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991.
992.
Ohne Zusammenfassung 相似文献
993.
Daniel Bischof Dr. Matthias W. Tripp Dr. Philipp E. Hofmann Chun-Ho Ip Dr. Sergei I. Ivlev Prof. Dr. Marina Gerhard Prof. Dr. Ulrich Koert Prof. Dr. Gregor Witte 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(7):e202103653
Optoelectronic properties of molecular solids are important for organic electronic devices and are largely determined by the adopted molecular packing motifs. In this study, we analyzed such structure-property relationships for the partially regioselective fluorinated tetracenes 1,2,12-trifluorotetracene, 1,2,10,12-tetrafluorotetracene and 1,2,9,10,11-pentafluorotetracene that were further compared with tetracene and perfluoro-tetracene. Quantum chemical DFT calculations in combination with optical absorption spectroscopy data show that the frontier orbital energies are lowered with the degree of fluorination, while their optical gap is barely affected. However, the crystal structure changes from a herringbone packing motif of tetracene towards a planar stacking motif of the fluorinated tetracene derivatives, which is accompanied by the formation of excimers and leads to strongly red-shifted photoluminescence with larger lifetimes. 相似文献
994.
Lisa Gamperl Otto E. O. Zeman Dr. Philipp Strobel Dr. Peter J. Schmidt Prof. Dr. Wolfgang Schnick 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(4):e202104007
The nitridosilicate CaLu[Si4N7–2xCxOx] (x≈0.3) was synthesized by carbothermal reduction and nitridation starting from CaH2, Lu2O3, graphite and amorphous Si3N4 at 1550 °C in a radiofrequency furnace. CaLu[Si4N7–2xCxOx] (x≈0.3) crystallizes isotypically to many previously known MIIMIIISi4N7 compounds in the space group P63mc, as was confirmed by Rietveld refinement based on powder X-ray diffraction data. Incorporation of carbon into the crystal structure as a result of the carbothermal synthesis route was confirmed by 13C and 29Si MAS NMR spectroscopy. For the first time in the MIIMIIISi4N7 compound class, complementary EDX measurements suggest that simultaneous incorporation of oxygen compensates for the negative charge excess induced by carbon, resulting in an adjusted sum formula, CaLu[Si4N7–2xCxOx] (x≈0.3). When excited with UV-to-blue light, CaLu[Si4N7–2xCxOx] (x≈0.3) shows an emission maximum in the blue spectral region (λem=484 nm; fwhm=4531 cm−1) upon doping with Ce3+, whereas Eu2+-doped CaLu[Si4N7–2xCxOx] (x≈0.3) exhibits a yellow-green emission (λem=546 nm; fwhm=3999 cm−1). 相似文献
995.
Dr. Julian Hofmann Philipp Spatz Rasmus Walther Dr. Marcus Gutmann Dr. Tangui Maurice Prof. Dr. Michael Decker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(39):e202200786
Flavonoids are polyphenolic natural products and have shown significant potential as disease-modifying agents against neurodegenerative disorders like Alzheimer's disease (AD), with activities even in vivo. Hybridization of the natural products taxifolin and silibinin with cinnamic acid led to an overadditive effect of these compounds in several phenotypic screening assays related to neurodegeneration and AD. Therefore, we have exchanged the flavonoid part of the hybrids with different flavonoids, which show higher efficacy than taxifolin or silibinin, to improve the activity of the respective hybrids. Chemical connection between the flavonoid and cinnamic acid was realized by an amide instead of a labile ester bond to improve stability towards hydrolysis. To investigate the influence of a double bond at the C-ring of the flavonoid, the dehydro analogues of the respective hybrids were also synthesized. All compounds obtained show neuroprotection against oxytosis, ferroptosis and ATP-depletion, respectively, in the murine hippocampal cell line HT22. Interestingly, the taxifolin and the quercetin derivatives are the most active compounds, whereby the quercetin derivate shows even more pronounced activity than the taxifolin one in all assays applied. As aimed for, no hydrolysis product was found in cellular uptake experiments after 4 h whereas different metabolites were detected. Furthermore, the quercetin-cinnamic acid amide showed pronounced activity in an in vivo AD mouse model at a remarkably low dose of 0.3 mg/kg. 相似文献
996.
