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1.
Janine C. Swarbrick 《Applied Surface Science》2006,252(15):5622-5626
We have used the established technique of electrospray in developing a portable vacuum electrospray system which can deposit, in vacuo, dissolved molecules onto a sample which may then be analysed by UHV techniques. As an initial test of the system we have analysed silicon samples with an electrosprayed layer of poly(ethylene) oxide (PEO) using atomic force microscopy (AFM). The polymer forms different structures depending on the voltage applied to the emitter, and solution composition. The system is part of our ongoing effort to deposit other materials such as nanoparticles, and large dye molecules for developing molecular dye sensitised solar cells. 相似文献
2.
Cossy J 《Chemical record (New York, N.Y.)》2005,5(2):70-80
The synthesis of optically active substituted piperidines has been achieved by using four different methodologies. The first one is an intramolecular nucleophilic displacement of activated alcohol moieties that was used to build up the piperidine ring of (-)-prosophylline and (-)-slaframine, and the second one is a ring-closing metathesis of unsaturated amines which was employed in the synthesis of (+)-sedamine and 4a,5-dihydrostreptazoline. The third methodology is the alpha-functionalization of N-Boc piperidines which was particularly useful in the synthesis of argatroban, and the fourth one is a ring expansion of prolinols to 3-chloropiperidines or 3-hydroxypiperidines which was utilized to synthesize (-)-paroxetine, (-)-pseudoconhydrine, the piperidine ring of (-)-velbanamine and (+)-zamifenacin. 相似文献
3.
B. Bastian T. P. Knepper P. Hoffmann H. M. Ortner 《Fresenius' Journal of Analytical Chemistry》1994,348(10):674-679
A method for the identification and quantification of aromatic sulfonic acids in industrial waste water has been developed. The preparation of the samples comprises a clean-up step and an enrichment step, utilizing i) reversed-phase extraction and ii) ion-pair solid phase extraction. The aromatic sulfonic acids are separated by ion-pair chromatography with diode-array detection. An advantage of the developed ion-pair chromatographic method is the separation of linear alkylbenzenesulfonic acids (LAS), lignosulfonic acids and aromatic sulfonic acids in one chromatographic run. Also described is an optimized clean-up procedure for collected fractions of a preparative chromatographic run to identify monosulfonic acids with GC/MS after methylation. The detection limits for aromatic sulfonic acids in industrial waste waters are at the g/l level. 相似文献
4.
5.
The synthesis of (−)-colletol was achieved from (R)-pent-4-en-2-ol by using enantioselective allyltitanations to control the stereogenic centers at C5 and cross-metathesis, ring-closing metathesis reactions to control the configuration of the double bonds. 相似文献
6.
The enantioselective monoreduction of 2-alkyl 1,3-diketones by dynamic kinetic resolution using optically active ruthenium catalysts allowed the preparation of the C14-C25 fragment of bafilomycin A1. 相似文献
7.
Photoreduction of ketones in the presence of amines led to ketyl radicals through photoinduced electron transfer (PET). Tertiary amines, such as triethylamine (Et3N) have frequently been used in these reactions. Different reactions can occur from ketyl radicals such as photoreduction, coupling reactions, additions on activated double bonds, cyclizations, bond cleavage of strained rings, tandem reactions such as cyclization-ring opening or ring opening-cyclization. 相似文献
8.
Meier H Gerold J Kolshorn H Mühling B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(2):360-370
Four OPV series 1-4 (a-d) with a terminal dialkylamino group as electron donor were prepared by Wittig-Horner reactions. To study the influence of the push-pull effect on the long-wavelength absorption, three of the four series contained terminal acceptor groups (CN, CHO, NO(2)). The length of the chromophores strongly affects the intramolecular charge transfer (ICT)-an effect which superimposes upon the extension of the conjugation. Increasing numbers n of repeat units cause an overall bathochromic shift for the purely donor-substituted series 1 a-4 a and the series 1 b-4 b with CN as weak acceptor. The two effects annihilate each other in the series 1 c-4 c with terminal CHO groups, so that the absorption maxima are almost independent of the length of the chromophore. A hypsochromic shift is observed for the series 1 d-4 d, which contains the strong acceptor group NO(2). This anomaly disappears on protonation of the dialkylamino group because the push-pull effect disappears in the ammonium salts. The results can be explained by semiempirical quantum mechanics (AM1, INDO/S). The HOMO-LUMO transition, which is mainly responsible for the ICT, becomes less important in the electron transitions S(0)-->S(1) when the distance between donor and acceptor is increased. The commonly used VB model, which contains an electroneutral and a zwitterionic resonance structure, is contrasted with a MO model with dipole segments at both ends of the OPV chains. The latter model turned out to be more appropriate-at least for donor-acceptor-substituted OPVs with n >/= 2. 相似文献
9.
[reaction: see text]. A convergent total synthesis of the methyl ester of zincophorin, an ionophore antibiotic, has been realized relying on a diastereoselective titanium-mediated aldol coupling between the C1-C12 and C13-C25 subunits. The latter fragment was prepared by using a Carroll-Claisen rearrangement. 相似文献
10.
Claude Peker Michel Herlem et Janine Badoz-Lambling 《Fresenius' Journal of Analytical Chemistry》1966,224(1):302-309
Résumé L'évolution de la rapidité de la réduction électrochimique des ions Co2+, Ni2+, Pb2+, In3+ et Zn2+ dans plusieurs milieux complexants a d'abord été étudiée: l'élongation et l'étalement des pics obtenus sont donnés pour une concentration 10–5 M pour chaque ion. Ensuite la résolution des couples Zn2+/Co2+, Zn2+/Ni2+, In3+/Cd2+ et Pb2+/Tl+ a été considérée dans les mêmes milieux complexants. Pour chaque couple on donne la différence E entre les potentiels de demi-vague des éléments et l'allure des polarogrammes.
En hommage au Prof. Dr. M. von Stackelberg à l'occasion de son 70ème anniversaire.
Associé au Centre National de la Recherche Scientifique. 相似文献
Summary The electrochemical reduction rate of the ions Co2+, Ni2+, Pb2+, In3+ and Zn2+ is studied in solutions of various complexing agents. The width and the shape of the peaks for each ion in 10–5 M concentration are given. The resolution of the couples Zn2+/Co2+, Zn2+/Ni2+, In3+/Cd2+ and Pb2+/Tl+ in the same electrolytes is shown hereafter. The difference E of the half-wave potentials and the behaviour of the polarograms for each couple is given.
Zusammenfassung Die Abhängigkeit der elektrochemischen Reduktionsgeschwindigkeit von verschiedenen Komplexbildnern wird am Beispiel der Ionen Co2+, Ni2+, Pb2+, In3+ und Zn2+ untersucht. Ausdehnung und Form der Polarogramme werden für jedes Element in 10–5 m Lösung angegeben. In den gleichen komplexbildenden Elektrolyten wird sodann die Trennung der Ionen Zn2+/Co2+, Zn2+/Ni2+, In3+/Cd2+ und Pb2+/Tl+ untersucht. Für jede Ionenkombination wird die Halbstufenpotentialdifferenz E angegeben und das Polarogramm erläutert.
En hommage au Prof. Dr. M. von Stackelberg à l'occasion de son 70ème anniversaire.
Associé au Centre National de la Recherche Scientifique. 相似文献