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71.
72.
Adri van den Hoogenband Jos H.M. Lange Jack A.J. den Hartog Remco Henzen Jan Willem Terpstra 《Tetrahedron letters》2007,48(26):4461-4465
A highly efficient synthetic approach to novel 4-bromo-N-substituted oxindoles is described. The method involves a mild intramolecular copper-catalyzed amidation reaction of N-substituted 2,6-dibromophenylacetamides. In contrast to our recently published palladium-catalyzed amidation reaction, no concomitant dimerization on the 3-position of the formed oxindole occurs. 相似文献
73.
Natural zircon is irradiated internally by U and Th impurities. After exposure to ionizing irradiation zircon exhibits thermoluminescence (TL), which can be used to calculate the irradiation dose and the sample age. A kinetic model for TL of zircon developed earlier is used to model the processes relevant for dating. The response of zircon to irradiation at different dose rates is simulated for different temperatures. Several scenarios for the dating procedure are considered, including laboratory added irradiation, fading and preheat. It is shown that by irradiating the sample at elevated temperatures one can imitate natural irradiation, i.e. it is possible to reproduce the structural state of the trap system (distribution functions of filled electron and hole traps), which is responsible for the TL behavior. This implies that the dose dependence of the TL signal from samples, which had been irradiated under natural conditions, can be produced by irradiation at an elevated temperature. 相似文献
74.
Formation of vacancy clusters in irradiated crystals is considered taking into account radiation-induced Schottky defect emission (RSDE) from extended defects. RSDE acts in the opposite direction compared with Frenkel pair production, and it results in the radiation-induced recovery processes. In the case of alkali halides, Schottky defects can be produced as a result of the interaction of extended defects with excitons, as has been suggested by Seitz in 1954. We consider a model that takes into account excitonic mechanisms for the creation of both Frenkel and Schottky defects, and which shows that although the contribution of the latter mechanism to the production of primary defects may be small, its role in the radiation-induced evolution of microstructure can be very significant. The model is applied to describe the evolution of sodium colloids and the formation of voids in NaCl, which is followed by a sudden fracture of the material, presenting a potential problem in rock salt-based nuclear waste repositories. The temperature, dose rate and dose dependence of colloid growth in NaCl doped with different types of impurities is analyzed. We have found that colloid growth may become negative below a threshold temperature (or above a threshold dose rate), or below a certain impurity concentration, which is determined by the RSDE, that depends strongly on the type and concentration of the impurities. The results obtained with the model are compared with experimental observations. 相似文献
75.
Läppchen T Pinas VA Hartog AF Koomen GJ Schaffner-Barbero C Andreu JM Trambaiolo D Löwe J Juhem A Popov AV den Blaauwen T 《Chemistry & biology》2008,15(2):189-199
The cytoskeletal proteins, FtsZ and tubulin, play a pivotal role in prokaryotic cell division and eukaryotic chromosome segregation, respectively. Selective inhibitors of the GTP-dependent polymerization of FtsZ could constitute a new class of antibiotics, while several inhibitors of tubulin are widely used in antiproliferative therapy. In this work, we set out to identify selective inhibitors of FtsZ based on the structure of its natural ligand, GTP. We found that GTP analogs with small hydrophobic substituents at C8 of the nucleobase efficiently inhibit FtsZ polymerization, whereas they have an opposite effect on the polymerization of tubulin. The inhibitory activity of the GTP analogs on FtsZ polymerization allowed us to crystallize FtsZ in complex with C8-morpholino-GTP, revealing the binding mode of a GTP derivative containing a nonmodified triphosphate chain. 相似文献
76.
Gangadhara S Craig D Ennis DA Hartog DJ Fiksel G Prager SC 《Physical review letters》2007,98(7):075001
The impurity ion temperature evolution has been measured during three types of impulsive reconnection events in the Madison Symmetric Torus reversed field pinch. During an edge reconnection event, the drop in stored magnetic energy is small and ion heating is observed to be limited to the outer half of the plasma. Conversely, during a global reconnection event the drop in stored magnetic energy is large, and significant heating is observed at all radii. For both kinds of events, the drop in magnetic energy is sufficient to explain the increase in ion thermal energy. However, not all types of reconnection lead to ion heating. During a core reconnection event, both the stored magnetic energy and impurity ion temperature remain constant. The results suggest that a drop in magnetic energy is required for ions to be heated during reconnection, and that when this occurs heating is localized near the reconnection layer. 相似文献
77.
