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101.
Mantosh K. Sinha Ofer Reany Dr. Galit Parvari Ananta Karmakar Dr. Ehud Keinan Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(30):9056-9067
4‐Aminobipyridine derivatives form strong inclusion complexes with cucurbit[6]uril, exhibiting remarkably large enhancements in fluorescence intensity and quantum yields. The remarkable complexation‐induced pKa shift (ΔpKa=3.3) highlights the strong charge–dipole interaction upon binding. The reversible binding phenomenon can be used for the design of switchable beacons that can be incorporated into cascades of binding networks. This concept is demonstrated herein by three different applications: 1) a switchable fluorescent beacon for chemical sensing of transition metals and other ligands; 2) direct measurement of binding constants between cucurbit[6]uril and various nonfluorescent guest molecules; and 3) quantitative monitoring of biocatalytic reactions and determination of their kinetic parameters. The latter application is illustrated by the hydrolysis of an amide catalyzed by penicillin G acylase and by the elimination reaction of a β‐cabamoyloxy ketone catalyzed by aldolase antibody 38C2. 相似文献
102.
M. B. Das S. Karmakar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(3):339-341
Lifetimes of eight levels belonging to the 5p46d configuration of
singly ionized xenon have been measured by high frequency deflection
technique with a delayed coincidence single photon counting arrangement. The
results have been compared with other experimental and theoretical values.
The lifetimes of the 6d 2F3/2 and 6d 4F3/2 levels have
been measured for the first time. 相似文献
103.
We argue that all the necessary ingredients for successful inflation are present in the flat directions of the Minimally Supersymmetric Standard Model. We show that out of many gauge-invariant combinations of squarks, sleptons, and Higgs bosons, there are two directions, LLe and udd, which are promising candidates for the inflaton. The model predicts more than 10(3) e-foldings, with an inflationary scale of H(inf) approximately O(1-10) GeV, provides a tilted spectrum with an amplitude of delta(H) approximately 10(-5) and a negligible tensor perturbation. The temperature of the thermalized plasma could be as low as T(rh) approximately O(1-10) TeV. Parts of the inflaton potential can be determined independently of cosmology by future particle physics experiments. 相似文献
104.
Bikash Karmakar 《Tetrahedron letters》2010,51(20):2748-2750
An efficient, mild and environmentally friendly method has been developed for the Strecker reaction to synthesize α-aminonitriles in the presence of K2PdCl4 as a catalyst. The three-component one-pot condensation of an aldehyde, amine and trimethylsilyl cyanide proceeded smoothly in water to afford the corresponding product in high yield with short reaction times. 相似文献
105.
A single-step melt-quench in situ thermochemical reduction technique has been used to synthesize a new series of Au° nanoparticles embedded antimony glass–ceramic (K2O–B2O3–Sb2O3–ZnO) dichroic nanocomposites. X-ray and selected area electron diffractions manifest growth of Au° nanoparticles along (2 0 0) planes. The particle sizes obtained from X-ray diffraction patterns are found to vary in the range 4–21 nm. Dichroic behavior is attributed to the elliptical shape gold nanoparticles having aspect ratio 1.2, as observed from the transmission electron microscopy (TEM) images. The Au° nanoparticles exhibit surface plasmon resonance band (SPR) around 600 nm, which experiences red-shifts with increasing Au concentration. These nanocomposites when co-doped with Sm2O3 and excited at 949 nm, exhibit 2-fold intensification of 636 nm red emission transition (4G5/2 → 6H9/2) due to SPR induced local field enhancement of Au° nanoparticles and are promising materials for display applications. 相似文献
106.
Manirul Islam Sanchita Mondal Mobarak Manir Anupam Singha Roy Paromita Mondal Dildar Hossain 《中国化学》2010,28(10):1810-1820
Polymer anchored Cu(II) Schiff base complexes have been prepared and characterized by using scanning electron microscope (SEM), elemental analysis, atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), spectrometric methods like diffuse reflectance spectra of solid (DRS) and fourier transform infrared spectroscopy (FTIR). These catalysts show excellent catalytic activity in the O‐arylation reaction of aryl halides with phenol in acetonitrile using Cs2CO3 at 70°C under an open air condition to give diaryl ethers in high yields. The effects of various parameters such as solvent, catalyst from different copper salt and base on the reaction system have been studied. The reaction is applicable to a wide variety of substituted aryl halides and phenols with different steric and electronic properties. These catalysts are recovered by simple filtration and the reusability experiments show that these catalysts can be used five times without much loss in the catalytic activity. 相似文献
107.
