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121.
122.
A fundamental study of raceway size in two dimensions 总被引:4,自引:0,他引:4
Blast furnace raceway zones are formed by the force of the air blast injected through the tuyeres evacuating a region of the
packed bed directly in front of these tuyeres. Raceway depths in blast furnaces have been historically predicted through the
use of empirical correlations based on measurements on cold and hot models. These correlations are not found to be universal
in application, however, with many researchers finding only fair agreement between their experi-mental data and the correlations
proposed by other researchers. We present here an alternative physical mechanism approach for raceway formation based on examination
of the fundamental properties of the system. The study includes two-dimensional experiments where raceway depths and shapes
are measured and an accompanying theoretical and numerical analysis of the under-lying mechanisms. Gas flow distributions
around the raceway zone are also examined. It is found that the raceway size for given blast conditions and particle properties
is such that the total gas drag on the solids vertically above the raceway balances the solid bed weight, with some allowance
for solid holdup by walls. The formulation of this theory leads to the further conclusion that the total surface area of the
raceway walls as a fraction of the horizontal cross-sectional area of the container or furnace is a unique function of three
factors: (a) the gas flow rate as a fraction of the gas flow rate required to fluidize the bed, (b) a particle Reynolds number
calculated at the particle's incipient fluidization velocity, and (c) the shape of the horizontal cross section of the bed. 相似文献
123.
M Grey AG Borg P Wood R Burgess A Fisher JA Yin 《Canadian Metallurgical Quarterly》1997,21(9):867-874
Multidrug resistance (MDR) mediated by the drug efflux pump P-glycoprotein (Pgp), may cause remission failure and relapse in patients with acute myeloid leukaemia (AML) by extruding cytotoxic agents such as anthracyclines from leukaemic cells thus allowing them to survive. Cell line data suggest that reversal of MDR is possible using modifying drugs such as cyclosporin A (CSA) and its analogue PSC 833. We have investigated the effects on cell kill of the addition of CSA and PSC 833 to daunorubicin, idarubicin, mitozantrone, etoposide and cytarabine in 52 fresh cell samples from AML patients using an MTT assay. Pgp status was determined by using monoclonal antibodies JSB-1 and MRK-16 and by assessment of rhodamine efflux. Although overall each cytotoxic-modifier combination produced significant improvements in cell kill compared to cytotoxic alone (P values ranged from P < 0.001 to P = 0.017), modifiers also produced significant cytotoxicity in their own right, and no consistent difference was seen between responses in Pgp-positive and negative groups. Up to one in three Pgp-positive samples failed to show any improvement in cell kill with the addition of CSA or PSC 833, possibly owing to co-expression of alternative resistance mechanisms not affected by the MDR modifiers. The best responses were seen when PSC 833 was added to idarubicin, with 7 out of 22 Pgp-positive cases (32%) showing five-fold improvements in cell kill or better compared to idarubicin alone. Comparison of equimolar concentrations of the two modifiers in the Pgp positive group failed to show a significant difference in cell kill, though PSC 833 was markedly superior to CSA in a minority of highly responsive samples which demonstrated clear evidence of MDR reversal. Our in vitro data suggest that MDR modifiers such as CSA and PSC 833 could play an important role in the therapy of AML and indicate the need for prospective randomised trials to assess their clinical efficacy. 相似文献
124.
We measured human observers' detectability of aperiodic signals in noise with two components (white and low-pass Gaussian). The white-noise component ensured that the signal detection task was always noise limited rather than contrast limited (i.e., image noise was always much larger than observer internal noise). The low-pass component can be considered to be a statistically defined background. Contrast threshold elevation was not linearly related to the rms background contrast. Our results gave power-law exponents near 0.6, similar to that found for deterministic masking. The Fisher-Hotelling linear discriminant model assessed by Rolland and Barrett [J. Opt. Soc. Am. A 9, 649 (1992)] and the modified nonprewhitening matched filter model suggested by Burgess [J. Opt. Soc. Am. A 11, 1237 (1994)] for describing signal detection in statistically defined backgrounds did not fit our more precise data. We show that it is not possible to find any nonprewhitening model that can fit our data. We investigated modified Fisher-Hotelling models by using spatial-frequency channels, as suggested by Myers and Barrett [J. Opt. Soc. Am. A 4, 2447 (1987)]. Two of these models did give good fits to our data, which suggests that we may be able to do partial prewhitening of image noise. 相似文献
125.
An optical sensing technique is described and evaluated for sensitivity to changes in refractive index and absorbance of model sample matrices. A binary dielectric/metal transmission diffraction grating is placed in contact with a sample and utilized in reflection mode; thus, the light captured and analyzed does not pass through the sample. This particular condition creates thresholds at which a particular transmitted diffraction order is transformed from a traveling wave to an evanescent one. The positions of these thresholds depend upon the complex dielectric function of the sample, the period of the grating, and the wavelength and incident angle of light striking the grating. Experimental evidence directly supports the theoretical predictions regarding responses to both the real and imaginary portions of the refractive index: the reflection coefficient derivative wavelength peak position shifts linearly with changes in the real part of the refractive index, and the derivative peak amplitudes exhibit a square-root dependence on absorbance. Refractive index sensitivity to a series of ethanol/water solutions is demonstrated with detectable changes in index as small as 2 × 10(-)(6). Absorbance sensitivity is shown via the differentiation of methylene blue samples having equivalent 1 cm path length absorbances between 0.459 and 244 AU. In a single reflection measurement, GLRS offers a large dynamic range for absorbance detection, allows simultaneous determination of bulk refractive index in optically dense media, and provides a platform for performing continuous process analysis. 相似文献
126.
