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排序方式: 共有173条查询结果,搜索用时 15 毫秒
91.
Arja Sarpola Heikki Hellman Vesa Hietapelto Jorma Jalonen Jukka Jokela Jaakko Rämö Jaakko Saukkoriipi 《Polyhedron》2007
Hydrolysis and speciation of aluminium sulfate octadecahydrate Al2(SO4)3·18H2O was studied by electrospray time of flight mass spectrometry (ESI TOF MS). Several novel polymeric species were determined. Highly charged polymers, characterized by other methods, such as the Keggin cation [Al13O4(OH)24(H2O)12]7+ and the octameric aluminium hydroxide cluster [Al8(OH)14(H2O)18](SO4)5 16H2O, were found using ESI-MS as the anions [Al13O4(OH)25(SO4)4]2− and [Al8O(OH)14(SO4)5(H2O)4]2−. All the main species identified contained sulfate or hydrogen sulfate. The compositions of the determined ions mimicked those of several stable mineral forms. 相似文献
92.
Hirotoshi Furusho Jorma Hölsä Taneli Laamanen Mika Lastusaari Janne Niittykoski Yasuo Okajima Aishi Yamamoto 《Journal of luminescence》2008,128(5-6):881-884
The Sr2MgSi2O7:Eu2+,Dy3+ materials were prepared with a solid state reaction and their microscopic structure (at 295 K only) and luminescence were studied at selected temperatures between 150 and 295 K. Undisturbed Sr crystal planes were common in the TEM images of the undoped Sr2MgSi2O7 material, whereas with Eu2+ doping more disturbed planes were observed even in the nanometer scale. With Dy3+ co-doping, a large number of small lattice domains created by the discontinuities in the crystal structure was observed. The domains with different orientations seem to be centered around point defects. The decay curves of Sr2MgSi2O7:Eu2+,Dy3+ showed fast (ms scale) persistent luminescence. The intensity of persistent luminescence increased considerably between 200 and 250 K while remaining constant in the ranges of 150–200 and 250–295 K. The changes were used to study the depth of the traps. In general, Dy3+ co-doping was found to deepen the traps. 相似文献
93.
Summary An ARC/CL coded wheat flour reference material (ARC/CL RM) with established recommended concentration values for 12 elements [1,2] was further characterized for P, K and Cr contents by means of an intercomparison study. Minor corrections were made to earlier recommended values in accordance with new results obtained. Fifteen laboratories using a total of 11 methods based on six entirely different analytical principles participated in the intercomparison study. The medians and standard deviations were calculated for the results of the intercomparison study. After rejecting as outliers values falling outside the median ± sd, the present recommended values were obtained by recalculating the median and 95% confidence limits. Recommended values were established for the major elements Ca, K, Mg, P, the minor elements Cu, Fe, Mn, Zn, and the trace elements Mo, Cr, Ni and Se. The relative standard deviations for the 95% confidence limits of the medians were lower than 10% for major and minor elements, 11% for Mo and 18% for Cr. All of the recommended concentration values fell into category A, having a high degree of confidence. The present RM, with its 16 recommended concentrations, is of value for use in nutritional, food composition and contaminant monitoring studies. 相似文献
94.
95.
Jaakko Paasi Jorma Lehtonen Markku Lahtinen Lauri Kettunen 《Physica C: Superconductivity and its Applications》1998,310(1-4):62-66
A formulation for the computation of AC losses in technical HTS conductors by using commercial FEM packages developed for two-dimensional computation of electromagnetic problems is presented. The formulation takes into account the real current density–electric field characteristic of a conductor and the spatial dependence of the current density. Having presented the formulation, example runs comparing transport current loss behaviour between HTS and LTS conductors are given. 相似文献
96.
Tero Kumpulainen Jussi Pekkanen Jani Valkama Jarmo Laakso Reijo Tuokko Matti Mäntysalo 《Optics & Laser Technology》2011,43(3):570-576
New manufacturing methods are being sought for electronics production. Printable electronics is a promising method for producing low cost and large-scale electronics. In printable electronics nanoparticle inks printed on the surface of substrate contain additives, such as dispersing agent and carrier fluids that provide good printing properties by changing the viscosity and separating the nanoparticles of the ink. In the sintering process ink particles are heated to a certain, ink-specific temperature. During the sintering process the carrier fluid and dispersing agents are evaporated from the ink. Additional heating after evaporation causes the nanoparticles to start to agglomerate. A small particle size allows the use of a considerably lower sintering temperature than with bulk silver, for example 220 °C. The sintering process is usually utilized with a convection oven, with a long sintering time, and the thermal load on the surrounding material can become too great as components and patterns are formed from layers of different type inks. Hence, alternative sintering methods are sought. This paper describes tests done with two different types of laser; pulsed and continuous wave lasers. Laser sintering enables short sintering times and selective sintering, making it possible for printed structures to contain fragile active components produced with other technologies. 相似文献
97.
