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881.
Diastereoselective Synthesis of Open‐Chain Secondary Alkyllithium Compounds and Trapping Reactions with Electrophiles
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Dr. Guillaume Dagousset Kohei Moriya Rasmus Mose Dr. Guillaume Berionni Prof. Dr. Konstantin Karaghiosoff Prof. Dr. Paul Knochel 《Angewandte Chemie (International ed. in English)》2014,53(5):1425-1429
A practical stereoselective iodide–lithium exchange was used in the first general preparation of functionalized stereodefined acyclic secondary nonstabilized lithium reagents from the corresponding secondary alkyl iodides. These lithium reagents react with various electrophiles including carbon electrophiles with high retention of configuration. Kinetic data on the configurational stability of these acyclic alkyllithium reagents are given. This methodology offers a new entry to chiral synthons for the stereoselective synthesis of open‐chain molecules. 相似文献
882.
From Syndiotactic Homopolymers to Chemically Tunable Alternating Copolymers: Highly Active Yttrium Complexes for Stereoselective Ring‐Opening Polymerization of β‐Malolactonates
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Cédric G. Jaffredo Dr. Yulia Chapurina Dr. Sophie M. Guillaume Prof. Dr. Jean‐François Carpentier 《Angewandte Chemie (International ed. in English)》2014,53(10):2687-2691
Alternating copolymers constitute an attractive class of materials. It was shown previously that highly alternated poly(β‐hydroxyalkanoate)s (PHAs) can be prepared by ring‐opening polymerization (ROP) of mixtures of two different enantiomerically pure 4‐alkyl‐β‐propiolactones. However, the approach could not be extended to PHAs with chemically tunable functional groups, which is highly desirable to access original advanced materials. Reported herein is the first highly syndioselective and controlled ROP of racemic allyl and benzyl β‐malolactonates (MLAR; R=allyl, benzyl) using an yttrium complex supported by a tetradentate dichloro‐substituted bis(phenolate) ligand. This highly active catalyst allows the nearly perfect alternating copolymerization of MLAAllyl and MLABenzyl. Hydrogenolysis of the benzyloxycarbonyl or functionalization of the allyl pendant groups opens a route towards a new class of functional alternating copolymers. 相似文献
883.
Spontaneous Biomimetic Formation of (±)‐Dictazole B under Irradiation with Artificial Sunlight
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Adam Skiredj Dr. Mehdi A. Beniddir Prof. Dr. Delphine Joseph Karine Leblanc Dr. Guillaume Bernadat Dr. Laurent Evanno Prof. Dr. Erwan Poupon 《Angewandte Chemie (International ed. in English)》2014,53(25):6419-6424
Guided by biosynthetic considerations, the total synthesis of dictazole B is reported for the first time. Experimental evidence for an easy access to challenging cyclobutane alkaloids of marine origin, which are often postulated to be biosynthetic precursors of more complex structures, is provided. 相似文献
884.
Dr. Martin Rahm Guillaume Bélanger‐Chabot Prof. Ralf Haiges Prof. Karl O. Christe 《Angewandte Chemie (International ed. in English)》2014,53(27):6893-6897
The elusive nitryl cyanide, NCNO2, has been synthesized and characterized. It was prepared in good yield, isolated by fractional condensation, characterized by NMR and vibrational spectroscopy, and studied by theoretical calculations. Nitryl cyanide holds promise as a high energy density material (HEDM) and might also prove useful as a HEDM building block. The simplicity and inherent stability of nitryl cyanide, together with the known multitude of nitriles in interstellar space, suggest that the compound might also be a potential candidate for observations in atmospheric and interstellar chemistry. 相似文献
885.
From Chitin to Bioactive Chitooligosaccharides and Conjugates: Access to Lipochitooligosaccharides and the TMG‐chitotriomycin
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Guillaume Despras Aurélien Alix Dominique Urban Boris Vauzeilles Jean‐Marie Beau 《Angewandte Chemie (International ed. in English)》2014,53(44):11912-11916
The direct and chemoselective N‐transacylation of peracetylated chitooligosaccharides (COSs), readily obtained from chitin, to give per‐N‐trifluoroacetyl derivatives offers an attractive route to size‐defined COSs and derived glycoconjugates. It involves the use of various acceptor building blocks and trifluoromethyl oxazoline dimer donors prepared with efficiency and highly reactive in 1,2‐trans glycosylation reactions. This method was applied to the preparation of the important symbiotic glycolipids which are highly active on plants and to the TMG‐chitotriomycin, a potent and specific inhibitor of insect, fungal, and bacterial N‐acetylglucosaminidases. 相似文献
886.
