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991.
Dr. Frederik Schleife Dr. Clément Bonnot Dr. Jean-Claude Chambron Dr. Martin Börner Prof. Dr. Berthold Kersting 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(21):e202104255
The syntheses and properties of expanded 4-tert-butyl-mercaptocalix[4]arenes, in which the methylene linkers are replaced by −CH2NRCH2− or −CH2NRCH2− and −CH2NRCH2CH2CH2NRCH2− units, are described. The new macrocycles were obtained in a step-wise manner, utilizing fully protected, i. e. S-alkylated, derivatives of the oxidation-sensitive thiophenols in the cyclisation steps. Reductive cleavage of the macrobicyclic or macrotricyclic intermediates ( 6 , 7 , 11 ) afforded the free thiophenols (H4 8 , H4 9 , and H4 12 ) in preparative yields as their hydrochloride salts. The protected proligands can exist in two conformations, resembling the “cone” and “1,3-alternate” conformations found for the parent calix[4]arenes. The free macrocycles do not show conformational isomerism, but are readily oxidized forming intramolecular disulfide linkages. Preliminary complexation experiments show that these expanded mercaptocalixarenes can serve as supporting ligands for tetranuclear thiolato clusters. 相似文献
992.
Hülya Gizem Özkan Vanrajsinh Thakor Hong-Gui Xu Galyna Bila Prof. Dr. Rostyslav Bilyy Daria Bida Dr. Martin Böttcher Prof. Dr. Dimitrios Mougiakakos Dr. Rainer Tietze Prof. Dr. Andriy Mokhir 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202104420
Elevated levels of reactive oxygen species (ROS) and deficient mitochondria are two weak points of cancer cells. Their simultaneous targeting is a valid therapeutic strategy to design highly potent anticancer drugs. The remaining challenge is to limit the drug effects to cancer cells without affecting normal ones. We have previously developed three aminoferrocene (AF)-based derivatives, which are activated in the presence of elevated levels of ROS present in cancer cells with formation of electron-rich compounds able to generate ROS and reduce mitochondrial membrane potential (MMP). All of them exhibit important drawbacks including either low efficacy or high unspecific toxicity that prevents their application in vivo up to date. Herein we describe unusual AF-derivatives lacking these drawbacks. These compounds act via an alternative mechanism: they are chemically stable in the presence of ROS, generate mitochondrial ROS in cancer cells, but not normal cells and exhibit anticancer effect in vivo. 相似文献
993.
Dr. Kristina Sorochkina Dr. Konstantin Chernichenko Prof. Dr. Vladimir V. Zhivonitko Dr. Martin Nieger Prof. Dr. Timo Repo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(61):e202201927
Ortho-phenylene-bridged phosphinoborane (2,6-Cl2Ph)2B-C6H4-PCy2 1 was synthesized in three steps from commercially available starting materials. 1 reacts with H2 or H2O under mild conditions to form corresponding zwitterionic phosphonium borates 1-H2 or 1-H2O . NMR studies revealed both reactions to be remarkably reversible. Thus, when exposed to H2, 1-H2O partially converts to 1-H2 even in the presence of multiple equivalents of water in the solution. The addition of parahydrogen to 1 leads to nuclear spin hyperpolarization both in dry and hydrous solvents, confirming the dissociation of 1-H2O to free 1 . These observations were supported by computational studies indicating that the formation of 1-H2 and 1-H2O from 1 are thermodynamically favored. Unexpectedly, 1-H2O can release molecular hydrogen to form phosphine oxide 1-O . Kinetic, mechanistic, and computational (DFT) studies were used to elucidate the unique “umpolung” water reduction mechanism. 相似文献
994.
Martin Vuagnat Dr. Vincent Tognetti Prof. Dr. Philippe Jubault Dr. Tatiana Besset 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(55):e202201928
In this study, a practical and straightforward synthesis of β-(E)-trifluoromethylstyrenes by ruthenium-catalyzed C−H bond activation was developed. The readily available and inexpensive 2-bromo-3,3,3-trifluoropropene (BTP), a non-ozone depleting reagent, was used as a reservoir of 3,3,3-trifluoropropyne. With this approach, the monofunctionalization of a panel of heteroarenes was possible in a safe and scalable manner (23 examples, up to 87 % yield). Mechanistic investigations and density functional theory (DFT) calculations were also conducted to get a better understanding of the mechanism of this transformation. These studies suggested that 1) a cyclometallated ruthenium complex enabled the transformation, 2) this complex exhibited high efficiency in this transformation compared to the commercially available [RuCl2(p-cymene)]2 and 3) the mechanism proceeded through a bis-cyclometallated ruthenium intermediate for the carboruthenation step. 相似文献
995.
