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971.
Dr. Adrien T. Normand Dr. Quentin Bonnin Dr. Stéphane Brandès Dr. Philippe Richard Prof. Paul Fleurat-Lessard Dr. Charles H. Devillers Cédric Balan Prof. Pierre Le Gendre Dr. Gerald Kehr Prof. Gerhard Erker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(11):2803-2815
Tame d0 phosphidotitanocene cations stabilized with a pendant tertiary phosphane arm are reported. These compounds were obtained by one-electron oxidation of d1 precursors with [Cp2Fe][BPh4]. The electronic structure of these compounds was studied experimentally (EPR, UV/Vis, and NMR spectroscopy, X-ray diffraction analysis) and through DFT calculations. The theoretical analysis of the bonding situation by using the electron localization function (ELF) shows the presence of π-interactions between the phosphido ligand and Ti in the d0 complexes, whereas dπ–pπ repulsion prevents such interactions in the d1 complexes. In addition, CH–π interactions were observed in several complexes, both in solution and in the solid state, between the phosphido ligand and the phosphane arm. The d0 complexes were found to be light sensitive, and decompose through Ti−P bond homolysis to give TiIII species. A naked d0 phosphidotitanocene cation has been trapped by reaction with diphenylacetylene, yielding a Ti/P frustrated Lewis pair (FLP), which was found to be less reactive than a previously reported Zr analog. 相似文献
972.
M. Sc. Tony Stüker M. Sc. Thomas Hohmann Dr. Helmut Beckers Prof. Sebastian Riedel 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(51):23374-23379
The fluoronitrenoid metal complexes FNCoF2 and FNRhF2 as well as the first ternary RhVI and IrVI complexes NIrF3 and NRhF3 are described. They were obtained by the reaction of excited Group-9 metal atoms with NF3 and their IR spectra, isolated in solid rare gases (neon and argon), were recorded. Aided by the observed 14/15N isotope shifts and quantum-chemical predictions, all four stretching fundamentals of the novel complexes were safely assigned. The F−N stretching frequencies of the fluoronitrenoid complexes FNCoF2 (1056.8 cm−1) and FNRhF2 (872.6 cm−1) are very different and their N−M bonds vary greatly. In FNCoF2, the FN ligand is singly bonded to Co and bears considerable iminyl/nitrene radical character, while the N−Rh bond in FNRhF2 is a strong double bond with comparatively strong σ- and π-bonds. The anticipated rearrangement of FNCoF2 to the nitrido CoVI complex is predicted to be endothermic and was not observed. 相似文献
973.
Anna Bonfiglio Lenka Pallova Dr. Vincent César Dr. Christophe Gourlaouen Dr. Stéphane Bellemin-Laponnaz Dr. Chantal Daniel Dr. Federico Polo Dr. Matteo Mauro 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(51):11751-11766
A novel class of phosphorescent cationic heterobimetallic IrIII/MI complexes, where MI=CuI ( 4 ) and AuI ( 5 ), is reported. The two metal centers are connected by the hybrid bridging 1,3-dimesityl-5-acetylimidazol-2-ylidene-4-olate (IMesAcac) ligand that combines both a chelating acetylacetonato-like and a monodentate N-heterocyclic carbene site coordinated onto an IrIII and a MI center, respectively. Complexes 4 and 5 have been prepared straightforwardly by a stepwise site-selective metalation with the zwitterionic [(IPr)MI(IMesAcac)] metalloproligand (IPr=1,3-(2,6-diisopropylphenyl)-2H-imidazol-2-ylidene) and they have been fully characterized by spectroscopic, electrochemical, and computational investigation. Complexes 4 and 5 display intense red emission arising from a low-energy excited state that is located onto the “Ir(C^N)” moiety featuring an admixed triplet ligand-centered/metal-to-ligand charge transfer (3IL/1MLCT) character. Comparison with the benchmark mononuclear complexes reveals negligible electronic coupling between the two distal metal centers at the electronic ground state. The bimetallic systems display enhanced photophysical properties in comparison with the parental congeners. Noteworthy, similar non-radiative rate constants have been determined along with a two-fold increase of radiative rate, yielding brightly red-emitting cyclometalating IrIII complexes. This finding is ascribed to the increased MLCT character of the emitting state in complexes 4 and 5 due to the smaller energy gap between the 3IL and 1MLCT manifolds, which mix via spin–orbit coupling. 相似文献
974.
Dr. Leandro Trupp Dr. Andrea C. Bruttomesso Dr. Svetlana V. Eliseeva Dr. Stéphane Petoud Dr. Javier A. Ramírez Dr. Beatriz C. Barja 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(55):12645-12653
Herein, the design, synthesis, and characterization of a phenhomazine ligand are described. The ligand has six pendant acetate arms designed for the combined coordination of copper(II) and lanthanide(III) ions, with the perspective of developing a “turn-off” copper sensor. The key step for the ligand preparation was the one-step endomethylene bridge fission of a diamino Tröger's base with a concomitant alkylation. Fluorescence and absorption spectroscopies as well as nuclear magnetic resonance (NMR) experiments were performed to analyze and understand the coordination properties of the ligand. Transition metal coordination was driven by the synergistic effect of the free nitrogen atoms of the diazocinic core and the two central acetate arms attached to those nitrogen atoms, whereas lanthanide coordination is performed by the external acetate arms, presumably forming a self-assembled 2:2 metallosupramolecular structure. The terbium complex shows the typical green emission with narrow bands and long luminescence lifetimes. The luminescence quenching produced by the presence of copper(II) ions was analyzed. This work sets, therefore, a starting point for the development of a phenhomazine-based “turn-off” copper(II) sensor. 相似文献
975.
