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301.
The modified Bernoulli numbers $$ B_{n}^{*} = \sum_{r=0}^{n} \binom{n+r}{2r} \frac{B_{r}}{n+r}, \quad n > 0 $$ introduced by D. Zagier in 1998 are extended to the polynomial case by replacing B r by the Bernoulli polynomials B r (x). Properties of these new polynomials are established using the umbral method as well as classical techniques. The values of x that yield periodic subsequences $B_{2n+1}^{*}(x)$ are classified. The strange 6-periodicity of $B_{2n+1}^{*}$ , established by Zagier, is explained by exhibiting a decomposition of this sequence as the sum of two parts with periods 2 and 3, respectively. Similar results for modifications of Euler numbers are stated. 相似文献
302.
In recent years, the high availability of methane in the shale gas reserves has raised significant interest in its conversion to high-value chemicals but this process is still not commercially viable. Metal oxides, due to their surface heterogeneity and the presence of Lewis acidic and basic site pairs are known to facilitate the activation of C−H bonds of methane. In this work, we investigate the C−H bond activation of methane on pristine and doped γ-Al2O3 clusters using density functional theory (DFT) calculations. Our results demonstrate that the polar pathway is energetically preferred over the radical pathway on these systems. We found that the metal dopants (boron and gallium) not only alter the catalytic activity of dopant sites but this effect is more pronounced on some of the adjacent sites (non-local). Among the selected dopants, gallium greatly improves the catalytic activity on most of the site pairs (including most active and least active) of pristine γ-Al2O3. Additionally, we identified a correlation between H2 binding energies and the C−H activation free energies on Ga-doped γ-Al2O3. 相似文献
303.
Tewari JC Dixit V Cho BK Malik KA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(3):1119-1127
The capacity to confirm the variety or origin and the estimation of sucrose, glucose, fructose of the citrus fruits are major interests of citrus juice industry. A rapid classification and quantification technique was developed and validated for simultaneous and nondestructive quantifying the sugar constituent's concentrations and the origin of citrus fruits using Fourier Transform Near-Infrared (FT-NIR) spectroscopy in conjunction with Artificial Neural Network (ANN) using genetic algorithm, Chemometrics and Correspondences Analysis (CA). To acquire good classification accuracy and to present a wide range of concentration of sucrose, glucose and fructose, we have collected 22 different varieties of citrus fruits from the market during the entire season of citruses. FT-NIR spectra were recorded in the NIR region from 1,100 to 2,500 nm using the fiber optic probe and three types of data analysis were performed. Chemometrics analysis using Partial Least Squares (PLS) was performed in order to determine the concentration of individual sugars. Artificial Neural Network analysis was performed for classification, origin or variety identification of citrus fruits using genetic algorithm. Correspondence analysis was performed in order to visualize the relationship between the citrus fruits. To compute a PLS model based upon the reference values and to validate the developed method, high performance liquid chromatography (HPLC) was performed. Spectral range and the number of PLS factors were optimized for the lowest standard error of calibration (SEC), prediction (SEP) and correlation coefficient (R(2)). The calibration model developed was able to assess the sucrose, glucose and fructose contents in unknown citrus fruit up to an R(2) value of 0.996-0.998. Numbers of factors from F1 to F10 were optimized for correspondence analysis for relationship visualization of citrus fruits based on the output values of genetic algorithm. ANN and CA analysis showed excellent classification of citrus according to the variety to which they belong and well-classified citrus according to their origin. The technique has potential in rapid determination of sugars content and to identify different varieties and origins of citrus in citrus juice industry. 相似文献
304.
A new chelating copolymer (HQDMA) has been synthesized through copolymerization of 8-hydroxyquinoline and dimethylolacetone
monomers in the presence of base as a catalyst. This newly developed copolymer ligand (H2L) has been used to prepare a series of five polymeric chelates (ML) by using Zn(II), Cu(II), Ni(II), Co(II) and Mn(II) metal
ions. Both the parent ligand and its metal chelates have been systemically investigated in detail to elucidate the chemical
structure and thermal behaviour by elemental analyses, spectral (IR and electronic) characterization, number-average molecular
mass determination and thermogravimetric analysis (TG). In addition to these, magnetic susceptibility measurements have also been
carried out for studying geometry and metal-ligand stoichiometry of polymeric chelates.
The chemical structure of polychelates on the basis of elemental and IR characterization suggests that the bidentate ligand
(H2L) coordinates to metal ions through oxygen atom of the phenolic hydroxyl group by replacing hydrogen atom and nitrogen of
the quinoline ring. The studies of magnetic moments and electronic spectra reveal that all polychelates with octahedral geometry
are paramagnetic in nature except that of Zn(II) chelate, which is diamagnetic. The thermogravimetric analysis of parent ligand
and its metal chelates have shown remarkable difference in mode of thermal decomposition and their thermal stabilities. The
kinetic parameter, energy of activation (E
a) of thermal decomposition has also been estimated by Broido method. 相似文献
305.
