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51.
52.
Electrochemical Identification and Categorization of the Protective Quality of Intact and Damaged Coatings 下载免费PDF全文
Defective polymeric coatings that are particularly relevant in the conservation of outdoor metalwork, are analyzed using electrochemical impedance spectroscopy (EIS), validated by Kramers? Kronig transformations, and modeled using electrical equivalent circuit models (EECs). Using twenty different coated panels of five different coating types, ten mathematical methods for categorizing the protective qualities of coatings are explored as simpler and faster alternatives to circuit modeling; three methods gave a perfect correlation with the category determined by circuit modeling. Our findings highlight the need for fitting data to EECs before relying upon purely mathematical parameters for evaluating protective coating quality. 相似文献
53.
Capillary electrophoretic determination of inorganic ions in a prenatal vitamin formulation 总被引:1,自引:0,他引:1
Michael E. Swartz 《Journal of chromatography. A》1993,640(1-2):441-444
Methods for the quantitative analysis of three cations (calcium, iron and zinc), and the qualitative analysis of several anionic species (chloride, sulfate, nitrate, citrate, fumerate, phosphate, carbonate and acetate) from a prenatal vitamin formulation by two different capillary ion electrophoresis methods are reported. The cation method was evaluated for detection and quantitation limits, precision, accuracy and linearity. For standard solutions, detection limits into the ng/ml range, and reproducibility that averaged less than 1% for migration time and 2% for area response were generated. Calibration plots exhibited linearity in excess of three orders of magnitude. In addition, excellent agreement between capillary ion electrophoresis and flame photometry quantitative results for the cation analyses were obtained. 相似文献
54.
A Soibel SS Banerjee Y Myasoedov ML Rapparort E Zeldov S Ooi T Tamegai 《Pramana》2002,58(5-6):893-898
Using a novel differential magneto-optical imaging technique we investigate the phenomenon of vortex lattice melting in crystals
of Bi2Sr2CaCu2O8 (BSCCO). The images of melting reveal complex patterns in the formation and evolution of the vortex solid-liquid interface
with varying field (H)/temperature (T). We believe that the complex melting patterns are due to a random distribution of material disorder/inhomogeneities across
the sample, which create fluctuations in the local melting temperature or field value. To study the fluctuations in the local
melting temperature/field, we have constructed maps of the melting landscape T
m(H, r), viz., the melting temperature (T
m) at a given location (r) in the sample at a given field (H). A study of these melting landscapes reveals an unexpected feature: the melting landscape is not fixed, but changes rather
dramatically with varying field and temperature along the melting line. It is concluded that the changes in both the scale
and shape of the landscape result from the competing contributions of different types of quenched disorder which have opposite
effects on the local melting transition. 相似文献
55.
Let xi ≥ 0, yi ≥ 0 for i = 1,…, n; and let aj(x) be the elementary symmetric function of n variables given by aj(x) = ∑1 ≤ ii < … <ij ≤ nxii … xij. Define the partical ordering x <y if aj(x) ≤ aj(y), j = 1,… n. We show that , where {xα}i = xαi. We also give a necessary and sufficient condition on a function f(t) such that x <y ? f(x) <f(y). Both results depend crucially on the following: If x <y there exists a piecewise differentiable path z(t), with zi(t) ≥ 0, such that z(0) = x, z(1) = y, and z(s) <z(t) if 0 ≤ s ≤ t ≤ 1. 相似文献
56.
A Gurtu P K Malhotra I S Mittra P M Sood SC Gupta VK Gupta GL Kaul LK Mangotra Y Prakash NK Rao ML Sharma 《Pramana》1974,3(5):311-322
This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett. 50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratioR em = 〈n s〉/〈n ch〉, where 〈n ch〉 is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1·6 at 68 GeV/c and attains a constant value of 1·71 ± 0·04 in the region 200 to 8000 GeV/c. Furthermore,R em = 1·71 implies an effectiveA-dependence ofR A =A 0.18,i.e., a very weak dependence. Predictions ofR em on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production. 相似文献
57.
