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971.
Daschbach JL Chang TM Corrales LR Dang LX McGrail P 《The journal of physical chemistry. B》2006,110(35):17291-17295
Molecular dynamics simulations are used to investigate the molecular interactions of hydrogen-loaded beta-hydroquinone clathrate. It is found that, at lower temperatures, higher loadings are more stable, whereas at higher temperatures, lower loadings are more stable. Attractive forces between the guest and host molecules lead to a stabilized minimum-energy configuration at low temperatures. At higher temperatures, greater displacements take the system away from the shallow energy minimum, and the trend reverses. The nature of the cavity structure is nearly spherical for a loading of one, leads to preferential occupation near the hydroxyl ring crowns of the cavity with a loading of two, and at higher loadings, leads to occupation of the interstitial sites (the hydroxyl rings) between cages by a single H(2) molecule with the remaining molecules occupying the equatorial plane of the cavity. Occupation of the interstitial positions of the cavities leads to facile diffusion. 相似文献
972.
Dang TT Albrecht U Gerwien K Siebert M Langer P 《The Journal of organic chemistry》2006,71(6):2293-2301
The one-pot cyclization of dilithiated oximes with epibromohydrin provided a convenient and regioselective approach to 6-hydroxymethyl-5,6-dihydro-4H-1,2-oxazines. The reaction of the latter with phosphorus tribromide resulted in a Beckmann rearrangement and formation of 5-bromomethyl-2-iminotetrahydrofurans. The reaction of dilithiated hydrazones with epibromohydrin afforded oxazolo[3,4-b]pyridazin-7-ones, which were formed by a novel domino cyclization. 相似文献
973.
The sorption of selenite from aqueous solutions onto hematite was investigated as a function of pH (2-12), ionic strength (0.01-0.1 M), and concentration of selenium (10(-7)-10(-2) M). The sorption may proceed according to two processes: surface complexation, followed by the precipitation of ferric selenite starting at approximate [Se] = 4 x 10(-4) M (surface coverage>ca. 2 at nm(-2)). The sorption isotherms have been fitted by a Tempkin equation. A surface complexation model (2-pK/Constant Capacitance Model) was used to fit the sorption data. The nature of the surface species of selenite cannot be determined by modeling since monodentate >FeOSe(O)O- or >FeOSe(O)OH and bidentate (>FeO)2SeO surface complexes are both able to fit the experimental data. The reversibility and kinetics of sorption were also studied. The affinity of selenite ions toward hematite, expressed as the distribution coefficient with respect to the surface area (K(D) in L m(-2)), was compared with results published for other ferric oxides (goethite and amorphous ferric oxide). It was found that the reactivity toward selenite is similar, contrary to acid-base properties which depend on the nature of the oxide and its level of purity. 相似文献
974.
Wolfgang Stadlbauer Anna E. Tubl Hoai V. Dang Claudia Reidlinger Klaus Zangger 《Journal of heterocyclic chemistry》2006,43(1):117-125
4‐Chloro‐ or 4‐tosyloxyquinolines 1 and 10 react with CH‐acidic compounds such as malonates 2a,b , ethyl cyanoacetate ( 2c ), malononitrile ( 2d ), ethyl acetoacetate ( 2e ), acetylacetone ( 2f ) or dimedone ( 2g ) under mild conditions and good yields to quinolin‐4‐yl substituted derivatives 3‐8 and 11 . With 3‐phenylsulfonylquinolones 1i‐k a redox reaction to 2‐hydroxy‐2‐quinolin‐4‐yl‐malonates 9 was observed. Amination of 3‐nitroquinolinyl malonate 3f leads to malonester‐amides 13 and 14 . 相似文献
975.
A new vanadium molybdenum mixed oxide V1.1Mo0.9O5 [V(V)0.2V(IV)0.9Mo(VI)0.9O5] has been synthesized, as a pure phase, via hydrothermal methods in the presence of molybdic acid and vanadyl sulfate. Its crystal structure has been solved ab initio from high-resolution powder diffraction data collected at the ESRF beamline ID31. This compound crystallizes in the monoclinic symmetry, space group C2/m, with cell dimensions , , , β=90.625(3)° and Z=2 per formula. The structure consists of double strings of VO5 square pyramids sharing edges and corners along [100] and [010], and more weakly bound along [001]. In this latter direction, the bond (V,Mo)-O=2.377 Å, while remaining long, leads for the first time to the interpenetration of the apical oxygens of the [(V,Mo)2O5]n layers, resulting in a three-dimensional (3D) structure closely related to R-Nb2O5. This structure will be compared to the pure layer structure of V2O5 where this bond reaches 2.793 Å. 相似文献
976.
