全文获取类型
收费全文 | 1422篇 |
免费 | 45篇 |
国内免费 | 2篇 |
专业分类
化学 | 1135篇 |
晶体学 | 8篇 |
力学 | 19篇 |
数学 | 50篇 |
物理学 | 257篇 |
出版年
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 14篇 |
2019年 | 17篇 |
2018年 | 8篇 |
2017年 | 7篇 |
2016年 | 34篇 |
2015年 | 35篇 |
2014年 | 34篇 |
2013年 | 59篇 |
2012年 | 70篇 |
2011年 | 90篇 |
2010年 | 52篇 |
2009年 | 47篇 |
2008年 | 96篇 |
2007年 | 74篇 |
2006年 | 83篇 |
2005年 | 69篇 |
2004年 | 68篇 |
2003年 | 78篇 |
2002年 | 73篇 |
2001年 | 30篇 |
2000年 | 22篇 |
1999年 | 18篇 |
1998年 | 11篇 |
1997年 | 20篇 |
1996年 | 16篇 |
1995年 | 14篇 |
1994年 | 18篇 |
1993年 | 13篇 |
1992年 | 17篇 |
1991年 | 9篇 |
1990年 | 15篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 12篇 |
1985年 | 19篇 |
1984年 | 15篇 |
1983年 | 18篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1976年 | 15篇 |
1975年 | 8篇 |
1974年 | 8篇 |
1973年 | 12篇 |
1968年 | 5篇 |
排序方式: 共有1469条查询结果,搜索用时 15 毫秒
171.
Ulmann PA Tanaka H Matsuo Y Xiao Z Soga I Nakamura E 《Physical chemistry chemical physics : PCCP》2011,13(47):21045-21049
A [70]fullerene-benzodifuranone acceptor dyad synthesized by a Ag?-mediated coupling reaction was used to construct a thin-film organic solar cell. The fullerene and the benzodifuranone dye in the dyad have close-lying LUMO levels in the range of 3.7-3.9 eV, so that energy transfer from the dye to the fullerene can take place. A p-n heterojunction photovoltaic device consisting of a tetrabenzoporphyrin and a [70]fullerene-benzodifuranone dyad showed a weak but discernible contribution from light absorption of the dyad to the photocurrent under both a positive and a negative effective bias. These results indicate that the benzodifuranone moiety attached to the acceptor contributes to light-harvesting by energy transfer. 相似文献
172.
Akiko Hori Yuta Inoue Hidetaka Yuge 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(5):o154-o156
4‐Chloro‐5‐(2‐phenoxyethoxy)phthalonitrile, C16H11ClN2O2, (I), and 4‐chloro‐5‐[2‐(pentafluorophenoxy)ethoxy]phthalonitrile, C16H6ClF5N2O2, (II), show different types of electrostatic interaction. In (I), the phenoxy and phthalonitrile (benzene‐1,2‐dicarbonitrile) moieties are well separated in an open conformation and intermolecular C—H...π interactions are observed in the crystal packing. On the other hand, in (II), the pentafluorophenoxy moiety interacts closely with the Cl atom to form a folded conformation containing an intramolecular halogen–π interaction. 相似文献
173.
R. A. Broglia T. Døssing M. Matsuo E. Vigezzi P. Bosetti A. Bracco S. Frattini B. Herskind S. Leoni P. Rasmussen 《Zeitschrift für Physik A Hadrons and Nuclei》1987,356(3):259-262
Rotational motion loses its coherence as a function of the nuclear internal excitation energy. The damping process does not proceed in a continuous fashion and scars of discrete rotational bands are found, inbedded in a background of damped rotational states, regardless whether the calculations are carried out using effective or “random” forces. The complexity of the damping mechanism is revealed in the lineshape of the ridges in the γ-γ correlation spectrum. 相似文献
174.
Katsumi Saitoh Koichiro Sera Tadashi Shirai Tatsuji Sato Matsuo Odaka 《Analytical sciences》2003,19(4):525-528
The purpose of this study is to clarify the chemical characterization of PM2.5 and PM10 in diesel exhaust particles (DEP). Sampling of PM2.5 and PM10 in DEP was carried out in November 1999 using an automobile exhaust testing system at the National Traffic Safety and Environment Laboratory, with a diesel truck (engine type: direct injection, displacement: 7,961 cc, carrying weight: 2,020 kg, equivalent inertia weight: 5,600 kg) placed on a chassis dynamometer. Sampling conditions included idling, constant speed of 40 km/h, M-15 test pattern and 60%-revolution/40%-load of maximum power. Samples were collected on a polycarbonate membrane filter (Nuclepore, pore size: 0.8 microm) using a MiniVol Portable Air Sampler (Airmetrics Co., Inc.). The concentrations of several elemental and ionic species in the PM2.5 and PM10 samples were determined by particle induced X-ray emission (PIXE) and ion chromatography analysis. PIXE analysis of the PM2.5 and PM10 samples revealed 15 elements, of which Na, Mg, Si, S, Cl, Ca, Fe and Zn were found to be the major components. Ionic species were Cl-, NO2-, NO3-, SO4(2-), Na+, NH4+, K+ and Ca2+. Concentrations of elements and ionic species under the sampling condition of 60%-revolution/40%-load were highest in comparison with those of the other sampling conditions. The elemental and ionic species data were compared for PM2.5 and PM10; PM2.5 concentrations were 70% or more of PM10 concentrations for the majority of elements, and concentrations of ionic species in PM2.5 and PM10 were almost identical. 相似文献
175.
