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991.
Kerim Samedov Yannic Heider Yuanjing Cai Philipp Willmes Daniel Mühlhausen Volker Huch Robert West David Scheschkewitz Paul W. Percival 《Angewandte Chemie (International ed. in English)》2020,59(37):16007-16012
Understanding the characteristics of radicals formed from silicon‐containing heavy analogues of alkenes is of great importance for their application in radical polymerization. Steric and electronic substituent effects in compounds such as phosphasilenes not only stabilize the Si=P double bond, but also influence the structure and species of the formed radicals. Herein we report our first investigations of radicals derived from phosphasilenes with Mes, Tip, Dur, and NMe2 substituents on the P atom, using muon spin spectroscopy and DFT calculations. Adding muonium (a light isotope of hydrogen) to phosphasilenes reveals that: a) the electron‐donor NMe2 and the bulkiest Tip‐substituted phosphasilenes form several muoniated radicals with different rotamer conformations; b) bulky Dur‐substituted phosphasilene forms two radicals (Si‐ and P‐centred); and c) Mes‐substituted phosphasilene mainly forms one species of radical, at the P centre. These significant differences result from intramolecular substituent effects. 相似文献
992.
Philipp E. Hofmann Matthias W. Tripp Daniel Bischof Yvonne Grell Anna L. C. Schiller Tobias Breuer Sergei I. Ivlev Gregor Witte Ulrich Koert 《Angewandte Chemie (International ed. in English)》2020,59(38):16501-16505
The rapid development of organic electronics is closely related to the availability of molecular materials with specific electronic properties. Here, we introduce a novel synthetic route enabling a unilateral functionalization of acenes along their long side, which is demonstrated by the synthesis of 1,2,10,11,12,14‐hexafluoropentacene ( 1 ) and the related 1,2,9,10,11‐pentafluorotetracene ( 2 ). Quantum chemical DFT calculations in combination with optical and X‐ray absorption spectroscopy data indicate that the single‐molecule properties of 1 are a connecting link between the organic semiconductor model systems pentacene (PEN) and perfluoropentacene (PFP). In contrast, the crystal structure analysis reveals a different packing motif than for the parent molecules. This can be related to distinct F???H interactions identified in the corresponding Hirshfeld surface analysis and also affects solid‐state properties such as the exciton binding energy and the sublimation enthalpy. 相似文献
993.
994.
Thorsten Rieth Natalie Tober Daniel Limbach Tobias Haspel Marcel Sperner Niklas Schupp Philipp Wicker Stefan Glang Matthias Lehmann Heiner Detert 《Molecules (Basel, Switzerland)》2020,25(23)
Tristriazolotriazines (TTTs) with a threefold alkoxyphenyl substitution were prepared and studied by DSC, polarized optical microscopy (POM) and X-ray scattering. Six pentyloxy chains are sufficient to induce liquid-crystalline behavior in these star-shaped compounds. Thermotropic properties of TTTs with varying substitution patterns and a periphery of linear chains of different lengths, branching in the chain and swallow-tails, are compared. Generally, these disks display broad and stable thermotropic mesophases, with the tangential TTT being superior to the radial isomer. The structure–property relationships of the number of alkyl chains, their position, length and structure were studied. 相似文献
995.
Tobias Ullrich Piermaria Pinter Julian Messelberger Philipp Haines Ramandeep Kaur Max M. Hansmann Dominik Munz Dirk M. Guldi 《Angewandte Chemie (International ed. in English)》2020,59(20):7906-7914
Herein, we present a new class of singlet fission (SF) materials based on diradicaloids of carbene scaffolds, namely cyclic (alkyl)(amino)carbenes (CAACs). Our modular approach allows the tuning of two key SF criteria: the steric factor and the diradical character. In turn, we modified the energy landscapes of excited states in a systematic manner to accommodate the needs for SF. We report the first example of intermolecular SF in solution by dimer self‐assembly at cryogenic temperatures. 相似文献
996.
