全文获取类型
收费全文 | 118篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 81篇 |
晶体学 | 4篇 |
力学 | 1篇 |
数学 | 12篇 |
物理学 | 26篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 5篇 |
2014年 | 1篇 |
2013年 | 6篇 |
2012年 | 2篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2008年 | 3篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 1篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 4篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有124条查询结果,搜索用时 312 毫秒
41.
42.
Hitoshi Mizuguchi Hiroshi Atsumi Yasuhiro Shimada Masatoshi Endo Junichi Shida 《Analytica chimica acta》2004,527(2):131-138
A new technique of expressing slight differences in metal ion concentrations by clear difference in colour was established for visual threshold detection of trace metal ions. The proposed method is based on rapid change of the mole fraction of the homo-binuclear complex (M2L) about a ligand in a narrow range of the total metal ion concentration (MT) in a small excess, in case the second metal ion is bound to the reagent molecule which can bind two metal ions. Theoretical simulations showed that the highly sensitive colour change within slight differences in metal ion concentrations would be realized under the following conditions: (i) both of the stepwise formation constants of complex species are sufficiently large; (ii) the stepwise formation constant of the 1:1 complex (ML) is larger than that of M2L; and (iii) the absorption spectrum of M2L is far apart from the other species in the visible region. Furthermore, the boundary of the colour region in MT would be readily controlled by the total ligand concentration (LT). Based on this theory, the proposed model was verified with the 3,3′-bis[bis(carboxymethyl)amino]methyl derivatives of sulphonephthalein dyes such as xylenol orange (XO), methylthymol blue (MTB), and methylxylenol blue (MXB), which can bind two metal ions at both ends of a π-electron conjugated system. The above-mentioned model was proved with the iron(III)-XO system at pH 2. In addition, MTB and MXB were suitable reagents for the visual threshold detection of trivalent metal ions such as iron(III), aluminium(III), gallium(III) and indium(III) ion in slightly acidic media. The proposed method has been applied successfully as a screening test for aluminium(III) ion in river water sampled at the downstream area of an old mine. 相似文献
43.
Quasi-band structures in 74Se, 78, 80Kr and 84Sr have been investigated using (p, 2nγ) reactions. The members of the quasi-γ band have been observed up to 5+ in 74Se, 78, 80Kr and up to 3+ in84Sr. The analyses of the energy systematics of the quasi-γ bands studied in this mass region as well as in other regions make clear the evolution of the quasi-γ band to the γ-band in well-deformed nuclei. In addition to these positive-parity bands, negative-parity levels were observed in 74Se, 80Kr and 84Sr. 相似文献
44.
Kenji Kinoshita Yasuo Shida Chiseko Sakuma Mutsuo Ishizaki Koichi Kiso Osamu Shikino Hiroyasu Ito Masatoshi Morita Takafumi Ochi Toshikazu Kaise 《应用有机金属化学》2005,19(2):287-293
Diphenylarsinic acid (DPAA) and phenylarsonic acid (PAA), which were degradation products of organoarsenic chemical warfare agents used as sternutatory gas, were detected in the well water at Kamisu, Ibaraki Prefecture, Japan. The standard material of DPAA was synthesized with aqueous arsenic acid and phenylhydrazine in order to determine organic arsenic compounds in well water. The DPAA showed a protonated ion at m/z 263 [M + H]+ and a loss of H2O ion at m/z 245 [M + H ? H2O]+ from protonated ion by the electrospray ionization time‐of‐flight mass spectrometry. The quantitative analysis of DPAA and PAA was performed by high‐performance liquid chromatography inductively coupled plasma mass spectrometry and the system worked well for limpid liquid samples such as well water. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
45.
Self-association of telomeric short oligodeoxyribonucleotides containing a dG cluster. 总被引:1,自引:0,他引:1
Oligonucleotides containing a dG cluster, d(TmGnTm), are models of single-stranded parts of telomeric deoxyribonucleic acid and substitutes for poly(dG). Electrophoretic and spectroscopic analyses of the oligomers indicate that the oligomers can form two alternative structures, single- and quadruple-stranded helices, in solution at room temperature. The transformation of the single-strandef form into the quadruple-stranded form or vice versa is undetectable in 0.1 M NaCl at 4.3 x 10(-5) M strand concentration at room temperature. However, at a 50-fold higher strand concentration, the single-stranded oligomer is gradually converted into the quadruplex. An increase in ionic strength stabilizes the single-stranded structure, so it seems to inhibit the formation of the quadruplex. The quadruplex, [d(TTGGGGTT)]4, is resistant to denaturation in 7 M urea, in which the Watson-Crick type d(TTGGGGTT).d(AACCCCAA) duplex dissociates. An increase in the number of T residues facilitates the dissociation of the quadruplex by heating. Thus the number of T residues surrounding the dG cluster might control the rigidity of the quadruplex structure. 相似文献
46.
