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111.
Dr. Mara Beltrán-Gastélum Dr. Berta Esteban-Fernández de Ávila Dr. Hua Gong Dr. Pooyath Lekshmy Venugopalan Prof. Dr. Tibor Hianik Prof. Dr. Joseph Wang Veronika Subjakova 《Chemphyschem》2019,20(23):3177-3180
Herein, we report ultrasound-propelled graphene-oxide coated gold nanowire motors, functionalized with fluorescein-labeled DNA aptamers (FAM-AIB1-apt), for qualitative detection of overexpressed AIB1 oncoproteins in MCF-7 breast cancer cells. The movement of nanomotors under the ultrasound field facilitated intracellular uptake and resulted in a faster aptamer binding with the target protein and thus faster fluorescence recovery. The propulsion behavior of the aptamer functionalized nanomotors greatly enhanced the fluorescence intensity compared to static conditions. The new aptamer@nanomotor-based strategy offers considerable potential for further development of sensing methodologies towards diagnosis of breast cancer. 相似文献
112.
Reaction of an N‐Heterocyclic Carbene‐Stabilized Silicon(II) Monohydride with Alkynes: [2+2+1] Cycloaddition versus Hydrogen Abstraction
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Carsten Eisenhut Tibor Szilvási Dr. Nora C. Breit Prof. Dr. Shigeyoshi Inoue 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(5):1949-1954
An in depth study of the reactivity of an N‐heterocyclic carbene (NHC)‐stabilized silylene monohydride with alkynes is reported. The reaction of silylene monohydride 1 , tBu3Si(H)Si←NHC, with diphenylacetylene afforded silole 2 , tBu3Si(H)Si(C4Ph4). The density functional theory (DFT) calculations for the reaction mechanism of the [2+2+1] cycloaddition revealed that the NHC played a major part stabilizing zwitterionic transition states and intermediates to assist the cyclization pathway. A significantly different outcome was observed, when silylene monohydride 1 was treated with phenylacetylene, which gave rise to supersilyl substituted 1‐alkenyl‐1‐alkynylsilane 3 , tBu3Si(H)Si(CH?CHPh)(C?CPh). Mechanistic investigations using an isotope labelling technique and DFT calculations suggest that this reaction occurs through a similar zwitterionic intermediate and subsequent hydrogen abstraction from a second molecule of phenylacetylene. 相似文献
113.
Dr. Wan-Shan Li Dr. Ren-Jie Yan Yi Yu Prof. Zhi Shi Dr. Attila Mándi Dr. Li Shen Prof. Tibor Kurtán Prof. Jun Wu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(31):13128-13136
Marine dinoflagellates produce remarkable organic molecules, particularly those with polyoxygenated long-carbon-chain backbones, namely super-carbon-chain compounds (SCCCs), characterized by the presence of numerous stereogenic carbon centers on acyclic polyol carbon chains. Even today, it is a challenge to determine the absolute configurations of these compounds. In this work, the planar structures and absolute configurations of two highly flexible SCCCs, featuring either a C69- or C71-linear carbon backbone, gibbosols A and B, respectively, each containing thirty-seven stereogenic carbon centers, were unambiguously established by a combined chemical, spectroscopic, and computational approach. The discovery of gibbosols A and B with two hydrophilic acyclic polyol chains represents an unprecedented class of SCCCs. A reasonable convergent strategy for the biosynthesis of these SCCCs was proposed. 相似文献
114.
Szilrd Varga Pter Angyal Gbor Martin Orsolya Egyed Tams Holczbauer Tibor Sos 《Angewandte Chemie (International ed. in English)》2020,59(32):13547-13551
We report 8‐step syntheses of (?)‐minovincine and (?)‐aspidofractinine using easily available and inexpensive reagents and catalyst. A key element of the strategy was the utilization of a sequence of cascade reactions to rapidly construct the penta‐ and hexacyclic frameworks. These cascade transformations included organocatalytic Michael‐aldol condensation, a multistep anionic Michael‐SN2 cascade reaction, and Mannich reaction interrupted Fischer indolization. To streamline the synthetic routes, we also investigated the deliberate use of steric effect to secure various chemo‐ and regioselective transformations. 相似文献
115.
116.
Miada F. Abdelwahab Tibor Kurtán Attila Mándi Werner E.G. Müller Mostafa A. Fouad Mohamed S. Kamel Zhen Liu Weaam Ebrahim Georgios Daletos Peter Proksch 《Tetrahedron letters》2018,59(27):2647-2652
Two new cryptic 3,4-dihydronaphthalen-(2H)-1-one (1-tetralone) derivatives, aspvanicin A (1) and its epimer aspvanicin B (2), as well as several known cryptic metabolites (3–8), were obtained from the ethyl acetate extract of the co-culture of the endophytic fungus Aspergillus versicolor KU258497 with the bacterium Bacillus subtilis 168 trpC2 on solid rice medium. When A. versicolor was cultured axenically in liquid Wickerham medium supplemented with 3.5% DMSO, an additional three known secondary metabolites (9–11) were isolated that were lacking when the fungus was fermented on rice medium. The structures of the new compounds were elucidated using one- and two-dimensional NMR spectroscopy as well as HRESIMS. The relative and absolute configurations of 1 and 2 were determined by the combination of NMR and electronic circular dichroism (ECD) analysis aided by DFT conformational analysis and TDDFT-ECD calculations. The ECD calculations revealed that although the sign of the blue-shifted overlapping n-π1 ECD transition follows the helicity rule of cyclic aryl ketones, the calculation of low-energy conformers and ECD spectra was necessary to determine the stereochemistry. All metabolites were assessed for their antibacterial and cytotoxic activities; one of the new diastereomers, compound 2, showed moderate cytotoxic activity against the mouse lymphoma cell line L5178Y. 相似文献
117.
