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801.
Zomer B Collé L Jedyńska A Pasterkamp G Kooter I Bloemen H 《Analytical and bioanalytical chemistry》2011,401(9):2945-2954
Acridinium esters traditionally are triggered using basic hydrogen peroxide. By serendipity, we have found that acridinium
esters can also be triggered with emission of chemiluminescence by reductive triggering, e.g., by zinc metal or reduced forms
of ferric and cupric salts. Furthermore, organic reducing compounds like dithiothreitol, tricarboxyethylphosphine or glutathione
could be used in combination with organic oxidants like quinones or inorganic ferric or cupric salts. Mechanisms are proposed
which involve the intermediacy of superoxide. Two forms of reactive oxygen species (i.e., hydrogen peroxide and superoxide)
could be discriminated based on differences in kinetics. Some applications (improved detection of acridinium ester, use of
acridinium ester as redox probes) are discussed. 相似文献
802.
Kurach E Djurado D Rimarčik J Kornet A Wlostowski M Lukeš V Pécaut J Zagorska M Pron A 《Physical chemistry chemical physics : PCCP》2011,13(7):2690-2700
Two series of new soluble conjugated compounds containing tetrazine central ring have been synthesized. The three-ring compounds have been synthesized by the reaction of aryl cyanide (where aryl = thienyl, alkylthienyl, phenyl or pyridyl) with hydrazine followed by oxidation of the intermediate product with diethyl azodicarboxylate. The five-ring compounds have been prepared using two pathways: (i) reaction of 5-cyano-2,2'-bithiophene (or its alkyl derivative) with hydrazine; (ii) via Suzuki or Stille coupling of 3,6-bis(5-bromo-2-thienyl)-1,2,4,5-tetrazine with a stannyl or boronate derivative of alkylthiophene. UV-vis spectroscopic properties of the synthesized compounds are strongly dependent on the nature of the aryl group, the position of the solubilizing substituent and the length of the molecule, showing the highest bathochromic shift (λ(max) > 440 nm) for five-ring compounds with alkyl groups attached to C(α) carbon in the terminal thienyl ring. An excellent linear correlation has been found for spectroscopically determined and theoretically calculated (TD-B3LYP/6-31G*) excitation energies. With the exception of dipyridyl derivative, the calculated lowest unoccupied molecular orbital (LUMO) level of the investigated molecules changes within a narrow range (from -2.63 to -2.41 eV), in line with the electrochemical data, which show a reversible reduction process with the redox potential varying from -1.23 V to -1.33 V (vs. Fc/Fc(+)). The electrochemically determined positions of the LUMO levels are consistently lower by 0.9 to 1.2 eV with respect to the calculated ones. All molecules readily crystallize. Single crystal studies of 3,6-bis(2,2'-bithien-5-yl)-1,2,4,5-tetrazine show that it crystallizes in a P2(1)/c space group whose structural arrangement is not very favorable to the charge carriers flow within the crystal. Powder diffraction studies of other derivatives have shown that their structural organization is sensitive to the position of the solubilizing substituent. In particular, the presence of alkyl groups attached to C(α) carbon in the terminal thienyl ring promotes the formation of a lamellar-type supramolecular organization. 相似文献
803.
Trąbska J Wesełucha-Birczyńska A Zięba-Palus J Runge MT 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(4):824-830
This work aimed at characterization of a black layer covering a Bronze Age (period VI) pot surface. To solve research problems plane polarized light microscopy (PLM), scanning microscopy with X-ray microanalyser (SEM/EDS), Raman and FTIR microspectroscopies were applied. Observation of the black layer under the PLM suggests that we deal with an opaque, isotropic layer, purposely put on leather-hard, burnished surface of a pot. No traces of organic substances that might have modified a pot surface before painting were detected. The black layer coats the pot with a continuous 0.2-0.4 μm thick layer. The black layer must have been applied while warm or hot. It is recognized that the black layer is a true painting layer. Spectroscopic analyses (Raman and FTIR) point that birch tar or a birch-pine tar had been applied. Carbon black should be definitely excluded. The analyzed organic substance is structurally ordered in various degrees, due to varying temperature influence. Some Raman spectra reveal, in second-order region of the spectrum (>2000 cm(-1)), the graphite presence. Scarce points reveal the presence of inorganic admixtures: clay minerals, feldspars and quartz. The next question is: Is it an organic paint or a carbon-based, "mixed" paint? Inorganic admixtures are only casual. Relatively high concentration of alumina is expected to have appeared due to aluminum mobility in acidic environment and this was provided by organic tar/pitch substances. Phosphorus (usually with calcium) mostly concentrates together with clay minerals. Thus, hypothesis on bone powder or ash addition to tar/pitch should be excluded. Some elements may originate not only from inorganic substances but also from wood ashes. 相似文献
804.
Aleksandra Kwiatkowska 《Israel Journal of Mathematics》2014,201(1):75-97
We show that the automorphism group, Aut(?), of a projective Fraïssé limit ?, whose natural quotient is the pseudo-arc, has a comeager conjugacy class. This generalizes an unpublished result of Izhar Oppenheim that Aut(?) (and consequently, the group of all homeomorphisms of the pseudo-arc) has a dense conjugacy class. We also present a simple proof of the result of Oppenheim. 相似文献
805.
