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71.
Schmoeger E Paril C Tscheliessnig R Jungbauer A 《Journal of separation science》2010,33(20):3125-3136
The adsorption of plasmid DNA onto two different types of ceramic hydroxyapatite beads with a particle diameter of 20 μm, namely Ceramic Hydroxyapatite Type II and the Type III, which is not commercially available, were investigated. Type II and the Type III have a pore diameter of 80 and 240 nm, respectively. Equilibrium and dynamic binding capacity for a 4.9 kbp model plasmid on Ceramic Hydroxyapatite Type II and Type III were enhanced by addition of NaCl to the adsorption buffer. This result indicates that the adsorption mechanism cannot be solely explained by electrostatic interaction. The affinities of plasmid DNA for Ceramic Hydroxyapatite Type II (with a K(D) of ≈0.005 mg/mL) and to Hydroxyapatite Type III (with a K(D) of ≈0.045 mg/mL) were not affected by NaCl, whereas the binding capacity was. This observation corroborates the assumption that a change of the shape of the plasmid molecule is affected and could be the reason for increased binding capacity with salt. The maximal binding capacity shows that at least a part of the CHT II bead must be accessible for the plasmid, whereas CHT III can be saturated with the plasmid. In both cases, an extremely hindered transport takes place. 相似文献
72.
Clive S. Penkett Rupert O. Sims Simon Berritt Stephen P. Rushton Peter B. Hitchcock 《Tetrahedron》2006,62(40):9403-9409
Whilst seeking to improve the yield of a Heck-style arylation/fragmentation reaction using a silyloxy substituted meta photocycloadduct, an alternative reaction pathway was discovered that led to the formation of the unique oxidatively cyclised compound 8. This tricyclic ether is believed to form as the result of the meta photocycloadduct structure fragmenting to give a π-allyl palladium species and then subsequently being displaced by a neighbouring hydroxyl group. An attempt to develop an enantioselective version of this reaction via the desymmetrisation of a meso π-allyl palladium intermediate was made using the meta photocycloadduct derived from anisole and Z-but-2-ene-1,4-diol, however no enantioenrichment of the products could be detected. 相似文献
73.
Drake IJ Zhang Y Gilles MK Teris Liu CN Nachimuthu P Perera RC Wakita H Bell AT 《The journal of physical chemistry. B》2006,110(24):11665-11676
Aluminum coordination in the framework of USY and ZSM-5 zeolites containing charge-compensating cations (NH4+, H+, or Cu+) was investigated by Al K-edge EXAFS and XANES. This work was performed using a newly developed in-situ cell designed especially for acquiring soft X-ray absorption data. Both tetrahedrally and octahedrally coordinated Al were observed for hydrated H-USY and H-ZSM-5, in good agreement with 27Al NMR analyses. Upon dehydration, water desorbed from the zeolite, and octahedrally coordinated Al was converted progressively to tetrahedrally coordinated Al. These observations confirmed the hypothesis that the interaction of water with Br?nsted acid protons can lead to octahedral coordination of Al without loss of Al from the zeolite lattice. When H+ is replaced with NH4+ or Cu+, charge compensating species that absorb less water, less octahedrally coordinated Al was observed. Analysis of Al K-edge EXAFS data indicates that the Al-O bond distance for tetrahedrally coordinated Al in dehydrated USY and ZSM-5 is 1.67 angstroms. Simulation of k3chi(k) for Cu+ exchanged ZSM-5 leads to an estimated distance between Cu+ and framework Al atoms of 2.79 angstroms. 相似文献
74.
Rupert Lasser 《Journal of Mathematical Analysis and Applications》2003,279(1):339-349
Let be an orthogonal polynomial sequence on the real line with respect to a probability measure π with compact support S. For y∈S, a sequence of polynomials is called a selective approximate identity with respect to y if for all f∈C(S). We prove the existence and give a complete characterization of a selective approximate identity depending on . A Fejér-like construction is performed and is considered in the context of Nevai class M(b,a) and Nevai's G-operator. 相似文献
75.
Hugh Felkin Tauqir Fillebeen-Khan Yvonne Gault Rupert Holmes-Smith Janusz Zakrzewski 《Tetrahedron letters》1984,25(12):1279-1282
Homogeneous catalytic dehydrogenation of cycloöctane into cycloöctene has been effected by means of a variety of iridium and ruthenium polyhydrides, at 150°C, in the presence of an olefin as the hydrogen acceptor; best results (45–70 catalytic turnovers) have been achieved with (iPr3P)2IrH5, [(-F-C6H4)3P]2IrH5 and [(-F-C6H4)3P]3RuH4. 相似文献
76.
