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61.
Nianjun Yang Rene Hoffmann Waldemar Smirnov Armin Kriele Christoph E. Nebel 《Electrochemistry communications》2010,12(9):1218-1221
Nanotextured diamond surfaces with geometrical properties close to protein dimensions were used for the realization of direct electron transfer of cytochrome c (cyt c) without any covalent bonding. The peroxidase activity of native and denatured cyt c was also investigated. Cyclic voltammograms of native cyt c show quasi-reversible electron transfer reactions, while no heme redox activity is detected for denatured cyt c. Unfolding (denaturation) of cyt c can be achieved in the presence of hydrogen peroxide. Partially or fully denatured cyt c showed higher peroxidase activity than native cyt c. This is because denatured cyt c loses its tertiary structure and hydrogen peroxide is easier to access the heme redox center. The apparent Michaelis–Menten constant Km for native and denatured cyt c has been determined to be 0.23 mM and 0.08 mM. 相似文献
62.
Waldemar Tomaszewski Vladimir M. Gun’ko Roman Leboda Jadwiga Skubiszewska-Zięba 《Central European Journal of Chemistry》2010,8(4):750-757
Solid phase extraction (SPE) of methoxy- and methylenedioxyamphetamines from diluted aqueous solutions was investigated on
carbon and polymeric adsorbents of different textures and chemical compositions. Those adsorbents were applied cartridges
packed with three chemically modified carbons prepared from plum stones (initial A2PS, oxidized A2PS-O, and reduced A2PS-H)
and commercially available adsorbents (polymeric LiChrolut EN, graphitized Hypercarb and Carboprep). Several factors influence
the recovery rates of amphetamine derivatives such as the polarity of adsorbates (free energy of salvation), the specific
surface area and surface composition of adsorbents, and the solvent characteristics. Different combinations of these factors
affect the recovery rate (R1) for high- and low-surface area adsorbents. The minimal R1 values are observed for an amphetamine
derivative at a maximal solvation effect and for a set of amphetamines adsorbed on graphitized carbons.
相似文献
63.
Vernaleken A Weitenberg J Sartorius T Russbueldt P Schneider W Stebbings SL Kling MF Hommelhoff P Hoffmann HD Poprawe R Krausz F Hänsch TW Udem T 《Optics letters》2011,36(17):3428-3430
We report on single-pass high-harmonic generation (HHG) with amplified driving laser pulses at a repetition rate of 20.8?MHz. An Yb:YAG Innoslab amplifier system provides 35?fs pulses with 20?W average power at 1030?nm after external pulse compression. Following tight focusing into a xenon gas jet, we observe the generation of high-harmonic radiation of up to the seventeenth order. Our results show that state-of-the-art amplifier systems have become a promising alternative to cavity-assisted HHG for applications that require high repetition rates, such as frequency comb spectroscopy in the extreme UV. 相似文献
64.
Waldemar Grundmann 《Journal of Theoretical Probability》2014,27(1):278-300
In this paper, we derive sharp estimates and asymptotic results for moment functions on Jacobi type hypergroups. Moreover, we use these estimates to prove a central limit theorem (CLT) for random walks on Jacobi hypergroups with growing parameters $\alpha ,\beta \rightarrow \infty $ . As a special case, we obtain a CLT for random walks on the hyperbolic spaces ${H}_d(\mathbb F )$ with growing dimensions $d$ over the fields $\mathbb F =\mathbb R ,\ \mathbb C $ or the quaternions $\mathbb H $ . 相似文献
65.
F. P. Treadwell Emil C. Behrend Waldemar Krühn und Camille Poulenc 《Fresenius' Journal of Analytical Chemistry》1905,44(2):111-112
Ohne Zusammenfassung 相似文献
66.
Static headspace sampling and headspace solid-phase microextraction have been applied for the determination of the low molecular mass aldehydes—markers of edible oil oxidation. Preconcentration and determination conditions for the two procedures were optimized. LODs LOQs and repeatability of a standard mixture were established for all investigated compounds. Both methods of sampling were applied to the analysis of samples of rapeseed and sunflower oils. It appears that solid-phase microextraction is better than headspace sampling for the analysis of volatile oxidation products. Solid-phase microextraction can be conducted at a much lower temperature and has lower LOD values and better repeatability than headspace sampling. 相似文献
67.
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69.
Agata Krakowska Witold Reczyński Włodzimierz Opoka Waldemar Turski 《International journal of environmental analytical chemistry》2015,95(9):855-866
Honey is a sweet product made by bees using nectar from flowers. Concentrations of Ca, K, Mg, Fe, Zn, Mn, Cu, Pb and Cd were determined in 13 honey samples from the selected regions around the world. Levels of Ca, Mg, Cu, Fe, Zn and Mn were measured using flame atomic absorption spectrometry (FAAS). Potassium concentration was determined via flame photometry. Concentrations of Cd and Pb were determined using the electrothermal technique (ETAAS). It was estimated that the examined samples of honey from Greece, Turkey, Spain, Poland, Mexico, Argentina and Italy were of good quality in terms of metal concentrations (compliant with the norms referring to food products – WHO, Fifty-third Report of the joint FAO/WHO Expert Committee on Food Additives; Technical Report Series 776, Geneva), although the analysed samples were not free of heavy metals. The concentrations of the elements in the honey samples ranged from 2.38 to 9.31 μg · g?1 for Zn, from 3.86 to 35.10 μg · g?1 for Fe, from 0.19 to 21.64 μg · g?1 for Mn, from 49.53 to 1006.90 μg · g?1 for Ca, from 388.25 to 4761.50 μg · g?1 for K and from 0.20 to 1.53 μg · g?1 for Cu and regarding heavy metals from 0.11 to 2.78 μg · g?1 for Pb and from 0.02 to 0.44 μg · g?1 for Cd. According to these results it was found that the concentrations of heavy metals in the honey samples (except for alfalfa honey and eucalyptus honey from Italy) were under the acceptable limits for foods set out by the FAO/WHO. It was confirmed that the application of chemometric tools supports the extraction of significant information from analytical data, even though the availability of samples is not fully sufficient (this problem is often encountered in environmental analyses). 相似文献
70.
The reagentless and oxygen‐independent biosensors for ethanol were developed based on the covalent immobilization of alcohol dehydrogenase (ADH) and its cofactor nicotinamide adenine dinucleotide (NAD+) on chitosan (CHIT) chains. The CHIT‐NAD+‐ADH structures were adsorbed onto carbon nanotubes (CNT) in order to provide a signal transduction based on the recycling of redox states of NAD cofactor at CNT (detection limit, 8–30 µM ethanol; dynamic range up to 20 mM). The CHIT‐NAD+‐dehydrogenase/CNT hybrid material represents a general approach to the development of dehydrogenases‐based electrochemical biosensors. Interestingly, the CHIT‐NAD+ solutions preserved their enzymatic activity even after five years of storage at 4 °C. 相似文献