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101.
Xie Y Hill JP Schumacher AL Karr PA D'Souza F Anson CE Powell AK Ariga K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(35):9824-9833
A novel corrole-type macrocycle, oxocorrologen (2), substituted with hemiquinone groups, has been synthesized. It was found to undergo multiple tautomerism of its exchangeable protons between electronegative atom sites at the macrocyclic core (nitrogen atoms) and periphery (phenol oxygen atoms). Alkylation at one macrocyclic nitrogen atom with a 4-nitrobenzyl group gave 3, which can exist in only two tautomeric forms depending on the solvent. Tautomerism has been studied by means of (1)H NMR spectroscopy in a variety of solvents and solvent mixtures. Tautomer structure assignments have been supported by DFT calculations of the relative energies of the tautomers. X-ray crystallography of the N-nitrobenzyl derivative has revealed that intramolecular hydrogen bonding may be responsible for stabilizing the observed tautomers. The solvent dependence of the tautomerism of 2 and 3 confers solvatochromism. Electrochemical measurements on 2 and 3 in their respective quinone forms have revealed irreversible processes, but indicate that they are both electron-deficient with a small HOMO-LUMO gap and first reduction potentials close to those of fullerene electron acceptors. 相似文献
102.
Yang L Nakamura N Hattori M Wang Z Bligh SW Xu L 《Rapid communications in mass spectrometry : RCM》2007,21(12):1833-1840
Sensitive, selective and reliable high-performance liquid chromatography (HPLC)-diode array detection (DAD)/electrospray ionization multi-stage mass spectrometry (ESI-MSn) methods have been developed for the characterization of nine 2-glucosyloxycinnamic acid derivatives and quantitative analysis of three of the major 2-glucosyloxycinnamic acids, cis-melilotoside, trans-melilotoside and dihydromelilotoside, present in Dendrobium medicinal plants. The identities of the latter three major 2-glucosyloxycinnamic acids were confirmed by comparing their retention times, UV and mass spectra with those of the reference standards. The characteristic ESI-MSn fragmentation patterns of the remaining six 2-glucosyloxycinnamic acid derivatives, which are similar to the three major compounds, have allowed the putative elucidation of their structures. The concentrations of the cis-, trans- and dihydromelilotosides were simultaneously determined by HPLC/ESI-MS2 using the multiple reaction monitoring (MRM) mode in extracts of Dendrobium species. The method was validated with respect to the overall intra- and inter-day variation (RSD less than 8%) and the limits of quantification for the cis-, trans- and dihydromelilotosides were 0.09, 0.09 and 0.01 microg/mL, respectively. 相似文献
103.
Alpha-glucosidase inhibitors from Millettia conraui 总被引:1,自引:0,他引:1
Tiabou Tchinda A Nahar Khan S Fuendjiep V Ngandeu F Ngono Ngane A Choudhary MI 《Chemical & pharmaceutical bulletin》2007,55(9):1402-1403
A new geranylated isoflavone, 7-O-geranyl-6-methoxypseudobaptigenin (1) was isolated from the stem barks of Millettia conraui, along with known compounds 5-methoxydurmillone (2), conrauinone A (3), beta-amyrine (4), sitosterol (5), 3-O-beta-D-glucopyranosyl sitosterol (6) and n-docosanol (7). Compounds 1 and 4 showed a significant alpha-glucosidase inhibitory activity. The structures of the compounds were determined by analysis of their spectroscopic data. 相似文献
104.
Amor Ben Ali Minh Trang Dang Annie Hémon-Ribaud Vincent Maisonneuve 《Journal of solid state chemistry》2007,180(6):1911-1917
Single crystals of [H3dien]·(FeF6)·H2O (I) and [H3dien]·(CrF6)·H2O (II) are obtained by solvothermal synthesis under microwave heating. I is orthorhombic (Pna21) with a=11.530(2) Å, b=6.6446(8) Å, c=13.787(3) Å, V=1056.3(2) Å3 and Z=4. II is monoclinic (P21/c) with a=13.706(1) Å, b=6.7606(6) Å, c=11.3181(9) Å, β=99.38(1)°, V=1034.7(1) Å3 and Z=4. The structure determinations, performed from single crystal X-ray diffraction data, lead to the R1/wR2 reliability factors 0.028/0.066 for I and 0.035/0.102 for II. The structures of I and II are built up from isolated FeF6 or CrF6 octahedra, water molecules and triprotonated amines. In both structures, each octahedron is connected by hydrogen bonds to six organic cations and two water molecules. The iron-based compound is also characterized by 57Fe Mössbauer spectrometry: the hyperfine structure confirms the presence of Fe3+ in octahedral coordination and reveals the existence of paramagnetic spin fluctuations. 相似文献
105.
106.
Recent results on the selective reduction of cyclic vinylphosphine oxides and vinylphosphinates, as well as their refunctionalization by the use of borane, are summarized. The selective reduction of the phosphorus moiety of unsaturated phosphonates, phosphinates, and phosphine oxides is also discussed. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:161–167, 2001 相似文献
107.
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109.
Stereoselective Synthesis of the Halaven C14–C26 Fragment from D‐Quinic Acid: Crystallization‐Induced Diastereoselective Transformation of an α‐Methyl Nitrile 下载免费PDF全文
Francis Belanger Dr. Charles E. Chase Dr. Atsushi Endo Dr. Francis G. Fang Dr. Jing Li Steven R. Mathieu Dr. Annie Z. Wilcoxen Huiming Zhang 《Angewandte Chemie (International ed. in English)》2015,54(17):5108-5111
Crystallization‐induced diastereoselective transformation (CIDT) of an α‐methyl nitrile completes an entirely non‐chromatographic synthesis of the halichondrin B C14–C26 stereochemical array. The requisite α‐methyl nitrile substrate is derived from D ‐quinic acid through a series of substrate‐controlled stereoselective reactions via a number of crystalline intermediates that benefit from a rigid polycyclic template. Therefore, all four stereogenic centers in the Halaven C14–C26 fragment were derived from the single chiral source D ‐quinic acid. 相似文献
110.
Annie Praud-Tabaries 《Tetrahedron letters》2009,50(14):1645-6755
A terpenoid-like library containing 1,4-disubstituted-(1H)-1,2,3-triazoles was prepared by means of 1,3-dipolar cycloaddition of geranyl and farnesyl azides with a set of terminal alkynes, in order to design a new class of potentially active anti-biofilm compounds. Reactions were optimized to proceed under mild conditions and in high yields. Two compounds were found to possess interesting activity against Pseudoalteromonas sp. biofilm. This process is suitable for combinatorial chemistry of marine natural product-like compounds. 相似文献