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71.
Prof. Dr. Ming Li Prof. Dr. Andrew P. Dove Dr. Vinh X. Truong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(6):2304-2308
Photochemical ligation is important in biomaterials engineering for spatiotemporal control of biochemical processes. Such reactions however generally require activation by high energy UV or short wavelength blue light, which can limit their use as a consequence of the potential of these high energy light sources to damage living cells. Herein, we present an additive-free, biocompatible, chemical ligation triggered by mild visible light. BODIPY dyes with a pendant thioether attached at the meso-position undergo photolysis of the [C−S] bond under green light (λ=530 nm) excitation, producing an ion pair intermediate that can react specifically with a propiolate group. The utility of this photochemical ligation in materials science is demonstrated by the fabrication of hydrogels with specific architectures, photo-immobilization of biomacromolecules, and live cell encapsulation within a hydrogel scaffold. 相似文献
72.
73.
Jan M. Becker Dr. Sarah Tempelaar Matthew J. Stanford Ryan J. Pounder James A. Covington Dr. Andrew P. Dove Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(20):6099-6105
The ring‐opening polymerisation of lactide by a range of amino–oxazoline and amino–thiazoline catalysts is reported. The more electron‐rich derivatives are demonstrated to be the most highly active and polymerisation is well controlled, as evidenced by the linear relationship between the molecular weight and both the monomer conversion and the monomer‐to‐initiator ratio. Mechanistic studies reveal significant interactions between the monomer, initiator and catalyst and that the polymerisation is first order with respect to each of these components. These observations indicate that the polymerisation operates by a general base/pseudo‐anionic mechanism. 相似文献
74.
Ruairí P. Brannigan Anthony Walder Andrew P. Dove 《Journal of polymer science. Part A, Polymer chemistry》2014,52(16):2279-2286
9‐Phenyl‐2,4,8,10‐tetraoxaspiro[5,5]undecanone (PTO) was synthesized from pentaerythritol via the acid‐catalyzed acetal formation reaction with benzaldehyde and subsequent ring closure with ethyl chloroformate. The cyclic carbonate monomer was subsequently polymerized by ring‐opening polymerization (ROP) initiated from 1,4‐butanediol (1,4‐BDO) using the 1‐(3,5‐bis(trifluoromethyl)phenyl)‐3‐cyclohexylthiourea and 1,8‐diazabicyclo[5.4.0]undec‐7‐ene dual organocatalytic system. It was found that the organocatalyst allowed for the synthesis of well‐defined polymers with minimal adverse side reactions and low dispersities. This system was then employed in the ROP of PTO initiated from an α,ω‐dihydroxy poly(caprolactone) (PCL) macroinitiator, with varying molecular weights, to yield a series of A‐B‐A block copolymers. These materials were characterized by 1H NMR spectroscopy, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis and tensile analysis. It was found that the chain extension from PCL with poly(PTO) (PPTO) blocks yielded a thermoplastic material with superior tensile properties (elongation and Young's modulus) to that of the PCL homopolymer. Furthermore, it was noted that the addition of PPTO could be employed to alter the crystallization properties (crystallization temperature (Tc), and percentage crystallization) of the central PCL block. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2279–2286 相似文献
75.
Philip KP Dove EL McPherson DD Gotteiner NL Vonesh MJ Stanford W Reed JE Rumberger JA Chandran KB 《IEEE transactions on medical imaging》1994,13(2):241-253
Quantitative evaluation of cardiac function from cardiac images requires the identification of the myocardial walls. This generally requires the clinician to view the image and interactively trace the contours. This method is susceptible to great variability that depends on the experience and knowledge of the particular operator tracing the contours. The particular imaging modality that is used may also add tracing difficulties. Cine-computed tomography (cine-CT) is an imaging modality capable of providing high quality cross-sectional images of the heart. CT images, however, are cluttered, i.e., objects that are not of interest, such as the chest wall, liver, stomach, are also visible in the image. To decrease this variability, investigators have developed computer-assisted or near-automatic techniques for tracing these contours. All of these techniques, however, require some operator intervention to confidently identify myocardial borders. The authors present a new algorithm that automatically finds the heart within the chest, and then proceeds to outline (detect) the myocardial contours. Information at each tomographic slice is used to estimate the contours at the next tomographic slice, thus allowing the algorithm to work in near-apical cross-sectional images where the myocardial borders are often difficult to identify. The algorithm does not require operator input and can be used in a batch mode to process large quantities of data. An evaluation and correction phase is included to allow an operator to view the results and selectively correct portions of contours. The authors tested the algorithm by automatically identifying the myocardial borders of 27 cardiac images obtained from three human subjects and quantitatively comparing these automatically determined borders with those traced by an experienced cardiologist. 相似文献
76.
