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排序方式: 共有88条查询结果,搜索用时 31 毫秒
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V. I. Petrenko M. V. Avdeev V. M. Garamus M. Kubovcikova Z. Gažová K. Šipošová L. A. Bulavin L. Almásy V. L. Aksenov P. Kopcansky 《Physics of the Solid State》2014,56(1):129-133
The structure of filament amyloid aggregates of hen egg white lysozyme in water has been investigated by the small-angle X-ray scattering method. The experimental data are described by different cylindrical models, among which the best agreement is reached with the long helix model. A comparison of the results with the small-angle neutron scattering data reveals the influence of the heavy component of the solvent (a H2O/D2O mixture) on the structure of the filaments. 相似文献
5.
Jairo Amortegui Alexander Rodríguez-López Deicy Rodríguez Ana K. Carrascal Carlos J. Alméciga-Díaz Adelina del P. Melendez Oscar F. Sánchez 《Applied biochemistry and biotechnology》2014,172(7):3374-3389
Bacteriocins are low molecular peptides with antimicrobial activity, which are of great interest as food bio-preservatives and for treating diseases caused by pathogenic bacteria. In this study, we present the characterization of bacteriocins produced by Lactobacillus plantarum LE5 and LE27 isolated from ensiled corn. Bacteriocins were purified through ammonium sulfate precipitation and double dialysis by using 12- and 1-kDa membranes. Bacteriocins showed activity against Listeria innocua, Listeria monocytogenes, and Enteroccocus faecalis. Molecular weight was estimated through Tricine-SDS-PAGE and overloading the gel onto Mueller-Hinton agar seeded with L. monocytogenes, showing an inhibition zone between 5 and 10 kDa. NanoLC-MS/MS analysis allowed the identification of UPF0291 protein (UniProtKB/Swiss-Prot Q88VI7), which is also presented in other lactic acid bacteria without assigned function. Ab initio modeling showed it has an α-helix-rich structure and a large positive-charged region. Bacteriocins were stable between 4 and 121 °C and pH 2 and 12, and the activity was inhibited by SDS and proteases. Mode of action assay suggests that the bacteriocin causes of target microorganism. Taken together, these results describe a possible new class IIa bacteriocin produced by L. plantarum, which has a wide stability to physicochemical conditions, and that could be used as an alternative for the control of foodborne diseases. 相似文献
6.
Measurements of induced losses on primary coated single-mode fibers strained against the inner wall of loose tube cable materials are reported. Fibers have been chosen from current types such as match and depressed clad with mode field diameters (MFD) and cut-off wavelengths spanning the expected range of production tolerances. The loss dependence on MFD and cut-off is characterized, and the combination high MFD/low cut-off turns out to be the most bend sensitive parameter combination while the opposite case with low MFD/high cut-off gives the best performance. Different tube materials provide different bend loss performance depending on the microstructure of the tube and the amount and type of filling jelly. 相似文献
7.
Toxic metal complexes of macrocyclic cyclen molecule – synthesis,structure and complexing properties
M. Litecká R. Gyepes M. Vilková M. Almáši M. Walko 《Journal of Coordination Chemistry》2017,70(10):1698-1712
Toxic metal (Cd2+, Hg2+, Pb2+, and Ag+) complexes with the tetradentate macrocyclic ligand - cyclen (1,4,7,10-tetraazacyclododecane, [12]aneN4, L) were prepared and studied in the solid state by IR, X-ray diffraction, elemental and thermal analysis. Diffraction results have yielded three molecular structures, [Cd([12]ane-κ4N1,4,7,10)(NO3)2)] (1), [Hg([12]ane-κ4N1,4,7,10)(NO3-κ2O,O`)]NO3 (2), [Pb2([12]ane-κ4N1,4,7,10)2][Pb(NO3)6] (3) and one polymeric structure {[Ag2([12]ane-κ3N1,4,7)(μ2-[12]aneN10)](NO3)2?2H2O)}n (4) featuring a unique coordination mode not observed before with cyclen as a ligand. The monodentate (1) and chelate (with small bite angle 50.3(3)°, (2) coordination modes of nitrate ligands were confirmed. Stereochemically active 6s2 lone pair was suggested in 3 and DFT results confirmed no significant metal–metal covalent bond. The stability constants of the complexes with Cd2+ and Pb2+ ions were determined by potentiometric methods in aqueous solutions. Additionally, the structures of complexes in solution were observed by 1H NMR. Both methods confirm similar cyclen complexing properties toward Zn2+ biometal and Cd2+, Pb2+ toxic metals. 相似文献
8.
