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Regioselective esterification of vicinal diols on monosaccharide derivatives via Mitsunobu reactions
We have carried out a series of esterification reactions of secondary alcohols derived from d-glucose, d-mannose, and d-galactose via the Mitsunobu reaction. The benzoylation reaction of vicinal diols derived from monosaccharides under Mitsunobu conditions afforded monobenzoates with retention of stereochemistry only. The regioselectivity of these reactions depends on the stereochemistry of the sugar starting material. The Mitsunobu reactions on these diols may be used for the selective protection of other vicinal secondary hydroxyl groups. 相似文献
54.
M.Sc. Vincente T. Sterrenberg M.Sc. Dörte Stalling M.Sc. J. Iven H. Knaack Dr. Timothy K. Soh Prof. Dr. Jens B. Bosse Prof. Dr. Chris Meier 《Angewandte Chemie (International ed. in English)》2023,62(38):e202308271
The metabolic labeling of nucleic acids in living cells is highly desirable to track the dynamics of nucleic acid metabolism in real-time and has the potential to provide novel insights into cellular biology as well as pathogen-host interactions. Catalyst-free inverse electron demand Diels–Alder reactions (iEDDA) with nucleosides carrying highly reactive moieties such as axial 2-trans-cyclooctene (2TCOa) would be an ideal tool to allow intracellular labeling of DNA. However, cellular kinase phosphorylation of the modified nucleosides is needed after cellular uptake as triphosphates are not membrane permeable. Unfortunately, the narrow substrate window of most endogenous kinases limits the use of highly reactive moieties. Here, we apply our TriPPPro (triphosphate pronucleotide) approach to directly deliver a highly reactive 2TCOa-modified 2′-deoxycytidine triphosphate reporter into living cells. We show that this nucleoside triphosphate is metabolically incorporated into de novo synthesized cellular and viral DNA and can be labeled with highly reactive and cell-permeable fluorescent dye-tetrazine conjugates via iEDDA to visualize DNA in living cells directly. Thus, we present the first comprehensive method for live-cell imaging of cellular and viral nucleic acids using a two-step labeling approach. 相似文献
55.
Dr. Stanislav L. Veinberg Zachary W. Friedl Austin W. Lindquist Brianna Kispal Dr. Kristopher J. Harris Dr. Luke A. O'Dell Prof. Robert W. Schurko 《Chemphyschem》2016,17(23):4011-4027
14N ultra‐wideline solid‐state NMR (SSNMR) spectra were obtained for 16 naturally occurring amino acids and four related derivatives by using the WURST–CPMG (wideband, uniform rate, and smooth truncation Carr–Purcell–Meiboom–Gill) pulse sequence and frequency‐stepped techniques. The 14N quadrupolar parameters were measured for the sp3 nitrogen moieties (quadrupolar coupling constant, CQ, values ranged from 0.8 to 1.5 MHz). With the aid of plane‐wave DFT calculations of the 14N electric‐field gradient tensor parameters and orientations, the moieties were grouped into three categories according to the values of the quadrupolar asymmetry parameter, ηQ: low (≤0.3), intermediate (0.31–0.7), and high (≥0.71). For RNH3+ moieties, greater variation in N?H bond lengths was observed for systems with intermediate ηQ values than for those with low ηQ values (this variation arose from different intermolecular hydrogen‐bonding arrangements). Strategies for increasing the efficiency of 14N SSNMR spectroscopy experiments were discussed, including the use of sample deuteration, high‐power 1H decoupling, processing strategies, high magnetic fields, and broadband cross‐polarization (BRAIN‐CP). The temperature‐dependent rotations of the NH3 groups and their influence on 14N transverse relaxation rates were examined. Finally, 14N SSNMR spectroscopy was used to differentiate two polymorphs of l ‐histidine through their quadrupolar parameters and transverse relaxation time constants. The strategies outlined herein permitted the rapid acquisition of directly detected 14N SSNMR spectra that to date was not matched by other proposed methods. 相似文献
56.
