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991.
Nadine Allefeld Beate Neumann Dr. Hans‐Georg Stammler Prof. Dr. Gerd‐Volker Röschenthaler Dr. Nikolai Ignat'ev Prof. Dr. Berthold Hoge 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(25):7736-7745
A new efficient synthesis of functionalized perfluoroalkyl fluorophosphates by oxidative addition of Me2NCH2F to the electron‐deficient phosphanes (C2F5)nPF3?n (n=0–3) is reported. The initially formed zwitterionic, hexacoordinated phosphates [(C2F5)nF5?nP(CH2NMe2?CH2NMe2)] are converted into the corresponding phosphonium salts [(Me3PCH2NMe2]+[(C2F5)nF5?nP(CH2NMe2)]? by treatment with PMe3. In addition [(C2F5)3F2P(CH2NMe2?CH2NMe2)] can undergo a 1,3‐methyl shift from the internal to the terminal nitrogen—a structural characterization was achieved from the CF3 analogue. Reaction of [(C2F5)3F2P(CH2NMe?CH2NMe3)] and PMe3 gave rise to the formation of the zwitterionic phosphonium phosphate [(C2F5)3F2P(CH2NMe?CH2PMe3)], which was fully characterized by X‐ray diffraction analysis. Moreover, an efficient one‐pot synthesis of Cs+[(C2F5)3F2P(CH2NMe2)]? was pursued. This salt turned out to be a useful nucleophile in several alkylation reactions. 相似文献
992.
A Dehydratase Domain in Ambruticin Biosynthesis Displays Additional Activity as a Pyran‐Forming Cyclase
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Gesche Berkhan Dr. Frank Hahn 《Angewandte Chemie (International ed. in English)》2014,53(51):14240-14244
Hydropyran rings are a common structural motif in reduced polyketides. Information on their biosynthetic formation and particularly the biochemical characterization of the responsible enzymes has only been reported in few cases. The dehydratase domain AmbDH3 from the ambruticin polyketide synthase was investigated. Through in vitro assay of the recombinant domain with synthetically‐derived substrate surrogates, it was shown that it has a second catalytic activity as a cyclase that performs oxa‐conjugate addition. Probing AmbDH3 with synthetic substrate analogues revealed stereoselectivity and substrate tolerance in both substeps. This is the first characterization of a pyran‐forming cyclase from a cis‐AT PKS system and the first report of a polyketide synthase domain with this kind of dual activity. Finally, it was revealed that this domain shows potential for application in chemoenzymatic synthesis. 相似文献
993.
Klaus Diemert Thomas Hahn Wilhelm Kuchen 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):287-294
Abstract Ph 2 PCOONa 2, hergestellt dutch Reaktion von Ph2PNa mit CO2, wird in protischen Medien rasch unter Bildung von Ph2PH and CO2 hydrolysiert. Die Hydrolyse verlauft in Natronlauge sehr viel langsamer and es bilden sich zusätzlich geringe Mengen Ph2P(O)O? und HCOO?, Aus 2 and stöchiometrischen Mengen RI bilden sich tertiäre Phosphine Ph2PR (R[dbnd]Me, Et) während mit überschüssigem MeI das Phosphoniumsalz [Ph2PMe2]I erhalten wird. Ph2PCOOMe, Ph2PCOOSiMe3 bzw. Ph2PCSSNa wurden durch Umsetzung von 2 mit (MeO)2SO2, Me3SiCl bzw. CS2 synthetisiert. Ph2P(O)ONa and Ph2P(S)SNa entstanden bei der Reaktion von 2 mit O2 oder S8 in Benzol. Concerning Sodiumdiphenylphosphinoformiate Ph2PCOONa1. Ph2PCOONa 2, prepared from Ph2PNa and CO2, is readily hydrolyzed in protic media with formation of Ph 2 PH and CO2. Hydrolysis is much slower in NaOH and small quantities of Ph2P(O)O? and HCOO? are additionally formed. Reactions of 2 with RI in stoichiometrical amounts gave tertiary phosphines Ph2PR (R[dbnd]Me, Et) while the phosphonium compound [Ph2PMe2]I resulted from 2 and MeI in excess. Ph2PCOOMe, Ph2PCOOSiMe3 or Ph2PCSSNa were obtained from 2 and (MeO)2SO2, Me3SiCl or CS2. Ph2P(O)ONa and Ph2P(S)SNa were isolated when 2 was reacted with O2 or S8 in benzene. 相似文献
994.
