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71.
A simple and rapid method was developed for the determination of 20 antibiotics (sulfonamides, tetacyclines, and flumequine) in honey by liquid chromatography tandem mass spectrometry. The proposed method is sensitive (limit of detection 0.5 to 10 ppb for the various antibiotics) and selective. A hydrolysis step ensures the liberation of sugar-bound sulfonamides. The approach has been used to analyze some 300 honey samples. A number of them were found to have exceeded the Swiss limit of 50 ppb. 相似文献
72.
Angelo Albert Francesco Paolo Colonna Maurizio Guerra Bianca F. Bonini Germana Mazzanti Zoltàn Dinya Gian Franco Pedulli 《Journal of organometallic chemistry》1981,221(1):47-55
The radical adducts resulting from the reaction between group IVB organometallic radicals MR3 (M = Si, Ge, Sn; R = alkyl or aryl) and a number of thioketones of the chromone and flavone series have been investigated by ESR spectroscopy. The spectral parameters obtained for these species have been compared with those of similar adducts of the corresponding ketones. Both classes of radicals adopt an orthogonal conformation, and the differences between the former and the latter paramagnetic species can be accounted for by the different electronegativity of oxygen and sulphur. the effects of substitution of the heterocyclic oxygen with a sulphur or selenium atom on the spin density distribution are likewise explained. INDO calculations have been carried out on the model systems CH2XSiH3 (X = O, S). 相似文献
73.
Bruna Bovio
Sandro Calogero
Friedrich E. Wagner
Alfredo Burini
Bianca Rosa Pietroni 《Journal of organometallic chemistry》1994,470(1-2):275-283Reactions of the trinuclear [Au3Rim3] compound (Rim = [μ-1-benzylimidazolato-N3,C2] with several reagents capable of oxidative addition have been investigated by 197Au Mössbauer spectroscopy. The reaction products are either AuI carbene mononuclear and binuclear complexes or trinuclear AuIII and mixed-valence compounds. The X-ray crystal structure of the mixed-valence complex [AuIIIAuI2Rim3I2] has been determined. Two two-coordinate AuI centres show average Au---C and Au---N distances of 2.02(3) and 2.04(2) Å and average C---Au---N angles of 175.0(1.2)°, whereas the four-coordinate AuIII centre gives Au---C and Au---N 1.96(4) and 1.91(3) Å with the C---Au---N angle 170.5(1.6)°, and Au---I average distances 2.598(3) Å, with an I---Au=I angle 175.8(1)°. The Au---Au intramolecular distances [Au(1) Au(2) 3.432(3), Au(1) Au(3) 3.508(3), Au(2) Au(3) 3.464(3) Å] indicate a weak metal-metal interaction. 相似文献
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76.
Manuel W. Thesen Bianca Höfer Marc Debeaux Silvia Janietz Armin Wedel Anna Köhler Hans‐Hermann Johannes Hartmut Krueger 《Journal of polymer science. Part A, Polymer chemistry》2010,48(15):3417-3430
A series of novel styrene derived monomers with triphenylamine‐based units, and their polymers have been synthesized and compared with the well‐known structure of polymer of N,N′‐bis(3‐methylphenyl)‐N,N′‐diphenylbenzidine with respect to their hole‐transporting behavior in phosphorescent polymer light‐emitting diodes (PLEDs). A vinyltriphenylamine structure was selected as a basic unit, functionalized at the para positions with the following side groups: diphenylamine, 3‐methylphenyl‐aniline, 1‐ and 2‐naphthylamine, carbazole, and phenothiazine. The polymers are used in PLEDs as host polymers for blend systems with the following device configuration: glass/indium–tin–oxide/PEDOT:PSS/polymer‐blend/CsF/Ca/Ag. In addition to the hole‐transporting host polymer, the polymer blend includes a phosphorescent dopant [Ir(Me‐ppy)3] and an electron‐transporting molecule (2‐(4‐biphenyl)‐5‐(4‐tert‐butylphenyl)‐1,3,4‐oxadiazole). We demonstrate that two polymers are excellent hole‐transporting matrix materials for these blend systems because of their good overall electroluminescent performances and their comparatively high glass transition temperatures. For the carbazole‐substituted polymer (Tg = 246 °C), a luminous efficiency of 35 cd A?1 and a brightness of 6700 cd m?2 at 10 V is accessible. The phenothiazine‐functionalized polymer (Tg = 220 °C) shows nearly the same outstanding PLED behavior. Hence, both these polymers outperform the well‐known polymer of N,N′‐bis(3‐methylphenyl)‐N,N′‐diphenylbenzidine, showing only a luminous efficiency of 7.9 cd A?1 and a brightness of 2500 cd m?2 (10 V). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3417–3430, 2010 相似文献
77.
78.
Conditions for the separation and determination of benzalkonium chloride (BAC) homologues by CE with UV-detection and CE coupled to MS (IT) using electrospray as ionization source were established. The separation was performed using fused-silica capillaries of 50 microm id and 100 mM acetic acid-ammonium acetate buffer solution at pH 4.5 with 80% of ACN as carrier electrolyte. CE-MS coupling parameters were optimized and methanol-10 mM acetic acid (90:10 v/v) was selected as sheath liquid. Detection limits, based on an S/N of 3:1, were calculated, and values between 0.8 and 1.3 mg/L with CE-ESI/MS and around 0.5 mg/L with CE-ESI-MS/MS, using hydrodynamic injection (15 s, 3.5 kPa), were obtained. Good run-to-run and day-to-day precisions on concentration were achieved with RSDs lower than 8%. Quantitative analysis was carried out by the internal standard method and the calibration curves showed good linearities (r(2) > 0.98). The CE-ESI-MS/MS method was successfully applied to the analysis of BAC in different ophthalmic solutions, allowing the direct determination, identification and confirmation of the BAC homologues presented in these samples. 相似文献
79.
Highly direct total syntheses of phosphatidylinositol (PI), phosphatidylinositol-3-phosphate (PI3P), phosphatidylinositol-3,5-bisphosphate (PI3,5P2), and a range of deoxygenated versions are reported. Each synthesis is carried out to deliver the target in optically pure form. The key step for each synthesis is a catalytic asymmetric phosphorylation reaction that affects desymmetrization of an appropriate myo-inositol precursor. Elaboration to each target compound is then carried out employing a diversity-oriented strategy from the common precursors. In addition to three natural products, several additional streamlined total syntheses of deoxygenated PI analogues are reported. These syntheses set the stage for high-precision biological investigations of polar headgroup/biological target interactions of these membrane-associated signaling molecules. 相似文献
80.
The mean spherical approximation (MSA) can be solved semianalytically for the Gaussian core model (GCM) and yields exactly the same expressions for the energy and the virial equations. Taking advantage of this semianalytical framework, we apply the concept of the self-consistent Ornstein-Zernike approximation (SCOZA) to the GCM: a state-dependent function K is introduced in the MSA closure relation which is determined to enforce thermodynamic consistency between the compressibility route and either the energy or virial route. Utilizing standard thermodynamic relations this leads to two differential equations for the function K that have to be solved numerically. Generalizing our concept we propose an integrodifferential-equation-based formulation of the SCOZA which, although requiring a fully numerical solution, has the advantage that it is no longer restricted to the availability of an analytic solution for a particular system. Rather it can be used for an arbitrary potential and even in combination with other closure relations, such as a modification of the hypernetted chain approximation. 相似文献