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101.
The research described in this paper presents a method for chemically modifying the surface of plant photosynthetic membranes
in such a way that electrical contact can be made. Colloidal platinum was prepared, precipitated directly onto thylakoid membranes
from aqueous solution, and entrapped on fiberglass filter paper. This composition of matter was capable of sustained simultaneous
photoevolution of hydrogen and oxygen when irradiated at any wavelength (400–700 nm) in the chlorophyll absorption spectrum.
Experimental data support the interpretation that part of the platinum metal catalyst is precipitated adjacent to the photosystem-I
reduction site of photosynthesis and that electron transfer occurs across the interface between photosystem I and the catalyst.
When contacted with metal electrodes, the thylakoid-platinum combination was capable of generating a sustained flow of current
through an external load resistor. Procedures for preparing this material and experimental data on its catalytic and electronic
properties are presented. Also presented is an analysis of the flow of photocurrent in terms of the interfacial electron transfer
reactions that occur at the interfaces of the components of the assembly. 相似文献
102.
Multi-temperature thermal plasmas have often to be considered to account for the nonequilibrium effects. Recently André et al. have developed the calculation of concentrations in a multi-temperature plasma by artificially separating the partition functions into a product by assuming that the excitation energies are those of the lower levels (electronic, vibration, and rotation). However, at equilibrium, differences, increasing with temperature, can be observed between partition functions calculated rigorously and with their method. This paper presents a modified method where it has been assumed that the preponderant rotational energy is that of the vibrational level v=0 of the ground electronic state and the preponderant vibrational energy is that of the ground electronic state. The internal partition function can then be expressed as a product of series expressions. At equilibrium for N
2
and N
2
+
partition functions the values calculated with our method differ by less than 0.1% from those calculated rigorously. The calculation has been limited to three temperatures: heavy species Th
, electrons Te
, and vibrational T
v
temperatures. The plasma composition has been calculated by minimizing the Gibbs free enthalpy with the steepest descent numerical technique. The nonequilibrium properties have been calculated using the method of Devoto, modified by Bonnefoi and Aubreton. The ratio =Te/Th
was varied between 1 and 2 as well as the ratio
v
=T
v
/T
h
for a nitrogen plasma. At equilibrium the corresponding equilibrium transport properties of Ar and N
2
are in good agreement with those of Devoto and Murphy except for T>10,000 K where we used a different interaction potential for N–N
+
. The effects of v
and e
on thermodynamic and transport properties of N
2
are then discussed. 相似文献
103.
Rat V. André P. Aubreton J. Elchinger M.F. Fauchais P. Lefort A. 《Plasma Chemistry and Plasma Processing》2002,22(4):453-474
The calculation of two-temperature transport coefficients in an argon–hydrogen plasma at atmospheric pressure is performed using a new theory of two-temperature transport properties recently presented. The latter takes into account the coupling between electrons and heavy species, coupling neglected in the already existing theories of Devoto and Bonnefoi. Transport coefficients are calculated at two-temperatures, the kinetic temperature of electrons Te being different from that of heavy species Th. This paper is divided into two parts. The first one is related to elastic processes and its aim is to compare the results obtained with this new theory for viscosity , translational thermal conductivities tr
e and tr
h and electrical conductivity with the previous results of Bonnefoi. The composition is calculated with the modified equilibrium constant of van de Sanden et al. and the most recent interaction potential are discussed. As it could be expected the electron translational thermal conductivity and the electrical conductivity calculated when taking into account or not the coupling between electrons and heavy species show non-negligible discrepancies. Besides this comparison, the results also show the drastic influence of the non-equilibrium parameter =Te/Th on the values of , , tr
e, and tr
h. 相似文献
104.
C. AutretC. Martin A. MaignanM. Hervieu B. RaveauG. André F. Bourée 《Journal of solid state chemistry》2002,165(1):65-73
The Ho0.5Sr0.5MnO3 perovskite, synthesized in air, has been studied by combining neutron powder and electron diffraction techniques. The Pnma-type structure exhibits a strong tilting of the MnO6 octahedra. This octahedra tilting and microtwinning involve a complex strained structure. No structural transition is observed down to 1.4 K, but short-range A-type antiferromagnetism running over only a few perovskite subcells is evidenced below ≈90 K. The different behavior of this perovskite compared to other Ln0.5Sr0.5MnO3 perovskites is discussed in terms of A-site cationic mismatch. 相似文献
105.
有机金属络合物用于高分子富氧膜的研究进展 总被引:2,自引:0,他引:2
本文介绍了能够可逆吸附分子氧的有机金属络合物用于高分子富氧膜的研究进展,以及以双重吸附理论进行的膜的促进输送机理。 相似文献
106.
