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排序方式: 共有389条查询结果,搜索用时 15 毫秒
81.
82.
Karel Cizek Jiri Barek Jan Fischer Karolina Peckova Jiri Zima 《Electroanalysis》2007,19(12):1295-1299
The voltammetric behavior of 3‐nitrofluoranthene and 3‐aminofluoranthene was investigated in mixed methanol‐water solutions by differential pulse voltammetry (DPV) at boron doped diamond thin‐film electrode (BDDE). Optimum conditions have been found for determination of 3‐nitrofluoranthene in the concentration range of 2×10?8–1×10?6 mol L?1, and for determination 3‐aminofluorathnene in the concentration range of 2×10?7–1×10?5 mol L?1, respectively. Limits of determination were 3×10?8 mol L?1 (3‐nitrofluoranthene) and 2×10?7 mol L?1 (3‐aminofluoranthene). 相似文献
83.
Determination of thermodynamic properties of isotactic poly(1-butene) at infinite dilution using density and inverse gas chromatography 总被引:2,自引:0,他引:2
The partial molar volumes, V1(M), and the molar volume of isotactic crystalline low-molecular-weight poly(1-butene), iPBu-1, V1, have been calculated from the measured density of {iPBu-1 + solvent (n-hexane, n-heptane, n-nonane, n-decane, p-xylene, cyclohexane and chloroform)} systems. Some of the thermodynamic quantities were also obtained for the iPBu-1 with eight hydrocarbons (n-octane, n-decane, n-undecane, n-dodecane, n-tridecane, o-xylene, m-xylene, p-xylene) by the method of inverse gas chromatography at various temperatures. The weight fraction activity coefficients of the solvent at infinite dilution, omega2(infinity) and the Flory-Huggins thermodynamic interaction parameters, chi21(infinity), between polymer and solvents were determined. The partial molar free energy, deltaG2(infinity), the partial molar heat of mixing, deltaH2(infinity), at infinite dilution and the polymer solubility parameter, delta1, were calculated. Additionally, the (solid + liquid) binary mixtures equilibria, SLE, of iPBu-1 with three hydrocarbons (n-octane, n-decane and m-xylene) were studied by a dynamic method. By performing these experiments over a large concentration range, the T-x phase diagrams of the polymer-solvent systems were constructed. The excess Gibbs energy models were used to describe the nonideal behaviour of the liquid phase. The omega2(infinity) were determined from the solubility measurements and were predicted by using the UNIFAC FV model. 相似文献
84.
Michal Gacki Karolina Kafarska Wojciech M. Wolf 《Journal of Coordination Chemistry》2019,72(22-24):3481-3494
AbstractA cobalt(II) complex with empirical formula [Co(dicl)2·(H2O)3]·MeOH (where dicl?=?diclofenac) was synthesized and characterized by elemental analysis, flame atomic absorption spectroscopy (FAAS), infrared spectroscopy (FTIR) and thermal decomposition techniques (TGA). The crystal structure of the complex was determined by single crystal X-ray diffraction technique. The compound crystallizes in the monoclinic space group I2/a. Apical water molecules link adjacent cobalt(II) ions forming polymeric chains along the crystal a axis. The thermal behavior of the complex was studied by TG/DTG/DTA, TG/MS and TG/FTIR methods under non-isothermal conditions in air. Upon heating [Co(dicl)2·(H2O)3]·MeOH decomposes progressively to metal oxides, which are the final products of pyrolysis. Furthermore, antioxidant activity of the complex was examined. 相似文献
85.
The effect of polyelectrolyte chain length on layer-by-layer protein/polyelectrolyte assembly--an experimental study 总被引:2,自引:0,他引:2
The effect of polyelectrolyte chain length on the formation of multilayered assemblies of alternating globular proteins and linear polyanions prepared by the layer-by-layer electrostatic adsorption technique was investigated. The systems studied were albumin/sodium poly(styrenesulfonate), immunoglobulin G/sodium poly(styrenesulfonate), albumin/sodium dextran sulfate, and albumin/heparin. The formation of assemblies was followed using FTIR multiple internal reflection spectroscopy. While the amount of polyelectrolyte adsorbed on the first (primary) protein layer did not depend on its molecular weight, the effect of polyelectrolyte chain length was clearly observed in the following steps of alternating adsorption. Some short-chain polyanion molecules were removed from the surface when a next protein layer was adsorbed from solution. The short polyanion chains were not able to make a sufficient number of ion pairs for stable interaction with additional protein molecules and left the surface as soluble protein/polyanion complexes. The most pronounced effect could be seen with sodium poly(styrenesulfonate) of Mw up to ca. 2 x 10(4), but a detectable effect could be traced even up to Mw ca. 8 x 10(4). Such a pronounced effect, however, was not observed with dextran sulfate. The effect of molecular weight of heparin was clearly observed but all heparins tested, regardless of their molecular weight, effectively assembled with albumin to form multilayer. 相似文献
86.
