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941.
Jindrich Kynicky Vedran Milosavljevic Pavlina Jelinkova Yazan Haddad Miguel Angel Merlos Rodrigo Hana Buchtelova Zuzana Bytesnikova Martin Brtnicky Lukas Richtera Pavel Kopel Vojtech Adam 《Chemical Papers》2018,72(6):1437-1449
Eu(III) and Tb(III) Schiff base complexes are applicable in various fields such as sensing, assays, screening protocols in vitro, and imaging studies in vitro or in vivo. Fluorescent europium and terbium complexes and their interaction with cell penetrating peptide (KKKRKC) can represent an excellent key for understanding pathway of peptide transportation though cell membrane and the application of Schiff base complexes as potential antibacterial drugs. The Schiff base–metal complexes and its conjugates with peptide were tested for their antibacterial activity against Pseudomonas aeruginosa and Salmonella typhimurium. Schiff base–metal complexes conjugated with peptide show minor toxicity in normal human PNT1A cells and high antibacterial activity against P. aeruginosa and S. typhimurium, where IC50 down to 125.9 and/or 36.1 µM were found for P. aeruginosa and S. typhimurium, respectively. Our results strongly suggest that Schiff base–metal complexes conjugated with peptide have great potential to be developed into highly effective antibacterial drug. 相似文献
942.
Lindomar G. De Sousa José Geraldo M. C. Júnior Rodrigo M. Verly Manoel J. M. Pires Débora V. Franco Leonardo M. Da Silva 《Journal of Solid State Electrochemistry》2018,22(5):1349-1363
A porous anode composed of β-PbO2 was electrochemically deposited onto a carbon cloth substrate (e.g., CC/β-PbO2) aiming for the electrochemical ozone production (EOP) in electrolyte-free water using a solid polymer electrolyte (SPE) filter-press reactor. Scanning electron microscopy (SEM) images revealed the presence of a three-dimensional oxide structure necessary to obtain a fluid-permeable anode. X-ray analysis showed the predominance of the β-PbO2 phase. The maximum current efficiency for the EOP was 9.5% with an ozone production rate of 1.40 g h?1. Using a constant ozone production rate of 0.5 g h?1, the oxidative degradation of paracetamol (PCT) dissolved in water was accomplished as a function of the PCT concentration (20, 30, and 50 mg L?1) and the pH (acid, natural (without adjustment), and alkaline). The UV-Vis spectrophotometric analysis showed that the degradation process is more pronounced in alkaline media with a strong reduction in the electrical energy per order (E EO). A reduction of the chemical oxygen demand (COD) of up to 80% was observed. A linear correlation between data referring to COD and HPLC measurements with the UV absorbance measured at 243 nm (UV243) was verified indicating that these different techniques can be complementary to each other. The nuclear magnetic resonance (NMR) study of the ozonation by-products revealed that the oxidation of PCT occurred through the rupture of the aromatic ring. The major part of phenol’s ring was oxidized to CO3 2? while no reaction occurs in the acetamide group of paracetamol during the ozonation reaction. 相似文献
943.
Maria F. Gazulla M. Jesús Ventura Marta Rodrigo Jéssica Gilabert 《Analytical letters》2018,51(12):1956-1972
Water may be present in clayey materials in different forms (hydration water and structural water), providing different properties to the materials such as reactivity and plasticity, and affecting the industrial processes in which they are involved, resulting in the importance of the determination these types of water. In addition, some clayey materials such as bentonites or sepiolites, present very high avidity for water, which must be considered in the characterization of the materials, and especially in the structural water content determination. In the literature, no rapid and accurate methods for the determination of structural water content in this type of clayey materials are described and validated, so to fill the lack of a methodology for determining structural water, a method by combustion and infrared detection has been established. In the development of the methodology, the sample preparation was the most important step, in which the drying process of the samples had particular relevance. The time and temperature of drying and the maximum time that the samples can be stored in the desiccator before the analysis were evaluated. The development of the measurement method was performed optimizing the conditions and constructing calibration curves. The developed methodology was validated using reference materials. Finally, several clayey materials (sepiolites, bentonites, and kaolin) were analyzed using the developed methodology. The results were compared with those obtained by differential thermal analysis-thermogravimetry (DTA-TG), concluding that the DTA-TG analysis is only useful for the determination of structural water when the materials do not contain carbonates (e.g., calcite, dolomite). 相似文献
944.
Araújo AS da Rocha LL Tomazela DM Sawaya AC Almeida RR Catharino RR Eberlin MN 《The Analyst》2005,130(6):884-889
After just simple degassing, dilution, pH adjustment and direct flow injection, characteristic fingerprint spectra of beer samples have been obtained by fast (few seconds) electrospray ionization mass spectrometry (ESI-MS) analysis in both the negative and positive ion modes. A total of 29 samples belonging to the two main beer types (lagers and ales) and several beer subtypes from USA, Europe and Brazil could be clearly divided into three groups both by simple visual inspection of their ESI(+)-MS and ESI(-)-MS fingerprints as well as by chemometric treatment of the MS data. Diagnostic ions with contrasting relative abundances in both the positive and negative ion modes allow classification of beers into three major types: P = pale (light) colored (pilsener, pale ale), D = dark colored (bock, stout, porter, mild ale) and M = malt beer. For M beers, samples of a dark and artificially sweetened caramel beer produced in Brazil and known as Malzbiers were used. ESI-MS/MS on these diagnostic beer cations and anions, most of which are characterized as arising from ionization of simple sugars, oligosaccharides, and iso-alpha-acids, yield characteristic tandem mass spectra adding a second and optional MS dimension for improved selectivity for beer characterization by fingerprinting. Direct ESI-MS or ESI-MS/MS analysis can therefore provide fast and reliable fingerprinting characterization of beers, distinguishing between types with different chemical compositions. Other unusual polar components, impurities or additives, as well as fermentation defects or degradation products, could eventually be detected, making the technique promising for beer quality control. 相似文献
945.
