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排序方式: 共有439条查询结果,搜索用时 31 毫秒
421.
Björn Hildebrandt Dr. Stephan Raub Prof. Dr. Walter Frank Prof. Dr. Christian Ganter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(21):6670-6678
A new synthetic route to complexes of the cationic N‐heterocyclic carbene ligand 2 has been developed by the attachment of a cationic pentamethylcyclopentadienylruthenium ([RuCp*]+) fragment to a metal‐coordinated benzimidazol‐2‐ylidene ligand. The coordination chemistry and the steric and electronic properties of the cationic carbene were investigated in detail by experimental and theoretical methods. X‐ray structures of three carbene–metal complexes were determined. The cationic ligand 2 is a poorer overall electron donor relative to the related neutral carbene, which is evident from cyclic voltammetry (CV) and IR measurements. 相似文献
422.
Ute Linz Henry Hildebrandt Hartmut Herrmann Thomas Engel 《Nachrichten aus der Chemie》2011,59(6):658-660
423.
424.
Fischer N Goddard-Borger ED Greiner R Klapötke TM Skelton BW Stierstorfer J 《The Journal of organic chemistry》2012,77(4):1760-1764
Imidazole-1-sulfonyl azide hydrochloride, an inexpensive and effective diazotransfer reagent, was recently found to be impact sensitive. To identify safer-to-handle forms of this reagent, several different salts of imidazole-1-sulfonyl azide were prepared, and their sensitivity to heat, impact, friction, and electrostatic discharge was quantitatively determined. A number of these salts exhibited improved properties and can be considered safer than the aforementioned hydrochloride. The solid-state structures of the chloride and less sensitive hydrogen sulfate were determined by single-crystal X-ray diffraction in an effort to provide some insight into the different properties of the materials. 相似文献
425.
Marta Bobrowska Janusz Typek Grzegorz Zolnierkiewicz Kamil Wardal Niko Guskos Iwona Pelech Marcin Podsiadly Urszula Narkiewicz 《Central European Journal of Chemistry》2012,10(6):1963-1968
Magnetic resonance study of six samples consisting of carbon encapsulated nickel nanoparticles or carbon nanotubes ended with such nickel nanoparticles was carried out at room temperature. Samples of Ni/C were prepared by carburization of nanocrystalline nickel by ethylene (C2H4) and methane (CH4). Hydrocarbons decomposition on nickel nanoparticles was done at temperatures 500, 600 and 700°C. Magnetic resonance spectra of samples designated as CH4/500, CH4/600, CH4/700, C2H4/500, C2H4/600 and C2H4/700 were obtained by Bruker E 500 spectrometer. The integrated intensities of the resonance spectra were correlated with the carburization conditions (temperature, type of hydrocarbon) during samples preparation. A core-shell model of the investigated samples allowed rough estimation of appropriate shell sizes. 相似文献
426.
Niko S. Radulovi? Goran A. Bogdanovi? Polina D. Blagojevi? Vidosav S. Deki? Rastko D. Vuki?evi? 《Journal of chemical crystallography》2011,41(4):545-551
Abstract
X-Ray analyses of 4-(naphthalen-1-ylamino)-3-nitro-chromen-2-one and 3-nitro-4-phenylamino-chromen-2-one showed that the mentioned compounds crystallize in the space groups P1- (triclinic crystal system; unit cell parameters: a = 8.087(2) ?, b = 9.241(3) ?, c = 10.911(3) ?, α = 93.77(3)°, β = 102.51(3)°, γ = 106.44(2)°, V = 756.4(4) ?3 and Z = 2) and P212121 (orthorhombic crystal system; unit cell parameters: a = 4.9274(9) ?, b = 14.725(3) ?, c = 17.866(4) ?, α = β = γ = 90°, V = 1296.3(5) ?3 and Z = 4), respectively. The analyses of crystal structures and gas phase conformations, inferred from single X-ray crystallographic and molecular modeling experiments, respectively, showed that the changes in π delocalization of the farmacoactive formal 3-amino-2-nitro-acrylic acid derivatives might explain the observed significant difference of the antimicrobial and antioxidant activities and spectral properties of two 4-arylamino-3-nitro-coumarin derivatives. 相似文献427.
Toll H Berger P Hofmann A Hildebrandt A Oberacher H Lenhof HP Huber CG 《Electrophoresis》2006,27(13):2734-2746
Due to their extensive structural heterogeneity, the elucidation of glycosylation patterns in glycoproteins such as the subunits of human chorionic gonadotropin (hCG), hCG-alpha, and hCG-beta, remains one of the most challenging problems in the proteomic analysis of post-translational modifications. In consequence, glycosylation is usually studied after decomposition of the intact proteins to the proteolytic peptide level. However, by this approach all information about the combination of the different glycopeptides in the intact protein is lost. In this study we have, therefore, attempted to combine the results of glycan identification after tryptic digestion with molecular mass measurements on the native starting material of the new first WHO Reference Reagents (RR) for hCG-alpha (99/720) and hCG-beta (99/650). Despite the extremely high number of possible combinations of the glycans identified in the tryptic peptides by HPLC-MS (>1000 for hCG-alpha and >10 000 for hCG-beta), the mass spectra of intact hCG-alpha and hCG-beta revealed only a limited number of glycoforms present in hCG preparations from pools of pregnancy urines. Peak annotations for hCG-alpha were performed with the help of a bioinformatic algorithm that generated a database containing all possible modifications of the proteins, including modifications possibly introduced during sample preparation such as oxidation or truncation, for subsequent searches for combinations fitting the mass difference between the polypeptide backbone and the measured molecular masses. Fourteen different glycoforms of hCG-alpha, containing biantennary, partly sialylized hybrid-type glycans, including methionine-oxidized and N-terminally truncated forms, were identified. Mass spectra of high quality were also obtained for hCG-beta, however, a database search mass accuracy of +/-5 Da was insufficient to unambiguously assign the possible combinations of post-translational modifications. In summary, mass spectrometric fingerprints of intact molecules were shown to be highly useful for the characterization of glycosylation patterns of different hCG preparations such as the new first WHO RR for immunoassays and could be the first step in establishing biophysical reference methods for hCG and related molecules. 相似文献
428.
Sampling of water, soil and sediment to trace organic pollutants at a river-basin scale 总被引:1,自引:0,他引:1
Sampling is considered a crucial step in the analysis of organic compounds in the environment. This review describes field
sampling techniques and provides detailed step-by-step procedures for collection and preservation of all major environmental
matrices (water, sediment and soil) integrated as part of the river-basin water cycle. Attention is given to the prerequisites
for obtaining reliable samples, and the practical issues of sample collection (planning, field sampling, sampling strategies
and equipment and data quality assessment) are considered. Considering the heterogeneity of environmental matrices, special
considerations for each matrix are given to solve typical problems and to find the most appropriate solutions to ensure the
quality of the sample. The procedures described in the next sections are commonly used protocols that reflect true field conditions
and current state-of-the-art techniques used in the sampling of organic compounds. The aim is to signify the importance of
sampling to the overall analytical procedure. Finally, quality control issues to be considered in environmental sampling are
given. 相似文献
429.
Kadzimirsz D Hildebrandt D Merz K Dyker G 《Chemical communications (Cambridge, England)》2006,(6):661-662
The title compounds are enantioselectively synthesized in just two preparative steps, making use of the Ugi-four-component reaction with an amino acid as chiral component, followed by a gold-catalyzed hydroamination. 相似文献
430.