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31.
Guido Galliani Diego Monti Giovanna Speranza Paolo Manitto 《Tetrahedron letters》1984,25(52):6037-6040
Bilin-1,19(21H,24H)-diones interact with O2·- in DMSO giving rise to adducts showing charge-transfer character. This reaction can be reversed by addition of O2·- consuming compounds. The O2·-biliverdin dimethyl ester adduct collapses partially to 10-oxobilirubin dimethyl ester when treated with thiourea and 2-mercaptoethanol. 相似文献
32.
Guido Kickelbick Dieter Rutzinger Thomas Gallauner 《Monatshefte für Chemie / Chemical Monthly》2002,133(8):1157-1164
Summary. Hexadentate ligands were formed by the reaction of primary dimethylaminoethyl- or methoxyethylamines with formaldehyde. The
resulting N, N′, N″-functionalized hexahydro-1,3,5-triazines contain pending amino or ether functionalities which are able to coordinate to
metals in addition to the ring nitrogen atoms. Both ligands were reacted with CuBr, and novel tricopper clusters were isolated
and characterized by X-ray structure analysis. In these compounds a ring nitrogen atom, the pending amino or ether functionality,
and two bridging bromine atoms coordinate each of the copper atoms.
Received January 22, 2002; accepted (revised) March 22, 2002 相似文献
33.
Fries G Wolf J Ilg K Walfort B Stalke D Werner H 《Dalton transactions (Cambridge, England : 2003)》2004,(12):1873-1881
A series of unsymmetrical 1,2-bis(phosphino)ethanes R(2)PCH(2)CH(2)PR'(2) and 1-arsino-2-phosphinoethanes R(2)AsCH(2)CH(2)PR'(2) mainly with bulky substituents R and R' were prepared from the cyclic sulfate by stepwise cleavage of the carbon-oxygen bonds by LiPR(2) and LiPR'(2) or LiAsR(2) and LiPR'(2), respectively. Analogously, racemic mixtures of R(2)PCH(2)CH(Me)PPh(2)(R =iPr, Cy ) as well as the enantiomers (R)-, (R)- and (R)-tBu(2)PCH(2)CH(Me)PPh(2)(R)- were obtained from the corresponding unsymmetrical cyclic sulfates and (S)-. On a similar route, the racemates of the 1,3-bis(phosphino)propanes R(2)PCH(2)CH(2)CH(Me)PPh(2)(R =iPr, tBu ), optically pure (R)- and (S,S)-iPr(2)PCH(Me)CH(2)CH(Me)PPh(2)(S,S)- were prepared. The reaction of [[RhCl([small eta](4)-C(8)H(12))](2)] with chelating ligands L-L, where L-L is R(2)PCH(2)P(men)(2)(R =iPr, Ph; men =(1S,2R,5S)-menthyl), Cy(2)AsCH(2)P(men)(2), or (R)-, (R)-, (R)-, (R)- and (S,S)-, in the presence of AgPF(6), gave the complexes [Rh(eta(4)-C(8)H(12))(L-L)]PF(6) which were used as pre-catalysts in the hydrogenation of the methyl ester of alpha-acetamidocinnamic acid (ACM). Depending on L-L, the solvent, the temperature and the pressure of H(2), optical yields of up to 69% ee were achieved. For two of the rhodium complexes, and, the molecular structures were determined by X-ray crystallography. 相似文献
34.
Yee AA Savchenko A Ignachenko A Lukin J Xu X Skarina T Evdokimova E Liu CS Semesi A Guido V Edwards AM Arrowsmith CH 《Journal of the American Chemical Society》2005,127(47):16512-16517
NMR spectroscopy and X-ray crystallography, the two primary experimental methods for protein structure determination at high resolution, have different advantages and disadvantages in terms of sample preparation and data collection and analysis. It is therefore of interest to assess their complementarity when applied to small proteins. Structural genomics/proteomics projects provide an ideal opportunity to make such comparisons as they generate data in a systematic manner for large enough numbers of proteins to allow firm conclusions to be drawn. Here we report a comparison for 263 unique proteins screened by both NMR spectroscopy and X-ray crystallography in our structural proteomics pipeline. Only 21 targets (8%) were deemed amenable to both methods based on an initial 2D 15N-HSQC NMR spectrum and optimized crystallization trials. However, the use of both methods in the pipeline increased the total number of targets amenable to structure determination to 107, with 43 amenable to NMR only and 43 amenable to X-ray crystallographic methods only. We did not observe a correlation between 15N-HSQC spectral quality and the success of the same protein in crystallization screens. Similar results were found for an independent set of 159 proteins as reported in the accompanying paper by Snyder et al. Thus, we conclude that both methods are highly complementary, and in order to increase the number of proteins suited for structure determination, we suggest that both methods be used in parallel in screening of all small proteins for structure determination. 相似文献
35.
