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1.
Tobias Bischof Xueying Guo Ivo Krummenacher Lukas Beßler Zhenyang Lin Maik Finze Holger Braunschweig 《Chemical science》2022,13(25):7492
The synthesis of 9-borafluorene with an electron-withdrawing o-carboranyl substituent and its reactions with a series of alkenes are described. The o-carboranyl substituent is bonded via one of the cluster carbon atoms to the boron atom of the 9-borafluorene moiety. In all cases, the reactions afford partly saturated analogs of borepins (i.e. 6,7-dihydroborepins) by unprecedented alkene insertion into the endocyclic B–C bond of the borole ring. Comparative studies with 9-bromo-9-borafluorene illustrate the superior insertion reactivity of the carboranyl-substituted derivative. A suite of experimental and computational techniques disclose the unique properties of the 9-borafluorene and provide insight into how the 9-carboranyl substituent affects its chemical reactivity.A 9-carboranyl-substituted 9-borafluorene is reported, which is capable of undergoing efficient ring expansion to 6,7-dihydroborepins by a previously unknown alkene insertion. 相似文献
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We demonstrate the electrical detection of pulsed X-band electron nuclear double resonance (ENDOR) in phosphorus-doped silicon at 5 K. A pulse sequence analogous to Davies ENDOR in conventional electron spin resonance is used to measure the nuclear spin transition frequencies of the (31)P nuclear spins, where the (31)P electron spins are detected electrically via spin-dependent transitions through Si/SiO(2) interface states, thus not relying on a polarization of the electron spin system. In addition, the electrical detection of coherent nuclear spin oscillations is shown, demonstrating the feasibility to electrically read out the spin states of possible nuclear spin qubits. 相似文献
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Andrea Retzbach Joachim Marschall Marion Rahnke Lukas Otto Michaela Maier 《Journal of nanoparticle research》2011,13(12):6231-6244
In this article, we report data from an online questionnaire study with 587 respondents, representative for the adult U.S.
population in terms of age, gender, and level of education. The aim of this study was to assess how interest in science and
knowledge as well as beliefs about science are associated with risk and benefit perceptions of nanotechnology. The findings
suggest that the U.S. public is still rather unfamiliar with nanotechnology. Those who have some knowledge mainly have gotten
it from TV and the Internet. The content of current media reports is perceived as fairly positive. Knowledge of scientific
methods is unrelated to benefit and risk perceptions, at least when other predictors are controlled. In contrast, positive
beliefs about science (e.g., its impact on economy or health) and more sophisticated epistemological beliefs about the nature
of scientific knowledge are moderately linked to more positive perceptions of nanotechnology. The only exception is the perception
of scientific uncertainty: This is associated with less positive evaluations. Finally, higher engagement with science is associated
with higher risk perceptions. These findings show that laypersons who are engaged with science and who are aware of the inherent
uncertainty of scientific evidence might perceive nanotechnology in a somewhat more differentiated way, contrary to how it
is portrayed in the media today. 相似文献
7.
Lukas Pietzonka Thomas Lautenschläger Daniel Spemann Annemarie Finzel Jürgen W. Gerlach Frank Frost Carsten Bundesmann 《The European Physical Journal B - Condensed Matter and Complex Systems》2018,91(10):252
TiO2 thin films were grown by ion beam sputter deposition (IBSD) using oxygen ions, with the ion energy and geometrical parameters (ion incidence angle, polar emission angle, and scattering angle) being varied systematically. Metallic Ti and ceramic TiO2 served as target materials. The thin films were characterized concerning thickness, growth rate, surface topography, structural properties, mass density, and optical properties. It was found that the scattering geometry has the main impact on the film properties. Target material, ion energy, and ion incidence angle have only a marginal influence. Former studies on reactive IBSD of TiO2 using Ar and Xe ions reported equivalent patterns. Nevertheless, the respective ion species distinctively affects the film properties. For instance, mass density and the refractive index of the TiO2 thin films are remarkably lower for sputtering with oxygen ions than for sputtering with Ar or Xe ions. The variations in the thin film properties are tentatively attributed to the angular and the energy distribution of the film-forming particles, especially, to those of the backscattered primary particles. 相似文献
8.
