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排序方式: 共有75条查询结果,搜索用时 31 毫秒
31.
Sean T. Hunt Tarit Nimmanwudipong Yuriy Romn‐Leshkov 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(20):5231-5236
Transition‐metal carbides (TMCs) exhibit catalytic activities similar to platinum group metals (PGMs), yet TMCs are orders of magnitude more abundant and less expensive. However, current TMC synthesis methods lead to sintering, support degradation, and surface impurity deposition, ultimately precluding their wide‐scale use as catalysts. A method is presented for the production of metal‐terminated TMC nanoparticles in the 1–4 nm range with tunable size, composition, and crystal phase. Carbon‐supported tungsten carbide (WC) and molybdenum tungsten carbide (MoxW1−xC) nanoparticles are highly active and stable electrocatalysts. Specifically, activities and capacitances about 100‐fold higher than commercial WC and within an order of magnitude of platinum‐based catalysts are achieved for the hydrogen evolution and methanol electrooxidation reactions. This method opens an attractive avenue to replace PGMs in high energy density applications such as fuel cells and electrolyzers. 相似文献
32.
Kishore Kumar Hotha Swapan Roychowdhury Ramesh Mullangi L. K. Ravindranath 《Biomedical chromatography : BMC》2013,27(9):1192-1199
A rapid, simple, specific and sensitive LC‐MS/MS method has been developed and validated for the enantiomeric quantification of amlodipine (AML) isomers [R‐amlodipine (R‐AML) and S‐amlodipine (S‐AML)] with 200 μL of human plasma using R‐AML‐d4 and S‐AML‐d4 as corresponding internal standards as per regulatory guidelines. A simple liquid–liquid extraction process was used to extract these analytes from human plasma. The total run time was 3.5 min and the elution of R‐AML, S‐AML, R‐AML‐d4 and S‐AML‐d4 occurred at 1.62, 2.51, 1.63 and 2.53 min, respectively. This was achieved with a mobile phase consisting of 0.2% ammonia–acetonitrile (20:80, v/v) at a flow rate of 1 mL/min on a Chiralcel OJ RH column. A linear response function was established for the range of concentrations 0.1–10 ng/mL (r >0.998) for each enantiomer. The intra‐ and inter‐day precision values for both enantiomers met the acceptance criteria. Both enantiomers were stable in a set of stability studies, viz. bench‐top, auto‐sampler, freeze–thaw cycles and long‐term. The current assay was successfully applied to a pharmacokinetic study to quantitate AML enantiomers following oral administration of 10 mg AML tablet to humans. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
33.
A new type of outer synchronization between two distinct networks, composed of different classes of oscillators is investigated with the help of open plus closed loop approach, proposed earlier by Jackson and Grosu. It is further assumed that all the members of the network differ in their parameter values. Asymptotic stability of the zero solution of the error equation is proved analytically. Numerical simulation reveals that the same type of members of the two networks gets synchronized. 相似文献
34.
With the help of the general theory of the Heun equation, this paper completes previous work by the authors and other groups
on the explicit representation of the massive gravitino propagator in four-dimensional de Sitter space. As a result of our
original contribution, all weight functions which multiply the geometric invariants in the gravitino propagator are expressed
through Heun functions, and the resulting plots are displayed and discussed after resorting to a suitable truncation in the
series expansion of the Heun function. It turns out that there exist two ranges of values of the independent variable in which
the weight functions can be divided into dominant and sub-dominant families. 相似文献
35.
Pradip K. Gadekar Maryann Hoermann Faith Corbo Rajiv Sharma S. Sarveswari Abhijit Roychowdhury 《Tetrahedron letters》2014
Herein, we have developed a mild and selective reductive deprotection method for the MAc protected alcohols using sodium borohydride. The new deprotection conditions provide a complete orthogonality between O-MAc and other protecting groups such as tert-butyl ester, N-Boc, Fmoc, Cbz, O-TBDMS, N-benzyl, O-benzyl, O-acetyl, N-acetyl, N-MAc, etc. In addition to O-MAc deprotection, this method is also applicable for S-MAc deprotection. 相似文献
36.
