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101.
The effect of microstructure on the rheology of clay/polymer nanocomposites is investigated using dispersions of organically
treated clay in nearly Newtonian poly(dimethylsiloxane). Degree of dispersion and floc size are altered by using two different
dispersion procedures and by changing the shear history. The scaling for dynamic moduli of attractive colloids applies, except
for a possible relaxation mechanism at very low frequencies. The time to reach the crossover at a given frequency is found
to be extremely sensitive to the dispersion procedure used. Hydrodynamic and elastic components of the steady state stress,
on the other hand, evolve in a very similar fashion for the different systems. Although the relaxation times of the elastic
stress components change drastically with flow-induced changes in structure, the dispersion process hardly has an effect at
all. Intermittent start-up flows in the forward and reverse directions show that anisotropy persists long after the flow has
been arrested, even at shear rates where no large reversible flocs are present. The degree of dispersion only had a limited
effect on the anisotropy. Finally, the effect of shear on structure recovery has been studied. Very low shear rates are found
to increase the rate of recovery, even for small strains. 相似文献
102.
The use of municipal solid waste (MSW) compost as a sorbent for tributyltin (TBT) in seawater was investigated. TBT‐contaminated seawater, both artificially prepared and that collected from Msida Creek yacht marina (Malta), was allowed to percolate through untreated and water‐washed columns of compost and then analysed for organotins using gas chromatography‐flame photometric detection. About 90% of dissolved TBT ranging in concentration from about 800 to 8000 ngSnl?1 was sorbed by treating 500 ml solutions with 100 g untreated compost. On the other hand, no detectable breakthrough of TBT was observed from compost that had previously been washed by water to remove soluble organic matter. Breakthrough of TBT from unwashed compost is thought to be due to formation of complexes between the soluble organic matter in compost and aquated TBT, which renders the organotin more hydrophilic. The use of washed MSW compost as sorbent for the purification of TBT‐contaminated waters generated in large quantity during hull‐cleaning activities in drydocks is suggested as a mitigatory measure against the impact of TBT on the coastal marine environment. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
103.
104.
Differential scanning calorimetry (DSC) is one of the most frequently used techniques for analyzing small concentrations of
amorphous phases in a crystalline matrix. In recent years novel enhanced DSC approaches have been intensively looked for to
improve parameters such as sensitivity, accuracy, and detection limit of the technique. Low levels of amorphous phases can
be quantitatively determined in DSC by measuring the heat capacity change associated with the glass transition. In this short
review the potentials provided by the HyperDSC and StepScan DSC techniques are discussed. Examples illustrate the advantages
and disadvantages of the techniques and compare their abilities to detect small glass transitions and determine low contents
of amorphous phases in samples which are mostly crystalline. 相似文献
105.
Background
Triptolide is a diterpene triepoxide from the Chinese medicinal plant Tripterygium wilfordii Hook F., with known anti-inflammatory, immunosuppressive and anti-cancer properties. 相似文献106.
A. Gareth Brenton A. Ruth Godfrey 《Journal of the American Society for Mass Spectrometry》2010,21(11):1821-1835
High-resolution mass spectrometry has become ever more accessible with improvements in instrumentation, such as modern FT-ICR
and Orbitrap mass spectrometers. This has resulted in an increase in the number of articles submitted for publication quoting
accurate mass data. There is a plethora of terms related to accurate mass analysis that are in current usage, many employed
incorrectly or inconsistently. This article is based on a set of notes prepared by the authors for research students and staff
in our laboratories as a guide to the correct terminology and basic statistical procedures to apply in relation to mass measurement,
particularly for accurate mass measurement. It elaborates on the editorial by Gross in 1994 regarding the use of accurate
masses for structure confirmation [1]. We have presented and defined the main terms in use with reference to the International
Union of Pure and Applied Chemistry (IUPAC) recommendations for nomenclature and symbolism for mass spectrometry. The correct
use of statistics and treatment of data is illustrated as a guide to new and existing mass spectrometry users with a series
of examples as well as statistical methods to compare different experimental methods and datasets. 相似文献
107.
Bilateral cochlear implant (BiCI) users gain an advantage in noisy situations from a second implant, but their bilateral performance falls short of normal hearing listeners. Channel interactions due to overlapping electrical fields between electrodes can impair speech perception, but its role in limiting binaural hearing performance has not been well characterized. To address the issue, binaural masking level differences (BMLD) for a 125 Hz tone in narrowband noise were measured using a pair of pitch-matched electrodes while simultaneously presenting the same masking noise to adjacent electrodes, representing a more realistic stimulation condition compared to prior studies that used only a single electrode pair. For five subjects, BMLDs averaged 8.9 ± 1.0 dB (mean ± s.e.) in single electrode pairs but dropped to 2.1 ± 0.4 dB when presenting noise on adjacent masking electrodes, demonstrating a negative impact of the additional maskers. Removing the masking noise from only the pitch-matched electrode pair not only lowered thresholds but also resulted in smaller BMLDs. The degree of channel interaction estimated from auditory nerve evoked potentials in three subjects was significantly and negatively correlated with BMLD. The data suggest that if the amount of channel interactions can be reduced, BiCI users may experience some performance improvements related to binaural hearing. 相似文献
108.
Equations are found for exact g -functions corresponding to integrable bulk and boundary flows between successive unitary c<1 minimal conformal field theories in two dimensions, confirming and extending previous perturbative results. These equations are obtained via an embedding of the flows into a boundary version of Al. Zamolodchikov's staircase model. 相似文献
109.
110.
The covering spectrum is a geometric invariant of a Riemannian manifold, more generally of a metric space, that measures the size of its one-dimensional holes by isolating a portion of the length spectrum. In a previous paper we demonstrated that the covering spectrum is not a spectral invariant of a manifold in dimensions three and higher. In this article we give an example of two isospectral Cayley graphs that admit length space structures with distinct covering spectra. From this we deduce the existence of infinitely many pairs of Sunada-isospectral surfaces with unequal covering spectra. 相似文献