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M. M. Moustafa 《Journal of Thermal Analysis and Calorimetry》1997,50(3):463-471
The oxime and Schiff's base of N-furoylphenylhydroxylamine form complexes with Co2+, Cu2+, Zn2+ and Fe3+. These complexes were studied by means of the UV — Vis. spectra of nujol mulls, electron spin resonance (ESR) spectra and magnetic susceptibility to determine their stereochemistry. The complexes were characterized via elemental analyses, molar conductivities and thermogravimetric analyses. Organic reagents were used for the gravimetric determination of Co2+, Cu2+ and Fe3+ through the precipitation of their complexes. The compounds were also used for separation of a binary mixture of Cu2+ and Cu2+. Interferences were studied. 相似文献
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CrystalStructureandMolecularAbsoluteConfigurationof(+)-Isocedranol(C_(15)H_(26)O)¥LiuJie;ChenMin-Qin(CenterofAnalysis&Measurem... 相似文献
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The title sterically crowded di-9-anthrylethyne derivative with 3,5-iPr2-phenyl groups at 1-position showed a barrier to rotation about the acetylenic axis of 18.0 kcal mol−1 based on a dynamic NMR study, which is an extremely high value for acyclic diarylethynes. The mechanism of the dynamic stereochemistry and the substituent effect on the rotational barrier are discussed. 相似文献
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The crystal structure of synthetic carlinite, Tl2S, was re-determined by single crystal and powder X-ray diffraction methods. The cell parameters obtained from Rietveld refinement are a=12.150(2) Å, c=18.190(4) Å, V=2325.5(7) Å3. A single crystal data refinement proved Tl2S crystallizing in the trigonal space group R3 with M=440.8gmol−1, Z=27, R=0.076, and wR=0.145. The atomic arrangement found is that of a strongly deformed anti-CdI2 type, but the deformation is clearly different from that given by previous workers. In the five crystallographically different STl6 octahedra the S-Tl distances vary between 2.82 and 3.09Å, the Tl-Tl edges between 3.52 and 4.58Å. The common features of these octahedra are (i) each one with a definitely smaller vs larger Tl3 face in trans-position, both faces parallel or sub-parallel (00.1), and (ii) each three shorter and longer S-Tl distances to the atoms of the larger and smaller Tl3 faces, respectively. The Tl-Tl contacts between different Tl2S sheets are on the average definitely shorter than the ones within the sheet and they can be smaller than the Tl-Tl contacts in the small Tl3 faces of the STl6 octahedra. The atomic arrangement indicates that the single electron pairs of the monovalent Tl atoms are not arranged all parallel to the z-axis, as one would expect for Tl2S with an ideal anti-CdI2 structure. The surrounding of the S atoms resembles that of one-third of the Cl atoms in yellow InCl. The absorbance of Tl2S is very low at wave numbers approximately <9000 cm−1. 相似文献
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Organoboranes, readily available via the hydroboration of unsaturated organic compounds, exhibit a remarkable versatility
in their reactions. The boron atom in these organoboranes can be readily converted into a wide variety of organic groups under
very mild conditions, providing simple versatile syntheses of organic compounds. Exploration of these substitution reactions
reveal that, with rare exceptions, the organoboranes transfer the alkyl group to other elements of synthetic interest with
complete retention of stereochemistry. Recently we have discovered a method of synthesizing essentially optically pure organoborane
intermediates. These optically active alkyl groups attached to boron can also be transferred with complete retention of optical
activity. Consequently, it is now possible to achieve by a rational synthesis the preparation of almost any optically active
compound with a chiral center, either R- or S-, in essentially 100% enantiomeric excess. 相似文献
8.
A new method for the synthesis of aminovinyl trifluoromethyl ketones was developed. The method is based on the reactions of 4-sulfonyl-1,1,1-trifluorobut-3-ene-2,2-diols with various alkyl-, aryl-, dialkyl-, and alkylarylamines. The stereochemistry of the compounds obtained was studied. 相似文献
9.
Toshiaki Sunazuka Masaki Handa Tatsuya Shirahata Kazuhiko Otoguro Satoshi ōmura 《Tetrahedron》2004,60(36):7845-7859
In the current studies, we used the Kakisawa-Kashman modification of the Mosher NMR method to determine the complete absolute stereochemistry of arisugacins. We also report the convergent total synthesis of (+)-arisugacins A and B by a sequence including (i) ruthenium complex-catalyzed asymmetric reduction of the cyclohexenone derivative; (ii) stereoselective construction of the arisugacin skeleton by a Knoevenagel-type reaction of an α,β-unsaturated aldehyde derivative with production of a 4-hydroxy-2-pyrone derivative as a key reaction; and (iii) stereoselective dihydroxylation to give the diol derivative, followed by deoxygenation. Accordingly, we defined the absolute structures of arisugacins A and B as 4a-(R),6a-(R),12a-(R), and 12b-(S). Finally, we characterized the bioactivities of the synthetic intermediates to understand the structure-activity relationships of the arisugacins. 相似文献
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