Marek Bajda Aleksandra Guła Krzysztof Więckowski Barbara Malawska 《Electrophoresis》2013,34(20-21):3079-3085
The lipophilicity of a library of 30 derivatives of dihydrofuran‐2(3H)‐one (γ‐butyrolactone) was determined by MEKC. Calibration curve prepared for ten reference drugs enabled to calculate partition coefficient (log P) for novel compounds. The results of MEKC analysis were compared with lipophilicity coefficients determined by RP‐TLC (RM0) and computational (Mlog P, Clog P) methods. Good correlation was observed between the results obtained by both experimental methods: the MEKC parameters log k and relative lipophilicity RMO. The relationship between determined log P values and results of the computational prediction was weaker. Analysis of the relationship between lipophilicity and anticonvulsant activity showed statistically significant differences between mean values of log P coefficients for group of active (2.18) and inactive (1.51) compounds in the maximal electroshock test. 相似文献
806.
Kinga Łuczka Daniel Sibera Aleksandra Smorowska Barbara Grzmil 《Chemical Papers》2013,67(9):1210-1217
Microwave radiation was used in the acquisition of aluminium ammonium calcium phosphates. The substrates such as CaCO3, H3PO4, aqueous ammonia were reagent grade, whereas Al(OH)3 was prepared afresh. The influence of process parameters (pH 6 ± 2, molar ratios of Al3+: Ca2+: PO 4 3? in the substrates, respectively 0.31: 0.62: 1; 0.5: 0.5: 1; 0.72: 0.36: 1) on the phase composition and the product properties was determined. Statistical software STATISTICA 10 was used for planning and evaluation of the experiments. The process parameters making it possible to acquire the material with the anticipated physicochemical properties were determined based on statistical evaluation of the planned research by the plan fractional factorial design at three levels 3(k?p). The phase composition of the samples was studied using XRD analysis. The specific surface area was calculated using the BET method and the particle size was determined by LSM. Materials with a molar ratio of Al3+: Ca2+ and Al3+: NH 4 + in the range of 0.07–0.76 and 0.75–3.4, respectively, with an absorption oil number of 36–56 g per 100 g, S BET within 8.2–73 m2 g?1, and particle size in the range of 156–252 nm were obtained. 相似文献
807.
Agata Jargiło Iwona Grabowska Hanna Radecka Magdalena Sulima Ilona Marszałek Aleksandra Wysłouch‐Cieszyńska Wim Dehaen Jerzy Radecki 《Electroanalysis》2013,25(5):1185-1193
The new system which consists of the thiol derivative of dipyrromethene–Cu(II) complex created on the surface of a gold electrode was applied for the first time for oriented immobilization of selected His‐tagged domains of a receptor for advanced glycation endproducts (RAGE). Cyclic voltammetry (CV), Osteryoung square‐wave voltammetry (OSWV), electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM) were used for characterization of the redox active sensing layer. The biosensor proposed was applied for determination of Aβ16–23′ peptide. In its presence, a decrease of the maximum Cu(II) redox current was observed. These values correlated linearly with the Aβ16–23′ concentration in the range 0.001–1.000 µM. The presence of diluted human plasma has no influence on the sensor responses. 相似文献
808.
Aleksandra Skowrońska Ewa Krawczyk Janusz Burski 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-3):233-236
Abstract The selectivity of sulphur, selenium and oxygen removal from pseudohalogens: phosphorus disulphides 1 and 2, diselenides 3 and oxophosphoranesulphenyl chlorides 4 has been investigated. A mechanistic rationalization is proposed to account for sulphur (selenium)/oxygen extrusion variation as a function of substrates structure and reaction conditions. 相似文献
809.
Jacek Jenczyk Maria Dobies Monika Makrocka-Rydzyk Aleksandra Wypych Stefan Jurga 《European Polymer Journal》2013
The nuclear magnetic resonance (NMR) and dielectric spectroscopy (DS) methods were used to investigate the segmental and global dynamics in lamellar microphase separated poly(styrene-b-isoprene) (SI) diblock copolymer. For the first time, the susceptibility representation of the NMR relaxation data is applied to the analysis of the molecular dynamics in complex polymer systems like the diblock copolymer. This approach in combination with the frequency-temperature superposition (FTS) allows one to compare directly the NMR and DS data in an extended frequency range providing a unique comprehensive picture of various relaxation processes present in the system studied. The findings of these investigations include structural relaxations of the polyisoprene (PI) and the polystyrene (PS) blocks, a normal mode relaxation of the PI block, and an extra low frequency interfacial relaxation. Special attention has been devoted to influence of the copolymer morphology on the segmental and global dynamics in PI. 相似文献
810.
Phthalazinone and pyridopyridazinone derivatives 3, 5, and 9 were prepared via reaction ofappropriate lactams 2 and 8 with 2-bromoethylphthalimide, N-tosylaziridine, and N,O-ditosyl derivatives of N-methylethanolamine in a two-step process in the presence of MeONa/MeOH or NaH/dimethylformamide (DMF). Starting compounds 2 and 8 were obtained by reaction of hydrazine hydrate with isoindolinones 1 or azaisoindolinones 6. Selected N-(2-phthalimidoethyl)-phthalazinones were converted into corresponding 2-[2-(methylamino) ethyl]- derivatives in satisfactory yields by treatment with hydrazine. 相似文献