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排序方式: 共有115条查询结果,搜索用时 15 毫秒
41.
Umut Aygül Dr. Heiko Peisert Johannes Frisch Dr. Antje Vollmer Prof. Norbert Koch Prof. Thomas Chassé 《Chemphyschem》2011,12(12):2345-2351
We report on the electronic structure of poly[2,6‐(4,4‐bis‐ (2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b;3,4‐b′]dithiophene)‐alt‐4,7(2,1,3‐benzothiadiazole)] (PCPDTBT), a promising low‐band‐gap donor material for efficient bulk heterojunction organic solar cells. Electronic properties of interfaces formed between PCPDTBT and prototypical electrodes [Au, indium‐tin‐oxide and poly(ethylene‐dioxythiophene): poly(styrenesulfonate)], obtained from X‐ray photoemission spectroscopy and ultraviolet photoemission spectroscopy, are evaluated. The formation of interface dipoles is observed, and their consequences for device performance are discussed. For the system PCPDTBT/Au chemical interactions occur, which may affect in particular the charge extraction at the corresponding interface. 相似文献
42.
In this research, we have studied magnetized strange quark matter (SQM) solutions for Friedmann-Robertson-Walker (FRW) universe in f(R, T) gravity. To obtain exact solutions of modified field equations we have used and models given by Harko et al. (Harko et al. in Phys. Rev. D 84:024020, 2011) and model (here f3 is an arbitrary function) with cosmological constant Λ. For t → ∞ we obtain dark energy situation with small constant values of cosmological constant in three different f(R, T) gravitation models. In our solutions magnetic field does not observe also we have transformed our solutions from FRW universe to Static Einstein Universe (SEU) and we get f(R, T) gravity results for SEU universe. Finally we discussed our physical solutions. 相似文献
43.
Melis?Ozge?Alas Rukan?GencEmail authorView authors OrcID profile 《Journal of nanoparticle research》2017,19(5):185
In this study, comparative evaluation of fluorescent carbon nanodots (C-Dots) prepared using carob molasses was reported by screening various biocompatible macromolecules as passivating agent (PA). Incorporation of PAs with different molecular weight, polarity, and chemical structure was examined, and compared with the polyethylene glycol (PEG, Mn = 10 kN) passivated and pristine C-Dots. Not only the fluorescence properties but also many other features including size, crystal structure, colloidal conductivity, resistance to photobleaching, quantum yield, and UV-modulated surface interaction of them with the reactive oxygen species (ROS) as well as ROS production were investigated. Photoluminescence (PL) capacity of C-Dots was found to be associated with the number of surface alkyl groups and polymeric hydrogen bounding present on the C-Dot surface (increased number is associated with decreased PL) while surface conductivity of C-Dots in water was proportional to the PL intensity. More importantly, C-Dots with relatively poorer fluorescent were investigated in various organic solvents (hexane, methanol, acetone, ethanol, dimethylformamide (DMF), and DMSO). As happens with the fluorescent dyes, their PL intensities were significantly enhanced (even for pristine C-Dots) depending on the solvent characteristics. All of the C-Dots synthesized were further evaluated by means of UV-induced generation of ROS and inhibition of ROS by using H2O2 as model. In contrary to other carbonaceous nanomaterials, they did not show any ROS generation, on the contrary, they showed ROS scavenging activity that can be modulated by UV-irradiation (λ exc = 365 nm). PEG and alginate passivated C-Dots inhibited H2O2 activity at LC50 values below 10 mg/mL. 相似文献
44.
Gallium Selenide (GaSe) thin films were grown by the electrochemical deposition (ECD) technique on Indium tin oxide (ITO) and p-Si (100) substrates. The Electron paramagnetic resonance (EPR) spectrum of GaSe thin films’ growth on ITO was recorded at room temperature. According to EPR results, the g value of an EPR signal obtained for GaSe deposited on ITO is 2.0012?±?0.0005. In/GaSe/p-Si heterojunction was irradiated with high-energy (6?MeV) and low-dose (1.53?×?1010?e??cm?2) electrons. The ideality factor of the In/GaSe/p-Si device was calculated as 1.24 and barrier height was determined as 0.82?eV from I–V measurements before irradiation. Acceptor concentration, built-in potential and barrier height of the In/GaSe/p-Si device were also obtained as 0.72?×?1014?cm?3, 0.65?eV and 0.97?eV from C–V measurements, respectively. After irradiation, the ideality factor n and barrier height Φb values of the In/GaSe/p-Si device were calculated as 1.55 and 0.781?eV, respectively. Acceptor concentration, the built-in potential and barrier height values of the In/GaSe/p-Si device have also shown a decrease after 6?MeV electron irradiation. This change in heterojunction device parameters shows that current transport does not obey thermionic emission, and thus tunneling could be active due to the defects formed by irradiation at the In–GaSe interface. 相似文献
45.
Salvatore Cabiddu Enzo Cadoni Stefana Melis Gioanna Gelli Maria Grazia Cabiddu Claudia Fattuoni Stefania De Montis Sandra Ianelli 《Tetrahedron》2001,57(52):10365-10375
The reaction of benzoxathiole-3-oxide with LDA in THF or THF/hexane or THF/HMPA gave a carbanion which was reacted with methyl iodide, aromatic aldehydes or carbon dioxide. The conformational stability (-diastereoselectivity) of the carbanion and the asymmetric induction due to the prochiral electrophiles (β-diastereoselectivity) was studied. The temperature and the solvent effects on the - and β-diastereoselectivity are discussed. 相似文献
46.
