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111.
We show that a compact embedded hypersurface ${S\subset\mathbb{R}^{n+1}}$ with constant higher-order mean curvature in a convex piecewise smooth cone C which is perpendicular to ?C is part of a hypersphere. Also we prove that an embedded disk type constant mean curvature surface ${S\subset\mathbb{R}^3}$ in a convex polyhedral cone C which makes constant contact angles with ?C is a spherical cap if C has at most five faces. This condition on the number of faces can be dropped if C is a right cone over a regular n-gon and the contact angles are the same on ?S. 相似文献
112.
A series of iridium tetrahydride complexes [Ir(H)4(PSiP‐R)] bearing a tridentate pincer‐type bis(phosphino)silyl ligand ([{2‐(R2P)C6H4}2MeSi]−, PSiP‐R, R=Cy, iPr, or tBu) were synthesized by the reduction of [IrCl(H)(PSiP‐R)] with Me4N ⋅ BH4 under argon. The same reaction under a nitrogen atmosphere afforded a rare example of thermally stable iridium(III)–dinitrogen complexes, [Ir(H)2(N2)(PSiP‐R)]. Two isomeric dinitrogen complexes were produced, in which the PSiP ligand coordinated to the iridium center in meridional and facial orientations, respectively. Attempted substitution of the dinitrogen ligand in [Ir(H)2(N2)(PSiP‐Cy)] with PMe3 required heating at 150 °C to give the expected [Ir(H)2(PMe3)(PSiP‐Cy)] and a trigonal bipyramidal iridium(I)–dinitrogen complex, [Ir(N2)(PMe3)(PSiP‐Cy)]. The reaction of [Ir(H)4(PSiP‐Cy)] with three equivalents of 2‐norbornene (nbe) in benzene afforded [IrI(nbe)(PSiP‐Cy)] in a high yield, while a similar reaction of [Ir(H)4(PSiP‐R)] with an excess of 3,3‐dimethylbutene (tbe) in benzene gave the C H bond activation product, [IrIII(H)(Ph)(PSiP‐R)], in high yield. The oxidative addition of benzene is reversible; heating [IrIII(H)(Ph)(PSiP‐Cy)] in the presence of PPh3 in benzene resulted in reductive elimination of benzene, coordination of PPh3, and activation of the C H bond of one aromatic ring in PPh3. [IrIII(H)(Ph)(PSiP‐R)] catalyzed a direct borylation reaction of the benzene C H bond with bis(pinacolato)diboron. Molecular structures of most of the new complexes in this study were determined by a single‐crystal X‐ray analysis. 相似文献
113.
Choi CB Kim SY Lee SH Jahng GH Kim HY Choe BY Ryu KN Yang DM Yim SV Choi WS 《Magnetic resonance imaging》2011,29(1):32-39
Parkinson's disease (PD) is a neurodegenerative disorder characterized by the progressive loss of the dopaminergic neurons in the substantia nigra pars compacta, which projects to the striatum. We induced a selective loss of nigrostriatal dopamine neurons, by infusing the mitochondrial complex 1 inhibitor 1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine (MPTP) into adult beagle dogs (N=5). Single voxel 1H water suppressed magnetic resonance spectroscopy (1H-MRS) at 3 T was used to assess the metabolic changes in the striatum of canine before and after MPTP intoxication. The metabolite spectra obtained from the striatum (voxel size: 2 cm3) showed a lower N-acetyl aspartate to total creatine (creatine+phosphocreatine) ratio after MPTP intoxication. There were no significant differences in other metabolite ratios such as glutamate+glutamine, choline-containing compounds (glycerophosphocholine+phophorylcholine and myo-inositol). Our findings indicated that 1H-MRS is a sensitive, noninvasive measure of neural toxicity and biochemical alterations of the striatum in a canine model of PD, and further studies are needed to confirm brain metabolic changes in association with progression of MPTP-intoxication. 相似文献
114.
Seung-Man Yu Kyung-Rae Dong Youn-Sang Ji Eun-Hoe Goo Woon-Kwan Chung Jong-Woong Lee Chong-Hwan Choe 《Applied magnetic resonance》2011,40(3):291-301
Gadolinium is the central metal that is used as magnetic resonance imaging (MRI) contrast media. Because the metal has toxicity
on its own, it causes fibrosis or sclerosis of skin or internal organs, which may lead to disability in joint movement, or
even death in the worst case. In the current study, the T
1 contrast media, Dotarem, was diluted to various molarities to measure the signal intensity of T
1-weighted images as a function of the molarity. The molarity that showed the maximum measurement value of the signal intensity
was examined to determine the proper amount of contrast media injected for the MRI scan. The change in the intensity of the
signal from the tumor tissue was determined based on the passage of time after injection. The distribution of the maximum
signal intensities depending on the time to repeat showed that the signal distribution had >95% of the maximum values when
the dilution concentration was in the range of 0.00095–0.00135 mmol/ml. Thus, it is most desirable when 0.084 mmol/kg (patient
weight) of contrast media is injected. In experiments involving tumors 0.084, 0.1, and 0.15 mmol/kg were injected to measure
the average signal intensity for each molarity. Compared to the signal intensity at a molarity of 0.084 mmol/kg, the three
patient’s signal intensities were measured to increase by 6.2, 7.6, and 5.7% at a molarity of 0.1 mmol/kg, and by 21.4, 18.8,
and 17.7% at a molarity of 0.15 mmol/kg. However, according to the correlation between the contract media injection amount
and the signal intensity increase, the contrast effect was not improved much despite the increase in the injection amount
by 19.04 and 78.5%. This study revealed that the optimal level of contrast media of 0.084 mmol/kg body weight should be administered
by considering the body weight of patients and the effects of media to reduce side effects of a high dose of contrast media
and to prevent environmental pollution. 相似文献
115.
