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51.
52.
Prof. Dr. So Won Youn Tae Yun Ko Young Ho Jang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(23):6736-6740
A Pd-catalyzed intermolecular oxidative annulation between N-Ts-anilines and styrenes was developed. This method offers a straightforward and robust approach to a wide range of 3-arylindoles using readily available starting materials with good functional-group tolerance and high regioselectivity and efficiency. Further elaboration of the products obtained from this process provided access to highly functionalized and structurally diverse indoles, for example, 3-(indol-3-yl)carbazoles, 1,9-dihydropyrrolo-[2,3-b]carbazoles, and 3′-aryl-3,5′-biindoles. 相似文献
53.
Heat and Mass Transfer in MHD Micropolar Flow Over a Vertical Moving Porous Plate in a Porous Medium
Youn J. Kim 《Transport in Porous Media》2004,56(1):17-37
An analysis is presented for the problem of free convection with mass transfer flow for a micropolar fluid via a porous medium bounded by a semi-infinite vertical porous plate in the presence of a transverse magnetic field. The plate moves with constant velocity in the longitudinal direction, and the free stream velocity follows an exponentially small perturbation law. A uniform magnetic field acts perpendicularly to the porous surface in which absorbs the micropolar fluid with a suction velocity varying with time. Numerical results of velocity distribution of micropolar fluids are compared with the corresponding flow problems for a Newtonian fluid. Also, the results of the skin-friction coefficient, the couple stress coefficient, the rate of the heat and mass transfers at the wall are prepared with various values of fluid properties and flow conditions. 相似文献
54.
The cross-linking reaction of a TiO(2)-polymer composite (TPC) dielectric with poly(4-vinyl phenol) (PVP), a TiO(2) precursor, and poly(melamine-co-formaldehyde) is demonstrated: We suggest that the dense chemical structure of TPC is caused by the alkoxyl group of the PVP cross-linker, poly(melamine-co-formaldehyde) methylated/butylated, reacted with the hydroxyl group of the PVP and the ligands of the TiO(2) precursor. 相似文献
55.
The reaction between ZnCl2 and N,N-bis[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]-1-phenylethylamine (bdmppea) affords [(bdmppea)ZnCl2], whose structure has been determined by X-ray crystallography. The [(bdmppea)ZnEt2] complex in situ prepared by the reaction between [bdmppea] and ZnEt2 exhibited high activity toward the polymerization reaction of rac-lactide at room temperature. However, its activity decreased sharply with decreasing temperature. Stereospecificity of this catalyst characterized by heterotacticity (Pr) was determined by homonuclear decoupled NMR spectroscopy, which value was ∼0.58. 相似文献
56.
Recent progress on the mesoporous nickel–alumina catalysts for hydrogen production by steam reforming of liquefied natural gas (LNG) was reported in this review. A number of mesoporous nickel–alumina composite catalysts were prepared by a single-step surfactant-templating method using cationic, anionic, and non-ionic surfactant as structure-directing agents for use in hydrogen production by steam reforming of LNG. For comparison, nickel catalysts supported on mesoporous aluminas were also prepared by an impregnation method. The effect of preparation method and surfactant identity on physicochemical properties and catalytic activities of mesoporous nickel–alumina catalysts in the steam reforming of LNG was investigated. Regardless of preparation method and surfactant identity, nickel oxide species were finely dispersed on the surface of mesoporous nickel–alumina catalysts through the formation of surface nickel aluminate phase. However, nickel dispersion and nickel surface area of mesoporous nickel–alumina catalysts were strongly affected by the preparation method and surfactant identity. It was found that nickel surface area of mesoporous nickel–alumina catalyst served as one of the important factors determining the catalytic performance in hydrogen production by steam reforming of LNG. Among the catalysts tested, a mesoporous nickel–alumina composite catalyst prepared by a single-step non-ionic surfactant-templating method exhibited the best catalytic performance due to its highest nickel surface area. 相似文献
57.