Hisao Yamashige Shuji Matsuo Tsutomu Kurisaki Rupert C C Perera Hisanobu Wakita 《Analytical sciences》2005,21(3):309-314
X-ray absorption near edge structure (XANES) measurements at the C, N, and Fe K absorption edges were performed for iron(III)-tetraphenylporphyrin (FeTPP), iron(III)-tetrakis(p-carboxyphenyl)porphyrin (FeTCPP), and iron(III)-tetrakis(p-sulfonatophenyl)porphyrin (FeTSPP). The spectral shapes differ in the Fe K XANES, but not in C and N K XANES among FeTPP, FeTCPP, and FeTSPP. Crosschecks of XANES data for C, N, and Fe K absorption edges in combination with discrete variational (DV)-Xalpha molecular orbital (MO) calculations indicate that each p-electron-withdrawing group on four meso-phenyl substitutes in an Fe(III)-porphyrin complex brings about a unique electron state through the complex because of the electron-withdrawal strength, itself. Consequently, they affect the positive charge of the center Fe(III) ion. 相似文献
176.
Hisao Yamashige Shuji Matsuo Tsutomu Kurisaki Rupert C C Perera Hisanobu Wakita 《Analytical sciences》2005,21(6):635-639
This study investigated the protonation of nitrogen atoms in porphyrins with meso-phenyl p-substituted by an electron-withdrawing group using N 1s X-ray photoelectron spectroscopy (XPS), the N K X-ray absorption near-edge structure (XANES), and the discrete variational (DV)-Xalpha molecular orbital (MO) method. Both tetraphenylporphyrin (TPP) and tetrakis(p-sulfonatophenyl)porphyrin (TSPP) have a single structure: the former has two protonated and two non-protonated N atoms in the porphine ring; the latter has four protonated N atoms in the porphine ring. In contrast, a combination of XPS, XANES, and DV-Xalpha MO calculations shows that tetrakis(p-carboxyphenyl)porphyrin (TCPP) has a dual structure: one structure has two protonated and two non-protonated N atoms; the other has four protonated N atoms. Furthermore, this result was also considered based on the protonation constants of N atoms in the porphyrins. The correlation between the strength of electron-withdrawing groups and protonation to N atoms in porphyrins can be described using the spectral patterns of the N 1s XPS and N K XANES spectra. 相似文献
177.
Kuno A. Zheng G. D. Matsuo M. Takano B. Shi J. A. Wang Q. 《Hyperfine Interactions》2002,141(1-4):321-326
In this study, 57Fe Mössbauer spectroscopy has been applied to sediments collected from Qinghai Lake in Qinghai Province, China, to investigate the vertical distribution of iron species. Their Mössbauer spectra consisted of four doublets ascribable to one paramagnetic high-spin Fe3+, two paramagnetic high-spin Fe2+ with different quadrupole splittings, and one diamagnetic low-spin Fe2+ that corresponds to pyrite (FeS2). The distribution of pyrite suggested climatic changes during the past nine thousand years. It was demonstrated that the iron speciation in the salt lake sediments by Mössbauer spectroscopy can be used to reconstruct the past environment.
相似文献178.
Shigeki Habaue Ryo Muraoka Akiko Aikawa Soichiro Murakami Hideyuki Higashimura 《Journal of polymer science. Part A, Polymer chemistry》2005,43(8):1635-1640
The oxidative coupling polymerization of 2,3‐dihydroxynaphthalene with the novel dinuclear‐type copper(II) catalysts successfully produced poly(2,3‐dihydroxy‐1,4‐naphthylene). For example, the MeOH‐insoluble polymer with a number average molecular weight of 4.4 × 103 from the polymerization using the complex of CuCl2 and N,N′‐bis(2‐morpholinoethyl)‐p‐xylylenediamine ( p ‐ 1 ) at room temperature under an O2 atmosphere followed by acetylation of the hydroxyl groups was obtained in 63% yield. The structures of the tetraamine ligands and the counter anion of the copper(II) salts significantly influenced the catalyst activity. The polymerization of 2,2′‐dimethoxy‐1,1′‐binaphthalene‐3,3′‐diol with the 2CuCl2‐ p ‐ 1 catalyst, however, resulted in a lower yield. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1635–1640, 2005 相似文献
179.
The first total synthesis of a cyclic depsipeptide possessing the 3-amino-6-hydroxy-2-piperidone (Ahp) unit was successfully achieved in a convergent manner by the oxidative construction of the Ahp unit at the later stage of the synthesis. This synthetic work provides data indicating that the structure of the target Ahp-depsipeptide, micropeptin T-20, should be re-examined. 相似文献
180.
D. Moromachi A. Kuno M. Matsuo 《Journal of Radioanalytical and Nuclear Chemistry》2008,278(2):495-498
In order to investigate the transition of tidelands, we collected sediments in Yatsu tideland and Nekozane river mouth in Tokyo Bay. The vertical distributions of elements were determined by instrumental neutron activation analysis and prompt gamma-ray analysis. In Yatsu tideland the vertical distribution changed in a great extent, which was considered as an influence of the neighboring reclamation. They were categorized into four groups, and two parameters were created by applying principal component analysis. Chemical states of iron and sulfur were also investigated by Mössbauer spectroscopy and X-ray absorption fine structure. These results show that Yatsu tideland became an anaerobic environment. 相似文献