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541.
Yuya Inaba Jian Yang Yu Kakibayashi Dr. Tomoki Yoneda Dr. Yuki Ide Dr. Yuh Hijikata Dr. Jenny Pirillo Dr. Ranajit Saha Prof. Dr. Jonathan L. Sessler Prof. Dr. Yasuhide Inokuma 《Angewandte Chemie (International ed. in English)》2023,62(15):e202301460
Chiral pyrrolic macrocycles continue to attract interest. However, their molecular design remains challenging. Here, we report a calixpyrrole-based chiral macrocyclic system, calix[1]furan[1]pyrrole[1]thiophene ( 1 ), synthesized from an oligoketone. Macrocycle 1 adopts a partial cone conformation in the solid state, and undergoes racemization via ring inversion. Molecular dynamics simulations revealed that inversion of the thiophene is the rate determining step. Pyrrole N-methylation suppressed racemization and permitted chiral resolution. Enantioselective N-methylation also occurred in the presence of a chiral ammonium salt, although the stereoselectivity is modest. A unique feature of 1 is that it acts as a useful synthetic precursor to yield several calix[n]furan[n]pyrrole[n]thiophene products (n=2–4), including a calix[12]pyrrole analogue that to our knowledge constitutes the largest calix[n]pyrrole-like species to be structurally characterized. 相似文献
542.
Ridlova G Mortimer JC Maslen SL Dupree P Stephens E 《Rapid communications in mass spectrometry : RCM》2008,22(17):2723-2730
The growing interest in the conversion of plant biomass into biofuels has recently highlighted the lack of analytical techniques that are able to profile the fine structures of plant cell-wall polysaccharides. Here we present a new liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI-MS) platform called Oligosaccharide Quantitation using Isotope Tagging (OliQuIT) developed for profiling the oligosaccharides derived from glycosyl hydrolase digestion of polysaccharides. The method is demonstrated using different arabinoxylan-derived oligosaccharide samples, which are reductively aminated with either the light (12C6) or heavy (13C6) form of aniline. The complex oligosaccharide mixtures are analysed by capillary normal-phase (NP)-LC and ESI-MS. Importantly, arabinoxylan oligosaccharide isomers are separated by NP-LC and their relative abundance in different samples can be determined from the intensities of ions labeled with the different isotopes. OliQuIT will be of use in multiple applications, including screening for plant varieties with improved saccharification properties, characterizing glycosyl hydrolase specificities and analysing plant glycosyl transferase mutants. 相似文献
543.
Yang JJ Yang J Wei L Zurkiya O Yang W Li S Zou J Zhou Y Maniccia AL Mao H Zhao F Malchow R Zhao S Johnson J Hu X Krogstad E Liu ZR 《Journal of the American Chemical Society》2008,130(29):9260-9267
We describe the rational design of a novel class of magnetic resonance imaging (MRI) contrast agents with engineered proteins (CAi.CD2, i = 1, 2,..., 9) chelated with gadolinium. The design of protein-based contrast agents involves creating high-coordination Gd(3+) binding sites in a stable host protein using amino acid residues and water molecules as metal coordinating ligands. Designed proteins show strong selectivity for Gd(3+) over physiological metal ions such as Ca(2+), Zn(2+), and Mg(2+). These agents exhibit a 20-fold increase in longitudinal and transverse relaxation rate values over the conventional small-molecule contrast agents, e.g., Gd-DTPA (diethylene triamine pentaacetic acid), used clinically. Furthermore, they exhibit much stronger contrast enhancement and much longer blood retention time than Gd-DTPA in mice. With good biocompatibility and potential functionalities, these protein contrast agents may be used as molecular imaging probes to target disease markers, thereby extending applications of MRI. 相似文献
544.
