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91.
Irradiation of substituted 2-benzylidenecyclopentanone O-alkyl and O-acetyloximes in methanol provides a convenient synthesis of alkyl, alkoxy, hydroxy, acetoxy, amino, dimethylamino and benzo substituted annulated quinolines. para-Substituents yield 6-substituted-2,3-dihydro-1H-cyclopenta[b]quinolines with 8-substituted products being obtained from ortho-substituted starting materials. Reactions of meta-substituted precursors are highly regioselective, with alkyl substituents leading to 5-substituted 2,3-dihydro-1H-cyclopenta[b]quinolines and more strongly electron-donating substituents generally resulting in 7-substituted products. 2-Furylmethylene and 2-thienylmethylene analogues yield annulated furo- and thieno-[2,3e]pyridines respectively. Sequential E- to Z-benzylidene group isomerisation and six pi-electron cyclisation steps result in formation of a short-lived dihydroquinoline intermediate which spontaneously aromatises by elimination of an alcohol or acetic acid. For 2-benzylidenecyclopentanone O-allyloxime, singlet excited states are involved in both steps. 相似文献
92.
93.
Austen Curtin Christine Austin Alessandro Giuliani Manuel Ruiz Marín Francheska Merced-Nieves Martha M. Tllez-Rojo Robert O. Wright Manish Arora Paul Curtin 《Entropy (Basel, Switzerland)》2021,23(12)
Metabolism and physiology frequently follow non-linear rhythmic patterns which are reflected in concepts of homeostasis and circadian rhythms, yet few biomarkers are studied as dynamical systems. For instance, healthy human development depends on the assimilation and metabolism of essential elements, often accompanied by exposures to non-essential elements which may be toxic. In this study, we applied laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to reconstruct longitudinal exposure profiles of essential and non-essential elements throughout prenatal and early post-natal development. We applied cross-recurrence quantification analysis (CRQA) to characterize dynamics involved in elemental integration, and to construct a graph-theory based analysis of elemental metabolism. Our findings show how exposure to lead, a well-characterized toxicant, perturbs the metabolism of essential elements. In particular, our findings indicate that high levels of lead exposure dysregulate global aspects of metabolic network connectivity. For example, the magnitude of each element’s degree was increased in children exposed to high lead levels. Similarly, high lead exposure yielded discrete effects on specific essential elements, particularly zinc and magnesium, which showed reduced network metrics compared to other elements. In sum, this approach presents a new, systems-based perspective on the dynamics involved in elemental metabolism during critical periods of human development. 相似文献
94.
A combination of two-dimensional nuclear magnetic resonance (NMR) proton relaxometry and differential interference contrast
optical microscopy is used to compare the pore structures of hydroxyethyl methacrylate-based hydrogels used in conventional
contact lenses with three silicone hydrogels primarily developed for continuous-wear contact lenses. It is shown that both
types of hydrogel have a connected network of nanopores but that, in addition, the silicone hydrogels contain pores on the
micrometer scale that enhances their permeability. The potential of other two-dimensional NMR relaxation and diffusion methods
for detailed characterization of hydrogels is discussed. 相似文献
95.
Zhen-Dan Shi Omid Motabar Ehud Goldin Ke Liu Noel Southall Ellen Sidransky Christopher P. Austin Gary L. Griffiths Wei Zheng 《Analytical and bioanalytical chemistry》2009,394(7):1903-1909
Alpha-galactosidase A hydrolyzes the terminal alpha-galactosyl moieties from glycolipids and glycoproteins in lysosomes. Mutations
in α-galactosidase cause lysosomal accumulation of the glycosphingolipid, globotriaosylceramide, which leads to Fabry disease.
Small-molecule chaperones that bind to mutant enzyme proteins and correct their misfolding and mistrafficking have emerged
as a potential therapy for Fabry disease. We have synthesized a red fluorogenic substrate, resorufinyl α-d-galactopyranoside, for a new α-galactosidase enzyme assay. This assay can be measured continuously at lower pH values, without
the addition of a stop solution, due to the relatively low pK
a of resorufin (~6). In addition, the assay emits red fluorescence, which can significantly reduce interferences due to compound
fluorescence and dust/lint as compared to blue fluorescence. Therefore, this new red fluorogenic substrate and the resulting
enzyme assay can be used in high-throughput screening to identify small-molecule chaperones for Fabry disease.
Zhen-Dan Shi and Omid Motabar contributed equally to this work 相似文献
96.
Austin Nevin Daniela Comelli Iacopo Osticioli Lucia Toniolo Gianluca Valentini Rinaldo Cubeddu 《Analytical and bioanalytical chemistry》2009,395(7):2139-2149
The assessment of the influence of natural and artificial ageing on the spectrofluorescence of triterpenoid varnishes dammar
and mastic is the focus of this work. Both Fourier transform infrared (FTIR) microscopy using attenuated total reflectance
and Raman spectroscopy have been employed for complementary molecular analysis of samples. Synchronous fluorescence spectroscopy,
excitation emission spectroscopy, and statistical analysis of data have been used to monitor changes in the optical properties
of varnish samples. Assessment of naturally and artificially aged samples using excitation emission spectroscopy suggests
that extensive exposure to visible light does not lead to easily appreciable differences in the fluorescence of mastic and
dammar; cluster analysis has been used to assess changes, which occur with artificial ageing under visible light, indicating
that differences in the fluorescence spectra of aged triterpenoids may be insufficient for their discrimination. The results
highlight significant differences between the initial fluorescence of films of dammar and mastic and the fluorescence, which
develops with ageing and oxidation, and specific markers, which change with ageing in FTIR and Raman spectra, have been identified. 相似文献
97.
98.
The Baeyer-Villiger reactions of acetone and 3-pentanone, including their fluorinated and chlorinated derivatives, with performic acid have been studied by ab initio and DFT calculations. Results are compared with experimental findings for the Baeyer-Villiger oxidation of aliphatic fluoro and chloroketones. According to theoretical results, the first transition state is rate-determining for all substrates even in the presence of acid catalyst. Although the introduction of acid into the reaction pathway leads to a dramatic decrease in the activation energy for the first transition state (TS), once entropy is included in the calculations, the enthalpic gain is lost. Of all substrates examined, pentanone reacts with performic acid via the lowest energy transition state. The second transition state is also lowest for pentanone, illustrating the accelerating effect of the additional alkyl group. Interestingly, there is only a small energetic difference in the transition states leading to migration of the fluorinated substituent versus the alkyl substituent in fluoropentanone and fluoroacetone. These differences match remarkably well with the experimentally obtained ratios of oxidation at the fluorinated and nonfluorinated carbons in a series of aliphatic ketones (calculated, 0.3 kcal/mol, observed, 0.5 kcal/mol), which are reported herein. The migration of the chlorinated substituent is significantly more difficult than that of the alkyl, with a difference in the second transition state of approximately 2.6 kcal/mol. 相似文献
99.
100.