F. G. Cherkasov S. G. L'vov D. A. Tikhonov H. W. Den Hartog D. I. Vainshtein 《辐射效应与固体损伤》2013,168(6-12):643-647
ESR, NMR and static magnetic susceptibility measurements of heavily irradiated NaCl-K and NaCl-KBF 4 are reported. Up to 10% of the NaCl-molecules are transformed into metallic Na nanoparticles and Cl 2 precipitates. In addition, there are paramagnetic F- and F-aggregates, which are coupled by exchange interactions to the conduction electrons in the nanoparticles. Above 160 v K the NMR and ESR signals of NaCl-K and NaCl-KBF 4 show Pauli paramagnetism and the properties of the Na nanoparticles are similar to bulk sodium. A single ESR line is observed revealing exchange interaction between conduction electrons in the nano-particles and F-aggregates. The observed decrease of the ESR susceptibility with decreasing temperature is due to a metal-insulator transition. The conduction electrons are localized below 40 v K and the above mentioned F-aggregate centers contribute significantly to the overall ESR signal. For NaCl-KBF 4 we observed that with decreasing temperature the ESR line shifts towards lower fields due to antiferromagnetic ordering and internal magnetic fields. 相似文献
78.
Control system for detection of the illegal use of naturally occurring steroids in calves 总被引:1,自引:0,他引:1
Within the scope of the National Plan for Hormone Control in The Netherlands, a study was performed to develop a system for control of the illegal use of three naturally occurring hormones [oestradiol-17 beta (E2-17 beta), testosterone (T), progesterone (P)] for fattening purposes in animal production. Using a specific high-performance liquid chromatographic-radioimmunoassay method, reference values were established for concentrations of E2-17 beta, T and P and some of their metabolites in blood plasma and urine from untreated male and female veal calves. E2-17 beta levels of both male and female calves were less than 0.01 microgram/l in blood plasma and less than 0.2 microgram/l in urine. For male veal calves levels of T and epitestosterone (epiT) in blood plasma and urine varied widely. The P levels were less than 0.1-0.3 micrograms/l in blood plasma and less than 0.6-10 micrograms/l in urine from both male and female calves. To investigate the effect of anabolic treatment on the hormone levels in plasma and excreta, male veal calves were injected, subcutaneously into the dewlap, with a solution containing 20 mg of E2-17 beta benzoate and 200 mg of T propionate in 5 ml of arachis oil. Only the levels of E2-17 beta and E2-17 alpha in blood plasma and excreta were elevated until about one week after injection, compared with the untreated control calves and the reference values. T and epiT levels were similar in plasma and excreta from both untreated and treated animals. 相似文献
79.
D. L. Massart L. Buydens C. Armanino I. Broeckaert D. Coomans W. H. Dekker M. P. Derde M. Detaevernier K. H. Esbensen M. Forina M. Jonckheer L. Kaufman A. M. Massart-Leën J. Smeyers-Verbeke J. C. Den Hartog 《Analytical and bioanalytical chemistry》1982,311(4):448-448
This poster illustrates the lecture on Pattern Recognition and gives recently published and unpublished examples, mainly from the laboratory from the first author. The applications concern: - the determination of metabolic pathways of branched chain fatty acids (by clustering), - the development of a genetic classification of meteorites (by clustering), - the classification of cholinergic agents according to their interaction with different receptors (by clustering), - the structure of a data set consisting of gaschromatographic profiles in samples collected in pollution monitoring stations (by factor analysis and pattern recognition), - factors determining GLC behaviour of solutes (by factor analysis and multiple regression), - the classification of olive oils according to geographic origin (by principal components and pattern recognition), - the diagnosis of thyroid status (by pattern recognition). 相似文献
80.