Martin Porubský Dr. Kristýna Vychodilová Dr. David Milićević Dr. Miloš Buděšinský Jarmila Stanková Dr. Petr Džubák Dr. Marián Hajdúch Prof. Jan Hlaváč 《ChemistryOpen》2021,10(11):1104-1110
The combination of cytotoxic amino-BODIPY dye and 2-phenyl-3-hydroxy-4(1H)-quinolinone (3-HQ) derivatives into one molecule gave rise to selective activity against lymphoblastic or myeloid leukemia and the simultaneous disappearance of the cytotoxicity against normal cells. Both species′ conjugation can be realized via a disulfide linker cleavable in the presence of glutathione characteristic for cancer cells. The cleavage liberating the free amino-BODIPY dye and 3-HQ derivative can be monitored by ratiometric fluorescence or by the OFF-ON effect of the amino-BODIPY dye. A similar cytotoxic activity is observed when the amino-BODIPY dye and 3-HQ derivative are connected through a non-cleavable maleimide linker. The work reports the synthesis of several conjugates, the study of their cleavage inside cells, and cytotoxic screening. 相似文献
996.
Matthias Ermer Julian Mehler Björn Rosenberger Dr. Marcus Fischer Dr. Peter S. Schulz Prof. Martin Hartmann 《ChemistryOpen》2021,10(2):233-242
Using ionic liquids (ILs) as linker precursors, the well-known metal-organic framework (MOF) UiO-66 (Universitetet i Oslo) and the recently reported MOF hcp UiO-66 (hexagonal closed packed) have been successfully synthesized and characterized. The advantage of the applied novel synthesis approach is an economically and environmentally benign work-up procedure, due to the better solubility of the IL. Additionally, the reactivity of the terephthalate anions is increased compared to terephthalic acid, resulting in faster MOF formation with an increased amount of defects in the MOF structure. In order to explore to the influence of defects on the catalytic performance, the cyclisation of citronellal to isopulegol was employed as test reaction. The activity of hcp UiO-66 and fcc UiO-66 (face centered cubic) is improved compared to other MOF or zeolite based catalysts, while the selectivity is similar. 相似文献
997.
Excessive uric acid levels in the human body (hyperuricemia) are the main causes of kidney stones and diabetes. In this study, a layer-by-layer arrangement of polymers and nanocomposites is used as a new electrode sensing material for rapid and direct electrochemical determination of uric acid (UA). The electrode surface architecture was constructed by the incorporation of poly (amidoamine) dendrimer with 0.5 generation (poly (amidoamine) [PAMAM] [D-G0.5]) of multiwalled carbon nanotube-silver nanoparticles (MWCNT-AgNP) and a poly (neutral-red) (poly [NR]) polymer. The PAMAM (D-G0.5)/MWCNT-AgNP/poly (NR)-coated electrode has a good electrocatalytic activity for the determination of UA using cyclic voltammetry and showed remarkable enhancement in current response at a low-oxidation potential (0.3 V). Under optimal conditions, the developed electrochemical sensor showed an excellent and wide linear range for the determination of UA (i.e. 0.016 μM–2500 μM), and the limit of detection was found to be 0.005 μM. The modified sensor system demonstrated excellent sensitivity and selectivity toward the detection of UA in the presence of interfering substances, which are commonly found in urine and human fluid samples. Furthermore, the developed sensor has represented both reproducibility and excellent stability for the UA determination in real samples (human urine). 相似文献
998.
Fast and selective analytical methods help to ensure the chemical identity and desired purity of the prepared complexes before their medical application, and play an indispensable role in clinical practice. Mass spectrometry, despite some limitations, is an integral part of these methods. In the context of mass spectrometry, specific problems arise with the low ionization efficiency of particular analytes. Chemical derivatization was used as one of the most effective methods to improve the analyte’s response and separation characteristics. The Schotten–Baumann reaction was successfully adapted for the derivatization of ESI hardly ionizable Re(VII) bis(catechol) oxochlorocomplex. Various alkyl and halogen p-substituted anilines as possible derivatization agents were tested. Unlike the starting complex, the reaction products were easily ionizable in electrospray, providing structurally characteristic molecular and fragment anions. DFT computer modeling, which proposed significant conformation changes of prepared complexes within their deprotonation, proved to have a close link to MS spectra. High-resolution MS and MS/MS measurements complemented with collision-induced dissociation experiments for detailed specification of prepared complexes’ fragmentation pathways were used. The specified fragmentation schemes were analogous for all studied derivatives, with an exception for [Re(O)(Cat)2PIPA]. 相似文献
999.
Scheinherrová Lenka Vejmelková Eva Keppert Martin Doleželová Magdaléna Rovnaníková Pavla Černý Robert 《Journal of Thermal Analysis and Calorimetry》2021,145(6):2951-2966
Journal of Thermal Analysis and Calorimetry - Geopolymers are considered as environmentally friendly binders with a high potential not only to lower the prices of binders, but mainly to decrease... 相似文献
1000.
The fundamental aim of drug design in research and development is to invent molecules with selective affinity towards desired disease-associated targets. At the atomic loci of binding surfaces, systematic structural variations can define affinities between drug candidates and biomolecules, and thereby guide the optimization of safety, efficacy and pharmacologic properties. Hydrophobic interaction between biomolecules and drugs is integral to binding affinity and specificity. Examples of antiviral drug discovery are discussed. 相似文献