全文获取类型
收费全文 | 205篇 |
免费 | 3篇 |
专业分类
化学 | 108篇 |
力学 | 3篇 |
数学 | 21篇 |
物理学 | 76篇 |
出版年
2023年 | 2篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 11篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 7篇 |
2002年 | 11篇 |
2001年 | 14篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 8篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1992年 | 5篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 4篇 |
1977年 | 5篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1971年 | 2篇 |
1970年 | 3篇 |
1968年 | 2篇 |
1965年 | 1篇 |
1962年 | 1篇 |
1939年 | 1篇 |
1928年 | 1篇 |
1927年 | 1篇 |
1881年 | 1篇 |
1879年 | 3篇 |
1876年 | 1篇 |
1873年 | 2篇 |
1872年 | 2篇 |
1867年 | 1篇 |
排序方式: 共有208条查询结果,搜索用时 0 毫秒
11.
E. Arijs A. Barassin E. Kopp C. Amelynck V. Catoire H. P. Fink C. Guimbaud U. Jenzer D. Labonnette W. Luithardt E. Neefs D. Nevejans N. Schoon A. -M. Van Bavel 《International journal of mass spectrometry》1998,181(1-3)
Detailed height profiles of stratospheric nitric acid mixing ratios have been derived with a baloon borne chemical ionization mass spectrometer by applying several ion molecule reaction schemes, each associated to a specific and selective ion source. These ions (CO3−, Cln−, CF3O−, and CF3O−H2O) give rise to specific product ions (mainly CO3−HNO3, NO3−HCl, NO3−HF, and CF3O−HNO3) upon reaction with ambient nitric acid molecules. This paper reports on the instrumental details as well as on the results obtained during two balloon flights with the instrument. Within the accuracy of the measurements, the nitric acid height profiles obtained with the three different ion sources are in good agreement with one another as well as with literature data. 相似文献
12.
Brigitte Kopp Erika Kubelka Christian Reich Wolfgang Robien Wolfgang Kubelka 《Helvetica chimica acta》1991,74(3):611-616
Investigation of the tubers of Eranthis hyemalis (Ranunculaceae) afforded six chromenone glycosides. Their structures have been elucidated mainly by spectroscopic (FAB-MS, 2D-NMR techniques) and chemical methods (acidic and enzymatic hydrolysis) as 9-{[(β-D -glucopyranosyl)oxy]methyl}-8,11-dihydro-5-hydroxy-2-methyl-4H-pyrano[2,3-g][1]benzoxepin-4-one ( 1 ), 9-{[(β-D -gentiobiosyl)oxy]methyl}-8,11-dihydro-5-hydroxy-2-methyl-4H-pyrano[2,3-g][1]benzoxepin-4-one( 2 ), 9-{[(β-D -glucopyranosvl)oxy]melhyl}-8,11-dihydro-5-hydroxy-2-(hydroxy-methyl)-4H-pyrano[2,3-g][1]benzoxepin-4-one( 3 ), 8-{(2E)-4-[(β-D -glucopyranosyl)oxy]-3-methylbut-2-enyl}-5,7-dihydroxy-2-methyl-4H-1-benzopyran-4-one ( 4 ), 8-{(2E)-4-[(β-D -glucopyranosyi)oxy]-3-methylbut-2-enyl}-5,7-dihydroxy-2-(hydroxymethyl)-4H-1-benzopyran-4-one ( 5 ), and 7-{[(β-D -glucopyranosy1)oxy]methyl}-2,3-dihydro-2-(l-hydroxy-1-methylethyl)-4-methoxy-5H-furo[3,2-g][1]benzopyran-5-one ( 6 ). Compound 2 exhibited negative inotropic activity. 相似文献
13.