Jan Rosenboom Dr. Lukas Chojetzki Dr. Tim Suhrbier Dr. Jabor Rabeah Dr. Alexander Villinger Dr. Ronald Wustrack Dr. Jonas Bresien Prof. Dr. Axel Schulz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(36):e202200624
The activation of C−Br bonds in various bromoalkanes by the biradical [⋅P(μ-NTer)2P⋅] ( 1 ) (Ter=2,6-bis-(2,4,6-trimethylphenyl)-phenyl) is reported, yielding trans-addition products of the type [Br−P(μ-NTer)2P−R] ( 2 ), so-called 1,3-substituted cyclo-1,3-diphospha-2,4-diazanes. This addition reaction, which represents a new easy approach to asymmetrically substituted cyclo-1,3-diphospha-2,4-diazanes, was investigated mechanistically by different spectroscopic methods (NMR, EPR, IR, Raman); the results suggested a stepwise radical reaction mechanism, as evidenced by the in-situ detection of the phosphorus-centered monoradical [⋅P(μ-NTer)2P-R].< To provide further evidence for the radical mechanism, [⋅P(μ-NTer)2P-Et] ( 3Et ⋅) was synthesized directly by reduction of the bromoethane addition product [Br-P(μ-NTer)2P-Et] ( 2 a ) with magnesium, resulting in the formation of the persistent phosphorus-centered monoradical [⋅P(μ-NTer)2P-Et], which could be isolated and fully characterized, including single-crystal X-ray diffraction. Comparison of the EPR spectrum of the radical intermediate in the addition reaction with that of the synthesized new [⋅P(μ-NTer)2P-Et] radical clearly proves the existence of radicals over the course of the reaction of biradical [⋅P(μ-NTer)2P⋅] ( 1 ) with bromoethane. Extensive DFT and coupled cluster calculations corroborate the experimental data for a radical mechanism in the reaction of biradical [⋅P(μ-NTer)2P⋅] with EtBr. In the field of hetero-cyclobutane-1,3-diyls, the demonstration of a stepwise radical reaction represents a new aspect and closes the gap between P-centered biradicals and P-centered monoradicals in terms of radical reactivity. 相似文献
9.
Philipp Rotering Lukas F. B. Wilm Janina A. Werra Dr. Fabian Dielmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(2):406-411
Electron-rich tertiary phosphines are valuable species in chemical synthesis. However, their broad application as ligands in catalysis and reagents in stoichiometric reactions is often limited by their costly synthesis. Herein, we report the synthesis and properties of a series of phosphines with 1-alkylpyridin-4-ylidenamino and 1-alkylpyridin-2-ylidenamino substituents that are accessible in a very short and scalable route starting from commercially available aminopyridines and chlorophosphines. The determination of the Tolman electronic parameter (TEP) value reveals that the electron donor ability can be tuned by the substituent pattern at the aminopyridine backbone and it can exceed that of common alkylphosphines and N-heterocyclic carbenes. The potential of the new phosphines as strong nucleophiles in phosphine-mediated transformations is demonstrated by the formation of Lewis base adducts with CO2 and CS2. In addition, the coordination chemistry of the new phosphines towards CuI, AuI, and PdII metal centers has been explored, and a convenient procedure to introduce the most basic phosphine into metal complexes starting from air-stable phosphonium salt is described. 相似文献
10.
Hendrik Schneider Lukas Deweid Thomas Pirzer Desislava Yanakieva Simon Englert Bastian Becker Dr. Olga Avrutina Prof. Dr. Harald Kolmar 《ChemistryOpen》2019,8(3):354-357
Antibody-drug conjugates (ADCs) are multicomponent biomolecules that have emerged as a powerful tool for targeted tumor therapy. Combining specific binding of an immunoglobulin with toxic properties of a payload, they however often suffer from poor hydrophilicity when loaded with a high amount of toxins. To address these issues simultaneously, we developed dextramabs, a novel class of hybrid antibody-drug conjugates. In these architectures, the therapeutic antibody trastuzumab is equipped with a multivalent dextran polysaccharide that enables efficient loading with a potent toxin in a controllable fashion. Our modular chemoenzymatic approach provides an access to synthetic dextramabs bearing monomethyl auristatin as releasable cytotoxic cargo. They possess high drug-to-antibody ratios, remarkable hydrophilicity, and high toxicity in vitro. 相似文献