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101.
Biosynthesis of the Fluorinated Natural Product Nucleocidin in Streptomyces calvus Is Dependent on the bldA‐Specified Leu‐tRNAUUA Molecule
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Xi Ming Zhu Stefanie Hackl Dr. Maulik N. Thaker Dr. Lindsay Kalan Claudia Weber Dr. Dagmar S. Urgast Dr. Eva M. Krupp Alyssa Brewer Stephanie Vanner Anjuli Szawiola Grace Yim Prof. Jörg Feldmann Prof. Andreas Bechthold Prof. Gerard D. Wright Prof. David L. Zechel 《Chembiochem : a European journal of chemical biology》2015,16(17):2498-2506
Nucleocidin is one of the very few natural products known to contain fluorine. Mysteriously, the nucleocidin producer Streptomyces calvus ATCC 13382 has not been observed to synthesize the compound since its discovery in 1956. Here, we report that complementation of S. calvus ATCC 13382 with a functional bldA‐encoded Leu‐tRNAUUA molecule restores the production of nucleocidin. Nucleocidin was detected in culture extracts by 19F NMR spectroscopy, HPLC‐ESI‐MS, and HPLC‐continuum source molecular absorption spectroscopy for fluorine‐specific detection. The molecule was purified from a large‐scale culture and definitively characterized by NMR spectroscopy and high‐resolution MS. The nucleocidin biosynthetic gene cluster was identified by the presence of genes encoding the 5′‐O‐sulfamate moiety and confirmed by gene disruption. Two of the genes within the nucleocidin biosynthetic gene cluster contain TTA codons, thus explaining the dependence on bldA and resolving a 60‐year‐old mystery. 相似文献
102.
Cover Picture: Freezing the Bioactive Conformation to Boost Potency: The Identification of BAY 85‐8501, a Selective and Potent Inhibitor of Human Neutrophil Elastase for Pulmonary Diseases (ChemMedChem 7/2015)
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Dr. Franz von Nussbaum Dr. Volkhart M.‐J. Li Dr. Swen Allerheiligen Sonja Anlauf Dr. Lars Bärfacker Dr. Martin Bechem Dr. Martina Delbeck Dr. Michael Gerisch Dr. Heike Gielen‐Haertwig Dr. Helmut Haning Dagmar Karthaus Dr. Dieter Lang Dr. Klemens Lustig Dr. Daniel Meibom Prof. Dr. Joachim Mittendorf Dr. Martina Schäfer Dr. Jens Schamberger Dr. Adrian Tersteegen 《ChemMedChem》2015,10(7):1117-1117
103.
Shang L Azadfar N Stockmar F Send W Trouillet V Bruns M Gerthsen D Nienhaus GU 《Small (Weinheim an der Bergstrasse, Germany)》2011,7(18):2614-2620
A facile strategy to synthesize water-soluble fluorescent gold nanoclusters (Au NCs) stabilized with the bidentate ligand dihydrolipoic acid (DHLA) is reported. The DHLA-capped Au NCs are characterized by UV-vis absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The Au NCs possess many attractive features including ultrasmall size, bright near-infrared luminescence, high colloidal stability, and good biocompatibility, making them promising imaging agents for biomedical and cellular imaging applications. Moreover, their long fluorescence lifetime (>100 ns) makes them attractive as labels in fluorescence lifetime imaging (FLIM) applications. As an example, the internalization of Au NCs by live HeLa cells is visualized using the FLIM technique. 相似文献
104.
Li Shang Linxiao Yang Jürgen Seiter Marita Heinle Gerald Brenner‐Weiss Dagmar Gerthsen G. Ulrich Nienhaus 《Advanced Materials Interfaces》2014,1(2)
Despite intense research on biological and biomedical applications of nanoparticles, our understanding of their basic interactions with the biological environment is still incomplete. Systematic variation of the physicochemical properties of the nanoparticles is widely seen as a promising strategy to obtain further insights. In view of the key role of the protein adsorption layer forming on nanoparticles in contact with biofluids, we systematically varied the surface charge of proteins adsorbing onto nanoparticles by chemical modification so as to examine the effect of Coulomb forces in modulating nano‐bio interactions. We chose human serum albumin (HSA) as a model protein and ultra‐small, negatively charged fluorescent gold nanoclusters (AuNCs) as model nanoparticles. By using fluorescence and CD spectroscopies, we measured binding affinities and structural changes upon binding of the HSA variants. The strengths of the protein‐nanoparticle interactions were found to change substantially upon modifying the surface charge of HSA. Furthermore, by using inductively coupled plasma optical emission spectroscopy, confocal fluorescence microscopy, scanning transmission electron microscopy and cell viability assays, we observed that cellular interactions of the AuNCs, including their adherence to cell membranes, uptake efficiency and cytotoxicity, depended markedly on the different surface charges of the HSA variants adsorbed onto the nanoparticles. These results illustrate vividly that the cellular responses to nanoparticle exposure depend on the specific properties of the proteins that adsorb onto nanoparticles from biofluids. 相似文献
105.
Maass Anne; Milesi Angela; Zabbini Silvia; Stahlberg Dagmar 《Canadian Metallurgical Quarterly》1995,68(1):116
The linguistic intergroup bias describes the tendency to communicate positive in-group and negative out-group behaviors more abstractly than negative in-group and positive out-group behaviors. This article investigated whether this bias is driven by differential expectancies or by in-group protective motives. In Exp 1, northern and southern Italian participants (N?=?151) described positive and negative behaviors of northern or southern protagonists that were either congruent or incongruent with stereotypic expectancies. Regardless of valence, expectancy-congruent behaviors were described more abstractly than incongruent ones. Exp 2 (N?=?40) showed that language is used in an equally biased fashion for individuals as previously demonstrated for groups. Exp 3 (N?=?192) induced expectancies experimentally and found greater abstraction for expectancy-congruent behaviors regardless of valence. All experiments confirmed the differential expectancy approach. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
106.
