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61.
62.
Eberhard Reimann Rainer Hertel Jürgen Krauss 《Monatshefte für Chemie / Chemical Monthly》2008,139(6):673-684
Alkylation of Reissert compounds derived from 3-methylisoquinolines with several 2-cyanobenzylbromides followed by hydrolytic cleavage provided the corresponding 1-benzyl-3-methylisoquinolines. Treatment of the latter with methylmagnesiumiodide caused cyclization to the title compounds rather than formation of 2-acetylbenzylisoquinolines. 相似文献
63.
The photoinduced dynamics in base pairs of adenine and thymine were analyzed by femtosecond pump-probe spectroscopy. On the short-time scale up to a few picoseconds, the characteristic time constants for the dimers are quite similar to the corresponding values of the monomers. This leads to the conclusion that ultrafast intramolecular relaxation proceeds via ππ* and nπ* states of one component within the dimer. On the long-time scale, we obtained a novel time constant of roughly 40 ps for the thymine dimer and the adenine–thymine base pair. This time constant was never observed in the monomers and is tentatively assigned to an intermolecular relaxation process, possibly via a hydrogen transfer state. 相似文献
64.
Gulbinas V Mineviciūte I Hertel D Wellander R Yartsev A Sundström V 《The Journal of chemical physics》2007,127(14):144907
Exciton diffusion in ladder-type methyl-substituted polyparaphenylene film and solution was investigated by means of femtosecond pump-probe spectroscopy using a combined approach, analyzing exciton-exciton annihilation, and transient absorption depolarization properties. We show that the different views on the exciton dynamics offered by anisotropy decay and annihilation are required in order to obtain a correct picture of the energy transfer dynamics. Comparison of the exciton diffusion coefficient and exciton diffusion radius obtained for polymer film with the two techniques reveals that there is substantial short-range order in the film. Also in isolated chains there is considerable amount of order, as revealed from only partial anisotropy decay, which shows that only a small fraction of the excitons move to differently oriented polymer segments. It is further concluded that interchain energy transfer is faster than intrachain transfer, mainly as a result of shorter interchain distances between chromophoric units. 相似文献
65.
Trisporic acids and their biosynthetic precursors represent a family of powerful fungal pheromones and morphogenetic factors. A highly flexible synthetic protocol is described that (i) provides rapid access to nonfunctionalized early trisporoids from beta-ionone, (ii) includes a regiospecific oxidative functionalization of beta-ionone leading to 1-acetoxy-beta-ionone giving access to functionalized trisporoids, and (iii) utilizes a biotransformation of early synthetic trisporoids by growing cells of Blakeslea trispora to prepare late trisporoids including trisporic acids. The same protocol also provides deuterium-labeled trisporoids such as trisporin B [2H3]-19. Administration of [2H3]-19 to growing cells of the (-)-mating type of B. trispora resulted in the formation of the labeled trisporols [2H3]-20 and [2H3]-21. Growing cultures containing both mating types can be used to prepare trisporic acids from early precursors. 相似文献
66.
Lohmeyer M. Bahlmann N. Zhuromskyy O. Hertel P. 《Optical and Quantum Electronics》1999,31(9-10):877-891
Coupled mode theory is applied to an arrangement of three raised strip waveguides with a multimode central strip. We use semivectorial numerically computed modes of the three single isolated waveguides as a basis for propagating supermode analysis of the entire structure. The pronounced polarization dependence of the raised strip guides allows for the design of a conveniently short polarization splitter. We discuss design guidelines and estimate the fabrication tolerances. The accuracy of the coupled mode approach is assessed by comparison with rigorously computed supermodes for comparable two waveguide couplers. Both types of structures indicate the limits in the applicability of the coupled mode model. 相似文献
67.
D. Hertel Yu.V. Romanovskii B. Schweitzer U. Scherf H. Bssler 《Macromolecular Symposia》2001,175(1):141-150
We report on the observation of delayed fluorescence (DF) and phosphorescence (P) from films and dilute frozen solutions of various conjugated polymers of the PPP‐type. The materials differ with respect to the rotational freedom along the polymer backbone. Upon pulsed optical excitation into the S1←S0 transition of the materials, delayed emission occurs on a time scale of μs to ms in solid films at 80 K. The phosphorescence in dilute frozen solution decays monoexponentially with a radiative lifetime on the order of one second. The data analysis reveals that the DF is caused by recombination of geminate electron hole pairs rather than triplet‐triplet annihilation. This conclusion is supported by investigations of the response of the DF to an applied electric field. 相似文献
68.
Winter B Faubel M Hertel IV Pettenkofer C Bradforth SE Jagoda-Cwiklik B Cwiklik L Jungwirth P 《Journal of the American Chemical Society》2006,128(12):3864-3865
The electronic structure of hydrated H3O+ and OH- is probed in a water jet by photoelectron spectroscopy employing 100 eV photons. The first ionization potential for OH- at 9.2 eV and the second ionization potential for H3O+ at 20 eV are resolved, corresponding to the removal of an electron from the 2ppi highest occupied molecular orbital and from the 1e orbital, respectively. These assignments are supported by present computational results based on a combination of molecular dynamics and ab initio calculations. 相似文献
69.
Claudia Hertel Michel Schümichen Jens Lang Jochen Fröhlich 《Flow, Turbulence and Combustion》2013,90(4):785-812
The paper is concerned with a grid adaptation approach based on a moving mesh partial differential equation. A method is proposed for discretizing this equation with a cell-centred finite volume method so that solution-dependent relocation of a fixed number of grid points without changing their topology becomes available as an attractive add-on for many finite volume solvers. Several interpolation strategies to determine appropriate cell corners from moved cell centre points are discussed and compared to each other. For a turbulent hill flow, numerical results are presented for two-dimensional adaptation based on an equidistribution of the gradient of the streamwise velocity and the production of turbulent kinetic energy. 相似文献
70.
Fabritz S Hörner S Könning D Empting M Reinwarth M Dietz C Glotzbach B Frauendorf H Kolmar H Avrutina O 《Organic & biomolecular chemistry》2012,10(31):6287-6293
Polyhedral silsesquioxanes are considered valuable conjugation scaffolds. Nevertheless, only a few examples of silsesquioxane-assembled peptide oligomers have been reported to date. We developed a new bioorthogonal cube-octameric silsesquioxane (COSS) scaffold bearing eight aminooxy coupling sites allowing for the conjugation of diverse peptides via oxime ligation. We found that the coupling efficacy depends on the ligand in view of steric hindrance and electrostatic repulsion. For the first time scaffold-based conjugation of cystine-knot miniproteins having a backbone of about thirty amino acids was successfully accomplished without loss of bioactivity. Atomic force microscopy (AFM) provided further knowledge on the size of COSS verifying them as picoscaffolds growing upon bioconjugation to nano-dimension. 相似文献