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71.
Organometallic 5d6 Transition Metal Complexes of 1‐Methyl‐(2‐alkylthiomethyl)‐1H‐benzimidazole Ligands: Structures and Electrochemical Oxidation The complexes [(mmb)Re(CO)3Cl], [(mtb)Re(CO)3Cl], [(mmb)OsCl(Cym)](PF6) and [(Cym)OsCl(mtb)](PF6) where Cym = p‐cymene, mmb = 1‐methyl‐(2‐methylthiomethyl)‐1H‐benzimidazole and mtb = 1‐methyl‐(2‐tert‐butylthiomethyl)‐1H‐benzimidazole were synthesized and, except for the latter, structurally characterized. In comparison with other late transition metal compounds of these N‐S chelate ligands the rhenium(I) systems exhibit a balanced coordination to both N and S donor atoms. Anodic one‐electron oxidation produces EPR‐silent rhenium(II) states whereas the osmium(III) species [(mmb)OsCl(Cym)]2+ could be identified via EPR and UV/VIS spectroelectrochemistry. 相似文献
72.
Summary The influence of different reversed-phase packings and the addition of acidic modifiers to the mobile phase was observed on
the separation of basic and neutral polypeptide antibiotics by gradient elution. A dependence of pore size, coverage, reaction
type and endcapping of the packings was not observed. Nevertheless, not all reversed-phase packings were suitable for the
separation of polypeptides, especially of basic molecules. The addition of phosphoric or perchloric acid to the mobile phase
prevented adsorption of the basic polypeptide antibiotics on the stationary phase. 相似文献
73.
74.
André Vanderbauwhede Bernold Fiedler 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1992,43(2):292-318
We show that in conservative systems each non-degenerate homoclinic orbit asymptotic to a hyperbolic equilibrium possesses an associated family of periodic orbits. The family is parametrized by the period, and the periodic orbits accumulate on the homoclinic orbit as the period tends to infinity. A similar result holds for symmetric homoclinic orbits in reversible systems. Our results extend earlier work by Devaney and Henrard, and provide a positive answer to a conjecture of Strömgren. We present a unified approach to both the conservative and the reversible case, based on a technique introduced recently by X.-B. Lin.Dedicated to Prof. Klaus Kirchgässner on the occasion of his sixtieth birthday 相似文献
75.
76.
Pill J Kloetzer HM Issaeva O Kraenzlin B Deus C Kraemer U Sadick M Fiedler F Gretz N 《Analytical and bioanalytical chemistry》2005,382(1):59-64
There is an obvious and growing medical need for an accurate determination of kidney function in the diagnosis and management of renal diseases. The glomerular filtration rate (GFR) is the accepted gold standard measurement of kidney function. Several approaches to estimate the GFR are available, but most of them are inconvenient and, therefore, of limited acceptance. A new method of quantification with fluorescein-isothiocyanate (FITC) sinistrin (FS), a novel GFR marker, has been evaluated. The method is based on the fluorescence label of FS and can be performed with a standard fluorometer. To control the interference of protein with the fluorescence signal, a calibration function was developed. The accuracy of the fluorometric method established is comparable to the so-called gold standard of enzymatic determination of polyfructosan. Moreover, FS is easy to handle and requires low-cost instruments. Our results demonstrate the potential of the direct fluorometric analysis of the new FITC-labelled marker of being a precise, simple, rapid and cost-effective method for diagnosing disturbed kidney function and monitoring its treatment efficacy. The dramatic decrease in analytical effort will result in a significantly higher acceptability of GFR determination. 相似文献
77.
J. Fiedler L. Frey F. Steigerwald H. Langhoff T. Griegel K. Petkau W. Hammer 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1988,11(2):141-145
Mixtures of rare-gases (Rg) and alkali vapors (A) were excited by helium and argon ions. VUV transitions observed between 131.1 nm and 189.9 nm were ascribed to the decay of (RgA)+ ions where Rg=Kr, Xe and A=Cs, Rb, K, Na, Li. In the (ArA)+ systems (A=Rb, K, Na, Li) transitions appeared between 114.1 nm and 124.7 nm. Since the final state is only weakly bound, the (RgA)+ ions seem to be promising candidates for storage media of VUV lasers. 相似文献
78.