Christian H. G. Jakob Bruno Dominelli Eva M. Hahn Tobias O. Berghausen Teresa Pinheiro Fernanda Marques Robert M. Reich Joo D. G. Correia Fritz E. Kühn 《化学:亚洲杂志》2020,15(17):2754-2762
A series of histidine derived Au(I) bis‐NHC complexes bearing different ester, amide and carboxylic acid functionalities as well as wingtip substituents is synthesized and characterized. The stability in aqueous media, in vitro cytotoxicity in a set of cancer cell lines (MCF7, PC3 and A2780/A2780cisR) along with the cellular uptake are evaluated. Stability tests suggest hydrolysis of the ester within 8 h, which might lead to deactivation. Furthermore, the bis‐NHC system shows a sufficient stability against cysteine and the thiol containing peptide GSH. The benzyl ester and amide show the highest activity comparable to the benchmark compound cisplatin, with the ester only displaying a slightly lower cytotoxicity than the amide. A cellular uptake study revealed that the benzyl ester and the amide could have different intracellular distribution profiles but both complexes induce perturbations of the cellular physiological processes. The simple modifiability and high stability of the complexes provides a promising system for upcoming post modifications to enable targeted cancer therapy. 相似文献
995.
Natalia Tiessen Beate Neumann Dr. Hans-Georg Stammler Prof. Dr. Berthold Hoge 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(60):13611-13614
While perfluorinated aryl, aryloxy and alkoxy aluminum species are well-established as weakly coordinating anions (WCAs), corresponding perfluoroalkyl aluminum derivatives are virtually unknown. Reaction of Si(C2F5)3CH3 with Li[AlH4] afforded the tetrakis(pentafluoroethyl)aluminate, [Al(C2F5)4]−. Several salts of the [Al(C2F5)4]− ion were synthesized and characterized by NMR spectroscopic methods, mass spectrometry, X-ray diffraction studies and elemental analysis. 相似文献
996.
Dr. Brigitte Holzer Barbara Dellago Ann-Katrin Thamm Dr. Thomas Mathis Prof. Berthold Stöger Dr. Ernst Horkel Dr. Christian Hametner Dr. Bertram Batlogg Prof. Johannes Fröhlich Dr. Daniel Lumpi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(13):2869-2882
A reliable synthetic protocol toward a series of fused chalcogenopheno[1]benzochalcogenophene (CBC) building blocks was developed based on a Fiesselmann reaction. The obtained CBC units were applied in McMurry and Stille coupling reactions toward symmetric regioisomeric ene-linked dimers. These π-conjugated compounds were characterized regarding their photophysical and electrochemical properties and proved to be materials with reduced HOMO–LUMO gaps compared to their sulfur-based analogues. Single-crystal X-ray diffraction experiments revealed strong intermolecular selenium–selenium and selenium–carbon interactions depending on the position and number of incorporated selenium atoms. Good field-effect transistor performance with charge carrier mobilities up to 4×10−3 cm2 V−1 s−1 and high on/off ratios could be observed. 相似文献
997.
Dr. Aysun Çapcı Dr. Mélanie M. Lorion Christina Mai Dr. Friedrich Hahn Dr. Jan Hodek Christina Wangen Dr. Jan Weber Prof. Dr. Manfred Marschall Prof. Dr. Lutz Ackermann Prof. Dr. Svetlana B. Tsogoeva 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(52):12019-12026
Viral infections cause life-threatening diseases in millions of people worldwide every year and there is an urgent need for new, effective antiviral drugs. Hybridization of two chemically diverse compounds into a new bioactive effector product is a successful concept to improve the properties of a hybrid drug relative to the parent compounds. In this study, (iso)quinoline–artemisinin hybrids, obtained through copper-catalyzed azide–alkyne cycloaddition or metal-free click reactions (in organic solvents or in the presence of water), were analyzed in vitro, for the first time, for their inhibitory activity against human cytomegalovirus (HCMV), relative to their parent compounds and the reference drug ganciclovir. EC50 (HCMV) values were obtained in a range 0.22–1.20 μm , which indicated highly potent antiviral properties in the absence of cytotoxic effects on normal cells (CC50>100 μm ). The most active hybrid, 1 (EC50=0.22 μm ), is 25 times more potent than its parent compound artesunic acid (EC50=5.41 μm ) and 12 times more efficient than the standard drug ganciclovir (EC50=2.6 μm ). Interestingly, hybrid 1 also shows inhibitory activity against hepatitis B virus in vitro (EC50 (HBeAg)=2.57 μm ). 相似文献
998.
