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971.
Dr. Mamta Bhandari Dr. Sandeep Rawat Dr. Mandeep Kaur Prof. Dr. Sanjay Singh 《European journal of organic chemistry》2023,26(36):e202300674
In this work, the catalytic activity of electronically unsaturated three coordinated aluminum hydride cations [ L AlH]+[HB(C6F5)3]− ( 1 ) and [ L AlH]+[B(C6F5)4]− ( 2 ) in hydrosilylation of imines has been disclosed ( L ={(2,6-iPr2C6H3N)P(Ph2)}2N). A variety of organo-silanes such as Et3SiH, MePhSiH2, PhSiH3, TMDSO, and PHMS are screened in this endeavour. The amines as products of catalysis were obtained in good to excellent yields after the hydrolysis of silylamine intermediates. Further, a series of controlled experiments systematically designed to investigate the underlying mechanistic pathway through multinuclear NMR analysis showed Lewis adduct formation between cationic aluminum centre and the imine nitrogen, which subsequently undergoes reaction with silane to afford the product. The hydrosilylation of imine performed with Et3SiH using catalyst 1 with a loading of 2 mol % at 60 °C occurs smoothly. Whereas 2 led to the product formation with Et3SiH only when used in stoichiometric quantity. Further, to investigate this unique behaviour of 1 NMR investigations were performed and revealed that the anion in 1 competes for hydride delivery and in-situ generates B(C6F5)3 that cooperatively reinforces the catalytic activity of 1 . 相似文献
972.
Dr. Supreet Kaur Dr. Golam Mohiuddin Dr. Neelam Yadav Prof. Santanu Kumar Pal 《Chemphyschem》2023,24(13):e202300133
In liquid crystalline systems, the presence of polar groups at lateral or terminal positions is fundamentally and technologically important. Bent-core nematics composed of polar molecules with short rigid cores usually exhibit highly disordered mesomorphism with some ordered clusters that favourably nucleate within. Herein, we have systematically designed and synthesized two new series of highly polar bent-core compounds comprised of two unsymmetrical wings, highly electronegative −CN and −NO2 groups at one end, and flexible alkyl chains at the other end. All the compounds showed a wide range of nematic phases composed of cybotactic clusters of smectic-type (Ncyb). The birefringent microscopic textures of the nematic phase were accompanied by dark regions. Further, the cybotactic clustering in the nematic phase was characterized via temperature-dependent XRD studies and dielectric spectroscopy. Besides, the birefringence measurements demonstrated the ordering of the molecules in the cybotactic clusters upon lowering the temperature. DFT calculations illustrated the favourable antiparallel arrangement of these polar bent-core molecules as it minimizes the large net dipole moment of the system. 相似文献
973.
Pratibha Nikhil Kumar Atul Kapoor Jaspreet Kaur Rajput Dinesh Singh Varnika 《Electroanalysis》2023,35(4):e202200283
Herein, an effective template assisted calcination procedure has been adopted to synthesize the Sulphur-doped graphitic carbon nitride (SXGCN). Furthermore, the SXGCN/GCE was then utilized for the electrochemical determination of 2,4-Dinitrophenol (2,4-DNP). It has been inferred that among the variously prepared SXGCN (x=0 %, 20 %, 40 %, 60 %, 80 %, and 100 %), S80GCN afforded the excellent electrochemical response for detection of 2,4-DNP. The synthesized SXGCN/GCE (x=80 %) demonstrates with a low detection limit of 0.9083 μM with linear range of 1–90 μM. Furthermore, the practical application of this sensor was successfully proved by detecting spiked 2,4-dinitrophenol in a real gym supplements sample. 相似文献
974.