Messoud Efendiev Michael Kläre Rupert Lasser 《Mathematical Methods in the Applied Sciences》2007,30(5):579-594
We consider a chemotaxis‐growth model which takes into account diffusion, chemotaxis, production of chemical substance, and growth. We present estimates from above and below of the fractal dimension dim?? of the exponential attractor ?? in terms of the coefficients of the system. Comparisons are made between the sizes of the global and exponential attractors. Numerical simulations are presented which confirm the analytical results obtained. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
77.
The methods of preparation of ReO3F are revised. ReO3F is an amorphous yellow solid that crystallizes into colorless needles after prolonged heating. Its structure is that of a fluorine and oxygen bridged chain with hexa coordinated rhenium atoms (a = 670.9(2), b = 596.6(2), c = 1030.6(4) pm, β = 90.057(7)°, space group P2/c. In presence of donor solvents ReO3F·2L (L = (C2H5)2O, (CH3)2O, THF) are formed. ReO2F3, if crystallized from HF, exists in two crystalline forms, both are fluorine bridged chain polymers. (ReO2F3‐I: a = 1539.7(3), b = 999.6(3), c = 924.4(2) pm, β = 95.25(1)°, space group P21/c; ReO2F3‐II: a = 544.9(1), b = 494.2(1), c = 1253.7(2) pm, β = 98.543(7)°, space group P21/c. ReO2F3 crystallizes from CFCl3 or SO2FCl as fluorine bridged cyclic trimer (a = 881.4(4), c = 822.1(6) pm, γ = 120°, space group P63/m, or fluorine bridged cyclic tetramer (a = 1107.8(2), b = 999.4(2), c = 1347.9(3) pm, space group Cmca). 相似文献
78.
Bhargav Kumar Mitra Rupert Young Chris Chatwin 《Optics and Lasers in Engineering》2007,45(11):1088-1093
A popular approach for detecting moving object regions in video sequences is the application of the background subtraction technique. According to this technique the background (reference) image is subtracted from the current image frame and the moving parts are detected by the selection of a suitable threshold. In this paper we present our work to discriminate the moving pixels of the generated difference images from the relatively stationary pixels through the use of three different threshold selection strategies, namely, (i) ‘3σ edit rule’, (ii) rule utilizing the Hampel identifier, and (iii) rule based on an ad hoc selection of threshold. Further, after segmentation a method of classification, based on a moving shadow search technique, previously developed by the authors, has been applied to segregate the moving shadow region from the actual moving object. The speed-up achieved through the use of the three aforementioned techniques on the core moving shadow search process, compared to that where no such process has been applied, has been documented. The final outcomes of applying the shadow detection technique after segmenting using each of the threshold selection strategies, one at a time, on some indoor video sequences have been demonstrated and comparison of the methods made. 相似文献
79.
We examine a variety of polynomial-chaos-motivated approximations to a stochastic form of a steady state groundwater flow model. We consider approaches for truncating the infinite dimensional problem and producing decoupled systems. We discuss conditions under which such decoupling is possible and show that to generalize the known decoupling by numerical cubature, it would be necessary to find new multivariate cubature rules. Finally, we use the acceleration of Monte Carlo to compare the quality of polynomial models obtained for all approaches and find that in general the methods considered are more efficient than Monte Carlo for the relatively small domains considered in this work. A curse of dimensionality in the series expansion of the log-normal stochastic random field used to represent hydraulic conductivity provides a significant impediment to efficient approximations for large domains for all methods considered in this work, other than the Monte Carlo method. 相似文献
80.
Soren Solari Andrew Smith Rupert Minnett Robert Hecht-Nielsen 《Physics of life reviews》2008,5(2):106-120
Confabulation Theory [Hecht-Nielsen R. Confabulation theory. Springer-Verlag; 2007] is the first comprehensive theory of human and animal cognition. Here, we briefly describe Confabulation Theory and discuss experimental results that suggest the theory is correct. Simply put, Confabulation Theory proposes that thinking is like moving. In humans, the theory postulates that there are roughly 4000 thalamocortical modules, the “muscles of thought”. Each module performs an internal competition (confabulation) between its symbols, influenced by inputs delivered via learned axonal associations with symbols in other modules. In each module, this competition is controlled, as in an individual muscle, by a single graded (i.e., analog) thought control signal. The final result of this confabulation process is a single active symbol, the expression of which also results in launching of action commands that trigger and control subsequent movements and/or thought processes. Modules are manipulated in groups under coordinated, event-contingent control, in a similar manner to our 700 muscles. Confabulation Theory hypothesizes that the control of thinking is a direct evolutionary outgrowth of the control of movement. Establishing a complete understanding of Confabulation Theory will require launching and sustaining a massive new phalanx of confabulation neuroscience research. 相似文献