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81.
Ultrafast dynamics and anionic active states of the flavin cofactor in cryptochrome and photolyase 总被引:1,自引:0,他引:1
Kao YT Tan C Song SH Oztürk N Li J Wang L Sancar A Zhong D 《Journal of the American Chemical Society》2008,130(24):7695-7701
We report here our systematic studies of the dynamics of four redox states of the flavin cofactor in both photolyases and insect type 1 cryptochromes. With femtosecond resolution, we observed ultrafast photoreduction of oxidized state flavin adenine dinucleotide (FAD) in subpicosecond and of neutral radical semiquinone (FADH(*)) in tens of picoseconds through intraprotein electron transfer mainly with a neighboring conserved tryptophan triad. Such ultrafast dynamics make these forms of flavin unlikely to be the functional states of the photolyase/cryptochrome family. In contrast, we find that upon excitation the anionic semiquinone (FAD(*-)) and hydroquinone (FADH(-)) have longer lifetimes that are compatible with high-efficiency intermolecular electron transfer reactions. In photolyases, the excited active state (FADH(-)*) has a long (nanosecond) lifetime optimal for DNA-repair function. In insect type 1 cryptochromes known to be blue-light photoreceptors the excited active form (FAD(*-)*) has complex deactivation dynamics on the time scale from a few to hundreds of picoseconds, which is believed to occur through conical intersection(s) with a flexible bending motion to modulate the functional channel. These unique properties of anionic flavins suggest a universal mechanism of electron transfer for the initial functional steps of the photolyase/cryptochrome blue-light photoreceptor family. 相似文献
82.
Magnetic mesoporous silica was prepared via embedding magnetite nanoparticles between channels of mesoporous silica (SBA‐15). The prepared composite (Fe3O4@SiO2‐SBA) was then reacted with 3‐chloropropyltriethoxysilane, sodium imidazolide and 2‐bromopyridine to give 3‐(pyridin‐2‐yl)‐1H‐imidazol‐3‐iumpropyl‐functionalized Fe3O4@SiO2‐SBA as a supported pincer ligand for Pd(II). The functionalized magnetic mesoporous silica was further reacted with [PdCl2(SMe2)2] to produce a supported N‐heterocyclic carbene–Pd(II) complex. The obtained catalyst was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray analysis, vibrating sample magnetometry, Brunauer–Emmett–Teller surface area measurement and X‐ray diffraction. The amount of the loaded complex was 80.3 mg g?1, as calculated through thermogravimetric analysis. The formation of the ordered mesoporous structure of SBA‐15 was confirmed using low‐angle X‐ray diffraction and transmission electron microscopy. Also, X‐ray photoelectron spectroscopy confirmed the presence of the Pd(II) complex on the magnetic support. The prepared magnetic catalyst was then effectively used in the coupling reaction of olefins with aryl halides, i.e. the Heck reaction, in the presence of a base. The reaction parameters, such as solvent, base, temperature, amount of catalyst and reactant ratio, were optimized by choosing the coupling reaction of 1‐bromonaphthalene and styrene as a model Heck reaction. N‐Methylpyrrolidone as solvent, 0.25 mol% catalyst, K2CO3 as base, reaction temperature of 120°C and ultrasonication of the catalyst for 10 min before use provided the best conditions for the Heck cross‐coupling reaction. The best results were observed for aryl bromides and iodides while aryl chlorides were found to be less reactive. The catalyst exhibited noticeable stability and reusability. 相似文献
83.
This paper considers how to optimally set the basestock level for a single buffer when demand is uncertain, in a robust framework. We present a family of algorithms based on decomposition that scale well to problems with hundreds of time periods, and theoretical results on more general models. 相似文献
84.
Hüseyin Ünver Mustafa Yıldız Aşkın Kiraz Nazan Ocak İskeleli Ahmet Erdönmez Başaran Dülger Tahsin Nuri Durlu 《Journal of chemical crystallography》2006,36(3):229-237
A new Schiff base compound has been synthesized by the reaction of 2-hydroxy-1-naphthaldehyde with 3,5-bis(trifluoromethyl)aniline.The title compound was characterized by elemental analysis, IR,1H NMR,13C NMR, and UV–Visible techniques.Its UV–Vis spectra was examined in polar and nonpolar solvents and in acidic and basic media. The crystal structure of the compound showed the OH group to be ortho to the imine group. It crystallizes in the monoclinic space group P21 with a = 11.328(2), b = 6.125(1), c = 11.937(2) ?, V = 825.1(2) ?3, D
x
= 1.543 g cm−3and Z = 2. An intramolecular O1- H⋯N1 [2.558(7) ?] hydrogen bond stabilizes the molecule. The compound has also been characterized by its antimicrobial activities. The ligand has been screened in vitro against the organisms Escherichia coli ATCC 11230, Staphylococcus aureus ATCC 6538, Klebsiella pneumoniae UC57, Micrococcus luteus La 2971, Proteus vulgaris ATCC 8427, Pseudomonas aeruginosa ATCC 27853, Mycobacterium smegmatis CCM 2067, Bacillus cereus ATCC 7064, and Listeria monocytogenes ATCC 15313, the yeast cultures Candida albicans ATCC 10231, Kluyveromyces fragilis NRRL 2415, Rhodotorula rubra DSM 70403, Debaryomyces hansenii DSM 70238, and Hanseniaspora guilliermondii DSM 3432. 相似文献
85.
