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61.
An unusually high yielding fluorination of aminopyralid (3) using F-TEDA (SELECTFLUOR™) in warm water, followed by kinetic resolution (via iterative esterification/saponification) of the crude fluorination product with dry HCl in methanol produced pure ring-fluorinated pyridine 2 in an overall yield of 31% for the two steps. 相似文献
62.
Silylated functionalized arylboronic acids were converted into corresponding iodinated arylboronic acids in good yields via the electrophilic ipso-desilylation effected with iodine chloride in refluxing CHCl3. Disilylated arylboronic acids were susceptible to diiodination. In addition, the structural characterization and reactivity of a novel sterically hindered ortho-silylated diarylborinic ester were reported. The potential of selected iodinated phenylboronic acids as monomers for the Suzuki-Miyaura cross-coupling polymerization was demonstrated. 相似文献
63.
64.
Emil Byström Anna Nordborg Fredrik Limé Ngoc Phuoc Dinh Knut Irgum 《Journal of separation science》2010,33(11):1563-1570
A combined surface activation and “grafting to” strategy was developed to convert divinylbenzene particles into weak cation exchangers suitable for protein separation. The initial activation step was based on plasma modification with bromoform, which rendered the particles amenable to further reaction with nucleophiles by introducing Br to a surface content of 11.2 atom‐%, as determined by X‐ray photoelectron spectroscopy. Grafting of thiol‐terminated glydicyl methacrylate telomers to freshly plasma activated surfaces was accomplished without the use of added initiator, and the grafting was verified both by reduction in bromine content and the appearance of sulfur‐carbon linkages, showing that the surface grafts were covalently bonded. Following grafting the attached glydicyl methacrylate telomer tentacles were further modified by a two‐step procedure involving hydrolysis to 2,3‐hydroxypropyl groups and conversion of hydroxyl groups to carboxylate functionality by succinic anhydride. The final material was capable of baseline separating four model proteins in 3 min by gradient cation exchange chromatography in a fully aqueous eluent. 相似文献
65.
Kimitada Terao 《Tetrahedron letters》2010,51(31):4107-11843
A highly efficient electrochemical method for synthesis of halosilanes bearing bulky substituents was developed. Electrophilic multiple substitution on tris(diphenylmethyl)silane with diarylcarbenium ions afforded a highly sterically demanding hydrosilane, tris(extended diarylmethyl)silane (TEDAMS-H), which was converted to the corresponding bromosilane (TEDAMS-Br). 相似文献
66.
Various cycloalkanes and straight‐chain alkanes were efficiently brominated with an aqueous HBr‐H2O2 system. This oxidative brominating process was promoted by catalysis and irradiation with light. The cycloalkanes were converted to the corresponding bromo‐cycloalkanes in moderate yields and the straight‐chain alkanes produced dominantly secondary bromides. This simple but effective bromination method of alkanes is characterized by high atom efficiency, inexpensive reagents and the absence of organic waste, which make it a good alternative to the existing method for C? H activation through bromination. 相似文献
67.
Alessandra Ricca Jean M. J. Tronchet Jacques Weber 《Journal of computer-aided molecular design》1992,6(6):541-552
Summary The cytotoxic activities of a series of sugar derivatives bearing electrophilic groups (1-cyanovinyl, 4-cyanochromen-2-yl and 3-nitrochromen-2-yl) have been correlated with their electrophilic properties. To this end, an electrophilic index was defined as an isovalue surface where the interaction energy with an incoming model nucelophile (H–) was equal to a predefined value. This index, calculated from extended Hückel wave functions, allows one to quantify the electrophilic character of the substrates and to describe its spatial localization within the molecular volume (at Michael acceptor sites or on other parts of the molecules). Only sugars for which Michael acceptor reactivity was predicted were retained, and they were subdivided into two groups: those showing antiviral activity against a retrovirus and those devoid of such activity. Under these conditions, good correlations between cytotoxic activity and electrophilic reactivity-positive for the first group, negative for the second-were found. In addition, the ratio electrophilicity/sum of the absolute value of the dipole plus its projection along the principal axis of inertia, Z, of the molecule allows one to predict to which of these groups a sugar derivative belongs. 相似文献
68.
Reaction of substituted benzene rings with N‐bromophthalimide, under neutral conditions, gave the corresponding bromo derivatives with a preference for the formation of the para bromo isomer over the ortho isomer. The simple work‐up procedure minimizes loss of product and the yields are good. 相似文献
69.
The behavior of (pyrrol-1-yl)furazans in electrophilic substitution reactions (halogenation, nitration, and acylation) was
studied. The presence of the furazan ring substantially did not affect the regioselectivity of the reactions but it prevented
replacement of all the hydrogen atoms in the pyrrole ring by electrophiles.
Dedicated to Academician V. A. Tartakovsky on the occasion of his 75th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1516–1520, August, 2007. 相似文献
70.
Peer Kirsch Matthias Bremer Herwig A Buchholz Enno Lork Gerd-Volker Röschenthaler 《Journal of fluorine chemistry》2003,122(2):233-236
The hitherto elusive title compound was synthesized and characterized with the aim to study its potential as a carbon-based (“CF-type”) electrophilic fluorination reagent. A detailed discussion of its structure, properties and reactivity is based on experimental studies as well as on molecular modeling. 相似文献