Willian Kopp Hernane S. Barud Marcelo F. Paz Luciano A. Bueno Raquel L. C. Giordano Sidney J. L. Ribeiro 《Journal of Sol-Gel Science and Technology》2012,63(2):219-223
The addition of calcium chloride eletrolyte to sodium polyphosphate solutions lead to Calcium polyphosphate coacervates. The effects of a thermal treatment were investigated with the objective to increase the relative stability of the obtained material. Thermogravimetry analysis indicates that coacervates became less hydrophilic and more thermally stable after the thermal treatment. Crystallization was identified through differential scanning calorimetry and X-ray diffraction. Morphological changes were observed after the thermal treatment by scanning electron microscopy. N2 adsorption?Cdesorption isotherms suggest that both materials, thermally treated or not, display type IV isotherms, low superficial area and mesoporous structure. Stability experiments in solutions at different pH values show that the thermally treated calcium polyphosphate is relatively more stable than the non-treated coacervate. 相似文献
14.
15.
The structural rules which govern the epitaxial crystallisation of polymers - and especially polyolefins - on organic substrates are established. Illustrative examples involve isotactic and syndiotactic polypropylenes and poly( l-butene). Investigation of the film structure by electron microscopy, electron diffraction and atomic force microscopy reveals some unprecedented features, including in particular the selection of the contact plane according to the chirality of its constituent helices, and direct observation of both right and left hands of polyolefin helices. 相似文献
16.
M. I. Kopp A. V. Tur V. V. Yanovsky 《Journal of Experimental and Theoretical Physics》2017,124(6):1010-1022
We have found a new type of large-scale instability in a rotating stratified moist atmosphere with small-scale turbulence. The turbulence is excited by an external small-scale force with a low Reynolds number. We have constructed the theory based on the method of multiscale asymptotic expansions. The nonlinear equations for large-scale motion have been derived in the third order of the perturbation theory. We have investigated the linear instability and stationary nonlinear regimes. Solutions in the form of localized vortex structures or kinks of a new type have been obtained. 相似文献
17.
D. H. Chaplin W. D. Hutchison M. P. Kopp N. Yazidjoglou 《Hyperfine Interactions》1988,43(1-4):241-247
Electric quadrupole interactions of impurity nuclei in single crystals of54MnNi,125SbNi and125SbFe have been studied as a function of crystal field direction and applied magnetic field using MAPON. Distributions are in all
cases broad compared with the mode values of the EQI's. For54MnNi the mode efg is isotropic to better than 5% between the easy <111> axis and a hard <100> axis. The efg is +0.88 (15)x 1019 Vm−2. The mode efg for125SbFe along its easy <100> axis is one half of that along a hard <112> axis, and one third of that measured along the easy <111>
axis of125SbNi. The much larger efg mode and distribution seen in125SbNi, for four to eight times greater dilution than for125SbFe, suggests intrinsic contributions due to valence screening effects in the more itinerant nickel host. 相似文献
18.
19.
20.
Five-coordinate phenylsilicates are formed from the reaction of trimethoxy(phenyl)silane with monosaccharides in methanol in the presence of a stoichiometric amount of base. Five complexes have been isolated and characterized with two ketoses and three aldopentoses. The silicon central atom in [K([18]crown-6)][PhSi(beta-D-Fruf 2,3H-2)2].MeOH (1, Fru=fructose) is part of two chelate rings, with the ligands being beta-D-fructofuranose-O2,O3 dianions. The beta-furanose isomer is best suited for silicon ligation because it exhibits a torsion angle close to 0 degrees for the most acidic diol function, thus assuring a flat chelate ring. The same structural principles are also found in [K([18]crown-6)][PhSi(beta-D-Araf1,2H-2)2].2 MeOH (2, Ara=arabinose), [K([18]crown-6)][PhSi(alpha-D-Ribf1,2H-2)2] (3, Rib=ribose), [K([18]crown-6)][PhSi(alpha-D-Xylf1,2H-2)2]. acetone (4, Xyl=xylose), and [K([18]crown-6)][PhSi(alpha-D-Rulf2,3H-2)2] (5, Rul=ribulose). 相似文献