Philipp Schüler Simon Sengupta Dr. Alexander Koch Dr. Helmar Görls Dr. Sven Krieck Prof. Matthias Westerhausen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(58):e202201897
The in situ Grignard Metalation Method (iGMM) is a straightforward one-pot strategy to synthesize alkaline-earth metal amides in multi-gram scale with high yields via addition of bromoethane to an ethereal suspension of a primary or secondary amine and magnesium (Part I) or calcium (Part II). This method is highly advantageous because no activation of calcium is required prior to the reaction. Contrary to the magnesium-based iGMM, there are some limitations, the most conspicuous one is the large influence of steric factors. The preparation of Ca(hmds)2 succeeds smoothly within a few hours with excellent yields opening the opportunity to prepare large amounts of this reagent. Side reactions and transfer of the iGMM to substituted anilines and N-heterocycles as well as other H-acidic substrates such as cyclopentadienes are studied. Bulky amidines cannot be converted directly to calcium amidinates via the iGMM but stoichiometric calciation with Ca(hmds)2 enables their preparation. 相似文献
997.
Bianca Seidler Jens H. Tran Julian Hniopek Philipp Traber Dr. Helmar Görls Prof. Dr. Stefanie Gräfe Prof. Dr. Michael Schmitt Prof. Dr. Jürgen Popp Dr. Martin Schulz Prof. Dr. Benjamin Dietzek-Ivanšić 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(72):e202202697
In this paper, the photophysical behavior of four panchromatically absorbing, homoleptic bis(4H-imidazolato)CuI complexes, with a systematic variation in the electron-withdrawing properties of the imidazolate ligand, were studied by wavelength-dependent time-resolved femtosecond transient absorption spectroscopy. Excitation at 400, 480, and 630 nm populates metal-to-ligand charge transfer, intraligand charge transfer, and mixed-character singlet states. The pump wavelength-dependent transient absorption data were analyzed by a recently established 2D correlation approach. Data analysis revealed that all excitation conditions yield similar excited-state dynamics. Key to the excited-state relaxation is fast, sub-picosecond pseudo-Jahn-Teller distortion, which is accompanied by the relocalization of electron density onto a single ligand from the initially delocalized state at Franck-Condon geometry. Subsequent intersystem crossing to the triplet manifold is followed by a sub-100 ps decay to the ground state. The fast, nonradiative decay is rationalized by the low triplet-state energy as found by DFT calculations, which suggest perspective treatment at the strong coupling limit of the energy gap law. 相似文献
998.
It will be shown with the help of the Birman-Schwinger principle that the non-real spectrum of the singular indefinite Sturm-Liouville operator sgn(·)(−d2/dx2 + q) with a real potential q ∈ L1 ∩ L2 is contained in a circle around the origin with radius . (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
999.
In the present work, a comparison of the results of a microscale continuum and a dipolar mean-field approach with regard to their predictions for the magnetostrictive response of magnetorheological elastomers is presented. It turns out that – for random, isotropic microstructures – there is a very good agreement between both modeling strategies. This is in contrast to former comparisons of continuum and other dipole approaches, which have shown considerable deviations. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
1000.
Many modern high-performance materials have inherent anisotropic elastic properties and its local material orientation can be considered to be an additional design variable for the topology optimization [1–3]. We extend our previous model for topology optimization with variational controlled growth [4–6] for linear elastic anisotropic materials, for which the material orientation is introduced as an additional design variable. We solve the optimization problem purely with the principles of thermodynamics by minimizing the Gibbs energy. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献