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51.
Equilibrium charge state distributions of beam foil excited molecular fragments exiting carbon foils
R. Schramm D. Hofmann P. Koschar H. J. Frischkorn J. Kemmler E. Rohrbach K. O. Groeneveld 《Il Nuovo Cimento D》1986,7(2):203-211
Summary Equilibrium charge state distributions of ions emerging from solids have been measured. As incident particles were used both
atomic (C+, N+, O+) and molecular (N
2
+
, CO+) projectile ions (0.025<E/M<0.108 MeV/u). The data of atomic projectile ions agree well with the data of other authors in a range in which they overlap.
Charge state fractions of emerging molecular-fragment ions behind a carbon foil are strongly influenced by the Coulomb explosion
and possibly by the wake potential.
Supported by BMFT/Bonn. 相似文献
52.
Sebastian Reicherts Sebastian Blume Christopher Reichert Dr.-Ing. Dr. h.c. Dieter Schramm 《PAMM》2016,16(1):859-860
Uncertainties in the kinematic parameters like the pulley positions take a major influence onto the force capability of a cable-driven parallel robot. For that purpose this paper describes a calibration method to estimate exactly the underlying kinematic parameters. As the kinematic is influenced by a variety of different parameter, the calibration can be very complex and time consuming. In this approach, a sensitivity analysis of a cable-driven parallel robot is presented to simplify and enhance the calibration. The results are discussed and the further steps are introduced. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
53.
Schober Y Schramm T Spengler B Römpp A 《Rapid communications in mass spectrometry : RCM》2011,25(17):2475-2483
The spatial distribution of proteins in tissue sections can be used to identify potential markers for pathological processes. Tissue sections are often subjected to enzymatic digestion before matrix‐assisted laser desorption/ionization (MALDI) imaging. This study is targeted at improving the on‐tissue identification of tryptic peptides by accurate mass measurements and complementary off‐line liquid chromatography coupled to electrospray ionization tandem mass spectrometry (LC/ESI‐MS/MS) analysis. Two adjacent mouse brain sections were analyzed in parallel. The first section was spotted with trypsin and analyzed by MALDI imaging. Direct on‐tissue MS/MS experiments of this section resulted in the identification of 14 peptides (originating from 4 proteins). The second tissue section was homogenized, fractionated by ultracentrifugation and digested with trypsin prior to LC/ESI‐MS/MS analysis. The number of identified peptides was increased to 153 (corresponding to 106 proteins) by matching imaged mass peaks to peptides which were identified in these LC/ESI‐MS/MS experiments. All results (including MALDI imaging data) were based on accurate mass measurements (RMS <2 ppm) and allow a confident identification of tryptic peptides. Measurements based on lower accuracy would have led to ambiguous or misleading results. MS images of identified peptides were generated with a bin width (mass range used for image generation) of Δm/z = 0.01. The application of accurate mass measurements and additional LC/MS measurements increased both the quality and the number of peptide identifications. The advantages of this approach for the analysis of biological tissue sections are demonstrated and discussed in detail. Results indicate that accurate mass measurements are needed for confident identification and specific image generation of tryptic peptides in tissue sections. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
54.
González-Prieto R Fleury B Schramm F Zoppellaro G Chandrasekar R Fuhr O Lebedkin S Kappes M Ruben M 《Dalton transactions (Cambridge, England : 2003)》2011,40(29):7564-7570
Two 2,6-bispyrazolylpyridine ligands (bpp) were functionalized with pyrene moieties through linkers of different lengths. In the ligand 2,6-di(1H-pyrazol-1-yl)-4-(pyren-1-yl)pyridine (L1) the pyrene group is directly connected to the bpp moiety via a C-C single bond, while in the ligand 4-(2,6-di(1H-pyrazol-1-yl)pyridin-4-yl)benzyl-4-(pyren-1-yl)butanoate (L2) it is separated by a benzyl ester group involving a flexible butanoic chain. Subsequent complexation of Fe(II) salts revealed dramatic the influence of the nature of the pyrene substitution on the spin-transition behaviour of the resulting complexes. Thus, compound [Fe(L1)(2)](ClO(4))(2) (1) is blocked in its high spin state due to constraints caused by a strong intermolecular π-π stacking in its structure. On the other hand, the flexible chain of ligand L2 in compounds [Fe(L2)(2)](ClO(4))(2) (2) and [Fe(L2)(2)](BF(4))(2)·CH(3)CN·H(2)O (3) prevents structural constraints allowing for reversible spin transitions. Temperature-dependent studies of the photophysical properties of compound 3 do not reveal any obvious correlation between the fluorescence of the pyrene group and the spin state of the spin transition core. 相似文献
55.
Protein motions that occur on the microsecond to millisecond time scale have been linked to enzymatic rates observed for catalytic turnovers, but not to transition-state barrier crossing. It has been hypothesized that enzyme motions on the femtosecond time scale of bond vibrations play a role in transition state formation. Here, we perturb femtosecond motion by substituting all nonexchangeable carbon, nitrogen, and hydrogen atoms with (13)C, (15)N, and (2)H and observe the catalytic effects in HIV-1 protease. According to the Born-Oppenheimer approximation, isotopic substitution alters vibrational frequency with unchanged electrostatic properties. With the use of a fluorescent peptide to report on multiple steps in the reaction, we observe significantly reduced rates in the heavy enzyme relative to the light enzyme. A possible interpretation of our results is that there exists a dynamic link between mass-dependent bond vibrations of the enzyme and events in the reaction coordinate. 相似文献
56.
Facing the difficulties associated with the preparation of crystalline ion beams in heavy ion storage rings we propose two
complementary table top schemes to elucidate fundamental issues like stability criteria for moving ion crystals at low velocities.
One is based on a small radio-frequency quadrupole (RFQ) storage ring, where by laser cooling Mg+ ion crystals at rest were observed, but conceptionally modified with additional acceleration electrodes and manufactured
with highest mechanical precision. The other approach suggested here implies the use of an RFQ ion guide for the lateral confinement
of the ions combined with buffer gas viscous damping, which could lead to an ideal starting condition for first time direct
three-dimensional laser cooling in a single pass arrangement.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
57.
Consider the standard continuous percolation in ℝ4, and choose the parameters so that the induced percolation on a fixed two dimensional linear subspace is critical. Although
two dimensional critical percolation dies, we show that there are exceptional two dimensional linear subspaces, in which percolation
occurs.
Received: 1 April 1997 / Revised version: 20 January 1998 相似文献
58.
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Ohne Zusammenfassung 相似文献