全文获取类型
收费全文 | 1523篇 |
免费 | 37篇 |
国内免费 | 2篇 |
专业分类
化学 | 829篇 |
晶体学 | 13篇 |
力学 | 65篇 |
数学 | 142篇 |
物理学 | 513篇 |
出版年
2023年 | 8篇 |
2020年 | 12篇 |
2019年 | 16篇 |
2018年 | 8篇 |
2016年 | 27篇 |
2015年 | 35篇 |
2014年 | 27篇 |
2013年 | 61篇 |
2012年 | 80篇 |
2011年 | 82篇 |
2010年 | 55篇 |
2009年 | 54篇 |
2008年 | 68篇 |
2007年 | 72篇 |
2006年 | 84篇 |
2005年 | 78篇 |
2004年 | 62篇 |
2003年 | 56篇 |
2002年 | 43篇 |
2001年 | 23篇 |
2000年 | 36篇 |
1999年 | 16篇 |
1998年 | 13篇 |
1997年 | 20篇 |
1996年 | 22篇 |
1995年 | 27篇 |
1994年 | 23篇 |
1993年 | 34篇 |
1992年 | 29篇 |
1991年 | 12篇 |
1990年 | 23篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1980年 | 8篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 7篇 |
1975年 | 10篇 |
1974年 | 9篇 |
1943年 | 7篇 |
1934年 | 6篇 |
1933年 | 11篇 |
1931年 | 8篇 |
排序方式: 共有1562条查询结果,搜索用时 15 毫秒
51.
Hattori S Ohkubo K Urano Y Sunahara H Nagano T Wada Y Tkachenko NV Lemmetyinen H Fukuzumi S 《The journal of physical chemistry. B》2005,109(32):15368-15375
Boron dipyrromethene (BODIPY), which is commonly used as an energy absorbing and transferring antenna molecule, has been modified to contain an electron donor moiety, 8-(2,4,5-trimethoxyphenyl)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (MEOPHBDP). The photoinduced electron transfer from a 2,4,5-trimethoxyphenyl moiety to a BODIPY moiety of MEOPHBDP in acetonitrile was observed by femtosecond laser flash photolysis measurements. The lifetime of the charge-separated state of MEOPHBDP was 59 ps at 298 K. The dye-sensitized solar cells (DSSC) were prepared using MEOPHBDP with carboxylic acid (MEOPHBDP-COOH) and a reference BODIPY dye having no electron donor moiety. The photovoltaic measurements were performed using a standard two-electrode system consisting of a working electrode and a Pt sputtered electrode in methoxyacetonitrile containing 0.5 M iodide and 0.05 M I(2). The photoelectrochemical properties of DSSC with MEOPHBDP are compared with those with a reference BODIPY dye. 相似文献
52.
53.
54.
55.
56.
57.
The thermal decomposition of peroxy acetyl nitrate (PAN) is investigated by low pressure flash thermolysis of PAN highly diluted in noble gases and subsequent isolation of the products in noble gas matrices at low temperatures and by density functional computations. The IR spectroscopically observed formation of CH3C(O)OO and H2CCO (ketene) besides NO2, CO2, and HOO implies a unimolecular decay pathway for the thermal decomposition of PAN. The major decomposition reaction of PAN is bond fission of the O-N single bond yielding the peroxy radical. The O-O bond fission pathway is a minor route. In the latter case the primary reaction products undergo secondary reactions whose products are spectroscopically identified. No evidence for rearrangement processes as the formation of methyl nitrate is observed. A detailed mapping of the reaction pathways for primary and secondary reactions using quantum chemical calculations is in good agreement with the experiment and predicts homolytic O-N and O-O bond fissions within the PAN molecule as the lowest energetic primary processes. In addition, the first IR spectroscopic characterization of two rotameric forms for the radical CH3C(O)OO is given. 相似文献
58.
Short-lived (CF(3))(3)B and (CF(3))(3)BCF(2) are generated as intermediates by thermal dissociation of (CF(3))(3)BCO and F(-) abstraction from the weak coordinating anion [B(CF(3))(4)](-), respectively. Both Lewis acids cannot be detected because of their instability with respect to rearrangement reactions at the B-C-F moiety. A cascade of 1,2-fluorine shifts to boron followed by perfluoroalkyl group migrations and also difluorocarbene transfer reactions occur. In the gas phase, (CF(3))(3)B rearranges to a mixture of linear perfluoroalkyldifluoroboranes C(n)()F(2)(n)()(+1)BF(2) (n = 2-7), while the respective reactions of (CF(3))(3)BCF(2) result in a mixture of linear (n = 2-4) and branched monoperfluoroalkyldifluoroboranes, e.g., (C(2)F(5))(CF(3))FCBF(2). For comparison, the reactions of [CF(3)BF(3)](-) and [C(2)F(5)BF(3)](-) with AsF(5) are studied, and the products in the case of [CF(3)BF(3)](-) are BF(3) and C(2)F(5)BF(2) whereas in the case of [C(2)F(5)BF(3)](-), C(2)F(5)BF(2) is the sole product. In contrast to reports in the literature, it is found that CF(3)BF(2) is too unstable at room temperature to be detected. The decomposition of (CF(3))(3)BCO in anhydrous HF leads to a mixture of the new conjugate Br?nsted-Lewis acids [H(2)F][(CF(3))(3)BF] and [H(2)F][C(2)F(5)BF(3)]. All reactions are modeled by density functional calculations. The energy barriers of the transition states are low in agreement with the experimental results that (CF(3))(3)B and (CF(3))(3)BCF(2) are short-lived intermediates. Since CF(2) complexes are key intermediates in the rearrangement reactions of (CF(3))(3)B and (CF(3))(3)BCF(2), CF(2) affinities of some perfluoroalkylfluoroboranes are presented. CF(2) affinities are compared to CO and F(-) affinities of selected boranes showing a trend in Lewis acidity, and its influence on the stability of the complexes is discussed. Fluoride ion affinities are calculated for a variety of different fluoroboranes, including perfluorocarboranes, and compared to those of the title compounds. 相似文献
59.
Bernadette HugonBruno Pfeiffer Pierre RenardMichelle Prudhomme 《Tetrahedron letters》2003,44(20):3935-3937
A synthesis in a few steps of a new family of granulatimide analogues was performed. In the new compounds, the aromatic framework of granulatimide is modified by replacement of the imidazole unit by a maleimide moiety. The synthesis of a water-soluble analogue is also presented. 相似文献
60.
Color Bricks: Building Highly Organized and Strongly Absorbing Multicomponent Arrays of Terpyridyl Perylenes on Metal Oxide Surfaces
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Essi Sariola‐Leikas Dr. Zafar Ahmed Dr. Paola Vivo Anniina Ojanperä Dr. Kimmo Lahtonen Jesse Saari Prof. Mika Valden Prof. Helge Lemmetyinen Dr. Alexander Efimov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1501-1510
Terpyridine‐substituted perylenes containing cyclic anhydrides in the peri position were synthesized. The anhydride group served as an anchor for assembly of the terpyridyl‐crowned chromophores as monomolecular layers on metal oxide surfaces. Further coordination with Zn2+ ions allowed for layer‐by‐layer formation of supramolecular assemblies of perylene imides on the solid substrates. With properly selected anchor and linker molecules it was possible to build high quality structures of greater than ten successive layers by a simple and straightforward procedure. The prepared films were stable and had a broad spectral coverage and high absorbance. To demonstrate their potential use, the synthesized dyes were employed in solid‐state dye‐sensitized solar cells, and electron injection from the perylene antennas to titanium dioxide was observed. 相似文献