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1.
In the pursuit to enlarge the library of polyimide materials for energy applications, new polyimide/MWCNTs composite films have been developed by MWCNTs-assisted polycondensation reaction of a hydroxyl and triphenylmethane-containing diamine with benzophenone tetracarboxylic dianhydride targeting to highlight their electrical storage capability as flexible electrodes in micro-supercapacitors (mSCs). The Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance, UV–vis, fluorescence, and Raman spectroscopies were used to demonstrate the evolution of interfacial interactions between MWCNTs and the precursors (diamine monomer and intermediate polyamidic acid) and polyimide matrix that proved to be the origin of MWCNTs homogeneous dispersion. Thus, composite films incorporating 1, 3, 5, and 10 w.t.% MWCNTs were obtained and thoroughly investigated with regard to their morphology, mechanical behavior, thermal stability, and electrical conductivity. The electrochemical performance of these composites was first analyzed in a classical three-electrode cell by cyclic voltammetry and galvanostatic charge-discharge in both aqueous and organic electrolyte systems. By far, the best electrical storage capacity was obtained with the composite polyimide film containing 10% MWCNTs that was further used as both active material and current collector in a flexible symmetric mSC realized by a straightforward and low-cost procedure. In the attempt to better exploit the advantages of this composite film, it was layered with a graphite-containing paint and tested as an electrode in a flexible mSC, which provided satisfactory results. To our knowledge, this is the first report on the electrical charge storage capability of a polyimide/MWCNTs free-standing film as a flexible electrode in mSCs, which do not require time- and resource-consuming processing steps.  相似文献   
2.
Silver-mediated α-dC–Ag+–β-dC hybrid base pairs decorated with 5-iodo- or 5-octadiynyl residues are well accommodated in duplex DNA. A strong Tm increase and favorable thermodynamic data for duplex DNA were observed after addition of silver ions. The phenomenon is particularly obvious when both nucleobases of the base pairs are functionalized. Neither the position of the base pair, nor the type of 5-substituent had a negative influence. On the contrary, functionalization of conventional silver-mediated β-dC–Ag+–β-dC homo base pairs showed a negative impact induced by the bulky substituents. To this end, cytosine modified 12-mer oligodeoxynucleotides were prepared by solid-phase synthesis employing new α-anomeric 2′-deoxycytidine phosphoramidites. A multigram scale synthesis was developed for 5-iodo-α-d -2′-deoxycytidine ( 1 ) employing the direct glycosylation of cytosine with Hoffer's α-d -halogenose followed by separation of anomeric DMT nucleosides. Regarding base-pair stability and functionalization silver-mediated α/β-dC hybrid base pairs were found to be superior to β/β-dC homo pairs. According to their extraordinary properties, they might find applications in DNA diagnostics, material science, or nanotechnology.  相似文献   
3.
We prove a result on the preservation of the pathwise uniqueness property for the adapted solution to backward stochastic differential equation under perturbations.  相似文献   
4.
Existence, uniqueness, continuous dependence with respect to controls and convergence in the probability of finite differences for controlled semilinear stochastic evolution equations, driven by continuous semimartingales, are considered under Lipschitz and monotone coefficients. The existence of discrete-optimal feedback controls for an associated optimization problem is proved.  相似文献   
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6.
One of the central problems in the mathematical theory of turbulence is that of breakdown of smooth (indefinitely differentiable) solutions to the equations of motion. In 1934 J. Leray advanced the idea that turbulence may be related to the spontaneous appearance of singularities in solutions of the 3—D incompressible Navier-Stokes equations. The problem is still open. We show in this report that breakdown of smooth solutions to the 3—D incompressible slightly viscous (i.e. corresponding to high Reynolds numbers, or highly turbulent) Navier-Stokes equations cannot occur without breakdown in the corresponding solution of the incompressible Euler (ideal fluid) equation. We prove then that solutions of distorted Euler equations, which are equations closely related to the Euler equations for short term intervals, do breakdown.Sponsored by the United States Army under Contract No. DAAG29-80-C-0041, and partially supported by the National Science Foundation under Grant No. MCS-82-01599  相似文献   
7.
Capillary electrochromatography requires the deposition of a stationary phase inside the capillary. In this paper the sol-gel method is proposed for this purpose. The gels were prepared externally and injected into a fused-silica capillary, where anchorage to the capillary wall was possible through condensation reactions between the silanol groups of the capillary wall and the residual silanol groups the gel. Contrary to a commonly used practice, alkaline pretreatment of the inner capillary wall prior to the introduction and anchoring of the gel was found to be only marginally effective in improving the mechanical stability of the column. The influence of various parameters, such as the pH, the water content, the presence of alcohol (ethanol) on the formation of tetraethoxysilane (TEOS)-n-octyltriethoxysilane (C8-TEOS) hybrid gels of varied composition is discussed. The pH and the amount of water present were found to be the determining factors in the preparation of a stable gel with the desired mechanical and chromatographic properties. By carrying out the gel formation at 80 degrees C, capillary columns could be produced in 2.5 h. While an acidic pH was required during (external) gel formation, subsequent treatment of the gel inside the capillary with an alkaline solution ('aging') was found to improve separation and stationary phase capacity significantly. The capillary columns were subsequently used to separate a mixture of polycyclic aromatic hydrocarbons in less than 3 min.  相似文献   
8.
One proves that any rank 3 topological vector bundle on a homogeneous rational 3-fold has an algebraic structure. The proof uses extensions of ideals by rank 2 vector bundles. The paper also contains a construction of rank 3 vector bundles on 3-folds using extensions of ideals by rank 2 reflexive sheaves.  相似文献   
9.
The ideal way to prepare efficient, yet robust stationary phases for microanalytical high-resolution methods such as capillary chromatography and electrochromatography remains to be defined. In this contribution a one step sol-gel process is proposed for the production of monolithic, macroporous nanocomposite phases in fused silica capillaries, which require no additional derivatization, since they already bear the interactive (C8) moieties. The effect of the catalyst, the water content, the pH, as well as that of certain additives on monolith formation and porosity is investigated. Volume shrinkage and a tendency to crack were the major obstacles to overcome. Homogeneous stationary phases could be produced by applying a pH gradient during sol formation, thereby changing the catalytic principle from acidic (0.1 M HCl) to basic (gradual formation of OH as a consequence of the hydrolysis of N-methylformamide). Gelation/coacervation of suchgels could be induced by the addition of N,N-diethylamine. The water content during sol formation was determined as decisive for pore formation, with 250% of the amount theoretically needed for complete hydrolysis of all precursors giving optimal results. The volume shrinkage problem during xerogel formation was resolved by integrating dialkyldialkoxysilane units (dimethyldiethoxysilane 35 mol%) into the silica network.  相似文献   
10.
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