Zhang YM Chohnan S Virga KG Stevens RD Ilkayeva OR Wenner BR Bain JR Newgard CB Lee RE Rock CO Jackowski S 《Chemistry & biology》2007,14(3):291-302
Coenzyme A (CoA) is the major acyl group carrier in intermediary metabolism. Hopantenate (HoPan), a competitive inhibitor of the pantothenate kinases, was used to chemically antagonize CoA biosynthesis. HoPan dramatically reduced liver CoA and mice developed severe hypoglycemia. Insulin was reduced, glucagon and corticosterone were elevated, and fasting accelerated hypoglycemia. Metabolic profiling revealed a large increase in acylcarnitines, illustrating the role of carnitine in buffering acyl groups to maintain the nonesterified CoASH level. HoPan triggered significant changes in hepatic gene expression that substantially increased the thioesterases, which liberate CoASH from acyl-CoA, and increased pyruvate dehydrogenase kinase 1, which prevents the conversion of CoASH to acetyl-CoA. These results identify the metabolic rearrangements that maintain the CoASH pool which is critical to mitochondrial functions, including gluconeogenesis, fatty acid oxidation, and the tricarboxylic acid and urea cycles. 相似文献
57.
Kilian KA Böcking T Gaus K King-Lacroix J Gal M Gooding JJ 《Chemical communications (Cambridge, England)》2007,(19):1936-1938
Cholera toxin levels are optically detected by affinity capture within hybrid lipid bilayer membranes formed in the nanostructures of porous silicon photonic crystals. 相似文献
58.
Central transition (55)Mn NMR spectra of several solid manganese pentacarbonyls acquired at magnetic field strengths of 11.75, 17.63, and 21.1 T are presented. The variety of distinct powder sample lineshapes obtained demonstrates the sensitivity of solid-state (55)Mn NMR to the local bonding environment, including the presence of crystallographically unique Mn sites, and facilitates the extraction of the Mn chemical shift anisotropies, CSAs, and the nuclear quadrupolar parameters. The compounds investigated include molecules with approximate C(4v) symmetry, LMn(CO)(5)(L = Cl, Br, I, HgMn(CO)(5), CH(3)) and several molecules of lower symmetry (L = PhCH(2), Ph(3-n)Cl(n)Sn (n= 1, 2, 3)). For these compounds, the Mn CSA values range from <100 ppm for Cl(3)SnMn(CO)(5) to 1260 ppm for ClMn(CO)(5). At 21.1 T the (55)Mn NMR lineshapes are appreciably influenced by the Mn CSA despite the presence of significant (55)Mn quadrupolar coupling constants that range from 8.0 MHz for Cl(3)SnMn(CO)(5) to 35.0 MHz for CH(3)Mn(CO)(5). The breadth of the solid-state (55)Mn NMR spectra of the pentacarbonyl halides is dominated by the CSA at all three applied magnetic fields. DFT calculations of the Mn magnetic shielding tensors reproduce the experimental trends and the magnitude of the CSA is qualitatively rationalized using a molecular orbital, MO, interpretation based on Ramsey's theory of magnetic shielding. In addition to the energy differences between symmetry-appropriate occupied and virtual MOs, the d-character of the Mn MOs is important for determining the paramagnetic shielding contribution to the principal components of the magnetic shielding tensor. 相似文献
59.
Motivated by recent zone annealing measurements on stripe-forming block-copolymer films [B. C. Berry, Nano Lett. 7, 2789 (2007)], we study block-copolymer ordering with a spatiotemporally heterogeneous mobility. Specifically, we implement a time- and space-dependent mobility field in the relaxation of a diblock copolymer self-consistent field theory. The model includes a gradient in the local mobility and intrinsic nanoscale mobility variations characteristic of glass phenomenology. The simulations demonstrate that a spatiotemporally heterogeneous mobility can have a significant influence on microdomain ordering in block-copolymer systems, and that nanoscale dynamic heterogeneities associated with glass formation can impact the structure of the ordered block-copolymer microphase. 相似文献
60.
Kristopher O. Davis Kaiyun Jiang Carsten Demberger Heiko Zunft Helge Haverkamp Dirk Habermann Winston V. Schoenfeld 《固体物理学:研究快报》2013,7(5):319-321
Emitter formation for industrial crystalline silicon (c‐Si) solar cells is demonstrated by the deposition of phosphorous‐doped silicate glasses (PSG) on p‐type monocrystalline silicon wafers via in‐line atmospheric pressure chemical vapor deposition (APCVD) and subsequent thermal diffusion. Processed wafers with and without the PSG layers have been analysed by SIMS measurements to investigate the depth profiles of the resultant phosphorous emitters. Subsequently, complete solar cells were fabricated using the phosphorous emitters formed by doped silicate glasses to determine the impact of this high‐throughput doping method on cell performance. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献