Swartz BD Reinartz NM Brennessel WW García JJ Jones WD 《Journal of the American Chemical Society》2008,130(26):8548-8554
The reaction of [(dippe)NiH]2 with 2-methyl-3-butenenitrile (2M3BN) in solvents spanning a wide range of polarities shows significant differences in the ratio of C-H and C-CN activated products. C-H cleavage is favored in polar solvents, whereas C-C cleavage is favored in nonpolar solvents. This variation is attributed to the differential solvation of the transition states, which was further supported through the use of sterically bulky solvents and weakly coordinating solvents. Variation of the temperature of reaction of [(dippe)NiH]2 with 2M3BN in decane and N,N-dimethylformamide (DMF) allowed for the calculation of Eyring activation parameters for the C-CN activation and C-H activation mechanisms. The activation parameters for the C-H activation pathway were DeltaH(double dagger) = 11.4 +/- 5.3 kcal/mol and DeltaS(double dagger) = -45 +/- 15 e.u., compared with DeltaH(double dagger) = 17.3 +/- 2.6 kcal/mol and DeltaS(double dagger) = -29 +/- 7 e.u. for the C-CN activation pathway. These parameters indicate that C-H activation is favored enthalpically, but not entropically, over C-C activation, implying a more ordered transition state for the former. 相似文献
58.
Lugo-Mas P Taylor W Schweitzer D Theisen RM Xu L Shearer J Swartz RD Gleaves MC Dipasquale A Kaminsky W Kovacs JA 《Inorganic chemistry》2008,47(23):11228-11236
The syntheses and structures of three new coordinatively unsaturated, monomeric, square-pyramidal thiolate-ligated Fe(III) complexes are described, [Fe(III)((tame-N(3))S(2)(Me2))](+) (1), [Fe(III)(Et-N(2)S(2)(Me2))(py)](1-) (3), and [Fe(III)((tame-N(2)S)S(2)(Me2))](2-) (15). The anionic bis-carboxamide, tris-thiolate N(2)S(3) coordination sphere of 15 is potentially similar to that of the yet-to-be characterized unmodified form of NHase. Comparison of the magnetic and reactivity properties of these reveals how anionic charge build up (from cationic 1 to anionic 3 and dianionic 15) and spin-state influence apical ligand affinity. For all of the ligand-field combinations examined, an intermediate S = 3/2 spin state was shown to be favored by a strong N(2)S(2) basal plane ligand field, and this was found to reduce the affinity for apical ligands, even when they are built in. This is in contrast to the post-translationally modified NHase active site, which is low spin and displays a higher affinity for apical ligands. Cationic 1 and its reduced Fe(II) precursor are shown to bind NO and CO, respectively, to afford [Fe(III)((tame-N(3))S(2)(Me))(NO)](+) (18, nu(NuO) = 1865 cm(-1)), an analogue of NO-inactivated NHase, and [Fe(II)((tame-N(3))S(2)(Me))(CO)] (16; nu(CO) stretch (1895 cm(-1)). Anions (N(3)(-), CN(-)) are shown to be unreactive toward 1, 3, and 15 and neutral ligands unreactive toward 3 and 15, even when present in 100-fold excess and at low temperatures. The curtailed reactivity of 15, an analogue of the unmodified form of NHase, and its apical-oxygenated S = 3/2 derivative [Fe(III)((tame-N(2)SO(2))S(2)(Me2))](2-) (20) suggests that regioselective post-translational oxygenation of the basal plane NHase cysteinate sulfurs plays an important role in promoting substrate binding. This is supported by previously reported theoretical (DFT) calculations. 相似文献
59.
The face ring of a simplicial complex modulo m generic linear forms is shown to have finite local cohomology if and only if the link of every face of dimension m or more is nonsingular, i.e., has the homology of a wedge of spheres of the expected dimension. This is derived from an enumerative result for local
cohomology of face rings modulo generic linear forms, as compared with local cohomology of the face ring itself. The enumerative
result is generalized to squarefree modules. A concept of Cohen–Macaulay in codimension c is defined and characterized for arbitrary finitely generated modules and coherent sheaves. For the face ring of an r-dimensional complex Δ, it is equivalent to nonsingularity of Δ in dimension r − c; for a coherent sheaf on projective space, this condition is shown to be equivalent to the same condition on any single generic
hyperplane section. The characterization of nonsingularity in dimension m via finite local cohomology thus generalizes from face rings to arbitrary graded modules. 相似文献
60.
We show that every abelian topological group contains many interesting sets which are both compact and sequentially compact. Then we can deduce some useful facts, e.g.,
- (1)
- if G is a Hausdorff abelian topological group and μ:N2→G is countably additive, then the range μ(N2)={μ(A):A⊆N} is compact metrizable;
- (2)
- if X is a Hausdorff locally convex space and {xj}⊂X, then F={∑j∈Δxj:Δ⊂N, Δ is finite} is relatively compact in (X,weak) if and only if F is relatively compact in X, and if and only if F is relatively compact in (X,F(M)) where F(M) is the Dierolf topology which is the strongest 〈X,X′〉-polar topology having the same subseries convergent series as the weak topology.