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161.
In this paper we show that, if G is a Berge graph such that neither G nor its complement
contains certain induced subgraphs, named proper wheels and long prisms, then either G is a basic perfect graph( a bipartite graph, a line graph of a bipartite graph or the complement of such graphs) or it has
a skew partition that cannot occur in a minimally imperfect graph. This structural result implies that G is perfect.
This work was supported in part by NSF grant DMI-0352885 and ONR grant N00014-03-1-0188. 相似文献
162.
Giacomo Nannicini Philippe Baptiste Gilles Barbier Daniel Krob Leo Liberti 《Computational Optimization and Applications》2010,45(1):143-158
Efficiently computing fast paths in large-scale dynamic road networks (where dynamic traffic information is known over a part
of the network) is a practical problem faced by traffic information service providers who wish to offer a realistic fast path
computation to GPS terminal enabled vehicles. The heuristic solution method we propose is based on a highway hierarchy-based
shortest path algorithm for static large-scale networks; we maintain a static highway hierarchy and perform each query on
the dynamically evaluated network, using a simple algorithm to propagate available dynamic traffic information over a larger
part of the road network. We provide computational results that show the efficacy of our approach. 相似文献
163.
Giacomo Luigi Petretto Sergio Stoccoro Maria Agostina Cinellu Giovanni Minghetti 《Journal of organometallic chemistry》2010,695(2):256-259
Taking advantage of palladium peculiar “rollover” C,N cyclometallation, it is possible to promote C(3) functionalization of 6-alkyl-substituted-2,2′-bipyridines. The carbonylation reaction of rollover species [Pd(Ln)Cl]2, (HL1 = 6-isopropyl-2,2′-bipy, 1; HL2 = 6-neopentyl-2,2′-bipy, 2; HL3 = 6-ethyl-2,2′-bipy, 3; HL4 = 6-methyl-2,2′-bipy, 4) allowed the synthesis of 2-(pyridin-2-yl)-6-alkyl-nicotinic acids or esters. These nicotinic derivatives are extremely rare and, as far as we know, quite unreported in the case of the 6-substituted molecules. 相似文献
164.
In this work, a combination of experimental and quantum mechanical investigations is performed for the study of dichroic absorption properties of melt-processed linear low-density polyethylene (LLDPE) oriented films containing < or =0.5 wt % of either 4,4'-bis(2-benzoxazolyl)stilbene (BBS) or 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene (BTBBT). The data acquired reveal that the film optical anisotropy and the performances as linear polarizer are strongly dependent on the molecular structure of the chromophore. In particular, the rodlike structure of BBS favors the alignment of the dye along the drawing direction of the PE film, providing dichroic ratios as high as 100 and optical performances as linear polarizer close to the pseudo-affine deformation scheme. On the contrary BTBBT, although characterized by huge anisotropic potentialities, confers the oriented film very poor dichroism and is unsuitable for linear polarizer applications. This behavior is attributed to the more complex banana-shaped structure of BTBBT dye caused by the thiophene 2,5-functionalization that limits the molecule parallel orientation to the drawing direction. 相似文献
165.
A. De Giacomo P. D'Angelo A. Inglese S. Milioto R. De Lisi 《Journal of solution chemistry》1999,28(8):1001-1018
Density measurements on decyltrimethylammonium bromide (DeTAB)–water and pentanol (PentOH)–DeTAB–water systems as functions of both alcohol and surfactant m
S concentrations were carried out at 2 and 19 MPa from 25 to 130°C. From experimental data for the water–DeTAB binary system, the standard (infinite dilution) partial molar volumes, expansibilities, and compressibilities of DeTAB, and the corresponding properties in the micellar phase are calculated. The trends of the standard partial molar volumes of PentOH V
R
o
in DeTAB micellar solutions as functions of m
S reflect the transfer of PentOH from the aqueous to the micellar phase, except at 130°C and 19 MPa. On the basis of an equation previously used, the distribution constant of PentOH between the aqueous and the micellar phases and the standard partial molar volume of alcohol in the aqueous and the micellar phases are obtained from V
R
o
data. Comparisons with data for PentOH in dodecyltrimethylammonium bromide are made. 相似文献
166.
