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排序方式: 共有97条查询结果,搜索用时 109 毫秒
71.
This paper addresses the use of different slotted pores in rotating membrane emulsification technology. Pores of square and rectangular shapes were studied to understand the effect of aspect ratio (1-3.5) and their orientation on oil droplet formation. Increasing the membrane rotation speed decreased the droplet size, and the oil droplets produced were more uniform using slotted pores as compared to circular geometry. At a given rotation speed, the droplet size was mainly determined by the pore size and the fluid velocity of oil through the pore (pore fluid velocity). The ratio of droplet diameter to the equivalent diameter of the slotted pore increased with the pore fluid velocity. At a given pore fluid velocity and rotation speed, pore orientation significantly influences the droplet formation rate: horizontally disposed pores (with their longer side perpendicular to the membrane axis) generate droplets at double the rate of vertically disposed pores. This work indicates practical benefits in the use of slotted membranes over conventional methods. 相似文献
72.
A theoretical and experimental study of alcohol/water and alcohol/alcohol solvent mixtures near a surface of N-(1-phenylethyl)-N'-[3-(triethoxysilyl)propyl]-urea (PEPU), a Pirkle-type chiral stationary phase, is presented. Molecular dynamics simulations are performed at room temperature for water/methanol, water/1-propanol, water/2-propanol, and methanol/1-propanol solvent mixtures confined between two PEPU surfaces. The interface was also prepared experimentally by attaching the PEPU molecules to atomic force microscopy tips and oxidized Si(111) substrates. Chemical force spectrometric measurements between such PEPU-terminated tips and samples were taken in the solvent mixtures, and the results are compared to the molecular dynamics study. We find that the extent of hydrogen bonding at the surface is the dominant contributor to the measured forces. 相似文献
73.
The diffusion of small palladium clusters on MgO(100) is theoretically investigated. It is found that small clusters can diffuse even faster than isolated adatoms by a variety of mechanisms (some of which are novel), such as dimer rotation, trimer walking, tetramer rolling, and sliding. The consequences of the diffusion of small clusters on the growth of Pd aggregates on MgO(100) are investigated, and it is shown that fast mobility of clusters larger than a single atom is essential to bring the theoretical results into agreement with the outcome of molecular beam epitaxy experiments. 相似文献
74.
We present (29)Si, (27)Al, and (67)Zn NMR evidence to show that silicate ions in alkaline solution form complexes with zinc(II) (present as zincate, Zn(OH)(3)(-) or Zn(OH)(4)(2-)) and, concomitantly, with aluminate (Al(OH)(4)(-)). Zincate reacts with monomeric silicate at pH 14-15 to form [(HO)O(2)Si-O-Zn(OH)(3)](4-) and with dimeric silicate to produce [HO-SiO(2)-O-SiO(2)-O-Zn(OH)(3)](6-). The exchange of Si between these free and Zn-bound sites is immeasurably fast on the (29)Si NMR time scale. The cyclic silicate trimer reacts relatively slowly and incompletely with zincate to form [(HO)(3)Zn{(SiO(3))(3)}](7-). The concentration of the cyclic trimer becomes further depleted because zincate scavenges the silicate monomer and dimer, with which the cyclic trimer is in equilibrium on the time scale of sample preparation. Identification of these zincate-silicate complexes is supported by quantum chemical theoretical calculations. Aluminate and zincate, when present together, compete roughly equally for a deficiency of silicate to form [(HO)(3)ZnOSiO(2)OH](4-) and [(HO)(3)AlOSiO(2)OH](3-) which exchange (29)Si at a fast but measurable rate. 相似文献
75.
Halliday GM Agar NS Barnetson RS Ananthaswamy HN Jones AM 《Photochemistry and photobiology》2005,81(1):3-8
This review of our work, presented at the Photocarcinogenesis Symposium of the 14th International Congress on Photobiology, shows that UV-A causes a similar number of gene mutations as UV-B in human skin cancer. Areas of about 20 keratinocytes from solar keratoses and squamous cell carcinomas, which are benign and malignant skin cancers, respectively, were sampled by laser capture microdissection. Automated sequencing of the p53 gene was used to detect mutations in these tumor areas, and the cause of the mutations was attributed on the basis of previously published studies. UV-A and UV-B caused similar numbers of p53 gene mutations in both benign and malignant human skin tumors, with UV-B-induced mutations being restricted to the upper areas of the tumors and UV-A-induced mutations predominating at the basal layer. Furthermore, each microdissected region within a tumor had distinct mutations showing that the skin tumors consisted of different clones of cells. This is not consistent with how human skin carcinogenesis is currently understood, and hypotheses to explain our data are presented. We propose that the UV-A waveband of sunlight is as important as UV-B in causing skin cancer in humans. 相似文献
76.
