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排序方式: 共有102条查询结果,搜索用时 31 毫秒
51.
Thermal degradation characteristics of some poly[poly(ethylene glycol)] phosphates (PPEGP) based on ethylene glycol (PEGP), an equimolar mixture of ethylene glycol and trigol (PETP), digol (PDGP), and trigol (PTGP) have been studied by combined differential thermal and thermogravimetric analyses (DTA/TGA). It has been shown that, in spite of their structural similarities, the PPEGPs do not conform to any generalized degradation pattern. Local strains in the crosslinked network and the possible intranetwork topographic interferences due to crossovers, entanglements, and varying lengths of polyoxyethylene link units are believed to play a pivotal role in the thermal degradation of individual PPEGPs. © 1995 John Wiley & Sons, Inc. 相似文献
52.
A full-field technique for simultaneous measurement of the magnitude of birefringence and its orientation is presented. This is achieved using a monolithic birefringence sensitive interferometer where the interference fringes carry the information of both the birefringence phase and the orientation of the fast axis of an optically transmissive anisotropic material placed at the output of the interferometer. The interferometer consists of a suitably polarization-masked cube beam splitter, orientated as in the Gates interferometer, which serves to generate a pair of orthogonally polarized and collinearly propagating light beams. Experimental results are obtained through an algorithm incorporating eight polarization phase-shifted interferograms. 相似文献
53.
Mackenzie Moore Nandini Avula Seokwon Jo Megan Beetch Emilyn U. Alejandro 《International journal of molecular sciences》2021,22(13)
Placental dysfunction can lead to fetal growth restriction which is associated with perinatal morbidity and mortality. Fetal growth restriction increases the risk of obesity and diabetes later in life. Placental O-GlcNAc transferase (OGT) has been identified as a marker and a mediator of placental insufficiency in the setting of prenatal stress, however, its role in the fetal programming of metabolism and glucose homeostasis remains unknown. We aim to determine the long-term metabolic outcomes of offspring with a reduction in placental OGT. Mice with a partial reduction and a full knockout of placenta-specific OGT were generated utilizing the Cre-Lox system. Glucose homeostasis and metabolic parameters were assessed on a normal chow and a high-fat diet in both male and female adult offspring. A reduction in placental OGT did not demonstrate differences in the metabolic parameters or glucose homeostasis compared to the controls on a standard chow. The high-fat diet provided a metabolic challenge that revealed a decrease in body weight gain (p = 0.02) and an improved insulin tolerance (p = 0.03) for offspring with a partially reduced placental OGT but not when OGT was fully knocked out. Changes in body weight were not associated with changes in energy homeostasis. Offspring with a partial reduction in placental OGT demonstrated increased hepatic Akt phosphorylation in response to insulin treatment (p = 0.02). A partial reduction in placental OGT was protective from weight gain and insulin intolerance when faced with the metabolic challenge of a high-fat diet. This appears to be, in part, due to increased hepatic insulin signaling. The findings of this study contribute to the greater understanding of fetal metabolic programming and the effect of placental OGT on peripheral insulin sensitivity and provides a target for future investigation and clinical applications. 相似文献
54.
55.
R. Sarathi Arya Nandini Toshikatsu Tanaka 《Electrical Engineering (Archiv fur Elektrotechnik)》2011,93(4):199-207
In the present work, electrical trees were experimentally generated in virgin and gamma-irradiated XLPE cable insulation,
under AC voltages. Fibrillar type of electrical tree structure forms from the defect site in gamma-irradiated specimens. Failure
times due to electrical trees were analysed by adopting Weibull distribution studies. The results of the study indicate that
gamma-irradiated specimens, where the rate of tree propagation is high, causing early failure of insulation. Pulsed electro
acoustic emission (PEAE) technique was adopted to understand the space charge formation in XLPE cable insulation. The results
of the study indicate that homo and hetero charges form near to the electrodes especially in gamma-irradiated XLPE cable insulation.