A. Crisan V.S. Dang P. Mikheenko Y.Y. Tse A. Sarkar J. Bowen J.S. Abell 《Physica C: Superconductivity and its Applications》2010,470(1):55-60
Using Pulsed Laser Deposition we have fabricated thick quasi-multilayers composed of incomplete layers of PrBa2Cu3Ox (PrBCO) nano-dots and layers of YBa2Cu3O7?δ (YBCO). The number of such sequences was between 2 and 6, with the thickness of individual YBCO layers between 565 and 885 nm, and total thickness between 1.13 and 5.31 μm. For the thinner quasi-multilayer, DC magnetization studies showed an increase in the critical current density Jc at all fields in comparison with a pure YBCO reference sample, while the thicker samples showed an increased Jc only in high fields. We have also investigated the frequency dependence of Jc from AC susceptibility studies and found that the pinning potential is well described by a logarithmic dependence on current density. Pinning potentials in PrBCO/YBCO quasi-multilayers also proved to be higher than in the reference sample at high fields. From angle-dependent transport measurements we have found indications of strong pinning centres induced by the (PrBCO) nano-dots, both isotropic and c-axis correlated. 相似文献
977.
Yan Dang Yulei Zhang Li Fan Hsinchun Chen Mihail C. Roco 《Journal of nanoparticle research》2010,12(3):687-706
Nanotechnology patent applications published during 1991–2008 have been examined using the “title–abstract” keyword search
on esp@cenet “worldwide” database. The longitudinal evolution of the number of patent applications, their topics, and their respective
patent families have been evaluated for 15 national patent offices covering 98% of the total global activity. The patent offices
of the United States (USA), People’s Republic of China (PRC), Japan, and South Korea have published the largest number of
nanotechnology patent applications, and experienced significant but different growth rates after 2000. In most repositories,
the largest numbers of nanotechnology patent applications originated from their own countries/regions, indicating a significant
“home advantage.” The top applicant institutions are from different sectors in different countries (e.g., from industry in
the US and Canada patent offices, and from academe or government agencies at the PRC office). As compared to 2000, the year
before the establishment of the US National Nanotechnology Initiative (NNI), numerous new invention topics appeared in 2008,
in all 15 patent repositories. This is more pronounced in the USA and PRC. Patent families have increased among the 15 patent
offices, particularly after 2005. Overlapping patent applications increased from none in 1991 to about 4% in 2000 and to about
27% in 2008. The largest share of equivalent nanotechnology patent applications (1,258) between two repositories was identified
between the US and Japan patent offices. 相似文献
978.
D. P. Kozlenko N. T. Dang Z. Jirák S. E. Kichanov E. V. Lukin B. N. Savenko L. S. Dubrovinsky C. Lathe C. Martin 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,77(3):407-411
The crystal and magnetic structures of Pr0.15Sr0.85MnO3
manganite have been studied by means of powder X-ray and neutron diffraction
in the temperature range 10–400 K at high external pressures up to 55 and 4 GPa, respectively. A structural phase transition
from cubic to tetragonal
phase upon compression was observed, with large positive pressure
coefficient of transition temperature dT
ct
/dP = 28(2) K/GPa. The C-type
antiferromagnetic (AFM) ground state is formed below T
N
≈ 260 K
at ambient pressure. While at ambient pressure the structural and magnetic
transition temperatures are close, T
ct
~ T
N
, upon compression
they become decoupled with T
N
≪ T
ct
due to much weaker
T
N
pressure dependence with coefficient dT
N
/dP = 3.8(1) K/GPa. 相似文献
979.
H. M.?Dang M. J.?van Goethem E. R.?van der Graaf S.?Brandenburg R.?Hoekstra T.?Schlath?lter 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(1):51-58
Interaction of ionizing radiation with plasmid DNA can lead to formation of single strand breaks, double strand breaks and
clustered lesions. We have investigated the response of the synthetic plasmid pBR322 in aqueous solution upon irradiation
with 12C ions under spread-out Bragg peak conditions (densely ionizing) and with 137Cs γ-photons (sparsely ionizing) as a function of dose. To evaluate the relevance of indirect effects, i.e. influences of diffusion
limited radical induced DNA damage triggered by water radiolysis, the experiments were performed at various concentrations
of the radical scavenger mannitol. Agarose gel electrophoresis was employed to quantify the DNA damage. At low scavenger concentration
for a given dose DNA damage is higher for γ-photons than for 12C. For the latter, the microscopic dose distribution is inhomogeneous, with very high dose deposited along the few tracks
through the solution. This is in agreement with the concept that scavengers efficiently reduce damage for γ-photons, implying that the underlying damage mechanism is single strand break induction by OH radicals. For 12C induced damage, the fraction of SSB and DSB that is unaffected by radical scavengers and thus due to direct effect is quantified. 相似文献
980.
Traffic noise prediction models in France are based on vehicle noise emission values defined by the French Guide du Bruit des Transports Terrestres (Noise Guide for Ground Transport - Noise levels prediction). These emission values are suited for models addressing the noise assessments of road infrastructures and the dimensioning of acoustic protections, needing traffic noise estimations in terms of ?Aeq over a long period of time (an hour or more).The values, obtained from measurements collected in the 70s, are updated in the publication of a new guide (Methodological Guide, Vehicle noise emissions, to be published), which addresses the road surface influence on tyre/road noise. The emission values are now expressed through the contributions of a power unit component, function of traffic speed, traffic flow type and road declivity, and of a rolling noise component, function of traffic speed and road pavement.The paper outlines the procedures followed to determine the components, gives their numerical values, and illustrates some vehicle noise emissions. 相似文献