The role of nuclear degrees of freedom in modifying the electron or exciton transfer rates between molecules is investigated. In addition to the usual Franck-Condon overlap factors which arise from the overlaps of initial and final vibrational states, we discuss a dependence of the transfer integral upon nuclear motions, a dependence which has been often cited, but nearly always ignored, in the usual dynamical theories of transfer processes. We show, within a Bom-Oppenheimer treatment, that the transfer integral dependence upon librational, rotational and vibrational modes can profoundly change both the rate itself and its functional dependences (upon temperature, upon orientation, etc.). Using a simple cosine form for the dependence of the transfer integral upon the modifying nuclear mode and a simple displaced-oscillator transformation, we obtain a closed-form solution for the transfer rate, which includes a new overlap factor arising from the dependence of the transfer integral upon nuclear coordinates. Some general remarks about the role of this dependence are made, and applications to particular transfer systems are briefly discussed. 相似文献
108.
Saha Manas Kumar Sen Sutapa Gupta Tarakranjan Mitra Samiran Kundu Parimal Karmakar Aswini Kumar 《Transition Metal Chemistry》1998,23(5):635-640
The mononuclear fragments [Cu(HDopn)(OH)2]+ and [Cu(HPopn)(OH)2]+, [H2Dopn=3,3-(trimethylene- dinitrilo)-dibutan-2–one dioximate and H2Popn, = 3, 3-(phenylenedinitrilo)-dibutan-2–one dioximate] were used to prepare four binuclear complexes [(OH2)Cu (Dopn)Cu(ditn)]2+, [(OH2)Cu(Dopn)Ni(ditn)(H2O)]2+ (ditn=diethylenetriamine) and [(OH2)Cu(Popn)Cu(L) (H2O)]2+ (L=2,2-bipyridine or 1,10–phenanthroline). Two trinuclear complexes, [{Cu(Popn)(OH2)}2M (H2O)n]2+ (when M=CuII, n=1; M=ZnII, n= 2), have been synthesised and characterised by elemental analyses, f.a.b. mass, i.r., electronic, e.s.r. spectroscopy and variable temperature (5–300K) magnetic susceptibility measurements. A strong antiferromagnetic interaction (J=–545cm–1 to –700cm–1) has been found for the binuclear copper(II) complexes. The X-band e.s.r. spectra of these complexes at 300K and for trinuclear complexes at 120K indicate square-pyramidal geometry for the copper centres with a (dx2–y2)1 ground state. The binuclear complex of copper(II)–nickel(II) centres with antiferromagnetic interaction (J=–107 cm–1) is described, and moderately strong zero-field splitting within the quartet state leads to Kramers doublet, as indicated by X-band e.s.r. spectra of this complex. The trinuclear copper(II) complex with an antiferromagnetic interaction (J= –350cm–1) is also described. The heterometallic trinuclear copper(II)–zinc(II)–copper(II) system shows a very weak interaction (J–1cm–1). 相似文献
109.
Modeling of separation of aqueous solutions of FeCl3 and AlCl3 by zeolite-clay composite membranes using a space-charge model 总被引:1,自引:0,他引:1
In our earlier work, we reported the separation of FeCl3 from its aqueous solution and AlCl3 from its aqueous solution by analcime zeolite (Z1) membrane and its nitrated (Z2 membrane) and aminated (Z3 membrane) forms. Experimental data on the separation of aqueous solutions of FeCl3 and AlCl3 by zeolite-clay composite membranes has been simulated using the two-dimensional space-charge model. The computational requirement of the model has been considerably reduced by first obtaining a series solution of the nonlinear Poisson-Boltzmann equation. The effective pore radius of the membrane is taken as the one that gives the best fit to the experimental data, while the pore length is determined from the SEM photograph of the cross-sectional view of the membrane. The effective pore radii of the Z1, Z2, and Z3 membranes for FeCl3 solute are found to be 8.0, 7.0, and 5.0 nm, respectively, while for AlCl3 they are 4.5, 2.5, and 2.5 nm, respectively. These values are much less than the average of the pore size range values determined independently in an earlier work using the bubble point method and indicate partial blocking of the pores by these salts. The effective pore radius is larger for FeCl3 as compared to AlCl3 and decreases on modification. The intrinsic rejection is also found to decrease on modification. The permeate flux calculated from the model matches very well with the experimental values. 相似文献