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101.
Muhammad Asif Hanif Ahmed Yahya Al-Maskari Jamal Nasser Al-Sabahi Ibtisam Al-Hdhrami Muhammad Mumtaz Khan Ahlam Al-Azkawi 《Natural product research》2015,29(24):2332-2335
Medicago sativa Linn growing in Omani desert were chemically characterised using flame photometry, inductively coupled plasma, gas chromatography–mass spectrometry and high performance liquid chromatographic (HPLC) analysis. HPLC analyses were performed to determine the phenolics and flavonoids present in M. sativa. The major compounds detected in M. sativa leaves were protchaechenic acid (3.22%), hydroxyl benzoic acid (1.05%), β-Phenyl caffate (0.97%) and kaempherol (0.89%). Pterostilbene, a cholesterol-lowering compound, was detected in M. sativa. 相似文献
102.
The purpose of this note is to investigate the stabilization of the wave equation with Kelvin–Voigt damping in a bounded domain. Damping is localized via a non-smooth coefficient in a suitable subdomain. We prove a polynomial stability result in any space dimension, provided that the damping region satisfies some geometric conditions. The main novelty of this note is that the geometric situations covered here are richer than that considered in [25], [22], [16] and include in particular an example where the damping region is not localized in a neighborhood of the whole or a part of the boundary. 相似文献
103.
Michele Vascellari Danny Messig Arne Scholtissek Christian Hasse Meng Xia Benoît Fiorina Nasser Darabiha 《Proceedings of the Combustion Institute》2019,37(3):2857-2866
A multi-stream Flamelet Progress Variable (FPV) model, specifically developed for coal combustion, is proposed. The model accounts for the different fuel streams associated with the volatile and char burnout products. The applicability of the new FPV model is investigated in a laminar stagnation pulverized coal flame. The flame considered is a premixed mixture of CH4, O2 and N2, carrying pulverized coal particles, stabilized in an impinging wall. Spontaneous emissions of OH*, CH* and C are measured to identify the flame. The 1D numerical simulations of the experimental conditions are able to reproduce the main features of the flame. The applicability of the multi-stream FPV model to coal combustion is further evaluated with the a posteriori analysis of the FPV results, comparing the results with a reference model, where the species are fully transported and the chemistry directly evaluated. Then, with the budget analysis, the influence of the control variables used to build the look-up table is assessed by examining the conditional contributions to the overall transport terms of scalar quantities (e.g. species, temperature). The results of both analyses show that the proposed multi-stream FPV model can accurately predict the main features of coal combustion, with only minor issues related to the manifold used to build the look-up table. 相似文献
104.
Aboul-Enein Mohamed N. El-Azzouny Aida A. Maklad Yousreya A. Ismail Mohamed A. Ismail Nasser S. M. Hassan Rasha M. 《Research on Chemical Intermediates》2015,41(6):3767-3791
Research on Chemical Intermediates - A series of novel safinamide derivatives were synthesized and biologically evaluated for their anticonvulsant activity against maximal electroshock seizure... 相似文献
105.
106.
Acid/Base‐Triggered Switching of Circularly Polarized Luminescence and Electronic Circular Dichroism in Organic and Organometallic Helicenes
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Nidal Saleh Barry Moore II Monika Srebro Nicolas Vanthuyne Loïc Toupet J. A. Gareth Williams Christian Roussel Kirandeep K. Deol Gilles Muller Jochen Autschbach Jeanne Crassous 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(4):1673-1681
Electronic circular dichroism and circularly polarized luminescence acid/base switching activity has been demonstrated in helicene‐bipyridine proligand 1 a and in its “rollover” cycloplatinated derivative 2 a . Whereas proligand 1 a displays a strong bathochromic shift (>160 nm) of the nonpolarized and circularly polarized luminescence upon protonation, complex 2 a displays slightly stronger emission. This strikingly different behavior between singlet emission in the organic helicene and triplet emission in the organometallic derivative has been rationalized by using quantum‐chemical calculations. The very large bathochromic shift of the emission observed upon protonation of azahelicene‐bipyridine 1 a has been attributed to the decrease in aromaticity (promoting a charge‐transfer‐type transition rather than a π–π* transition) as well as an increase in the HOMO–LUMO character of the transition and stabilization of the LUMO level upon protonation. 相似文献
107.
