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491.
U. Röpke H. Bartelt S. Unger K. Schuster J. Kobelke 《Applied physics. B, Lasers and optics》2011,104(3):481-486
Optical waveguide arrays consisting of a two-dimensional arrangement of weakly coupled waveguides represent the basis of the
new research field of discrete optics. For studying the nonlinear pulse dynamics, fiber waveguide arrays offer specific advantages
such as a high optical damage threshold and an accessible range of anomalous dispersion. Coherent coupling of such waveguides
for reasonable propagation lengths requires, however, a high structural quality of the waveguides and their superstructure,
which is beyond conventional fiber technology. Design, fabrication and characterization of such a fiber waveguide array are
described. The linear propagation properties in such a system are modeled and compared with experimental measurements. The
high structural homogeneity and good optical quality of the arrays as well as the limits of the nearest-neighbor approximation
are demonstrated. 相似文献
492.
Min H Girard-Lauriault PL Gross T Lippitz A Dietrich P Unger WE 《Analytical and bioanalytical chemistry》2012,403(2):613-623
We investigated the ageing of amine-terminated self-assembled monolayers (amine-SAMs) on different silica substrates due to exposure to different ambient gases, pressures, and/or temperatures using time-of-flight secondary ion mass spectrometry (ToF-SIMS) with principal component analysis and complementary methods of surface analysis as X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS). The goal of this study is to examine the durability of primary amine groups of amine-SAMs stored in a user laboratory prior to being used as supports for biomolecule immobilization and other applications. We prepared amine-SAMs on the native oxides of silicon wafers and glass slides using 3-aminopropyl triethoxysilane, by using optimized conditions such as anhydrous organic solvent and reaction time scale of hours to avoid multilayer growth. Selected commercial amine-SAM slides have been investigated, too. When the amine-SAMs are exposed to air, oxygen incorporation occurs, followed by formation of amide groups. The formation of oxygen species due to ageing was proved by ToF-SIMS, XPS, and NEXAFS findings such as CNO(-) secondary ion emission at m/z 42, observation of the N 1s HNC=O component peak at 400.2-400.3 eV in XPS, and, last but not least, by formation of a π*(HNC=O) resonance at 401 eV in the N K-edge X-ray absorption spectrum. It is concluded that the used multi-method approach comprising complementary ToF-SIMS, XPS, and NEXAFS analyses is well suited for a thorough study of chemical aspects of ageing phenomena of amine-SAM surfaces. 相似文献
493.
K. J. Kim W. E. S. Unger J. W. Kim D. W. Moon T. Gross V.‐D. Hodoroaba D. Schmidt T. Wirth W. Jordaan M. van Staden S. Prins L. Zhang T. Fujimoto X. P. Song H. Wang 《Surface and interface analysis : SIA》2012,44(2):192-199
An international interlaboratory comparison of the measurement capabilities of four National Metrology Institutes (NMIs) and one Designated Institute (DI) in the determination of the chemical composition of thin Fe‐Ni alloy films was conducted via a key comparison (K‐67) of the Surface Analysis Working Group of the Consultative Committee for Amount of Substance. This comparison was made using XPS (four laboratories) and AES (one laboratory) measurements. The uncertainty budget of the measured chemical composition of a thin alloy film was dominated by the uncertainty of the certified composition of a reference specimen which had been determined by inductively coupled plasma mass spectrometry using the isotope dilution method. Pilot study P‐98 showed that the quantification using relative sensitivity factors (RSFs) of Fe and Ni derived from an alloy reference sample results in much more accurate result in comparison to an approach using RSFs derived from pure Fe and Ni films. The individual expanded uncertainties of the participants in the K‐67 comparison were found to be between 2.88 and 3.40 atomic %. The uncertainty of the key comparison reference value (KCRV) calculated from individual standard deviations and a coverage factor (k) of 2 was 1.23 atomic %. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
494.
