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801.
B. AguirreR.S. Vemuri D. ZubiaM.H. Engelhard V. ShutthananadanK. Kamala Bharathi C.V. Ramana 《Applied Surface Science》2011,257(6):2197-2202
Hafnium oxide (HfO2) thin films have been made by radio-frequency (rf) magnetron-sputtering onto Si(1 0 0) substrates under varying growth temperature (Ts). HfO2 ceramic target has been employed for sputtering while varying the Ts from room temperature to 500 °C during deposition. The effect of Ts on the growth and microstructure of deposited HfO2 films has been studied using grazing incidence X-ray diffraction (GIXRD), and high-resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive X-ray spectrometry (EDS). The results indicate that the effect of Ts is significant on the growth, surface and interface structure, morphology and chemical composition of the HfO2 films. Structural characterization indicates that the HfO2 films grown at Ts < 200 °C are amorphous while films grown at Ts > 200 °C are nanocrystalline. An amorphous-to-crystalline transition occurs at Ts = 200 °C. Nanocrystalline HfO2 films crystallized in a monoclinic structure with a (−1 1 1) orientation. An interface layer (IL) formation occurs due to reaction at the HfO2-Si interface for HfO2 films deposited at Ts > 200 °C. The thickness of IL increases with increasing Ts. EDS at the HfO2-Si cross-section indicate that the IL is a (Hf, Si)-O compound. The electrical characterization using capacitance-voltage measurements indicate that the dielectric constant decreases from 25 to 16 with increasing Ts. The current-voltage characteristics indicate that the leakage current increases significantly with increasing Ts due to increased ILs. 相似文献
802.
Kondapalli Venkata Gowri Chandra Sekhar Thripuraribhatla Venkata Naga Varuna Tara Sasank Hunsur Nagendra Nagesh Narva Suresh Kalaga Mahalakshmi Naidu Amaroju Suresh 《中国化学快报》2013,24(12):1045-1048
A simple and efficient method has been developed for conversion of chalcone oximes to 3,5-diaryl isoxazoles in excellent yields under solvent-free conditions. The synthesized compounds were characterized by infrared spectroscopy, ^1H NMR, ^13C NMR and HRMS. 相似文献
803.
Venkata Ramana Gedela Vadali Venkata Satya Siva Srikanth 《Applied Physics A: Materials Science & Processing》2014,115(1):189-197
Granular type polyaniline (PANi), PANi nanofibers (NFs), and PANi nanotubes (NTs) expedient as working electrode materials for supercapacitors are synthesized. The synthesis procedure used in this work facilitates not only the synthesis of solid powders of the PANi nanostructures, but also thin films constituted by the same PANi nanostructures in the same experiment. PANi NFs are found to exhibit faster electrode kinetics and better capacitance when compared to PANi NTs and granular PANi. Specific capacitance and energy storage per unit mass of PANi NFs are 239.47 Fg?1 (at 0.5 Ag?1) and 43.2 Wh?kg?1, respectively. Electrical conductivity of PANi NFs is also better when compared to the other two nanostructures. Properties of the three PANi nanostructures are explicated in correlation with crystallinity, intrinsic oxidation state, doping degree, BET surface area, and ordered mesoporosity pertaining to the nanostructures. 相似文献
804.
Y. Lakshman Kumar R. Venkata Nadh P. S. Radhakrishnamurti 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2014,88(5):774-778
In the oxidation of D-sorbitol and D-mannitol by potassium periodate in alkaline media, substrate inhibition was observed with both substrates, i.e., a decrease in the rate of the reaction was observed with an increase in the concentration of substrate. The substrate inhibition was attributed to the formation of stable complex between the substrate and periodate. The reactions were found to be first order in case of periodate and a positive fractional order with hydroxide ions. Arrhenius parameters were calculated for the oxidation of sorbitol and mannitol by potassium periodate in alkali media. 相似文献
805.
Herein we document the first total synthesis of mangiferaelactone and thus establish its absolute configuration. The central nonenolide ring was constructed using ring closing metathesis and Yamaguchi esterification. The key alcohol fragment was synthesized by the Bernet–Vasella fragmentation of C-ribofuranoside. 相似文献
806.
Krishnamoorthy Hegde Veeranki Venkata Dasu 《Applied biochemistry and biotechnology》2014,174(2):803-819
A comparative analysis of the structural and functional aspects along with equilibrium unfolding of two homologous cutinases, Cut1 and Cut2, from Thermobifida fusca was carried out. The CD and fluorescence profile at different pH in the range of 6 to 9 showed no structural variations for both cutinases, indicating their stability to a wide range of pH. Tryptophan quenching studies suggested that all the four Trp residues in the protein are in inaccessible hydrophobic pockets. Further, near-UV CD analysis of tertiary structure revealed a dissimilar distribution of aromatic amino acid on the surface of these two enzymes. Denaturation profiles obtained in aqueous solutions of the guanidine hydrochloride revealed different tolerance levels for unfolding of the two cutinases, with Cut2 showing higher resistivity to unfolding in comparison to Cut1. Both cutinases retained all the structural parameters even in the presence of 8 M urea, indicating the protein to be highly resistant to urea-induced unfolding. Structural study by homology modeling revealed a high resemblance of secondary structure between the two cutinases; however, their tertiary structure, hydrophobicity, and surface electrostatic properties were very different, which contributed to the difference in the structural stability of these two cutinases. 相似文献
807.