Yoshiki Katayama Kazuhide Nita Masahide Ueda Hiroshi Nakamura Makoto Takagi Keihei Ueno 《Analytica chimica acta》1985
New crown ethers carrying a pendent phenolic chromophore were synthesized. These crown ethers, on dissociation of the phenolic proton, provide lipophilic anions which can extract alkali metal cations into 1,2-dichloroethane by forming highly-colored uncharged metal complexes. Structural effects on the extraction were studied for possible use of these crown ethers as extraction—spectrophotometric reagents selective for alkali metals. The following factors are discussed in detail: (i) nature of the crown ether ring (ring size. aza-crown or standard crown ether), (ii) nature of the pendent phenolic group, and (iii) geometry between the crown ether center and pendent phenolic group. 15-Crown-5 or smaller ring-sized reagents favored the extraction of lithium ion when the basicity of the pendent phenolate was relatively high and a six-membered “chelate” ring was possible for the phenolate and the crown ether-bound metal. 15-Crown-5 type reagents were sodium-selective when an eight-membered “chelate” ring was possible between the phenolate and the crown ether-bound metal. 18-Crown-6 type reagents were generally potassium-selective. However, these selectivities were not absolute, and other structural parameters, steric and conformational, must be considered to explain in detail the selectivities of the individual reagents. 相似文献
77.
The structure of Pd clusters adsorbed on MgO(001) is determined by a combination of global-optimization methods using semiempirical potentials and density functional calculations. The transition to fcc clusters with (001) epitaxy is shown to take place in the size range 10相似文献
78.
MVN Murthy Urjit A Yajnik KRS Balaji G Bhattacharyya Amol Dighe Shashikant Dugad ND Hari Dass PK Kabir Kamales Kar D Indumathi John G Learned Debasish Majumdar NK Mondal MVN Murthy SN Nayak Sandip Pakvasa Amitava Raychaudhuri RS Raghavan G Rajasekaran R Ramachandran Alak K Ray Asim K Ray Saurabh Rindani HS Sharatchandra Rahul Sinha Nita Sinha S Umasankar Urjit A Yajnik 《Pramana》2000,55(1-2):347-355
We have identified some important and worthwhile physics opportunities with a possible neutrino detector located in India.
Particular emphasis is placed on the geographical advantage with a stress on the complimentary aspects with respect to other
neutrino detectors already in operation. 相似文献
79.
Cristina Nita Biao Zhang Joseph Dentzer Camélia Matei Ghimbeu 《Journal of Energy Chemistry》2021,(7):207-218
In recent years,hard carbon materials have gained significant interest as anode materials for Na-ion batteries.Biomass waste is considered one of the most inter... 相似文献
80.
Aurica P. Chiriac Alina Ghilan Iordana Neamtu Loredana E. Nita Alina G. Rusu Vlad Mihai Chiriac 《Macromolecular bioscience》2019,19(9)
(Nano)gels from macromolecular compounds—natural, synthetic, or a combination thereof, suitable crosslinkers—and conferred characteristics—such as degradability, size, charge, amphiphilicity, responsiveness, and softness—are capable of responding to the challenges imposed by bioengineering applications. Polysaccharide‐based gels have received particular attention in this field. This review addresses recent advancement in the use of (nano)gel structures prepared only from compounds based on gellan gum, heparin, chondroitin sulfate, carrageenan, guar gum, galactose, or agarose, which represent an important part of the special class of natural polymers, the polysaccharides. Also, future trends are taken into discussion regarding the (nano)gels' use in biomedical applications such as biomimetics, biosensors, artificial muscles, and chemical separations in relation with their ability to be used as a vehicle for various biomolecules due to their physicochemical properties, biocompatibility, and biodegradability. 相似文献