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931.
Claudio E. Grünenfelder Dr. Jessica K. Kisunzu Prof. Dr. Helma Wennemers 《Angewandte Chemie (International ed. in English)》2016,55(30):8571-8574
The tripeptide H‐d Pro‐Pro‐Asn‐NH2 is presented as a catalyst for asymmetric conjugate addition reactions of aldehydes to maleimide. The peptidic catalyst promotes the reaction between various aldehydes and unprotected maleimide with high stereoselectivities and yields. The obtained products were readily derivatized to the corresponding pyrrolidines, lactams, lactones, and peptide‐like compounds. 1H NMR spectroscopic, crystallographic, and computational investigations provided insight into the conformational properties of H‐d Pro‐Pro‐Asn‐NH2 and revealed the importance of hydrogen bonding between the peptide and maleimide for catalyzing the stereoselective C?C bond formation. 相似文献
932.
Electrocatalytic Nanostructured Ferric Tannates: Characterization and Application of a Polyphenol Nanosensor
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Dr. Massimiliano Magro Dr. Emanuela Bonaiuto Dr. Davide Baratella Dr. Jessica de Almeida Roger Dr. Petr Jakubec Vittorino Corraducci Dr. Jiri Tuček Dr. Ondrej Malina Prof. Radek Zbořil Prof. Fabio Vianello 《Chemphyschem》2016,17(20):3196-3203
A novel core–shell hybrid nanomaterial composed of peculiar maghemite nanoparticles (surface‐active maghemite nanoparticles (SAMNs)) as the core and tannic acid (TA) as the shell was developed by self‐assembly of ferric tannates onto the surface of SAMNs by simple incubation in water. The hybrid nanomaterial (SAMN@TA) was characterized by using UV/Vis, FTIR, and Mössbauer spectroscopies, magnetization measurements, and X‐ray powder diffraction, which provide evidence of a drastic reorganization of the iron oxide surface upon reaction with TA and the formation of an outer shell that consists of a cross‐linked network of ferric tannates. According to a Langmuir isotherm analysis, SAMN@TA offers one of most stable iron complexes of TA reported in the literature to date. Moreover, SAMN@TA was characterized by using electrical impedance spectroscopy, voltammetry, and chronoamperometry. The nanostructured ferric tannate interface showed improved conductivity and selective electrocatalytic activity toward the oxidation of polyphenols. Finally, a carbon‐paste electrode modified with SAMN@TA was used for the determination of polyphenols in blueberry extracts by square‐wave voltammetry. 相似文献
933.
Michael S. Roberts Nicholas S. Selvo Jessica K. Roberts Vinay M. Daryani Thandranese S. Owens K. Elaine Harstead 《液相色谱法及相关技术杂志》2016,39(16):745-751
A rapid and robust method for measuring methotrexate (MTX) and its two primary metabolites, 7-hydroxymethotrexate (7-OHMTX) and 2,4-diamino-N10-methylpteroic acid (DAMPA), was developed for use in pharmacokinetic studies of plasma and cerebrospinal fluid samples collected from infants with malignant brain tumors. Sample aliquots (100?µL) were prepared for bioanalysis of MTX and metabolites using a Waters Oasis HLB microelution solid-phase extraction (SPE) plate. Chromatography was performed using a Phenomenex Synergi Polar-RP 4 µ 75?×?2.0?mm ID column heated to 40°C. A rapid gradient elution on a Shimadzu HPLC system was used, with mobile phase A consisting of water/formic acid (100/0.1?v/v) and mobile phase B consisting of acetonitrile/formic acid (100/0.1?v/v). Column eluent was analyzed using AB Sciex QTRAP 5500 instrumentation in electrospray ionization mode. The ion transitions (m/z) monitored were 455.2?→?308.1, 471.1?→?324.1, and 326.2?→?175.1 for MTX, 7-OHMTX, and DAMPA, respectively. The method was linear over 0.0022–5.5?µM for MTX, 0.0085–21?µM for 7-OHMTX, and 0.0031–7.7?µM for DAMPA. The method was applied to the analysis of serial plasma samples obtained from infants diagnosed with malignant brain tumors receiving high-dose methotrexate and results were compared to MTX concentrations from an immunoassay based on fluorescence polarization. 相似文献
934.
