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151.
Kwon BJ Perry TT Wilhelm CL Healy EW 《The Journal of the Acoustical Society of America》2012,131(4):3111-3119
Normal-hearing (NH) listeners maintain robust speech understanding in modulated noise by "glimpsing" portions of speech from a partially masked waveform--a phenomenon known as masking release (MR). Cochlear implant (CI) users, however, generally lack such resiliency. In previous studies, temporal masking of speech by noise occurred randomly, obscuring to what degree MR is attributable to the temporal overlap of speech and masker. In the present study, masker conditions were constructed to either promote (+MR) or suppress (-MR) masking release by controlling the degree of temporal overlap. Sentence recognition was measured in 14 CI subjects and 22 young-adult NH subjects. Normal-hearing subjects showed large amounts of masking release in the +MR condition and a marked difference between +MR and -MR conditions. In contrast, CI subjects demonstrated less effect of MR overall, and some displayed modulation interference as reflected by poorer performance in modulated maskers. These results suggest that the poor performance of typical CI users in noise might be accounted for by factors that extend beyond peripheral masking, such as reduced segmental boundaries between syllables or words. Encouragingly, the best CI users tested here could take advantage of masker fluctuations to better segregate the speech from the background. 相似文献
152.
Chris D. Geddes Peter Douglas Christopher P. Moore Trevor J. Wear Peter L. Egerton 《Journal of fluorescence》1999,9(3):163-171
Fourteen thin-film optical sensors in which halide-sensitive fluorophores are immobilized in a thin copolymer film (50 m, dry) have been developed and characterized. The sensor films use rhodamine, 6-methoxyquinoline, and harmane dyes which have been functionalized and bound to a hydrophilic copolymer. The sensor films are reversibly capable of determining aqueous bromide and iodide with 4 and 2% accuracy, respectively, at concentrations of around 10–3 mol dm–3, and are more sensitive than previous plastic sensor fabrications. The 90% response time to molar iodide is 30–60 s. A combination of sensor films allows the simultaneous determination of both I– and Br– in a mixed-halide solution. The interference of several ions, including pseudo-halides, on the sensor films has been studied. 相似文献
153.
Trevor A. Hamlin Israel Fernndez F. Matthias Bickelhaupt 《Angewandte Chemie (International ed. in English)》2019,58(26):8922-8926
We have quantum chemically analyzed the catalytic effect of dihalogen molecules (X2=F2, Cl2, Br2, and I2) on the aza‐Michael addition of pyrrolidine and methyl acrylate using relativistic density functional theory and coupled‐cluster theory. Our state‐of‐the‐art computations reveal that activation barriers systematically decrease as one goes to heavier dihalogens, from 9.4 kcal mol?1 for F2 to 5.7 kcal mol?1 for I2. Activation strain and bonding analyses identify an unexpected physical factor that controls the computed reactivity trends, namely, Pauli repulsion between the nucleophile and Michael acceptor. Thus, dihalogens do not accelerate Michael additions by the commonly accepted mechanism of an enhanced donor–acceptor [HOMO(nucleophile)–LUMO(Michael acceptor)] interaction, but instead through a diminished Pauli repulsion between the lone‐pair of the nucleophile and the Michael acceptor's π‐electron system. 相似文献
154.
Dr. Francesco Zaccaria Dr. Stephanie C. C. van der Lubbe Celine Nieuwland Dr. Trevor A. Hamlin Prof. Dr. Célia Fonseca Guerra 《Chemphyschem》2021,22(22):2286-2296
The formation of guanine quadruplexes (GQ) in DNA is crucial in telomere homeostasis and regulation of gene expression. Pollution metals can interfere with these DNA superstructures upon coordination. In this work, we study the affinity of the internal GQ channel site towards alkaline earth metal (Mg2+, Ca2+, Sr2+, and Ba2+), and (post-)transition metal (Zn2+, Cd2+, Hg2+, and Pb2+) cations using density functional theory computations. We find that divalent cations generally bind to the GQ cavity with a higher affinity than conventional monovalent cations (e. g. K+). Importantly, we establish the nature of the cation-GQ interaction and highlight the relationship between ionic and nuclear charge, and the electrostatic and covalent interactions. The covalent interaction strength plays an important role in the cation affinity and can be traced back to the relative stabilization of cations’ unoccupied atomic orbitals. Overall, our findings contribute to a deeper understanding of how pollution metals could induce genomic instability. 相似文献
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157.
The volatile intermediate Et3NBH3 was isolated during the thermolysis of Et4NBH4 at 185°C for 16 hr under dynamic vacuum. The rate of decomposition of Et4NBH4 was studied. Separate thermolyses of Et4NBH4 (or Et3NBH3) with closo B9H92?nido B9H?12, or arachno B9H14? did not produce B10H102? as the major product. These results are inconsistent with the “build-up” mechanism previously proposed for the thermolytic convertion of BH 4? to B10H102? and a new mechanism is required. 相似文献
158.
Paul W.C CrossGeorge J Ellames Jennifer S GibsonJohn M Herbert William J KerrAlan H McNeill Trevor W Mathers 《Tetrahedron》2003,59(18):3349-3358
A series of iridium-based complexes formed in situ, containing pyridine, phosphines, triphenylarsine, triphenylstibine, and triphenylamine as ligands, has been screened for ability to mediate ortho-exchange of hydrogen in a series of model substrates. Improved incorporation into a number of substrate classes has been achieved. The electronic properties and number of ligands at the metal centre are instrumental in determining which catalysts are best suited to exchange in any given substrate. 相似文献
159.