Dr. Gaspard Hedouin Sudripet Sharma Karanjeet Kaur Ramesh Hiralal Choudhary Dr. Jacek B. Jasinski Dr. Fabrice Gallou Dr. Sachin Handa 《Angewandte Chemie (International ed. in English)》2023,62(39):e202312348
Herein, we developed the recyclable ligand-free iridium (Ir)-hydride based Ir0 nanoparticles (NPs) for the first regioselective partial hydrogenation of PV-substituted naphthalenes. Both the isolated and in situ generated NPs are catalytically active. A control nuclear magnetic resonance (NMR) study revealed the presence of metal-surface-bound hydrides, most likely formed from Ir0 species. A control NMR study confirmed that hexafluoroisopropanol as a solvent was accountable for substrate activation via hydrogen bonding. High-resolution transmission electron microscopy of the catalyst supports the formation of ultrasmall NPs, and X-ray photoelectron spectroscopy confirmed the dominance of Ir0 in the NPs. The catalytic activity of NPs is broad as showcased by highly regioselective aromatic ring reduction in various phosphine oxides or phosphonates. The study also showcased a novel pathway toward preparing bis(diphenylphosphino)-5,5′,6,6′,7,7′,8,8′-octahydro-1,1′-binaphthyl (H8-BINAP) and its derivatives without losing enantioselectivity during catalytic events. 相似文献
975.
Dr. Yijiao Qu Dr. Robert De Rose Dr. Chan-Jin Kim Dr. Jiajing Zhou Dr. Zhixing Lin Dr. Yi Ju Dr. Sukhvir Kaur Bhangu Dr. Christina Cortez-Jugo Dr. Francesca Cavalieri Prof. Frank Caruso 《Angewandte Chemie (International ed. in English)》2023,62(12):e202214935
DNA-based materials have attracted interest due to the tunable structure and encoded biological functionality of nucleic acids. A simple and general approach to synthesize DNA-based materials with fine control over morphology and bioactivity is important to expand their applications. Here, we report the synthesis of DNA-based particles via the supramolecular assembly of tannic acid (TA) and DNA. Uniform particles with different morphologies are obtained using a variety of DNA building blocks. The particles enable the co-delivery of cytosine-guanine adjuvant sequences and the antigen ovalbumin in model cells. Intramuscular injection of the particles in mice induces antigen-specific antibody production and T cell responses with no apparent toxicity. Protein expression in cells is shown using capsules assembled from TA and plasmid DNA. This work highlights the potential of TA as a universal material for directing the supramolecular assembly of DNA into gene and vaccine delivery platforms. 相似文献
976.
Kaur P Wu M Anzaldi L Waldeck DH Xue C Liu H 《Langmuir : the ACS journal of surfaces and colloids》2007,23(26):13203-13208
This study investigates the fluorescence quenching of a poly(p-phenyleneethynylene) (1) based polyelectrolyte by positively charged and neutral macromolecules. This work shows that the change in the fluorescence yield of 1 depends on a number of factors, including electrostatic, hydrophobic, and energy transfer interactions with the quencher and also changes in the solution conditions such as concentration and ionic strength. The fluorescence quenching is attributed to the formation of aggregates that form upon addition of different quenchers to a solution of 1 and/or the solution conditions. The extent of 1's aggregation is shown to depend on the type of interaction between the polymer and the quencher, the concentration of the polymer, and the ionic strength of the solution. 相似文献
977.
Tarlok S. Lobana Prof. Parminderjit Kaur Geeta Hundal Ray J. Butcher Alfonso Castineiras 《无机化学与普通化学杂志》2008,634(4):747-753
Reactions of pyrimidine‐2‐thione (HpymS) with PdII/PtIV salts in the presence of triphenyl phosphine and bis(diphenylphosphino)alkanes, Ph2P‐(CH2)m‐PPh2 (m = 1, 2) have yielded two types of complexes, viz. a) [M(η2‐N, S‐ pymS)(η1‐S‐ pymS)(PPh3)] (M = Pd, 1 ; Pt, 2 ), and (b) [M(η1‐S‐pymS)2(L‐L)] {L‐L, M = dppm (m = 1) Pd, 3 ; Pt, 4 ; dppe (m = 2), Pd, 5 ; Pt, 6 }. Complexes have been characterized by elemental analysis (C, H, N), NMR spectroscopy (1H, 13C, 31P), and single crystal X‐ray crystallography ( 1 , 2 , 4 , and 5 ). Complexes 1 and 2 have terminal η1‐S and chelating η2‐N, S‐modes of pymS−, while other Pd/Pt complexes have only terminal η1‐S modes. The solution state 31P NMR spectral data reveal dynamic equilibrium for the complexes 3 , 5 and 6 , whereas the complexes 1 , 2 and 4 are static in solution state. 相似文献
978.
