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121.
122.
Zhang C Shephard NE Rhodes SM Chen Z 《Langmuir : the ACS journal of surfaces and colloids》2012,28(14):6052-6059
Sum frequency generation (SFG) vibrational spectroscopy was used to study the effect of silane headgroups on the molecular interactions that occur between poly(ethylene terephthalate) (PET) and various epoxy silanes at the PET/silane and PET/silicone interfaces. Three different silanes were investigated: (3-glycidoxypropyl) trimethoxysilane (γ-GPS), (3-glycidoxypropyl) methyl-dimethoxysilane (γ-GPMS), and (3-glycidoxypropyl) dimethyl-methoxysilane (γ-GPDMS). These silanes share the same backbone and epoxy end group but have different headgroups. SFG was used to examine the interfaces between PET and each of these silanes, as well as silanes mixed with methylvinylsiloxanol (MVS). We also examined the interfaces between PET and uncured or cured silicone with silanes or silane-MVS mixtures. Silanes with different headgroups were found to exhibit a variety of methoxy group interfacial segregation and ordering behaviors at various interfaces. The effect of MVS was also dependent upon silane headgroup choice, and the interfacial molecular structures of silane methoxy headgroups were found to differ at PET/silane and PET/silicone interfaces. Epoxy silanes have been widely used as adhesion promoters for polymer adhesives; therefore, the molecular structures probed using SFG were correlated to adhesion testing results to understand the molecular mechanisms of silicone-polymer adhesion. Our results demonstrated that silane methoxy headgroups play important roles in adhesion at the PET/silicone interfaces. The presence of MVS can change interfacial methoxy segregation and ordering, leading to different adhesion strengths. 相似文献
123.
Sara H. Elgazzar Nicoleta S. Tipi Nick J. Hubbard David Z. Leach 《European Journal of Operational Research》2012
The main aim of this paper is to develop a performance measurement method which links supply chain (SC) processes’ performance to a company’s financial strategy through demonstrating and utilising the relationship between SC processes’ performance and a company’s financial performance. 相似文献
124.
A two-dimensional numerical model is used to study the nonlinear behavior of density gradients on transverse dispersion. Numerical
simulations are conducted using d
3
f, a computer code for simulation of density-dependent flow in porous media. Considering a density-stratified horizontal flow
in a heterogeneous porous media, a series of simulations is carried out to examine the effect of the density gradient on macro-scale
transverse dispersivity. Changing salt concentration significantly affects fluid properties. This physical behavior of the
fluid involves a non-linearity in modeling the interaction between salt and fresh water. It is concluded that the large-scale
transport properties for high density flow deviate significantly from the tracer case due to the spatial variation of permeability,
described by statistical parameters, at the local-scale. Indeed, the presence of vertical flow velocities induced by permeability
variations is responsible for the reduction of the mixing zone width in the steady state in the case of a high density gradient.
Uncertainties in the model simulations are studied in terms of discretization errors, boundary conditions, and convergence
of ensemble averaging. With respect to the results, the gravity number appears to be the controlling parameter for dispersive
flux. In addition, the applicability and limitations of the nonlinear model of Hassanizadeh (1990) and Hassanizadeh and Leijnse
(1995) (Adv Water Resour 18(4):203–215, 1995) in heterogeneous porous media are investigated. We found that the main cause
of the nonlinear behavior of dispersion, which is the interaction between density contrast and vertical velocity, needs to
be explicitly accounted for in a macro-scale model. 相似文献
125.
Single-Crystal Structures of a Donor-Acceptor-Substituted Cyclopentadiene, Its Cation and Its Anion Dimer: Different Distortion of a Five-Membered Carbon Ring 1,4-Dimethyl-2,3,4,6-tetrahydro-1 H-cyclopentapyrazine-5,7-dicarbonitrile, its molecular cation, and its dimer dianion, generated by hydride abstraction or deprotonation, and crystallized, differ remarkably in their structures: the five-membered ring in the neutral compound is of (Z)-butadiene-type, whereas, in the tetrafluorborate salt, a peripheric NCCCCCN⊕ cyanine distortion occurs and in the sodium derivatives, solvated by either one or two 1,2-dimethoxyethane molecules, a cyclopentadienyl anion is formed. The structural perturbations induced by changing molecular charges are rationalized by extensive MNDO calculations, which on geometry optimization, reproduce the experimental structures and, in addition, provide charge distributions, further confirming the nN/π and π/π interactions already recognizable from the structural parameters. 相似文献
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129.
Karidi K Garoufis A Hadjiliadis N Reedijk J 《Dalton transactions (Cambridge, England : 2003)》2005,(4):728-734
A general method for the synthesis of chloro(polypyridyl)ruthenium conjugated peptide complexes via a solid-phase strategy is described. The method is applied to synthesize two positional isomers of the complex [Ru(terpy)(4-CO2H-4'-Mebpy-Gly-L-His-L-LysCONH2)Cl](PF6). Even though the separation of the isomers was only partially achieved chromatographically, the isomers were unambiguously assigned by NMR spectroscopy. The interactions of the complex [Ru(terpy)(4-CO2H-4'-Mebpy-Gly-L-His-L-LysCONH2)Cl](PF6) with CT-DNA and plasmid DNA, have been studied with various spectroscopic techniques, showing that (i) the complexes coordinatively bind to DNA preferring the bases guanine and cytosine over the bases thymine and adenine after hydrolysis of the coordinated chloride, (ii) electrostatic interactions between the complex cation and the polyanionic DNA chain assist this binding (iii) only in the case of one isomer the peptide does interact further with DNA as evidenced from 31P NMR spectroscopy, (iv) DNA unwinding occurs in all cases with high binding ratio (Ru/base) values (r > 0.3). 相似文献
130.
Spyridoula Kasselouri Achilleas Garoufis George Kalkanis Spyros P. Perlepes Nick Hadjiliadis 《Transition Metal Chemistry》1993,18(5):531-536
Summary Transition metal(II) chloro complexes of the new Schiff base ligand 1,2-bis(2-pyridylmethyleneimino)benzene (L), derived from 2-pyridinecarboxaldehyde and 1,2-phenylenediamine, were prepared. Compounds of [MnLCl2]-H2O, [CoLCl2]·2H2O, [NiLCl2] and [Zn3L2Cl4]Cl2 were prepared. Details are given of the formation of the complex [Cu(L·EtOH)Cl2], in which one molecule of EtOH adds across only one of the Schiff base {ie531-01} groups to give the coordinated ligand L·EtOH. The rationalization of this type of reaction by considering the steric requirements of the ligand is given. The complexes were characterized by elemental analyses, conductivity measurements, thermal techniques, mass spectra, magnetic susceptibilities and spectroscopic (i.r., ligand field, e.s.r., 1H n.m.r.) studies. The nitrogen donor atoms of the tetradentate ligands L and L·EtOH are assumed to adopt an essentially planar arrangement about manganese(II), cobalt(II), nickel(II) and copper(II), with the remaining axial coordination sites occupied by chloro ligands to yield high-spin octahedral molecules. A trinuclear structure, based on tetrahedrally coordinated metal ions, is proposed for the zinc(II) complex. 相似文献