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571.
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573.
Monika Taucher Kathrin Breuker 《Journal of the American Society for Mass Spectrometry》2010,21(6):918-929
We have studied the effect of solution additives on hydrolysis and charge state distribution in ESI MS of RNA. Lower and higher
charge state ions can be electrosprayed from solutions containing 25 mM piperidine/25 mM imidazole and 1% vol. triethylamine,
respectively, with base-catalyzed hydrolysis rates that are sufficiently slow to perform MS/MS experiments. These lower and
higher charge state ions are suitable as precursors for CAD and EDD, respectively. We demonstrate nearly complete sequence
coverage for 61 nt RNA dissociated by CAD, and 34 nt RNA dissociated by EDD, and suggest a mechanism for backbone fragmentation
in EDD of RNA. 相似文献
574.
Virdee S Kapadnis PB Elliott T Lang K Madrzak J Nguyen DP Riechmann L Chin JW 《Journal of the American Chemical Society》2011,133(28):10708-10711
Protein ubiquitination is a post-translational modification that regulates almost all aspects of eukaryotic biology. Here we discover the first routes for the efficient site-specific incorporation of δ-thiol-L-lysine (7) and δ-hydroxy-L-lysine (8) into recombinant proteins, via evolution of a pyrrolysyl-tRNA synthetase/tRNA(CUA) pair. We combine the genetically directed incorporation of 7 with native chemical ligation and desulfurization to yield an entirely native isopeptide bond between substrate proteins and ubiquitin. We exemplify this approach by demonstrating the synthesis of a ubiquitin dimer and the first synthesis of ubiquitinated SUMO. 相似文献
575.
Engelhardt K Rumpel A Walter J Dombrowski J Kulozik U Braunschweig B Peukert W 《Langmuir : the ACS journal of surfaces and colloids》2012,28(20):7780-7787
The surface chemistry of ions, water molecules, and proteins as well as their ability to form stable networks in foams can influence and control macroscopic properties such as taste and texture of dairy products considerably. Despite the significant relevance of protein adsorption at liquid interfaces, a molecular level understanding on the arrangement of proteins at interfaces and their interactions has been elusive. Therefore, we have addressed the adsorption of the model protein bovine serum albumin (BSA) at the air-water interface with vibrational sum-frequency generation (SFG) and ellipsometry. SFG provides specific information on the composition and average orientation of molecules at interfaces, while complementary information on the thickness of the adsorbed layer can be obtained with ellipsometry. Adsorption of charged BSA proteins at the water surface leads to an electrified interface, pH dependent charging, and electric field-induced polar ordering of interfacial H(2)O and BSA. Varying the bulk pH of protein solutions changes the intensities of the protein related vibrational bands substantially, while dramatic changes in vibrational bands of interfacial H(2)O are simultaneously observed. These observations have allowed us to determine the isoelectric point of BSA directly at the electrolyte-air interface for the first time. BSA covered air-water interfaces with a pH near the isoelectric point form an amorphous network of possibly agglomerated BSA proteins. Finally, we provide a direct correlation of the molecular structure of BSA interfaces with foam stability and new information on the link between microscopic properties of BSA at water surfaces and macroscopic properties such as the stability of protein foams. 相似文献
576.
Dr. Kathrin Junge Bianca Wendt Felix Alexander Westerhaus Dr. Anke Spannenberg Dr. Haijun Jiao Prof. Dr. Matthias Beller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(29):9011-9018
The synthesis of phosphine–imidazolyl ligands 1 and 2 in good yields is presented. In combination with [{Ru(benzene)Cl2}2], ligands 1 c and 1 e formed efficient catalyst systems for the selective hydrogenation of various carboxylic esters into their corresponding primary alcohols. Furthermore, the structures of four ruthenium complexes with ligands 1 b , 1 c , 1 d , and 1 e were determined by X‐ray crystallography, which showed the formation of different coordination modes depending on the ligand structure. 相似文献
577.
Wienhöfer G Westerhaus FA Jagadeesh RV Junge K Junge H Beller M 《Chemical communications (Cambridge, England)》2012,48(40):4827-4829
A novel iron-catalyzed transfer hydrogenation of alkynes to the corresponding alkenes applying formic acid as a hydrogen donor is reported. An in situ combination of Fe(BF(4))(2)·6H(2)O and tetraphos allows for highly selective hydrogenation of a broad range of aromatic and aliphatic alkynes tolerating different functional groups. 相似文献
578.
A rapid and sensitive method for the screening and quantification of 35 benzodiazepines in human urine by gas chromatography/time-of-flight mass spectrometry was developed and validated. Target analytes were isolated from 1 ml urine by solid-phase extraction using Oasis MCX extraction columns (extraction recovery between 35 and 99%). With a supported liquid-liquid extraction method, a new modification of conventional liquid-liquid-extraction, a less time intensive alternative for benzodiazepine extraction is presented. The sample pretreatment entails the derivatization of the benzodiazepines with N,O-bis(trimethylsilyl)trifluoroacetamide plus 1% trimethylchlorosilane. Separation of all benzodiazepines was done within 9.5 min, and detection was based on full mass spectra for each analyte. A deconvolution algorithm was used for unresolved chromatographic peaks to identify coeluted substances. The subsequent quantification was done using significant masses. The limit of quantification is 10 ng/ml for most of the compounds. Linearity is in the range between 10 and 350 ng/ml. Reproducibility was observed with coefficients of variation below 2% at concentrations of 50 and 200 ng/ml. The accuracy is between 88 and 108% depending on the respective analyte and the concentration. 相似文献
579.
Junge K Wendt B Westerhaus FA Spannenberg A Jiao H Beller M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(29):9011-9018
The synthesis of phosphine-imidazolyl ligands 1 and 2 in good yields is presented. In combination with [{Ru(benzene)Cl(2)}(2)], ligands 1?c and 1?e formed efficient catalyst systems for the selective hydrogenation of various carboxylic esters into their corresponding primary alcohols. Furthermore, the structures of four ruthenium complexes with ligands 1?b, 1?c, 1?d, and 1?e were determined by X-ray crystallography, which showed the formation of different coordination modes depending on the ligand structure. 相似文献
580.