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61.
The excited states of a charged particle interacting with the quantized electromagnetic field and an external potential all
decay, but such a particle should have a true ground state – one that minimizes the energy and satisfies the Schr?dinger equation.
We prove quite generally that this state exists for all values of the fine-structure constant and the ultraviolet cutoff. We also show the same thing for a many-particle system under physically
natural conditions.
Oblatum 21-IX-2000 & 8-IV-2001?Published online: 18 June 2001 相似文献
62.
Marcel C. Remillieux Joseph M. Corcoran T. Ryan Haac Ricardo A. Burdisso U. Peter Svensson 《Applied Acoustics》2012,73(10):1029-1044
Propagation of impulsive sound around buildings and induced structural loading are investigated experimentally and numerically. Experiments were conducted on a rectangular building at Virginia Tech using sonic booms generated by shaped charges with an explosive weight of 0.78 kg, constructed from detonation cord. These experiments were simulated with a three-dimensional numerical model, in the context of geometrical acoustics (GA), by combining the image source method for the reflected field (specular reflections) with an extension of the Biot–Tolstoy–Medwin (BTM) method for the diffracted field. In this model, it is assumed that the acoustic propagation is linear and that all surfaces are acoustically rigid. This numerical model is validated against a boundary element (BE) solution and experimental data, showing a good overall agreement. The key advantages of this GA modeling approach for this application include the ability to model large three-dimensional domains over a wide frequency range and also to decompose the sound field into direct, reflected, and diffracted components, thus providing a better understanding of the sound-propagation mechanisms. Finally, this validated numerical model is used to investigate sound propagation around a cluster of six rectangular buildings, for a range of elevated source positions simulating sonic booms from aircraft. 相似文献
63.
B. Fraboni P. Cosseddu Y.Q. Wang R.K. Schulze A. Cavallini M. Nastasi A. Bonfiglio 《Physica B: Condensed Matter》2012,407(15):3047-3051
We report on the effects of low energy ion implantation (N and Ne) in the reduction and control of the degradation of pentacene organic thin film transistors (OTFTs) due to the exposure to atmosphere (i.e. oxygen and water). We have observed that a controlled damage depth distribution preserves the functionality of the devices, even if ion implantation induces significant molecular structure modifications, in particular a combination of dehydrogenation and carbonification effects. No relevant changes in the pentacene thin film thickness have been observed. The two major transport parameters that characterize OTFT performance are the carrier mobility and the threshold voltage. We have monitored the effectiveness of this process in stabilizing the device by monitoring the carrier mobility and the threshold voltage over a long time (over 2000 h). Finally, we have assessed by depth resolved X-ray Photoemission Spectroscopy analyses that, by selectively implanting with ions that can react with the hydrocarbon matrix (e.g. N+), it is possible to locally modify the charge distribution within the organic layer. 相似文献
64.
Marcel Herzog 《Journal of Combinatorial Theory, Series A》2008,115(7):1235-1245
Given integers k,l?2, where either l is odd or k is even, we denote by n=n(k,l) the largest integer such that each element of An is a product of k cycles of length l. For an odd l, k is the diameter of the undirected Cayley graph Cay(An,Cl), where Cl is the set of all l-cycles in An. We prove that if k?2 and l?9 is odd and divisible by 3, then . This extends earlier results by Bertram [E. Bertram, Even permutations as a product of two conjugate cycles, J. Combin. Theory 12 (1972) 368-380] and Bertram and Herzog [E. Bertram, M. Herzog, Powers of cycle-classes in symmetric groups, J. Combin. Theory Ser. A 94 (2001) 87-99]. 相似文献
65.
For a large class of quantum mechanical models of matter and radiation we develop an analytic perturbation theory for non-degenerate
ground states. This theory is applicable, for example, to models of matter with static nuclei and non-relativistic electrons
that are coupled to the UV-cutoff quantized radiation field in the dipole approximation. If the lowest point of the energy
spectrum is a non-degenerate eigenvalue of the Hamiltonian, we show that this eigenvalue is an analytic function of the nuclear
coordinates and of α3/2, α being the fine structure constant. A suitably chosen ground state vector depends analytically on α3/2 and it is twice continuously differentiable with respect to the nuclear coordinates.
Submitted: November 24, 2008. Accepted: March 4, 2009. 相似文献
66.
Marcelín-Jiménez G Morales-Martínez M Angeles-Moreno AP Mendoza-Morales L 《Biomedical chromatography : BMC》2008,22(10):1143-1148
Pharmacokinetics of diphenidol (DPN) is limited due to the lack of analytical methodology. Here, a micro-assay for DPN quantification was developed, by coupling ultra-performance liquid chromatography with tandem mass spectrometry. The procedure involved plasma precipitation and injection of supernatant into UPLC with an Acquitytrade mark C18 column. Detection was in positive electrospray, following transitions of m/z 310.3 --> 292.3 and m/z 275.3 --> 230.2 for DPN and chlorphenamine (internal standard), respectively. The method was linear with a range of 4-400 ng/mL, and a 2 min run time. This method was applied in a switchability trial, where both formulations of DPN were bioequivalent. 相似文献
67.
