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131.
M. Gutowski I. Dabkowska J. Rak S. Xu J.M. Nilles D. Radisic K.H. Bowen Jr 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):431-439
The photoelectron spectra (PES) of anions of uracil-glycine and uracil-phenylalanine complexes reveal broad features with
maxima at 1.8 and 2.0 eV. The results of ab initio density functional B3LYP and second order M?ller-Plesset theory calculations indicate that the excess electron occupies a
π* orbital localized on uracil. The excess electron attachment to the complex can induce a barrier-free proton transfer (BFPT)
from the carboxylic group of glycine to the O8 atom of uracil. As a result, the four most stable structures of the anion of
uracil-glycine complex can be characterized as the neutral radical of hydrogenated uracil solvated by the anion of deprotonated
glycine. The similarity between the PES spectra for the uracil complexes with glycine and phenylalanine suggests that the
BFPT is also operative in the case of the latter anionic species. The BFPT to the O8 atom of uracil may be related to the
damage of nucleic acid bases by low energy electrons because the O8 atom is involved in a hydrogen bond with adenine in the
standard Watson-Crick pairing scheme.
Received 6 April 2002 Published online 13 September 2002 相似文献
132.
We study the propagation of the light mesons σ,ω,ρ, and a0(980) in dense hadronic matter in an extended derivative scalar coupling model. Within the scheme proposed it is possible
to unambiguously define effective density-dependent couplings at the Lagrangian level. We first apply the model to study asymmetric
nuclear matter with fixed isospin asymmetry, and then we pay particular attention to hypermatter in β-equilibrium. The equation
of state and the potential contribution to the symmetry coefficient arising from the mean-field approximation are investigated.
Received: 16 October 2001 / Accepted: 10 January 2002 相似文献
133.
N.-K. Lee T.A. Vilgis 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(4):451-465
We study the elastic properties of single A/B random copolymer chains, with a specific sequence and use them as theoretical
model for so called HP proteins. HP proteins carry hydrophilic (P) and hydrophobic (H) monomers. We predict a rich structure
in the force-extension relations which can be attributed to the information in the sequence. The variational method is used
to probe local minima on the path of stretching and releasing for the chain molecules. At a given force, we find multiple
configurations which are separated by energy barriers. A collapsed globular configuration consists of several domains which
unravel cooperatively. Upon stretching, the unfolding path shows a stepwise pattern corresponding to the unfolding of each
domain. While releasing, several cores can be created simultaneously in the middle of the chain, resulting in a different
path of collapse. The long-range interactions and stiffness of the chain simplify the potential landscape given by the disorder
in sequence.
Received 5 March 2002 / Received in final form 16 May 2002 Published online 13 August 2002 相似文献
134.
Ying Zhang Gang Hu Shigang Chen H.A. Cerdeira 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):381-384
A method of controlling global stochasticity in Hamiltonian systems by applying nonlinear perturbation is proposed. With the
well-known standard map we demonstrate that this control method can convert global stochasticity into regular motion in a
wide chaotic region for arbitrary initial condition, in which the control signal remains very weak after a few kicks. The
system in which chaos has been controlled approximates to the original Hamiltonian system, and this approach appears robust
against small external noise. The mechanism underlying this high control efficiency is intuitively explained.
Received 15 January 2002 Published online 6 June 2002 相似文献
135.
S. Zschocke G. Plunien G. Soff 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):147-156
The renormalization method of Bogoljubov-Parasiuk-Hepp-Zimmermann (BPHZ) is used in order to derive the renormalized energy
shift due to the gauge invariant K?llén-Sabry diagram of the two-photon vacuum polarization (VPVP) as well as the self energy
vacuum polarization S(VP)E beyond the Uehling approximation. It is outlined, that no outer renormalization is required for
the two-photon vacuum polarization and that only the inner renormalization has to be accomplished. It is shown that the so-called
nongauge invariant spurious term is absent for a wide class of vacuum polarization (VP) diagrams if one applies the widely
used spherical expansion of bound and free-electron propagator. This simplifies significantly calculations in bound state
quantum electrodynamics. As one result of our paper the use of the BPHZ-approach in bound state QED is established.