Miriam Unger Harumi Sato Yukihiro Ozaki Heinz W. Siesler 《Macromolecular Symposia》2011,305(1):90-100
Variable-temperature FT-IR spectra of poly(3-hydroxybutyrate) (PHB), poly(ε-caprolactone) (PCL) and a PHB/PCL (50:50 wt.%) blend were analyzed by two-dimensional correlation spectroscopy (2DCOS). For this purpose the ν(CO) region was employed to characterize in some detail the crystallization behavior of the investigated polymer systems during cooling from the melt. The asynchronous 2D correlation spectra clearly captured the existence of three components in the crystallinity-sensitive region of the CO stretching mode for PHB and PCL, respectively: a well-ordered, an inter-mediate and a less ordered crystalline state. Furthermore, by 2DCOS application a sequential order of the observed structural changes could be proposed for the whole temperature range during the crystallization of both polymers. In the case of the PHB/PCL (50:50 wt.%) polymer blend, we have split up the spectral data set in the sub-sets between 200–120 °C and 70–30 °C for a more detailed 2DCOS analysis. In this way we could separate the crystallization process of PHB and PCL in the polymer blend. 相似文献
495.
The solution of eigenvalue problems for partial differential operators by using boundary integral equation methods usually
involves some Newton potentials which may be resolved by using a multiple reciprocity approach. Here we propose an alternative
approach which is in some sense equivalent to the above. Instead of a linear eigenvalue problem for the partial differential
operator we consider a nonlinear eigenvalue problem for an associated boundary integral operator. This nonlinear eigenvalue
problem can be solved by using some appropriate iterative scheme, here we will consider a Newton scheme. We will discuss the
convergence and the boundary element discretization of this algorithm, and give some numerical results. 相似文献
496.
A nonlinear eigenvalue problem arising from a coupled finite element/boundary element approach for fluid-structure interaction is considered. We propose an approach based on polynomial interpolation and linearization for its numerical solution. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
497.
Y. Kagamitani T. Kuribayashi K. Hazu T. Onuma D. Tomida R. Simura S.F. Chichibu K. Sugiyama C. Yokoyama T. Ishiguro T. Fukuda 《Journal of Crystal Growth》2010,312(22):3384-3387
Purely wurtzite phase needle crystals and epitaxial layers of GaN were grown by the ammonothermal method using an NH4I mineralizer. The inclusion of zincblende phase GaN was effectively eliminated by increasing the growth temperature higher than 500 °C. Accordingly, an approximately 20-μm-thick GaN epitaxial layer was achieved on the Ga-polar face of a c-plane GaN seed wafer at 520 °C. Although the characteristic deep state emission band dominated the room temperature photoluminescence spectrum, the near-band-edge emission of GaN was observed for both the needle crystals and the epitaxial layers. These results encourage one to grow better quality GaN crystals at a high growth rate under high-temperature growth conditions. 相似文献
498.
Fiber based high repetition rate, high energy laser source applying chirped pulse amplification 总被引:4,自引:0,他引:4
D. Nickel A. Liem J. Limpert H. Zellmer U. Griebner S. Unger G. Korn A. Tünnermann 《Optics Communications》2001,190(1-6):309-315
We demonstrate the potential of a high-gain Yb-fiber amplifier system to provide ultrashort pulses with high energies. 100 μJ pulses generated at a repetition rate of 32 kHz exhibit nearly diffraction limited output (M2≈1.7) at a 1060 nm center wavelength. Using chirped pulse amplification, temporally streched laser pulses from a femtosecond oscillator could be compressed after amplification to subpicosecond pulse duration. The achievable intensities are high enough to create plasmas which can efficiently convert laser light to the extreme ultraviolet radiation. In a multimode Yb-doped fiber amplifier we obtained average powers of up to 22 W and single pulse energies up to 130 μJ. 相似文献
499.
Peter Fulde Patrick Unger Jun-Ichi Igarashi 《International journal of quantum chemistry》1997,63(3):645-653
Until now, solids with strongly correlated electrons can be treated only by model Hamiltonians. Even then a calculation of spectral densities is not simple, because the strong Coulomb interactions prevent us from treating correlations perturbatively. We show that projection and partitioning techniques are a very valuable tool here. The method is applied to computations of the density of states of transition metals, in particular, Ni. Here, the band narrowing and the sattlite peak at 6 eV due to correlations are reproduced. A second application concerns the spectral density of doped and undoped Cu(SINGLE BOND)O planes which are part of the high-Tc superconducting materials. © 1997 John Wiley & Sons, Inc. J Quant Chem 63: 645–653, 1997 相似文献
500.