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171.
Berger I Hanif M Nazarov AA Hartinger CG John RO Kuznetsov ML Groessl M Schmitt F Zava O Biba F Arion VB Galanski M Jakupec MA Juillerat-Jeanneret L Dyson PJ Keppler BK 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(29):9046-9057
The synthesis and in vitro anticancer activity of dihalogenido(eta6-p-cymene)(3,5,6-bicyclophosphite-alpha-D-glucofuranoside)ruthenium(II) complexes are described. The compounds were characterized by NMR spectroscopy and ESI mass spectrometry, and the molecular structures of dichlorido-, dibromido- and diiodido(eta6-p-cymene)(3,5,6-bicyclophosphite-1,2-O-isopropylidene-alpha-D-glucofuranoside)ruthenium(II) were determined by X-ray diffraction analysis. The complexes were shown to undergo aquation of the first halido ligand in aqueous solution, followed by hydrolysis of a P--O bond of the phosphite ligand, and finally formation of dinuclear species. The hydrolysis mechanism was confirmed by DFT calculations. The aquation of the complexes was markedly suppressed in 100 mM NaCl solution, and notably only very slow hydrolysis of the P--O bond was observed. The complexes showed affinity towards albumin and transferrin and monoadduct formation with 9-ethylguanine. In vitro studies revealed that the 3,5,6-bicyclophosphite-1,2-O-cyclohexylidene-alpha-D-glucofuranoside complex is the most cytotoxic compound in human cancer cell lines (IC50 values from 30 to 300 microM depending on the cell line). 相似文献
172.
Higgins JM Schmitt AL Guzei IA Jin S 《Journal of the American Chemical Society》2008,130(47):16086-16094
We report the synthesis, structural identification, and electrical properties of the first one-dimensional (1-D) nanomaterials of a semiconducting higher manganese silicide (MnSi(2-x)) with widths down to 10 nm via chemical vapor deposition of the single-source precursor Mn(CO)(5)SiCl(3). The complex Nowotny chimney ladder structure of these homologous higher manganese silicides, also referred to as Mn(n)Si(2n-m), MnSi(1.75), or MnSi(1.8), contributes to the excellent thermoelectric performance of the bulk materials, which would be enhanced by phonon scattering due to 1-D nanoscale geometry. The morphology, structure, and composition of MnSi(2-x) nanowires and nanoribbons are examined using electron microscopy and X-ray spectroscopy. Elaborate select area electron diffraction analysis on single-crystal nanowires reveals the phase to be Mn(19)Si(33), one of a series of crystallographically distinct higher manganese silicides that have a Nowotny chimney ladder structure. Electrical transport study of single nanowires shows that they are degenerately doped with a low resistivity (17 mohms x cm) similar to the bulk. 相似文献
173.
Higher oxidation states of americium have long been known; however, options for their preparation in acidic solution are limited. The conventional choice, silver-catalyzed peroxydisulfate, is not useful at nitric acid concentrations above about 0.3 M. We investigated the use of sodium bismuthate as an oxidant for Am (3+) in acidic solution. Room-temperature oxidation produced AmO 2 (2+) quantitatively, whereas oxidation at 80 degrees C produced AmO 2 (+) quantitatively. The efficacy of the method for the production of oxidized americium was verified by fluoride precipitation and by spectroscopic absorbance measurements. We performed absorbance measurements using a conventional 1 cm cell for high americium concentrations and a 100 cm liquid waveguide capillary cell for low americium concentrations. Extinction coefficients for the absorbance of Am (3+) at 503 nm, AmO 2 (+) at 514 nm, and AmO 2 (2+) at 666 nm in 0.1 M nitric acid are reported. We also performed solvent extraction experiments with the hexavalent americium using the common actinide extraction ligand tributyl phosphate (TBP) for comparison to the other hexavalent actinides. Contact with 30% tributyl phosphate in dodecane reduced americium; it was nevertheless extracted using short contact times. The TBP extraction of AmO 2 (2+) over a range of nitric acid concentrations is shown for the first time and was found to be analogous to that of uranyl, neptunyl, and plutonyl ions. 相似文献
174.
Gautier F Destribats M Perrier-Cornet R Dechézelles JF Giermanska J Héroguez V Ravaine S Leal-Calderon F Schmitt V 《Physical chemistry chemical physics : PCCP》2007,9(48):6455-6462
We study oil-in-water emulsions stabilised by pH-sensitive colloidal silica or latex particles. Depending on the composition of the continuous phase, the same type of particles and the same emulsification process lead to emulsions characterised either by large drops densely covered by the particles, or to small droplets which are weakly covered. The two kinetically stable states can be tuned reversibly by using pH or salinity as compositional stimuli. We examine the emulsions' behaviour in these two limiting cases and we discuss the possible mechanisms allowing stabilisation, especially in the case of low surface coverage. 相似文献
175.
Serra D Bosch A Russo DM Rodríguez ME Zorreguieta A Schmitt J Naumann D Yantorno O 《Analytical and bioanalytical chemistry》2007,387(5):1759-1767
This work describes the application of several analytical techniques to characterize the development of Bordetella pertussis biofilms and to examine, in particular, the contribution of virulence factors in this development. Growth of surface-attached
virulent and avirulent B. pertussis strains was monitored in continuous-flow chambers by techniques such as the crystal violet method, and nondestructive methodologies
like fluorescence microscopy and Fourier transform (FT) IR spectroscopy. Additionally, B. pertussis virulent and avirulent strains expressing green fluorescent protein were grown adhered to the base of a glass chamber of
1-μm thickness. Three-dimensional images of mature biofilms, acquired by confocal laser scanning microscopy, were quantitatively
analysed by means of the computer program COMSTAT. Our results indicate that only the virulent (Bvg+) phase of B. pertussis is able to attach to surfaces and develop a mature biofilm. In the virulent phase these bacteria are capable of producing
a biofilm consisting of microcolonies of approximately 200 μm in diameter and 24 μm in depth. FTIR spectroscopy allowed us
not only to follow the dynamics of biofilm growth through specific biomass and biofilm marker absorption bands, but also to
monitor the maturation of the biofilm by means of the increase of the carbohydrate-to-protein ratio. 相似文献
176.
