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121.
In anormalous dispersion of monomode optical fiber,optical solitons are evolvedfrom optical pulses when the dispersion is balanced by the nonlinearity.Undistorted transmissioncan be realized by using optical solitons,which can offer much greater the transmission capacityand extend the repeater spacing of the fiber communication system.The mechanism of thegeneration of optical solitons is expounded.A few forms of nonlinear transmission equationare obtained by using a concise method.The general complete expression of elementary solitonsolution of the nonlinear transmission equation without loss is given,and the design of the solitontransmission system is discussed. 相似文献
122.
The effect of Rasba spin–orbit interaction (SOI) on the magnetocapacitance of the 2DEG in a MODFET is investigated. We present calculations on the density of states (DOS) of the 2DEG in a MODFET under the influence of both Rasba SOI and weak two-dimensional periodic modulation. Adopting a Gaussian broadening of magnetic-field-dependent width, we present a simple expression for the DOS, valid for the relevant weak magnetic fields and modulation strengths. In the presence of Rasba SOI and for weak potential modulation strengths, a typical beating pattern of the magnetocapacitance oscillations is observed in the low magnetic filed range. A simple relation that predicts the positions of nodes in the beating patterns is obtained. The interplay between the SOI and the periodic potential modulation is discussed. 相似文献
123.
The ground state of the van der Waals-type lanthanide dimer Yb2 has been studied by means of relativistic energy-consistent ab initio pseudopotentials using three different core definitions.
Electron correlation was treated by coupled-cluster theory, whereby core-valence correlation effects have been accounted for
either explicitly by correlating the energetically highest coreorbitals or implicitly by means of an effective core-polarization
potential. Results for the first and second atomic ionization potentials, the atomic dipole polarizability, and the spectroscopic
constants of the molecular ground state are reported. Low-lying excited states have been investigated with spin-orbit configuration
interaction calculations. It is also demonstrated for the whole lanthanide series that correlation effects due to the atomic-like,
possibly open 4f-shell in lanthanides can be modeled effectively by adding a core-polarization potential to pseudopotentials attributing the
4f-shell to the core.
Received: 3 April 1998 / Accepted: 27 July 1998 / Published online: 9 October 1998 相似文献
124.
E. Sathiyaraj Samuele Ciattini 《Phosphorus, sulfur, and silicon and the related elements》2016,191(7):1042-1050
Twelve new nickel(II) complexes of functionalized dithiocarabamates [Ni(S2CNRR')2](1-6) and [Ni(S2CNRR')(NCS)(PPh3)](7-12) [where R=furfuryl; R'=2-hydroxy benzyl (1,7), 3-hydroxy benzyl (2,8), 4-hydroxy benzyl (3,9), 4-methoxy benzyl (4,10), 4-fluoro benzyl (5,11), 4-chloro benzyl (6,12)] have been prepared and characterized by elemental analysis, IR, UV-Vis and NMR (1H and 13C) spectroscopy. IR spectra of the complexes support the bidentate coordination of dithiocarbamate ligands. Electronic spectral studies on complexes 1-12 indicate square planar geometry around the nickel(II) central atom. In the 13C NMR spectra, the upfield shift of NCS2 carbon signal for heteroleptic complex (7-12) compared to homoleptic complexes (1-6) is due to the effect of PPh3 on the mesomeric drift of electron density toward nickel through thioureide C-N bond. Single crystal X-ray structural analysis of complex 11 confirms that the coordination geometry about the Ni(II) is distorted square planar. A rare intramolecular anagostic interaction C–H…Ni [Ni???H=2.804 Å] is observed. The packing of complex 11 is stabilized by non-conventional C–H…S, C–H?F and C–H?π(chelate, NiS2C) bonding interactions. 相似文献
125.
126.
V. E. Petrenko M. L. Dubova Yu. M. Kessler M. Yu. Perova 《Russian Chemical Bulletin》2000,49(11):1815-1819
A simple method for determination of the angular orientation of water molecules in the first coordination sphere from the
radial distribution functions is proposed. A comparative analysis of the ability of the model potentials of pair interaction
to take into account the effects of manybody interactions (MBI) was performed. The responses of the model pair potentials
to the MBI effects in the first and second coordination spheres were found to be poorly correlated with each other. It was
concluded that it is necessary to derive a new analytical type of potential functions of pair interaction.
Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 11, pp. 1842–1846. November. 2000. 相似文献
127.
Johannes Müller Janina Buck Prof. Dr. Andreas Hirsch 《European journal of organic chemistry》2023,26(9):e202201310
Within the scope of this paper, nine π-expanded mono-substituted 5,8,11,14,17-pentakis-(tert-butyl)-hexa-peri-hexabenzocoronenes (HBC) are introduced. 2-Iodo-5,8,11,14,17-pentakis-(tert-butyl)-hexa-peri-hexabenzocoronene served as precursor and was reacted with ethynyltrimethylsilane in a Sonogashira coupling reaction. The acetylene unit is used as a linker and can undergo another Sonogashira coupling reaction combining different phenyl coupling partners with the HBC core. The electron-withdrawing groups such as nitrile, pyridine and carbonyl species (aldehyde, methylester, carboxylic acid) as well as the three quinoxaline based species (diphenylquinoxaline, dibenzo[a,c]phenazine, phenanthro[4’,5’-a,b,c]phenazine) serve as substitution moieties. Their influence on the optoelectronic properties were investigated by UV/Vis absorption spectroscopy demonstrating a maximum redshift of 7 nm compared to starting compound 2-Iodo-5,8,11,14,17-pentakis-(tert-butyl) HBC. As for the phenanthro[4’,5’-a,b,c]phenazine substituted HBC a dramatic decrease in the intensity of the absorption of the UV/Vis spectrum was observed. The fluorescence spectroscopy pointed out that the dibenzo[a,c]phenazine and phenanthro[4’,5’-a,b,c]phenazine substitution changed the spectra to one broad peak departing from the characteristic HBC-like emission pattern. 相似文献
128.
Concetta De Stefano Claudia Foti Antonio Gianguzza Frank J. Millero Silvio Sammartano 《Journal of solution chemistry》1999,28(7):959-972
The hydrolysis of trimethyltin(IV) has been studied by potentiometry (H+ -glass electrode) and calorimetry in various salt media (NaNO3, NaCl, KCl, Na2SO4, and NaNO3—NaCl mixtures). The effect of ionic strength on the hydrolysis constants is accounted for by a simple Debye–Hückel type equation and by Pitzer equations. The results allow us to obtain H for hydrolysis and the temperature dependence of the Pitzer parameters. The resulting coefficients can be used to examine the speciation of (CH3)3Sn+ in multicomponent electrolyte solutions, such as natural waters, over a wide range of temperature and ionic strength. 相似文献
129.
W. Zielenkiewicz I. V. Terekhova A. Marcinowicz M. Koźbial J. Poznanski 《Journal of Thermal Analysis and Calorimetry》2008,93(2):365-372
Interactions of native and modified α- and β-cyclodextrins with nicotinic acid, pyridoxine and pyridoxal were studied by isothermal
titration calorimetry, solution calorimetry, and 1H NMR spectroscopy at 298.15 K and pH 6.8. Weak 1:1 complex formation was found only between α-cyclodextrin and nicotinic
acid. The stability constant and corresponding thermodynamic parameters of complex formation (Δc
G, Δc
H and Δc
S) were calculated using the calorimetric data. The 1H NMR data indicate the shallow insertion of the carboxylic group of the nicotinic acid molecule into α-CD cavity. For all
other compounds the weak interactions, not accompanied by complex formation, were characterized by the enthalpic virial coefficients
calculated on the basis of McMillan-Mayer approach. The obtained thermodynamic parameters were analyzed in the terms of influence
of the solutes’ structure on the selectivity of intermolecular host-guest interactions. 相似文献
130.
Indranath Mukhopadhyay 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1997,53(14):2467-2469
In this paper, it is shown that the interaction responsible for making the series of ‘forbidden' transitions from the state (nτK)=(110) in the ground vibrational (v=0) state to the levels of (122+) in the CH3-rocking vibrational state (v=r) of methanol is ‘Coriolis' resonance and not ‘Fermi' resonance as proposed in a recent publication. This has been established from the J-dependence of the observed perturbed energy spacings between the two interacting pairs from high resolution spectroscopic analysis. The J-dependence clearly follows the classic ‘Coriolis' interaction matrix elements for ΔK=2, which would not occur if the interaction were due to ‘Fermi' resonance. 相似文献