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排序方式: 共有206条查询结果,搜索用时 15 毫秒
111.
Emerson C. Rios Alessandra A. Correa Fernando H. Cristovan Leandro A. Pocrifka Adriane V. Rosario 《Solid State Sciences》2011,13(11):1978-1983
Composite electrodes of poly(3,4-ethylenedioxithiophene) and manganese oxide (PEDOT/MnO2) have been prepared by electrodeposition of manganese oxide over PEDOT-modified titanium substrate. The PEDOT layers are deposited on titanium by potentiostatic deposition at 1.4 V and at two different temperatures: 5 and 25 °C (named PEDOT(5) and PEDOT(25), respectively). The electrodes are characterized by field emission gun scanning electron microscopy (FEG-SEM) and their electrochemical performances are evaluated by using cyclic voltammetry (CV) in 1 molL−1 Na2SO4. The results show an improvement in the specific capacitance (Cs) of the oxide due to the presence of the polymer layer. Considering only the MnO2 mass, the Cs values of the electrodes Ti/MnO2, Ti/PEDOT(5)/MnO2 and Ti/PEDOT(25)/MnO2, estimated by the CV technique, are 151, 159 and 199 Fg−1 at 10 mVs−1 respectively. The micrographies of electrodes show that the polymer layer leads to very significant changes in the morphology of the oxide layers, which in turn generates the improvement observed in the capacitive property. 相似文献
112.
Pereira CL Pedroso EF Doriguetto AC Ellena JA Boubekeur K Filali Y Journaux Y Novak MA Stumpf HO 《Dalton transactions (Cambridge, England : 2003)》2011,40(3):746-754
Three new bimetallic oxamato-based magnets with the proligand 4,5-dimethyl-1,2-phenylenebis(oxamato) (dmopba) were synthesized using water or dimethylsulfoxide (DMSO) as solvents. Single crystal X-ray diffraction provided structures for two of them: [MnCu(dmopba)(H(2)O)(3)](n)·4nH(2)O (1) and [MnCu(dmopba)(DMSO)(3)](n)·nDMSO (2). The crystalline structures for both 1 and 2 consist of linearly ordered oxamato-bridged Mn(II)Cu(II) bimetallic chains. The magnetic characterization revealed a typical behaviour of ferrimagnetic chains for 1 and 2. Least-squares fits of the experimental magnetic data performed in the 300-20 K temperature range led to J(MnCu) = -27.9 cm(-1), g(Cu) = 2.09 and g(Mn) = 1.98 for 1 and J(MnCu) = -30.5 cm(-1), g(Cu) = 2.09 and g(Mn) = 2.02 for 2 (H = -J(MnCu)∑S(Mn),(i)(S(Cu,i) + S(Cu),(i-1))). The two-dimensional ferrimagnetic system [Me(4)N](2n){Co(2)[Cu(dmopba)](3)}(n)·4nDMSO·nH(2)O (3) was prepared by reaction of Co(II) ions and an excess of [Cu(dmopba)](2-) in DMSO. The study of the temperature dependence of the magnetic susceptibility as well as the temperature and field dependences of the magnetization revealed a cluster glass-like behaviour for 3. 相似文献
113.