Ashraf Mahmoud Ahmad Abo Naser Marwan Abu‐Amara Tarek Sheltami Nidal Nasser 《International Journal of Communication Systems》2018,31(1)
The evolved packet core (EPC) network is the mobile network standardized by the 3rd Generation Partnership Project and represents the recent evolution of mobile networks providing high‐speed data rates and on‐demand connectivity services. Software‐defined networking (SDN) is recently gaining momentum in network research as a new generation networking technique. An SDN‐based EPC is expected to introduce gains to the EPC control plane architecture in terms of simplified, and perhaps even software‐based, vendor independent infrastructure nodes. In this paper, we propose a novel SDN‐based EPC architecture along with the protocol‐level detailed implementation and provide a mechanism for identifying information fields exchanged between SDN‐EPC entities that maintains correct functionality with minimal impact on the conventional design. Furthermore, we present the first comprehensive network performance evaluation for the SDN‐based EPC versus the conventional EPC and provide a comparative analysis of 2 networks performances identifying potential bottlenecks and performance issues. The evaluation focuses on 2 network control operations, namely, the S1‐handover and registration operations, taking into account several factors, and assessing performance metrics such as end‐to‐end delay (E2ED) for completion of the respective control operation, and EPC nodes utilization figures. 相似文献
108.
Nafis Mahmud Abdelbaki Benamor Mustafa S. Nasser Paitoon Tontiwachwuthikul 《Journal of solution chemistry》2018,47(2):262-277
The apparent protonation constant of an amino butanol (AB) and its carbamate formation constant in the CO2–H2O–AB system were determined at T = 298.15–328.15 K, and at various ionic strengths up to 0.2 mol·L?1 by potentiometric titration. The Debye–Hückel equation was used to extrapolate the protonation constants to zero ionic strength. The variation of the thermodynamic equilibrium constant for carbamate formation with temperature was modeled according to the relationship of log10 K1 = 280.91/T ? 0.1105, while the temperature dependency of the amine protonation constant was correlated by log10 K2 = 1926.53/T + 2.9482. Van’t Hoff type plots of the pK values showed linear relationships indicating that the standard enthalpy changes of reaction are constant over this range of temperatures. Hence, our current findings are crucial for designing efficient unit operations involving separation of CO2 from natural or flue gases. 相似文献
109.
The chemical reactivity of electron deficient chromone–linked acrylonitrile [3-(6-methylchromonyl)acrylonitrile (1)] was studied towards some active methylene nitriles and active methylene ketones. Reaction of compound 1 with malononitrile, cyanoacetamide, ethyl cyanoacetate, malononitrile dimer and acetoacetanilide afforded 5-cyanomethylchromeno[4,3-b]pyridines 2–4 and 9. Compound 1 reacted with 1H-benzimidazol-2-ylacetonitrile producing pyrido[1,2-a]benzimidazole derivative 5. Benzonitrile derivatives 6–8 were efficiently synthesized from the reaction of compound 1 with acetylacetone, ethyl acetoacetate and diethylmalonate. In these reactions a diversity of products has been synthesized through a domino process, including Michael addition, retro-Michael with γ-pyrone ring opening followed by different types of recyclization (RORC). Structures of the new synthesized products were deduced on the basis of their analytical and spectral data, and the reaction mechanisms are discussed. 相似文献
110.
Mehdi D. Esrafili Hadi Behzadi Nasser L. Hadipour 《Theoretical chemistry accounts》2008,121(3-4):135-146
We investigated geometry, energy, ${\nu_{{\text{N--H}}}}$ harmonic frequencies, 14N nuclear quadrupole coupling tensors, and ${n_{\rm O}\to \sigma _{{\text{N--H}}}^\ast}$ charge transfer properties of (acetamide) n clusters, with n = 1 ? 7, by means of second-order Møller-Plesset perturbation theory (MP2) and DFT method. Dependency of dimer stabilization energies and equilibrium geometries on various levels of theory was examined. B3LYP/6-311++G** calculations revealed that for acetamide clusters, the average hydrogen-bonding energy per monomer increases from ?26.85 kJ mol?1 in dimer to ?35.12 kJ mol?1 in heptamer; i.e., 31% cooperativity enhancement. The n-dependent trend of ${\nu_{{\text{N--H}}}\,{and}\,^{14}}$ N nuclear quadrupole coupling values were reasonably correlated with cooperative effects in ${r_{{\text{N--H}}}}$ bond distance. It was also found that intermolecular ${n_{\rm O}\to \sigma_{{\text{N--H}}}^\ast}$ charge transfer plays a key role in cooperative changes of geometry, binding energy, ${\nu_{{\text{N--H}}}}$ harmonic frequencies, and 14N electric field gradient tensors of acetamide clusters. There is a good linear correlation between 14N quadrupole coupling constants, C Q (14N), and the strength of Fock matrix elements (F ij ). Regarding the ${n_{\rm O}\to \sigma_{{\text{N--H}}}^\ast}$ interaction, the capability of the acetamide clusters for electron localization, at the N–H· · ·O bond critical point, depends on the cluster size and thereby leads to cooperative changes in the N–H· · ·O length and strength, N–H stretching frequencies, and 14N quadrupole coupling tensors. 相似文献