The transport of trichloroethylene, 1,1,1-trichloroethane, and toluene in aqueous solutions through a polydimethylsiloxane film was modeled using a Fickian diffusion model to fit data obtained from an evanescent fiber-optic chemical sensor (EFOCS). The resultant diffusion coefficients for these analytes were respectively 3 × 10(-)(7), 5 × 10(-)(7), and 1 × 10(-)(7) cm(2)/s. Inclusion of an interfacial conductance term, defined as the ratio of the mass transport coefficient across the polymer surface and the analyte diffusion coefficient in the polymer, was required to accurately model the data. It was determined that the interfacial conductance terms were generally of the same order of magnitude for the analytes examined, suggesting a constant transport mechanism for the analytes. Linear chemometric algorithms were used to model the EFOCS response to aqueous mixtures of the three analytes with individual analyte concentrations between 20 and 300 ppm. Both partial least-squares and principal component regression algorithms performed comparably on the calibration sets, with cross-validated root-mean-squared errors of prediction for trichloroethylene, 1,1,1-trichloroethane, and toluene of approximately 26, 29, and 22 ppm, respectively. The resultant prediction model was then used to determine analyte concentrations in an independent data set with comparable precision. 相似文献
127.
Theory, explanation, and a third generation of theoretical development in social gerontology 总被引:1,自引:0,他引:1
Efforts at cumulative knowledge building in social gerontology have been lax, judging from research articles published in journals between 1990 and 1994. Too little attention has been paid to the cumulative development of theory; readers are left with many empirical generalizations but underdeveloped explanations by which to interpret findings and build upon them in subsequent research. To assist future theory development in social gerontology, we review seven theoretical perspectives referenced most frequently in recent journals: (1) social constructionist, (2) social exchange, (3) life course, (4) feminist, (5) age stratification (age and society), (6) political economy of aging, and (7) critical theory. We suggest that, taken together, these represent a "third generation" of explanation in social gerontology, noting their debt to older and more established traditions in social science theory. We argue that authors and journal reviewers should place more emphasis on theory development - which means, most simply, the construction of explicit explanations in accounting for empirical findings - if knowledge development about social aspects of aging is to be cumulative, systematic, and incremental. 相似文献
128.
Fluorescence recovery after photobleaching (FRAP) was used to quantify the translational diffusion of microinjected FITC-dextrans and Ficolls in the cytoplasm and nucleus of MDCK epithelial cells and Swiss 3T3 fibroblasts. Absolute diffusion coefficients (D) were measured using a microsecond-resolution FRAP apparatus and solution standards. In aqueous media (viscosity 1 cP), D for the FITC-dextrans decreased from 75 to 8.4 x 10(-7) cm2/s with increasing dextran size (4-2,000 kD). D in cytoplasm relative to that in water (D/Do) was 0.26 +/- 0.01 (MDCK) and 0.27 +/- 0.01 (fibroblasts), and independent of FITC-dextran and Ficoll size (gyration radii [RG] 40-300 A). The fraction of mobile FITC-dextran molecules (fmob), determined by the extent of fluorescence recovery after spot photobleaching, was >0.75 for RG < 200 A, but decreased to <0.5 for RG > 300 A. The independence of D/Do on FITC-dextran and Ficoll size does not support the concept of solute "sieving" (size-dependent diffusion) in cytoplasm. Photobleaching measurements using different spot diameters (1.5-4 micron) gave similar D/Do, indicating that microcompartments, if present, are of submicron size. Measurements of D/Do and fmob in concentrated dextran solutions, as well as in swollen and shrunken cells, suggested that the low fmob for very large macromolecules might be related to restrictions imposed by immobile obstacles (such as microcompartments) or to anomalous diffusion (such as percolation). In nucleus, D/Do was 0.25 +/- 0.02 (MDCK) and 0.27 +/- 0.03 (fibroblasts), and independent of solute size (RG 40-300 A). Our results indicate relatively free and rapid diffusion of macromolecule-sized solutes up to approximately 500 kD in cytoplasm and nucleus. 相似文献
129.
C. H. Burgess 《Materials Science & Technology》2017,33(7):809-821
Atomic layer deposition (ALD) is an increasingly popular thin film deposition technique which offers unique large area capability combined with excellent conformality, thus ALD will likely be important in the development of next generation optoelectronic devices. Such device platforms include solar cells, thin film transistors and light emitting diodes, and in all of these technologies one material is frequently used – zinc oxide (ZnO) – owing to its excellent electrical and optical properties combined with earth abundance. The approaches and achievements in tailoring the properties of ALD ZnO are discussed. Key process variables include deposition temperature and purge times as well dopant incorporation, with particular attention paid to tuning band alignment and carrier concentrations (focusing on lower carrier concentration applications).
This review was submitted as part of the 2016 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged. 相似文献
130.
J. E. Burgess BSc PhD CBiol MIBiol M. E. Mayhew BSc PhD DPD GIBiol T. Stephenson BSc PhD DIC CEng FIChemE T. A. Clark BSc MSc PhD GRSC 《Water and Environment Journal》2002,16(1):40-45
An organism diversity index for use with mixed liquor or wastewater samples was developed to assess the species richness and diversity of activated sludge. The index was used in several studies and was found to be fast and simple to perform using basic laboratory equipment. Two bench-scale and two pilot-scale studies found that the resulting 'organism diversity index'value was a good indicator of process performance and was not influenced by the total concentration of the mixed-liquor suspended solids but by their nature alone. The technique rapidly yielded pertinent information about the health of the sludge and could be used instead of genetic investigations to obtain population information quickly enough for wastewater-treatment plant process control. 相似文献