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981.
982.
983.
Reductive Carbocyclization of Homoallylic Alcohols to syn‐Cyclobutanes by a Boron‐Catalyzed Dual Ring‐Closing Pathway 下载免费PDF全文
Dr. Chinmoy Kumar Hazra Jinhoon Jeong Hyunjoong Kim Prof. Dr. Mu‐Hyun Baik Dr. Sehoon Park Prof. Dr. Sukbok Chang 《Angewandte Chemie (International ed. in English)》2018,57(10):2692-2696
The organoborane‐catalyzed reductive carbocyclization of homoallylic alcohols has been developed by using hydrosilanes as reducing reagents to provide a range of 1,2‐disubstituted arylcyclobutanes. The reaction proceeds in a cis‐selective manner with high efficiency under mild conditions. Mechanistic studies, including deuterium scrambling and Hammett studies, and DFT calculations, suggest a dual ring‐closing pathway. 相似文献
984.
Haseo Ki 《Transactions of the American Mathematical Society》1997,349(7):2845-2870
We show that the Denjoy rank and the Zalcwasser rank are incomparable. We construct for any countable ordinal differentiable functions and such that the Zalcwasser rank and the Kechris-Woodin rank of are but the Denjoy rank of is 2 and the Denjoy rank and the Kechris-Woodin rank of are but the Zalcwasser rank of is 1. We then derive a theorem that shows the surprising behavior of the Denjoy rank, the Kechris-Woodin rank and the Zalcwasser rank.
985.
986.
The design and synthesis of a new cross-linkable amphiphile is reported. Solutions of the amphiphile in a toluene/water mixture form reverse micelles as indicated by dynamic light scattering and NMR spectroscopy. As indicated by dynamic light scattering, TEM, and NMR spectroscopy data, these reverse micelles can be cross-linked without drastically changing the radius of the reverse micelles. Mixed reverse micelles are also characterized and cross-linked. The cross-linked reverse micelles are demonstrated to facilitate phase transfer and can be used to site isolate a catalyst. 相似文献
987.
D.I. Kim E.H. Kim Z.U. Bae H.G. Na J.H. Choi Y.C. Park 《Journal of inclusion phenomena and macrocyclic chemistry》2004,49(1-2):107-113
The complexes 13,14-([X]benzo)-3-(p-[Y]benzoyl)-2,4,9,11-tetramethyl-1,5,8,12-tetraazacyclotetradeca-l,3,9,11-tetraenato(2-)nickel(II), wherein Y = CH3, H, Cl, NO2 or OCH3, X = CH3 or Cl, have been synthesized and characterized. IR spectra of the benzoylated complexes show intense bands in the regions 1641-1654 cm?1 attributable to the stretching modes of C—O. Hammett plots of the l/γ max of π→π ? have positive slopes of 0.251 for A series (X = CH3) and 0.233 for B series (X = Cl), respectively, which are quite similar to those based on the NMR resonances of methine protons. The cyclic voltammograms of the complexes show two one-electron irreversible oxidation processes in the potential range of +0.1 to +0.8 V and two, three or four reduction peaks between ?1.2 and ?2.8 V depending on the substituents. Hammett plots of first and second oxidation potentials are linear with the positive slopes (0.039 and 0.057 V for A series, 0.036 and 0.047V for B series). The structure of the copper(II) complex (orthorhombic, C2221, a= 8.0994(11), b= 8.3187(10), c= 24.561(5)Å, α(=β=γ)= 90.0°, Z= 4, R 1= 0.0474 and wR 2= 0.1219) was characterized using single crystal X-ray diffraction method. 相似文献
988.
Libuše Kišová 《Monatshefte für Chemie / Chemical Monthly》1970,101(2):484-492
Zusammenfassung Die Wechselstrompolarographie ist für die Messung der Geschwindigkeitskonstanten der Elektrodenprozesse im Bereich von 5·10–3–5·10–2 cm sec–1 anwendbar. Das bestätigen auch die Ergebnisse, die für ein Modellsystem erhalten wurden. Experimentell wurde die Anwendbarkeit der Methode am Redoxsystem [CrCl2(H2O)4]+–[CrCl2(H2O)4] in sauren 4–9n-LiCl-Lösungen nachgeprüft, und zwar durch den Vergleich der Resultate mit den Ergebnissen der Messungen derFaraday-impedanz und der Methode der überlagerten Spannung.
Mit 7 Abbildungen 相似文献
Application of alternating current polarography for the measurement of rate constants
The method of alternating current polarography is known to be applicable to the measurement of rate constants of electrode reactions within the range of 5·10–3 to 5·10–2 cm sec–1. This follows also from the results obtained with model systems. The applicability of the method has been studied in the redox-system [CrCl2(H2O)4]+–[CrCl2(H2O)4] in acid solutions of 4N to 9N LiCl. The results were compared with those obtained by measuring the faradaic impedance and with the results of the method of periodically changed rectangular voltage.
Mit 7 Abbildungen 相似文献
989.
An approach to enhance specificity against RNA targets using heteroconjugates of aminoglycosides and chloramphenicol (or linezolid) 总被引:2,自引:0,他引:2
Lee J Kwon M Lee KH Jeong S Hyun S Shin KJ Yu J 《Journal of the American Chemical Society》2004,126(7):1956-1957
We describe the design and synthesis of new heterodimeric conjugates, which are comprised of a neomycin B (Neo) stem-binding component and a chloramphenicol (Cam) or linezolid (Lnz) loop-binding component. Some of the heterodimeric conjugates display enhanced affinities to RNA targets and that binding occurs in both stem and loop regions of the RNA. In addition, the results of foot-printing and mutation studies suggest that the enhanced binding affinity of the conjugates is RNA sequence-specific. 相似文献
990.
Tocainide and its 14 analogues were resolved on a chiral stationary phase (CSP) based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 covalently bonded to silica gel. The resolution was quite good, the separation (alpha) and resolution factors (Rs) being 1.84-15.32 and 1.34-13.78, respectively. Especially, the result for the resolution of tocainide on the CSP turns out to be the best one among others reported so far. The chromatographic resolution behaviors were demonstrated to be dependent on the content and the type of organic and acidic modifiers and the ammonium acetate concentration in aqueous mobile phase. 相似文献