Zoppellaro G Harbitz E Kaur R Ensign AA Bren KL Andersson KK 《Journal of the American Chemical Society》2008,130(46):15348-15360
Cytochromes of the c type with histidine-methionine (His-Met) heme axial ligation play important roles in electron-transfer reactions and in enzymes. In this work, two series of cytochrome c mutants derived from Pseudomonas aeruginosa (Pa c-551) and from the ammonia-oxidizing bacterium Nitrosomonas europaea (Ne c-552) were engineered and overexpressed. In these proteins, point mutations were induced in a key residue (Asn64) near the Met axial ligand; these mutations have a considerable impact both on heme ligand-field strength and on the Met orientation and dynamics (fluxionality), as judged by low-temperature electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectra. Ne c-552 has a ferric low-spin (S = 1/2) EPR signal characterized by large g anisotropy with g(max) resonance at 3.34; a similar large g(max) value EPR signal is found in the mitochondrial complex III cytochrome c1. In Ne c-552, deletion of Asn64 (NeN64Delta) changes the heme ligand field from more axial to rhombic (small g anisotropy and g(max) at 3.13) and furthermore hinders the Met fluxionality present in the wild-type protein. In Pa c-551 (g(max) at 3.20), replacement of Asn64 with valine (PaN64V) induces a decrease in the axial strain (g(max) at 3.05) and changes the Met configuration. Another set of mutants prepared by insertion (ins) and/or deletion (Delta) of a valine residue adjacent to Asn64, resulting in modifications in the length of the axial Met-donating loop (NeV65Delta, NeG50N/V65Delta, PaN50G/V65ins), did not result in appreciable alterations of the originally weak (Ne c-552) or very weak (Pa c-551) axial field but had an impact on Met orientation, fluxionality, and relaxation dynamics. Comparison of the electronic fingerprints in the overexpressed proteins and their mutants reveals a linear relationship between axial strain and average paramagnetic heme methyl shifts, irrespective of Met orientation or dynamics. Thus, for these His-Met axially coordinated Fe(III), the large g(max) value EPR signal does not represent a special case as is observed for bis-His axially coordinated Fe(III) with the two His planes perpendicular to each other. 相似文献
979.
Deoiled soya, an agricultural waste material, and bottom ash, a waste of power plants, have been successfully used for the removal and recovery of the hazardous water-soluble dye brilliant green from water. To remove the dye from water, batch adsorption studies have been carried out by observing the effects of pH, concentration, amounts of adsorbents, size of adsorbent particles, etc. Attempts have also been made to monitor the adsorption process through Langmuir, Freundlich, Tempkin, and D-R adsorption isotherm models. Relevant thermodynamic parameters have also been calculated from these models. The adsorption process has been found endothermic and feasible at all the temperatures. The kinetics of the adsorption was also recorded and indicates pseudo-second-order kinetics in both cases. Kinetic operations also reveal the involvement of a film diffusion mechanism for the deoiled soya adsorption at all the temperatures, while bottom ash undergoes through a particle diffusion mechanism at only 30 °C and at higher temperatures a film diffusion mechanism operates. Bulk removal of the dye has been carried out through column studies for both adsorbents. Attempts have also been made to recover the dye from exhausted columns by eluting sulfuric acid of pH 3. 相似文献
980.
A new, rapid and sensitive RP-HPLC method with UV spectrophotometric detection was developed and validated for the concomitant estimation of adenosine and related purines in rat brain tissue preparations. The HPLC system consisted of C-18 column with UV-photodiode-array detection ranging from 210 to 400 nm, facilitating the online confirmation of peak purity. The column temperature was maintained at 30 degrees C and the injection volume was 20 muL. Elution with an isocratic mobile phase consisting of water/methanol/acetonitrile (88:5:7 by volume) at a flow rate of 0.8 mL/min yielded sharp, utmost-resolved peaks of adenosine (Ade), inosine (Ino), hypoxanthine (Hypoxan) and adenine (Adn) within 10 min. The method was validated with respect to the linearity, accuracy, precision, sensitivity, selectivity and stability. The method was also employed to estimate the naturally occurring purines in discrete regions of rat brain. A new protocol developed for tissue preparation utilizing H(2)SO(4) and Tris buffer gave well-resolved peaks and high component recoveries (>96%) which eliminated the need of an internal standard. The results show that the method for the determination of Ade, Ino, Hypoxan and Adn by RP-HPLC described here has good linearity, accuracy, precision, sensitivity, selectivity and is simple and rapid to perform. 相似文献