全文获取类型
收费全文 | 405篇 |
免费 | 27篇 |
专业分类
化学 | 363篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 13篇 |
物理学 | 53篇 |
出版年
2023年 | 3篇 |
2021年 | 6篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 11篇 |
2015年 | 19篇 |
2014年 | 4篇 |
2013年 | 22篇 |
2012年 | 20篇 |
2011年 | 39篇 |
2010年 | 15篇 |
2009年 | 12篇 |
2008年 | 30篇 |
2007年 | 30篇 |
2006年 | 31篇 |
2005年 | 26篇 |
2004年 | 28篇 |
2003年 | 18篇 |
2002年 | 10篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1967年 | 3篇 |
1964年 | 1篇 |
1890年 | 1篇 |
排序方式: 共有432条查询结果,搜索用时 15 毫秒
31.
Hironobu Sasaki 《偏微分方程通讯》2015,40(11):1959-2004
We study scattering problems for the one-dimensional nonlinear Dirac equation (?t + α?x + iβ)Φ = λ|Φ|p?1Φ. We prove that if p > 3 (resp. p > 3 + 1/6), then the wave operator (resp. the scattering operator) is well-defined on some 0-neighborhood of a weighted Sobolev space. In order to prove these results, we use linear operators D(t)xD(?t) and t?x + x?t ? α/2, where {D(t)}t∈? is the free Dirac evolution group. For the reader's convenience, in an appendix we list and prove fundamental properties of D(t)xD(?t) and t?x + x?t ? α/2. 相似文献
32.
33.
Munetaka Iwamura Airi Fukui Koichi Nozaki Hikaru Kuramochi Satoshi Takeuchi Tahei Tahara 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(51):23354-23361
Femtosecond time-resolved absorption and picosecond time-resolved emission measurements were carried out for highly concentrated aqueous solutions of K2[Pt(CN)4] to investigate excited-state dynamics of the [Pt(CN)42−] oligomers formed with metallophilic interactions. Time-resolved absorption spectra exhibit complicated dynamics that are represented with five time constants. Among them, the 90-ps and 400-ps dynamics were assigned to the S1 → T1 intersystem crossing of the trimer and tetramer coexisting in the solution by comparison with the fluorescence decays. Clear oscillations of transient absorption were observed in the first few picoseconds, and the frequency-detected-wavelength 2D analysis revealed that the 135-cm−1 and 65-cm−1 oscillations arise from the Pt–Pt stretch motions of the S1 trimer and S1 tetramer, respectively. The obtained time-resolved spectroscopic data provide a clear view of the excited-state dynamics of the [Pt(CN)42−] oligomers in the femto-/picosecond time region. 相似文献
34.
Ryo Kimura Hikaru Kuramochi Pengpeng Liu Takuya Yamakado Atsuhiro Osuka Tahei Tahara Shohei Saito 《Angewandte Chemie (International ed. in English)》2020,59(38):16430-16435
Flapping fluorophores (FLAP) with a flexible 8π ring are rapidly gaining attention as a versatile photofunctional system. Here we report a highly photostable “flapping peryleneimide” with an unprecedented fluorogenic mechanism based on a bent‐to‐planar conformational change in the S1 excited state. The S1 planarization induces an electronic configurational switch, almost quenching the inherent fluorescence (FL) of the peryleneimide moieties. However, the FL quantum yield is remarkably improved with a prolonged lifetime upon a slight environmental change. This fluorogenic function is realized by sensitive π‐conjugation design, as a more π‐expanded analogue does not show the planarization dynamics. With strong visible‐light absorption, the FL lifetime response synchronized with the flexible flapping motion is useful for the latest optical techniques such as FL lifetime imaging microscopy (FLIM). 相似文献
35.
36.
Toshie Tahara Yoshitsugu Sakuda Mitsuaki Kodama Yoshimasa Fukazawa Shô Itô Kazuyoshi Kawazu Shuhei Nakajima 《Tetrahedron letters》1980,21(19):1861-1862
The structures of xantholides A and B were deduced on the basis of IR and NMR spectra, and confirmed by X-ray analysis. Xantholide A inhibited the larval growth of Drosophila melanogaster. 相似文献
37.
Okada S Okinaka K Iwawaki H Furugori M Hashimoto M Mukaide T Kamatani J Igawa S Tsuboyama A Takiguchi T Ueno K 《Dalton transactions (Cambridge, England : 2003)》2005,(9):1583-1590
This study reports substituent effects of iridium complexes with 1-phenylisoquinoline ligands. The emission spectra and phosphorescence quantum yields of the complexes differ from that of tris(1-phenylisoquinolinato-C2,N)iridium(iii)(Irpiq) depending on the substituents. The maximum emission peak, quantum yield and lifetime of those complexes ranged from 598-635 nm, 0.17-0.32 and 1.07-2.34 micros, respectively. This indicates the nature of the substituents has a significant influence on the kinetics of the excited-state decay. The substituents attached to phenyl ring have an influence on a stability of the HOMO. Furthermore, those substituents have effect on the contribution to a mixing between 3pi-pi* and (3)MLCT for the lowest excited states. Some of the complexes display the larger quantum yield than Irpiq, which has the quantum yield of 0.22. The organic light emitting diode (OLED) device based on tris [1-(4-fluoro-5-methylphenyl)isoquinolinato-C2,N]iridium(iii)(Ir4F5Mpiq) yielded high external quantum efficiency of 15.5% and a power efficiency of 12.4 lm W(-1) at a luminance of 218 cd m(-2). An emission color of the device was close to an NTSC specification with CIE chromaticity characteristics of (0.66, 0.34). 相似文献
38.
Matsuo Y Tahara K Sawamura M Nakamura E 《Journal of the American Chemical Society》2004,126(28):8725-8734
Selective penta-addition of a methylcopper reagent followed by addition of a phenylcopper reagent to a suitably modified synthetic intermediate results in creation of 40pi-electron systems-hoop- and bowl-shaped cyclic benzenoid compounds, [10]cyclophenacene, and dibenzo-fused corannulene derivatives. The 40pi-electron cyclophenacene derivatives have been found to be chemically stable, yellow-colored, luminescent (560 nm), and EPR-silent. X-ray crystallographic analysis provided precision structural data sets. The dibenzo-fused corannulene derivatives exhibit blue-green (460 nm) to red (649 nm) fluorescence. 相似文献
39.
Transformation of a crystallized molecular solid to a periodically organized covalent extended solid was obtained by a solvent-free process of an organosilane. Hydrolysis and further polycondensation occur in the solid state; in addition this route leads to crystal-like silicon-based hybrid materials with a higher periodicity than material prepared by sol-gel process. 相似文献
40.