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91.
Wang X Rodriguez JA Hanson JC Gamarra D Martínez-Arias A Fernández-García M 《The journal of physical chemistry. B》2006,110(1):428-434
New information about the active sites for the water gas shift (WGS) reaction over Cu-CeO2 systems was obtained using in-situ, time-resolved X-ray diffraction (TR-XRD), X-ray absorption spectroscopy (TR-XAS, Cu K and Ce L3 edges), and infrared spectroscopy (DRIFTS). Cu-CeO2 nanoparticles prepared by a novel reversed microemulsion method (doped Ce1-xCuxO2 sample) and an impregnation method (impregnated CuOx/CeO2 sample) were studied. The results from all of the samples indicate that both metallic copper and oxygen vacancies in ceria were involved in the generation of active sites for the WGS reaction. Evidence was found for a synergistic Cu-Ovacancy interaction. This interaction enhances the chemical activity of Cu, and the presence of Cu facilitates the formation of O vacancies in ceria under reaction conditions. Water dissociation occurred on the Ovacancy sites or the Cu-Ovacancy interface. No significant amounts of formate were formed on the catalysts during the WGS reaction. The presence of strongly bound carbonates is an important factor for the deactivation of the catalysts at high temperatures. This work identifies for the first time the active sites for the WGS reaction on Cu-CeO2 catalysts and illustrates the importance of in situ structural studies for heterogeneous catalytic reactions. 相似文献
92.
Susmita Bandyopadhyay Jose R. Peralta-Videa Jose A. Hernandez-Viezcas Milka O. Montes Arturo A. Keller Jorge L. Gardea-Torresdey 《应用光谱学评论》2013,48(3):180-206
Abstract: Currently, thousands of commercially available products contain engineered nanoparticles (ENPs). Because numerous nanoparticles (NPs) are being used in products that will be in contact with water or directly used in water treatment processes, these materials will undoubtedly reside, at least temporarily, in bodies of water. Given the widespread use of NPs and ENPs in consumer goods, a large portion of these materials will soon go into the waste stream, potentially to soil and sediments or added directly to agricultural lands via biosolids. Possible impacts of ENPs on aquatic and terrestrial ecosystems are of great concern. Preliminary data from several research groups have shown that ENPs may have a direct impact on food safety and the food chain. However, our knowledge about detection and characterization of NPs in the environment, especially aquatic environments, is still in its infancy. This review includes the most recent literature about the methods applied to the measurement of NPs and ENPs in the environment. The review covers methods to determine size distribution, shape, structure, surface charge, chemical composition, surface area, agglomeration, surface chemistry, porosity, and solubility. 相似文献
93.
Atushi Ishikawa Shouji Fujimoto Arturo Ramos Takayuki Mizuno 《Entropy (Basel, Switzerland)》2021,23(7)
We analytically derived and confirmed by empirical data the following three relations from the quasi-time-reversal symmetry, Gibrat’s law, and the non-Gibrat’s property observed in the urban population data of France. The first is the relation between the time variation of the power law and the quasi-time-reversal symmetry in the large-scale range of a system that changes quasi-statically. The second is the relation between the time variation of the log-normal distribution and the quasi-time-reversal symmetry in the mid-scale range. The third is the relation among the parameters of log-normal distribution, non-Gibrat’s property, and quasi-time-reversal symmetry. 相似文献
94.
Assuming a beta prior distribution on the fraction defective, $p$ , failure-censored sampling plans for Weibull lifetime models using classical (or average) and Bayesian (or posterior) producer’s and consumer’s risks are designed to determine the acceptability of lots of a given product. The average risk criterion provides a certain assurance that good (bad) lots will be accepted (rejected), whereas the posterior risk criterion provides a determined confidence that an accepted (rejected) lot is indeed good (bad). The performance of classical and Bayesian risks are analyzed in developing sampling plans when the lifetime variable follows the Weibull distribution. Several figures and tables illustrate the sensitivity of the risks and optimal sample sizes for selected censoring levels and specifications according to the available prior information on $p$ . The analysis clarifies the distinction among the different risks for a given sampling plan, and the effect of the prior knowledge on the required sample size. The study shows that, under uncertainty in the prior variance of $p$ , the designs using Bayesian risks are more appropriate. 相似文献
95.
