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191.
A bootstrap procedure useful in latent class, or more general mixture models has been developed to determine the sufficient number of latent classes or components required to account for systematic group differences in the data. The procedure is illustrated in the context of a multidimensional scaling latent class model, CLASCAL. Also presented is a bootstrap technique for determining standard errors for estimates of the stimulus co‐ordinates, parameters of the multidimensional scaling model. Real and artificial data are presented. The bootstrap procedure for selecting a sufficient number of classes seems to correctly select the correct number of latent classes at both low and high error levels. At higher error levels it outperforms Hope's (J. Roy. Statist. Soc. Ser B 1968; 30 : 582) procedure. The bootstrap procedures to estimate parameter stability appear to correctly re‐produce Monte Carlo results. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
192.
Divergent Chemoenzymatic Synthesis of Asymmetrical‐Core‐Fucosylated and Core‐Unmodified N‐Glycans
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Dr. Lin Liu Dr. Shuo Wang Prof. Dr. Kelley W. Moremen Prof. Dr. Geert‐Jan Boons 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(52):18742-18746
A divergent chemoenzymaytic approach for the preparation of core‐fucosylated and core‐unmodified asymmetrical N‐glycans from a common advances precursor is described. An undecasaccharide was synthesized by sequential chemical glycosylations of an orthogonally protected core fucosylated hexasaccharide that is common to all mammalian core fucosylated N‐glycans. Antennae‐selective enzymatic extension of the undecasaccharide using a panel of glycosyl transferases afforded core fucosylated asymmetrical triantennary N‐glycan isomers, which are potential biomarkers for breast cancer. A unique aspect of our approach is that a fucosidase (FucA1) has been identified that selectively can cleave a core‐fucoside without affecting the fucoside of a sialyl LewisX epitope to give easy access to core‐unmodified compounds. 相似文献
193.
Multiple Ionization of Free Ubiquitin Molecular Ions in Extreme Ultraviolet Free‐Electron Laser Pulses
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Dr. Thomas Schlathölter Dr. Geert Reitsma Dmitrii Egorov Dr. Olmo Gonzalez‐Magaña Dr. Sadia Bari Leon Boschman Dr. Erwin Bodewits Dr. Kirsten Schnorr Georg Schmid Dr. Claus Dieter Schröter Dr. Robert Moshammer Prof. Dr. Ronnie Hoekstra 《Angewandte Chemie (International ed. in English)》2016,55(36):10741-10745
The fragmentation of free tenfold protonated ubiquitin in intense 70 femtosecond pulses of 90 eV photons from the FLASH facility was investigated. Mass spectrometric investigation of the fragment cations produced after removal of many electrons revealed fragmentation predominantly into immonium ions and related ions, with yields increasing linearly with intensity. Ionization clearly triggers a localized molecular response that occurs before the excitation energy equilibrates. Consistent with this interpretation, the effect is almost unaffected by the charge state, as fragmentation of sixfold deprotonated ubiquitin leads to a very similar fragmentation pattern. Ubiquitin responds to EUV multiphoton ionization as an ensemble of small peptides. 相似文献
194.
The general one-dimensional equilibrium equations describing the dynamic behaviour of a porous medium form a system of coupled hyperbolic partial differential equations. A transition from the time to the frequency domain is made by spectral decomposition of the displacements. The equations simplify to a set of coupled ordinary differential equations. A solution can be obtained by solving a frequency-dependent eigenvalue problem. The characteristic equation clarifies the double wave-pattern and the attenuation of each wave. A spectrally formulated element uses the frequency-dependent eivenvectors as shape functions. The mass distribution is treated exactly without the need of subdividing a member into smaller elements and therefore wave propagation within an element is also treated exactly. 相似文献
195.
Synthetic Enterobacterial Common Antigen (ECA) for the Development of a Universal Immunotherapy for Drug‐Resistant Enterobacteriaceae
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Dr. Lin Liu Jingying Zha Dr. Antonio DiGiandomenico Dr. Douglas McAllister Dr. C. Kendall Stover Dr. Qun Wang Prof. Geert‐Jan Boons 《Angewandte Chemie (International ed. in English)》2015,54(37):10953-10957
All Enterobacteriaceae express a polysaccharide known as enterobacterial common antigen (ECA), which is an attractive target for the development of universally acting immunotherapies. The first chemical synthesis of ECA‐derived oligosaccharides for the development of such therapies is described. A number of synthetic challenges had to be addressed, including the development of concise synthetic procedures for unusual monosaccharides, the selection of appropriate orthogonal protecting groups, the development of stereoselective glycosylation methods, appropriate timing for the introduction of the carboxylic acid groups on the ManpNAcA moieties, and the selection of appropriate conditions for the reduction of multiple azido moieties. The synthetic compounds were employed to uncover immunodominant moieties of ECA. Furthermore, a monoclonal antibody (mAb) was developed that binds to ECA and can selectively recognize a wide range of Enterobacteriaceae species. 相似文献
196.
Latent class analysis of time series designed to classify and compare sets of series is discussed. For a particular time series in latent class the data are independently normally distributed with a vector of means, and common variance , that is, . The function of time, , can be represented by a linear combination of low-order splines (piecewise polynomials). The probability density function for the data of a time series is posited to be a finite mixture of spherical multivariate normal densities. The maximum-likelihood function is optimized by means of an EM algorithm. The stability of the estimates is investigated using a bootstrap procedure. Examples of real and artificial data are presented. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
197.
198.
Phalet T. Prandolini M.J. Brewer W.D. Dekoster J. De Moor P. Severijns N. Schuurmans P. Turrell B.G. Van Geert A. Vanneste L. Vereecke B. Versyck S. 《Hyperfine Interactions》1999,120(1-8):209-214
Near perpendicular magnetic hyperfine fields in 110mAg have been observed in Fe/Ag multilayers. These fields are studied by low temperature nuclear orientation (LTNO) in multilayers
[Ag(x ML)/Fe(y ML)]20, with (x,y) monolayer (ML) values of (2,10), (3,9), (5,10) and (3,18). The 110mAg γ-ray anisotropy was measured as a function of applied magnetic field parallel to the multilayer. The average induced hyperfine
field of Ag is significantly influenced by the quality of the multilayer as measured by X-ray diffraction.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
199.
Mousa Al‐Tarazi A. Bert M. Heesink Geert F. Versteeg 《Crystal Research and Technology》2005,40(8):735-740
For the precipitation of CuS and ZnS, the effects of the reactor/precipitator type, mass transfer and process conditions on crystal morphology were studied. Either H2S gas or a S2– solution were applied. Three different types of reactors have been tested, namely a laminar jet, a bubble column and an MSMPR reactor. The choice of reactor type as well as mass transfer and metal concentration all have a considerable influence on the morphology of the produced crystals. A well mixed bubble column with H2S containing gas as feed yields the coarsest crystals. Use is then made of the surface active properties of CuS‐particles, which induce agglomeration at the gas‐liquid interface, where as the low metal concentrations inside the reactor also contribute to the formation of coarser particles (especially for ZnS). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
200.
A solution procedure is presented to compute free field vibrations induced by train or road traffic, the excitation being either deterministic or stochastic. The full interaction between the vehicle, the track or road and the soil is accounted for, using a substructure approach that takes advantage of the fact that the properties of the track or road and the soil do not change along the longitudinal direction. A time-frequency approach is proposed to characterize the free field radiated in the soil. The examples show the importance of guided waves along the track for understanding the dynamic behavior of the track or the road. 相似文献