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101.
Rankin S Oswald J Barlow J Lammers M 《The Journal of the Acoustical Society of America》2007,121(2):1213-1218
Vocalizations from the northern right whale dolphin, Lissodelphis borealis, were recorded during a combined visual and acoustic shipboard survey of cetacean populations off the west coast of the United States. Seven of twenty single-species schools of L. borealis produced click and pulsed vocalizations. No whistles were detected during any of the encounters. Clicks associated with burst-pulse vocalizations were lower in frequency and shorter in duration than clicks associated with echolocation. All burst-pulse sounds were produced in a series containing 6-18 individual burst-pulses. These burst-pulse series were stereotyped and repeated. A total of eight unique burst-pulse series were detected. Variation in the temporal characteristics of like units compared across repeated series was less than variation among all burst-pulses. These stereotyped burst-pulse series may play a similar communicative role as do stereotyped whistles found in other delphinid species. 相似文献
102.
103.
Robert D. Shannon Olaf Medenbach Philippe Ghosez 《Journal of solid state chemistry》2009,182(10):2762-2768
The refractive indices of ZrW2O8, measured at wavelengths of 435.8-643.8 nm, were used to calculate nD at λ=589.3 nm and n∞ at λ=∞ from a one-term Sellmeier equation. Refractive indices, nD and dispersion values, A, are, respectively, 1.8794 and 114×10−16 m2. The high dispersion, relative to other molybdates, tungstates and Zr-containing compounds, is attributed to the low value of Eo=7.7 eV and mean cation coordination number. Total electronic polarizabilities, αtotal, were calculated from n∞ and the Lorenz-Lorentz equation. The unusually large difference between the observed polarizability of 20.087 Å3 and the calculated total polarizability αT of 17.59 Å3 (Δ=+12.4%) is attributed to (1) a large M-O-W angle, (2) a high degree of W 5d-O(terminal) 2p and Zr nd-O 2p hybridization, and (3) unusually high oxygen displacement factors, B(O), normalized to B(W). 相似文献
104.
Among the families of peptidomimetic foldamers under development as novel biomaterials and therapeutics, poly-N-substituted glycines (peptoids) with alpha-chiral side chains are of particular interest for their ability to adopt stable, helical secondary structure in organic and aqueous solution. Here, we show that a peptoid 22-mer with a biomimetic sequence of side chains and an amphipathic, helical secondary structure acts as an excellent mimic of surfactant protein C (SP-C), a small protein that plays an important role in surfactant replacement therapy for the treatment of neonatal respiratory distress syndrome. When integrated into a lipid film, the helical peptoid SP mimic captures the essential surface-active behaviors of the natural protein. This work provides an example of how an abiological oligomer that closely mimics both the hydrophobic/polar sequence patterning and the fold of a natural protein can also mimic its biophysical function. 相似文献
105.
JP Safko JE Kuperstock SM McCullough AM Noviello X Li JP Killarney C Murphy HH Patterson CA Bayse RD Pike 《Dalton transactions (Cambridge, England : 2003)》2012,41(38):11663-11674
The synthesis, X-ray structures and photophysics of ten complexes of CuX (X = I or Br) with bridging N-substituted and N,N'-disubstituted piperazines (Pip) are presented. Depending on the steric demand of the Pip substituents, the complexes fall into four categories: (CuX)(4)(Pip)(2), which are networks of linked Cu(4)X(4) cubane units, (CuX)(2)(Pip), which are chains of linked Cu(2)X(2) rhombs, and (CuX)(2)(Pip)(2) or (CuX)(4)(Pip)(4), which are simple rhomboid dimers and cubane tetramers. A combination of spectroscopic studies and DFT calculations was used to investigate the luminescence of the products. The results suggest that the relatively high energy emission seen in dimers is due to cluster-centred (XMLT/metal-centred) excitations for the aliphatic amines and MLCT (d →π*) for aromatic amines, and low energy emission seen in the tetramers is the result of cluster-centred transitions. The (CuI)(2)(Pip) complexes act as sensor materials, undergoing irreversible reaction with aliphatic and aromatic amines (Nu) in the vapour state, irreversibly producing cubanes (CuI)(4)Nu(4), with corresponding production of long wavelength emission. 相似文献
106.
