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71.
Corral A 《Physical review letters》2006,97(17):178501
Spatiotemporal properties of seismicity are investigated for a worldwide (WW) catalog and for southern California in the stationary case (SC), showing a nearly universal scaling behavior. Distributions of distances between consecutive earthquakes (jumps) are magnitude independent and show two power-law regimes, separated by jump values about 200 (WW) and 15 km (SC). Distributions of waiting times conditioned to the value of jumps show that both variables are correlated, in general, but turn out to be independent when only short or long jumps are considered. Finally, diffusion profiles are found to be independent on the magnitude, contrary to what the waiting-time distributions suggest. 相似文献
72.
Terpene alkyne systems act as templates in the preparation of natural product hybrids and in macrocyclic structures having up to four terpene units and eight Co-atoms, which are built by using the Nicholas reaction. 相似文献
73.
Surface‐enhanced Raman scattering and density functional theory studies of bis(4‐aminophenyl)sulfone
Guillermo Diaz‐Fleming Freddy Clis Carlos Fredes Marcelo Campos‐Vallette Alvaro E. Aliaga Rainer Koch 《Journal of Raman spectroscopy : JRS》2010,41(2):160-166
Raman and surface‐enhanced Raman scattering (SERS) spectra of dapsone by using colloidal silver nanoparticles have been recorded. Density functional theory was used for the optimization of ground state geometries and simulation of the vibrational spectrum of this molecule. The SERS spectrum with a large silver cluster as a model metallic surface was simulated for the first time. Taking into account the experimental and calculated Raman as well as the SERS normal modes and the corresponding assignments, along with the modeling of the free dapsone and the one in the presence of the colloidal silver nanoparticles, the importance of the sulfone group on the SERS effect in dapsone was inferred. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
74.
Poly(2,5-dimethoxy-p-phenylenevinylene) (dMeOPPV) has been formed in the intergallery spacing of a montmorillonite by introducing the (2,5-dimethoxy-1,4-phenylene)bis(methylene-S-tetrahydrothiophenium) monomer by ion exchange, increasing the basicity of the solid aluminosilicate with Cs(+) and subsequent heating at 200 degrees C. dMeOPPV@montmorillonite was characterized by optical spectroscopy, FT-IR spectroscopy, solid-state (13)C NMR, photoluminescence, and chemical analysis. All the data are compatible with that reported in the literature for pure dMeOPPV. The dMeOPPV polymer incorporated inside montmorillonite exhibits a green light emission which makes the organic polymer very attractive for its application in polymer light-emitting diodes (PLEDs). The new polymeric material can be submitted to laser irradiation (laser power, 10 mJ pulse(-1)) under oxygen without decomposition. 相似文献
75.
Díez A Fernández J Lalinde E Moreno MT Sánchez S 《Dalton transactions (Cambridge, England : 2003)》2008,(36):4926-4936
A series of homoleptic and heteroleptic platinum(ii) complexes [Pt(C[triple bond, length as m-dash]CFc)(2)(L-L)] (L-L = COD , 1,1'-bis(diphenylphosphino)ferrocene (dppf) ), Q(2)[cis/trans-Pt(C(6)F(5))(2)(C[triple bond, length as m-dash]CFc)(2)] (cis, Q = PMePh(3), ; trans, Q = NBu(4), ), (NBu(4))[Pt(bzq)(C[triple bond, length as m-dash]CFc)(2)] (Hbzq = 7,8-benzoquinoline) and (NBu(4))(2)[Pt(C[triple bond, length as m-dash]CFc)(4)] has been synthesized and characterized spectroscopically and the structures of .2CHCl(3), and .2H(2)O.2CH(2)Cl(2) confirmed by single-crystal X-ray studies. The anion of complex , shows strong O-Hpi(C[triple bond, length as m-dash]C) interactions and weaker C-Clpi(C[triple bond, length as m-dash]C) contacts between the protons of two water and two CH(2)Cl(2) molecules and the C(alpha)[triple bond, length as m-dash]C(beta) of mutually cis alkynyl groups. In this complex the presence of additional O-HH-C(Cp) and C-ClH-C(Cp) contacts gives rise to an extended bidimensional network. The optical and electrochemical properties of all derivatives have been examined. It is remarkable that for complexes and a facile oxidatively induced coupling, giving rise to 1,4-diferrocenylbutadiyne, is observed, this also having been proven by chemical oxidation. 相似文献
76.
