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51.
Lukas Fischer Alexander K. Strzelczyk Nils Wedler Christian Kropf Stephan Schmidt Laura Hartmann 《Chemical science》2020,11(36):9919
Catechol and amine residues, both abundantly present in mussel adhesion proteins, are known to act cooperatively by displacing hydration barriers before binding to mineral surfaces. In spite of synthetic efforts toward mussel-inspired adhesives, the effect of positioning of the involved functional groups along a polymer chain is not well understood. By using sequence-defined oligomers grafted to soft hydrogel particles as adhesion probes, we study the effect of catechol–amine spacing, as well as positioning relative to the oligomer terminus. We demonstrate that the catechol–amine spacing has a significant effect on adhesion, while shifting their position has a small effect. Notably, combinations of non-charged amides and catechols can achieve similar cooperative effects on adhesion when compared to amine and catechol residues. Thus, these findings provide a blueprint for the design of next generation mussel-inspired adhesives.The catechol driven adhesion of precision macromolecules on glass surfaces is quantified by soft colloidal probe readout. Catechol moieties are shown to synergize with amine and amide residues depending on residue spacing and residue order. 相似文献
52.
Furstner A Thiel OR Ackermann L Schanz HJ Nolan SP 《The Journal of organic chemistry》2000,65(7):2204-2207
The ruthenium carbene complexes 3a,b bearing imidazol-2-ylidene ligands constitute excellent precatalysts for ring-closing metathesis (RCM) reactions allowing the formation of tri- and tetrasubstituted cycloalkenes. They also apply to annulations that are beyond the scope of the standard Grubbs carbene 1 as well as to ring-closing reactions of acrylic acid derivatives even if the resulting alpha,beta-unsaturated lactones (or lactams) are tri- or tetrasubstituted. The reactivity of 3a was found to be highly dependent on the reaction medium: particularly high reaction rates are observed in toluene, although this solvent also leads to an increased tendency of the catalyst to isomerize the double bonds of the substrates. 相似文献
53.
Moses Salci Evgeny Yarevsky Sergey B. Levin Nils Elander 《International journal of quantum chemistry》2007,107(2):464-468
A three‐dimensional finite element method is applied to the ground states of the symmetric and asymmetric atomic helium trimers 4He3 and 4He2–3He. Three different He–He interaction potentials of hard‐core nature were studied. Two extrapolation procedures based on the convergence properties of the finite element method are investigated. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
54.
D. Dubbers H. Ackermann M. Grupp P. Heitjans H. -J. Stöckmann 《Zeitschrift für Physik B Condensed Matter》1976,25(4):363-368
An experimental method is presented which allows the determination of the sign of nuclear electric quadrupole interactions in solids. Activated target nuclei with a purely dipolar spin polarization are produced by capture of polarized thermal neutrons. The quadrupole coupling of the nuclei to the electric field gradient tensor in the target crystal converts this (dipolar) polarization partly into a (quadrupolar) alignment, which can be measured by the anisotropy of the-ray emission in a succeeding nuclear transition. The sign of the alignment created in this reorientation process depends on the sign of the electric quadrupole interaction. The reorientation effect can be enhanced by selective induction of nuclear magnetic resonance transitions. The method has been applied to measure the sign of the crystal electric field gradient (efg) in tetragonal MgF2. Further, the sign of an efg in cubic CaF2 originating from a19F interstitial adjacent to the activated20F probe nucleus has been determined. The method is in principle applicable to a considerable number of nuclides. 相似文献
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Markus Follmann Nils Griebenow Michael G. Hahn Ingo Hartung Franz‐Josef Mais Joachim Mittendorf Martina Schfer Hartmut Schirok Johannes‐Peter Stasch Friederike Stoll Alexander Straub Peter Jeschke Ralf Nauen Michael Edmund Beck Hans‐Wilhelm Engels Hans‐Georg Pirkl Reinhard Albers Rolf W. Albach Jens Krause Andreas Hoffmann Holger Casselmann Jeff Dormish 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2013,125(36):9503-9503
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Dr. Kai-Stephan Feichtner Dr. Lennart T. Scharf Dr. Thorsten Scherpf Dr. Bert Mallick Nils Boysen Prof. Dr. Viktoria H. Gessner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(69):17351-17360
The use of iminophosphoryl-tethered ruthenium carbene complexes to activate secondary phosphine P−H bonds is reported. Complexes of type [(p-cymene)-RuC(SO2Ph)(PPh2NR)] (with R = SiMe3 or 4-C6H4−NO2) were found to exhibit different reactivities depending on the electronics of the applied phosphine and the substituent at the iminophosphoryl moiety. Hence, the electron-rich silyl-substituted complex undergoes cyclometallation or shift of the imine moiety after cooperative activation of the P−H bond across the M=C linkage, depending on the electronics of the applied phosphine. Deuteration experiments and computational studies proved that cyclometallation is initiated by the activation process at the M=C bond and triggered by the high electron density at the metal in the phosphido intermediates. Consistently, replacement of the trimethylsilyl (TMS) group by the electron-withdrawing 4-nitrophenyl substituent allowed the selective cooperative P−H activation to form stable activation products. 相似文献
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