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22.
Andrea Hartwig Leon Mullenders Monika Asmu? Heike Dally M. Hartmann 《Fresenius' Journal of Analytical Chemistry》1998,361(4):377-380
Based on pronounced enhancing effects in combination with other DNA-damaging agents the potentials of Ni(II), Cd(II) and
As(III) to interfere with DNA repair processes in HeLa cells was investigated. With respect to oxidative DNA damage, Ni(II)
and Cd(II) induced DNA strand breaks starting at concentrations of 250 μM and 5 μM, respectively. The induction of oxidative
DNA base modifications like 8-hydroxyguanine was restricted to the cytotoxic concentration of 750 μM Ni(II) and not observed
after treatment with Cd(II). In contrast, the removal of oxidative DNA base modifications was inhibited at concentrations
as low as 50 μM Ni(II) and 0.5 μM Cd(II). Regarding nucleotide excision repair, Ni(II) and Cd(II) disturbed the DNA-protein
interactions involved in the damage recognition step when applying HeLa nuclear protein extracts and a UV-damaged oligonucleotide,
while As(III) inhibited the actual incision event. In the case of Ni(II) and Cd(II), this effect was reversible by the addition
of Mg(II) and Zn(II), respectively. Furthermore, Cd(II) inactivated the isolated bacterial Fpg protein, most likely by the
displacement of Zn(II) from its zinc finger structure. Since DNA is continuously damaged by exogenous and endogenous sources,
an impaired repair capacity might well account for the carcinogenic action of the metal compounds.
Received: 30 July 1997 / Revised: 6 October 1997 / Accepted: 10 October 1997 相似文献
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Zusammenfassung Die optisch aktiven Methylcymantren-- und--carbonsäuren bekannter Absolutkonfiguration wurden auf dem Weg: COClCON3NH2Hal in die entsprechenden Chlor-, Brom- und Jod-methylcymantrene umgewandelt, und dieORD der genannten Verbindungen sowie die Drehungen der Methylcymantrenylisocyanate (dargestellt aus den Aziden) gemessen. In den Halogen-methylcymantrenen liegen optisch aktive Metallocene vor, bei denen der Beitrag zur Drehung nur aus der Atomchiralität stammen kann, während bei den anderen Methylcymantrenderivaten auch die Konformationschiralität einen Beitrag leistet. Entsprechend sind die [M]D-Werte der Halogen-methylcymantrene proportional den Polarisierbarkeiten von Hal. DieNMR-Daten der neuen Cymantrenderivate werden mitgeteilt und kurz diskutiert.
Mit 3 Abbildungen
16. Mitt.:H. Falk undK. Schlögl, Mh. Chem.99, 578 (1968).
a) 3. Mitt.:Heike Gowal undK. Schlögl, Mh. Chem.99, 267 (1968); b) 2. Mitt.:Heike Gowal undK. Schlögl, Mh. Chem.98, 2302 (1967); c) 1. Mitt.:S. G. Cottis, H. Falk undK. Schlögl, Tetrahedron Letters [London]1965, 2857. 相似文献
The optically active methylcymantrene-- and--carboxylic acids of known absolute configuration were converted into the corresponding chloro, bromo and iodo methylcymantrenesvia their chlorides, azides and amines. TheORD of these cymantrene derivatives as well as the rotations of methylcymantrenyl isocyanates (prepared from the azides) are reported. The halogen methylcymantrenes represent optically active metallocenes, in which the contribution to the optical rotations originates only from atomic chirality, whilst in the case of the other methylcymantrene derivatives the conformational chirality also contributes. Correspondingly, the [M]D values of the halogen methylcymantrenes are proportional to the polarizibilities of Hal. TheNMR data of the new cymantrene derivatives are reported and briefly discussed.
Mit 3 Abbildungen
16. Mitt.:H. Falk undK. Schlögl, Mh. Chem.99, 578 (1968).
a) 3. Mitt.:Heike Gowal undK. Schlögl, Mh. Chem.99, 267 (1968); b) 2. Mitt.:Heike Gowal undK. Schlögl, Mh. Chem.98, 2302 (1967); c) 1. Mitt.:S. G. Cottis, H. Falk undK. Schlögl, Tetrahedron Letters [London]1965, 2857. 相似文献
26.
