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971.
In the paper (Khugaev et al. in Phys Rev D94:064065. arXiv: 1603.07118, 2016), we have shown that for perfect fluid spheres the pressure isotropy equation for Buchdahl–Vaidya–Tikekar metric ansatz continues to have the same Gauss form in higher dimensions, and hence higher dimensional solutions could be obtained by redefining the space geometry characterizing Vaidya–Tikekar parameter K. In this paper we extend this analysis to pure Lovelock gravity; i.e. a \((2N+2)\)-dimensional solution with a given \(K_{2N+2}\) can be taken over to higher n-dimensional pure Lovelock solution with \(K_n=(K_{2N+2}-n+2N+2)/(n-2N-1)\) where N is degree of Lovelock action. This ansatz includes the uniform density Schwarzshild and the Finch–Skea models, and it is interesting that the two define the two ends of compactness, the former being the densest and while the latter rarest. All other models with this ansatz lie in between these two limiting distributions. 相似文献
972.
F. Duque L.M. Molina M.J. López A. Ma nanes J.A. Alonso 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):285-288
The electronic and atomic structure of Al13H has been studied using Density Functional Theory. Al13H has closed electronic shells. This makes the cluster very stable and suggests that it could be a candidate to form cluster
assembled solids. The interaction between two Al13H clusters was analyzed and we found that the two units preserve their identities in the dimer. A cubic-like solid phase assembled
from Al13H units was then modeled. In that solid the clusters retain much of their identity. Molecular dynamics runs show that the
structure of the assembled solid is stable at least up to 150 K. A favorable relative orientation of the clusters with respect
to their neighbors is critical for the stability of that solid.
Received 21 November 2000 相似文献
973.
Iris Miraballes‐Martínez A. Martín‐Molina F. Galisteo‐Gonzlez Jacqueline Forcada 《Journal of polymer science. Part A, Polymer chemistry》2001,39(17):2929-2936
Cationic latex particles with surface amino groups were prepared by a multistep batch emulsion polymerization. In the first one or two steps, monodisperse cationic latex particles to be used as the seed were synthesized, and in the third step, two different amino‐functionalized monomers [aminoethylmethacrylate hydrochloride (AEMH) and vinylbenzylamine hydrochloride (VBAH)] were used to synthesize the final functionalized latex particles. 2,2′‐Azobisisobutyramidine dihydrochloride was used as the initiator, and different concentrations of two quaternary ammonium emulsifiers with hydrophobic chains of different lengths were examined. To characterize the final latexes yields were obtained gravimetrically, and particle size distributions and average particle diameters were determined by transmission electron microscopy and photon correlation spectroscopy. The amount of amino groups was determined by fluorimetry. The effect of the amino‐functional monomer used on the final latexes and the colloidal behavior of the system were studied. The influence of the different conditions utilized to synthesize the latexes on the colloidal stability of the particles was evaluated in terms of the Fuchs stability ratio and electrophoretic mobility. High yields of the amino‐functional monomers were obtained. Surface amino, amidine, and quaternary ammonium groups provided the cationic character. The colloidal stability behavior of the products obtained was compatible with their cationic character. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2929–2936, 2001 相似文献
974.
975.
Hans De Brouwer Mike A. J. Schellekens Bert Klumperman Michael J. Monteiro Anton L. German 《Journal of polymer science. Part A, Polymer chemistry》2000,38(19):3596-3603
Reversible addition–fragmentation chain transfer (RAFT) was applied to the copolymerization of styrene and maleic anhydride. The product had a low polydispersity and a predetermined molar mass. Novel, well‐defined polyolefin‐based block copolymers were prepared with a macromolecular RAFT agent prepared from a commercially available polyolefin (Kraton L‐1203). The second block consisted of either polystyrene or poly(styrene‐co‐maleic anhydride). Furthermore, the colored, labile dithioester moiety in the product of the RAFT polymerizations could be removed from the polymer chain by UV irradiation. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3596–3603, 2000 相似文献
976.
