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排序方式: 共有204条查询结果,搜索用时 921 毫秒
111.
Broderick EM Guo N Wu T Vogel CS Xu C Sutter J Miller JT Meyer K Cantat T Diaconescu PL 《Chemical communications (Cambridge, England)》2011,47(35):9897-9899
The activity of cerium alkoxide complexes supported by a Schiff base ligand was controlled using redox reagents during the ring-opening polymerization of L-lactide. The rate of L-lactide polymerization was modified by switching in situ between the cerium(III) and cerium(IV) species. 相似文献
112.
Scepaniak JJ Harris TD Vogel CS Sutter J Meyer K Smith JM 《Journal of the American Chemical Society》2011,133(11):3824-3827
The four-coordinate iron(II) phosphoraniminato complex PhB(MesIm)(3)Fe-N═PPh(3) undergoes an S = 0 to S = 2 spin transition with T(C) = 81 K, as determined by variable-temperature magnetic measurements and Mo?ssbauer spectroscopy. Variable-temperature single-crystal X-ray diffraction revealed that the S = 0 to S = 2 transition is associated with an increase in the Fe-C and Fe-N bond distances and a decrease in the N-P bond distance. These structural changes have been interpreted in terms of electronic structure theory. 相似文献
113.
Broderick EM Guo N Vogel CS Xu C Sutter J Miller JT Meyer K Mehrkhodavandi P Diaconescu PL 《Journal of the American Chemical Society》2011,133(24):9278-9281
The activity of an yttrium alkoxide complex supported by a ferrocene-based ligand was controlled using redox reagents during the ring-opening polymerization of L-lactide. The oxidized complex was characterized by X-ray crystallography and (1)H NMR, XANES, and M?ssbauer spectroscopy. Switching in situ between the oxidized and reduced yttrium complexes resulted in a change in the rate of polymerization of L-lactide. Synthesized polymers were analyzed by gel permeation chromatography. Polymerization of trimethylene carbonate was also performed with the reduced and oxidized forms of an indium alkoxide complex. The indium system showed the opposite behavior to that of yttrium, revealing a metal-based dependency on the rate of polymerization. 相似文献
114.
Broderick EM Thuy-Boun PS Guo N Vogel CS Sutter J Miller JT Meyer K Diaconescu PL 《Inorganic chemistry》2011,50(7):2870-2877
Two series of Schiff base metal complexes were investigated, where each series was supported by an ancillary ligand incorporating a ferrocene backbone and different N=X functionalities. One ligand is based on an imine, while the other is based on an iminophosphorane group. Cerium(IV), cerium(III), and yttrium(III) alkoxide complexes supported by the two ligands were synthesized. All metal complexes were characterized by cyclic voltammetry. Additionally, NMR, Mo?ssbauer, X-ray absorption near-edge structure (XANES), and absorption spectroscopies were used. The experimental data indicate that iron remains in the +2 oxidation state and that cerium(IV) does not engage in a redox behavior with the ancillary ligand. 相似文献
115.
116.
Cuyckens F Wassvik C Mortishire-Smith RJ Tresadern G Campuzano I Claereboudt J 《Rapid communications in mass spectrometry : RCM》2011,25(23):3497-3503
Travelling wave ion mobility spectrometry - mass spectrometry (TWIMS-MS) was evaluated as a tool for structural identification of metabolites of small molecule drugs in cases where the exact position of the biotransformation could not be identified by conventional tandem mass spectrometry. Test sets of compounds containing biotransformations at aromatic positions were analyzed. These present a problem for traditional MS methods since an atomic level localization of the biotransformation cannot normally be determined from MS(n) spectra. In addition to ion mobility measurements of the intact metabolite ions, ion mobility measurements of product ions were also made and the results compared with calculated values. This approach reduces the complexity of the problem, making theoretical calculations easier and more predictable when a modeled collision cross section (CCS) is required. A good relative correspondence between theoretical and measured CCSs was obtained allowing the identification of the exact position of the biotransformation. It was also demonstrated that authentic standards with substructures identical to those in the unknown can be used to assign the exact position of the biotransformation. In this approach the identification was based on the comparison of the drift times or CCSs for product ions of the standard, with those of the same product ions in the unknown. 相似文献
117.
118.
Giuseppe Belletti Carola Tortora Indradevi D. Mellema Dr. Paul Tinnemans Dr. Hugo Meekes Prof. Dr. Floris P. J. T. Rutjes Prof. Dr. Svetlana B. Tsogoeva Prof. Dr. Elias Vlieg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(4):839-844
Viedma ripening is a deracemization process that has been used to deracemize a range of chiral molecules. The method has two major requirements: the compound needs to crystallize as a conglomerate and it needs to be racemizable under the crystallization conditions. Although conglomerate formation can be induced in different ways, the number of racemization methods is still rather limited. To extend the scope of Viedma ripening, in the present research we applied UV-light-induced racemization in a Viedma ripening process, and report the successful deracemization of a BINOL derivative crystallizing as a conglomerate. Irradiation by UV light activates the target compound in combination with an organic base, required to promote the excited-state proton transfer (ESPT), leading thereafter to racemization. This offers a new tool towards the development of Viedma ripening processes, by using a cheap and “green” catalytic source like UV light to racemize suitable chiral compounds. 相似文献
119.
120.
E. Mainka E. Gantner A. v. Baeckmann 《Journal of Radioanalytical and Nuclear Chemistry》1976,32(2):401-411
The work of the Analytical Department of the “Institut für Radiochemie der Gesellschaft für Kernforschung, Karlsruhe”, which
is mainly the analysis of the nuclear fuel cycles is described.
Seit 1. 9. 75 IAEA Wien 相似文献
Seit 1. 9. 75 IAEA Wien 相似文献