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991.
D.M. Polishchuk A.I. Tovstolytkin Elena Fertman Vladimir Desnenko Anatoly Beznosov Marcela Kajňaková Alexander Feher 《Journal of magnetism and magnetic materials》2012
We have studied by the electron-spin resonance (ESR) and static magnetic field techniques, the La2/3Ba1/3MnO3 perovskite, which was previously shown to exhibit a martensitic phase transformation in the vicinity of Ts∼200 K [Physical Review B 68, 054109 (2003)], leading to its structural phase-segregated state. Resonant absorptions reveal that in the temperature interval from 100 K to 340 K the compound represents a mixture of two ferromagnetic phases possessing different magnetizations, in varying proportions depending on the temperature, and a small amount of a paramagnetic phase. The results agree well with the previous neutron diffraction study. Applied in the ESR experiments, magnetic fields (2–6 kOe) strongly affect the magnetization curves: even magnetic field as high as 700 Oe modifies the anomaly in the phase transformation region and removes the difference between the zero-field cooled and field-cooled magnetization curves, which implies that the difference in the magnetic susceptibility of the coexisting phases is small and the magnetic domain configuration can be easily changed. 相似文献
992.
In this paper we try to bridge breakthroughs in quantitative sociology/econometrics, pioneered during the last decades by Mac Fadden, Brock–Durlauf, Granovetter and Watts–Strogatz, by introducing a minimal model able to reproduce essentially all the features of social behavior highlighted by these authors. 相似文献
993.
Alexander A. Redkin Elena V. Nikolaeva Alexander E. Dedyukhin Yurii P. Zaikov 《Ionics》2012,18(3):255-265
The interrelationship between electrical conductivity, molar volume and enthalpy of mixing was studied for molten chlorides
and their mixtures. The dependence of electrical conductivity and activation energy on the molar volume is different for various
groups of salts. The dependence of specific conductivity on molar volume obtained for molten alkali chlorides was found to
be similar to other chloride salts. The specific conductivity of binary mixtures that lack strong chemical interactions between
the components can also be described by the proposed empirical equation. The enthalpy of mixing should be taken into consideration
for these chemical interactions. 相似文献
994.
995.
E Bellido I Ojea-Jiménez A Ghirri C Alvino A Candini V Puntes M Affronte N Domingo D Ruiz-Molina 《Langmuir : the ACS journal of surfaces and colloids》2012,28(33):12400-12409
Atomic force microscopy is shown to be an excellent lithographic technique to directly deposit nanoparticles on graphene by capillary transport without any previous functionalization of neither the nanoparticles nor the graphene surface while preserving its integrity and conductivity properties. Moreover this technique allows for (sub)micrometric control on the positioning thanks to a new three-step protocol that has been designed with this aim. With this methodology the exact target coordinates are registered by scanning the tip over the predetermined area previous to its coating with the ink and deposition. As a proof-of-concept, this strategy has successfully allowed the controlled deposition of few nanoparticles on 1 μm(2) preselected sites of a graphene surface with high accuracy. 相似文献
996.
Cao Y Galoppini E Reyes PI Duan Z Lu Y 《Langmuir : the ACS journal of surfaces and colloids》2012,28(21):7947-7951
A stepwise surface functionalization methodology was applied to nanostructured ZnO films grown by metal organic chemical vapor deposition (MOCVD) having three different surface morphologies (i.e., nanorod layers (ZnO films-N), rough surface films (ZnO films-R), and planar surface films (ZnO films-P). The films were grown on glass substrates and on the sensing area of a quartz crystal microbalance (nano-QCM). 16-(2-Pyridyldithiol)-hexadecanoic acid (PDHA) was bound to ZnO films-N, -R, and -P through the carboxylic acid unit, followed by a nucleophilic displacement of the 2-pyridyldithiol moiety by single-stranded DNA capped with a thiol group (SH-ssDNA). The resulting ssDNA-functionalized films were hybridized with complementary ssDNA tagged with fluorescein (ssDNA-Fl). In a selectivity control experiment, no hybridization occurred upon treatment with non complementary DNA. The ZnO films' surface functionalization, characterized by FT-IR-ATR and fluorescence spectroscopy and detected on the nano-QCM, was successful on films-N and -R but was barely detectable on the planar surface of films-P. 相似文献
997.
