专业分类
化学 | 1163篇 |
晶体学 | 17篇 |
力学 | 10篇 |
数学 | 30篇 |
物理学 | 190篇 |
出版年
2023年 | 14篇 |
2022年 | 19篇 |
2021年 | 41篇 |
2020年 | 37篇 |
2019年 | 61篇 |
2018年 | 50篇 |
2017年 | 26篇 |
2016年 | 51篇 |
2015年 | 56篇 |
2014年 | 61篇 |
2013年 | 100篇 |
2012年 | 134篇 |
2011年 | 139篇 |
2010年 | 61篇 |
2009年 | 40篇 |
2008年 | 90篇 |
2007年 | 76篇 |
2006年 | 52篇 |
2005年 | 55篇 |
2004年 | 46篇 |
2003年 | 40篇 |
2002年 | 33篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1988年 | 4篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1968年 | 3篇 |
1967年 | 5篇 |
1966年 | 2篇 |
排序方式: 共有1410条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
995.
Nojima A. Sawaya K. Adachi S. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1989,17(6):880-883
Two-dimensional finite-element analysis is performed for ion-cyclotron range of frequency (ICRF) antennas with various cross-sectional configurations. Interest is mainly focused on the quantitative difference in the input impedance among various antennas such as the normal loop antenna, the antenna with surrounding limiter walls, and the antenna buried into the cutoff cavity. For analytical simplicity, the cold plasma approximation is used. The numerical results show how the input impedance is affected by the presence of the limiter walls or the cutoff cavity. The code described can be applied to the designs of ICRF antennas with a wide range of plasma parameters and antenna geometries 相似文献
996.
Synthesis of π‐conjugated network polymers based on fluoroarene and fluorescent units via direct arylation polycondensation and their porosity and fluorescent properties
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Shotaro Hayashi Yuki Togawa Shin‐Ichi Yamamoto Toshio Koizumi Koji Nishi Atsushi Asano 《Journal of polymer science. Part A, Polymer chemistry》2017,55(23):3862-3867
In this study, we report the synthesis of π‐conjugated network polymers including unique fluorescent units via palladium‐catalyzed direct (C? H) arylation polycondensation of 1,2,4,5‐tetrafluorobenzene with tetrabromoarenes. The obtained polymers, including tetraphenylethene (TPE) or pyrene (PYR) units, had microporous structures with the specific Brunauer–Emmett–Teller (BET) surface areas at 508 and 824 m2 g?1, respectively. These polymers possessed narrow pore distributions (<15 nm). These analyses supported that π‐conjugated microporous polymers (CMPs) were synthesized by the direct arylation. Similar to the result of BET surface areas, carbon capture capacity of CMP based on PYR unit was higher than that of CMP based on TPE unit. Because the nitrogen capture capacity of these CMPs was low (≈ 0), selectivity of carbon dioxide adsorption was very high. TPE is a typical aggregation‐induced emission unit but PYR is an aggregation‐caused quenching (ACQ) molecule. The incorporation of TPE unit into the microporous polymer gave green‐colored fluorescence (Φ = 0.12). The polymer including PYR units also showed the green‐colored fluorescence (Φ = 0.05) even though the ACQ property. These synthesized CMPs exhibited characteristic solvatofluorochromism. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3862–3867 相似文献
997.
998.
999.
Absolute configuration of miyakosyne A at its isolated branched methyl stereogenic center has been studied by chemical degradation in combination with esterification with the Ohrui's acid. Comparison of the 1H NMR data of the relevant diesters for the degradation product and the synthetic standards indicated the 14R-configuration. 相似文献
1000.
Hiroyuki Takemura Maiko Nagaoka Chihiro Kawasaki Kasumi Tokumoto Noriko Tobita Yuki Takano Tetsuo Iwanaga 《Tetrahedron letters》2017,58(11):1066-1070
A cage compound was synthesized in order to investigate the structure and cation-π interactions of the metal ion complex. The multi-step synthesis was achieved starting from trimesic acid triethyl ester. In solution, a completely symmetrical structure that was anticipated by the molecular design was observed by 1H and 13C NMR spectroscopy. However, in the solid state, X-ray crystallographic analysis revealed that the compound had a collapsed structure. 相似文献