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961.
Luciana Vera‐Candioti María J. Culzoni Alejandro C. Olivieri Héctor C. Goicoechea 《Electrophoresis》2008,29(22):4527-4537
Drug monitoring in serum samples was performed using second‐order data generated by CE‐DAD, processed with a suitable chemometric strategy. Carbamazepine could be accurately quantitated in the presence of its main metabolite (carbamazepine epoxide), other therapeutic drugs (lamotrigine, phenobarbital, phenytoin, phenylephrine, ibuprofen, acetaminophen, theophylline, caffeine, acetyl salicylic acid), and additional serum endogenous components. The analytical strategy consisted of the following steps: (i) serum sample clean‐up to remove matrix interferences, (ii) data pre‐processing, in order to reduce the background and to correct for electrophoretic time shifts, and (iii) resolution of fully overlapped CE peaks (corresponding to carbamazepine, its metabolite, lamotrigine and unexpected serum components) by the well‐known multivariate curve resolution‐alternating least squares algorithm, which extracts quantitative information that can be uniquely ascribed to the analyte of interest. The analyte concentration in serum samples ranged from 2.00 to 8.00 mg/L. Mean recoveries were 102.6% (s=7.7) for binary samples, and 94.8% (s=13.5) for spiked serum samples, while CV (%)=4.0 was computed for five replicate, indicative of the acceptable accuracy and precision of the proposed method. 相似文献
962.
Vera Stehr Reinhold F. Fink Carsten Deibel Bernd Engels 《Journal of computational chemistry》2016,37(23):2146-2156
The prediction of substance‐related charge‐transport properties is important for the tayloring of new materials for organic devices, such as organic solar cells. Assuming a hopping process, the Marcus theory is frequently used to model charge transport. Here another approach, which is already widely used for exciton transport, is adapted to charge transport. It is based on the spectral overlap of the vibrational donor and acceptor spectra. As the Marcus theory it is derived from Fermi's Golden rule, however, it contains less approximations, as the molecular vibrations are treated quantum mechanically. In contrast, the Marcus theory reduces all vibrational degrees of freedom to one and treats its influence classically. The approach is tested on different acenes and predicts most of the experimentally available hole mobilities in these materials within a factor of 2. This represents a significant improvement to values obtained from Marcus theory which is qualitatively correct but frequently overestimates the mobilities by factors up to 10. Furthermore, the charge‐transport properties of two derivatives of perylene bisimide are investigated. © 2016 Wiley Periodicals, Inc. 相似文献
963.
Hefti M Holenstein F Albert I Looser H Luginbuehl V 《Photochemistry and photobiology》2011,87(1):235-241
5-Aminolevulinic acid (5-ALA) is a natural precursor of protoporphyrin IX (PpIX), which can be used as a photosensitizer in photodynamic therapy (PDT). Accumulation of PpIX in benign meningioma cells has been observed previously, its exploitation for PDT, however, was discouraged by inconsistent results. To evaluate PDT for benign meningiomas, we investigated PpIX synthesis in two human meningioma cell lines (HBL-52 and BEN-MEN-1), their respective extracellular loss of PpIX and corresponding ferrochelatase (FECH) activity as well as their susceptibility to PDT. We demonstrated PpIX production after 5-ALA administration and minor loss to the extracellular space in both cell lines. However, significantly more (up to five times) PpIX was accumulated in BEN-MEN-1 as compared with HBL-52 cells. FECH activity was 2.7-fold higher in HBL-52 compared with BEN-MEN-1 cells and accordingly higher FECH levels could be shown in HBL-52 cells by Western blot analysis. BEN-MEN-1 cells were much more sensitive to PDT and cells could be almost completely killed by irradiation doses of 2 J cm(-2) , whereas HBL-52 showed only an insufficient response at this irradiation dose. We conclude that differences in intracellular PpIX concentrations between HBL-52 and BEN-MEN-1 benign meningioma cells were mainly due to differences in FECH activity and that these differences correspond to their susceptibility to 5-ALA-induced PDT. 相似文献
964.
Prof. Dr. Hans‐Jörg Deiseroth Joachim Maier Katja Weichert Vera Nickel Shiao‐Tong Kong Christof Reiner 《无机化学与普通化学杂志》2011,637(10):1287-1294
Possible three‐dimensional diffusion pathways of lithium ions in crystalline lithium argyrodites are discussed based on earlier studies of local dynamics and site preferences. The specific Li‐ionic conductivities of the lithium argyrodites Li7PS6 and Li6PS5X (X: Cl, Br, I) and their temperature dependences are measured by impedance spectroscopy using different electron‐blocking and ion‐blocking electrode systems. Measurements were carried out between 160 K and 550 K depending on the respective sample. Bulk and grain boundary contributions and the influence of sample preparation are discussed. Typical values for the ionic conductivities at room temperature are in the range 10–7 to 10–5 S · cm–1 and at 500 K between 10–6 and 10–3 S · cm–1. Thermal activation energies are in the range 0.16 to 0.56 eV. The electronic conductivity at room temperature was measured by polarization measurements for the samples Li6PS5X (X: Cl, Br) and was shown to be in the order of magnitude of 10–8 S · cm–1. Chemical diffusion coefficients of lithium were calculated based on the polarization measurements. For Li6PS5Br a high value of 3.5 × 10–6 cm2 · s–1 was found. 相似文献
965.
