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661.
W. Carrillo‐Cabrera R. Cardoso Gil M. Somer
. Persil H. G. von Schnering 《无机化学与普通化学杂志》2003,629(4):601-608
Na12Ge17 is prepared from the elements at 1025 K in sealed niobium ampoules. The crystal structure reinvestigation reveals a doubling of the unit cell (space group:P21/c; a = 22.117(3)Å, b = 12.803(3)Å, c = 41.557(6)Å, β = 91.31(2)°, Z = 16; Pearson code: mP464), furthermore, weak superstructure reflections indicate an even larger C‐centred monoclinic cell. The characteristic structural units are the isolated cluster anions [Ge9]4— and [Ge4]4— in ratio 1:2, respectively. The crystal structure represents a hierarchical cluster replacement structure of the hexagonal Laves phase MgZn2 in which the Mg and Zn atoms are replaced by the Ge9 and Ge4 units, respectively. The Raman spectrum of Na12Ge17 exhibits the characteristic breathing modes of the constituent cluster anions at ν = 274 cm—1 ([Ge9]4—) and ν = 222 cm—1 ([Ge4]4—) which may be used for identification of these clusters in solid phases and in solutions. Raman spectra further prove that Na12Ge17 is partial soluble both in ethylenediamine and liquid ammonia. The solution and the solid extract contain solely [Ge9]4—. The remaining insoluble residue is Na4Ge4. By heating the solvate Na4Ge9(NH3)n releases NH3 and decomposes irreversibly at 742 K, yielding Na12Ge17 and Ge. 相似文献
662.
Humberto César Chaves Fernandes 《International Journal of Infrared and Millimeter Waves》1996,17(8):1419-1430
The theory and numerical results of the asymmetric single and coupled bilateral and unilateral finlines and arbitrary antipodal finline considering the attenuation of the substrate are presented. Results are given to the complex propagation constant. The full wave analysis of the Transverse Transmission Line — TTL method is used in the FTD. Applying the moment method the complex propagation constant, including the attenuation constant and the phase constant, are obtained. The effective dielectric constant, eff,, and the characteristic impedance are also calculated. The results are compared with the references, and news results are presented for these parameters. 相似文献
663.
664.
L. Harivardhan Reddy Humberto Ferreira Catherine Dubernet Sinda Lepetre Mouelhi Didier Desmaële Bernard Rousseau Patrick Couvreur 《Journal of nanoparticle research》2008,10(5):887-891
Recently, we had discovered that the linkage of nucleoside analogues to squalene, a precursor in the sterol biosynthesis,
led to amphiphilic molecules, which self-organized in water as nanoassemblies of 100–300 nm in diameter, irrespective of the
nucleoside analogue used. Thus, it was observed that the 4-(N)-trisnorsqualenoylgemcitabine (SQdFdC), the squalenoyl prodrug of the anticancer nucleoside analogue gemcitabine, was impressively
more active than its parent compound gemcitabine, both in vitro and in vivo on experimental leukaemia. Since squalene, which
is a natural constituent of shark liver and olive oil, is known to be absorbed orally, we investigated in this short note
the absorption and tissue distribution of 3H-radiolabelled SQdFdC nanoassemblies comparatively to 3H-gemcitabine after oral administration to mice. Whereas gemcitabine was found to be rapidly absorbed (t
max = 1 h), this compound underwent a rapid clearance from the plasma. Conversely, the SQdFdC nanoassemblies displayed slower
absorption followed by the progressive tissue accumulation, and they exhibited a lower clearance rate. The accumulation of
the SQdFdC nanoassemblies in tissues such as pancreas, thymus, lung, liver and spleen (except at 1 h post-administration)
was similar to that of the gemcitabine, yet exhibited significantly greater penetration and retention into the stomach and
intestinal tissues comparatively to gemcitabine. Thus, the SQdFdC nanoassemblies could be of potential interest in the treatment
of gastrointestinal tumours by oral route. 相似文献
665.
Alexander Trujillo Mauricio Fuentealba David Carrillo Carolina Manzur Jean-René Hamon 《Journal of organometallic chemistry》2009,694(9-10):1435-1440
The synthesis of the new air and thermally stable orange neutral dinuclear iron–nickel unsymmetrical Schiff base complex, [8-(2-oxo,5-allyloxo-phenyl)-4,7-diaza-3-methyl-1-ferrocenyl-1-one-octa-1,3,7-trienato]nickel(II) (2), was achieved via the Williamson coupling reaction between the 2-oxo,5-hydroxyphenyl precursor 1 and allyl chloride in the presence of base. Complex 2 was isolated in 68% yield and characterized by IR, UV–Vis, 1H and 13C NMR spectroscopy, HRMS and authenticated by a single crystal X-ray diffraction analysis. The organometallic/inorganic hybrid complex 2 consists in a ferrocenyl fragment linked to a classical Werner-type complex made of an unsymmetrical quadridentate N2O2 Schiff base ligand with a pendant allyl ether functionality as a potential anchoring group. The Ni(II) center displays a square-planar geometry with the nitrogen and oxygen atoms occupying mutually trans positions. The structure of 2 · H2O shows that the water crystallization molecule interacts through two distinct intermolecular hydrogen bonds with the two oxygen atoms of the tetradentate N2O2 acyclic chelating ligand, forming in the solid state, a distorted six-membered ring. 相似文献
666.