Vargová Z Almáši M Arabuli L Györyová K Zeleňák V Kuchár J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(2):788-793
The infrared spectra, elemental and thermal (TG/DTG and DTA) analyses of novel [Zn(cyclen-κ4N1,4,7,10)(HGly-κ2O,O')](ClO4)2 (1), and [Zn2(cyclen-κ4N1,4,7,10)2(μ-S-Ala-κ2N,O)](ClO4)(3)·2H2O (2) complexes (cyclen - 1,4,7,10-tetraazacyclododecane) were recorded and analyzed in the relation to their structural peculiarities. IR spectral data indicate both mono- or bidentate coordination mode of a carboxylate group in the prepared complexes (at pH≈9). The results indicate unusual bidentate carboxylate coordination mode (in complex (1)) toward to Zn2+-cyclen unit. Therefore the crystal structure determination of the crystalline complex [Zn(cyclen-κ4N1,4,7,10)(NO3-κ2O,O')](NO3) was attached in order to support the coordination mode assignment in complex (1). 相似文献
9.
Marczak W Czech B Almásy L Lairez D 《Physical chemistry chemical physics : PCCP》2011,13(13):6260-6269
Small-angle neutron scattering proved that molecules in aqueous solutions of pyridine, 2-methylpyridine and 2,6-dimethylpyridine form clusters. The clusters are dynamic aggregates consisting of hydrogen-bonded water-amine complexes. Strengthening of the hydrogen bonds between water and amine molecules due to the methyl groups in the ortho position in the pyridine ring makes the structures more stable, as was evidenced by relatively long times of the structural relaxation. The strong intermolecular forces affect the thermal expansion of the systems. No aggregates similar to those in aqueous systems are present in the methanolic ones. That points to the crucial role of water in the molecular clustering. A molecule of methanol, although capable of hydrogen bonding with the amines, cannot participate in larger structures because of the lack of protons that could form the enhanced network. Thus, even if the amine-methanol complexes occur, they are incapable of further association. It was shown that the co-operative nature of hydrogen bonds and the propensity of water to association are the main factors that determine the properties of aqueous systems. 相似文献
10.
In this paper, we consider a stochastic queueing model for the performance evaluaton of a real-life computer system consisting
of n terminals connected with a CPU. A user at terminal i has thinking and processing time depending on the index i. Let us
suppose that the operational system is subject to random breakdowns, which may be software or hardware ones, stopping the
service both at the terminals and at the CPU. The failure-free operation times of the system and the restoration times are
random variables. Busy terminals are also subject to random breakdowns not affecting the system operation. The failure-free
operation times and the repair times of a busy terminal i are random variables with distribution function depending on index
i. The breakdowns are serviced by a single repairman providing preemptive priority to the system's failure, while the restoration
at the terminals are carried out according to the FIFO rule. We assume that each user generates only one job at a time, and
he waits at the CPU before he starts thinking again, that is, the terminal is inactive while waiting at the CPU, and it cannot
break down. All random variables involved in the model construction are assumed to be exponentially distributed and independent
of each other. The aim of this paper is to investigate the effect of different service disciplines, such as FIFO, processor
sharing, priority processor sharing, and polling, on the main performance measures, such as utilizations, response times,
throughput, and mean queue length.
Supported by the Hungarian National Foundation for Scientific Research (grant No. ORKA T014974/95).
Proceedings of the Seminar on Stability Problems for Stochastic Models, Hajdúszoboszló. Hungary, 1997, Part II. 相似文献