Synthesis and Photoluminescence Properties of the Red‐Emitting Phosphor Mg3(BN2)N Doped with Eu2+
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Jessica Schölch Tobias Dierkes David Enseling Markus Ströbele Thomas Jüstel H.‐Jürgen Meyer 《无机化学与普通化学杂志》2015,641(5):803-808
Mg3(BN2)N was prepared by solid state metathesis reactions and several europium (Eu2+) doped samples were prepared to discover novel red‐emitting photoluminescent (PL) materials. It turned out that the undoped and doped samples showed very broad deep‐red photoluminescence ranging from about 500 nm into the near infrared. Due to the similar spectra of the undoped and doped samples and unusually high FWHM values of about 5780 cm–1 we conclude that the luminescence process originates from defect sites. This was confirmed by decay measurements which show that the decay constants for all samples were in the range of several milliseconds. 相似文献
935.
Syntheses and Crystal Structures of BaAgTbS3, BaCuGdTe3, BaCuTbTe3, BaAgTbTe3, and CsAgUTe3
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Five new quaternary chalcogenides of the 1113 family, namely BaAgTbS3, BaCuGdTe3, BaCuTbTe3, BaAgTbTe3, and CsAgUTe3, were synthesized by the reactions of the elements at 1173–1273 K. For CsAgUTe3 CsCl flux was used. Their crystal structures were determined by single‐crystal X‐ray diffraction studies. The sulfide BaAgTbS3 crystallizes in the BaAgErS3 structure type in the monoclinic space group C3,2h‐C2/m, whereas the tellurides BaCuGdTe3, BaCuTbTe3, BaAgTbTe3, and CsAgUTe3 crystallize in the KCuZrS3 structure type in the orthorhombic space group D1,27,h‐Cmcm. The BaAgTbS3 structure consists of edge‐sharing [TbS69–] octahedra and [AgS59–] trigonal pyramids. The connectivity of these polyhedra creates channels that are occupied by Ba atoms. The telluride structure features 2∞[MLnTe32–] layers for BaCuGdTe3, BaCuTbTe3, BaAgTbTe3, and 2∞[AgUTe31–] layers for CsAgUTe3. These layers comprise [MTe4] tetrahedra and [LnTe6] or [UTe6] octahedra. Ba or Cs atoms separate these layers. As there are no short Q ··· Q (Q = S or Te) interactions these compounds achieve charge balance as Ba2+M+Ln3+(Q2–)3 (Q = S and Te) and Cs+Ag+U4+(Te2–)3. 相似文献
936.
Novel Composite Plastics Containing Silver(I) Acylpyrazolonato Additives Display Potent Antimicrobial Activity by Contact
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Prof. Fabio Marchetti Dr. Jessica Palmucci Prof. Claudio Pettinari Dr. Riccardo Pettinari Dr. Francesca Condello Dr. Stefano Ferraro Dr. Mirko Marangoni Prof. Alessandra Crispini Dr. Stefania Scuri Prof. Iolanda Grappasonni Prof. Mario Cocchioni Dr. Massimo Nabissi Dr. Michele R. Chierotti Prof. Roberto Gobetto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):836-850
New silver(I) acylpyrazolonato derivatives displaying a mononuclear, polynuclear, or ionic nature, as a function of the ancillary azole ligands used in the synthesis, have been fully characterized by thermal analysis, solution NMR spectroscopy, solid‐state IR and NMR spectroscopies, and X‐ray diffraction techniques. These derivatives have been embedded in polyethylene (PE) matrix, and the antimicrobial activity of the composite materials has been tested against three bacterial strains (E. coli, P. aeruginosa, and S. aureus): Most of the composites show antimicrobial action comparable to PE embedded with AgNO3. Tests by contact and release tests for specific migration of silver from PE composites clearly indicate that, at least in the case of the PE, for composites containing polynuclear silver(I) additives, the antimicrobial action is exerted by contact, without release of silver ions. Moreover, PE composites can be re‐used several times, displaying the same antimicrobial activity. Membrane permeabilization studies and induced reactive oxygen species (ROS) generation tests confirm the disorganization of bacterial cell membranes. The cytotoxic effect, evaluated in CD34+ cells by MTT (3‐(4,5‐dimethylthiazole‐2‐yl)‐2,5‐diphenyltetrazoliumbromide) and CFU (colony forming units) assays, indicates that the PE composites do not induce cytotoxicity in human cells. Studies of ecotoxicity, based on the test of Daphnia magna, confirm tolerability of the PE composites by higher organisms and exclude the release of Ag+ ions in sufficient amounts to affect water environment. 相似文献
937.