107.
Ledentsov N Bimberg D Hopfer F Mutig A Shchukin V Savel'ev A Fiol G Stock E Eisele H Dähne M Gerthsen D Fischer U Litvinov D Rosenauer A Mikhrin S Kovsh A Zakharov N Werner P 《Nanoscale research letters》2007,2(9):417-429
We report on progress in growth and applications of submonolayer (SML) quantum dots (QDs) in high-speed vertical-cavity surface-emitting
lasers (VCSELs). SML deposition enables controlled formation of high density QD arrays with good size and shape uniformity.
Further increase in excitonic absorption and gain is possible with vertical stacking of SML QDs using ultrathin spacer layers.
Vertically correlated, tilted or anticorrelated arrangements of the SML islands are realized and allow QD strain and wavefunction
engineering. Respectively, both TE and TM polarizations of the luminescence can be achieved in the edge-emission using the
same constituting materials. SML QDs provide ultrahigh modal gain, reduced temperature depletion and gain saturation effects
when used in active media in laser diodes. Temperature robustness up to 100 °C for 0.98 μm range vertical-cavity surface-emitting
lasers (VCSELs) is realized in the continuous wave regime. An open eye 20 Gb/s operation with bit error rates better than
10−12 has been achieved in a temperature range 25–85 °C without current adjustment. Relaxation oscillations up to ∼30 GHz have been realized indicating feasibility of 40 Gb/s signal transmission.
A. V. Savel’ev—on leave from the Abraham Ioffe Physical Technical Institute, Politekhnicheskaya 26, 194021, St. Petersburg,
Russia. 相似文献
108.
Petr Svoboda Rajesh Theravalappil Sameepa Poongavalappil Jarmila Vilcakova Dagmar Svobodova Pavel Mokrejs Antonin Blaha 《Polymer Engineering and Science》2012,52(6):1241-1249
A series of ethylene–octene copolymer (EOC) composites have been prepared by melt‐mixing with different weight ratios of expandable graphite filler (0–50% by weight). Electrical conductivity [both alternating current (AC) and direct current (DC)] and thermal conductivity studies were carried out. Effect of filler loading and frequency on electrical conductivity was studied. DC conductivity has increased from 1.51 × 10?13 S cm?1 to 1.17 × 10?1 S cm?1. Percolation threshold by DC and also AC methods was observed at about 16 vol% of the filler. Real part of permittivity was found to be decreasing with increase in frequency while conductivity was increasing. Thermal conductivity was also found to be increasing gradually from 0.196 to 0.676 Wm?1 K?1 which is about 245% increase. Graphite not only increases the electrical and thermal conductivities but at and above 40 wt%, also acts as a halogen‐free, environmental friendly flame retardant. Shore‐A hardness of EOC/graphite composites shows that even with high graphite loading, the hardness is increased from about 50–68 only so that the rubbery nature of the composite is not affected very much. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers 相似文献
109.
Above-ground carbon storage by urban trees in Leipzig, Germany: Analysis of patterns in a European city 总被引:2,自引:0,他引:2
Many aspects of global change, including carbon dioxide emissions, have been attributed to urban areas. On the other hand, cities have been found to provide valuable ecosystem services such as carbon storage. The aim of this study is to estimate the above-ground carbon storage in trees in the central European city of Leipzig and produce spatially explicit carbon storage maps. We used stratified random sampling across 19 land cover classes using 190 sample plots to measure carbon storage. In addition, we derived canopy cover from color-infrared orthophotos using an object-oriented approach and Random Forest machine learning. Finally, we apply an error assessment method that includes sampling error, but also uncertainty stemming from allometric equations, and that so far has only been applied to rural forests. The total above ground carbon stock of Leipzig was estimated using both land cover and canopy cover, which was more laborious than just using land cover but reduced the standard error. Canopy cover was approximately 19% of the city area. Leipzig's above-ground carbon storage was estimated to be 316,000 Mg C at 11 Mg C ha−1. The distribution of carbon storage across the city showed the highest values at intermediate urbanization levels. Carbon storage in the city of Leipzig was in the lower range compared to cities in Europe, Asia and the USA, and our results indicate that great care should be taken when transferring values between cities. We provide spatially explicit and detailed maps of above-ground storage that can contribute to ecosystem services assessments. 相似文献
110.
Martaus J Cambel V Gregusová D Kúdela R Fedor J 《Journal of nanoscience and nanotechnology》2010,10(7):4448-4453
A novel approach to local anodic oxidation technique, which leads to approximately equal 50 nm wide line patterns, is described. The technique is utilized to prepare quantum point contact on a low-mobility semiconductor heterostructure. Transport measurements show quantized conductance in zero magnetic field at 4.2 K thanks to very short one-dimensional constriction. The technique is also used for the definition of low-to-room temperature sub-micrometer Hall probes to show its applicability for the room temperature applications. The magnetic-field resolution and the sensitivity of the probes are evaluated in dependence of the probe dimensions, bias current, and temperature. The 200-nm probe shows magnetic-field resolution of 47 microT/(Hz)(1/2) at 140 Hz and at 4.2 K, when it is driven by 5 microA bias current. The novel approach is promising for the development of the future nano-devices operated both at low and room temperatures. To our knowledge, local anodic oxidation technique applied directly to shallow semiconductor heterostructure has been successfully used for the room temperature application for the first time. 相似文献