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421.
Formation of a Dimer of Trinuclear Helicates which Encapsulates an Array of Six Hydrogen‐Bonded Anions 下载免费PDF全文
Robert A. Faulkner Dr. Lindsay P. Harding Joshua Higginson Prof. Craig R. Rice Christopher Slater 《Angewandte Chemie (International ed. in English)》2014,53(49):13540-13543
The amine‐containing ligand L, composed of two bidentate pyridyl‐thiazole moieties linked by a 1,3‐diaminophenylene unit, reacts with copper(II) ions to form a dinuclear double helicate [Cu2L2]4+. Reaction of [Cu2L2]4+ with dihydrogen phosphate (0.5 equivalents) gives the unsaturated dinuclear double helicate [Cu2L2(OPO3H2)]3+. [Cu2L2(OPO3H2)]3+ further reacts with another 0.5 equivalents of dihydrogen phosphate to give a trinuclear circular helicate which then self‐assembles into a hexameric cluster [{Cu3L3(OPO3H2)3}]26+. 相似文献
422.
Anna F. Oliveri Lindsay A. Wills Caitlyn R. Hazlett Matthew E. Carnes I-Ya Chang Paul Ha-Yeon Cheong Darren W. Johnson 《Chemical science》2015,6(7):4071-4085
NMR spectroscopy is the go-to technique for determining the solution structures of organic, organometallic, and even macromolecular species. However, structure determination of nanoscale aqueous inorganic clusters by NMR spectroscopy remains an unexplored territory. The few hydroxo-bridged inorganic species well characterized by 1H Nuclear Magnetic Resonance spectroscopy (1H-NMR) do not provide enough information for signal assignment and prediction of new samples. 1H-NMR and quantum mechanical (QM) computations were used to characterize the NMR spectra of the entire array of inorganic flat-Ga13–xInx (0 ≤ x ≤ 6) nanoscale clusters in solution. A brief review of the known signals for μ2-OH and μ3-OH bridges gives expected ranges for certain types of protons, but does not give enough information for exact peak assignment. Integration values and NOESY data were used to assign the peaks of several cluster species with simple 1H-NMR spectra. Computations agree with these hydroxide signal assignments and allow for assignment of the complex spectra arising from the remaining cluster species. This work shows that 1H-NMR spectroscopy provides a variety of information about the solution behavior of inorganic species previously thought to be inaccessible by NMR due to fast ligand and/or proton exchange in wet solvents. 相似文献
423.
Abstract Brillouin scattering has been used to study methanol as a function of pressure up to 8.4 GPa. Our near-forward-scattering experiments yield the pressure dependence of the velocity of longitudinal acoustic (LA) phonons, while we determine the pressure dependence of the product of the index of refraction and the LA phonon velocity from our backscattering experiments. The pressure dependence of the LA phonon lifetimes is obtained from the linewidth of the measured Brillouin peaks. From our backscattering experiments we find that the normalized phonon attenuation is a decreasing function of pressure. 相似文献
424.
425.
Kevin Colizza Alexander Yevdokimov Lindsay McLennan James L. Smith Jimmie C. Oxley 《Journal of the American Society for Mass Spectrometry》2018,29(2):393-404
Over the last several decades, mass spectrometry has become one of the principle methods for compound identification and quantification. While for analytical purposes, fragments which are not fully characterized in terms of origin and intensity as a function of experimental conditions have been used, understanding the nature of those species is very important. Herein we discuss such issues relative to triacetone triperoxide (TATP) and its frequently observed fragment at m/z 89. This “fragment” has been identified as the gas-phase reaction product of TATP with one or two methanol molecules/ions. Additionally, the origin and conditions of other fragments at m/z 91, 75, and 74 associated with TATP will be addressed. Similar analytical issues associated with other multi-peroxide organic compounds [hexamethylene triperoxide diamine (HMTD), methyl ethyl ketone peroxides (MEKP)] will also be discussed. Solution storage conditions for TATP, HMTD, and tetramethylene diperoxide diamine dialdehyde have been determined. 相似文献
426.