Humberto Prado 《Semigroup Forum》2008,77(3):456-462
We study stability properties of certain evolution equations including the fractional Cauchy problem. Under some spectral
assumptions these equations are governed either by a resolvent or a regularized resolvent or a k-convoluted semigroup. We investigate the long time behavior for bounded solutions by a direct application of the ergodic
theorems for regularized resolvents of Lizama and Prado (J. Approx. Theory 122:42–61, 2003), Prado (Semigroup Forum 73:243–252, 2006). We apply our results to the qualitative study of the fractional diffusion-wave equation on L
p
(ℝ).
The author is partially supported under FONDECYT Grant no 1070127. 相似文献
667.
Ma. Eulalia Vanegas Raúl Quijada Daniel Serafini Griselda B. Galland Humberto Palza 《Journal of Polymer Science.Polymer Physics》2008,46(8):798-806
Syndiotactic polypropylenes and their copolymers with 1‐olefins were synthesized using two metallocene/MAO catalytic systems, and the effect of the different microstructures on nonisothermal crystallization and subsequent melting was studied. Using differential scanning calorimetry (DSC) it was observed that samples with lower content of defects showed crystallization on cooling from the melt, and a double melting peak in the subsequent heating scan, the latter associated with melt, recrystallization and remelt processes that it was confirmed by its nonreversing exothermic process found by means of temperature modulated DSC (MDSC). However, polymers with high amount of defects showed cold crystallization on heating followed by a melting process, that it was observed by MDSC. Wide angle X‐ray diffraction was used for characterizing the changes of crystalline forms in relationship with crystallization process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 798–806, 2008 相似文献
668.
Plastic-Adherent DNA Aptamer-Magnetic Bead and Quantum Dot Sandwich Assay for Campylobacter Detection 总被引:1,自引:0,他引:1
John G. Bruno Taylor Phillips Maria P. Carrillo Randy Crowell 《Journal of fluorescence》2009,19(3):427-435
DNA aptamers were developed against MgCl2-extracted surface proteins from Campylobacter jejuni. The two highest affinity aptamers were selected for use in a magnetic bead (MB) and red quantum dot (QD)-based sandwich
assay scheme. The assay was evaluated using both heat-killed and live C. jejuni and exhibits detection limits as low as an average of 2.5 colony forming unit (cfu) equivalents in buffer and 10–250 cfu
in various food matrices. The assay exhibits low cross-reactivity with bacterial species outside the Campylobacter genus, but exhibits substantial cross-reactivity with C. coli and C. lari. The assay was evaluated with a spectrofluorometer and a commercially available handheld fluorometer, which yielded comparable
detection limits and ranges. Remarkably, the sandwich assay components adhere to the inside face of polystyrene cuvettes even
in food matrices near neutral pH, thereby enabling a rapid homogeneous assay, because fluorescence is concentrated to a small,
thin planar area and background fluorescence from the bulk solution is minimized. The plastic cuvette-adherent technology
coupled to a sensitive handheld fluorometer may enable rapid (15–20 min), portable detection of foodborne pathogens from “farm-to-fork”
by obviating the slow enrichment culture phase used by other food safety tests. 相似文献
669.
J. A. Carrillo A. Jüngel P. A. Markowich G. Toscani A. Unterreiter 《Monatshefte für Mathematik》2001,10(5):1-82
We analyse the large-time asymptotics of quasilinear (possibly) degenerate parabolic systems in three cases: 1) scalar problems with confinement by a uniformly convex potential, 2) unconfined scalar equations and 3) unconfined systems. In particular we are interested in the rate of decay to equilibrium or self-similar solutions. The main analytical tool is based on the analysis of the entropy dissipation. In the scalar case this is done by proving decay of the entropy dissipation rate and bootstrapping back to show convergence of the relative entropy to zero. As by-product, this approach gives generalized Sobolev-inequalities, which interpolate between the Gross logarithmic Sobolev inequality and the classical Sobolev inequality. The time decay of the solutions of the degenerate systems is analyzed by means of a generalisation of the Nash inequality. Porous media, fast diffusion, p-Laplace and energy transport systems are included in the considered class of problems. A generalized Csiszár–Kullback inequality allows for an estimation of the decay to equilibrium in terms of the relative entropy. 相似文献
670.
Julia‐Maria Hübner Wilder Carrillo‐Cabrera Yurii Prots Matej Bobnar Ulrich Schwarz Yuri Grin 《Angewandte Chemie (International ed. in English)》2019,58(37):12914-12918
The silicon‐rich cage compound MgSi5 was obtained by high‐pressure high‐temperature synthesis. Initial crystal structure determination by electron diffraction tomography provided the basis for phase analyses in the process of synthesis optimization, finally facilitating the growth of single crystals suitable for X‐ray diffraction experiments. The crystal structure of MgSi5 (space group Cmme, Pearson notation oS24, a=4.4868(2) Å, b=10.1066(5) Å, and c=9.0753(4) Å) constitutes a new type of framework of four‐bonded silicon atoms forming Si15 cages enclosing the Mg atoms. Two types of smaller Si8 cages remain empty. The atomic interactions are characterized by two‐center two‐electron bonds within the silicon framework. In addition, there is evidence for multi‐center Mg?Si bonding in the large cavities of the framework and for lone‐pair‐like interactions in the smaller empty voids. 相似文献