Graf C Gao Q Schütz I Noufele CN Ruan W Posselt U Korotianskiy E Nordmeyer D Rancan F Hadam S Vogt A Lademann J Haucke V Rühl E 《Langmuir : the ACS journal of surfaces and colloids》2012,28(20):7598-7613
The influence of the surface functionalization of silica particles on their colloidal stability in physiological media is studied and correlated with their uptake in cells. The surface of 55 ± 2 nm diameter silica particles is functionalized by amino acids or amino- or poly(ethylene glycol) (PEG)-terminated alkoxysilanes to adjust the zeta potential from highly negative to positive values in ethanol. A transfer of the particles into water, physiological buffers, and cell culture media reduces the absolute value of the zeta potential and changes the colloidal stability. Particles stabilized by L-arginine, L-lysine, and amino silanes with short alkyl chains are only moderately stable in water and partially in PBS or TRIS buffer, but aggregate in cell culture media. Nonfunctionalized, N-(6-aminohexyl)-3-aminopropyltrimethoxy silane (AHAPS), and PEG-functionalized particles are stable in all media under study. The high colloidal stability of positively charged AHAPS-functionalized particles scales with the ionic strength of the media, indicating a mainly electrostatical stabilization. PEG-functionalized particles show, independently from the ionic strength, no or only minor aggregation due to additional steric stabilization. AHAPS stabilized particles are readily taken up by HeLa cells, likely as the positive zeta potential enhances the association with the negatively charged cell membrane. Positively charged particles stabilized by short alkyl chain aminosilanes adsorb on the cell membrane, but are weakly taken up, since aggregation inhibits their transport. Nonfunctionalized particles are barely taken up and PEG-stabilized particles are not taken up at all into HeLa cells, despite their high colloidal stability. The results indicate that a high colloidal stability of nanoparticles combined with an initial charge-driven adsorption on the cell membrane is essential for efficient cellular uptake. 相似文献
998.
Boron compounds have been traditionally regarded as "Lewis acids" preferring to accept electrons rather than donate them in the course of their reactions but current examples of unusual reactivity between tricoordinated boranes and electrophilic sites suggest a new conceptual context for the boryl moieties, based on their nucleophilic character which can be enhanced depending on the substituents on boron. 相似文献
999.
Carlstedt J Bilalov A Krivtsova E Olsson U Lindman B 《Langmuir : the ACS journal of surfaces and colloids》2012,28(5):2387-2394
Full equilibrium phase diagrams are presented for two ternary systems composed of the cationic surfactant dodecyltrimethylammonium bromide (DTAB), water (D(2)O), and a cyclodextrin, either β-cyclodextrin (β-CD) or (2-hydroypropyl)-β-cyclodextrin (2HPβCD). (2)H NMR, SAXS, WAXS, and visual examination were used to determine the phase boundaries and characterize the nature of the phases formed. Additionally, diffusion (1)H NMR was used to investigate parts of the diagrams. The water solubility of 2HPβCD is 80% (w/w), whereas it is only 1.85% (w/w) for β-CD. Solubility increases for both species upon complexation with DTAB; while the increase is minute for 2HPβCD, it is dramatic for β-CD. Both systems displayed an isotropic liquid solution (L(1)) one-phase region, the extension of which differs extensively between the two systems. Additionally, the DTAB:2HPβCD:water system also comprised a normal hexagonal (H(1)) area, which was not found for the DTAB:β-CD:water system. In the DTAB:β-CD:water system, on the other hand, we found cocrystallization of DTAB and β-CD. From this work we conclude that DTAB and CD molecules form 1:1 inclusion complexes with high affinities. Moreover, we observed indications of an association of 2HPβCD to DTAB micelles in the isotropic solution phase, which was not the case for β-CD and DTAB micelles. This is, to our knowledge, the first complete phase diagrams of surfactant-CD mixtures; as a novel feature it includes the observation of cocrystallization at high concentrations. 相似文献
1000.
In this work we present a new method to describe movements of stick-slip microdrives. On the microscopic scale we model the contact between actuator and slider as a dynamic tangential contact using the method of reduction of dimensionality. On the macroscopic scale simple one- and three-dimensional equations of motion are derived. An algorithm to solve these equations will be introduced. The results of the simulation will be compared qualitatively and quantitatively to experimental investigations. Even for the simplest assumed model it proves that experimental and numerical values correlate excellently. 相似文献