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71.
Jinhua Wang Dr. Barbara Wicher Dr. Victor Maurizot Prof. Ivan Huc 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(3):1031-1038
Quinoline based aromatic amide foldamers are known to adopt stable folded conformations. We have developed a synthetic approach to produce similar oligomers where all amide bonds, or part of them, have been replaced by an isosteric vinylene group. The results of solution and solid state structural studies show that oligomers exclusively containing vinylene linkages are not well folded, and adopt predominantly flat conformations. In contrast, a vinylene segment flanked by helical oligoamides also folds in a helix, albeit with a slightly lower curvature. The presence of vinylene functions also result in an extension of π-conjugation across the oligomer that may change charge transport properties. Altogether, these results pave the way to foldamers in which both structural control and specific electronic properties may be engineered. 相似文献
72.
Zbigniew Gregorowicz Barbara Piwowarska Franciszek Buhl und Krystyna Kania 《Fresenius' Journal of Analytical Chemistry》1968,237(5):347-351
Zusammenfassung Es wurde eine UV-spektrophotometrische Methode zur Bestimmung der 2,2-Dicinchoninsäure beschrieben. Messung erfolgt bei pH 10 bei dem Absorptionsmaximum von 260 nm. Der Bestimmungsbereich beträgt 1,71–20,52 g der 2,2-Dicinchonin-Ionen in 25 ml Lösung. Ba2+, Sr2+, Ca2+, Mg2+, Ni2+, Co2+, Zn2+, Hg2+ und Al3+ in 100fachem sowie Pb2+ in 10fachem Überschuß verursachen keine Störungen. Blei in 20 fachem sowie Ag+ und Hg2
2+ in einfachem Überschuß verursachen Ausscheidung von Niederschlägen.
Summary An UV-spectrophotometric method for the determination of 2,2-dicinchonic acid is described. The absorption is measured in a solution of pH 10 at the maximum of 260 nm.The range of application of the method was 1,71 to 20,52 g of DC2– ions in 25 ml of solution. Ba2+, Sr2+, Ca2+, Mg2+, Ni2+, Co2+, Al3+, Zn2+, Hg2+ ions present in hundredfold excess do not interfere with the determination. Ag+, Hg2 2+ ions in one-fold and Pb2+ ion in twenty-fold excess cause the deposition of a precipitate, but five-fold and ten-fold excess of Pb2+ does not interfere.相似文献
73.
Barbara Burnat Tadeusz Blaszczyk Andrzej Leniart 《Journal of Solid State Electrochemistry》2014,18(11):3111-3119
Stainless steel ISO 5832–9 type is often used to perform implants which operate in protein-containing physiological environments. The interaction between proteins and surface of the implant may affect its corrosive properties. The aim of this work was to study the effect of selected serum proteins (albumin and γ-globulins) on the corrosion of ISO 5832–9 alloy (trade name M30NW) which surface was modified by titania coatings. These coatings were obtained by sol–gel method and heated at temperatures of 400 and 800 °C. To evaluate the effect of the proteins, the corrosion tests were performed with and without the addition of proteins with concentration of 1 g L?1 to the physiological saline solution (0.9 % NaCl, pH 7.4) at 37 °C. The tests were carried out within 7 days. The following electrochemical methods were used: open circuit potential, linear polarization resistance, and electrochemical impedance spectroscopy. In addition, surface analysis by optical microscopy and X-ray photoelectron spectroscopy (XPS) method was done at the end of weekly corrosion tests. The results of corrosion tests showed that M30NW alloy both uncoated and modified with titania coatings exhibits a very good corrosion resistance during weekly exposition to corrosion medium. The best corrosion resistance in 0.9 % NaCl solution is shown by alloy samples modified by titania coating annealed at 400 °C. The serum proteins have no significant effect onto corrosion of investigated biomedical steel. The XPS results confirmed the presence of proteins on the alloy surface after 7 days of immersion in protein-containing solutions. 相似文献
74.
Using chiral probes shown to be sensitive to the presence of mobile phase additives, a memory effect for these additives by an amylosic column was demonstrated. Exposure to these additives gave prolonged chromatographic performance changes even after their removal from the mobile phase. This finding is consistent with strong binding of the additives to the stationary phase. A procedure to remove bound additives was developed. 相似文献
75.