Sandra Malaquin Mouhamad Jida Justin Courtin Guillaume Laconde Nicolas Willand Benoit Deprez Rebecca Deprez-Poulain 《Tetrahedron letters》2013,54(6):562-567
We report efficient miniaturized conditions to prepare arrays of bicyclic lactams for screening. The nature of the solvent is usually an important factor of reactivity. At a small synthesis scale, when automated pipetting devices are required, physical properties of the solvent, such as surface tension and vapor pressure also become very important. After having shown that a complete evaporation of a solution of reagents in water or a mixture of ethanol and water yields the expected lactams, we exemplified the reaction and procedure with the preparation of a library of 80 members. Our synthesis scheme is validated for synthesis scales from 1 to 100 mg. Therefore, it can be used both to produce rapidly test samples for HTS as well as to prepare intermediates for the synthesis of more elaborated nature-inspired compounds. 相似文献
887.
Guillaume Robichaud Jeremy A. Barry Kenneth P. Garrard David C. Muddiman 《Journal of the American Society for Mass Spectrometry》2013,24(1):92-100
Mass spectrometry imaging (MSI) allows for the direct monitoring of the abundance and spatial distribution of chemical compounds over the surface of a tissue sample. This technology has opened the field of mass spectrometry to numerous innovative applications over the past 15 years. First used with SIMS and MALDI MS that operate under vacuum, interest has grown for mass spectrometry ionization sources that allow for effective imaging but where the analysis can be performed at ambient pressure with minimal or no sample preparation. We introduce here a versatile source for MALDESI imaging analysis coupled to a hybrid LTQ-FT-ICR mass spectrometer. The imaging source offers single shot or multi-shot capability per pixel with full control over the laser repetition rate and mass spectrometer scanning cycle. Scanning rates can be as fast as 1 pixel/second and a spatial resolution of 45 μm was achieved with oversampling.
Design and integration of a versatile IR-MALDESI imaging source offering multi-shot capability with a commercial FT-ICR mass spectrometer 相似文献
888.
Anton Buzlukov Guillaume Gerbaud Carole Bourbon Sabine Hediger Gaël De Paëpe Sébastien Patoux Michel Bardet 《Journal of Solid State Electrochemistry》2013,17(5):1421-1427
Different synthesis batches of LiFePO4/C materials were prepared, and their electrochemical properties as positive cathodes for lithium-ion batteries were evaluated. Using standard solid-state NMR conditions, such as a 7-mm magic-angle-spinning probe performing at low spinning rates, information on both intercalated and non-intercalated (stored on the grain boundaries) lithium was obtained. A sharp signal assigned to non-intercalated lithium could be observed by diluting the active material in silica. Correlations could be, thus, obtained between the amount of each type of lithium and the electrochemical history and state of the material, revealing that the relative amount of surface lithium in a pristine LiFePO4/C material is rather constant and cannot be used as a criterion for its further specification. However, a drastic increase of this surface lithium was observed in the cathode materials of out-of-order batteries. As the cathode material recovered from the batteries after electrochemical testing was carefully washed before analysis, we can conclude that the non-intercalated lithium is strongly bound to the active material probably inside the so-called solid electrolyte interface layer at the surfaces of LiFePO4 particles. This work illustrates that solid-state lithium NMR can allow rapid characterization and testing of LiFePO4/C cathode materials. 相似文献
889.
Aurlien Chardon Arnaud Osi Damien Mahaut Thu‐Hong Doan Nikolay Tumanov Johan Wouters Luca Fusaro Benoît Champagne Guillaume Berionni 《Angewandte Chemie (International ed. in English)》2020,59(30):12402-12406
A highly bent triarylborane, 9‐boratriptycene, was generated in solution by selective protodeboronation of the corresponding tetra‐aryl boron ate complex with the strong Brønsted acid HNTf2. The iptycene core confers enhanced Lewis acidity to 9‐boratriptycene, making it unique in terms of structure and reactivity. We studied the stereoelectronic properties of 9‐boratriptycene by quantifying its association with small N‐ and O‐centered Lewis bases, as well as with sterically hindered phosphines. The resultant Lewis adducts exhibited unique structural, spectroscopic, and photophysical properties. Beyond the high pyramidalization of the 9‐boratriptycene scaffold and its low reorganization energy upon Lewis base coordination, quantum chemical calculations revealed that the absence of π donation from the triptycene aryl rings to the boron vacant pz orbital is one of the main reasons for its high Lewis acidity. 相似文献