A reaction of trans-[Ir(H)(5)(PiPr(3))(2)] (1) with 2,3,5,6-tetrafluoropyridine, pentafluorobenzene or 1,3-difluorobenzene in the presence of neohexene affords the square-pyramidal C-H activation products cis-trans-[Ir(4-C(5)NF(4))(H)(2)(PiPr(3))(2)] (2), cis-trans-[Ir(C(6)F(5))(H)(2)(PiPr(3))(2)] (4) and cis-trans-[Ir(2-C(6)H(3)F(2))(H)(2)(PiPr(3))(2)] (6). Irradiation of complex 1 with 2,3,5,6-tetrafluoropyridine or pentafluorobenzene gave the hydrides cis-trans-[Ir(4-C(5)NF(4))(H)(2)(H(2))(PiPr(3))(2)] (3) or cis-trans-[Ir(C(6)F(5))(H)(2)(H(2))(PiPr(3))(2)] (5). The presence of non-classical bound H(2) moieties has been demonstrated by the measurement of T(1) times at different temperatures. For 3 the H-H distance in the H(2) ligand can be estimated to be 0.82 A. The dihydride compounds 2, 4 and 6 react with CO to yield the complexes cis-trans-[Ir(Ar)(H)(2)(CO)(PiPr(3))(2)] (7: Ar = 4-C(5)NF(4), 8: Ar = C(6)F(5), 9: Ar = 2-C(6)H(3)F(2)). A reaction of 2 or 3 with an excess of ethylene leads to the formation of ethane and the Ir(i) ethylene complex trans-[Ir(4-C(5)NF(4))(eta(2)-C(2)H(4))(PiPr(3))(2)] (10). Treatment of 10 with CO furnishes the Ir(i) complex trans-[Ir(4-C(5)NF(4))(CO)(PiPr(3))(2)] (11). 相似文献
68.
Moreira LM Santiago PS de Almeida EV Tabak M 《Colloids and surfaces. B, Biointerfaces》2008,61(2):153-163
The present work focuses on the interaction between the zwitterionic surfactant N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) and the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp). Electronic optical absorption, fluorescence emission and circular dichroism spectroscopy techniques, together with Gel-filtration chromatography, were used in order to evaluate the oligomeric dissociation as well as the autoxidation of HbGp as a function of the interaction with HPS. A peculiar behavior was observed for the HPS–HbGp interaction: a complex ferric species formation equilibrium was promoted, as a consequence of the autoxidation and oligomeric dissociation processes. At pH 7.0, HPS is more effective up to 1 mM while at pH 9.0 the surfactant effect is more intense above 1 mM. Furthermore, the interaction of HPS with HbGp was clearly less intense than the interaction of this hemoglobin with cationic (CTAC) and anionic (SDS) surfactants. Probably, this lower interaction with HPS is due to two factors: (i) the lower electrostatic attraction between the HPS surfactant and the protein surface ionic sites when compared to the electrostatic interaction between HbGp and cationic and anionic surfactants, and (ii) the low cmc of HPS, which probably reduces the interaction of the surfactant in the monomeric form with the protein. The present work emphasizes the importance of the electrostatic contribution in the interaction between ionic surfactants and HbGp. Furthermore, in the whole HPS concentration range used in this study, no folding and autoxidation decrease induced by this surfactant were observed. This is quite different from the literature data on the interaction between surfactants and tetrameric hemoglobins, that supports the occurrence of this behavior for the intracellular hemoglobins at low surfactant concentration range. Spectroscopic data are discussed and compared with the literature in order to improve the understanding of hemoglobin–surfactant interaction as well as the acid isoelectric point (pI) influence of the giant extracellular hemoglobins on their structure–activity relationship. 相似文献
69.
Antipina MN Schulze I Dobner B Langner A Brezesinski G 《Langmuir : the ACS journal of surfaces and colloids》2007,23(7):3919-3926
Cationic liposomes/DNA complexes can be used as nonviral vectors for direct delivery of DNA-based biopharmaceuticals to damaged cells and tissues. In order to obtain more effective and safer liposome-based gene transfection systems, the new cationic lipid 2-amino-3-hexadecyloxy-2-(hexadecyloxymethyl)propan-1-ol (AHHP) was synthesized. In this paper we report on the synthesis of AHHP and investigations of its physical-chemical properties. Langmuir monolayers of AHHP were studied at the air/buffer interface by film balance measurements, grazing incidence X-ray diffraction (GIXD), and infrared reflection absorption spectroscopy (IRRAS). Structure and thermotropic phase behavior of AHHP in aqueous dispersion were examined by small-angle and wide-angle X-ray scattering (SAXS/WAXS) and differential scanning calorimetry (DSC). The results show clear differences in structure and phase behavior of AHHP, both in the monolayer system and in aqueous dispersions, in dependence on the subphase pH due to protonation or deprotonation of the primary amine in the lipid head group. Thermodynamic data derived from pi-A isotherms provide information about the critical temperature (Tc), which is in rough agreement with the temperature of the lipid phase transition from gel to fluid state (Tm) found by X-ray and calorimetry studies of AHHP aqueous dispersions. The packing properties of the molecules in mono- and bilayer systems are very similar. DNA couples to the monolayer of the new lipid at low as well as at high pH but in different amounts. The DNA coupling leads to an alignment of adsorbed DNA strands indicated by the appearance of a Bragg peak. The distance between aligned DNA strands does not change much with increasing monolayer pressure. 相似文献
70.
Marcel Meiland 《Tetrahedron letters》2009,50(4):469-3893
MS and 1H, 13C and 11B NMR results are presented revealing the formation of cyclic seven-membered boronate structures at trans-1,2-diol moieties of carbohydrates providing new opportunities for the activation, protection and analysis of glucopyranose-based oligomers and polymers such as cellulose or starch. ‘Coordination-induced shifts’ in 13C NMR spectra were identified for the esterification by boronic acids of carbohydrates, which can be applied for further studies. 相似文献