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991.
Dr. Ivana Šišoláková Jana Hovancová Frederika Chovancová Prof. Renáta Oriňaková Dr. Iveta Maskaľová Prof. Andrej Oriňak Prof. Jozef Radoňak 《Electroanalysis》2021,33(3):627-634
Screen printed carbon electrodes (SPCEs) modified by a combination of chitosan, multi walled carbon nanotubes (MWCNTs) and zinc nanoparticles (ZnNPs) were studied for the first time as a suitable candidate for non-enzymatic insulin determination. In an effort to find the most suitable modification for electrochemical insulin determination, the stability, analytical characteristics, and selectivity were determined. The results confirmed that the ZnNPs/chitosan-MWCNTs prepared with the Zn deposition time of 45 s displayed the best electrocatalytic activity towards insulin oxidation in a wide linear concentration range (0.5 μM to 5 μM), with low limit of detection and high sensitivity. 相似文献
992.
The unsteady laminar magnetohydrodynamics(MHD) boundary layer flow and heat transfer of nanofluids over an accelerating convectively heated stretching sheet are numerically studied in the presence of a transverse magnetic field with heat source/sink. The unsteady governing equations are solved by a shooting method with the Runge-KuttaFehlberg scheme. Three different types of water based nanofluids, containing copper, aluminium oxide, and titanium dioxide, are taken into consideration. The effects of the pertinent parameters on the fluid velocity, the temperature, the entropy generation number, the Bejan number, the shear stress, and the heat transfer rate at the sheet surface are graphically and quantitatively discussed in detail. A comparison of the entropy generation due to the heat transfer and the fluid friction is made with the help of the Bejan number. It is observed that the presence of the metallic nanoparticles creates more entropy in the nanofluid flow than in the regular fluid flow. 相似文献
993.
This paper describes a prey?Cpredator fishery system with prey dispersal in a two-patch environment, one of which is a free fishing zone and the other a protected zone. The proposed system reflects the dynamic interaction between the net economic revenue and the fishing effort used to harvest the population in presence of a suitable tax. Local as well as global stability of the system is analyzed. The optimal taxation policy is formulated and solved with the help of Pontryagin??s maximal principle. The objective of the paper is to achieve the sustainability of the fishery, keeping the ecological balance, and maximize the monetary social benefit. The dynamical behavior of the delay system is further analyzed through incorporating discrete type gestational delay of predators, and the existence of Hopf bifurcation phenomenon is checked at the interior equilibrium point. Moreover, we use normal form method and center manifold theorem to examine the nature of the Hopf bifurcation. Theoretical results are verified with the help of numerical examples and graphical illustrations. 相似文献
994.
Jana Sopkov‐de Oliveira Santos Alexandre Bouillon Jean‐Charles Lancelot Sylvain Rault 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(8):o582-o584
The crystal structure of the first reported non‐substituted N‐methyldioxazaborocane confirms that the presence of a methyl group attached to the N atom introduces an NB bond length that is longer than that in a simple dioxazaborocane ring. The presence of more N atoms in the vicinity of the B atom in the title compound [systematic name: 6a‐(6‐bromopyridin‐2‐yl)‐3a‐methyl‐2,3,4,5‐tetrahydro‐1,6‐dioxa‐3a‐aza‐6a‐borapentalene], C10H14BBrN2O2, does not modify significantly any structural parameter in the dioxazaborocane ring. On the other hand, a small asymmetry appears in the bond angles of the pyridine C atom next to the B atom. 相似文献
995.
Aura Tintaru Laurence Charles Petr Milko Jana Roithová Detlef Schr?der 《Journal of Physical Organic Chemistry》2009,22(3):229-233
The complexation of copper(II) to acridine derivatives has been studied by means of electrospray ionization (ESI) mass spectrometry. Under soft conditions of ionization, the ESI mass spectra of methanolic solutions of copper(II) chloride and the acridine ligands show abundant signals of the mononuclear complexes formed from the metal and ligand. Depending on the position of the N‐benzoylamino substituent in the acridinic heterocycle, however, the copper atom involved in the complexation process adopts different oxidation states in the resulting cations. Hence, the metal is reduced to copper(I) in the monocationic complex with the compound substituted in position 2, whereas it keeps its divalent state in the monocation formed with the compound substituted in position 4. As a consequence, the regioisomers lead to monocations with different masses in the ESI spectra. In order to understand this unusual behavior of two isomeric compounds, additional experiments have been performed with quinoline as a model. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
996.
