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Holger Moroder Jessica Steger Dagmar Graber Katja Fauster Krista Trappl Viter Marquez Dr. Norbert Polacek Priv.‐Doz. Dr. Daniel N. Wilson Dr. Ronald Micura Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(22):4056-4060
Translation of specific small peptides on the ribosome can confer resistance to macrolide antibiotics. To reveal the molecular details of this and related phenomena, stable RNA–peptide conjugates that mimic peptidyl‐tRNA would be desirable, especially for ribosome structural biology. A flexible solid‐phase synthesis strategy now allows efficient access to these highly requested derivatives without restriction on the RNA and peptide sequences.
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Eriksson J Malmsten M Tiberg F Callisen TH Damhus T Johansen KS 《Journal of colloid and interface science》2005,284(1):99-106
Enzymatic degradation of model cellulose films prepared by a spin-coating technique was investigated by ellipsometry. The cellulose films were prior to degradation characterized by ellipsometry, contact angle measurements, ESCA (electron spectroscopy for chemical analysis) and AFM (atomic force microscopy). At enzyme addition to preformed cellulose films an initial adsorption was observed, which was followed by a total interfacial mass decrease due to enzymatic degradation of the cellulose films. The degradation rate was found to be constant during an extended time of hours, whereafter the degradation leveled off. In parallel to the decreased interfacial mass, the cellulose degradation resulted in a thinner and more dilute interfacial film. At long degradation times, however, there was an expansion of the cellulose film. The enzyme concentration affected the degradation rate significantly, with a faster degradation at a higher enzyme concentration. The effects of pH, temperature, ionic strength and stirring rate in the cuvette were also investigated. 相似文献
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Dr. Anton H. Hofman Dr. Mehedi Reza Prof. Janne Ruokolainen Prof. Gerrit ten Brinke Prof. Katja Loos 《Angewandte Chemie (International ed. in English)》2016,55(42):13081-13085
The formation of unusual multilayered parallel lamellae‐in‐lamellae in symmetric supramolecular double‐comb diblock copolymers is presented. While keeping the concentration of surfactant fixed, the number of internal layers was found to increase with molecular weight M up to 34 for the largest block copolymer. The number of internal structures n was established to scale as M0.67 and therefore enables easy design of such structures with great precision. 相似文献
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Roy A. Meoded Dr. Reiko Ueoka Dr. Eric J. N. Helfrich Dr. Katja Jensen Nancy Magnus Prof. Dr. Birgit Piechulla Prof. Dr. Jörn Piel 《Angewandte Chemie (International ed. in English)》2018,57(36):11644-11648
Enzymatic core components from trans‐acyltransferase polyketide synthases (trans‐AT PKSs) catalyze exceptionally diverse biosynthetic transformations to generate structurally complex bioactive compounds. Here we focus on a group of oxygenases identified in various trans‐AT PKS pathways, including those for pederin, oocydins, and toblerols. Using the oocydin pathway homologue (OocK) from Serratia plymuthica 4Rx13 and N‐acetylcysteamine (SNAC) thioesters as test surrogates for acyl carrier protein (ACP)‐tethered intermediates, we show that the enzyme inserts oxygen into β‐ketoacyl moieties to yield malonyl ester SNAC products. Based on these data and the identification of a non‐hydrolyzed oocydin congener with retained ester moiety, we propose a unified biosynthetic pathway of oocydins, haterumalides, and biselides. By providing access to internal ester, carboxylate pseudostarter, and terminal hydroxyl functions, oxygen insertion into polyketide backbones greatly expands the biosynthetic scope of PKSs. 相似文献
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Dettmer K Nürnberger N Kaspar H Gruber MA Almstetter MF Oefner PJ 《Analytical and bioanalytical chemistry》2011,399(3):1127-1139
Trypsin/ethylenediaminetetraacetic acid (EDTA) treatment and cell scraping in a buffer solution were compared for harvesting
adherently growing mammalian SW480 cells for metabolomics studies. In addition, direct scraping with a solvent was tested.
Trypsinated and scraped cell pellets were extracted using seven different extraction protocols including pure methanol, methanol/water,
pure acetone, acetone/water, methanol/chloroform/water, methanol/isopropanol/water, and acid–base methanol. The extracts were
analyzed by GC-MS after methoximation/silylation and derivatization with propyl chloroformate, respectively. The metabolic
fingerprints were compared and 25 selected metabolites including amino acids and intermediates of energy metabolism were quantitatively
determined. Moreover, the influence of freeze/thaw cycles, ultrasonication and homogenization using ceramic beads on extraction
yield was tested. Pure acetone yielded the lowest extraction efficiency while methanol, methanol/water, methanol/isopropanol/water,
and acid–base methanol recovered similar metabolite amounts with good reproducibility. Based on overall performance, methanol/water
was chosen as a suitable extraction solvent. Repeated freeze/thaw cycles, ultrasonication and homogenization did not improve
overall metabolite yield of the methanol/water extraction. Trypsin/EDTA treatment caused substantial metabolite leakage proving
it inadequate for metabolomics studies. Gentle scraping of the cells in a buffer solution and subsequent extraction with methanol/water
resulted on average in a sevenfold lower recovery of quantified metabolites compared with direct scraping using methanol/water,
making the latter one the method of choice to harvest and extract metabolites from adherently growing mammalian SW480 cells. 相似文献
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