Goel A Dixit M Chaurasia S Kumar A Raghunandan R Maulik PR Anand RS 《Organic letters》2008,10(12):2553-2556
A novel series of thermally stable blue light emitting quateraryls with a piperidine donor and a nitrile acceptor was prepared from a ketene- S, S-acetal under mild conditions without using an organometal catalyst. The performance of a blue quateraryl 6e was investigated by fabricating a multilayer OLED with a configuration of ITO/PEDOT:PSS (40 nm)/quateraryl (60 nm)/BCP (6 nm)/Alq(3) (20 nm)/LiF (0.5 nm)/Al (200 nm), which exhibited blue emission with a low turn on voltage of 4 V at a brightness of 0.22 cd/m(2). 相似文献
306.
Chandresh L. Jagani Natvar A. Sojitra Satish F. Vanparia Tarosh S. Patel Ritu B. Dixit Bharat C. Dixit 《Journal of Saudi Chemical Society》2012,16(4):363-369
The present paper describes an optimized reaction condition for the microwave promoted synthesis of newer 3-thiazole substituted 2-styryl-4(3H)-quinazolinone derivatives, which in turn were prepared in good yield by the treatment of various 2-styryl benzoxazinone derivatives with various 2-aminothiazoles using co-solvent under microwave irradiation. All the compounds were characterized by various spectroscopic techniques and analytical methods. All newly synthesized compounds have been screened for their in vitro antibacterial and antifungal activities against Escherichia coli, Pseudomonas aeruginosa, Bacillus megaterium,Bacillus subtilis, and Aspergillus niger. 相似文献
307.
Parmar D Matsubara H Price K Spain M Procter DJ 《Journal of the American Chemical Society》2012,134(30):12751-12757
Unsaturated lactones undergo reductive radical cyclizations upon treatment with SmI(2)-H(2)O to give decorated cycloheptanes in a single highly selective operation during which up to three contiguous stereocenters are generated. Furthermore, cascade processes involving lactones bearing two alkenes, an alkene and an alkyne, or an allene and an alkene allow "one-pot" access to biologically significant molecular scaffolds with the construction of up to four contiguous stereocenters. The cyclizations proceed by the trapping of radical anions formed by electron transfer reduction of the lactone carbonyl. 相似文献
308.
309.
Döppner T Thomas CA Divol L Dewald EL Celliers PM Bradley DK Callahan DA Dixit SN Harte JA Glenn SM Haan SW Izumi N Kyrala GA LaCaille G Kline JK Kruer WL Ma T MacKinnon AJ McNaney JM Meezan NB Robey HF Salmonson JD Suter LJ Zimmerman GB Edwards MJ MacGowan BJ Kilkenny JD Lindl JD Van Wonterghem BM Atherton LJ Moses EI Glenzer SH Landen OL 《Physical review letters》2012,108(13):135006
We have imaged hard x-ray (>100 keV) bremsstrahlung emission from energetic electrons slowing in a plastic ablator shell during indirectly driven implosions at the National Ignition Facility. We measure 570 J in electrons with E>100 keV impinging on the fusion capsule under ignition drive conditions. This translates into an acceptable increase in the adiabat α, defined as the ratio of total deuterium-tritium fuel pressure to Fermi pressure, of 3.5%. The hard x-ray observables are consistent with detailed radiative-hydrodynamics simulations, including the sourcing and transport of these high energy electrons. 相似文献
310.
Ankit Kumar Yadav Chandra Prakash Dr. Akhilesh Pandey Prof. Ambesh Dixit 《Chemphyschem》2023,24(21):e202300142
Cu2ZnSnS4 (CZTS) active material-based resistive random-access memory (RRAM) devices are investigated to understand the impact of three different Cu, Ag, and Al top electrodes. The dual resistance switching (RS) behaviour of spin coated CZTS on ITO/Glass is investigated up to 102 cycles. The stability of all the devices (Cu/CZTS/ITO, Ag/CZTS/ITO, and Al/CZTS/ITO) is investigated up to 103 sec in low- (LRS) and high- (HRS) resistance states at 0.2 V read voltage. The endurance up to 102 cycles with 30 msec switching width shows stable write and erase current. Weibull cumulative distribution plots suggest that Ag top electrode is relatively more stable for set and reset state with 33.61 and 25.02 shape factors, respectively. The charge carrier transportation is explained by double logarithmic plots, Schottky emission plots, and band diagrams, substantiating that at lower applied electric field intrinsic copper ions dominate in Cu/CZTS/ITO, whereas, at higher electric filed, top electrodes (Cu and Ag) dominate over intrinsic copper ions. Intrinsic Cu+ in CZTS plays a decisive role in resistive switching with Al electrode. Further, the impedance spectroscopy measurements suggest that Cu+ and Ag+ diffusion is the main source for the resistive switching with Cu and Ag electrodes. 相似文献