Dr. G. Henrieke Heideman Dr. José Augusto Berrocal Prof. Meike Stöhr Prof. E. W. Meijer Prof. Ben L. Feringa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):207-211
The development of new strategies for the preparation of multicomponent supramolecular assemblies is a major challenge on the road to complex functional molecular systems. Here we present the use of a non-porous self-assembled monolayer from uC33-NDI-uC33 , a naphthalenediimide symmetrically functionalized with unsaturated 33 carbon-atom-chains, to prepare bicomponent supramolecular surface systems with a series of alkoxy-pyrene ( PyrOR ) derivatives at the liquid/HOPG interface. While previous attempts at directly depositing many of these PyrOR units at the liquid/HOPG interface failed, the multicomponent approach through the uC33-NDI-uC33 template enabled control over molecular interactions and facilitated adsorption. The PyrOR deposition restructured the initial uC33-NDI-uC33 monolayer, causing an expansion in two dimensions to accommodate the guests. As far as we know, this represents the first example of a non-porous or non-metal complex-bearing monolayer that allows the stepwise formation of multicomponent supramolecular architectures on surfaces. 相似文献
976.
Dr. Daniela Mélanie Delannoy López Dr. Dong Tien Tran Dr. Guillaume Viault Dr. Sofiane Dairi Dr. Philippe Alexandre Peixoto Yoan Capello Laëtitia Minder Prof. Laurent Pouységu Dr. Elisabeth Génot Dr. Carmelo Di Primo Dr. Denis Deffieux Prof. Stéphane Quideau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(17):5498-5508
A selection of bioactive polyphenols of different structural classes, such as the ellagitannins vescalagin and vescalin, the flavanoids catechin, epicatechin, epigallocatechin gallate (EGCG), and procyanidin B2, and the stilbenoids resveratrol and piceatannol, were chemically modified to bear a biotin unit for enabling their immobilization on streptavidin-coated sensor chips. These sensor chips were used to evaluate in real time by surface plasmon resonance (SPR) the interactions of three different surface-bound polyphenolic ligands per sensor chip with various protein analytes, including human DNA topoisomerase IIα, flavonoid leucoanthocyanidin dioxygenase, B-cell lymphoma 2 apoptosis regulator protein, and bovine serum albumin. The types and levels of SPR responses unveiled major differences in the association, or lack thereof, and dissociation between a given protein analyte and different polyphenolic ligands. Thus, this multi-analysis SPR technique is a valuable methodology to rapidly screen and qualitatively compare various polyphenol–protein interactions. 相似文献
977.
J. Rothhardt M. Bilal R. Beerwerth A.V. Volotka V. Hilbert T. Stöhlker S. Fritzsche J. Limpert 《X射线光谱测定》2020,49(1):165-168
We propose to measure the lifetime of short-lived excited states in highly charged ions by pump-probe experiments. Utilizing two synchronized and delayed Femtosecond pulses allows accessing these lifetimes with Femtosecond precision. Such measurements could provide sensitive tests of state-of-the art atomic structure calculations beyond the capabilities of established methods. 相似文献
978.
Dr. Cédric Tresse Dr. Marc François-Heude Vincent Servajean Rubal Ravinder Clémence Lesieur Lucie Geiben Dr. Louis Jeanne-Julien Vincent Steinmetz Dr. Pascal Retailleau Dr. Emmanuel Roulland Prof. Dr. Jean-Marie Beau Dr. Stéphanie Norsikian 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5230-5239
We give a full account of the total synthesis of tiacumicin B (Tcn-B), a natural glycosylated macrolide with remarkable antibiotic properties. Our strategy is based on our experience with the synthesis of the tiacumicin B aglycone and on unique 1,2-cis-glycosylation steps. We used sulfoxide anomeric leaving-groups in combination with a remote 3-O-picoloyl group on the donors that allowed highly β-selective rhamnosylation and noviosylation that rely on H-bond-mediated aglycone delivery. The rhamnosylated C1–C3 fragment was anchored to the C4–C19 aglycone fragment by a Suzuki–Miyaura cross-coupling. Ring-size-selective Shiina macrolactonization provided a semiglycosylated aglycone that was engaged directly in the noviolysation step with a virtually total β-selectivity. Finally, a novel deprotection method was devised for the removal of a 2-naphthylmethyl ether on a phenol, and efficient removal of all the protecting groups provided synthetic tiacumicin B. 相似文献
979.
G. A. Le Roy Henry R. Procter St. Krawczynski Alex F. Reid Ch. O. Curtman Carl Meissner C. Meineke und M. Ripper 《Fresenius' Journal of Analytical Chemistry》1893,32(1):453-458
Ohne Zusammenfassung 相似文献
980.