Debattam Sarkar Dr. Tanmoy Ghosh Dr. Ananya Banik Dr. Subhajit Roychowdhury Prof. Dirtha Sanyal Prof. Kanishka Biswas 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):11208-11215
A two-step optimization strategy is used to improve the thermoelectric performance of SnTe via modulating the electronic structure and phonon transport. The electrical transport of self-compensated SnTe (that is, Sn1.03Te) was first optimized by Ag doping, which resulted in an optimized carrier concentration. Subsequently, Mn doping in Sn1.03−xAgxTe resulted in highly converged valence bands, which improved the Seebeck coefficient. The energy gap between the light and heavy hole bands, i.e. ΔEv decreases to 0.10 eV in Sn0.83Ag0.03Mn0.17Te compared to the value of 0.35 eV in pristine SnTe. As a result, a high power factor of ca. 24.8 μW cm−1 K−2 at 816 K in Sn0.83Ag0.03Mn0.17Te was attained. The lattice thermal conductivity of Sn0.83Ag0.03Mn0.17Te reached to an ultralow value (ca. 0.3 W m−1 K−1) at 865 K, owing to the formation of Ag7Te4 nanoprecipitates in SnTe matrix. A high thermoelectric figure of merit (z T≈1.45 at 865 K) was obtained in Sn0.83Ag0.03Mn0.17Te. 相似文献
37.
Tuhin Roychowdhury Dhruv Shah Varun Jain Dhananjay I. Patel Berg Dodson William Skinner James N. Hilfiker Stacey J. Smith Matthew R. Linford 《Surface and interface analysis : SIA》2020,52(7):433-441
In this work, copper and tungsten were sputtered onto silicon wafers by direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS). The resulting films were characterized by energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and X-ray diffraction (XRD). By EDX and XPS, all the sputtered films showed only the expected metal peaks. By XPS, the surfaces sputtered by DCMS were richer in oxygen than those produced by HiPIMS. By AFM, the surfaces were quite smooth. The root mean square (RMS) roughness values are as follows: 0.83 nm (W, HiPIMS), 1.10 nm (W, DCMS), 0.85 nm (Cu, HiPIMS), and 1.78 nm (Cu, DCMS). By SEM, the HiPIMS films exhibited smaller grain sizes, which was confirmed by XRD. The crystallite sizes estimated by XRD are as follows: 4 nm (W, body-centered cubic, HiPIMS), 13 nm (W, body-centered cubic, DCMS), 7 nm (W, cubic, HiPIMS), 14 nm (W, cubic, DCMS), 25 nm (Cu, HiPIMS), and 35 nm (Cu, DCMS). By SE, the HiPIMS surfaces showed higher refractive indices, which suggested that they were denser and less oxidized than the DCMS surfaces. 相似文献
38.
A collocated, non-orthogonal grid based finite volume technique has been applied for investigating the two dimensional natural
convective flow and heat transfer around a heated cylinder kept in a square enclosure. The effects of different enclosure
wall thermal boundary conditions, fluid Prandtl number and the ratio between enclosure and cylinder dimensions (aspect ratio)
upon the flow and thermal features, have been systematically studied. It is observed that the patterns of recirculatory flow
and thermal stratification in the fluid are significantly modified, if any of these parameters is varied. The overall heat
transfer rates are also affected due to the changes in the flow and temperature patterns. The study presents useful observations
regarding the variation of local Nusselt number along each wall, for the different cases considered.
Received on 2 August 2000 / Published online: 29 November 2001 相似文献
39.
Mrinal Kanti Roychowdhury 《Chaos, solitons, and fractals》2011,44(11):947-953
We determine the quantization dimension function for the image measure supported on a recurrent self-similar set of an ergodic Markov measure, and its relationship with the temperature function of the thermodynamic formalism arising in multifractal analysis is established. 相似文献
40.
We study empirically how the fame of WWI fighter-pilot aces, measured in numbers of web pages mentioning them, is related to their achievement, measured in numbers of opponent aircraft destroyed. We find that on the average fame grows exponentially with achievement; the correlation coefficient between achievement and the logarithm of fame is 0.72. The number of people with a particular level of achievement decreases exponentially with the level, leading to a power-law distribution of fame. We propose a stochastic model that can explain the exponential growth of fame with achievement. Next, we hypothesize that the same functional relation between achievement and fame that we found for the aces holds for other professions. This allows us to estimate achievement for professions where an unquestionable and universally accepted measure of achievement does not exist. We apply the method to Nobel Prize winners in Physics. For example, we obtain that Paul Dirac, who is a hundred times less famous than Einstein contributed to physics only two times less. We compare our results with Landau’s ranking. 相似文献