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201.
202.
P Samorí A Fechtenk?tter F J?ckel T B?hme K Müllen J P Rabe 《Journal of the American Chemical Society》2001,123(46):11462-11467
A series of soluble hexabenzocoronene (HBC) derivatives with pendant optically active (S)-3,7-dimethyloctanyl and (R,S)-3,7-dimethyloctanyl (mixture of stereoisomers) hydrocarbon side chains with and without a phenylene spacer were assembled into differently ordered arrays at the interface between a solution and the basal plane of highly oriented pyrolytic graphite (HOPG). Molecularly resolved scanning tunneling microscopy (STM) images revealed that all derivatives self-assemble into oriented crystals in quasi-two dimensions. However, while for the alkyl-substituted HBCs (1,4) all of the single aromatic cores within a monolayer exhibit the same contrast in the STM, the single aromatic cores with a phenylene group between the alkyl side chains and the aromatic core (2a,2b,3) exhibit different contrasts within a monolayer. For the disks carrying racemic branched or n-alkyl side chains (2b,3) a random distribution of the two different contrasts within the 2D-crystal is observed, while the optically active phenylene-alkyl-substituted HBC (2a) exhibits a periodical distribution of three contrasts within the monolayer. We attribute the different contrasts of the aromatic cores in the presence of the phenylene groups to a loss of the planarity of the whole molecule and different conformations, which allow the conjugated disks to attain different equilibrium positions above the surface of HOPG. In the case of the optically active side chains a regular superstructure with three distinctly different positions such as in a staircase is attained. The self-assembly processes are governed by the interplay of intramolecular as well as intermolecular and interfacial interactions. In the present case, the interactions may induce both the molecules to acquire well distinct positions along the z axis and to adopt different conformations. The reported results open new avenues of exploration. For instance, the different couplings of conjugated molecules with the substrate at different separations can be investigated by means of scanning tunneling spectroscopy (STS). Furthermore, experiments on the STM tip-induced switching of single molecules embedded in a monolayer appear feasible. 相似文献
203.
204.
The Crystal Packings of (PPh4)2[NiCl4] · 2 MeCN and PPh4[CoCl0.6Br2.4(NCMe)] (PPh4)2[NiCl4] · 2 MeCN was obtained from the reaction of PPh4Cl and NiCl2 in acetonitrile in the presence of S2Cl2, PPh4[Cl2H] being a side product. The product of the reaction of CoS2 with S2Br2 (containing rests of S2Cl2) at 400 °C was treated with PPh4Br in acetonitrile yielding PPh4Br3 and PPh4[CoCl0.6Br2.4(NCMe)]. The crystal structures of the title compounds were determined by X‐ray diffraction. (PPh4)2[NiCl4] · 2 MeCN (space group I 4, a = 1839.3 pm, c = 1375.3 pm) has a crystal packing derived from the BiPh4[ClO4] structure type with a fourfold increased unit cell and one half of the ClO4– positions substituted by pairsof acetonitrile molecules. The crystal structure of PPh4[CoCl0.6Br2.4(NCMe)] (space group I41/a, a = 1804.7 pm, c = 3198.8 pm) is related to the AsPh4[RuNCl4] type with an eightfold increased unit cell. The [CoCl0.6Br2.4(NCMe)]– ions are disordered in two orientations and some halogen positions are randomly occupied by Cl and Br atoms. Family trees of group–subgroup relations show the symmetry relations. 相似文献
205.
Potassium Tetrachlorooxomolybdate(V), KMoOCl4 KMoOCl4 was obtained at 200 °C in small yield as a side‐product from the reaction of S2Cl2 with molybdenum which contained 0.7% of potassium (the main product was MoS2Cl3). Attempts to increase the yield by adding stoichiometric amounts of KOH or of KCl + H2O failed. An attempt to produce KMoOCl4 by the reduction of MoOCl4 with KI yielded K3Mo2Cl9 and a small amount of K2MoOCl5. The crystal structure of KMoOCl4 is monoclinic, space group P21/c, a = 657,1; b = 901,6; c = 2327,3 pm; β = 92,81°, Z = 8. Square‐pyramidal MoOCl4– ions are associated to infinite zigzag chains by Mo…Cl contacts. 相似文献
206.
207.
Vivekanantan S. Iyer Kimihiro Yoshimura Volker Enkelmann Rebekka Epsch Jürgen P. Rabe Klaus Müllen 《Angewandte Chemie (International ed. in English)》1998,37(19):2696-2699
At the limits of analytical investigation one finds the nanodimensional C60 graphite segment 1 , which, thanks to its long-chain alkyl substituents, is soluble. Monolayers of 1 on graphite can be characterized by scanning tunneling microscopy. 相似文献
208.
Gerd W. Rabe Sohrab Kheradmandan Louise M. Liable-Sands Ilia A. Guzei Arnold L. Rheingold 《Angewandte Chemie (International ed. in English)》1998,37(10):1404-1407
A coordination environment reminiscent of a paddle-wheel is exhibited by aryl groups about one of the two cesium ions in CsP(H)Dmp (Dmp=2,6-dimesitylphenyl; structure depicted on the right), which has now been synthesized and is found to exhibit Cs+{Cs2[P(H)Dmp]3}− contact ion pairs in the solid state. In contrast, the analogous rubidium compound displays a Rb4P4 cube as the central structural motif. 相似文献
209.
Potassium Heptachlorodioxodimolybdate(V), KMo2O2Cl7 KMo2O2Cl7 was obtained at 400 °C from the reaction of SCl2 with molybdenum which contained traces of potassium. Its crystal structure is monoclinic, space group C2/c, a = 1094.1, b = 1139.1, c = 1018.0 pm, β = 110.16°, Z = 4. In the Mo2O2Cl7– ion two coordination octahedra share a common face with three chlorine atoms. The crystal structure can be derived from the CsNiCl3 type by vacating one third of the Ni and two thirds of the Cs positions. The crystallographic group-subgroup relationship is given. 相似文献
210.
Jan Rinkel Dr. Patrick Rabe Dr. Paolina Garbeva Prof. Dr. Jeroen S. Dickschat 《Angewandte Chemie (International ed. in English)》2016,55(43):13593-13596
Stereospecifically labelled precursors were subjected to conversion by seven bacterial sesquiterpene cyclases to investigate the stereochemistry of their initial 1,10‐cyclisation‐1,3‐hydride shift cascades. Enzymes with products of known absolute configuration showed a coherent stereochemical course, except for (?)‐α‐amorphene synthase, for which the obtained results are better explained by an initial 1,6‐cyclisation. The link between the absolute configuration of the product and the stereochemical course of the 1,3‐hydride shifts enabled assignment of the absolute configurations of three enzyme products, which were confirmed independently through the absolute configuration of the common byproduct germacrene D‐4‐ol. 相似文献