Schmitt N.; Kilian M.; Kobayashi S.-P.; Rossman W. 《Journal London Mathematical Society》2007,75(3):563-581
A theorem on the unitarizability of loop group valued monodromyrepresentations is presented and applied to show the existenceof new families of constant mean curvature surfaces homeomorphicto a thrice-punctured sphere in the simply connected 3-dimensionalspace forms 3, 3 and 3. Additionally, the extended frame forany associated family of Delaunay surfaces is computed. 相似文献
177.
Schmitt M Wagner J Jung G Hempelmann R 《Journal of colloid and interface science》2007,311(2):425-429
Polymer colloids are prepared via radicalic emulsion polymerisation of butylacrylate. Functionalization with amino groups is achieved by copolymerisation of 2-amino-ethylmethacrylates. In order to over-compensate the positive surface charges resulting from the amino groups additionally vinylbenzenesulfonic acid is copolymerized. The size of the resulting particles is controlled by the molar ratio of amino to sulfonic acid groups. The suitability of amino groups for coupling reactions is demonstrated by electrophilic addition of fluorescein-5-isothiocyanate. The resulting particles are characterized by dynamic light scattering and zeta potential measurements as well as by optical spectroscopy. The suitability of labelled particles for optical tracer experiments is demonstrated by fluorescence correlation spectroscopy. 相似文献
178.
Neumann MG Schmitt CC Prieto KR Goi BE 《Journal of colloid and interface science》2007,315(2):810-813
A method based on the aggregate to monomol emission ratio, I(aggr)/I(monomol), was used to determine the minimal hydrotropic concentration (MHC) of aromatic hydrotropes. The main advantage of this method is that it does not require the use of probes or other additives, which might disrupt the aggregation process. Also, it relies on spectrophotometric measurements, which are more sensitive and less arduous than others, like conductivity, light scattering and surface tension. 相似文献
179.
Theiss C Trostmann I Andree S Schmitt FJ Renger T Eichler HJ Paulsen H Renger G 《The journal of physical chemistry. B》2007,111(46):13325-13335
Plants contain water-soluble chlorophyll-binding proteins (WSCPs) that function neither as antennas nor as components of light-induced electron transfer of photosynthesis but are likely constituents of regulatory protective pathways in particular under stress conditions. This study presents results on the spectroscopic properties of recombinant WSCP from cauliflower reconstituted with chlorophyll b (Chl b) alone or with mixtures of Chl a and Chl b. Two types of experiments were performed: (a) measurements of stationary absorption spectra at 77 and 298 K and CD spectra at 298 K and (b) monitoring of laser flash-induced transient absorption changes with a resolution of 200 fs in the time domain of up to 100 ps. On the basis of a theoretical analysis outlined by Renger et al. (J. Phys. Chem. B 2007, 111, 10487) the data obtained in part (a) are interpreted within a model where tetrameric WSCP binds predominantly two Chl molecules in the form of an excitonically coupled "open sandwich" dimer with a tilt angle of about 30 degrees between the chlorin planes. The time-resolved measurements on Chl a/Chl b heterodimers are described by two exponential kinetics with time constants of 400 fs and 7 ps. These kinetics are assumed to reflect a heterogeneous population of WSCPs with Chl dimers either in excitonic coupled "open sandwich" or weakly coupled geometric arrays. The 400 fs component is assigned to excited-state relaxations from the upper to the lower excitonic level of the strongly coupled "open sandwich" dimer, while the 7-8 ps component probably indicates excitation energy transfer from 1Chl b* to Chl a in a dimer array with weak coupling due to significantly longer mutual distances between the chlorin rings. 相似文献
180.
Deep UV resonance Raman micro-spectroscopy (lambda(exc) = 244 nm) was applied for a highly sensitive, selective, and gentle localization of the antimalarial quinine in situ in cinchona bark. The high potential of the method was demonstrated by the detection of small amounts of the alkaloid in the plant material without any further sample preparation, where conventional (non-resonant) Raman microscopy was unsuccessful due to a strong fluorescence background. The resonance Raman spectrum of cinchona bark corresponds well with that of quinine; it can be distinguished from its diastereomer quinidine via the mode at 831 cm(-1), which is shifted to 843 cm(-1) in the case of quinidine. This vibration involves a bending motion within the side chain around the chiral center of quinine. Vibrations belonging to the quinoline ring (important for its antimalarial activity in forming pi-pi-interactions to hemozoin) and the vinyl group are resonantly enhanced in the UV Raman spectra. A convincing mode assignment is derived by means of a combination of NIR Raman spectroscopy and DFT calculations. The Raman spectra of quinine in cinchona bark are modeled by considering a hydrous environment that causes a shift of the band at 1362 compared with 1371 cm(-1) in anhydrous quinine. This intense vibration is therefore sensitive to the presence of an aqueous environment and is assigned mostly to a stretching motion within the quinoline ring. The presented results nicely show the sensitivity of Raman spectroscopy to monitor subtle differences within the molecular structure and the influence of a biological relevant hydrous environment and trace low concentrated pharmaceutical relevant active agents in plant material. 相似文献