Giacomo Nannicini 《4OR: A Quarterly Journal of Operations Research》2010,8(3):327-330
This a summary of the author’s PhD thesis supervised by Leo Liberti, Philippe Baptiste and Daniel Krob and defended on 18
June 2009 at Ecole Polytechnique, Palaiseau, France. The thesis is written in English and is available at . The computation of point-to-point shortest paths in road networks has many practical applications that require very fast
solution times, meaning that Dijkstra’s algorithm is not a viable option. In this work we develop an efficient algorithm to
find the shortest route between two nodes of a large-scale, time-dependent graph, where we also allow the time-dependent arc
cost functions to be updated at regular intervals. Furthermore, we propose a mathematical programming formulation for the
shortest paths problem on time-dependent networks, that gives rise to integer programs. Within the context of solving Mixed-Integer
Linear Programs through a Branch-and-Bound algorithm, we propose a new strategy for branching, mixing branching on single
variables with branching on general hyperplanes. Finally, we introduce an effective heuristic for nonconvex Mixed-Integer
Nonlinear Programss which combines VNS, Local Branching, NLP local search and Branch-and-Bound. 相似文献
167.
Magnetic degrees of freedom are manifested through violations of the Bianchi identities and associated with singular fields.
Moreover, these singularities should not induce color nonconservation. We argue that the resolution of the constraint is that
the singular fields, or defects are Abelian in nature. Recently proposed surface operators seem to represent a general solution
to this constraint and can serve as a prototype of magnetic degrees of freedom. Some basic lattice observations, such as the
Abelian dominance of the confining fields, are explained then as consequences of the original non-Abelian invariance. Generically,
the properties of the two-dimensional defects associated with the surface operators are close to the predictions of the dual
models for the magnetic D2 branes. 相似文献
168.
169.
The carrier properties of mixed unilamellar vesicles of fluorocarbon-hydrocarbon surfactants built up with the ammonium salt of a perfluoropolyether and n-dodecylbetaine were investigated by electron spin resonance spectroscopy (ESR). The ESR-active lipophilic nitroxide 5-doxylstearic acid (5-DSA) was used as a model of a lipophilic drug to be carried and delivered into cell membranes. Healthy and malignant colorectal tissues were used as the target cells. Cell suspensions of living tissues were studied in physiological conditions. For the maintenance of the surgically removed tissues, McCoy’s 5A culture medium was used. 5-DSA probe was rapidly delivered from perfluoropolyether (PFPE)/betaine mixed vesicles to the membranes of both healthy and malignant colorectal cells. The analysis of the computed 5-DSA ESR line shapes ensured that no spectral differences occurred when 5-DSA was either introduced directly into the cells or through the intervention of vesicles. This well agreed for an unmodified physical status of the membranes where the probe was mainly localized. 相似文献
170.
Marino Basato Giacomo Facchin Mirto Mozzon Paolo Sgarbossa Augusto Tassan 《Journal of organometallic chemistry》2004,689(2):454-462
2-(Azidomethyl)phenyl isocyanide, 2-(CH2N3)C6H4NC (AziNC), coordinates to some cationic Pt(II) and Pd(II) species to afford isocyanide complexes of the type trans-[MCl(AziNC)(PPh3)2][BF4] (M=Pt, l; Pd, 2). AziNC is coordinated also in some neutral Pt(II) and Pd(II) species such as [MCl2(AziNC)2] (M=Pt, 3; Pd, 4) derived from the reactions of 2 equiv. of AziNC with [PtCl2(COD)] and [PdCl2(MeCN)2], respectively. Complexes 1 and 2 react with 1 equiv. of PPh3 affording the heterocyclic carbene complexes trans-[MCl{(H)}(PPh3)2][BF4] (M=Pt, 5; Pd, 6). Complexes 3 and 4 react with 1 equiv. of PPh3 displacing the isocyanide with the formation of the complexes cis-[MCl2(AziNC)(PPh3)] (M=Pt, 7; Pd, 8). These latter ones react with 2 equiv. of PPh3 affording as the final products the cationic carbene species trans-[MCl{(H)}(PPh3)2][Cl] (M=Pt, 9; Pd, 10). Complex 5 was also characterized by single crystal X-ray diffraction. The carbene complex is square-planar and the angle formed between the platinum square plane and the heterocyclic carbene ligand is 87.9(2)°. The C(1)-N(1) and C(1)-N(2) bond distances in the latter of 1.32(2) and 1.30(2) Å, respectively, are short for a single bond and indicate extensive π-bonding between the nitrogen atoms and the carbene carbon. 相似文献