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排序方式: 共有158条查询结果,搜索用时 31 毫秒
101.
Stephen A. Wise Michele M. Schantz Barbara J. Koster Rabia Demiralp Elizabeth A. Mackey Robert R. Greenberg Mechthild Burow Peter Ostapczuk Ted I. Lillestolen 《Fresenius' Journal of Analytical Chemistry》1993,345(2-4):270-277
Summary Fresh frozen homogenates of pilot whale blubber and liver tissue were prepared for use as control materials for the determination of organic and inorganic contaminants in marine mammal tissue analyses. The blubber material was analyzed to determine 30 polychlorinated biphenyl congeners and 16 chlorinated pesticides using gas chromatography with electron capture detection and gas chromatographymass spectrometry. A total of 39 trace elements and methylmercury were determined in the liver homogenate using instrumental neutron activation analysis, voltammetry, and cold vapor atomic absorption spectroscopy. The preparation and analysis of these two tissue materials are part of the development of marine mammal tissue reference materials. 相似文献
102.
103.
S. Guggenheim A. F. Koster van Groos 《Journal of Thermal Analysis and Calorimetry》1992,38(7):1701-1728
High-pressure differential thermal analysis results are used to describe dehydration reactions for the clay-like materials of Na-rich montmorillonite, K-, Ca-, and Mg-exchanged montmorillonite, kerolite, and a high-pressure phase resembling talc/mica with excess water. Because sealed capsules may be used to contain fluids, it is possible to evaluate the role of H2O in these reactions. A separate paper (Part II) addresses the use of HP-DTA to understand dehydroxylation reactions in these materials. 相似文献
104.
Bahreman A Limburg B Siegler MA Koning R Koster AJ Bonnet S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(33):10271-10280
The new ruthenium complex [Ru(terpy)(dcbpy)(Hmte)](PF(6) )(2) ([2](PF(6) )(2) ; dcbpy=6,6'-dichloro-2,2'-bipyridine, terpy=2,2';6',2"-terpyridine, Hmte=2-(methylthio)ethanol) was synthesized. In the crystal structure, this complex is highly distorted, revealing steric congestion between dcbpy and Hmte. In water, [2](2+) forms spontaneously by reacting Hmte and the aqua complex [Ru(terpy)(dcbpy)(OH(2) )](2+) ([1](2+) ), with a second-order rate constant of 0.025?s(-1) M(-1) at 25?°C. In the dark, the Ru?S bond of [2](2+) is thermally unstable and partially hydrolyzes; in fact, [1](2+) and [2](2+) are in an equilibrium characterized by an equilibrium constant K of 151?M(-1) . When exposed to visible light, the Ru?S bond is selectively broken to release [1](2+) , that is, the equilibrium is shifted by visible-light irradiation. The light-induced equilibrium shifts were repeated four times without major signs of degradation; the Ru?S coordination bond in [2](2+) can be described as a robust, light-sensitive, supramolecular bond in water. To demonstrate the potential of this system in supramolecular chemistry, a new thioether-cholesterol conjugate (4), which inserts into lipid bilayers through its cholesterol moiety and coordinates to ruthenium through its sulfur atom, was synthesized. Thioether-functionalized, anionic, dimyristoylphosphatidylglycerol (DMPG), lipid vesicles, to which aqua complex [1](2+) efficiently coordinates, were prepared. Upon exposure of the Ru-decorated vesicles to visible light, the Ru?S bond is selectively broken, thus releasing [1](2+) that stays at the water-bilayer interface. When the light is switched off, the metal complex spontaneously coordinates back to the membrane-embedded thioether ligands without a need to heat the system. This process was repeated four times at 35?°C, thus achieving light-triggered hopping of the metal complex at the water-bilayer interface. 相似文献
105.
This paper proposes an approximation model based on queuing network theory to analyze the impact of order batching and picking area zoning on the mean order throughput time in a pick-and-pass order picking system. The model includes the sorting process needed to sort the batch again by order. Service times at pick zones are assumed to follow general distributions. The first and second moments of service times at zones and the visiting probability of a batch of orders to a pick zone are derived. Based on this information, the mean throughput time of an arbitrary order in the order picking system is obtained. Results from a real application and simulation show that this approximation model provides acceptable accuracy for practical purposes. Furthermore, the proposed method is simple and fast and can be easily applied in the design and selection process of order picking systems. 相似文献
106.
J.H. Brewer D.R. Harshman E. Koster H. Schilling D.Ll. Williams M.G. Priestley 《Solid State Communications》1983,46(12):863-865
The Knight shift Kμ at the positive muon has been measured as a function of magnetic field, temperature, crystal orientation and alloyed impurity (bismuth or tin) in antimony. The anomalously large and anisotropic Kμ in pure Sb at low temperature has been confirmed and shown to be independent of magnetic field up to 9 kG; its anisotropic part is found to have the same strong temperature dependence as its isotropic component. The addition of 6.3 at.% Bi significantly reduces both Kμ and its anisotropy, but enhances their temperature dependence. The addition of 12.5 at.% Bi, or, more dramatically, as little as 0.3 at.% Sn to antimony is sufficient to reduce Kμ to a small value, effectively eliminating the anomalous behaviour. 相似文献
107.
108.
D. G. Haase C. R. Gould J. E. Koster N. R. Roberson L. W. Seagondollar J. P. Soderstrum M. B. Schneider X. Zhu 《Hyperfine Interactions》1988,43(1-4):133-138
We describe searches for parity and time reversal violations in the scattering of polarized neutrons from polarized and aligned165Ho targets. We have completed a search with 7.1 and 11.0 MeV neutrons for PoddTodd terms in the elastic scattering forward amplitude of the form s. (I×K), wheres is the neutron spin,I is the target spin andk is the neutron momentum vector. The target was a single crystal of holmium, polarized horizontally along itsb axis by a 1 Tesla magnetic field. The neutrons were polarized vertically. Differences in the neutron transmission were measured
for neutrons with spins parallel (antiparallel) toI×k. The P,T violating analyzing powers were found to be consistent with zero at the few 10−3 level: ρP,T(7.1 MeV)=−0.88 (±2.02) x 10−3, ρP,T(11.0 MeV)=−0.4 (±2.88) x 10−3. We have also attempted to find enhancements with MeV neutrons in P-violation due to the term s\k. We are preparing an aligned target cryostat for investigations of PevenTodd terms {bd(I\k)(I×k)\s} in neutron scattering. The target will be a single crystal cylinder of165Ho cooled to 100 mK in a bath of liquid helium and rotated by a shaft from a room temperature stepping motor. The cylinder
will be oriented vertically and the alignment (c) axis oriented horizontally. Warming or rotation of the sample allows one to separate effects that mimic the sought-after
time reversal violating term. 相似文献
109.
110.
The photocurrent in conjugated polymer-fullerene blends is dominated by the dissociation efficiency of bound electron-hole pairs at the donor-acceptor interface. A model based on Onsager's theory of geminate charge recombination explains the observed field and temperature dependence of the photocurrent in PPV:PCBM blends. At room temperature only 60% of the generated bound electron-hole pairs are dissociated and contribute to the short-circuit current, which is a major loss mechanism in photovoltaic devices based on this material system. 相似文献