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61.
Peter Sawatzki Thomas Mikeska Martin Nieger Michael Bolte Thomas Kolter 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(5):o225-o227
The title compound, C18H35NO4, is a new bioactive amphiphilic lipid with a cis‐substituted 1,3‐oxazolidin‐2‐one head group. In the crystal structure, the molecules form intercalating bilayers in which the oxazolidinone head groups are joined together by hydrogen bonds into chains. 相似文献
62.
Influence of the Ring Atoms on the Structure of Triel‐Pentel Heterocycles – Synthesis and X‐Ray Crystal Structures of [Me2InAs(SiMe3)2]2 and [Me2InSb(SiMe3)2]3 Triel‐pentel heterocycles [Me2InE(SiMe3)2]x have been prepared by dehalosilylation reactions from Me2InCl and E(SiMe3)3 (E = As, x = 2; E = Sb, x = 3) and characterised by NMR spectroscopy and by X‐ray crystal structure analyses. In addition the X‐ray crystal structures of [Me2GaAs(SiMe3)2]2 and [Me2InP(SiMe3)2]2 are reported. The compounds complete a family of 13 identically substituted heterocycles [Me2ME(SiMe3)2]x (M = Al, Ga, In; E = N, P, As, Sb, Bi; x = 2, 3), whose structures were investigated depending on the ring atoms M and E. The tendencies that have been observed concerning the ring sizes can be explained by the interplay of the atomic radii of the central atoms and the sterical demand of the ligands. After a formal separation of the M–E bonds in σ bonds and dative bonds the characteristic differences and trends in the endocyclic and exocyclic bond angles of both centres M and E can be interpreted on the basis of a simple Lewis acid/base adduct model. 相似文献
63.
Edgar Niecke Andr Fuchs Martin Nieger 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》1999,111(20):3213-3216
64.
Claudine Nicole Herlan Anna Sonnefeld Thomas Gloge Julian Brückel Luisa Chiara Schlee Claudia Muhle-Goll Martin Nieger Stefan Brse 《Molecules (Basel, Switzerland)》2021,26(15)
Outstanding affinity and specificity are the main characteristics of peptides, rendering them interesting compounds for basic and medicinal research. However, their biological applicability is limited due to fast proteolytic degradation. The use of mimetic peptoids overcomes this disadvantage, though they lack stereochemical information at the α-carbon. Hybrids composed of amino acids and peptoid monomers combine the unique properties of both parent classes. Rigidification of the backbone increases the affinity towards various targets. However, only little is known about the spatial structure of such constrained hybrids. The determination of the three-dimensional structure is a key step for the identification of new targets as well as the rational design of bioactive compounds. Herein, we report the synthesis and the structural elucidation of novel tetrameric macrocycles. Measurements were taken in solid and solution states with the help of X-ray scattering and NMR spectroscopy. The investigations made will help to find diverse applications for this new, promising compound class. 相似文献
65.
Densely substituted hydroquinoid phenanthrene ( 10 – 18 ), acephenanthrene ( 19 ), and triphenylene chromium tricarbonyl complexes ( 20 – 22 ) have been prepared via benzannulation of naphthalenyl ( 1 – 7 ), acenaphthenyl ( 8 ) and phenanthrenyl carbene complexes ( 9 ), respectively. The naphthalenyl, acenaphthenyl and phenanthrenyl carbene complexes 1 – 9 were obtained in 52–88 % yield starting from commercially available bromoarenes by dehalolithiation, addition of hexacarbonyl chromium to the lithioarene and O‐alkylation of the resulting acyl chromates with trimethyloxonium tetrafluoroborate (Fischer route). The benzannulation of the aryl carbene complexes (either with 3‐hexyne / (t‐butyl)dimethylsilyl chloride or with (t‐butyl)dimethylsilylethyne) allowed the regiospecific synthesis of the oligocyclic hydroquinoid arene tricarbonyl chromium complexes 10 – 22 in 44–94 % yield thus providing a two‐step synthesis with overall yields of 18 ‐ 80 %. Under the kinetic reaction conditions used the metal atom is exclusively coordinated to the persubstituted terminal hydroquinoid ring. The molecular structures of phenanthrene complexes 10 , 12 – 14 , and 16 , acephenanthrene complex 19 , and triphenylene complexes 20 and 21 in the solid state have been determined by X‐ray crystallography. The carbonyl ligands either adopt an eclipsed ( 10 , 12 , 14 , 16 , 19 , 20 ) or staggered ( 13 , 21 ) exo‐conformation pointing away from the center of the phenanthrene, acephenanthrene and triphenylene ligands, respectively. The coordination of the metal atom to the hydroquinoid ring is unsymmetric with the largest metal‐carbon distances found between the chromium atom and one bridgehead carbon and the ring carbon atom bearing the bulky (t‐butyl)dimethylsilyloxy (TBDMSO) substituent. 相似文献
66.
Burck S Gudat D Nieger M Du Mont WW 《Journal of the American Chemical Society》2006,128(12):3946-3955
P-Hydrogen-substituted 1,3,2-diazaphospholenes 1 were prepared by an improved procedure from diazadienes and were characterized by spectroscopy and in one case by X-ray diffraction. A unique hydride-type reactivity of the P-H bonds was documented by extensive reactivity studies. Aldehydes and ketones were readily reduced to diazaphospholene derivatives of the corresponding alcohols, with alkyl-substituted ketones being converted at much lower rates than aldehydes or diaryl ketones. Reactions with the tetrachlorides of group 14 elements proceeded via hydride/chloride metathesis to give either partially chlorinated derivatives EH(n)Cl(4-n) (n = 0-3 for E = C, Si) or HCl and phosphenium salts 16c[ECl3] (for E = Ge, Sn) which were characterized by spectroscopic and X-ray diffraction studies. Tin dichloride was readily reduced to the element. Reactions of 1c with the P-chloro-diazaphospholene 3c and the salt 16c[OTf] allowed the first experimental detection of intermolecular exchange of a hydride, rather than a proton, between phosphine derivatives. Computational studies indicated that the hydride transfer between 1c and the cation 16c involves a transient H-bridged species with bonding properties similar to those of B2H7-. The preference for the formation of these bridged intermediates over P-P bonded phosphenium-phosphine adducts is attributed to the low electrophilicity of the diazaphospholenium cations and characterizes a novel reaction mode for phosphenium ions. 相似文献
67.
Nising CF Ohnemüller UK Friedrich A Lesch B Steiner J Schnöckel H Nieger M Bräse S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(13):3647-3654
Tetrahydroxanthenones, which can be easily prepared by a domino oxa-Michael aldol condensation, offer various possibilities for diastereoselective functionalization, giving access to the stereocontrolled synthesis of stereochemical triades or tetrades, which represent privileged structural motifs. In most cases, the relative stereochemistry was unequivocally established by crystal structure analysis. 相似文献
68.
Alaa A. Hassan Fathy F. Abdel‐Latif Mohamed Abdel‐Aziz Sara M. Mostafa Stefan Bräse Martin Nieger 《Journal of heterocyclic chemistry》2016,53(2):633-636
New series of substituted aminothiadiazolylhydrazonoindolin‐2‐ones were prepared in high yields (89–94%) via the cyclocondensation of thiocarbonohydrazides ( 1a , 1b , 1c , 1d ) with 3‐(dicyanomethylene)‐2‐indolone in (ethanol/piperidine) at room temperature. Explanations of these conversations involve the nucleophilic addition on the dicyanomethylene carbon atom. The structures were established by spectroscopic data and single crystal X‐ray crystallography. 相似文献
69.
70.