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331.
Cooperative and FRET‐Assisted Brightness Enhancement in Oligo(phenylene ethynylene): Quantum Dot Organic–Inorganic Nanohybrids 下载免费PDF全文
Dr. Arun Gopi Manikantan Sajitha Reethu Haridas Listo Varghese Dr. Karuvath Yoosaf 《化学:亚洲杂志》2018,13(11):1492-1499
Herein, we combine the ideas of concerted emission from fluorophore ensembles and its further amplification through FRET in an organic–inorganic hybrid approach. Spherical and highly fluorescent organic nanoparticles (FONPs, Φf=0.38), prepared by the self‐assembly of oligo(phenylene ethynylene) (OPE) molecules, were selected as a potential donor material. This organic core was then decorated with a shell of fluorescent CdSe/ZnS core–shell quantum dots (QDs; <d>?5.5 nm, Φf=0.27) with the aid of a bifunctional ligand, mercaptopropionic acid. Its high extinction coefficient (?≈4.1×105 m ?1 cm?1) and good spectral match with the emission of the FONPs (J(λ)≈4.08×1016 m ?1 cm?1 nm4) made them a better acceptor candidate to constitute an efficient FRET pair (ΦFRET=0.8). As a result, the QD fluorescence intensity was enhanced by more than twofold. The fundamental calculations carried out indicated an improvement in all the FRET parameters as the number of QDs around the FONPs was increased. This, together with the localization of multiple QDs in a nanometric dimension (volume≈1.8×106 nm3), gave highly bright reddish luminescent hybrid particles as visualized under a fluorescence microscope. 相似文献
332.
B. Milton Boaz J. Mary Linet Babu Varghese M. Palanichamy S. Jerome Das 《Journal of Crystal Growth》2005,280(3-4):448-454
Single crystals of potassium p-nitrophenolate dihydrate (NPK·2H2O) have been grown successfully using the isothermal solvent evaporation technique. It is a new semiorganic nonlinear optical crystal, possessing a deff of about 1.5 times that of lithium niobate and in which the K+ ions are bonded to the nitro group instead of bonding with the phenolic O−. Large single crystals of dimension upto 20×6×4 mm3 are harvested within a period of 60 days. The grown crystals are subjected to single crystal X-ray, FTIR and DRS-UV visible spectral, thermal and microhardness analyses. Single crystal X-ray analysis confirms the molecular formula and the structure of the crystal. FTIR spectral studies verify the functional groups present in the crystal. The DRS-UV visible spectrum proved the optical transparency of the crystal in the entire visible and near infrared region. Thermal studies reveal that the crystals are stable upto 180 °C. Microhardness measurements on the cleaved plane (1 1 0) explain the strength and slip direction in the crystal. The SHG efficiency of the crystal is examined by performing the Kurtz powder test using Nd:YAG laser. 相似文献
333.
Panicker CY Varghese HT John A Philip D Nogueira HI 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(8):1545-1551
IR and Raman spectra of melamine diborate have been recorded and analysed. Band assignments are given based on the vibrations of melamine and boric acid molecules. Three sets of frequencies observed for the N-H stretching mode region is ascribed to different types of hydrogen bonds in the amino groups of the triazine ring. Due to the lower symmetry of the melamine and boric acid molecules in the crystal, activation of inactive modes and lifting of the degeneracy of certain vibrational modes are observed. Lower symmetry of the melamine molecule in the crystal has resulted in the decrease of intensity of the Raman active melamine band around 1490 cm(-1). All the internal modes of boric acid molecule were identified. All the ring breathing modes of melamine molecule show frequency shift towards the high wavenumber side. In other words, hydrogen bonding affects the ring breathing modes of melamine. 相似文献
334.
A. C. Varghese C. S. Menon 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(4):465-468
The various electrical properties and the nature of conduction mechanisms of
magnesium phthalocyanine thin film devices with top and bottom aluminium
electrodes have been investigated. The conduction mechanism was identified
as injection limited essentially due to the electrode material. Even with
the same electrode materials, the device showed asymmetric conduction
behavior in the forward and reverse bias. In general the conduction was
interpreted as a Schottky emission with barrier height Φs=1.07 eV for
the forward bias and Φs=1.09 eV in the reverse bias. The effect of
oxygen on the conductivity of the device has also been investigated. In the
oxygen doped samples the conductivity is decreased which may be attributed
to an interfacial layer between the electrode and the organic layer. Further
in the oxygen doped sample while a Schottky emission is observed at lower
voltages Poole-Frenkel conductivity was identified in the higher voltage
region. 相似文献
335.
The Compton profile of tantalum (Ta) has been measured using IGP type coaxial photon detector. The target atoms were excited
by means of 59.54 keV γ-rays from Am-241. The measurements were carried out on a high purity thin elemental foil. The data
were recoreded in a 4 K multichannel analyzer. These data duly corrected for various effects are presented and compared with
theoretical and measured values. Best agreement with experiment is found for the 5d36s2 electron configuration 相似文献
336.
meso-Tetra (2′- and 3′-thienyl)porphyrins and their Zn(II)-complexes were examined by steady-state fluorescence measurements. These
molecules exhibit significant bathochromic shift in their emission bands with decreased quantum yields relative to their correspondingmeso-tetraphenylporphyrin derivatives. The crystal structure of 5,10,15,20-tetrakis(3′-thienyl)porphinato zinc(II) shows planar and nonplanar stereochemical features of the macrocycle. One of the macrocycle
shows nearly planar while the other exhibited predominantly saddle-shaped geometry. The extent of displacement of the Β-pyrrole
carbons in the nonplanar (saddle) conformation is as high as ± 0·422 ?. 相似文献
337.