We consider random analytic functions defined on the unit disk of the complex plane f(z) = ?n=0¥ an Xn znf(z) = \sum_{n=0}^{\infty} a_{n} X_{n} z^{n}, where the X
n
’s are i.i.d., complex-valued random variables with mean zero and unit variance. The coefficients a
n
are chosen so that f(z) is defined on a domain of ℂ carrying a planar or hyperbolic geometry, and Ef(z)[`(f(w))]\mathbf{E}f(z)\overline{f(w)} is covariant with respect to the isometry group. The corresponding Gaussian analytic functions have been much studied, and
their zero sets have been considered in detail in a monograph by Hough, Krishnapur, Peres, and Virág. We show that for non-Gaussian
coefficients, the zero set converges in distribution to that of the Gaussian analytic functions as one transports isometrically
to the boundary of the domain. The proof is elementary and general. 相似文献
107.
Cook SL Zimmermann CM Singer D Fedorova M Hoffmann R Jackson GP 《Journal of mass spectrometry : JMS》2012,47(6):786-794
The fragmentation behavior of the 2+ and 3+ charge states of eleven different phosphorylated tau peptides was studied using collision-induced dissociation (CID), electron transfer dissociation (ETD) and metastable atom-activated dissociation (MAD). The synthetic peptides studied contain up to two known phosphorylation sites on serine or threonine residues, at least two basic residues, and between four and eight potential sites of phosphorylation. CID produced mainly b-/y-type ions with abundant neutral losses of the phosphorylation modification. ETD produced c-/z-type ions in highest abundance but also showed numerous y-type ions at a frequency about 50% that of the z-type ions. The major peaks observed in the ETD spectra correspond to the charge-reduced product ions and small neutral losses from the charge-reduced peaks. ETD of the 2+ charge state of each peptide generally produced fewer backbone cleavages than the 3+ charge state, consistent with previous reports. Regardless of charge state, MAD achieved more extensive backbone cleavage than CID or ETD, while retaining the modification(s) in most cases. In all but one case, unambiguous modification site determination was achieved with MAD. MAD produced 15-20% better sequence coverage than CID and ETD for both the 2+ and 3+ charge states and very different fragmentation products indicating that the mechanism of fragmentation in MAD is unique and complementary to CID and ETD. 相似文献
108.
Mohammad Ghaffari Mark Shannon H. Hui Ooi Kiang Tan Ahmad Irannejad 《Surface science》2012,606(5-6):670-677
In this report, SrTi(1 ? x)Fe(x)O(3 ? δ) photocatalyst powder was synthesized by a high temperature solid state reaction method. The morphology, crystalline structures of obtained samples, was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM), respectively. The electronic properties and local structure of the perovskite STFx (0 ≤ x ≤ 1) systems have been probed by extended X-ray absorption fine structure (EXAFS) spectroscopy. The effects of iron doping level x (x = 0–1) on the crystal structure and chemical state of the STFx have been investigated by X-ray photoelectron spectroscopy and the valence band edges for electronic band gaps were obtained for STFx by ultraviolet photoelectron spectroscopy (UPS). A single cubic perovskite phase of STFx oxide was successfully obtained at 1200 °C for 24 h by the solid state reaction method. The XPS results showed that the iron present in the STFx perovskite structure is composed of a mixture of Fe3+ and Fe4+ (SrTi(1 ? x)[Fe3+, Fe4+](x)O(3 ? δ)). When the content x of iron doping was increased, the amount of Fe3+ and Fe4+ increased significantly and the oxygen lattice decreased on the surface of STFx oxide. The UPS data has confirmed that with more substitution of iron, the position of the valence band decreased. 相似文献
109.
Madlene U. Koller Katrina L. Peariso Tina S. Guion Shannon Studer Martinez Charles F. Beam 《合成通讯》2013,43(19):2963-2974
2-, 3-, or 4-Picolyllithium was prepared in excess lithium diiso-propylamide and condensed with several hydroxy-benzaldehydes and 4-hydroxy-acetophenone to afford substituted hydroxyphenyl-pyridyl-ethanols and α-hydroxyphenyl-α-methylpyridineethanols. In two instances. 3-picolyllithium condensed with aldehydes to presumably form the hydroxyphenyl-pyridyl-ethanol, which underwent linear dehydration to the substituted pyridyl-ethylenyl-phenol. 相似文献
110.