Synthesis of New Chiral C2-Symmetrical Bis(oxazoline )Compounds 总被引:2,自引:0,他引:2
New chiral C2-symmetrical bis(oxazoline)compounds bearing one isobutyl-,secbutyl-benzyl- or isopropyl-substituent at the 4-position have been prepared and characterized. 相似文献
27.
The electrochemical oxidation of 6-hydroxy-1,2,3,4-tetrahydro-β-carboline (1), an alkaloid which occurs naturally in the mammalian brain, has been studied in aqueous solution particularly at physiological pH. The first voltammetric oxidation peak of 1 observed at the pyrolytic graphite electrode generates a radical intermediate which dimerizes to give 5,5′-bi-(6-hydroxy-1,2,3,4-tetrahydro-β-carboline) (3). However, the putative radical intermediate can also be further oxidized (1e) to give a C(5)-centered carbocation which can either dimerize in an ion-substrate reaction to give 3 or be attacked by water to give 5,6-dihydroxy-1,2,3,4-tetrahydro-β-carboline (8) which is rapidly oxidized further to 1,2,3,4-tetrahydro-β-carboline-5,6-dione (9). In the presence of glutathione dione 9 forms the 8-S-glutathionyl conjugate of 8 which is easily oxidized to the 8-S-glutathionyl conjugate of 9. It is suggested that 1 might be an alkaloid which is elevated in the brain as a result of chronic alcoholism, and the roles of the oxidative transformations of this compound in some of the addictive and neurophathological consequences of ethanol consumption are discussed. 相似文献
28.
Hang GONG Nian Fa YANG? Wei Jun TANG Qing Hua FAN Li Wen YANG The College of Chemistry Xiangtan University Xiangtan Laboratory of Chemical Biology Center for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2005,16(8)
Among the reactions in which C-C bonds are formed, the Baylis-Hillman coupling of aldehydes with α, β-unsaturated carbonylic compounds is currently attracting much interest due to the atom economy, the mild conditions and the generation of functional groups1,2. Furthermore, compared to the Heck, Suzuki and other palladium catalyzed C-C bond forming reaction3, the Baylis-Hillman reaction can be promoted by using organic bases in the complete absence of any metal4. However, almost all the … 相似文献
29.
Barluenga J Diéguez A Rodríguez F Flórez J Fañanás FJ 《Journal of the American Chemical Society》2002,124(31):9056-9057
Eight-membered carbocycles with up to five new stereogenic centers are enantioselectively obtained following a one-pot procedure that involves the coupling of three components: an alkenyl Fischer carbene complex, a ketone enolate, and allyl lithium. 相似文献
30.
Syntheses, Structure Determination and Reactions of Phosphine Substituted Derivatives of Fe3(CO)9(μ3-CF)2 Photolysis of Fe3(CO)9(μ3-CF)2 1 in the presence of acetonitrile 2a or benzoenitrile 2b results in the substitution of a single carbonyl ligand by a nitrile ligand yielding Fe3(CO)8(CH3CN)(μ3-CF)2 3a and Fe3(CO)8(C6H5CN)(μ3-CF)2 3b, respectively. The acetonitrile ligand in 3a can be easily replaced by trimethyl-phosphine 4a or triphenylphosphine 4b . The monosubstituted compounds Fe3(CO)8(PR3)(μ3-CF)25, R = CH3 a, R = C6H5, b are obtained as major products besides a small amount of the disubsituted products Fe3(CO)7(PR3)2(μ3-CF)2 6. The structure of 5a has been elucidated by a single crystal X-ray structure determination. Thermal ligand substitution in 1, however, results in the formation of a mixture of mono-, disubstituted, and trisubstituted products, in which 6b is the major product for diphenylphosphine. 5a reacts with ethyne 7 forming a phosphine substituted diferra-allyl-cluster Fe3(CO)7(PR3)(μ3-CF)(μ3? CF? CH? CH) 8. The structure of one isomere of 8 has been determinated by X-ray crystallography. 相似文献