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排序方式: 共有179条查询结果,搜索用时 15 毫秒
21.
In this paper, we present a cubically convergent method for finding the largest eigenvalue of a nonnegative irreducible tensor. A cubically convergent method is used to solve an equivalent system of nonlinear equations which is transformed by the tensor eigenvalue problem. Due to particular structure of tensor, Chebyshev’s direction is added to the method with a few extra computation. Two rules are designed such that the descendant property of the search directions is ensured. The global convergence is proved by using the line search technique. Numerical results indicate that the proposed method is competitive and efficient on some test problems. 相似文献
22.
23.
M. Kolev S. Nawrocki B. Zubik-Kowal 《Communications in Nonlinear Science & Numerical Simulation》2013,18(6):1473-1480
We investigate a new mathematical model that describes lung cancer regression in patients treated by chemotherapy and radiotherapy. The model is composed of nonlinear integro-differential equations derived from the so-called kinetic theory for active particles and a new sink function is investigated according to clinical data from carcinoma planoepitheliale. The model equations are solved numerically and the data are utilized in order to find their unknown parameters. The results of the numerical experiments show a good correlation between the predicted and clinical data and illustrate that the mathematical model has potential to describe lung cancer regression. 相似文献
24.
Mikhail K. Kolev Miglena N. Koleva Lubin G. Vulkov 《Numerical Methods for Partial Differential Equations》2013,29(4):1121-1148
Two numerical methods for a one‐dimensional haptotaxis model, which exploit the use of van Leer flux limiter, are developed and analyzed. Sufficient conditions time step size and flux limiting are given for such formulation to ensure the non‐negativity of the discrete solution and second‐order accuracy in space. Another advantage is that we avoid solving large nonlinear systems of algebraic equations. The discrete preservation of total conservation of cell density, concentration, and logarithmic density is also verified for the numerical solution. Numerical results concerning accuracy, convergence rate, positivity, and conservation properties are presented and discussed. Similar approach could be applied efficiently in the corresponding two‐ and three‐dimensional problems. © 2012 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2013 相似文献
25.
Abstract The i.r. spectra of N-phenylphthalimide and 15N-phenylphthalimide have been measured in 4000–100 cm?1 frequency range as KBr and polyethylene pellets and as chloroform solutions. The Raman spectra (4000–50) cm?1 of microcrystalline powder of the of the same compounds have also been investigated. A detailed assignment of most of the observed frequencies has been proposed on the basis of the group vibrational concept, isotopic shift data and analogies with the spectra of related molecules. Some literature data have been discussed and some frequencies are reassigned. 相似文献
26.
Tsonko Kolev Bojidarka B. Koleva Michael Spiteller 《Central European Journal of Chemistry》2008,6(3):393-399
The applications of linear-polarized IR-spectroscopy to oriented colloid suspensions in a nematic host are demonstrated with
croconic and rhodizonic acids. The experimental IR vibrational assignments of the solid-state of both neutral compounds are
presented. Assignments are supported by theoretical quantum chemical calculations and vibrational analysis at the DFT level
of theoretical approximation with the 6-311++G** basis set.
相似文献
27.
Kolev T Koleva BB Stoyanov S Spiteller M Petkov I 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(5):1087-1096
Counterions affect on the substructures formation in the case of the merocyanine dye, 1-methyl-4-[2-(4-hydroxyphenyl)ethenyl)]piridinium] hydrogensquarate both in gas and condense phase. Spectroscopically and structural elucidation of these aggregates have been performed, using solid-state conventional and linear-polarized IR-spectroscopy of oriented colloids as a nematic liquid crystal suspension, UV-vis spectroscopy, HPLC tandem ESI mass spectrometry, (1)H and (13)C NMR, TGV and DSC. Quantum chemical DFT calculations have been carried out as well. Experimental and theoretical data are compared with analogous ones of corresponding iodide salt of dye studied. 相似文献
28.
B. B. Koleva R. D. Nikolova S. Zareva T. Kolev A. G. Bojilova H. Mayer-Figge W. S. Sheldrick 《Structural chemistry》2008,19(6):975-982
IR-spectroscopic characterization of the coumarin-3-phosphonic acid and 1,2-benzoxaphosphorine-3-carboxylic acid ethyl esters has been carried out by means of linear-polarized IR (IR-LD) spectroscopy of oriented colloid suspensions in a nematic host. Quantum chemical DFT calculations at the B3LYP level of theory and 6-311++G** basis set were performed. The electronic structure and vibrational properties of both compounds are discussed. The spectroscopic data for 2-benzoxaphosphorine-3-carboxylic acid ethyl ester are in accordance with the crystal structure determined by single crystal X-ray diffraction. The compound C13H15O5P crystallizes in the noncentrosymmetric space group P212121, and its structure consists of a 3D network formed by short contacts of the type P=O···HC(Ar) with distances of 3.420 and 2.467 Å. The geometry of the PO3C fragment exhibits a pseudo T d symmetry. 相似文献
29.
Crystal structure and spectroscopic properties of ammonium hydrogensquarate squaric acid monohydrate
Tsonko Kolev Rüdiger W. Seidel Bojidarka B. Koleva Michael Spiteller Heike Mayer-Figge William S. Sheldrick 《Structural chemistry》2008,19(1):101-107
The structure of ammonium hydrogensquarate squaric acid monohydrate has been determined by single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group C2/c and exhibits a 3D network with molecules linked by intermolecular interactions with participation of the H2Sq, HSq?, NH4 +, and H2O species. The HSq? anion and the neutral H2Sq form a strong head-to-tail dimer through O–H···O hydrogen bonding with lengths of 2.587 and 2.494 Å (protected space between numeral and unit). The layers are connected by ammonium cations and water molecules in a plane through the O···N (2.950, 2.978, 3.036 Å) and O···O (2.953, 2.781 Å) bonds. Another such layer is connected to the NH4 + cation in the adjacent plane through bifurcated N–H···O hydrogen-bonding to form a double layer (NH···O bond lengths are 3.036, 2.978, 2.857, 2.909, 2.958, and 2.742 Å, respectively). The IR-band assignment of the compound was achieved using the polarized IR-spectroscopy of oriented colloids in a nematic host. Theoretical ab initio calculations were performed and achieved with a view to explain the IR-bands of the H2Sq.HSq? motif. 相似文献
30.
Bojidarka B. Koleva Tsonko Kolev Marc Lamshöft Michael Spiteller 《Transition Metal Chemistry》2008,33(7):911-919
The coordination behaviour of the tripeptide glycyl-l-phenylalanyl-glycine (H-Gly-Phe-Gly-OH) with Au(III), Pd(II), and Pt(II) in both solution and in the solid state has been
investigated experimentally. In addition, quantum chemical calculations have been carried out with a view to obtain the structures
and spectroscopic properties of the ligand and its complexes. Both in solution and in the solid state the tripeptide interacts
in a tetradentate manner with the Au(III) and Pd(II) ions through the NH2, two deprotonated amide N atoms and the COO−group, forming [Au(H-Gly-Phe-Gly-OH)H−2)] × H2O and [Pd(H-Gly-l-Phe-Gly-OH)H−2)]Na × H2O complexes. The MN3O chromophores are calculated to be near planar. Interaction with cisplatin leads to the formation of a mononuclear complex
with tridentate coordination of the ligand by NH2 and two N- atoms from the deprotonated amide groups ([Pt(H-Gly-l-Phe-Gly-OH)H−2)NH3] × 2H2O). The fourth coordination position of the Pt(II) is occupied by an NH3 ligand. The PtN4 chromophore is flat with a deviation from planarity of 0.3°.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献