Ekhard K. H. Salje Martin T. Dove Igor Tsatskis Kim Locherer Jutta Chrosch 《Phase Transitions》2013,86(4):539-569
Materials which undergo structural phase transitions with bilinear coupling between the spontaneous strain (e sp i ) and the thermodynamic order parameter (Q) of the type λi e sp i Q show characteristic fluctuation pattern at T > T c. Snapshots of such pattern show tweedlike structures with butterfly shaped structure factors. Some experimental fluctuation patterns are reviewed and compared with the theoretical predictions. At T ≤ Tc , characteristic microstructures often include structural twinning. The relevant energy expressions for order/disorder systems are recalled and their contribution to thermodynamic fluctuations are described. It is anticipated that some of the physical mechanisms may play a role also in improper ferroelastics with coupling of the type λi e sp i Q 2 k where Qk is a component of a degenerate order parameter Q = {Qk}. 相似文献
77.
Martin T. Dove Anne Bosenick Eva R. Myers Michele C. Warren Simon A.T. Redfern 《Phase Transitions》2013,86(3):205-226
We review the methodology of using computer models to obtain quantitative information about cation ordering. Empirical interatomic potentials or ab initio electronic structure calculations are used to generate the energies for many configurations containing disordered arrangements of cations, and the parameters in model Hamiltonians can be determined from these energies. Monte Carlo simulations are then used to generate ensemble averages as functions of temperature or chemical composition. Analysis of the Monte Carlo ensembles directly yields the temperature dependence of long-range and short-range order, and thermodynamic quantities such as energy and heat capacity. Use of thermodynamic integration allows for the calculation of entropy and free energy. The methods are illustrated by examples showing long-range order/disorder phase transitions (feldspars), short-range order in solid solutions (pyrope-grossular), and non-convergent ordering (magnesium aluminate spinel); where comparisons with experimental data are possible, the model calculations are seen to give results that are reasonably accurate. The example in which ab initio electronic structure calculations are used show that it is now possible to extract accurate thermodynamic data for ordering processes using models that require no prior experimental data. 相似文献
78.
A method for constructing resistance-wire strain gages which may be imbedded in a plastic model without materially altering the stress pattern in the model is presented. The methods used to calibrate the gages and the photoelastic tests made to investigate the effect of the gages on the stress pattern are described. The application of this new three-dimensional technique to evaluate the stress distribution in a thick-walled cylindrical pressure vessel is discussed. Correlation between experimental data and calculated values is given. 相似文献
79.
The local order in amorphous films of As2Se3, As2Se2Te, As2SeTe2, and As2Te3 has been examined by scanning electron diffraction with direct recording of the intensity of the elastically scattered electrons. The radial distribution functions indicate that there is a systematic increase in mean nearest neighbor distance as the Te concentration is increased, butthe mean coordination number increases slightly around 2.4. Pair function calculation of models shows that the 3-aand 2-fold coordinations of arsenic and chalcogens are retained in these glasses and the interatomic distances are close to those predicted from the Pauling covalent atomic radii of the constituent atomic species. The short range order appears to be similar in amorphous and crystalline As2Se3, but different in the case of As2Te3 as found by previous workers on bulk materials. 相似文献
80.
Recently it has been shown that the incorporation of AℓPO4 in a Zn2SiO4 phosphor results in an improved cathodoluminescent efficiency1. We report here on electron trap distributions in the substituted phosphors derived from UV excited thermoluminescent glow
curve measurements. It has been found that the glow curve peaks are modified appreciably with AℓPO4 addition, but new peaks do not appear to be introduced. This shift, however is largely due to a considerable change in the
absolute value of the detrapping rate, while there is only a relatively small change in the activation energies for detrapping.
The phosphors were prepared in a silica rich environment and for the present study were not subjected to post preparation
annealing treatments. 相似文献