全文获取类型
收费全文 | 1857篇 |
免费 | 76篇 |
国内免费 | 9篇 |
专业分类
化学 | 1281篇 |
晶体学 | 14篇 |
力学 | 26篇 |
数学 | 117篇 |
物理学 | 504篇 |
出版年
2023年 | 18篇 |
2022年 | 14篇 |
2021年 | 23篇 |
2020年 | 26篇 |
2019年 | 33篇 |
2018年 | 24篇 |
2017年 | 17篇 |
2016年 | 49篇 |
2015年 | 41篇 |
2014年 | 43篇 |
2013年 | 86篇 |
2012年 | 89篇 |
2011年 | 117篇 |
2010年 | 59篇 |
2009年 | 62篇 |
2008年 | 109篇 |
2007年 | 103篇 |
2006年 | 92篇 |
2005年 | 97篇 |
2004年 | 67篇 |
2003年 | 58篇 |
2002年 | 43篇 |
2001年 | 40篇 |
2000年 | 44篇 |
1999年 | 27篇 |
1998年 | 17篇 |
1997年 | 18篇 |
1996年 | 29篇 |
1995年 | 10篇 |
1994年 | 20篇 |
1993年 | 21篇 |
1992年 | 26篇 |
1991年 | 17篇 |
1990年 | 22篇 |
1989年 | 33篇 |
1988年 | 29篇 |
1987年 | 23篇 |
1986年 | 28篇 |
1985年 | 27篇 |
1984年 | 31篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 24篇 |
1980年 | 17篇 |
1978年 | 21篇 |
1977年 | 12篇 |
1976年 | 18篇 |
1975年 | 20篇 |
1973年 | 16篇 |
1969年 | 9篇 |
排序方式: 共有1942条查询结果,搜索用时 453 毫秒
91.
Rumiko Sakurai Kenichi Sakai Koichi Kodama Masanori Yamaura 《Tetrahedron: Asymmetry》2012,23(3-4):221-224
A useful key intermediate for the dipeptidyl peptidase-4 (DPP-4) inhibitor, 3-aminopiperidine 1, was successfully resolved with an enantiomerically pure resolving agent, N-tosyl-(S)-phenylalanine 2, to give both stereoisomers (R)-1 and (S)-1 as a less-soluble diastereomeric salt with (S)-2, via a dielectrically controlled resolution (DCR) phenomenon. 相似文献
92.
Hiroshi Sakai Takashi Yamazaki Nobuya Machida Toshihiko Shigematsu Saburo Nasu 《Molecular Crystals and Liquid Crystals》2013,570(2):105-110
Abstract Mössbauer spectra of the FePS3-cobaltocene intercalation compound were measured in the temperature range of 300K to 10K. The spectra, distinct from those of pure FePS3, suggest the charge transfer from cobaltocene to Fe-S antibonding orbitals of the FePS3 host lattice. 相似文献
93.
We have developed a Cd2+ fluorescent chemosensor with high selectivity as well as sensitivity by tethering a 4,7-bis(2-hydroxyethyl)-9-hydroxy-1,4,7-triazanonyl chelator to anthracene. This sensor features the ability to discriminate Cd2+ from Zn2+ to a high degree (KdZn/KdCd = 560) in a pH 7.2 buffer. 相似文献
94.
Hideki Misaka Eisuke Tamura Kosuke Makiguchi Kensuke Kamoshida Ryosuke Sakai Toshifumi Satoh Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2012,50(10):1941-1952
For the living ring‐opening polymerization (ROP) of epoxy monomers, the catalytic activity of organic superbases, tert‐butylimino‐tris(dimethylamino)phosphorane, 1‐tert‐butyl‐2,2,4,4,4‐pentakis(dimethylamino)‐2Λ5,4Λ5‐catenadi(phosphazene), 2,8,9‐triisobutyl‐2,5,8,9‐tetraaza‐1‐phosphabicyclo[3.3.3]undecane, and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris(dimethylamino)phosphoranylidenamino]‐2Λ5,4Λ5‐catenadi(phosphazene) (t‐Bu‐P4), was confirmed. Among these superbases, only t‐Bu‐P4 showed catalytic activity for the ROP of 1,2‐butylene oxide (BO) to afford poly(1,2‐butylene oxide) (PBO) with predicted molecular weight and narrow molecular weight distribution. The results of the kinetic, post‐polymerization experiments, and MALDI‐TOF MS measurement revealed that the t‐Bu‐P4‐catalyzed ROP of BO proceeded in a living manner in which the alcohol acted as the initiator. This alcohol/t‐Bu‐P4 system was applicable to the glycidol derivatives, such as benzyl glycidyl ether (BnGE) and t‐butyl glycidyl ether, to afford well‐defined protected polyglycidols. The α‐functionalized polyethers could be obtained using different functionalized initiators, such as 4‐vinylbenzyl alcohol, 5‐hexen‐1‐ol, and 6‐azide‐1‐hexanol. In addition, the well‐defined cyclic‐PBO and PBnGE were successfully synthesized using the combination of t‐Bu‐P4‐catalyzed ROP and click cyclization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
95.
96.
We study symmetric hyperbolic systems with memory-type dissipation and investigate their dissipative structures. We treat two cases: memory-type diffusion and memory-type relaxation, and observe that the dissipative structures of these two cases are essentially different. Namely, we show that the dissipative structure of the system with memory-type diffusion is of the standard type, while that of the system with memory-type relaxation is of the regularity-loss type. 相似文献
97.
Shelah considered a certain version of Strong Chang's Conjecture which we denote , and proved that it is equivalent to several statements, including the assertion that Namba forcing is semiproper. We introduce an apparently weaker version, denoted , and prove an analogous characterization of it. In particular, is equivalent to the assertion that the the Friedman‐Krueger poset is semiproper. This strengthens and sharpens results by Cox and sheds some light on problems posed by Usuba, Torres‐Perez and Wu. 相似文献
98.
Dr. Yohei Ogiwara Yurika Iino Prof. Dr. Norio Sakai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(26):6513-6516
A method for the palladium/copper-catalyzed direct acylation of azoles with acyl fluorides is described. This study reports the first examples of acyl fluorides being used as acylation reagents in transition-metal-catalyzed aromatic C−H bond functionalization reactions. Depending on the reaction temperature, decarbonylative coupling may also occur. Mechanistic studies suggest that the cleavage of the aromatic C−H bond, promoted by a copper-phosphine species, is not the rate-limiting step of this acylation. 相似文献
99.
100.