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171.
Michał Mosiałek Magdalena Dudek Aneta Michna Maciej Tatko Aneta Kędra Małgorzata Zimowska 《Journal of Solid State Electrochemistry》2014,18(11):3011-3021
Silver-Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) cathodes were prepared in two ways. In the first method, Ag-BSCF composite powder was prepared in ethanol solution, where Ag nanoparticles serving as a component in the preparation of Ag-BSCF composite cathodes had been previously obtained via one-step synthesis in absolute ethanol using a neutral polymer (polyvinylpyrrolidone). To the best of our knowledge, this is the first study to use a Ag sol obtained by the above method for preparation of Ag-BSCF composite powder. Then, a paste containing this powder was screen-printed on a Sm0.2Ce0.8O1.9 electrolyte and sintered at 1,000 °C. In the second technique, an aqueous solution of AgNO3 was added to a previously sintered BSCF cathode, which was then sintered again at 800 °C. The oxygen reduction reaction at the quasi-point BSCF cathode on the Sm0.2Ce0.8O1.9 electrolyte was tested by electrochemical impedance spectroscopy at different oxygen concentrations in three electrode setup. The continuous decrease of polarization resistance was observed under polarization ?0.5 V at 600 °C. The comparative studies of both obtained composite Ag-BSCF materials were performed in hydrogen-oxygen IT-SOFC involving samaria-doped ceria as an electrolyte and Ni-Gd0.2Ce0.8O1.9 anode. In both cases, the addition of silver to the cathode caused an increase in current and power density compared with an IT-SOFC built with the same components but involving a monophase BSFC cathode material. 相似文献
172.
Krzysztof Cybulski Ludwika Tomaszewska-Hetman Waldemar Rymowicz Magdalena Rakicka Anita Rywińska 《Chemical Papers》2018,72(12):3077-3083
With the problems related to chemical methods of pyruvic acid (PA) synthesis, a fast-growing interest has been observed in research aiming at reducing the production cost of PA by applying biotechnological methods. This study aimed to investigate the potential applicability of Yarrowia lipolytica Wratislavia 1.31 yeast strain for valorisation of pure and crude glycerol through the production of industrially desired PA. Conditions required for the effective PA biosynthesis, i.e., pH value, thiamine concentration, agitation, and substrate concentration, were examined in batch and fed-batch cultivation modes. The efficient production of PA occurred under the limitation of thiamine (1 µg L?1) and was stimulated by moderate pH (4.5) and agitation (800 rev min?1) of the culture. Under optimal conditions, Y. lipolytica Wratislavia 1.31 was able to produce 85.2 g L?1 of PA with volumetric productivity of 0.90 g L?1 h?1. The yield of PA biosynthesis reached a high level of 1.03 g g?1. Obtained results confirmed the aptitude of Y. lipolytica yeast to produce high amounts of PA from simple glycerol-containing media. Presented process was very promising and might be considered as an attractive alternative for currently used chemical methods of PA synthesis. 相似文献
173.
Hanna Barchanska Piotr Markowski Magdalena Strzebin 《International journal of environmental analytical chemistry》2018,98(6):493-505
A simple, fast and sensitive analytical method was developed for the quantification of herbicide mesotrione (MES) and its degradation products: 4-(methylsulfonyl)-2-nitrobenzoic acid (MNBA) and 2-amino-4-(methylsulfonyl) benzoic acid (AMBA) using differential pulse voltammetry (DPV). Voltammetric measurements were performed using glassy carbon electrode (GCE). Potential range, pH of the electrolyte and the scan rate were optimised to achieve the lowest detection limits of analytes. The optimal conditions were obtained in a Britton–Robinson (BR) buffer at pH 4.0 for MNBA and at pH 6.0 for MES and AMBA, with the scan rate 0.08 V/s. The potential V for (1) nitro and carbonyl groups of MES, (2) nitro group of MNBA and (3) amino group of AMBA, obtained under optimised conditions, was plotted as a function of a peak current (I). The I(V) dependencies were measured for the following concentration ranges: 0.5–5.0 µM for the nitro group of MES and MNBA, 0.75–5.0 µM and 0.50–8.5 µM for the carbonyl groups of MES, and 0.25–8.5 µM for amino group of AMBA; whereas, the limit of detection was in range 0.07–0.23 µM (20–80 µg/L). The proposed method is the first one that allows the determination of both MES and its degradation products. The practical applicability of these newly developed voltammetric methods was verified by direct determination of MES and its degradation products in model samples of drinking and surface water. 相似文献
174.