In this research, the image-sticking property of the in-plane switching (IPS)-liquid crystal display (LCD) with residual d.c. voltage on a rubbed polyimide surface was studied. The voltage holding ratio (VHR) and residual d.c. voltage were measured by the capacitance-voltage hysteresis method in the IPS-LCDs. It was found that the VHR increased with increasing specific resistivity of fluorine-containing LCs. The residual d.c. voltage decreased with increasing concentration of cyano-containing LCs. The residual d.c. voltage is thus decreased by the high polarity of cyano-LCs. 相似文献
999.
G Link T Berthold M Bechtold J U Weidner E Ohmes J Tang O Poluektov L Utschig S L Schlesselman M C Thurnauer G Kothe 《Journal of the American Chemical Society》2001,123(18):4211-4222
The geometry of the secondary radical pair P700(+)A1(-), in photosystem I (PSI) from the deuterated and 15N-substituted cyanobacterium Synechococcus lividus, has been determined by high time resolution electron paramagnetic resonance (EPR), performed at three different microwave frequencies. Structural information is extracted from light-induced quantum beats observed in the transverse magnetization of P700(+)A1(-) at early times after laser excitation. A computer analysis of the two-dimensional Q-band experiment provides the orientation of the various magnetic tensors of with respect to a magnetic reference frame. The orientation of the cofactors of the primary donor in the g-tensor system of is then evaluated by analyzing time-dependent X-band EPR spectra, extracted from a two-dimensional data set. Finally, the cofactor arrangement of P700(+)A1(-) in the photosynthetic membrane is deduced from angular-dependent W-band spectra, observed for a magnetically aligned sample. Thus, the orientation of the g-tensor of P700(+) with respect to a chlorophyll based reference system could be determined. The angle between the g1(z) axis and the chlorophyll plane normal is found to be 29 +/- 7 degrees, while the g1(y) axis lies in the chlorophyll plane. In addition, a complete structural model for the reduced quinone acceptor, A1(-), is evaluated. In this model, the quinone plane of is found to be inclined by 68 +/- 7 degrees relative to the membrane plane, while the P700(+)-A1(-) axis makes an angle of 35 +/- 6 degrees with the membrane normal. All of these values refer to the charge separated state, observed at low temperatures, where forward electron transfer to the iron-sulfur centers is partially blocked. Preliminary room temperature studies of P700(+)A1(-), employing X-band quantum beat oscillations, indicate a different orientation of A1(-) in its binding pocket. A comparison with crystallographic data provides information on the electron-transfer pathway in PSI. It appears that quantum beats represent excellent structural probes for the short-lived intermediates in the primary energy conversion steps of photosynthesis. 相似文献
1000.
M. Hahn O. Barbieri F.P. Campana R. Kötz R. Gallay 《Applied Physics A: Materials Science & Processing》2006,82(4):633-638
The extraordinary stability and cycle life performance of today’s electrochemical double-layer capacitors (EDLCs) are generally
ascribed to the fact that charge storage in activated carbon (AC) is based on pure double-layer charging. In contrast, Faradaic
charge-transfer reactions like those occurring in batteries are often connected with dimensional changes, which can affect
the cycle life of these storage devices. Here we report the charge-induced height change of an AC electrode in an aprotic
electrolyte solution, 1 mol/l (C2H5)4NBF4 (TEABF4) in acetonitrile. The results are compared with those obtained for a graphite electrode in the same electrolyte. For both
electrodes, we observe an expansion/contraction of several percent for a potential window of ±2 V vs. the immersion potential
(ip). For the EDLC electrode, significant expansion starts at about 1 V remote from the ip and hence is well within the normal
EDLC operation range. For the graphite electrode, the height changes are unambiguously caused by intercalation/deintercalation
of both anions and cations. The close analogies between the graphite and the EDLC electrode suggest that ion intercalation
or insertion processes might play a major role for charge storage, self discharge, cyclability, and the voltage limitation
of EDLCs.
PACS 82.47.Uv; 82.45.Fk; 82.45.Gj; 82.80.Fk; 81.05.Uw 相似文献