Two unprecedented degraded sterols, aplykurodinone-1 (1) and -2 (2), have been isolated from the skin of the marine anaspidean Syphonota geographica, collected along the coasts of Greece. The structures and the relative stereochemistry were established by spectroscopic analysis and confirmed by chemical correlation with related known compounds. 相似文献
36.
Simplistic modeling approach to heterogeneous dilute-acid hydrolysis of cellulose microcrystallites 总被引:9,自引:0,他引:9
Pär O. Pettersson Robert W. Torget Robert Eklund Qian Xiang Y. Y. Lee Guido Zacchi 《Applied biochemistry and biotechnology》2003,106(1-3):451-455
The classic kinetic model for cellulose hydrolysis is often referred to as pseudo-homogeneous, a term revealing the insight that the process is actually heterogeneous. During the past 10–15 yr, the shortcomings of this
model have been demonstrated in various studies and the interest in the heterogeneous aspects has increased. The present work
presents a simplistic model in which the intrinsic, heterogeneous hydrolysis and transport rates are coupled by the assumption
of a constant glucosidic surface concentration. The mechanisms affecting these two rates are largely unknown, but the model
serves as a guideline for further exploration of the process. 相似文献
37.
[reaction: see text] Marine diatoms produce alpha,beta,gamma,delta-unsaturated aldehydes that have detrimental effects on the reproduction of their natural predators. The production of these defensive metabolites is suggested to involve enzymatic oxidation of polyunsaturated fatty acids. In this paper, feeding experiments with labeled precursor provide clear evidence in support of the origin of octadienals 1 and 2 from 6,9,12-hexadecatrienoic acid (5), thus proving the involvement of novel lipoxygenase/lyase activity for the oxidation of C(16) fatty acids. 相似文献
38.
Angelo Fontana Adele Cutignano Antonella Giordano Anna Domènech Coll Guido Cimino 《Tetrahedron letters》2004,45(37):6847-6850
The biogenesis of aglajnes, polypropionate allomones of the cephalaspidean mollusc Bulla striata, has been investigated in vivo by feeding experiments. Incorporation of the committed precursor, [1-14C]-propionate, into aglajne-1 (1) and -3 (3) established the de novo origin of these compounds in B. striata. In the letter we also discuss briefly the ecological meaning of the origin of polypropionates in B. striata and in other cephalaspidean molluscs. 相似文献
39.
Guido Audisio Maria Grassi Piero Traldi Sergio Daolio 《Journal of mass spectrometry : JMS》1985,20(5):327-330
The positive ion chemical ionization (CI (isobutane)), negative ion chemical ionization (NICI) electron attachment (CH4, He) and NICI (OH?) spectra of the title compounds have been studied in detail with the aid of deuterium-labelled derivatives. The obtained results show that under CI conditions the stereospecificity is retained. Interesting correlations with the condensed phase epimerization yields are emphasized. 相似文献
40.
Zusammenfassung Bei der C-H-Bestimmung mit Außenabsorption der Stickoxide wurden bei einer Serie stickstoffhaltiger Substanzen zu hohe Wasserstoffwerte erhalten, während sich bei einer zweiten Serie, mit gleichen Atomgruppen, richtige Werte ergaben. Um dieses verschiedene Verhalten erklären zu können, wurden weitere Substanzen dieser Art dargestellt und analysiert. Dabei konnte beobachtet werden, daß Substanzen mit der Atomgruppe bei der Analyse im allgemeinen zu hohe Wasserstoffwerte geben, während die Anwesenheit von Phenylringen oder OH-Gruppen, in und Stellung wieder zu regelmäßigen Wasserstoffwerten führen.Die Darstellung neuer Verbindungen dieser Art wurde beschrieben. In den Verbindungen, die bei der C-H-Bestimmung zu hohe Wasserstoffwerte gaben, wurden zur Identifizierung einerseits der Stickstoff, anderseits C und H nach einer Methode bestimmt, die die Reduktion der Stickoxide vorsieht. Diese wird beschrieben.
Herrn Univ.-Prof. Dr.Hans Lieb zum 80. Geburtstag gewidmet. 相似文献
Summary Too high hydrogen values were obtained in the C-H-determinations, with external absorption of the nitrogen oxides, in a series of nitrogenous substances, whereas a second series with the same atom groups gave correct results. To explain these divergent behaviors, additional substances were prepared and analyzed. It was then observed that substances with the group yielded too high hydrogen values in general, while the presence of phenyl rings or OH-groups in the and-position led again to uniform hydrogen values. The preparation of the new compounds of this kind is described. In the case of the compounds that gave too high hydrogen values in the C-H-determination, identification was made on one hand by determining the nitrogen, on the other hand by determining the carbon and hydrogen by another method that provides for the reduction of the nitrogen oxides. The latter is described.
Herrn Univ.-Prof. Dr.Hans Lieb zum 80. Geburtstag gewidmet. 相似文献