de Oliveira FM Somera BF Corazza MZ Yabe MJ Segatelli MG Ribeiro ES Lima EC Dias SL Tarley CR 《Talanta》2011,85(5):2417-2424
The present paper describes the synthesis of a new chemically modified cellulose microfiber through oxidation with sodium periodate and functionalization with N,N′-bis (2-aminoethyl)-1,2-ethanediamine for the fast and selective preconcentration of Cd(II) ions in flow system analysis. The new sorbentsorbent was characterized by FTIR, SEM, and surface area values. The uptake behavior of Cd(II) ions onto this sorbent was evaluated from kinetic data, pseudo-first-order and pseudo-second-order models, as well as from Langmuir, Freundlich and Langmuir-Freundlich adsorption isotherms. The maximum sorption capacity of 4.59 mg g−1 was estimated by the Langmuir-Freundlich model with fast kinetics for the sorption of Cd(II) described by the pseudo-second-order kinetic model. After characterization, the sorbent was packed in a mini-column, and a fast flow injection preconcentration system for Cd(II) determination by FAAS was developed. The best Cd(II) preconcentration condition, obtained by means of factorial design and response surface methodology, was achieved at pH 9.36 and a flow rate of 10 mL min−1 followed by elution with 1.0 mol L−1 nitric acid. By using 78 s preconcentration time, fast and highly sensitive determination of Cd(II) ions could be achieved with a limit of quantification of 0.20 μg L−1, preconcentration factor of 26, consumption index of 0.5 mL, concentration efficiency of 20 min−1, and sample throughput of 39 h−1. The repeatability for 10 replicate determinations was found to be 7.8 and 2.5% for Cd(II) ion concentrations of 5.0 and 100.0 μg L−1, respectively. The new sorbent efficiency for the interference-free preconcentration of Cd(II) ions was assessed by analysis of tap, mineral and lake waters, as well as synthetic seawater and normal saline waters. Furthermore, complex samples, such as biological samples, could be analysed by the proposed method in accordance with the accuracy attested by analysis of certified reference materials, TORT-2 (lobster hepatopancreas), and DOLT-4 (dogfish liver). 相似文献
114.
ElHadji Assane Diop Jenna Jacquat Nicolas Drouin Emerson Ferreira Queiroz Jean‐Luc Wolfender Tahir Diop Julie Schappler Serge Rudaz 《Electrophoresis》2019,40(21):2820-2827
Mycobacterium tuberculosis is the causative agent of tuberculosis, an infectious bacterial disease, which most commonly affects the lungs. In the search for novel active compounds or medicines against tuberculosis, an ethnopharmacological survey combined with a host‐pathogen assay has recently highlighted the potency of an aqueous extract of Combretum aculeatum. C. aculeatum is used in traditional medicine and has demonstrated a significant in vitro antimycobacterial activity. Punicalagin, an ellagitannin, was isolated and found to be related to the biological activity of the extract. An analytical method for the evaluation of punicalagin in C. aculeatum was developed by capillary electrophoresis. After method optimization, the quantification of punicalagin was achieved for the evaluation of various plant extracts to determine the content of punicalagin related to the extraction modes and conditions, origin of the plant material, and harvesting period. The developed method demonstrated that the leaves presented the highest punicalagin content compared to the seeds and stems. A decoction of 30 min in boiling water was found to be the best extraction mode of C. aculeatum. 相似文献
115.
Let X be a locally compact space with a continuous proper action of a locally compact group G. Assuming that X satisfies a certain kind of duality in equivariant bivariant Kasparov theory, we can enrich the classical construction of
Lefschetz numbers for self-maps to an equivariant K-homology class. We compute the Lefschetz invariants for self-maps of finite-dimensional
simplicial complexes and smooth manifolds. The resulting invariants are independent of the extra structure used to compute
them. Since smooth manifolds can be triangulated, we get two formulas for the same Lefschetz invariant in this case. The resulting
identity is closely related to the equivariant Lefschetz Fixed Point Theorem of Lück and Rosenberg. 相似文献
116.
We use correspondences to define a purely topological equivariant bivariant K-theory for spaces with a proper groupoid action. Our notion of correspondence differs slightly from that of Connes and Skandalis. Our construction uses no special features of equivariant K-theory. To highlight this, we construct bivariant extensions for arbitrary equivariant multiplicative cohomology theories.We formulate necessary and sufficient conditions for certain duality isomorphisms in the topological bivariant K-theory and verify these conditions in some cases, including smooth manifolds with a smooth cocompact action of a Lie group. One of these duality isomorphisms reduces bivariant K-theory to K-theory with support conditions. Since similar duality isomorphisms exist in Kasparov theory, the topological and analytic bivariant K-theories agree if there is such a duality isomorphism. 相似文献
117.