Rodrigo L.O.R. Cunha Julio Zukerman-Schpector João V. Comasseto 《Journal of organometallic chemistry》2006,691(23):4807-4815
Tellurium tetrachloride adds to alkynes via two pathways: a concerted syn addition, that yields Z-tri- and tetra-substituted alkenes or by an anti addition that yields E-alkenes. The mechanistic aspects of these divergent pathways have been reevaluated at the light of crystallographic data. The molecules, of the title compound, in the crystal, are associated in a helical fashion with a Te…Te pitch of 6.3492(6) Å. As it exhibits inhibitory activity for cathepsin B and in order to gain more insight of the inhibition mechanism, a docking study was undertaken providing insight on why organic telluranes are more efficient inhibitors than inorganic ones as AS-101. 相似文献
946.
Calculations of the 13C NMR chemical shifts for the methoxy and ethoxy groups adsorbed on Y and ZSM-5 zeolites were computed at GIAO/B3LYP/6-31+G*//MM+ level of theory, using a cluster representing a real part of the zeolites. The Y zeolite was represented by a cluster with 168 atoms, while ZSM-5 was represented by a cluster with 144 atoms. The calculated chemical shifts agreed well with reported experimental values, showing that the difference in chemical shifts is associated with differences in the geometry of the alkoxides on the two zeolites. 相似文献
947.
Rodrigo Beltrán-Suito Angela Pinedo-Flores Fabiola Bravo-Hualpa Jorge Ramos-Muñoz 《Journal of Dispersion Science and Technology》2019,40(6):901-908
Water-resistant MOF-235 was used to adsorb N,N-dimethylamine (DMA) from aqueous solutions. It was synthesized from terephthalic acid and FeCl3.6H2O under air-free conditions and characterized by its crystalline structure, functional groups and temperature resistance. The kinetic data results were best adjusted to the pseudo-second order model (R2>0.963). The best-fit isotherm, Langmuir model, suggested the adsorption of DMA is localized on homogenously distributed active sites on the surface. This fit was confirmed by the value of β?=?1 on the Redlich-Peterson model. Our study suggests that the manipulation of novel materials such as MOF-235 promises new avenues for water treatment solutions.
Schematic structure of MOF-235 and its application as adsorbent. 相似文献
948.
The dimethylacetal of benzaldehyde and some 3, 3,4 and 3,4,5 oxygenated derivatives thereof are regiospecifically deprotonated at the 2-position by alkyl lithiums. The resulting aryl lithiums provide various 2-substituted benzaldehydes in moderate to excellent yields. 相似文献
949.
Marcio José Tiera Gerson Rodrigues dos Santos Vera A. de Oliveira Tiera Neide Aparecida Blaz Vieira Elisabete Frolini Rodrigo C. da Silva Watson Loh 《Colloid and polymer science》2005,283(6):662-670
A series of N-isopropylacrylamide (NIPAM)-acrylic acid–ethyl methacrylate terpolymers with varied monomer compositions was prepared by radical polymerization. The solution behavior of these polymers was studied in dilute aqueous solution using spectrophotometry, fluorescence spectroscopy and high-sensitivity differential scanning calorimetry. The results obtained revealed that the lower critical solution temperatures depend strongly on the copolymer composition, solution pH and ionic strength. At a high pH, the ionization of acrylic acid (AA) units leads to an increase in solution cloud points (Tc). Solutions of polymers containing 10% or less of AA display a constant Tc for pH above 5.5, with 15% there is a continuous increase in Tc with pH and, for higher AA contents, no clouding was observed within the studied temperature range. Fluorescence probe studies were conducted by following the I 1/I 3 ratio of pyrene vibronic bands and the emission of anilinonaphtalene sulfonic acid, sodium salt (ANS), both approaches revealing the existence of hydrophobic domains for polymers with higher ethyl methacrylate content at temperatures lower than Tc, suggesting some extent of aggregation and/or a coil-to-globule transition. Scanning calorimetry measurements showed an endothermic transition at temperatures agreeing with the previously detected cloud points. Moreover, the transition curves became broader and with a smaller transition enthalpy, as both the AA content and the solution pH were increased. These broader transitions were interpreted to be the result of a wider molecular distribution upon polymer ionization, hence, displaying varied solution properties. The decrease in transition enthalpy was rationalized as a consequence of reminiscent hydration of NIPAM units, even after phase separation, owing to the presence of electric charges along the polymer chain. 相似文献
950.
J. Manuel López-Romero Rodrigo Rico Jesús Hierrezuelo Chengzhi Cai Isabel López-Tocón 《Tetrahedron letters》2007,48(35):6075-6079
We report an efficient synthesis of a series of penta-p-phenylene derivatives with four side chains of various lengths, including deca(ethylene glycol) groups. The key feature of the synthesis is that the side chains are efficiently introduced in the last step, facilitating optimization of the side chains for different applications. Raman spectroscopy study indicates a similarly high rigidity for all these compounds, even those with long oligo(ethylene glycol) side chains. The deca(ethylene glycol)-substituted penta-p-phenylene derivatives are versatile building blocks for construction of nanometric, tripod-shaped adsorbates for biological applications. 相似文献