Su‐Kyung Lee Kyong‐Soon Shin Dr. Dong‐Youn Noh Prof. Dr. Olivier Jeannin Dr. Frédéric Barrière Dr. Jean‐François Bergamini Dr. Marc Fourmigué Dr. 《化学:亚洲杂志》2010,5(1):169-176
The redox‐active and chelating diphosphine, 3,4‐dimethyl‐3′,4′‐bis(diphenylphosphino)‐tetrathiafulvalene, denoted as P2 , is engaged in a series of platinum complexes, [(P2)Pt(dithiolene)], with different dithiolate ligands, such as 1,2‐benzenedithiolate (bdt), 1,3‐dithiole‐2‐thione‐4,5‐dithiolate (dmit), and 5,6‐dihydro‐1,4‐dithiin‐2,3‐dithiolate (dddt). The complexes are structurally characterized by X‐ray diffraction, together with a model compound derived from bis(diphenylphosphino)ethane, namely, [(dppe)Pt(dddt)] . Four successive reversible electron‐transfer processes are found for the [(P2)Pt(dddt)] complex, associated with the two covalently linked but electronically uncoupled electrophores, that is, the TTF core and the platinum dithiolene moiety. The assignments of the different redox processes to either one or the other electrophore is made thanks to the electrochemical properties of the model compound [(dppe)Pt(dddt)] lacking the TTF redox core, and with the help of theoretical calculations (DFT) to understand the nature and energy of the frontier orbitals of the [(P2)Pt(dithiolene)] complexes in their different oxidation states. The first oxidation of the highly electron‐rich [(P2)Pt(dddt)] complex can be unambiguously assigned to the redox process affecting the Pt(dddt) moiety rather than the TTF core, a rare example in the coordination chemistry of tetrathiafulvalenes acting as ligands. 相似文献
58.
Biochemical solutions have a wide range of hydrophilicity (contact angle and surface tension) and viscosity. A critical challenge is that microfluidic systems typically need expensive or complex pumps to control the various parallel biochemical streams. In this study, without using any pumps, we present a simple scheme that controls the ratio of the volumetric flow rate (VFR) of the parallel streams that have highly different hydrophilicity and viscosity. We accomplish this process by using capillarity to drive and merge two streams, and by regulating relative flow resistance to control the VFR ratio. Our results will significantly simplify the control of the VFR ratio for the various biochemical solutions that are used in microfluidic applications. 相似文献
59.
In this paper, high-luminance yellow-emitting Y3Al5O12:Ce3+ phosphor (YAG:Ce) microparticles were prepared in a solid flame using a 1.425Y2O3+2.5Al2O3+0.15CeO2+k(KClO3+urea)+mNH4F precursor mixture (here k is the number of moles of the KClO3+urea red-ox mixture, and m is the number of moles of NH4F). The self-sustaining combustion process for the entire reaction sample was provided by the heat generated from the KClO3+urea mixture. Parametric studies demonstrated that the maximum temperature in the combustion wave varied from 885 to 1200 °C for k=2.0-3.0 mole and m=0-1.5 mole. X-ray analysis results showed that the product obtained in the solid flame consisted of Y3Al5O12:Ce3+ and KCl phases. Therefore, after dissolving potassium chloride in distillated water, pure-phase YAG:Ce phosphor powder was obtained. The as-prepared YAG:Ce phosphor particles had diameters of 10-25 μm and good dispersity and exhibited luminescence properties comparable to those of YAG:Ce phosphor powders prepared by conventional high-temperature processing. 相似文献
60.
J.H. Yu J.H. Kim D.S. Park T.S. Kim T.S. Jeong C.J. Youn K.J. Hong 《Journal of Crystal Growth》2010,312(10):1683-1686
Wide band-gap BeZnO layers were grown on Al2O3 (0 0 0 1) substrate using radio-frequency magnetron co-sputtering. The rate of BexZn1−xO crystallized as a hexagonal structure was x=0.2. From the X-ray photoelectron spectroscopy measurement, the O–Zn bonds relating the crystal structure and the Be–O bonds related to the deviation of the stoichiometry in the BeZnO layer were caught at 530.4 and 531.7 eV in the O 1s spectrum, respectively. Thus, the observance on the Be 1s peak of 113.2 eV associated with the bonding Be–O indicates that the sputtered Be atoms are substituted for the host-lattice site in ZnO. This Be–O bonding shows a relatively low intense and broadening spectrum caused by large fluctuation of Be content in the BeZnO layer. From the photoluminescence and transmittance measurement, the free exciton and the neutral donor-bound exciton (D0, X) emissions were observed at 3.7692 and 3.7313 eV, respectively, and an average transmittance rate over 95% was achieved in a wide ultraviolet (UV)–visible region. Also, the binding energy for the (D0, X) emission was extracted to be 37.9 meV. Through the wide band-gap material BeZnO, we may open some possibilities for fabricating a ZnO-based UV light-emitting diode to be utilized as a barrier layer comprised of the ZnO/BeZnO quantum well structure and/or an UV light emitting material itself. 相似文献