997.
Jana Krenkova Andrea Gargano Nathan A. Lacher Jeffrey M. Schneiderheinze Frantisek Svec 《Journal of chromatography. A》2009,1216(40):6824-6830
Poly(glycidyl methacrylate-co-ethylene methacrylate) monoliths have been prepared in 100 μm i.d. capillaries and their epoxy groups hydrolyzed to obtain poly(2,3-dihydroxypropyl methacrylate-co-ethylene methacrylate) matrix. These polymers were then photografted in a single step with 2-acrylamido-2-methyl-1-propanesulfonic acid and acrylic acid to afford stationary phases for a strong and a weak cation exchange chromatography, respectively. Alternatively, poly(ethylene glycol) methacrylate was used for grafting in the first step in order to enhance hydrophilicity of the support followed by photografting with 2-acrylamido-2-methyl-1-propanesulfonic acid or acrylic acid in the second step. These new columns were used for the separation of proteins and peptides. A mixture of ovalbumin, α-chymotrypsinogen, cytochrome c, ribonuclease A and lysozyme was used to assess the chromatographic performance for large molecules while a cytochrome c digest served as a model mixture of peptides. All tested columns featured excellent mass transfer as demonstrated with very steep breakthrough curves. The highest binding capacities were found for columns prepared using the two step functionalization. Columns with sulfonic acid functionalities adsorbed up to 21.5 mg/mL lysozyme while the capacity of the weak cation exchange column functionalized with acrylic acid was 29.2 mg/mL. 相似文献
998.
A novel universal aerosol-based detector Nano Quantity Analyte Detector – NQAD™, connected with an ultra-performance liquid chromatography system is described. The detector was employed for detection of selected antibiotic compounds – macrolides (oleandomycin, erythromycin, troleandomycin, clarithromycin and roxithromycin) that are hard to detect using classical UV detectors due to the lack of chromophores. The determined lowest detection limits under isocratic conditions for these compounds ranged from 3.0 to 5.4 μg/mL. The suitability of the detector connected with ultra high-performance liquid chromatography in the gradient mode was tested on a more complex mixture containing 12 antibiotics. The detector exhibited full compatibility under both the elution modes when UHPLC separations were achieved in relatively short run times. 相似文献
999.
Rajendra M. Srivastava Maria C. Pereira Wagner W. M. Faustino Kaline Coutinho Janaína V. dos Anjos Sebasti?o J. de Melo 《Monatshefte für Chemie / Chemical Monthly》2009,15(2):1319-1324
Abstract
A simple and easy synthesis of ten arylamidoximes from arylnitriles and hydroxylamine is described. The formation of the arylamides has been observed to a much lesser extent in the present work. A new mechanism for the formation of arylamidoximes, as well as arylamides, from arylnitriles and hydroxylamine is suggested. Quantum mechanical calculations have been carried out to support this mechanism. The enthalpy of formation in conjunction with atomic charges of the reactants and intermediates helped to understand more about the generation of the products. 相似文献1000.
Višnja Vrdoljak Prof. Dalibor Milić Marina Cindrić Dubravka Matković‐Čalogović Jana Pisk Marina Marković Predrag Novak 《无机化学与普通化学杂志》2009,635(8):1242-1248
New dinuclear pentacoordinate molybdenum(V) complexes, [Mo2VO3L2] [L = thiosemicarbazonato ligand: C6H4(O)CH:NN:C(S)NHR′ and C10H6(O)CH:NN:C(S)NHR′; R′ = H, CH3, C6H5) were obtained either by oxygen atom abstraction from MoVIO2L with triphenylphosphine or by using [Mo2O3(acac)4] in the reaction with the corresponding ligands H2L. Crystal and molecular structure of [Mo2O3{C6H4(O)CH:NN:C(S)NHC6H5}2] · CH3CN has been determined by the single‐crystal X‐ray diffraction method. 相似文献