Ligor M Jarmalaviciene R Szumski M Maruska A Buszewski B 《Journal of separation science》2008,31(14):2707-2713
The aim of the investigations was to develop analytical methods for the determination of selected volatile and non-volatile organic compounds numbering among the final products of milk fermentation. The analyzed compounds were as follows: biacetyl and carboxylic acids (formic, acetic, citric, and lactic). The model yogurt was prepared under controlled conditions in our laboratory by addition of the selected bacteria (Lactobacillus bulgaricus and Streptococcus thermophilus) to the milk sample. The temperature, time, and stirring were controlled during the fermentation process. Factors considered in SPMPE-GC-FID method development included fiber exposure time, salt addition, temperature of extraction, and temperature of desorption. Various SPME fibers, for example with PDMS, CAR/PDMS, PA, and PDMS/DVB coatings, were tested to obtain the highest recovery of the investigated compounds extracted from yogurt samples. Based on these preliminary experiments, qualitative and quantitative analyses for the determination of biacetyl were performed by SPME-GC-FID. Moreover, a capillary zone electrophoresis method was developed for the determination of carboxylic acids in the yogurt samples. The buffer composition as well as deproteinization by acetonitrile were found to have a crucial effect on the analysis. 相似文献
175.
A number of copper salts, Cu(OOCCH(3))(2), Cu(ClO(4))(2), Cu(NO(3))(2), CuCl(2) and CuSO(4) have been tested for their ability to form binuclear copper-caffeine complexes. The electrospray ionization (ESI) mass spectra of methanol solution containing caffeine and CuCl(2) or CuSO(4) show signals of two copper atom containing ions, so the signals correspond to binuclear complexes: [2Caf + Cu(2)SO(4)](+), [2Caf + Cu(2)](+), [2Caf + Cu(2)Cl](+), [2Caf + Cu(2)Cl(2)](+) and [2Caf + Cu(2)Cl(3)](+). Sulfate and chloride anion are characterized by charge densities higher than those of the carboxylate, nitrate and perchlorate anion. Thus, due to the electrostatic forces, the binuclear complexes containing SO(4)(2-) or Cl(-) can survive the transfer from solution to the gas phase and then can successfully be observed on ESI mass spectra. The ion [2Caf + Cu(2)Cl(3)](+) is present in solution and could be detected when using methanol/chloroform as solvent. The ions [2Caf + Cu(2)](+), [2Caf + Cu(2)Cl](+) and [2Caf + Cu(2)Cl(2)](+) are formed from the [2Caf + Cu(2)Cl(3)](+) ion (by subsequent loss of Cl atoms) on transfer from the solution to the gas phase or in the gas phase. The ion [2Caf + Cu(2)](+) does not contain a bridging agent, thus it is reasonable to assume that it contains a Cu-Cu bond. 相似文献
176.
Lafolet F Chardon-Noblat S Duboc C Deronzier A Pruchnik FP Rak M 《Dalton transactions (Cambridge, England : 2003)》2008,(16):2149-2156
An original electrochemical synthesis of {[Rh4(mu-OOCCH3)4(phen)4]2+}n (1) molecular wire films from a solution of binuclear bridged Rh complexes [Rh2(mu-OOCCH3)2(phen)2(X)2](Y)2 (X = H2O, Y = BF4(-) (2a) and X = CH3CN, Y = BF4(-) (2b)) in MeCN electrolyte is reported. UV-vis spectroscopy and quartz crystal microbalance electrochemical coupled techniques have been used to demonstrate the electrosynthesis process. The resulting polymetallic compound has been characterized on the basis of its physicochemical properties, which have been compared with those of a chemically synthesized sample. Furthermore, according to EPR, 1H NMR and electrochemical behaviour, the mechanism of the oxidation of this polymetallic wire, containing mixed valent rhodium centers and alternatively acetate bridged Rh-Rh bonds, has been investigated in detail. 相似文献
177.