Nuri Oncel 《Surface science》2006,600(20):4690-4693
The diffusion and binding of CO molecules on self organized Pt nanowires on Ge(0 0 1), have been studied by room temperature scanning tunneling microscopy. CO molecules are found to bind at the bridge position of the Pt dimers. The CO molecules are mobile at room temperature and perform an “unrestricted” one-dimensional random walk in defect-free regions of the Pt nanowires. 相似文献
86.
Nuri Murat Yagmurlu Yusuf Ucar Ihsan Celikkaya 《Journal of Applied Analysis & Computation》2018,8(5):1494-1510
In this study, the numerical behavior of the one-dimensional Regularized Long Wave (RLW) equation has been sought by the Strang splitting technique with respect to time. For this purpose, cubic B-spline functions are used with the finite element collocation method. Then, single solitary wave motion, the interaction of two solitary waves and undular bore problems have been studied and the effectiveness of the method has been investigated. The new results have been compared with those of some of the previous studies available in the literature. The stability analysis has also been taken into account by the von Neumann method. 相似文献
87.
The buckling and initial postbuckling behavior of clamped shallow spherical sandwich shells with dissimilar face sheets under a uniform pressure is studied. The numerical results show that the buckling and initial post-buckling behavior of clamped shallow spherical sandwich shells with dissimilar face sheets is similar to that of the corresponding homogeneous shell. 相似文献
88.
一个解剖基人体下肢的生物动力模型--第一部分: 模型描述 总被引:4,自引:1,他引:4
建立一个完整的解剖基人体下肢二维(矢状面内)生物动力模型,该模型仿真了人体下肢的生物动力运动,并可用来计算人体下肢在冲击外载荷或肌肉活性力的作用下,下肢的重要承力部位-膝关节处的结构力(包括:膝关节的咬合接触力、膝关节处四个主要韧带张力等)和人体下肢的肌肉群力;同时本模型也可用来计算人体下肢在运动期间,膝关节处的咬合位移以及膝关节和髋关节的屈伸位移等。另外,模型还为研究人工关节、人工韧带和人工肌肉 相似文献
89.
Meliha Burcu Gürdere Ali Cemal Emeç Osman Nuri Aslan Yakup Budak Mustafa Ceylan 《合成通讯》2016,46(6):536-545
The triethylamin-mediated addition of 2-aminoethanethiol hydrochloride to chalcone analogs was investigated. This addition, bearing a 2-thienyl group at the 3-position, gave the only addition adduct at room temperature in 3 h, whereas the chalcones bearing the 2-furyl group at the 1-position gave an addition-cyclization product (1, 4-thiazepine) in the same conditions. The effect of the groups to the reaction was investigated by changing the 1- and 3-position groups. The chalcones bearing the 2-thienyl group at the 1-position and the others afforded the mixture of products in different ratio at rt for 0.5–24 h. Moreover, the addition–cyclization products (1,4-thiazepine) were obtained under reflux conditions in 36 h. The structures of the synthesized compounds were elucidated by 1H NMR, 13C NMR, infrared, and elemental analysis. 相似文献
90.
Leila O. Khafizova Nuri M. Chobanov Mariya G. Shaibakova Natalya R. Popodko Tatyana V. Tyumkina Usein M. Dzhemilev 《Tetrahedron》2018,74(20):2482-2487
An original method for the synthesis of С5-С6 cyclic ketones and tetrasubstituted furans was developed based on the Cp2TiCl2-catalyzed reaction of symmetrical alkynes and α,ω-dicarboxylates in the presence of Mg and ЕtAlCl2. The length of the hydrocarbon chain between carboxyl groups in a,ω-dicarboxylic acid esters affects the chemoselectivity of the reaction. The formation of 2-alkylidene and 2-alkenyl cyclopent(hex)an-1-ones occurred in the reaction with esters of glutaric and adipic acids. α,ω-Dicarboxylic acid esters with more than four methylene units between carboxyl groups gave rise to substituted furans. Stereochemistry of 2-alkenyl cyclopent(hex)an-1-ones was determined based on the analysis of experimental and theoretical data obtained from DFT calculations. 相似文献