Anna Puig‐Molina Harald Müller Anne‐Marie Le Qur Gavin Vaughan Heinz Graafsma ke Kvick 《无机化学与普通化学杂志》2000,626(11):2379-2387
Disodium[hydroxotetranitronitrosyl]ruthenate(II) is a photochromic compound excitable with blue‐green light which exhibits at least one unusually long‐lived metastable state at low temperature. At 298 K, the compound crystallises in the space group C2/m. A reversible phase transition occurs at 240 K upon cooling, as detected by Differential Scanning Calorimetry and X‐ray powder diffraction which causes a lowering of the crystal symmetry to the space group P21/n. Synchrotron X‐ray single crystal diffraction and FT‐IR spectroscopy data obtained on the ground and the excited states of the title compound low temperature phase are presented. 相似文献
977.
We introduce a deflation method that takes advantage of the IRA method, by extracting a GMRES solution from the Krylov basis
computed within the Arnoldi process of the IRA method itself. The deflation is well-suited because it is done with eigenvectors
associated to the eigenvalues that are closest to zero, which are approximated by IRA very quickly. By a slight modification,
we adapt it to the FOM algorithm, and then to GMRES enhanced by imposing constraints within the minimization condition. The
use of IRA enables us to reduce the number of matrix-vector products, while keeping a low storage.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
978.
M. J. Ayora Ca?ada M. I. Pascual Reguera A. Molina Díaz 《Fresenius' Journal of Analytical Chemistry》1999,363(1):59-63
An integrated flow-through photometric sensor for the determination of nickel in real samples of various origins has been
developed. The sensor is based on the reaction of Ni(II) with 1-(2-pyridylazo)-2-naphthol (PAN) immobilized on a cationic
resin which was placed in a flow-cell using a spectrophotometer tuned at 566 nm as detector. The Ni(II) ion from the sample
injected into the carrrier stream (pH = 5.0) of a monochannel continuous flow system reacts with the immobilized chromogenic
reagent to form a red chelate which remains on the active solid support and generates the analytical signal. When this reached
its maximum value the Ni(II)-PAN chelate was destroyed using 1 M H2SO4 as eluents, leaving the sorbed PAN untouched. The response of the sensor was linear in the three concentration ranges assayed:
0.3–4.0, 0.1–1.6 and 0.05–0.8 μg mL–1 for sample volumes of 100, 400 and 800 μL, respectively, and the R.S.D.(%) (n = 10) were 1.80(100 μL), 3.04(400 μL) and 2.29(800
μL). The sensor showed an excellent selectivity which could also be increased with a simple on-line modification to avoid
interference from copper. It was applied to a variety of real samples with very good results in all cases.
Received: 15 April 1998 / Revised: 29 June 1998 / Accepted: 3 July 1998 相似文献
979.
L. M. Plyasova T. M. Yur’eva I. Yu. Molina T. A. Kriger A. M. Balagurov L. P. Davydova V. I. Zaikovskii G. N. Kustova V. V. Malakhov L. S. Dovlitova 《Kinetics and Catalysis》2000,41(3):429-436
The dynamics of structural transformations during copper aluminate reduction in the temperature range used for catalyst activation
was studied by high-temperature X-ray analysis under controlled conditions (hydrogen, 2O–4OO‡C). The techniques of neutron
diffraction analysis, IR spectroscopy, chemical phase analysis, and electron microscopy were also used at particular stages.
In the course of reduction, copper metal is deposited onto the surface of spinel crystals from the bulk. Spinel becomes cation-deficient
with respect to copper. An analysis of powder diffraction patterns demonstrated that copper is reduced and released from tetrahedral
positions of the spinel structure at temperatures below ~300‡C and from octahedral positions only at temperatures above 300‡C.
In this case, a redistribution of aluminum ions was observed simultaneously. It is likely that the electrical neutrality is
attained by the formation of OH groups, the appearance of which in reduced samples was detected by IR spectroscopy and confirmed
by neutron diffraction analysis. At a reduction temperature of 400‡C, the oxygen framework was partially disintegrated. The
structures of reduced copper aluminates and chromites were compared. 相似文献
980.