Three new cembrane‐based diterpenes possessing the rare 3,14‐oxa‐bridged moiety were isolated from the hexane extract of a southwestern Caribbean gorgonian octocoral, Eunicea pinta, together with seven known cembranoid diterpenes. The structures of pintoxolanes A–C ( 1 – 3 , resp.), including their relative configurations, were deduced from spectroscopic data and chemical‐correlation experiments. Experimental evidence hinting to a plausible biogenesis of the 3,14‐oxalane moiety is provided. Preliminary cytotoxicity data for compounds 1 – 3 toward human cancer cell lines are also provided. 相似文献
966.
F. Geoffrey N. Cloke Peter B. Hitchcock Philip Hunnable John F. Nixon Lszlo Nyulszi Edgar Niecke Vera Thelen 《Angewandte Chemie (International ed. in English)》1998,37(8):1083-1086
The sterically demanding groups on the tricoordinate phosphorus atom, the π-electron acceptors substituted on the ring, and the dicoordinate phosphorus atoms within the ring are the most significant factors contributing to the planarity and aromaticity of the 1,2,4-triphosphole ring in 1 . The Bird aromaticity index for 1 shows that it has the most pronounced aromatic character of all known phospholes. 相似文献
967.
Maria N. Timofeeva;Evgeniy A. Paukshtis;Valentina N. Panchenko;Kristina I. Shefer;Vera I. Isaeva;Leonid M. Kustov;Evgeniy Yu. Gerasimov; 《European journal of organic chemistry》2019,2019(26):4215-4225
Zeolitic imidazolate framework (ZIF-8, Zn(2-meIm)2) and composites based on ZIF-8 and alumina nanofibers (NafenTM), i.e. ZIF-8/Nafen, were demonstrated to be efficient heterogeneous catalysts for the reaction of methanol with propylene oxide to produce propylene glycol methyl ether (PGME), which is a member of the family of glycol ether solvents used for a wide variety of consumer products and industrial applications. Both the reaction rate and the selectivity toward PGME were found to decrease with increasing crystal size of the ZIF-8 material, which was related to the change in the number of basic sites and their accessibility. The investigation of ZIF-8/Nafen composites revealed the dependence of their catalytic performance on the amount of the ZIF-8 component. In particular, the activity was affected by the crystal size of the ZIF-8 material and the nature of acid-base sites in its framework. 相似文献
968.
Vera Aparecida de Oliveira Tiera Marcio José Tiera Neide Aparecida Blaz Vieira Bruno Rochetti do Amaral Rogério Zambelli Pires 《Journal of Dispersion Science and Technology》2013,34(8):1121-1128
The interaction between cationic surfactants and isopropylacrylamide-acrylic acid-ethyl methacrylate (IPA:AA:EMA) terpolymers has been investigated using steady-state fluorescence and spectrophotometric measurements to assess the effect of the polymer composition on the aggregation process and terpolymers’ thermosensitivities. Micropolarity studies using pyrene show that the interaction of cationic surfactants with IPA:AA:EMA terpolymers occurs at surfactant concentrations much smaller than that observed for the pure surfactant in aqueous solution. The critical aggregation concentration (CAC) values decrease with both the hydrocarbon length of the surfactant and the content of ethyl methacrylate. These results were interpreted as a manifestation of the increasing contribution of attractive hydrophobic and electrostatic forces between negatively charged polymer chains and positively charged surfactant molecules. The increase of ethyl methacrylate in the copolymers lowers the CAC due to the larger hydrophobic character of the polymer backbone. The cloud point determination reveals that the lower critical solution temperatures (LCST) depend strongly on the copolymer composition and surfactant nature. The binding of surfactants molecules to the polymer chain screens the electrostatic repulsion between the carboxylic groups inducing a conformational transition and the dehydration of the polymer chain. 相似文献
969.
Vera L. B. Isaac Jemima D. D. Moraes Bruna G. Chiari Danila A. S. Guglielmi Letícia C. Cefali Nathália C. Rissi 《Journal of Dispersion Science and Technology》2013,34(4):532-538
This study aimed to characterize different emulsions obtained by the addition of four thickening agents, using rheological measurements, beyond analyzing the emulsions by polarized light microscopy looking for liquid crystals on them. The addition of these four thickening agents did not modify the base emulsion rheology, only an improvement in the sensory of the formulation was verified. The polarized light microscopy showed the formation of liquid crystalline structures in all the formulations, thus, the thickening agents did not influence in this parameter too. However, the emulsions could be considered appropriated for cosmetic purposes, probably being highly physically stable. 相似文献
970.
Alexander V. Shevtsov Vladimir V. Kuznetsov Alexander A. Kislukhin Vera Yu. Petukhova Yu. A. Strelenko Nina N. Makhova Konstantin A. Lyssenko 《Journal of heterocyclic chemistry》2006,43(4):881-888