We discuss the deformed sigma-model that arises when considering four-dimensional N=2 abelian vector multiplets in the presence of an arbitrary chiral background field. In addition, we allow for a class of deformations of special geometry by non-holomorphic terms. We analyze the geometry of the sigma-model in terms of intrinsic torsion classes. We show that, generically, the deformed geometry is non-Kähler. We illustrate our findings with an example. We also express the deformed sigma-model in terms of the Hesse potential that underlies the real formulation of special geometry. 相似文献
77.
Desmond Macleod-Carey Giovanni F. Caramori Raúl Guajardo-Maturana Dayan Paez-Hernandez Alvaro Muñoz-Castro Ramiro Arratia-Perez 《International journal of quantum chemistry》2019,119(2):e25777
The inclusion of relativistic effects to understand chemical structures and related properties brings to the scientific community challenging study cases, showing the rich diversity of chemical behavior of the different elements along the periodic table. The results highlighted here represent applications of relativistic methodologies to study the nature of bonding and a prediction of optical and magnetic properties of meaningful chemical entities containing heavy atoms, all made in Latin America. The good agreement between calculated and experimental observables in many molecular and cluster-like systems ratifies that relativistic methods are appropriate to describe these entities realistically. We expect to enhance our knowledge in these methodologies, currently included in doctoral programs in our region. 相似文献
78.
Nickolas D. Charistos Peng Jin Alvaro Muñoz-Castro 《International journal of quantum chemistry》2019,119(13):e25919
Spherical fullerenes offer noteworthy structures usually involving six- and five-membered faces, with application in technological issues. In this sense, cavernous spherical-like structures bearing larger holes provide interesting examples for further understanding of structure-properties relationship. Here, we explored the magnetic response of a proposed cavernous nitride fullerene, C24N24, which has a Oh-symmetry with six N4-macrocyclic and eight 1,3,5-triazine faces displaying 48-π electrons. C24N24 exhibits a local aromatic behavior owing to the contrasting antiaromatic response of the N4-macrocyclic faces and the aromatic character of the 1,3,5-triazine faces. Thus, the overall structure is ascribed as a local aromatic species, where the triazine faces exhibit the characteristic shielding cone for aromatic rings. Furthermore, the constructive combination of local shielding cones in C24N24 delivers a related shielding-cone response, as expected for a perfect aromatic cage. Hence, the local aromatic/nonaromatic/antiaromatic sections exhibit an additive or subtractive interaction, leading to a characteristic response inherent to the nature of the spherical cage. We expect that further study of the interplay between different aromatic and antiaromatic faces in fullerene-like cages can deliver interesting pseudo-aromatic or pseudo-antiaromatic spherical species. 相似文献
79.
Di Liu Alvaro D. Sponza Dandan Yang Melanie Chiu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(45):16356-16362
Deterministic methods for tuning polymer dispersity are rare, especially for nonradical polymerizations. Reported here is the first example of photomodulating dispersity in controlled cationic polymerizations of vinyl ethers using carboxy‐functionalized dithienylethene initiators. Reversible photoisomerization of these initiators induces changes in their acidities by up to an order of magnitude. Using the more acidic, ring‐closed isomers as initiators results in polymers with lower dispersities. The degree of light‐induced pKa change in the initiators correlates with the degree of dispersity change in polymers derived from the isomeric initiators. The polymerizations are controlled, and dynamic photoswitching of dispersity during the polymerization reaction was demonstrated. This work provides a framework for photomodulating dispersity in other controlled polymerizations and developing one‐pot block copolymerization reactions in which the dispersities of component blocks can be controlled using light. 相似文献
80.
Diego Mateo Andrea Santiago‐Portillo Josep Albero Sergio Navaln Mercedes Alvaro Hermenegildo García 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(49):18007-18012
Prolonged (weeks) UV/Vis irradiation under Ar of UiO‐66(Zr), UiO66 Zr‐NO2, MIL101 Fe, MIL125 Ti‐NH2, MIL101 Cr and MIL101 Cr(Pt) shows that these MOFs undergo photodecarboxylation of benzenedicarboxylate (BDC) linker in a significant percentage depending on the structure and composition of the material. Routine characterization techniques such as XRD, UV/Vis spectroscopy and TGA fail to detect changes in the material, although porosity and surface area change upon irradiation of powders. In contrast to BCD‐containing MOFs, zeolitic imidazolate ZIF‐8 does not evolve CO2 or any other gas upon irradiation. 相似文献