In this article we deal with a multi-dimensional diffusion whose corresponding diffusion vector fields are commutative, and study its joint distribution at the time when a component attains its maximum on finite time interval. Under regularity and ellipticity conditions we shall show the smoothness of this joint distribution. 相似文献
96.
We obtain upper and lower bounds for the density of a functional of a diffusion whose drift is bounded and measurable. The argument consists of using Girsanov’s theorem together with an Itô–Taylor expansion of the change of measure. One then applies Malliavin calculus techniques in a non-trivial manner so as to avoid the irregularity of the drift. An integration by parts formula for this set-up is obtained. 相似文献
97.
Santiago Cabaleiro Rafael Calvo Jesús Castro J. Arturo García-Vázquez Lia M. B. Napolitano Otaciro R. Nascimento Paulo Pérez-Lourido Jaime Romero Antonio Sousa 《Journal of chemical crystallography》2008,38(1):71-75
Abstract The coordination chemistry of the ligand N-thiazol-2-yl-toluenesulfonamidate towards the copper(II) ion has been investigated using an electrochemical synthesis method.
The X-ray structure of this complex was elucidated and is discussed. The compound crystallised in the monoclinic crystal system,
P21/c space group with a = 17.3888(9), b = 16.3003(9), c = 18.3679(9) ? and β = 114.3640(10)°. Four bidentate sulfathiazolato anions bridge two metal centers in a paddle-wheel fashion,
with the nitrogen atoms as donors to give a dimeric species with a Cu···Cu distance of 2.7859(5) ?.
Graphical Abstract The coordination chemistry of the ligand N-thiazol-2-yl-toluenesulfonamidate towards the copper(II) ion has been investigated using an electrochemical synthesis method.
The X-ray structure of the product has been elucidated and is discussed. Sulfathiazolato anions act as bridging ligands to
give a dimeric species with a Cu···Cu distance of 2.7859(5) ?.
相似文献
98.
Arturo Quirantes Francisco J. Olmo Hassan Lyamani Lucas Alados-Arboledas 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(8):1496-1503
Total aerosol scattering and backscattering atmospheric values are typically obtained with an integrating nephelometer. Due to design limitations, measurements do not cover the full (0°–180°) angular range, and correction factors are necessary. The effect of angle cutoff is examined for a number of particle size distributions and refractive indices. Scattering data for sub-micron particles can be corrected by the use of a modified Anderson approximation, while data for larger particle distributions can be approximated by a function of the effective size parameter. Correction factors for the hemispheric backscatter ratio are found to be small if nonsphericity is assumed. Such approximations will help more accurate corrections for angle range, particularly at large size parameter values. 相似文献
99.
A Multifunctional Chemical Probe for the Measurement of Local Micropolarity and Microviscosity in Mitochondria 下载免费PDF全文
Arturo Jiménez‐Sánchez Eric K. Lei Prof. Shana O. Kelley 《Angewandte Chemie (International ed. in English)》2018,57(29):8891-8895
The measurement of physicochemical parameters in living cells can provide information on individual cellular organelles, helping us to understand subcellular function in health and disease. While organelle‐specific chemical probes have allowed qualitative evaluation of microenvironmental variations, the simultaneous quantification of mitochondrial local microviscosity (ηm) and micropolarity (?m), along with concurrent structural variations, has remained an unmet need. Herein, we describe a new multifunctional mitochondrial probe ( MMP ) for simultaneous monitoring of ηm and ?m by fluorescence lifetime and emission intensity recordings, respectively. The MMP enables highly precise measurements of ηm and ?m in the presence of a variety of agents perturbing cellular function, and the observed changes can also be correlated with alterations in mitochondrial network morphology and motility. This strategy represents a promising tool for the analysis of subtle changes in organellar structure. 相似文献
100.
Small molecules that bind and modulate specific protein targets are increasingly used as tools to decipher protein function in a cellular context. Identifying specific small-molecule probes for each protein in the proteome will require miniaturized assays that permit screening of large collections of compounds against large numbers of proteins in a highly parallel fashion. Simple and general binding assays involving small-molecule microarrays can be used to identify probes for nearly any protein in the proteome. The assay may be used to identify ligands for proteins in the absence of knowledge about structure or function. In this tutorial review, we introduce small-molecule microarrays (SMMs) as tools for ligand discovery; discuss methods for manufacturing SMMs, including both non-covalent and covalent attachment strategies; and provide examples of ligand discovery involving SMMs. 相似文献