Received 28 September 2001 相似文献
136.
137.
Myung-Soon Lee 《Applied Surface Science》2006,252(14):5019-5025
We prepared high quality Au(1 1 1) film on Si wafer through the spin coating and thermal decomposition of a gold ink, spin-coated-and-fired (SCAF) Au film. The X-ray measurements, XRD and pole-figure analysis, showed that the SCAF Au film has a (1 1 1) out-of-plane orientation with a random in-plane orientation. In order to confirm the chemical activity of the SCAF Au film, we demonstrate the formation of patterned structures with the film by using soft lithography technique. The chemical activities of this physically stable SCAF Au film to the alkanethiols were at least equivalent those of physically deposited the Au films. The possibility of the mass production of micro patterned structure with the SCAF Au film was also demonstrated over the wide region on Si wafer by the microcontact lithography. These suggest that the Au film will help the easy fabrication of various nanosized devices on Si wafer and other substrates. 相似文献
138.
The pulsed positron beam at the Helsinki University of Technology is designed for the end energy of 3-30 keV and grounded target. This is achieved with a constant voltage acceleration followed by an adjustable deceleration. In the design of this accelerator-decelerator the possibility for electrical breakdowns and partial discharges must be eliminated.For designing the electrode and insulator structures for accelerator-decelerator configuration electric field simulations were carried out with the finite element analysis program. In this paper we present the design of the accelerator-decelerator and the results of the electric field simulations. The results of high voltage tests will also be presented and compared with the simulations. 相似文献
139.
In this paper, we report that the phase transformation of Ni-B, Ni-P diffusion barriers deposited electrolessly on Cu, for the reason that the Ni-P layer is a more effective diffusion barrier than the Ni-B layer. The Ni3B crystallized was decomposed to Ni and B2O3 above 400 °C and the Ni3P crystallized was decomposed to Ni and P2O5 above 600 °C respectively in Ar atmosphere. Also, the Ni3B was decomposed to Ni and free B above 400 °C and the Ni3P was decomposed to Ni and free P above 600 °C respectively in H2 atmosphere. The decomposed Ni formed a solid solution with Cu. The Cu diffusion occurred above 400 °C for Ni-B layer and above 600 °C for Ni-P layer, respectively. Because the decomposition temperature of Ni-P layer is about 200 °C higher than that of Ni-B layer, the Ni-P layer is a more effective barrier for Cu than the Ni-B layer. 相似文献
140.
着生刚毛藻处理富营养化湖泊水 总被引:8,自引:0,他引:8
分别研究了室内和露天条件下在鹅卵石上着生的刚毛藻Cladophora oligoclona对富营养化湖水中氮(N)和磷(P)的净化效果及其对水华藻类生长的抑制能力,同时对处理后湖水的藻类生长潜力进行了测试.结果显示,刚毛藻在原始浓度总氮(TN)10.512 mg/L和总磷(TP)0.856 mg/L的富营养化湖水中能维持正常的生长代谢,并能有效去除水体中的N、P养分.在室内12 d培养期间,刚毛藻对TN、氨氮(NH4-N)、TP和无机磷(PO4-P)的平均去除率分别达53.13%,44.40%,35.71%和30.53%.在室外6 d培养期间,刚毛藻对TN、NH4-N、TP和PO4-P的日均减少量分别为1.643 5±0.413 9,1.350 3±0.352 4,0.113 7±0.041 1,0.074 2±0.033 0 mg/L,总去除率分别高达93.81%,94.62%,79.67%和77.66%.刚毛藻对水华微囊藻生长的抑制率达99.63%,处理后湖水的藻类生长潜力较原湖水下降了40.17%.据此认为,刚毛藻在净化污染水体、修复受损湖泊及防治水体富营养化等方面具有潜在的应用前景. 相似文献