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77.
Krzysztof Kurzak Iwona Kuźniarska-Biernacka Barbara Kurzak Julia Jezierska 《Journal of solution chemistry》2001,30(8):709-731
As a part of our general interest in the UV-Vis spectroscopy of multidentate mixed-donor ligands, the (salicylideneethylenediamine)Cu(II) complex has been prepared and characterized by elemental analyses, solubility in common solvents, molar conductivities, and ultraviolet (UV), and visible (Vis) spectroscopy. The combined results of spectrophotometric measurements and EPR spectra, as well as known the X-ray structure for solids, were used to determine the structure of the investigated complex in solutions. The spectra of [Cu(salen)] (H2salen = salicylideneethylenediamine), were measured in various solvents at room temperature, resolved by Gaussian analysis, and angular overlap model (AOM) treated in C
2v symmetry. Because of overparametrization problems, the bis(salicylaldehyde)Cu(II) complex has been characterized and AOM treated. The results of this have been used for AOM studies of [Cu(salen)]. The effect of the solvents upon the - and -bonding ligand abilities is discussed. 相似文献
78.
Nicolas P. Cheval Barbara Hoffmann Anna Dikova Fatih Sirindil Philippe Bertus Aurélien Blanc Jean-Marc Weibel Patrick Pale 《Tetrahedron》2018,74(50):7111-7119
Vinyl nosylates, readily obtained from β-dicarbonyl derivatives, could be efficiently engaged in Sonogashira cross-coupling reactions, either cocatalyzed by copper or silver salts. The para-nitrobenzenesulfonate (nosylate) group allows this coupling to be performed under very mild conditions (room temperature). These new leaving group and mild conditions could be applied to the synthesis of acetylenic coumarinyl derivatives and to the total synthesis of an acetylenic monoterpene natural product, named cleviolide. 相似文献
79.
Barbara Fumić Marijana Zovko Končić Mario Jug 《Journal of inclusion phenomena and macrocyclic chemistry》2018,92(3-4):369-379
A novel sustainable and eco-friendly procedure simultaneously combining the use of ultrasound irradiation and hydroxypropyl-β-cyclodextrin (HPβCD) complexation was used to extract phytochemicals from Lotus corniculatus and to prepare flavonoid rich extract having potential as substrate reduction therapy of mucopolysaccharidosis type III (MPS III), a rare autosomal recessive lysosomal storage disorder. For that instance, Box-Behnken design and response surface methodology was employed to statistically assess the influence of HPβCD concentration, ultrasonic power, and extraction time on the total phenolic compounds, total flavonoids, total phenolic acids and radical scavenging activity (RSA) of the extracts prepared, chosen as the responses indicative of the product quality and performance. The potential of such optimised extract to modulate accumulation of gylcosoaminoglycans (GAGs) was evaluated on the fibroblast obtained from patients suffering from MPS type III. Optimized extract prepared by 45 min extraction using HPβCD at concentration of 20 mM and ultrasonic irradiation of 648 W was rich in flavonoids (1.36 mg/mL) and showed notable RSA of 1.04 mg/mL. Freeze-dried extract, at concentration of 3 and 6 µg/mL, reduced GAG levels in skin fibroblasts by 33.97 and 50.08%, respectively, without any toxic effects at given doses, showing a potential to be considered as a part of the substrate reduction therapy of MPS III. 相似文献
80.
Barbara Franczuk Witold Danikiewicz 《Journal of the American Society for Mass Spectrometry》2018,29(3):588-599
Ion-molecule reactions of Me2S2 with a wide range of aliphatic carbanions differing by structure and proton affinity values have been studied in the gas phase using mass spectrometry techniques and DFT calculations. The analysis of the spectra shows a variety of product ions formed via different reaction mechanisms, depending on the structure and proton affinity of the carbanion. Product ions of thiophilic reaction (m/z 47), SN2 (m/z 79), and E2 elimination – addition sequence of reactions (m/z 93) can be observed. Primary products of thiophilic reaction can undergo subsequent SN2 and proton transfer reactions. Gibbs free energy profiles calculated for experimentally observed reactions using PBE0/6-311+G(2d,p) method show good agreement with experimental results. 相似文献