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961.
Reaction of N,N'-bis(4-carboxysalicylidene)ethylenediamine (H(4)L) with iron(III) chloride and lanthanide nitrates resulted in the coordination polymers of composition {[Ln(2)(FeLCl)(2)(NO(3))(2)(DMF)(5)]·(DMF)(4)}(n) (Ln = Y, Eu, Gd, Tb, Dy). The polymers consist of iron-salen-based moieties having carboxylate linkers connected to rare earth atoms in a 1D chain structure. Thus, the iron-salen complex acts as a "metalloligand". Because of the twisting of the chains, porous structures are formed and possess large free void space. The magnetic studies of selected compounds exhibit weak intramolecular antiferromagnetic interactions of Ln-Ln. At 3, 30, and 80 K, the M?ssbauer spectra of the iron-dysprosium compound show a strongly asymmetric quadrupole doublet with isomer shift and quadrupole splitting values typical for Fe(III) ions in high spin state. In addition, an anomalous temperature dependence of both isomer shift and quadrupole splitting has been observed. 相似文献
962.
Fulcher LP Scherer RC Powell T 《The Journal of the Acoustical Society of America》2011,129(3):1548-1553
Pressure distributions for the uniform glottis were obtained with a static physical model (M5). Glottal diameters of d=0.005, 0.0075, 0.01, 0.02, 0.04, 0.08, 0.16, and 0.32 cm were used with a range of phonatory transglottal pressures. At each pressure and diameter, entrance loss and exit coefficients were determined. In general, both coefficients decreased in value as the transglottal pressure or the diameter increased. Entrance loss coefficients ranged from 0.69 to 17.6. Use of these coefficients with the measured flow rates in straightforward equations accurately reproduced the pressure distributions within the glottis and along the inferior vocal fold surface. 相似文献
963.
Peter R. Stevenson Bret E. Dunlap Paul S. Powell Brae V. Petersen Christopher J. Hatch Hung Chan Garret I. Still Michael T. Fulton Justin S. McKell David C. Collins 《Analytical and bioanalytical chemistry》2013,405(10):3085-3089
Single-dimension separations are routinely coupled in series to achieve two-dimensional separations, yet little has been done to simultaneously exploit multiple dimensions during separation. In this work, simultaneous chromatography and electrophoresis is introduced and evaluated for its potential to achieve two-dimensional separations. In simultaneous chromatography and electrophoresis, chromatography occurs via capillary action while an orthogonal electric field concurrently promotes electrophoresis in a second dimension. A novel apparatus with a dual solvent reservoir was designed to apply the concurrent electric field. Various compounds were used to characterize the apparatus and technique, i.e., vitamins, amino acids, and dyes. Improved separation is reported with equivalent analysis times in comparison to planar chromatography alone. The feasibility of simultaneously employing chromatography and electrophoresis in two dimensions is discussed. Figure
Separation of eight dyes is improved in comparison to (a) planar chromatography alone when employing (b) simultaneous chromatography and electrophoresis 相似文献
964.
Kayla J. Pyper David K. Kempe Jade Y. Jung Li-Hsing J. Loh Nigel Gwini Benjamin D. Lang Brittney S. Newton Jonathan M. Sims Vladimir N. Nesterov Gregory L. Powell 《Journal of Cluster Science》2013,24(3):619-634
Microwave heating allows for the high-yield, one-step synthesis of the known triosmium complexes Os3(μ-Br)2(CO)10 (1), Os3(μ-I)2(CO)10 (2), and Os3(μ-H)(μ-OR)(CO)10 with R = methyl (3), ethyl (4), isopropyl (5), n-butyl (6), and phenyl (7). In addition, the new clusters Os3(μ-H)(μ-OR)(CO)10 with R = n-propyl (8), sec-butyl (9), isobutyl (10), and tert-butyl (11) are synthesized in a microwave reactor. The preparation of these complexes is easily accomplished without the need to first prepare an activated derivative of Os3(CO)12, and without the need to exclude air from the reaction vessel. The syntheses of complexes 1 and 2 are carried out in less than 15 min by heating stoichiometric mixtures of Os3(CO)12 and the appropriate halogen in cyclohexane. Clusters 3–6 and 8–10 are prepared by the microwave irradiation of Os3(CO)12 in neat alcohols, while clusters 7 and 11 are prepared from mixtures of Os3(CO)12, alcohol and 1,2-dichlorobenzene. Structural characterization of clusters 2, 4, and 5 was carried out by X-ray crystallographic analysis. High resolution X-ray crystal structures of two other oxidative addition products, Os3(CO)12I2 (12) and Os3(μ-H)(μ-O2CC6H5)(CO)10 (13), are also presented. 相似文献
965.