The construction of topological index maps for equivariant families of Dirac operators requires factoring a general smooth map through maps of a very simple type: zero sections of vector bundles, open embeddings, and vector bundle projections. Roughly speaking, a normally non-singular map is a map together with such a factorisation. These factorisations are models for the topological index map. Under some assumptions concerning the existence of equivariant vector bundles, any smooth map admits a normal factorisation, and two such factorisations are unique up to a certain notion of equivalence. To prove this, we generalise the Mostow Embedding Theorem to spaces equipped with proper groupoid actions. We also discuss orientations of normally non-singular maps with respect to a cohomology theory and show that oriented normally non-singular maps induce wrong-way maps on the chosen cohomology theory. For K-oriented normally non-singular maps, we also get a functor to Kasparov's equivariant KK-theory. We interpret this functor as a topological index map. 相似文献
118.
Vedanth Nair Matthew Sirignano Benjamin Emerson Ben Halls Naibo Jiang Josef Felver Sukesh Roy Jim Gord Tim Lieuwen 《Proceedings of the Combustion Institute》2019,37(2):1489-1496
This paper analyzes the time averaged flow structure of a reacting jet in cross flow (RJICF), emphasizing the structure of the counter-rotating vortex pair (CVP) by using simultaneous tomographic particle image velocimetry (TPIV) and hydroxyl radical planar laser induced fluorescence (OH-PLIF). It was performed to determine the extent to which heat release, and the associated effects of gas expansion and baroclinic vorticity production, impact the structure of the CVP. These results show the clear presence of a CVP in the time averaged flow field, whose trajectory lies below the jet centerline on either side of the centerplane. Consistent with other measurements of high momentum flux ratio JICF in nonreacting flows, there is significant asymmetry in strength of the two vortex cores. The strength and structure of the CVP was quantified with vorticity and swirling strength (λci), showing that some regions of the flow with high shear are not necessarily accompanied by large scale bulk flow rotation and vice-versa. The OH PLIF measurement allows for correlation of the flame position with the dominant vortical structures, showing that the leeward flame branch lies slightly above, as well as, in the region between the CVP cores. 相似文献
119.
Conceptual improvements to a non-contact optical strain measurement technique for high-speed flywheels are presented. The
improvements include a novel reflective pattern that allows for greater displacement sensitivity, the ability to measure rigid
body vibrations and separate the associated vibration-induced displacement from the strain-induced displacement, and the ability
to compensate for potential sensor drift during flywheel operation. The effects of rigid body rotor vibrations and sensor
drift have been modeled and techniques to compensate for the errors associated with such effects are presented. Experimental
results validate the ability of the technique to separate such vibrations from axisymmetric flexible body displacements, and
to compensate for errors due to in-plane and out-of-plane pattern misalignment and sensor drift. Displacement measurements
made on an aluminum rotor operating at a maximum speed of 16 krpm (255 m/s at the point of measurement) were made with ±1
μm accuracy. At this speed, hoop strains were found to be within 40–125 με of theoretical predictions, provided a proper accounting
is made for thermal strains. Relative to the theoretical hoop strains, the measured hoop strains differed by 5.0 to 6.4% at
16 krpm. 相似文献
120.
Anne M. Grillet Carlton F. Brooks Benjamin J. Ash John A. Emerson 《Experiments in fluids》2007,42(2):207-216
Fluorescence imaging methods are explored as tools to study multi-component wetting of liquids. A novel approach was employed
using polymer labeled with contrasting fluorescent dyes, which allow optical recognition and also caused differences in surface
tension between blend components. Total internal reflection-fluorescence microscopy probes a thin surface layer to the order
of 100 nm to investigate the structure of the spreading drop next to the substrate. Dye segregation out of solution and phase
separation of polymer blends were observed. Confocal microscopy can visualize the larger three-dimensional structure of sessile
drops. Component segregation was observed and quantified using relative fluorescence intensities. 相似文献