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81.
The chiral separation of halogenated amino acids by ligand-exchange CE is described. Halogenated amino acids attracted increasing interest in recent years because of their physiological activities. Different chiral selectors, as there are L-4-hydroxyproline, L-histidine, and N-alkyl derivatives of L-4-hydroxyproline in form of their copper(II) complexes, are compared for their chiral recognition ability for halogenated amino acids. The influence of various parameters, such as selector concentration, pH, organic modifier, and field strength, on the resolution was investigated. All halogenated amino acids investigated were baseline-separated under optimized conditions. 相似文献
82.
Michael Lawrence Hadley Wickham Dianne Cook Heike Hofmann Deborah F. Swayne 《Computational Statistics》2009,24(2):195-205
This paper describes progress towards developing a platform for rapid prototyping of interactive data visualizations, using
R, GGobi, rggobi and RGtk2. GGobi is a software tool for multivariate interactive graphics. At the core of GGobi is a data
pipeline that incrementally transforms data through a series of stages into a plot and maps user interaction with the plot
back to the data. The GGobi pipeline is extensible and mutable at runtime. The rggobi package, an interface from the R language
to GGobi, has been augmented with a low-level interface that supports the customization of interactive data visualizations
through the extension and manipulation of the GGobi pipeline. The large size of the GGobi API has motivated the use of the
RGtk2 code generation system to create the low-level interface between R and GGobi. The software is demonstrated through an
application to interactive network visualization. 相似文献
83.
A pH‐sensitive detector for flow‐through potentiometry based on a graphite/quinhydrone/silicone composite electrode was applied to determine calcium and magnesium in aqueous solutions. The determinations are performed by FIA titrations with EDTA as the carrier solution. The method was applied to the analysis of mineral water, drinking water, and river water. The results were compared with those obtained by batch complexometric titration. The proposed new method is suitable for the simple, rapid and automated determination of water hardness in small sample volumes of aqueous solutions. The detection limit for both ions is about 1×10?5 mol L?1, the standard deviation is less than 2%. The sampling frequency is 60 determinations per hour. 相似文献
84.
Sayed M. Saleh Rainer Müller Heike S. Mader Axel Duerkop Otto S. Wolfbeis 《Analytical and bioanalytical chemistry》2010,398(4):1615-1623
Fluorescent silica nanoparticles (SiNPs) were prepared by covalent attachment of fluorophores to the amino-modified surface
of SiNPs with a typical diameter of 15 nm. The SiNPs are intended for use in novel kinds of fluorescence resonance energy
transfer (FRET)-based affinity assays at the interface between nanoparticle and sample solution. Various labels were employed
to obtain a complete set of colored SiNPs, with excitation maxima ranging from 337 to 659 nm and emission maxima ranging from
436 nm to the near infrared (710 nm). The nanoparticles were characterized in terms of size and composition using transmission
electron microscopy, thermogravimetry, elemental analysis, and dynamic light scattering. The surface of the fluorescent SiNPs
was biotinylated, and binding of labeled avidin to the surface was studied via FRET in two model cases. In the first, FRET
occurs from the biotinylated fluorescent SiNP (the donor) to the labeled avidin (the acceptor). In the second, FRET occurs
in the other direction. Aside from its use in the biotin–avidin system, such SiNPs also are believed to be generally useful
fluorescent markers in various kinds of FRET assays, not the least because the fluorophore is located on the surface of the
SiNPs (and thus always much closer to the second fluorophore) rather than being doped deep in its interior. 相似文献
85.
Bhandary S Ghosh S Herper H Wende H Eriksson O Sanyal B 《Physical review letters》2011,107(25):257202
One of the primary objectives in molecular nanospintronics is to manipulate the spin states of organic molecules with a d-electron center, by suitable external means. In this Letter, we demonstrate by first principles density functional calculations, as well as second order perturbation theory, that a strain induced change of the spin state, from S=1→S=2, takes place for an iron porphyrin (FeP) molecule deposited at a divacancy site in a graphene lattice. The process is reversible in the sense that the application of tensile or compressive strains in the graphene lattice can stabilize FeP in different spin states, each with a unique saturation moment and easy axis orientation. The effect is brought about by a change in Fe-N bond length in FeP, which influences the molecular level diagram as well as the interaction between the C atoms of the graphene layer and the molecular orbitals of FeP. 相似文献
86.
