全文获取类型
收费全文 | 563篇 |
免费 | 18篇 |
国内免费 | 7篇 |
专业分类
化学 | 410篇 |
晶体学 | 8篇 |
力学 | 4篇 |
数学 | 21篇 |
物理学 | 145篇 |
出版年
2023年 | 5篇 |
2022年 | 8篇 |
2019年 | 9篇 |
2018年 | 5篇 |
2016年 | 10篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 24篇 |
2012年 | 14篇 |
2011年 | 24篇 |
2010年 | 24篇 |
2009年 | 19篇 |
2008年 | 27篇 |
2007年 | 32篇 |
2006年 | 35篇 |
2005年 | 23篇 |
2004年 | 34篇 |
2003年 | 25篇 |
2002年 | 21篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 13篇 |
1998年 | 13篇 |
1997年 | 5篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 12篇 |
1973年 | 3篇 |
1970年 | 4篇 |
1969年 | 8篇 |
1968年 | 6篇 |
1967年 | 11篇 |
1966年 | 3篇 |
排序方式: 共有588条查询结果,搜索用时 0 毫秒
51.
Morita Y Nishida S Kobayashi T Fukui K Sato K Shiomi D Takui T Nakasuji K 《Organic letters》2004,6(9):1397-1400
[structure: see text] A bowl-shaped neutral radical with a corannulene system has been designed and synthesized for the first time as a stable solid in air. An unequivocal characterization of the electronic properties of the radical shows that an appreciable amount of spin delocalization extends onto the corannulene unit's curved surface. 相似文献
52.
53.
Fukui K Naito Y Akiyama Y Takahashi K 《European journal of mass spectrometry (Chichester, England)》2004,10(5):639-647
In this study, the fragmentation of gas-phase protonated Angiotensin II is investigated using electrospray ionization (ESI), Fourier-transform ion cyclotron resonance (FT-ICR), and mass spectrometry (MS) with a laser cleavage infrared multiphoton dissociation (IRMPD) technique. The experimental results show that the spectra peaks for the photoproducts are y2/b6- and y7-type ions, corresponding to the cleavage of His-Pro and Asp-Arg in the parent amino acid sequence. The fragmentation of the peptide under collision-free vacuum conditions is modeled using molecular dynamics simulations (MD). The binding energy for the peptide bonds (C'-N bond) of Angiotensin II is estimated from ab initio calculations. The calculations are directed at predicting experimental measurements of the product ions from the photodissociation of the peptide. The product distributions simulated by the MD dissociation trajectories include predominantly y7/b1 and y2/b6 pair ions. 相似文献
54.
Akai S Kawashita N Satoh H Wada Y Kakiguchi K Kuriwaki I Kita Y 《Organic letters》2004,6(21):3793-3796
[reaction: see text] The reactions of (phenylsulfinyl)furans or -thiophenes with carbon nucleophiles in the presence of trifluoroacetic anhydride allowed the nucleophilic installation of carbon functional groups on the furan and thiophene nuclei with complete regioselectivity. 相似文献
55.
Enantioselective Total Synthesis of Dysidavarone A,a Novel Sesquiterpenoid Quinone from the Marine Sponge Dysidea avara 下载免费PDF全文
Yurie Fukui Koichi Narita Prof. Dr. Tadashi Katoh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(9):2436-2439
Dysidavarone A, a structurally unprecedented sesquiterpenoid quinone, was synthesized in 30 % overall yield in a longest liner sequence of 13 steps from commercially available o‐vanillin. A highly strained and bridged eight‐membered carbocyclic core was established by the C7?C21 carbon bond formation through a copper enolate mediated Michael addition to the internal quinone ring. 相似文献
56.
57.
Miura Y Takiguchi Y Shirao M Takata S Yanagida T Fukui H Naganuma M Hatao M 《Photochemistry and photobiology》2008,84(6):1569-1575
In the in vitro evaluation of Sun Protection Factor (SPF), the photostability of the ultraviolet (UV) filters can have a major impact, especially for high-SPF formulations, but is generally not taken into consideration. In this study, we present a UV transmission spectrum measurement system utilizing a high-sensitivity UV photomultiplier tube with concomitant evaluation of photostability. We have developed an algorithm to estimate SPF in vitro by converting the amount of UV light transmission through the sunscreen layer into cumulative relative erythema effectiveness to obtain one minimal erythema dose. Thus, the algorithm uses the same endpoint as in vivo SPF methods, but with a photomultiplier tube as the detector instead of skin. The values obtained showed an excellent correlation with in vivo SPF values, even for high-SPF sunscreens exceeding SPF 50. This method should be suitable as an in vitro SPF testing method for regulatory purposes. 相似文献
58.
Directional crystallization from a binary mixture was performed by pseudo-NpT ensemble molecular dynamics. The initial crystal phase having a face-centered-cubic (fcc) structure grew toward the whole cell according to the temperature gradient in the universal cell. The growing crystal phase was not planar even though the solute molecules grew in two-dimensional coordinates because the solvent molecules disturbed the crystallization of the solute molecules at the diffusive crystal-solution interface. This represented the essential phenomenon of solute distribution during crystallization. Consequently, the growing crystal phase still contained solvent molecules having a liquid structure. The time change of the solute composition in the early phase of crystal growth showed an increase in solute composition as the time step proceeded. The resulting solute composition in this early phase was considered at different temperature gradients in the universal cell and it increased as the temperature of the initial crystal-solution interface increased. A new distribution coefficient model was proposed as a function of the difference between the local solute composition and bulk solute composition in the solution around the crystal-solution interface. The impurity-solvent distribution coefficient could be represented by the new model for faster growth of the lower temperature's initial interface. As regards a better distribution coefficient, there was found to be a very dilute solution phase over the crystal phase. The new variable "distribution rate" instead of the ambiguous variable "growth rate" was considered as a function of temperature gradient in the universal cell. 相似文献
59.
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
60.
Koji Konomi He-Sheng Li† Norihito Kuno Masaki Furuya‡ 《Photochemistry and photobiology》1993,58(6):852-857
Abstract Treatment of imbibed embryonic axes taken from seeds of Pisum sativum with N-phenylimide S-23142, a herbicide that has been suggested to inhibit protoporphyrin synthesis, or with N -methyl mesoporphyrin IX, an inhibitor of the iron chelatase for heme, resulted in a significant decrease in the amount of spectrophotometrically detectable phytochromc in the axes in both cases. However, the amount of immunochemically detectable phytochrome was not affected by either treatment. If S-23142 inhibits the synthesis of protoporphyrin IX in pea, it appears that the conversion of protoporphyrinogen IX to protoporphyrin IX is involved in the biosynthesis of the phytochrome chromophore. The conversion of protoporphyrin IX to heme (Fe-protoporpbyrin) also appears to be a step in the biosynthesis of the chromophore, since N -methyl mesoporphyrin IX prevented the synthesis of spectrophotometrically detectable phytochrome but did not affect the magnesium chelatase activity required for the synthesis of chlorophyll in pea embryonic axes. The results suggest that protoporphyrinogen IX, protoporphyrin IX and heme are intermediates in the biogenesis of the phytochromc chromophore. The pathway to phytochromobilin might become fixed after protoporphyrin IX, being directed toward the Fe branch for heme rather than to the Mg branch for chlorophyll. 相似文献