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101.
Chandra Shekhar Nishad Anirban Chandra Timir Karmakar G. P. Raja Sekhar 《Meccanica》2018,53(9):2333-2352
In this study, we develop a non-primitive boundary integral equation (BIE) method for steady two-dimensional flows of an incompressible Newtonian fluids through porous medium. We assume that the porous medium is isotropic and homogeneous, and use Brinkman equation to model the fluid flow. First, we present BIE method for 2D Brinkman equation in terms of the non-primitive variables namely, stream-function and vorticity variables. Subsequently, a test problem namely, the lid-driven porous cavity over a unit square domain is presented to assert the accuracy of our BEM code. Finally, we discuss an application of our proposed method to flows through porous wavy channel, which is a problem of significant interest in the micro-fluidics, biological domains and groundwater flows. We observe that the rate of convergence (\(R_{c}\)) increases with increasing Darcy number. For low Darcy number streamlines follow the curvature of the wavy-walled channel and no circulation occurs irrespective of the wave–amplitude, while for high Darcy number the flow circulation occurs near the crest of the wavy-walled channel, when the wave–amplitude is large enough. 相似文献
102.
Manish Shinde Amol Pawar Soumen Karmakar Tanay Seth Varsha Raut Sunit Rane Sudha Bhoraskar Dinesh Amalnerkar 《Journal of nanoparticle research》2009,11(8):2043-2047
Uncapped silver nanoparticles were synthesized by DC arc thermal plasma technique. The synthesized nanoparticles were structurally
cubic and showed wide particle size variation (between 20–150 nm). Thick film paste formulated from such uncapped silver nanoparticles
was screen-printed on alumina substrates and the resultant ‘green’ films were fired at different firing temperatures. The
films fired at 600 °C revealed better microstructure properties and also yielded the lowest value of sheet resistance in comparison
to those corresponding to conventional peak firing temperature of 850 °C. Our findings directly support the role of silver
nanoparticles in substantially depressing the operative peak firing temperature involved in traditional conductor thick films
technology. 相似文献
103.
104.
An unprecedented facile oxidation of 1,3,5-trisubstituted pyrazolines and Hantzsch 1,4-dihydropyridines (DHPs) to the corresponding pyrazoles and pyridines was observed, mediated by 3,4-dihydro-2H-pyran in air. The reaction showed excellent reactivity, functional group tolerance, and high yield without using any metal and/or halogen based oxidizing agents. 相似文献
105.
Kinetics of Stripping Ni(II) from the Ni‐BTMPPA Complex/BTMPPA/Kerosene System by Sulfate‐Acetato Solution
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The kinetics of stripping of Ni2+ from a Ni‐BTMPPA complex, dissolved in a kerosene solution of BTMPPA (H2A2, Cyanex 272), by acidic sulfate‐acetato solution, was studied using the single (falling) drop technique and flux (F) method of data treatment. The empirical flux equation at 303 K is Fb (kmol/m2s) = 10?4.35 [Ni2+] (1+10?3.42 [H+]?1)?1 ([H2A2](o)0.5+2.50 [H2A2](o))?1 (1+6[SO42?]) (1+3.20 [Ac?]). Activation energy (Ea), entropy change in activation (ΔS±), and enthalpy change in activation (ΔH±) were measured under different experimental conditions. Based on the empirical flux equation, Ea and ΔS±, the mechanism of Ni2+ stripping is provided. In a low [H+] region, the stripping reaction steps appear as [NiA+] → Ni2+ + A? and [Ni(HA2)2](int) → [NiHA2]+(int) + HA2(int)? in lower and higher concentration regions of free BTMPPA, respectively, provided [SO42?] and [Ac?] are kept low. However, at higher [H+] concentrations, the stripping is under diffusion control. With increasing [SO42?] and [Ac?], the enhancement of the rate is attributed to the attack of the Ni(II) complex by SO42? or HSO4? and Ac? to form NiSO4 or NiHSO4+ and NiAc+ complexes. Negative ΔS± values indicate that the rate‐determining stripping reaction steps occur via an substitution nucleophilic, bimolecular (SN2) mechanism. 相似文献
106.
107.