Philipp Mostosi Hermann Schindelin Philip Kollmannsberger Andrea Thorn 《Angewandte Chemie (International ed. in English)》2020,59(35):14788-14795
In recent years, three‐dimensional density maps reconstructed from single particle images obtained by electron cryo‐microscopy (cryo‐EM) have reached unprecedented resolution. However, map interpretation can be challenging, in particular if the constituting structures require de‐novo model building or are very mobile. Herein, we demonstrate the potential of convolutional neural networks for the annotation of cryo‐EM maps: our network Haruspex has been trained on a carefully curated set of 293 experimentally derived reconstruction maps to automatically annotate RNA/DNA as well as protein secondary structure elements. It can be straightforwardly applied to newly reconstructed maps in order to support domain placement or as a starting point for main‐chain placement. Due to its high recall and precision rates of 95.1 % and 80.3 %, respectively, on an independent test set of 122 maps, it can also be used for validation during model building. The trained network will be available as part of the CCP‐EM suite. 相似文献
997.
Fenja L. Duecker Dr. Robert C. Heinze Dr. Simon Steinhauer Prof. Dr. Philipp Heretsch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(44):9971-9981
In this work, a full account of the authors’ synthetic studies is reported that culminated in the first synthesis of 13(14→8),14(8→7)diabeo-steroid swinhoeisterol A as well as the related dankasterones A and B, 13(14→8)abeo-steroids, and periconiastone A, a 13(14→8)abeo-4,14-cyclo-steroid. Experiments are described in detail that provided further insight into the mechanism of the switchable radical framework reconstruction approach. By discussing failed strategies and tactics towards swinhoeisterol A, the successful route that also allowed an access to structurally closely related analogues, such as Δ22-24-epi-swinhoeisterol A, is eventually presented. 相似文献
998.
Philipp Buday Phillip Seeber Clara Zens Dr. Hassan Abul-Futouh Dr. Helmar Görls Prof. Dr. Stefanie Gräfe Dr. Piotr Matczak Dr. Stephan Kupfer Prof. Dr. Wolfgang Weigand Prof. Dr. Grzegorz Mloston 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(50):11412-11416
Reactions of α,β-unsaturated aromatic thioketones 1 (thiochalcones) with Fe3(CO)12 leading to η4-1-thia-1,3-diene iron tricarbonyl complexes 2 , [FeFe] hydrogenase mimics 3 , and the thiopyrane adduct 4 are described. Obtained products have been characterized by X-ray crystallography and by computational methods. Completely regio- and diastereoselective formation of the five-membered ring system in products 3 , containing four stereogenic centers, can be explained by an unprecedented, stepwise (3+2)-cycloaddition of two thiochalcone molecules mediated by Fe3(CO)12. Quantum chemical calculations aimed at elucidation of the reaction mechanism, suggest that the formal (3+2)-cycloaddition proceeds via sequential intramolecular radical transfer events upon homolytic cleavage of one carbon-sulfur bond leading to a diradical intermediate. 相似文献
999.
1000.
Der Satz von Bell behauptet, da? die Existenz von sogenannten objektiv Einstein-lokalen verborgenen Variablen und die Quantenmechanik unvereinbar sind. Der von Bell gegebene Beweis ist rein mathematischer Natur und schlie?t eine gewisse Klasse von verborgenen Variablen aus. Bells Beweis beruht auf der nun berühmten Bellschen Ungleichung, die eng mit dem Konsistenzproblem von Wahrscheinlichkeitsverteilungen für drei Paare von Zufallsver?nderlichen verbunden ist. Ziel dieser Arbeit ist es, einen überblick über diesen Gedankenkreis zu geben, sowie eine Reihe von weiteren in der Literatur erschienenen Beweisans?tze zu analysieren und gleichzeitig zu zeigen, da? man mit diesen Beweismethoden nicht alle Einstein-lokalen verborgenen Variablen ausschlie?en kann. 相似文献