Nuclear Magnetic Resonance Relaxivities: Investigations of Ultrahigh‐Spin Lanthanide Clusters from 10 MHz to 1.4 GHz 下载免费PDF全文
Julyana R. Machado Dr. Amer Baniodeh Prof. Dr. Annie K. Powell Prof. Dr. Burkhard Luy Dr. Steffen Krämer Dr. Gisela Guthausen 《Chemphyschem》2014,15(16):3608-3613
Paramagnetic relaxation enhancement is often explored in magnetic resonance imaging in terms of contrast agents and in biomolecular nuclear magnetic resonance (NMR) spectroscopy for structure determination. New ultrahigh‐spin clusters are investigated with respect to their NMR relaxation properties. As their molecular size and therefore motional correlation times as well as their electronic properties differ significantly from those of conventional contrast agents, questions about a comprehensive characterization arise. The relaxivity was studied by field‐dependent longitudinal and transverse NMR relaxometry of aqueous solutions containing FeIII10DyIII10 ultrahigh‐spin clusters (spin ground state 100/2). The high‐field limit was extended to 32.9 T by using a 24 MW resistive magnet and an ultrahigh‐frequency NMR setup. Interesting relaxation dispersions were observed; the relaxivities increase up to the highest available fields, which indicates a complex interplay of electronic and molecular correlation times. 相似文献
966.
Wu JC Liu SX Keene TD Neels A Mereacre V Powell AK Decurtins S 《Inorganic chemistry》2008,47(8):3452-3459
A pi-extended, redox-active tetradentate tetrathiafulvalene-fused salphen [salphen = N,N'-phenylenebis(salicylideneimine)] compound (L) was prepared via a direct Schiff-base condensation of the corresponding diamine-tetrathiafulvalene (TTF) precursor with salicylaldehyde. Its chelating coordination ability has been demonstrated by the formation of the corresponding transition metal complexes in the presence of M(OAc)2.nH2O (M = Co(II), Ni(II), Cu(II)) and FeCl3.6H2O. Three complexes have been characterized by single-crystal X-ray diffraction analysis showing that the TTF-salphen ligand coordinates to the metal ions in a planar mode through the nitrogen and oxygen atoms in a N2O2 cis-configuration. In the case of Fe(III), a dinuclear oxo-bridged Fe(III) complex is formed. These paramagnetic complexes are promising building blocks for the construction of dual functional materials due to their unique structural features (planarity and rigidity) as well as their inherent redox properties. 相似文献
967.
35 GHz electron paramagnetic resonance experiments on a powder sample of the magnetic molecule Mn 19 with a high-spin ground state S = 83/2 are presented. At low temperatures, the data are well described by the simulated spectra for an isolated spin with a zero-field-splitting parameter D = 0.004 cm (-1), which is, in particular, positive. Hence, Mn 19 is not a single-molecule magnet; the previously observed magnetic hysteresis at ultralow temperatures is likely due to intermolecular dipolar interactions. 相似文献
968.
A pentanuclear dysprosium hydroxy cluster of composition [Dy 5(mu 4-OH)(mu 3-OH) 4(mu-eta (2)-Ph 2acac) 4(eta (2)-Ph 2acac) 6] ( 1; Ph 2acac = dibenzoylmethanide) was prepared starting from [DyCl 3.6H 2O] and dibenzoylmethane. Both static (dc) and dynamic (ac) magnetic properties of 1 have been studied. Below 3 K, the appearance of slow relaxation of the magnetization typical for single-molecule magnets is seen, even if no hysteresis effects on the M vs H data are observed above 1.8 K. 相似文献
969.
The stability and presence of micron-scale bubbles (microbubbles) is of considerable interest in environmental, biomedical, and food sciences. Here we show that microbubbles can be formed and stabilized in a solution of low cost food-grade emulsifier (a mixture of saturated long-chain monoglycerides, diglycerides and sodium stearoyl-2-lactylate) in combination with polyethylene glycol (PEG)-40 stearate. Langmuir trough methods and fluorescence microscopy were combined to investigate the surface tension, interfacial elastic modulus, phase behavior and microstructure of monolayer shells coating these microbubbles. Our results strongly suggest that although the PEG40S is necessary to form microbubbles this component, as well as sodium stearoyl-2-lactylate, are "squeezed out" in the form of collapse aggregates. This process leaves a microbubble shell, composed of a condensed-phase low surface tension mono- and diglycerides mixture with some of the PEG40S and SSL2 remaining trapped between the condensed-phase domains. We find that other commercially available emulsifiers, containing unsaturated or bulky components unable to form condensed phases, do not to form or stabilize a microbubble layer, although they may form a foam, a finding that we relate to differences in surface tension. 相似文献
970.
Mitkina TV Lan Y Mereacre V Shi W Powell AK Rothenberger A 《Dalton transactions (Cambridge, England : 2003)》2008,(9):1136-1139
The first reactions of the trinuclear oxygen-centred iron carboxylate [Fe(3)(mu(3)-O)(mu(2)-piv)(6)(H(2)O)(3)](piv) (piv=(t)BuCOO(-)) with the neutral ligand precursor [RP(S)(mu-S)](2) (R=4-anisyl) are reported. 相似文献