Maria Grazia CabidduSalvatore Cabiddu Enzo CadoniStefania De Montis Claudia FattuoniStefana Melis 《Tetrahedron》2003,59(16):2893-2897
The metallation reaction of N-Boc-and N-Piv-(methylthio)anilines are here described. The results show that N-Boc derivatives are metallated only by superbases to give products substituted at the thiomethylic group. N-Piv derivatives show a different behaviour: ortho-derivative is metallated by both butyllithium and superbase at the thiomethylic carbon atom, while para-derivative is metallated in ortho to the N-Piv group by butyllithium and at the thiomethylic carbon atom by superbase. The meta-derivative is metallated only by superbase at the thiomethylic carbon atom. 相似文献
47.
Abstract— In 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) poisoned chloroplasts of algae and‘ higher plants the area over the fluorescence induction curve increases with biphasic first order kinetics (Melis and Homann, 1975). Two possibilities are considered to explain the biphasic nature of the area growth. The first is a sequential double reduction of the primary electron acceptor in system II while the second envisages a heterogeneity of its photochemical centers. The kinetic properties of the area growth after firing a single saturating flash proved to be incompatible with the predictions of the “sequential double reduction” model. This conclusion was corroborated by results obtained from a kinetic analysis of the area restoration process in the dark, and an analysis of the partially restored areas. Assuming an existence of a heterogeneous pool of photochemical centers, the growth of the area over the fluorescence curve could be further analyzed to yield two components, a fast a-component, and a relatively slow β-component. The kinetic characteristics of these components, and the effect of a short saturating flash on their respective size, led to the conclusion that one type of photochemical center had a faster recombination rate of the photochemically separated charges and was less efficient in trapping excitation energy. 相似文献
48.
Anastasios Melis Nechama S. Kosower Nancy A. Crawford Emilia Kirowa-Eisner Miriam Schwarz Edward M. Kosower 《Photochemistry and photobiology》1986,43(5):583-589
Abstract— Monobromobimane in chloroplasts lowers both the quantum yield of system II photochemistry and the yield of chlorophyll a fluorescence. Illumination of the chloroplasts in the presence of monohromobimane is an absolute prerequisite to the manifestation of this phenomenon, which proceeds via the Photosystem II intermediate, the semiquinone radical anion, QA -. The latter transfers an electron to monobromobimane to yield an anion radical (mBBr· ), which may either lose bromide ion to yield a reactive radical (mB· ), or acquire a proton and undergo further reduction, eventually forming syn-(methyl, methyl) bimane. In turn, mB reacts with the protein of the light-harvesting complex, to form a product which acts as static excitation energy quencher in the chlorophyll pigment bed of photosystem 11. Polarographic reduction of monobromobimane shows an adsorption wave at O V and two reduction waves. Prolonged reduction in water at -0.5 V yields syn-(methyl, methyl) bimane (which is further reduced at more negative potentials) and bromide ion. Thus, both electrochemical and chloroplast-induced reduction produce syn-(methyl, methyl) bimane. Monobromobimane may then serve as a Photosystem II activated probe in elucidating the conformation of intrinsic thylakoid membrane polypeptides. 相似文献
49.
The determination of palladium and platinum in alumina-supported bimetallic Pt-Re, Pd and Pt catalysts at the 0.03 and 0.3% (m/m) levels, respectively, and of rhodium and platinum in platinum sieve catalysts at the 0.04% (m/m) level and in the 4.75–19.75% (m/m) range, respectively, is described. The platinum group metals in fresh or spent catalysts are determined chromatographically using densitometry by forming theirN,N-diethyl-N-benzoylthiourea complexes. The precision of the method, %RSD, is 0.4–3.5, 2.2–6.7, and 4.2–6.0 for Pt, Pd and Rh, respectively. The accuracy was tested using alumina-based and active carbon platinum and palladium standards. The results were also compared with those obtained by FAAS. There was at most 8% difference between the results obtained with these methods, except for one active carbon based Pd standard. 相似文献
50.
The behaviour of 1-(2-bromoethyl) 4-nitrobenzene (1), N,N,N-triethyl-2-(4-nitrophenyl)ethanaminium bromide (2) and N,N-diethyl-N-[2-(4-nitrophenyl)ethyl]octan-1-aminium bromide (3) in the OH−-induced elimination reactions with formation of 1-nitro-4-vinylbenzene in mixtures of DMSO/H2O or CH3CN/H2O has been investigated. With all three substrates an increase in dipolar aprotic solvent content implies a limited increase
of the second-order rate constant k
OH up to ≅605, and then an exponential increase is observed. The variation of activation parameters ΔH
# and dGS
#, measured in DMSO/H2O mixtures, is parallel for 1 and 2. This similar behaviour of 1 and 2 with respect to variation in solvent composition is evidence that it is not possible to use this technique of solvent effect
for the mechanistic diagnosis of elimination reactions. 相似文献