Antti J. Koivisto Maija M?kinen Elina M. Rossi Hanna K. Lindberg Mirella Miettinen Ghita C.- M. Falck Hannu Norppa Harri Alenius Anne Korpi Joakim Riikonen Esa Vanhala Minnamari Vippola Pertti Pasanen Vesa-Pekka Lehto Kai Savolainen Jorma Jokiniemi Kaarle H?meri 《Journal of nanoparticle research》2011,13(7):2949-2961
This study presents a novel exposure protocol for synthesized nanoparticles (NPs). NPs were synthesized in gas phase by thermal decomposition of metal alkoxide vapors in a laminar flow reactor. The exposure protocol was used to estimate the deposition fraction of titanium dioxide (TiO2) NPs to mice lung. The experiments were conducted at aerosol mass concentrations of 0.8, 7.2, 10.0, and 28.5 mg m?3. The means of aerosol geometric mobility diameter and aerodynamic diameter were 80 and 124 nm, and the geometric standard deviations were 1.8 and 1.7, respectively. The effective density of the particles was approximately from 1.5 to 1.7 g cm?3. Particle concentration varied from 4 × 105 cm?3 at mass concentrations of 0.8 mg m?3 to 12 × 106 cm?3 at 28.5 mg m?3. Particle phase structures were 74% of anatase and 26% of brookite with respective crystallite sized of 41 and 6 nm. The brookite crystallites were approximately 100 times the size of the anatase crystallites. The TiO2 particles were porous and highly agglomerated, with a mean primary particle size of 21 nm. The specific surface area of TiO2 powder was 61 m2 g?1. We defined mice respiratory minute volume (RMV) value during exposure to TiO2 aerosol. Both TiO2 particulate matter and gaseous by-products affected respiratory parameters. The RMV values were used to quantify the deposition fraction of TiO2 matter by using two different methods. According to individual samples, the deposition fraction was 8% on an average, and when defined from aerosol mass concentration series, it was 7%. These results show that the exposure protocol can be used to study toxicological effects of synthesized NPs. 相似文献
98.
Pragya Verma Arnulf Rosspeintner Bogdan Dereka Eric Vauthey Tatu Kumpulainen 《Chemical science》2020,11(30):7963
Excited-state proton transfer (ESPT) to solvent is often explained according to the two-step Eigen–Weller model including a contact ion pair (CIP*) as an intermediate, but general applicability of the model has not been thoroughly examined. Furthermore, examples of the spectral identification of CIP* are scarce. Here, we report on a detailed investigation of ESPT to protic (H2O, D2O, MeOH and EtOH) and aprotic (DMSO) solvents utilizing a broadband fluorescence technique with sub-200 fs time resolution. The time-resolved spectra are decomposed into contributions from the protonated and deprotonated species and a clear signature of CIP* is identified in DMSO and MeOH. Interestingly, the CIP* intermediate is not observable in aqueous environment although the dynamics in all solvents are multi-exponential. Global analysis based on the Eigen–Weller model is satisfactory in all solvents, but the marked mechanistic differences between aqueous and organic solvents cast doubt on the physical validity of the rate constants obtained.Time-resolved broadband fluorescence facilitates direct observation of reaction intermediates in excited-state proton transfer to solvent in protic and aprotic solvents. 相似文献
99.
Jorma Kumpulainen Maija Paakki Raija Tahvonen 《Fresenius' Journal of Analytical Chemistry》1988,332(6):685-688
Summary A potato reference material (RM) was prepared for the analytical quality control program to be employed by the Sub-network on Trace Elements in Food of the FAO European Co-operative Network on Trace Elements. Approximately 50 kg of commercially available potato granules prepared from baked, mashed and roller-dried potatoes, containing 2.8% ash and 3 mg/kg added butylhydroxyanisole was purchased. The granules were carefully homogenised in large glass cylinders followed by division into 50 g portions into numbered acid-washed bottles. The bottled material was tested for homogeneity by taking ten bottles throughout the bottling line and determining by validated atomic absorption spectrometric methods 1.0 g samples for seven mineral elements. Homogeneity for Mg, Ca, Zn, Fe, Mo, Ni and Cd was better than 5%. An international network on experienced, high-quality reference laboratories was established to conduct an interlaboratory comparison study on the determination of 14 mineral elements in the RM. A total of seven methods based on independent analytical principles were employed by the reference laboratories. After excluding outlying analytical results, the criteria defined by the IAEA were used for classification of the overall medians obtained through the interlaboratory comparison study. The relative standard deviations for the 95% confidence limits of the medians were as follows: P=4.2%, K=0.7%, Na=4.7%, Ca=5.5%, Mg=2.4%, Fe=9.3%, Mn=4.0%, Zn=3.6%, Cu=4.7%, Mo=23%, Ni=22%, Cr=19%, Pb=11% and Cd=4.6%. With the exception of Cr, all of the recommended concentration values obtained for the above indicated elements fell into category A, i.e. values recommended with a high degree of confidence according to the classification criteria of the IAEA. The present RM is the only certified potato RM currently available for mineral elements.
Charakterisierung eines Kartoffel-Referenzmaterials für Haupt-, Neben- und Spurenelemente相似文献
100.