E. Nolte Y. Shida W. Kutschera R. Prestele H. Morinaga 《Zeitschrift für Physik A Hadrons and Nuclei》1974,268(3):267-288
In-beamγ ray spectroscopy withγ singles spectra,γγ coincidences andγ ray angular distributions has been performed with several target-projectile combinations:natCa +32S,natCa +40Ca,54Fe +14N,58Ni +12C,58Ni +14N,66Zn +16O,68Zn +16O. Level schemes of66Ge,68Ge,69As,70Se,74Kr,80Sr and82Sr have been deduced. The following level energies and spin-parity assignments have been found:66Ge: 957.4 keV, 2+; 1693.7; 2174.7, (4+); 3685.7; 4207.5;68Ge: 1015.8, 2+; 1777.9, 2+; 2267.9, 4+; 2428.8, 3(+); 2649.1, 3?; 3582.3, (5?); 3649.3, (5?); 3696.2, (6+); 3883.3, (6?); 4054.4, (7?); 4454.6; 4837.3;69As: 98.2; 164.6;789.6;863.2; 1306;2160;2210.4;2831.5;3258.3;3263.5;3991.1;5195.7;70Se: 945.4, 2+; 1600.9; 2039.4, (4+);74Kr: 455.7, 2+; 1013.5, (4+); 1781.5;80Sr: 385.4, 2+; 980.2, (4+); 1763.2, (6+);82Sr: 573.4, 2+; 1328.5,(4+); 2229.6,(6+). γ ray activity spectra have been measured after the bombardment of natural Ca with32S. The half-life of the new isotope69Se has been found to be 27±3 sec. Recoil distance Doppler-shift measurements have been performed with the reactions62,64Ni,66zn(16O, 2n)76, 78 Kr,80Sr. The following half-lives have been determined:76Kr: 423.8 keV, 2+, 37±5 psec; 1034.2,4+, 5.7±1.6;78Kr: 455.3, 2+, 25±3; 1120.0, 4+, 3.8±1;80Sr: 385.4, 2+, 44±6. The energy and half-life systematics of the first excited state of even-even nuclei suggest a maximum of nuclear deformation in the region 28≦N, Z≦50 near 38 76 Sr38 or 40 78 Zr38. 相似文献
47.
48.
(±)-(4,5-anti)-4-Benzyloxy-5-hydroxy-(2E)-hexenoic acid 6 was subjected to δ-lactonization in the presence of 2,4,6-trichlorobenzoyl chloride and pyridine to give the α,β-unsaturated-δ-lactone congener (±)-7 (87% yield) accompanied by trans-cis isomerization. This δ-lactonization procedure was applied to the chiral synthesis of (+)-(4S,5R)-7 or (−)-(4R,5S)-7 from the chiral starting material (+)-(4S,5R)-6 or (−)-(4R,5S)-6. Deprotection of the benzyl group in (+)-(4S,5R)-7 or (−)-(4R,5S)-7 by the AlCl3/m-xylene system gave the natural osmundalactone (+)-(4S,5R)-5 or (−)-(4R,5S)-5 in good yield, respectively. Condensation of (−)-(4R,5S)-5 and tetraacetyl-β-d-glucosyltrichloroimidate 22 in the presence of BF3·Et2O afforded the condensation product (−)-8 (97% yield), which was identical to tetra-O-acetylosmundalin (−)-8 derived from natural osmundalin 9. 相似文献
49.
Tamiya M Ohmori K Kitamura M Kato H Arai T Oorui M Suzuki K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(35):9791-9823
A general approach to the regio- and stereoselective total synthesis of the benanomicin-pradimicin antibiotics (BpAs) is described. Construction of the aglycon has been achieved by 1) the diastereoselective ring-opening of a biaryl lactone by using (R)-valinol as a chiral nucleophile and 2) the stereocontrolled semi-pinacol cyclization of the aldehyde acetal by using SmI(2) in the presence of BF(3)OEt(2) and a proton source to afford the ABCD tetracyclic monoprotected diol. This strategy enabled us to control the two stereogenic sites in the B ring (C-5 and C-6) and the regioselective introduction of the carbohydrate moiety. The ABCD tetracycle could serve as an ideal platform for the divergent access to various BpAs. The amino acid (D-alanine) was introduced onto the ABCD tetracycle. Glycosylation was promoted by the combination of Cp(2)HfCl(2) and AgOTf (1:2 ratio). Construction of the E ring followed by deprotection completed the first total synthesis of benanomicin A (2 a), benanomicin B (2 b), and pradimicin A (1 a). The route is flexible enough to allow the synthesis of other congeners differing in their amino acid and carbohydrate moieties. 相似文献
50.
This paper reports the first computational estimation of the comb polymers' third virial coefficients. The number of the chains in the comb polymers range from 5 to 11. An algorithm that counts the contributing terms of the third virial coefficients in an accelerated manner is presented along with its efficiency dependence on the polymers' size. In addition, the second virial coefficients are estimated for the comb polymers and compared to previously reported results. 相似文献