Susan Wei Chihoon Lee Lindsay Wichers J. S. Marron 《Journal of computational and graphical statistics》2016,25(2):549-569
High-dimensional low sample size (HDLSS) data are becoming increasingly common in statistical applications. When the data can be partitioned into two classes, a basic task is to construct a classifier that can assign objects to the correct class. Binary linear classifiers have been shown to be especially useful in HDLSS settings and preferable to more complicated classifiers because of their ease of interpretability. We propose a computational tool called direction-projection-permutation (DiProPerm), which rigorously assesses whether a binary linear classifier is detecting statistically significant differences between two high-dimensional distributions. The basic idea behind DiProPerm involves working directly with the one-dimensional projections of the data induced by binary linear classifier. Theoretical properties of DiProPerm are studied under the HDLSS asymptotic regime whereby dimension diverges to infinity while sample size remains fixed. We show that certain variations of DiProPerm are consistent and that consistency is a nontrivial property of tests in the HDLSS asymptotic regime. The practical utility of DiProPerm is demonstrated on HDLSS gene expression microarray datasets. Finally, an empirical power study is conducted comparing DiProPerm to several alternative two-sample HDLSS tests to understand the advantages and disadvantages of each method. 相似文献
427.
P. L. Masiteng A. A. Pasternak E. A. Lawrie O. Shirinda J. J. Lawrie R. A. Bark S. P. Bvumbi N. Y. Kheswa R. Lindsay E. O. Lieder R. M. Lieder T. E. Madiba S. M. Mullins S. H. T. Murray J. Ndayishimye S. S. Ntshangase P. Papka J. F. Sharpey-Schafer 《The European Physical Journal A - Hadrons and Nuclei》2016,52(2):28
428.
Dr. Lindsay R. Merte Dr. Christopher J. Heard Dr. Feng Zhang Dr. Juhee Choi Mikhail Shipilin Dr. Johan Gustafson Prof. Jason F. Weaver Prof. Henrik Grönbeck Prof. Edvin Lundgren 《Angewandte Chemie (International ed. in English)》2016,55(32):9267-9271
Ultrathin metal oxides exhibit unique chemical properties and show promise for applications in heterogeneous catalysis. Monolayer FeO films supported on metal surfaces show large differences in reactivity depending on the metal substrate, potentially enabling tuning of the catalytic properties of these materials. Nitric oxide (NO) adsorption is facile on silver‐supported FeO, whereas a similar film grown on platinum is inert to NO under similar conditions. Ab initio calculations link this substrate‐dependent behavior to steric hindrance caused by substrate‐induced rumpling of the FeO surface, which is stronger for the platinum‐supported film. Calculations show that the size of the activation barrier to adsorption caused by the rumpling is dictated by the strength of the metal–oxide interaction, offering a straightforward method for tailoring the adsorption properties of ultrathin films. 相似文献
429.
Rabideau BD Pell LE Bonnecaze RT Korgel BA 《Langmuir : the ACS journal of surfaces and colloids》2007,23(3):1270-1274
Polydisperse amorphous-silicon colloidal particles ranging from approximately 10 to 140 nm in diameter were evaporated onto carbon substrates. The particles formed close-packed monolayers in which each particle had 6-fold nearest-neighbor coordination characteristic of a hexagonal lattice yet completely lacked positional order. Orientational correlation functions were calculated for the particles and found to be constant throughout the aggregate, indicating the occurrence of long-range orientational order. Computer simulations revealed that the structural organization in this system resulted from capillary immersion forces that lead to a size separation as the particles deposit from the evaporating solvent onto the substrate. 相似文献
430.
Mittag T Christensen KL Lindsay KB Nielsen NC Skrydstrup T 《The Journal of organic chemistry》2008,73(3):1088-1092
In this work, a new method for the preparation of peptidyl ketones is presented employing a SmI(2)/H(2)O-mediated coupling of N-peptidyl oxazolidinones with electron-deficient alkenes. The requisite peptide imides were easily prepared by solution-phase peptide synthesis starting from an N-acyl oxazolidinone derivative of an amino acid. Importantly, they could be used directly in the C-C bond-forming step without the need for further functionalization. Coupling of these peptide derivatives with a second peptide possessing an N-terminal acryloyl group leads to ketomethylene isosteres of glycine-containing peptides. This method represents an alternative means for ligating two small peptides through a C-C bond-forming step. 相似文献