Uwe Kolitsch Karolina Schwendtner 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(3):i17-i20
The crystal structure of hydrothermally synthesized caesium aluminium bis[dihydrogen arsenate(V)] hydrogen arsenate(V), CsAl(H2AsO4)2(HAsO4), was determined from single‐crystal X‐ray diffraction data collected at room temperature. The compound represents a new structure type that is characterized by decorated kröhnkite‐like [100] chains of corner‐sharing AlO6 octahedra and AsO4 tetrahedra. Ten‐coordinated Cs atoms are situated between the chains, which are interconnected by five different hydrogen bonds [O⋯O = 2.569 (4)–2.978 (4) Å]. All atoms are in general positions. CsAl(H2AsO4)2(HAsO4) is very closely related to CsGa(H1.5AsO4)2(H2AsO4) and isotypic CsCr(H1.5AsO4)2(H2AsO4). 相似文献
87.
Karolina Wahlström 《Tetrahedron letters》2009,50(24):2976-5879
The indole nucleus of Z-Trp-OBzl is modified by acylation of the indole nitrogen using Boc-N-methyl butyric acid followed by catalytic hydrogenation and introduction of the Fmoc group. The resulting derivative, Fmoc-Trp(Boc-Nmbu)-OH, is incorporated into peptide chains via solid-phase peptide synthesis (SPPS). After assembly of the peptide chain, the Boc group is cleaved by treatment with TFA. The peptide is isolated with the tryptophan residue modified with a cationic 4-(N-methylamino) butanoyl group, which improves the solubility of the peptide during HPLC purification. On treatment of the purified peptide at pH 9.5, the Nmbu group undergoes an intramolecular cyclization reaction; this results in the fully deprotected peptide and N-methylpyrrolidone. 相似文献
88.
Aleksandra Kawczyk-Krupka Dorota Bartusik-Aebisher Wojciech Latos Grzegorz Cieślar Karolina Sieroń Sebastian Kwiatek Piotr Oleś Beata Kwiatek David Aebisher Magdalena Krupka Rafał Wiench Dariusz Skaba Marcin Olek Jacek Kasperski Zenon Czuba Aleksander Sieroń 《Photochemistry and photobiology》2020,96(3):539-549
The purpose of this review is to present an overview of the development of photodiagnostic and photodynamic therapy (PDD and PDT) techniques in Poland. The paper discusses the principles of PDD, including fluorescent techniques in determining precancerous conditions and cancers of the skin, digestive tract, bladder and respiratory tract. Methods of PDT of cancer will be discussed and the current state of knowledge as well as future trends in the development of photodynamic techniques will be presented, including the possibility of using photodynamic antimicrobial therapy. Research pioneers in photodynamic medicine such as Thomas Dougherty are an inspiration for the development of methods of PDD and PDT in our Clinic. The Center for Laser Diagnostics and Therapy in Bytom, Poland, promotes the propagation of PDD and PDT through the training of clinicians and raising awareness among students in training and the general public. Physicians at the Center are engaged in photomedical research aimed at clinical implementation and exploration of new avenues in photomedicine while optimizing existing modalities. The Center promotes dissemination of clinical results from a wide range of topics in PDD and PDT and serving as representative authorities of photodynamic medicine in Poland and Europe. 相似文献
89.
Karolina Strakova Dr. Amalia I. Poblador-Bahamonde Dr. Naomi Sakai Prof. Stefan Matile 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(65):14935-14942
To image the membrane tension in living cells, planarizable push–pull probes have been introduced. The first operational probe is built around two dithieno[3,2-b:2′,3′-d]thiophenes (DTTs) that are twisted out of co-planarity and polarized with donors and acceptors at either end. In this report, the chemical space available for the twisting of “flipper probes” is assessed comprehensively. The result is, not surprisingly, that every atom matters: Removal of one methyl group in the twist region yields probes that planarize already in solution and are thus less sensitive to membrane tension. Addition of one or more carbons in the same region hinders non-interfering probe alignment along lipid tails and thus partitioning into lipid bilayer membranes as well as mechanosensitivity. However, substitution of one methyl by an isosteric trifluoromethyl group in the twist region, achieved by quite substantial multistep organic synthesis, yields excitation maxima that shift over +100 nm to the red in response to increasing order of the surrounding membrane. This record redshift comes with record changes in fluorescence intensity and lifetime, high push–pull transition dipoles and higher rotational barriers. Supported by distinct dependence on viscosity and twist of the push–pull probes, kinetic competition between dark, fully twisted and bright, fully planarized relaxed excited states emerges as unifying origin of fluorescence quantum yields. 相似文献
90.
Rafał Pelka Karolina Kiełbasa Walerian Arabczyk 《Central European Journal of Chemistry》2011,9(2):240-244
Iron catalyst for ammonia synthesis of various mean sizes of iron nanocrystallites were nitrided with ammonia in a differential
reactor equipped with systems that made it possible to conduct both thermogravimetric measurements and hydrogen concentration
analyses in the reacting gas mixture. The nitriding process was investigated under atmospheric pressure at the temperature
of 475°C. It was found that along with an increase of mean size of iron nanocrystallites, with a decrease of specific surface
area of the samples, nitriding degree of solid samples increased. At the same time the rate of surface reaction of catalytic
ammonia decomposition decreased. Along with an increase of the samples’ specific surface area an increase of the catalyst’s
activity was observed. However, it was also observed that the concentration of active sites on the catalysts’ surface decreased
along with an increase of specific surface area. 相似文献