Variations in space charge density at different voltage magnitudes with time were analysed. It is observed that the electric
field in the insulating material becomes highly non-uniform on occurrence of hetero charges. It is also realized that on removal
of applied voltage, the charge decay is less with gamma-irradiated specimens. Based on the present study, it could be concluded
that Space charge density in insulating material and life of insulating material due to electrical tree formation shows inverse
relationship. 相似文献
56.
Nandini Jaiswal Shail Upadhyay Devendra Kumar Om Parkash 《International Journal of Hydrogen Energy》2014
A few compositions in the system, Ce1 − x − ySmxSryO1.90 have been prepared by citrate–nitrate auto-combustion method. X-ray diffraction data show that all the compositions are solid solution having cubic fluorite structure. Density of the samples sintered at 1350 °C has been found to be more than 95% of the theoretical value. Surface morphology has been studied by scanning electron microscope. AC impedance spectroscopy measurements have been carried out to study the grains, grain boundaries and total ionic conductivity of the samples in the temperature range 200–600 °C. The composition, Ce0.82Sm0.16Sr0.02O1.90 shows the maximum conductivity i.e. 2.67 × 10−2 S-cm−1 at 600 °C among all the compositions investigated. This is about two times higher than that of Ce0.80Sm0.20O1.90. 相似文献
57.
58.
Xianjie Qiu Nandini Sane Parthasakha Neogi 《American Institute of Chemical Engineers》2019,65(11):e16720
Models for drug delivery are based on the use of stirred tanks to represent organs that contain no mass transfer resistances. In the original Krogh cylinder model, a mass transfer resistance shows up but there is no convection in the tissue where convection should matter. In the present study, a two-dimensional flow field is used to show that when a liquid enters the capillary, some leave through the walls into the tissue at the arterial end and then doubles back into the capillary at the venous end. Some flow does not return which is taken to be the flow to the lymphatic system. We can get the measured transcapillary pressure drop of about 2,666 Pa if in addition the compliance of the tube wall is taken into account. Very realistic flow fields have been shown for a model liver and a tumor. 相似文献
59.
60.
S. V. Narasimhan M. Harish A. R. Haripriya Nandini Basumallick 《Signal, Image and Video Processing》2009,3(1):85-99
This paper proposes a new harmonic wavelet transform (HWT) based on discrete cosine transform (DCTHWT) and its application
for signal or image compression and subband spectral estimation using modified group delay (MGD). Further, the existing DFTHWT
has also been explored for image compression. The DCTHWT provides better quality decomposed decimated signals, which enable
improved compression and MGD processing. For signal/image compression, compared to the HWT based on DFT (DFTHWT), the DCTHWT
reduces the reconstruction error. Compared to DFTHWT for the speech signal considered for a compression factor of 0.62, the
DCTWHT provides a 30% reduction in reconstruction error. For an image, the DCTHWT algorithm due to its real nature, is computationally
simple and more accurate than the DFTHWT. Further compared to Cohen–Daubechies–Feauveau 9/7 biorthogonal symmetric wavelet,
the DCTHWT, with its computational advantage, gives a better or comparable performance. For an image with 6.25% coefficients,
the reconstructed image by DFTHWT is significantly inferior in appearance to that by DCTHWT which is reflected in the error
index as its values are 3.0 and 2.65%, respectively. For spectral estimation, DCTHWT reduces the bias both in frequency (frequency
resolution) and spectral magnitude. The reduction in magnitude bias in turn improves the signal detectability. In DCTHWT,
the improvement in frequency resolution and the signal detectability is not only due to good quality DCT subband signals but
also due to their stretching (decimation) in the wavelet transform. The MGD reduces the variance while preserving the frequency
resolution achieved by DCT and decimation. In view of these, the new spectral estimator facilitates a significant improvement
both in magnitude and frequency bias, variance and signal detection ability; compared to those of MGD processing of both DFT
and DCT fullband and DFT subband signals. 相似文献