Flexible and Rigid Amine‐Functionalized Microporous Frameworks Based on Different Secondary Building Units: Supramolecular Isomerism,Selective CO2 Capture,and Catalysis
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Ritesh Haldar Dr. Sandeep K. Reddy Venkata M. Suresh Dr. Sudip Mohapatra Prof. Sundaram Balasubramanian Prof. Tapas Kumar Maji 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(15):4347-4356
We report the synthesis, structural characterization, and porous properties of two isomeric supramolecular complexes of ([Cd(NH2?bdc)(bphz)0.5]?DMF?H2O}n (NH2?bdc=2‐aminobenzenedicarboxylic acid, bphz=1,2‐bis(4‐pyridylmethylene)hydrazine) composed of a mixed‐ligand system. The first isomer, with a paddle‐wheel‐type Cd2(COO)4 secondary building unit (SBU), is flexible in nature, whereas the other isomer has a rigid framework based on a μ‐oxo‐bridged Cd2(μ‐OCO)2 SBU. Both frameworks are two‐fold interpenetrated and the pore surface is decorated with pendant ?NH2 and ?N?N? functional groups. Both the frameworks are nonporous to N2, revealed by the type II adsorption profiles. However, at 195 K, the first isomer shows an unusual double‐step hysteretic CO2 adsorption profile, whereas the second isomer shows a typical type I CO2 profile. Moreover, at 195 K, both frameworks show excellent selectivity for CO2 among other gases (N2, O2, H2, and Ar), which has been correlated to the specific interaction of CO2 with the ?NH2 and ?N?N? functionalized pore surface. DFT calculations for the oxo‐bridged isomer unveiled that the ?NH2 group is the primary binding site for CO2. The high heat of CO2 adsorption (ΔHads=37.7 kJ mol?1) in the oxo‐bridged isomer is realized by NH2???CO2/aromatic π???CO2 and cooperative CO2???CO2 interactions. Further, postsynthetic modification of the ?NH2 group into ?NHCOCH3 in the second isomer leads to a reduced CO2 uptake with lower binding energy, which establishes the critical role of the ?NH2 group for CO2 capture. The presence of basic ?NH2 sites in the oxo‐bridged isomer was further exploited for efficient catalytic activity in a Knoevenagel condensation reaction. 相似文献
808.
B. V. V. S. Pavan Kumar Dr. K. Venkata Rao Prof. S. Sampath Dr. Subi J. George Muthusamy Eswaramoorthy 《Angewandte Chemie (International ed. in English)》2014,53(48):13073-13077
Several covalent strategies towards surface charge‐reversal in nanochannels have been reported with the purpose of manipulating ion transport. However, covalent routes lack dynamism, modularity and post‐synthetic flexibility, and hence restrict their applicability in different environments. Here, we introduce a facile non‐covalent approach towards charge‐reversal in nanochannels (<10 nm) using strong charge‐transfer interactions between dicationic viologen (acceptor) and trianionic pyranine (donor). The polarity of ion transport was switched from anion selective to ambipolar to cation selective by controlling the extent of viologen bound to the pyranine. We could also regulate the ion transport with respect to pH by selecting a donor with pH‐responsive functional groups. The modularity of this approach further allows facile integration of various functional groups capable of responding to stimuli such as light and temperature to modulate the transport of ions as well as molecules. 相似文献
809.
Venkata Suresh Vajrala Emmanuel Suraniti Patrick Garrigue Bertrand Goudeau Michel Rigoulet Anne Devin Neso Sojic Stéphane Arbault 《Analytical and bioanalytical chemistry》2014,406(4):931-941
Microsystems based on microwell arrays have been widely used for studies on single living cells. In this work, we focused on the subcellular level in order to monitor biological responses directly on individual organelles. Consequently, we developed microwell arrays for the entrapment and fluorescence microscopy of single isolated organelles, mitochondria herein. Highly dense arrays of 3-μm mean diameter wells were obtained by wet chemical etching of optical fiber bundles. Favorable conditions for the stable entrapment of individual mitochondria within a majority of microwells were found. Owing to NADH auto-fluorescence, the metabolic status of each mitochondrion was analyzed at resting state (Stage 1), then following the addition of a respiratory substrate (Stage 2), ethanol herein, and of a respiratory inhibitor (Stage 3), antimycin A. Mean levels of mitochondrial NADH were increased by 29 % and 35 % under Stages 2 and 3, respectively. We showed that mitochondrial ability to generate higher levels of NADH (i.e., its metabolic performance) is not correlated either to the initial energetic state or to the respective size of each mitochondrion. This study demonstrates that microwell arrays allow metabolic studies on populations of isolated mitochondria with a single organelle resolution. Figure
Microwell arrays, build up from optical fiber bundles, were used for the entrapment and monitoring by fluorescence microscopy of populations of single mitochondria. Mitochondrial NADH was quantified under several metabolic states to study individual mitochondria responses simultaneously with whole population behaviors. 相似文献
810.
A concise approach for the total synthesis of aculeatin D and 6-epi-aculeatin D employing differentially protected anti, anti-1,3,5-triol alkyne prepared from alpha-D-glucoheptonic-gamma-lactone derivative is documented. Phenol protecting group manipulation for selective O-debenzylation during the hydrogenation of the diyne intermediate and one-pot phenolic oxidation with concomitant spiroketalization highlight the accomplished total synthesis. 相似文献