Recently developed continuum phase field models for brittle fracture show excellent modeling capability in situations with complex crack topologies including branching in the small and large strain applications. This work presents a generalization towards fully coupled multi-physics problems at large strains. A modular concept is outlined for the linking of the diffusive crack modeling with complex multi field material response, where the focus is put on the model problem of finite thermo-elasticity. This concerns a generalization of crack driving forces from the energetic definitions towards stress-based criteria, the constitutive modeling of degradation of non-mechanical fluxes on generated crack faces. Particular assumptions are made on the generation of convective heat exchanges approximating surface load integrals of the sharp crack approach by distinct volume integrals. The coupling effect is also shown in generation of cracks due to thermally induced stress states. We finally demonstrate the performance of the phase field formulation of fracture at large strains by means of representative numerical examples. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
87.
Tian Tian Mengling Liu Yinhui Li Jian Han Liang Ren Heike Lorenz Qing Wu Jianxin Chen 《Particuology》2022,(3):88-97
Textile wastewater contains highly toxic,nondegradable,carcinogenic organic pollutants,causing severe damage to the ecological environment.In this work,β-cyclod... 相似文献
88.
Heike Mildenberger 《Archive for Mathematical Logic》2001,40(2):93-112
We show that the Filter Dichotomy Principle implies that there are exactly four classes of ideals in the set of increasing functions from the natural numbers. We thus answer two open questions on consequences of ? < ?. We show that ? < ? implies that ? = ?, and that Filter Dichotomy together with ? < ? implies ? < ?. The technical means is the investigation of groupwise dense sets, ideals, filters and ultrafilters. With related techniques we prove the new inequality ?≤ cf(?). Received: 9 October 1998 / Revised version: 18 August 1999 / Published online: 21 December 2000 相似文献
89.
This paper deals with the use of Cu(II) complexes of L-tartaric acid or L-threonine as selectors for the chiral separation of drugs containing amino alcohol structure by ligand-exchange CE. Using Cu(II) ions as a complexing agent, a series of sympathomimetics and beta-blockers were resolved. It was found that the resolution strongly depends on selector concentration and pH. The optimum pH for complexation was 12. 相似文献
90.
Thiobromo Complexes of Arsenic and Antimony. Preparation and Crystal Structures of (PPh4)2[As2SBr6] · CH2Br2 and (PPh4)2[Sb2SBr6] · CH2Br2 (PPh4)2[As2SBr6] · CH2Br2 is formed by the reaction of As2S3, PPh4I and HI in dibromomethane. It can also be obtained, as well as (PPh4)2[Sb2SBr6] · CH2Br2, from (PPh4)2[As2Br8] and (PPh4)3[Sb2Br9], respectively, with bistrimethylsilylsulfide. The crystal structures of the title compounds were determined by X-ray diffraction. They are isotypic with (PPh4)2[As2SCl6] · C2H4Cl2. In the anions [M2SBr6]2? the M atoms (As or Sb) have a distorted octahedral coordination, the two octahedra share acommon face with one bridging S and two Br atoms; the lone electron pairs occupy the trans positions to the S atom. Crystal data: triclinic, space group P1 , Z = 2; (PPh4)2[As2SBr6] · CH2Br2, a = 119.1, b = 1203.6, c = 2067.5 pm α= 94.89, β = 97.78, γ = 112.20°, 3046 independent observed reflexions, R = 0.083; (PPh4)2[Sb2SBr6] · CH2Br2, a = 1198.9, b = 1224.3, c = 2085.5pm, α = 95.04, β = 98.48, γ = 112.13°C, 2380 reflexions, R = 0.079. 相似文献