Gaspard S Forster M Huber C Zafiu C Trettenhahn G Kautek W Castillejo M 《Physical chemistry chemical physics : PCCP》2008,10(40):6174-6181
The large intensities available with femtosecond (fs) laser pulses allow permanent structural modifications in transparent materials with high spatial resolution. Irradiation of self-standing transparent biopolymer films, such as collagen, pure and curcumin doped gelatine employing a 60-fs high-power 11 MHz Ti-Sapphire oscillator laser system linked to an optical microscope led to modifications and ablation. Swelling modifications consisting in the foaming of the irradiated area and formation of a single layer of bubbles arranged around the narrow ablation crater were investigated by optical, scanning force (SFM) and scanning electron (SEM) microscopy. These modifications occur at fluences below the respective ablation thresholds, i.e. ablation processes take place on modified swelled phases. The results are discussed in terms of local temperature increase, generation of thermoelastic stress, physico-chemical effects, and in terms of an incubation model, i.e. the accumulation of these phenomena upon successive pulse irradiation. 相似文献
178.
New process, instantaneous controlled pressure drop (DIC) was applied on Cananga odorata dry flowers with the aim to isolate essential oil. DIC is based on high temperature, short time heating followed by an abrupt pressure drop into a vacuum. A part of volatile compounds is carried away from flowers in the form of vapor (DIC direct oil) that evolves adiabatically during the pressure drop (proper isolation process) and the other part remains in the DIC-treated flowers (DIC residual oil). In the present paper, the effect of DIC cycle number (1-9) and heating time (4.3-15.7 min) on the availability of oil compounds was investigated at three levels of steam pressure (0.28, 0.4 and 0.6 MPa). The availability was defined as the amount of a compound in direct or residual oil divided by the amount of this compound in the reference oil extracted from non-treated flowers by chloroform during 2h. The total availability and yield of volatiles in the direct oil increased with pressure and cycle number. At a higher pressure, the effect of heating time was insignificant. The amount of oxygenated monoterpenes and other light oxygenated compounds (i.e. predominantly exogenous compounds) in the residual flowers was lower than in the direct oil and this amount decreased with cycle number. On the other hand, the availability of oxygenated sesquiterpenes and other heavy oxygenated compounds (i.e. predominantly endogenous compounds) in residual flowers exhibited a maximum for about five cycles and their quantity at this point was three times as much as in the direct oil. The total availability of each compound at 0.6 MPa was higher than one. The rapid DIC process (0.6 MPa, 8 cycles, 6 min) gave better results than steam distillation (16 h) concerning direct oil yield (2.8%dm versus 2.5%dm) and content of oxygenated compounds (72.5% versus 61.7%). 相似文献
179.
Agnieszka Wolnicka-Glubisz Magdalena Olchawa Mariusz Duda Pawel Pabisz Anna Wisniewska-Becker 《Photochemistry and photobiology》2023,99(1):57-67
Curcumin is a plant-derived yellow-orange compound widely used as a spice, dye and food additive. It is also believed to have therapeutic effects against different disorders. On the other hand, there are data showing its phototoxicity against bacteria, fungi and various mammalian cells. Since the mechanism of its phototoxic action is not fully understood, we investigated here the phototoxic potential of curcumin in liposomal model membranes and in HaCaT cells. First, detection of singlet oxygen (1O2) luminescence proved that curcumin generates 1O2 upon blue light irradiation in organic solvent and in liposomes. Then, HPLC-EC(Hg) measurements revealed that liposomal and cellular cholesterol is oxidized by 1O2 photogenerated by curcumin. Enrichment of liposome membranes with curcumin significantly increased the oxygen photo-consumption rate compared to the control liposomes as determined by EPR oximetry. Cytotoxicity measurements, mitochondrial membrane potential analyses and protein hydroperoxides detection confirmed strong phototoxic effects of curcumin in irradiated HaCaT cells. These data show that since curcumin is advertised as a valuable dietary supplement, or a component of cosmetics for topical use, caution should be recommended especially when skin is exposed to light. 相似文献
180.
Orts Gil G Losik M Schlaad H Drechsler M Hellweg T 《Langmuir : the ACS journal of surfaces and colloids》2008,24(22):12823-12828
Poly(styrene) 388- block-poly( l-lysine) 138 could be dispersed in water with the aid of the nonionic surfactant C 12E 6. Light scattering and direct imaging techniques show that the copolymer/surfactant aggregates are polydisperse spherical micelles. The rather broad size distribution can be attributed to the glassy state of the polystyrene core of the micelles hampering equilibration. Nevertheless, the poly( l-lysine) block remains pH sensitive in these mixed aggregates and circular dichroism measurements show that poly( l-lysine) block adopts a random coil conformation at low pH and an beta-sheet conformation at pH > or = 11 without any change in the micellar shape. Samples prepared by evaporation of drops of the solutions on graphite wafers exhibit different wetting patterns depending on the polypeptide conformation as indicated by atomic force microscopy. 相似文献