Teplý F Stará IG Starý I Kollárovic A Saman D Rulísek L Fiedler P 《Journal of the American Chemical Society》2002,124(31):9175-9180
An original approach to helicene frameworks exploiting atom economic isomerization of appropriate energy-rich aromatic cis,cis-dienetriynes has been developed. The new paradigm provides nonphotochemical syntheses of helicenes based on the easy, convergent, and modular assembly of key cis,cis-dienetriynes and their nickel(0)-catalyzed [2+2+2] cycloisomerization. The potential of the methodology is underlined by the syntheses of the parent [5]helicene (2), 7,8-dibutyl[5]helicene (23), [6]helicene (24), and [7]helicene (25). The approach can be adapted to prepare functionalized helicenes as exemplified by the eight-step synthesis of 7,8-dibutyl-2,3-dimethoxy[6]helicene (34). Density functional theory (DFT) calculations showed that bis[2-((1Z)-1-buten-3-ynyl)phenyl]acetylene (1) and isomeric [5]helicene (2) differ enormously in the Gibbs energy content (DeltaG = -136.6 kcal x mol(-1)) to favor highly the devised intramolecular simultaneous construction of three aromatic rings. 相似文献
79.
Schraml J Sýkora J Fiedler P Roithová J Mindl J Blechta V Císarová I Exner O 《Organic & biomolecular chemistry》2004,2(16):2311-2314
The structures of four N,O-diacylhydroxylamines (RCOHNOCOR', R, R'= Me, Ph) were determined in the solid state by X-ray diffraction and studied by NMR and IR spectroscopies in solution. The interpretation of the results was supported by ab-initio calculations of various tautomers and conformers, rotational barriers and chemical shifts. The results indicate the absence of OH tautomers (R-C(OH)=N-O-C(O)-R', N-acyloxyimidic acid); the NH tautomers (R-C(O)-NH-O-C(O)-R', O-acylhydroxamic acid) are present in DMSO solutions as equilibrium mixtures of a few conformers, their exchange being the likely source of 15N and 13C NMR line broadening. 相似文献
80.
Sandeep Ghumaan Biprajit Sarkar Mahendra P. Patil Jan Fiedler Raghavan B. Sunoj Wolfgang Kaim Goutam Kumar Lahiri 《Polyhedron》2007
The complexes (μ3-L1/L2)[Ru(acac)2]3, acac− = 2,4-pentanedionato, L1 = 2,3,8,9,14,15-hexachlorodiquinoxalino[2,3-a:2′,3′-c]phenazine and L2 = 2,3,8,9,14,15- hexamethyldiquinoxalino[2,3-a:2′,3′-c]phenazine, undergo stepwise one-electron oxidation involving a total of three electrons and stepwise one-electron reduction with three (L2) or four electrons (L1). All reversibly accessible states were characterized by UV–Vis–NIR spectroelectrochemistry. Oxidation leads to mixed-valent intermediates {(μ3-L)[Ru(acac)2]3}+ and {(μ3-L)[Ru(acac)2]3}2+ of which the RuIIIRuIIRuII combinations exhibit higher comproportionation constants Kc than the RuIIIRuIIIRuII states – in contrast to a previous report for the unsubstituted parent systems {(μ3-L3)[Ru(acac)2]3}+/2+, L3 = diquinoxalino[2,3-a:2′,3′-c]phenazine. No conspicuous inter-valence charge transfer absorptions were observed for the mixed-valent intermediates in the visible to near-infrared regions. The monocations and monoanions were characterized by EPR spectroscopy, revealing rhombic ruthenium(III) type signals for the former. Electron addition produces ruthenium(II) complexes of the reduced forms of the ligands L, a high resolution EPR spectrum with 14N and 35,37Cl hyperfine coupling and negligible g anisotropy was found for {(μ3-L1)[Ru(acac)2]3}−. DFT calculations of (μ3-L1)[Ru(acac)2]3 confirm several ligand-centered low-lying unoccupied MOs for reduction and several metal-based high-lying occupied MOs for electron withdrawal, resulting in low-energy metal-to-ligand charge transfer (MLCT) transitions. 相似文献