Yong Zhao Xianliang Sheng Jin Zhai Lei Jiang Chunhe Yang Zhongwei Sun Yongfang Li Daoben Zhu 《Chemphyschem》2007,8(6):856-861
Titanium dioxide (TiO(2)) photoelectrodes with micro/nano hierarchical branched inner channels have been prepared by an electrohydrodynamic (EHD) technique and assembled to form dye-sensitized solar cells (DSSCs). Excellent penetration of ionic-liquid electrolytes and enhanced light harvesting in the longer wavelength region are realized within the composite-structure electrode, thus a better fill factor (ff) of 75.3 % and higher conversion efficiency (eta) of 7.1 % are obtained for viscous ionic-liquid electrolytes compared to pure nanostructured films. Hierarchical branched channels in the photoanodes can efficiently improve the transport properties of redox-active species in viscous electrolytes, which is demonstrated by electrical impedance spectroscopy (EIS). The incident monochromatic photon-to-electron conversion efficiency (IPCE) shows that enhanced light scattering in the composite film is of benefit for light harvesting and thus for solar energy conversion efficiency. 相似文献
107.
108.
M. R. Yaftian M. Burgard D. Matt C. Wieser C. Dieleman 《Journal of inclusion phenomena and macrocyclic chemistry》1997,27(2):127-140
The complexing, extracting and mobile carrier properties of the tetra(phosphine oxide)-calix[4]arene 1 and the hybrid diamide-di(phosphine oxide)-calix[4]arene 2 were studied. Both ligands give 1 : 1 complexes with alkali cations in THF as shown by the picrate method. 1H NMR experiments were run to follow encapsulation of sodium and potassium cations. The corresponding spectra indicate C2-symmetrical structure. The observed extraction orders of the alkali picrates were as follows K+>Rb+>Li+>Cs+>Na+ for 1 and Li+>Na+>K+>Rb++ for 2. Transport kinetics was analysed by means of a model which assumes pure diffusion and which allows the evaluation of mass transfer coefficients in all systems. These coefficients and their influences on the transport rate are discussed in terms of size of the transporting species in the liquid membrane. 相似文献
109.
Yoshihiko Nishimori Katsuhiko Kanaizuka Dr. Masaki Murata Dr. Hiroshi Nishihara Prof. 《化学:亚洲杂志》2007,2(3):367-376
Films of linear and branched oligomer wires of Fe(tpy)2 (tpy=2,2′:6′,2′′‐terpyridine) were constructed on a gold‐electrode surface by the interfacial stepwise coordination method, in which a surface‐anchoring ligand, (tpy? C6H4N?NC6H4? S)2 ( 1 ), two bridging ligands, 1,4‐(tpy)2C6H4 ( 3 ) and 1,3,5‐(C?C? tpy)3C6H3 ( 4 ), and metal ions were used. The quantitative complexation of the ligands and FeII ions was monitored by electrochemical measurements in up to eight complexation cycles for linear oligomers of 3 and in up to four cycles for branched oligomers of 4 . STM observation of branched oligomers at low surface coverage showed an even distribution of nanodots of uniform size and shape, which suggests the quantitative formation of dendritic structures. The electron‐transport mechanism and kinetics for the redox reaction of the films of linear and branched oligomer wires were analyzed by potential‐step chronoamperometry (PSCA). The unique current‐versus‐time behavior observed under all conditions indicates that electron conduction occurs not by diffusional motion but by successive electron hopping between neighboring redox sites within a molecular wire. Redox conduction in a single molecular wire in a redox‐polymer film has not been reported previously. The analysis provided the rate constant for electron transfer between the electrode and the nearest redox‐complex moiety, k1 (s?1), as well as that for intrawire electron transfer between neighboring redox‐complex moieties, k2 (cm2 mol?1 s?1). The strong effect of the electrolyte concentration on both k1 and k2 indicates that the counterion motion limits the electron‐hopping rate at lower electrolyte concentrations. Analysis of the dependence of k1 and k2 on the potential gave intrinsic kinetic parameters without overpotential effects: k10=110 s?1, k20=2.6×1012 cm2 mol?1 s?1 for [n Fe 3 ], and k10=100 s?1, k20=4.1×1011 cm2 mol?1 s?1 for [n Fe 4 ] (n=number of complexation cycles). 相似文献
110.
用循环伏安法和计时库仑法研究了掺杂亚铁氰化钾离子的聚哟咯膜内的电荷传输问题。实验结果表明,聚吡咯膜内的电荷传递可以处理成电子在膜内的扩散模型,电荷传递速度可以 用电子表观扩散系数(Dapp)来表征。Dapp的大小由聚合物膜的结构、电活怀离子之间的过及对离了在膜中的运动决定。 相似文献