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661.
An artificial operon was synthesized, consisting of the genes for chorismate pyruvate-lyase of E. coli and for 4-hydroxybenzoate 3-hydroxylase of Corynebacterium cyclohexanicum. This operon, directing the biosynthesis of 3,4-dihdroxybenzoate, was expressed in the heterologous expression host Streptomyces coelicolor M512, together with a modified biosynthetic gene cluster for the aminocoumarin antibiotic clorobiocin. The resulting strain produced a clorobiocin derivative containing a 3,4-dihdroxybenzoyl moiety. Its structure was confirmed by MS and NMR analysis, and it was found to be a potent inhibitor of the gyrases from Escherichia coli and Staphylococcus aureus. Bioassays against different E. coli mutants suggested that this compound is actively imported by catechol siderophore transporters in the cell envelope. This study provides an example of the structure of a natural product that can be rationally modified by synthetic biology. 相似文献
662.
663.
Max Herberhold Silke Gerstmann Und Bernd Wrackmeyer 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):273-283
Abstract Reactions of the salts K2SN2 and K[(NSN)R] (R = ′Bu, SiMe3 and P′Bu2) with organoelement chlorides R′R′ěl have been used to prepare four series of model sulfur diimides: R′R″E(NSN)ER″R′, ′Bu(NSN)ER″R′, Me3Si(NSN)E″R′ and tBu2P(NSN)ER″R′, respectively (E = C, Si, Ge, Sn; R′ and R″ = alkyl or aryl group). All compounds have been characterized by ′H and 13C NMR and—if possible—by 31P, 29Si and 119Sn NMR spectroscopy. The configuration (Z or E) of the substituents R and E″R′ has been assigned in several cases using tBu(NSN)tBu (1) as a reference. The E,Z assignment of 1H, 13C and 15N nuclei in 1 is based on selectively 1H-decoupled refocused INEPT 15N NMR and two-dimensional (2D) 13C/1H heteronuclear shift correlations. The sulfur diimides under study are in general fluxional in solution. 相似文献
664.
We have developed a method for quantification of a specific monoclonal IgM directed toward embryonic stem cells based on a peptide affinity monolith. A peptide affinity ligand with the sequence C-C-H-Q-R-L-S-Q-R-K was obtained by epitope mapping using peptide SPOT synthesis. The peptide ligand was covalently immobilized by coupling the N-terminal cysteine to a monolithic disk that was previously modified with iodated spacer molecules. The monolithic disc was used for quantification of purified IgM and for IgM present in mammalian cell culture supernatant. We observed 17% unspecific binding of IgM to the monolithic disk and additionally a product loss in the flow through of 20%. Nevertheless, calibration curves had high correlation coefficients and inter/intra-assay variability experiments proved sufficient precision of the method. A limit of quantification of 51.69 μg/mL for purified IgM and 48.40 μg/mL for IgM in cell culture supernatant could be calculated. The binding capacity was consistent within the period of the study which included more than 200 cycles. The analysis time of less than 2 min is an advantage over existing chromatographic methods that rely on pore diffusion. 相似文献
665.
Xu X Lu H Ruppel JV Cui X Lopez de Mesa S Wojtas L Zhang XP 《Journal of the American Chemical Society》2011,133(39):15292-15295
3,5-Di(t)Bu-QingPhyrin, a new D(2)-symmetric chiral porphyrin derived from a chiral cyclopropanecarboxamide containing two contiguous stereocenters, has been developed using an iterative approach based on Co(II)-catalyzed asymmetric cyclopropanation of alkenes. The Co(II) complex of 3,5-Di(t)Bu-QingPhyrin, [Co(P2)], has proved to be a general and effective catalyst for asymmetric intramolecular cyclopropanation of various allylic diazoacetates (especially including those with α-acceptor substituents) in high yields with excellent stereoselectivities. The [Co(P2)]-based intramolecular metalloradical cyclopropanation provides convenient access to densely functionalized 3-oxabicyclo[3.1.0]hexan-2-one derivatives bearing three contiguous quaternary and tertiary chiral centers with high enantiomeric purity. 相似文献
666.
667.
H. Behrens 《Fresenius' Journal of Analytical Chemistry》1904,43(1):56
Ohne Zusammenfassung 相似文献
668.
H. Behrens 《Fresenius' Journal of Analytical Chemistry》1900,39(2):106-107
Ohne Zusammenfassung 相似文献
669.
Ernst-August Behrens 《Mathematische Annalen》1941,118(1):85-93
Ohne Zusammenfassung 相似文献
670.
Ernst-August Behrens 《Mathematische Zeitschrift》1961,76(1):367-384
Ohne Zusammenfassung 相似文献