Dr. Chad M. Shade Dr. Robert D. Kennedy Dr. Jessica L. Rouge Dr. Mari S. Rosen Mary X. Wang Soyoung E. Seo Dr. Daniel J. Clingerman Prof. Chad A. Mirkin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(31):10983-10987
We report the design and synthesis of small molecules that exhibit enhanced luminescence in the presence of duplex rather than single‐stranded DNA. The local environment presented by a well‐known [Ru(dipyrido[3,2‐a:2′,3′‐c]phenazine)L2]2+‐based DNA intercalator was modified by functionalizing the bipyridine ligands with esters and carboxylic acids. By systematically varying the number and charge of the pendant groups, it was determined that decreasing the electrostatic interaction between the intercalator and the anionic DNA backbone reduced single‐strand interactions and translated to better duplex specificity. In studying this class of complexes, a single RuII complex emerged that selectively luminesces in the presence of duplex DNA with little to no background from interacting with single‐stranded DNA. This complex shows promise as a new dye capable of selectively staining double‐ versus single‐stranded DNA in gel electrophoresis, which cannot be done with conventional SYBR dyes. 相似文献
938.
The B6‐vitamer Pyridoxal is a Sensitizer of UVA‐induced Genotoxic Stress in Human Primary Keratinocytes and Reconstructed Epidermis
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Rebecca Justiniano Joshua D. Williams Jessica Perer Anh Hua Jessica Lesson Sophia L. Park Georg T. Wondrak 《Photochemistry and photobiology》2017,93(4):990-998
UVA‐driven photooxidative stress in human skin may originate from excitation of specific endogenous chromophores acting as photosensitizers. Previously, we have demonstrated that 3‐hydroxypyridine‐derived chromophores including B6‐vitamers (pyridoxine, pyridoxamine and pyridoxal) are endogenous photosensitizers that enhance UVA‐induced photooxidative stress in human skin cells. Here, we report that the B6‐vitamer pyridoxal is a sensitizer of genotoxic stress in human adult primary keratinocytes (HEKa) and reconstructed epidermis. Comparative array analysis indicated that exposure to the combined action of pyridoxal and UVA caused upregulation of heat shock (HSPA6, HSPA1A, HSPA1L, HSPA2), redox (GSTM3, EGR1, MT2A, HMOX1, SOD1) and genotoxic (GADD45A, DDIT3, CDKN1A) stress response gene expression. Together with potentiation of UVA‐induced photooxidative stress and glutathione depletion, induction of HEKa cell death occurred only in response to the combined action of pyridoxal and UVA. In addition to activational phosphorylation indicative of genotoxic stress [p53 (Ser15) and γ‐H2AX (Ser139)], comet analysis indicated the formation of Fpg‐sensitive oxidative DNA lesions, observable only after combined exposure to pyridoxal and UVA. In human reconstructed epidermis, pyridoxal preincubation followed by UVA exposure caused genomic oxidative base damage, procaspase 3 cleavage and TUNEL positivity, consistent with UVA‐driven photooxidative damage that may be relevant to human skin exposed to high concentrations of B6‐vitamers. 相似文献
939.
A synthesis of the putative clausenal structure has been achieved from commercially available carbazole using a five-step sequence that features three iridium-catalyzed C–H borylation reactions. This conceptually disparate approach to carbazole synthesis further demonstrates the utility of the iridium-catalyzed borylation reaction in heteroaromatic C–H functionalization. The spectroscopic data of the synthetic sample casts doubt on the structure assigned to the natural product. 相似文献
940.
Jessica Clavadetscher Dr. Eugenio Indrigo Dr. Sunay V. Chankeshwara Dr. Annamaria Lilienkampf Prof. Mark Bradley 《Angewandte Chemie (International ed. in English)》2017,56(24):6864-6868
Transition metals have been successfully applied to catalyze non-natural chemical transformations within living cells, with the highly efficient labeling of subcellular components and the activation of prodrugs. In vivo applications, however, have been scarce, with a need for the specific cellular targeting of the active transition metals. Here, we show the design and application of cancer-targeting palladium catalysts, with their specific uptake in brain cancer (glioblastoma) cells, while maintaining their catalytic activity. In these cells, for the first time, two different anticancer agents were synthesized simultaneously intracellularly, by two totally different mechanisms (in situ synthesis and decaging), enhancing the therapeutic effect of the drugs. Tumor specificity of the catalysts together with their ability to perform simultaneous multiple bioorthogonal transformations will empower the application of in vivo transition metals for drug activation strategies. 相似文献