338.
Chemistry of N,S‐Heterocyclic Carbene and Metallaboratrane Complexes: A New η3‐BCC‐Borataallyl Complex 下载免费PDF全文
Dr. Dipak Kumar Roy Anangsha De Subhankar Panda Dr. Babu Varghese Prof. Sundargopal Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(39):13732-13738
A high‐yielding synthetic route for the preparation of group 9 metallaboratrane complexes [Cp*MBH(L)2], 1 and 2 ( 1 , M=Rh, 2 , M=Ir; L=C7H4NS2) has been developed using [{Cp*MCl2}2] as precursor. This method also permitted the synthesis of an Rh–N,S‐heterocyclic carbene complex, [(Cp*Rh)(L2)(1‐benzothiazol‐2‐ylidene)] ( 3 ; L=C7H4NS2) in good yield. The reaction of compound 3 with neutral borane reagents led to the isolation of a novel borataallyl complex [Cp*Rh(L)2B{CH2C(CO2Me)}] ( 4 ; L=C7H4NS2). Compound 4 features a rare η3‐interaction between rhodium and the B‐C‐C unit of a vinylborane moiety. Furthermore, with the objective of generating metallaboratranes of other early and late transition metals through a transmetallation approach, reactions of rhoda‐ and irida‐boratrane complexes with metal carbonyl compounds were carried out. Although the objective of isolating such complexes was not achieved, several interesting mixed‐metal complexes [{Cp*Rh}{Re(CO)3}(C7H4NS2)3] ( 5 ), [Cp*Rh{Fe2(CO)6}(μ‐CO)S] ( 6 ), and [Cp*RhBH(L)2W(CO)5] ( 7 ; L=C7H4NS2) have been isolated. All of the new compounds have been characterized in solution by mass spectrometry, IR spectroscopy, and 1H, 11B, and 13C NMR spectroscopies, and the structural types of 4 – 7 have been unequivocally established by crystallographic analysis. 相似文献
339.
Dipl.‐Chem. Philipp Ensslen Fabian Brandl Dr. Sabrina Sezi Dr. Reji Varghese Dr. Roger‐Jan Kutta Prof. Dr. Bernhard Dick Prof. Dr. Hans‐Achim Wagenknecht 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(26):9349-9354
The chromophores ethynyl pyrene as blue, ethynyl perylene as green and ethynyl Nile red as red emitter were conjugated to the 5‐position of 2′‐deoxyuridine via an acetylene bridge. Using phosphoramidite chemistry on solid phase labelled DNA duplexes were prepared that bear single chromophore modifications, and binary and ternary combinations of these chromophore modifications. The steady‐state and time‐resolved fluorescence spectra of all three chromophores were studied in these modified DNA duplexes. An energy‐transfer cascade occurs from ethynyl pyrene over ethynyl perylene to ethynyl Nile red and subsequently an electron‐transfer cascade in the opposite direction (from ethynyl Nile red to ethynyl perylene or ethynyl pyrene, but not from ethynyl perylene to ethynyl pyrene). The electron‐transfer processes finally provide charge separation. The efficiencies by these energy and electron‐transfer processes can be tuned by the distances between the chromophores and the sequences. Most importantly, excitation at any wavelength between 350 and 700 nm finally leads to charge separated states which make these DNA samples promising candidates for light‐harvesting systems. 相似文献
340.
Rongala Ramalakshmi Koushik Saha Dipak Kumar Roy Dr. Babu Varghese Prof. Ashwini K. Phukan Prof. Sundargopal Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(48):17191-17195
A series of agostic σ‐borane/borate complexes have been synthesized and structurally characterized from simple borane adducts. A room‐temperature reaction of [Cp*Mo(CO)3Me], 1 with Li[BH3(EPh)] (Cp*=pentamethylcyclopentadienyl, E=S, Se, Te) yielded hydroborate complexes [Cp*Mo(CO)2(μ‐H)BH2EPh] in good yields. With 2‐mercapto‐benzothiazole, an N,S‐carbene‐anchored σ‐borate complex [Cp*Mo(CO)2BH3(1‐benzothiazol‐2‐ylidene)] ( 5 ) was isolated. Further, a transmetalation of the B‐agostic ruthenium complex [Cp*Ru(μ‐H)BHL2] ( 6 , L=C7H4NS2) with [Mn2(CO)10] affords a new B‐agostic complex, [Mn(CO)3(μ‐H)BHL2] ( 7 ) with the same structural motif in which the central metal is replaced by an isolobal and isoelectronic [Mn(CO)3] unit. Natural‐bond‐orbital analyses of 5–7 indicate significant delocalization of the electron density from the filled σB?H orbital to the vacant metal orbital. 相似文献