Ostatná V Vaisocherová H Homola J Hianik T 《Analytical and bioanalytical chemistry》2008,391(5):1861-1869
We report a multichannel surface plasmon resonance (SPR) sensor for detection of thrombin via DNA aptamers immobilized on
the SPR sensor surface. A detailed investigation of the effect of the immobilisation method on the interaction between thrombin
and DNA aptamers is presented. Three basic approaches to the immobilisation of aptamers on the surface of the SPR sensor are
examined: (i) immobilisation based on chemisorption of aptamers modified with SH groups, (ii) immobilisation of biotin-tagged
aptamers via previously immobilized avidin, neutravidin or streptavidin molecular linkers, and (iii) immobilisation employing
dendrimers as a support layer for subsequent immobilisation of aptamers. A level of nonspecific binding of thrombin to immobilized
human serum albumin (HSA) for each of the immobilisation methods is determined. Immobilisation of aptamers by means of the
streptavidin–biotin system yields the best results both in terms of sensor specificity and sensitivity. 相似文献
118.
Gennady A. Evtugyn Anna V. Porfireva Tibor Hianik Maria S. Cheburova Herman C. Budnikov 《Electroanalysis》2008,20(12):1300-1308
Novel method of potentiometric detection of DNA‐protein interactions has been proposed. For this purpose, polymeric phenothiazine dyes, methylene blue (MB) and methylene green (MG), were electrochemically deposited onto the glassy carbon electrode and covered with double stranded DNA (dsDNA) as a target for antibodies (DNA‐sensor) or DNA aptamer specific to human α‐thrombin (aptasensor). The biosensors were consecutively incubated at pH 7.5 and 3.0 and the difference in potentials, ΔE, was used as a measure of protein concentration. The potentiometric DNA‐sensors were tested in standard serum of autoimmune disease patients (systemic lupus erythemathosus (SLE) and autoimmune thyroidites). It was shown, that the ΔE value of DNA‐sensor depends on the dilution of serum in the range from 1 : 1 to 1 : 100. Nonthermostated serum exhibited bell‐shape dependence of ΔE on serum dilution due to interfering effect of serine proteins at maximum dilution between 1 : 20 and 1 : 50. For SLE serum thermostated at 56 °C the ΔE linearly decreased as a function of serum dilution and reached saturation at dilution 1 : 20. Similarly the changes in the potential of aptasensor allowed us to determine the α‐thrombin in the range from 1 nM to 1 μM. The Faradic impedance spectra measured at presence of redox probe [Fe(CN)6]4?/3? revealed changes in the resistance and capacitance attributed to the shielding effect of anti‐DNA antibodies and an increase in the electron transfer. The developed potentiometric biosensors can be used for preliminary diagnostics of autoimmune diseases and thrombin detection with sensitivity comparable to traditional methods. The developed assay is, however simpler and cheaper in comparison with commonly used methods. 相似文献
119.
Low-frequency, high-amplitude pH-oscillations observed experimentally in the H2O2-HSO3(-)-S2O3(-) flow reaction system at 21.0 degrees C undergo period-doubling cascades to chemical chaos upon decreasing the temperature to 19.0 degrees C in small steps. Period-4 oscillations are observed at 20.0 degrees C and can be calculated on the basis of a simple model. A reverse transition from chaos to high-frequency limit cycle oscillations is also observable in the reaction system upon decreasing further the temperature step by step to 15.0 degrees C. Period-2 oscillations are measured at 18.0 degrees C. Such a temperature-change-induced transition between periodic and chaotic oscillatory states can be understood by taking into account the different effects of temperature on the rates of composite reactions in the oscillatory system. Small differences in the activation energies of the composite reactions are responsible for the observed transitions. Temperature-change-induced period doubling is suggested as a simple tool for determining whether an experimentally observed random behavior in chemical systems is of deterministic origin or due to experimental noise. 相似文献
120.
Philip M. Keil Ademola Soyemi Kilian Weisser Prof. Tibor Szilvási Prof. Christian Limberg Dr. Terrance J. Hadlington 《Angewandte Chemie (International ed. in English)》2023,62(19):e202381961
The open-shell cationic stannylene-iron(0) complex 4 ( 4 =[PhiPDippSn⋅Fe⋅IPr]+; PhiPDipp={[Ph2PCH2Si(iPr)2](Dipp)N}; Dipp=2,6-iPr2C6H3; IPr=[(Dipp)NC(H)]2C:) cooperatively and reversibly cleaves dihydrogen at the Sn−Fe interface under mild conditions (1.5 bar, 298 K), in forming bridging hydrido-complex 6 . The One-electron oreduction of the related GeII−Fe0 complex 3 leads to oxidative addition of one C−P linkage of the PhiPDipp ligand in an intermediary Fe−I complex, leading to FeI phosphide species 7 . One-electron reduction reaction of 4 gives access to the iron(−I) ferrato-stannylene, 8 , giving evidence for the transient formation of such a species in the reduction of 3 . The covalently bound tin(II)-iron(−I) compound 8 has been characterised through EPR spectroscopy, SQUID magnetometry, and supporting computational analysis, which strongly indicate a high localization of electron spin density at Fe−I in this unique d9-iron complex. 相似文献