The RITP-emulsion polymerization of styrene in the presence of molecular iodine has been successfully performed using potassium persulfate (KPS) as an initiator and 1-hexadecanesulfonate as an emulsifier under argon atmosphere at 80°C for 7 hrs in the absence of light. The effects of the iodine concentration, molar ratio between KPS and iodine, and solid contents on the molecular weight of polystyrene (PS) were studied. As the iodine concentration increased from 0.05 to 0.504 mmol under the fixed [KPS]/[I(2)] ratio at 4.5, the weight-average molecular weight of PS substantially decreased from 126,120 to 35,690 g/mol, the conversion increased from 85.0% to 95.2%, and the weight-average particle diameter decreased from 159 to 103 nm. In addition, as the ratio of [KPS]/[I(2)] increased from 0.5 to 6.0 at the fixed [I(2)] of 0.504 mmol, the weight-average molecular weight of PS decreased from 72,170 to 30,640 g/mol with high conversion between 81.7% and 96.5%. Moreover, when the styrene solid content increased from 10 to 40 wt.% at the fixed [KPS]/[I(2)] ratio of 4.5, the weight-average molecular weight of PS varied between 33,500 and 37,200 g/mol, the conversion varied between 94.9% and 89.7% and the weight-average diameter varied from 122 to 205 nm. Thus, the control of molecular weight of PS less than 100,000g/mol with high conversion (95%) and particle stability of up to 40 wt.% solid content were easily achieved through the usage of iodine with suitable ratio of [KPS]/[I(2)] in the RITP-emulsion polymerization technique, which is of great industrial importance. 相似文献
116.
Ha TL Kim HJ Shin J Im GH Lee JW Heo H Yang J Kang CM Choe YS Lee JH Lee IS 《Chemical communications (Cambridge, England)》2011,47(32):9176-9178
A platform protocol developed based on the hollow manganese oxide nanoparticles provided multimodal diagnostic agents, which allow the selectively detect vulva cancer with T(1)-weighted in vivo MRI. 相似文献
117.
Charge exchange technique has been used to detect the presence of long-lived excited electronic states of trans-, cis-, and 1,1-C2H2Cl 2 +· . The \(\tilde B\) states of the three cations which are formed by removal of an electron from an in-plane chlorine nonbonding orbital of the corresponding neutrals have been found to have long lifetimes (tens of microseconds or longer). Whether the à states formed by removal of an electron from the other in-plane chlorine nonbonding orbitals are long-lived also can not be determined by the present experiments. Cations in the excited electronic states above the \(\tilde B\) states were not detected because of their prompt dissociation following intramolecular relaxation or radiative decay. 相似文献
118.
Charge exchange ionization in collision cells installed in a double focusing mass spectrometer with reversed geometry has been used to detect the presence of a long-lived excited electronic state of benzene ion. In particular, the first collision cell located between the ion source and the magnetic sector was modified to serve as an ion source for the reagent ion generated by charge exchange with the primary ion. Strong reagent ion signals were observed when the ionization energies of the reagents (1,3-C4H6, CS2, CH3Cl) were lower than the recombination energy (approximately 11.5 eV) of the excited state benzene ion, while the signals were negligible for reagents (CH3F,CH4) with higher ionization energy. The fact that a strong signal is observable only for electronically exoergic charge exchange is useful for detecting the presence of a long-lived electronically excited state. 相似文献
119.
120.
April R. Rodriguez Uh‐Joo Choe Daniel T. Kamei Timothy J. Deming 《Macromolecular bioscience》2012,12(6):805-811
The design, synthesis, and self‐assembly of the first dual hydrophilic triblock copolypeptide vesicles, ${\rm R}_{m}^{{\rm H}} {\rm E}_{n} {\rm L}_{o} $ and ${\rm K}_{m}^{{\rm P}} {\rm R}_{n}^{{\rm H}} {\rm L}_{o} $ , is reported. Variation of the two distinct hydrophilic domains is used to tune cellular interactions without disrupting the self‐assembled structure. The aqueous self‐assemblies of these triblock copolypeptides in water are characterized using microscopy and DLS. Cell culture studies are used to evaluate cytotoxicity as well as intracellular uptake of the vesicles. The ability of polypeptides to incorporate ordered chain conformations that direct self‐assembly, combined with the facile preparation of functional, multiblock copolypeptide sequences of defined lengths, allow the design of vesicles attractive for development as drug carriers.