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101.
Biswajit GhoshRupanjali Bhattacharjee Pushan BanerjeeSubrata Das 《Applied Surface Science》2011,257(8):3670-3676
In this work, 650 nm polycrystalline SnS thin films were grown by thermal evaporation of high purity tin sulfide powder at 250 °C substrate temperature, followed by post deposition annealing at 200 °C and 300 °C for 2, 4 and 6 h, and at 400 °C for 2 and 4 h in argon ambient. The XRD pattern of the as-deposited and annealed SnS films led to the conclusion that the as-deposited films were polycrystalline in nature with preferentially oriented along (1 1 1) direction. The direct bandgap of all the films was found to be observed between 1.33 and 1.53 eV. Except for annealing at 400 °C all the films were nearly stoichiometric in nature, suggesting lower rate of desulfurization at that ambient. However, higher annealing temperature has resulted in the segregation of tin phase. All the films showed good absorption in the visible range. The as-deposited and annealed films showed p-type conductivity. Hall measurement revealed the carrier concentration and mobility ranging from 1015 to 1016 cm−3 and 0.8 to 31.6 cm2 V−1 s−1 respectively. The photoconductivity measurements of all the SnS films were carried out by recording the lowering of resistance of the respective films with time under illumination. 相似文献
102.
Shashaank Gupta Shuvrajyoti Bhattacharjee Dhananjai Pandey Vipul Bansal Suresh K. Bhargava Ju Lin Peng Ashish Garg 《Applied Physics A: Materials Science & Processing》2011,104(1):395-400
We report an unusual behavior observed in (BiFeO3)1−x
–(PbTiO3)
x
(BF–xPT) thin films prepared using a multilayer chemical solution deposition method. Films of different compositions were grown
by depositing several bilayers of BF and PT precursors of varying BF and PT layer thicknesses followed by heat treatment in
air. X-ray diffraction showed that samples of all compositions show mixing of two compounds resulting in a single-phase mixture,
also confirmed by transmission electron microscopy. In contrast to bulk compositions, samples show a monoclinic (MA-type) structure suggesting disappearance of the morphotropic phase boundary (MPB) at x=0.30 as observed in the bulk. This is accompanied by the lack of any enhancement of the remanent polarization at the MPB,
as shown by the ferroelectric measurements. Magnetic measurements showed an increase in the magnetization of the samples with
increasing BF content. Significant magnetization in the samples indicates melting of spin spirals in the BF–xPT films, arising from a random distribution of iron atoms. Absence of Fe2+ ions was corroborated by X-ray photoelectron spectroscopy measurements. The results illustrate that thin film processing
methodology significantly changes the structural evolution, in contrast to predictions from the equilibrium phase diagram,
besides modifying the functional characteristics of the BP-xPT system dramatically. 相似文献
103.
Let N ≥ 5 and \({{\mathcal{D}}^{2,2} (\mathbb{R}^N)}\) denote the closure of \({C_0^\infty (\mathbb{R}^N)}\) in the norm \({\|u\|_{{\mathcal{D}}^{2,2} (\mathbb{R}^N)}^2 := \int\nolimits_{\mathbb{R}^N} |\Delta u|^2.}\) Let \({K \in C^2 (\mathbb{R}^N).}\) We consider the following problem for ? ≥ 0: $$(P_\varepsilon) \left\{\begin{array}{llll}{\rm Find} \, u \in {\mathcal{D}}^{2, 2} (\mathbb{R}^N) \, \, {\rm solving} :\\ \left.\begin{array}{lll}\Delta^2 u = (1+ \varepsilon K (x)) u^{\frac{N+4}{N-4}}\\ u > 0 \end{array}\right\}{\rm in} \, \mathbb{R}^N.\end{array}\right.$$ We show an exact multiplicity result for (P ? ) for all small ? > 0. 相似文献
104.
The degradation of neurotransmitters is a hallmark feature of Alzheimer''s disease (AD). Copper bound Aβ peptides, invoked to be involved in the pathology of AD, are found to catalyze the oxidation of serotonin (5-HT) by H2O2. A combination of EPR and resonance Raman spectroscopy reveals the formation of a Cu(ii)–OOH species and a dimeric, EPR silent, Cu2O2 bis-μ-oxo species under the reaction conditions. The Cu(ii)–OOH species, which can be selectively formed in the presence of excess H2O2, is the reactive intermediate responsible for 5-HT oxidation. H2O2 produced by the reaction of O2 with reduced Cu(i)–Aβ species can also oxidize 5-HT. Both these pathways are physiologically relevant and may be involved in the observed decay of neurotransmitters as observed in AD patients.The mononuclear copper hydroperoxo species (Cu(ii)–OOH) of Cu–Aβ is the active oxidant responsible for serotonin oxidation by Cu–Aβ in the presence of physiologically relevant oxidants like O2 and H2O2, which can potentially cause oxidative degradation of neurotransmitters, a marker of Alzheimer''s disease. 相似文献
105.
Papiya Bhattacharjee 《Topology and its Applications》2011,158(14):1802-1814
In studying the minimal prime spectra of commutative rings with identity we have been able to identify several interesting types of extensions of rings. In particular, we determine what kind of ring extensions will result in a homeomorphisms of the hull-kernel and inverse topologies on the minimal prime spectra. We relate these types of extensions to other known types of extensions. 相似文献
106.