Waern JB Desmarets C Chamoreau LM Amouri H Barbieri A Sabatini C Ventura B Barigelletti F 《Inorganic chemistry》2008,47(8):3340-3348
Luminescent cyclometalated rhodium(III) and iridium(III) complexes of the general formula [M(ppy) 2(N (wedge)N)][PF 6], with N (wedge)N = Hcmbpy = 4-carboxy-4'-methyl-2,2'-bipyridine and M = Rh ( 1), Ir ( 2) and N (wedge)N = H 2dcbpy = 4,4'-dicarboxy-2,2'-bipyridine and M = Rh ( 3), Ir ( 4), were prepared in high yields and fully characterized. The X-ray molecular structure of the monocarboxylic iridium complex [Ir(ppy) 2(Hcmbpy)][PF 6] ( 2) was also determined. The photophysical properties of these compounds were studied and showed that the photoluminescence of rhodium complexes 1 and 3 and iridium complexes 2 and 4 originates from intraligand charge-transfer (ILCT) and metal-to-ligand charge-transfer/ligand-centered MLCT/LC excited states, respectively. For comparison purposes, the mono- and dicarboxylic acid ruthenium complexes [Ru(DIP) 2(Hcmbpy)][Cl] 2 ( 5) and [Ru(DIP) 2(H 2dcbpy)][Cl] 2 ( 6), where DIP = 4,7-diphenyl-1,10-phenanthroline, were also prepared, whose emission is MLCT in nature. Comparison of the photophysical behavior of these rhodium(III), iridium(III), and ruthenium(II) complexes reveals the influence of the carboxylic groups that affect in different ways the ILCT, MLCT, and LC states. 相似文献
545.
Kang C Troyer JL Robertson EM Rothgeb DW Hossain E Wyrwas RB Parmenter CS Jarrold CC 《The Journal of chemical physics》2008,128(10):104309
Anion photoelectron spectra of the O(2)(-) . arene and O(4)(-) . arene complexes with p-xylene and p-difluorobenzene are presented and analyzed with the aid of calculations on the anions and corresponding neutrals. Relative to the adiabatic electron affinity of O(2), the O(2)(-) . arene spectra are blueshifted by 0.75-1 eV. Solvation energy alone does not account for this shift, and it is proposed that a repulsive portion of the neutral potential energy surface is accessed in the detachment, resulting in dissociative photodetachment. O(2)(-) is found to interact more strongly with the p-difluorobenzene than the p-xylene. The binding motif involves the O(2)(-) in plane with the arene, interacting via electron donation along nearby C-H bonds. A peak found at 4.36(2) eV in the photoelectron spectrum of O(2)(-) . p-difluorobenzene (p-DFB) is tentatively attributed to the charge transfer state, O(2)(-) . p-DFB(+). Spectra of O(4)(-) . arene complexes show less blueshift in electron binding energy relative to the spectrum of bare O(4)(-), which itself undergoes dissociative photodetachment. The striking similarity between the profiles of the O(4)(-) . arene complexes with the O(4)(-) spectrum suggests that the O(4)(-) molecule remains intact upon complex formation, and delocalization of the charge across the O(4)(-) molecule results in similar structures for the anion and neutral complexes. 相似文献
546.
de Korompay A Hill JC Carter JF NicDaeid N Sleeman R 《Journal of chromatography. A》2008,1178(1-2):1-8
A method was developed for the isolation of 3,4-methylenedioxymethylamphetamine (MDMA) and other active ingredients from illicit ecstasy tablets. The method employed supported liquid extraction (SLE) with cartridges containing a modified form of diatomaceous earth. The method developed was simple and robust and the extract could be analysed directly, by GC-MS, to identify ingredients and reduced in volume for isotope ratio MS analysis of both delta(13)C and delta(15)N. The technique was shown to be highly reproducible, independent of the tablet matrix and considerably faster than existing liquid-liquid extraction methods. Crucially, no significant isotopic fractionation was observed as a result of the extraction process. 相似文献
547.
Gordon RJ Campbell J Henderson DK Henry DC Swart RM Tasker PA White FJ Wood JL Yellowlees LJ 《Chemical communications (Cambridge, England)》2008,(39):4801-4803
Novel polynucleating, di- and tri-acidic ligands have been designed to increase the molar and mass transport efficiencies for the recovery of base metals by solvent extraction. 相似文献
548.
549.
550.
Dana M. Mizrahi Melany Omer‐Mizrahi Jenny Goldshtein Nataly Askinadze Shlomo Margel 《Journal of polymer science. Part A, Polymer chemistry》2010,48(23):5468-5478
Poly(ethylene glycol) (PEG) mono methacrylate ester (MAPEG) has been used, through a variety of reactions, to form several novel monomers, bearing both a polymerizable handle and various functional groups. These new compounds may be conjugated to biomolecules via amine, acid, or thiol moieties or they may form dendrimers via the epoxide. In addition, polymerization of these monomers may result in functionalized nanoparticles and microparticles or coatings, thus altering the acid‐base or electrochemical properties of surfaces and particles. Full synthetic considerations, including interesting intermediates, are reported. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献