Ruma?Karmakar Chirantan?Roy?Choudhury Andrei?S.?Batsanov Stuart?R.?Batten Samiran?MitraEmail author 《Structural chemistry》2005,16(5):535-539
Two new complexes [CuBr(C11H13N2O)] (1) and [Cu(NCO)(C11H13N2O)] (2) containing the tridentate Schiff base ligand, N-(1-acetyl-2-propylidene)(2-pyridylmethyl) amine which is the 1:1 condensation product of acetylacetone and 2-aminomethylpyridine, have been synthesised and characterised by elemental analysis, IR and electronic spectra, electrochemical study and single crystal X-ray diffraction study. Crystal structures reveal that the copper atom in both the complexes are in square geometry formed by the N2O donor set of the Schiff base and a bromine atom in 1 and one cyanate ligand in 2. Both bromide and isocyanate ligands act in a terminal monodentate fashion. 相似文献
108.
Hydrogen‐Bonded Organic Frameworks (HOFs): A New Class of Porous Crystalline Proton‐Conducting Materials
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Avishek Karmakar Rajith Illathvalappil Bihag Anothumakkool Arunabha Sen Partha Samanta Aamod V. Desai Dr. Sreekumar Kurungot Dr. Sujit K. Ghosh 《Angewandte Chemie (International ed. in English)》2016,55(36):10667-10671
Two porous hydrogen‐bonded organic frameworks (HOFs) based on arene sulfonates and guanidinium ions are reported. As a result of the presence of ionic backbones appended with protonic source, the compounds exhibit ultra‐high proton conduction values (σ) 0.75× 10?2 S cm?1 and 1.8×10?2 S cm?1 under humidified conditions. Also, they have very low activation energy values and the highest proton conductivity at ambient conditions (low humidity and at moderate temperature) among porous crystalline materials, such as metal–organic frameworks (MOFs) and covalent organic frameworks (COFs). These values are not only comparable to the conventionally used proton exchange membranes, such as Nafion used in fuel cell technologies, but is also the highest value reported in organic‐based porous architectures. Notably, this report inaugurates the usage of crystalline hydrogen‐bonded porous organic frameworks as solid‐state proton conducting materials. 相似文献
109.
Sandeep Mohanty Amrendra Kumar Roy Sandeep Reddy Kuchipudi Pavithran Vinay Kumar Arun Chandra Karmakar 《Phosphorus, sulfur, and silicon and the related elements》2016,191(6):857-866
We investigated the POCl3-mediated transformation of aromatic bisulfite adducts to the corresponding 5-arylidenethiazolidine-2,4-diones. The in situ transformation of an aromatic bisulfite adduct to the parent aldehyde in a non-aqueous non-polar solvent (toluene) was demonstrated using DoE (Design of experiment), offline 1H NMR, online ReactIR, HPLC, LC-MS, and GC-MS. By means of these analytical tools, we determined, for the first time, the structure of the intermediate species (aldehyde) prior to the carbon–carbon double-bond formation. The carbon–sulfur bond undergoes a fast cleavage, immediately after the addition of POCl3, which finally affords the corresponding 5-arylidenethiazolidine-2,4-diones. 相似文献
110.
Bimodal Functionality in a Porous Covalent Triazine Framework by Rational Integration of an Electron‐Rich and ‐Deficient Pore Surface
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Avishek Karmakar Amrit Kumar Abhijeet K. Chaudhari Partha Samanta Aamod V. Desai Rajamani Krishna Dr. Sujit K. Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(14):4931-4937
A porous covalent triazine framework (CTF) consisting of both an electron‐deficient central triazine core and electron‐rich aromatic building blocks is reported. Taking advantage of the dual nature of the pore surface, bimodal functionality has been achieved. The electron deficiency in the central core has been utilized to address one of the pertinent problems in chemical industries, namely separation of benzene from its cyclic saturated congener, that is, cyclohexane. Also, by virtue of the electron‐rich aromatic rings with Lewis basic sites, aqueous‐phase chemical sensing of a nitroaromatic compound of highly explosive nature (2,4,6‐trinitrophenol; TNP) has been achieved. The present compound supersedes the performance of previously reported COFs in both the aspects. Notably, this reports the first example of pore‐surface engineering leading to bimodal functionality in CTFs. 相似文献