Abhishek Roy Michael A. Hickner Xiang Yu Yanxiang Li Thomas E. Glass James E. McGrath 《Journal of Polymer Science.Polymer Physics》2006,44(16):2226-2239
One of the integral parts of the fuel cell is the proton exchange membrane. Our research group has been engaged in the past few years in the synthesis of several sulfonated poly(arylene ether) random copolymers. The copolymers were varied in both the bisphenol structure as well as in the functional groups in the backbone such as sulfone and ketones. To compare the effect of sequence length, multiblock copolymers based on poly(arylene ether sulfone)s were synthesized. This paper aims to describe our investigation of the effect of chemical composition, morphology, and ion exchange capacity (IEC) on the transport properties of proton conducting membranes. The key properties examined were proton conductivity, methanol permeability, and water self diffusion coefficient in the membranes. It was observed that under fully hydrated conditions, proton conductivity for both random and block copolymers was a function of IEC and water uptake. However, under partially hydrated conditions, the block copolymers showed improved proton conductivity over the random copolymers. The proton conductivity for the block copolymer series was found to increase with increasing block lengths under partially hydrated conditions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2226–2239, 2006 相似文献
107.
John A. Mikroyannidis Ioakim K. Spiliopoulos Theodoros S. Kasimis Abhishek P. Kulkarni Samson A. Jenekhe 《Journal of polymer science. Part A, Polymer chemistry》2004,42(9):2112-2123
Two new poly(p‐phenylene vinylene) derivatives OX1‐PPV and OX2‐PPV bearing two 1,3,4‐oxadiazole rings per repeat unit and a fully conjugated backbone with solubilizing dodecyloxy side groups were synthesized and investigated. The amorphous conjugated polymers had glass‐transition temperature values of 60–75 °C and emitted intense blue or greenish‐blue light in solution with photoluminescence (PL) emission maxima at 379–492 nm and PL quantum yields of 0.41–0.52. In the solid state they emitted yellowish‐green light with PL emission maxima at 533–555 nm. Cyclic voltammetry showed that both conjugated polymers had reversible reduction and irreversible oxidation, making them n‐type materials. The electron affinity of OX2‐PPV was estimated as 2.85 eV whereas that of OX1‐PPV was 2.75 eV. Yellow electroluminescence (EL) was achieved from single‐layer light‐emitting diodes of OX2‐PPV with an EL emission maximum at 555 nm and a brightness of 70 cd/m2. Polymer OX2‐PPV, which was functionalized with 2,6‐bis(1,3,4‐oxadiazole‐2‐yl)pyridine, demonstrated sensitivity to various metal ions as a fluorescence‐mode chemosensor. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2112–2123, 2004 相似文献
108.
Hang Wang Anand S. Badami Abhishek Roy James E. McGrath 《Journal of polymer science. Part A, Polymer chemistry》2007,45(2):284-294
Nanophase‐separated, hydrophilic–hydrophobic multiblock copolymers are promising proton‐exchange‐membrane materials because of their ability to form various morphological structures that enhance transport. A series of poly(2,5‐benzophenone)‐activated, telechelic aryl fluoride oligomers with different block molecular weights were successfully synthesized by the Ni(0)‐catalyzed coupling of 2,5‐dichlorobenzophenone and the end‐capping agent 4‐chloro‐4′‐fluorobenzophenone. These telechelic oligomers (hydrophobic) were then copolymerized with phenoxide‐terminated, disulfonated poly(arylene ether sulfone)s (hydrophilic) by nucleophilic, aromatic substitution to form hydrophilic–hydrophobic multiblock copolymers. High‐molecular‐weight multiblock copolymers with number‐average block lengths ranging from 3000 to 10,000 g/mol were successfully synthesized. Two separate glass‐transition temperatures were observed via differential scanning calorimetry in the transparent multiblock copolymer films when each block length was longer than 6000 g/mol. Tapping‐mode atomic force microscopy also showed clear nanophase separation between the hydrophilic and hydrophobic domains and the influence of the block length as it increased from 6000 to 10,000 g/mol. Transparent and creasable films were solvent‐cast and exhibited moderate proton conductivity and low water uptake. These copolymers are promising candidates for high‐temperature proton‐exchange membranes in fuel cells, which will be reported separately in part II of this series. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 284–294, 2007 相似文献
109.
G. R. Sudhakaran R. L. Bhattacharjee J. C. Sarker L. H. Johnston 《Journal of Infrared, Millimeter and Terahertz Waves》1986,7(12):1903-1911
A submillimeter laser Stark spectrum has been observed for fully deuterated Methyl Chloride (CD3Cl) with the 337 μm line of the HCN laser up to Stark fields of about 54000 V/cm. The spectra were taken for both Parallel and Perpendicular Polarizations and the multiplet transitions were identified as JK=42K←41K in the ground vibrational state. Three families with K=12, 13 and 14 have been identified and their zero field frequencies have been given with improved accuracy over those calculated from available molecular constants. 相似文献
110.