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551.
Effects of restricted diffusion in a biological phantom: a q-space diffusion MRI study of asparagus stems at a 3T clinical scanner 总被引:1,自引:1,他引:0
Lätt J Nilsson M Rydhög A Wirestam R Ståhlberg F Brockstedt S 《Magma (New York, N.Y.)》2007,20(4):213-222
Introduction The aim of this work was to study the effects of restricted diffusion in a biological phantom consisting of green asparagus
stems using q-space MRI at a clinical scanner.
Method Measurements of the full width at half maximum (FWHM) of the displacement distribution were performed with varied diffusion
time (T
d). The accuracy of the measurements was investigated with respect to the degree of violation of the short gradient pulse (SGP)
condition, partial volume effects and a FWHM-based tensor model.
Results The measurements showed a reasonably constant FWHM perpendicular to the capillaries in the vascular bundles and an increased
FWHM parallel with the bundles when the T
d was increased. A 15% decrease in FWHM perpendicular to the bundles was observed when the diffusion encoding duration was
prolonged from 24 to 74 ms, owing to the violation of the SGP condition. For a population of different confinement sizes,
simulations indicated that the FWHM reflects the smaller sizes rather then the mean size of the confinements.
Conclusion A new method allowing tensor analysis of FWHM was derived and yielded accurate results. In conclusion, we found it possible
to measure the effects of restricted diffusion with q-space MRI using a clinical MRI scanner. 相似文献
552.
K. F. Ho S. C. Lee Jimmy C. Yu S. C. Zou Kochy Fung 《The Science of the total environment》2002,300(1-3)
To determine the characteristic of carbonaceous species in atmospheric particles in Hong Kong, PM10 and PM2.5 samples were collected using high volume (hi-vol.) air samplers from November 2000 to February 2001. The organic carbon (OC) and elemental carbon (EC) were analyzed by the selective thermal manganese dioxide oxidation (TMO) method. The ratios of PM2.5/PM10 mass ratios were 0.61, 0.78 and 0.53 for particulate matter collected at PolyU station (PolyU, near a major traffic corridor), Kwun Tong station (KT, mixed residential/commercial/industrial) and the Hok Tsui background station (HT), respectively. These results indicate that the PM2.5 concentrations constitute the majority of the PM10 concentrations, especially in urban and industrial areas of Hong Kong. The average concentrations at the three sites ranged from 73.11 to 83.52 μg/m3 for PM10 and from 42.37 to 57.38 μg/m3 for PM2.5. The highest daily mass concentrations of PM10 and PM2.5 were 125.89 μg/m3 and 116.89 μg/m3 at KT, respectively. The correlation between PM10 and PM2.5 was high at KT and HT (r>0.9, P<0.01). This means that the sources of PM10 and PM2.5 may be the same at both sites. The highest mean concentration of OC (12.02 μg/m3) and EC (6.86 μg/m3) in PM10 was found at the PolyU among the three sites. For PM2.5, the highest mean concentration of OC (10.16 μg/m3) was at KT while the highest mean concentration of EC (7.95 μg/m3) was at PolyU. However, the background concentrations at HT were higher than another background area, Kosan, Korea. Transportation of pollutants from the Asian continent may be responsible for the elevations of EC+OC at the remote site. More than 74% of the EC and more than 79% of the OC were found in the PM2.5 fraction at the three sampling locations. At PolyU station, PM2.5 consisted of 18.18% OC and 11.16% EC while 17.70% OC and 8.81% EC were found in KT station. Thus OC and EC are major constituents of aerosols in Hong Kong. OC/EC ratios for PM10 and PM2.5 were less than 2 at PolyU and KT stations while the ratio exceeded 3 at HT background station. This indicates that OC measured in the urban area may be emitted directly as a primary aerosol. 相似文献
553.
554.
在不同温度下(120~220℃),利用水热法制备了含1wt%、2wt%、4wt%和8wt%Bi2WO6的异质结型Bi2WO6/ZnO复合光催化剂,采用X射线粉末衍射(XRD)、扫描电镜(SEM)、傅里叶变换红外光谱(FT-IR)、紫外可见漫反射(UV-Vis)吸收光谱及光致发光光谱(PL)等系列手段对所制备的光催化剂进行了表征,并以紫外光(365nm)为光源,酸性橙II为降解对象,进行光催化活性测试,考察了不同Bi2WO6复合量及不同水热温度对ZnO光催化剂反应活性的影响.研究表明,异质结型Bi2WO6/ZnO复合光催化剂的光催化活性明显优于纯ZnO和Bi2WO6.当复合4wt%Bi2WO6水热处理温度为150℃时,所制备的复合光催化剂的光催化活性最佳,为纯ZnO的2.6倍.活性提高的主要原因是形成的Bi2WO6/ZnO异质结能显著降低光生电子和空穴对的复合几率,并改善了异质结型Bi2WO6/ZnO复合光催化剂的表面性能. 相似文献
555.
Jessica Nilsson Kerstin Olsson Gabriele Engqvist Jimmy Ekvall Marie Olsson Margareta Nyman Bjrn kesson 《Journal of the science of food and agriculture》2006,86(4):528-538
Bioactive compounds were investigated in genotypes (cauliflower 10, white cabbage 10, curly kale 1) and plant parts of the three crops. The content of most of the major glucosinolates glucobrassicin, sinigrin and glucoiberin differed significantly between cultivars. Samples harvested in 2000 had higher amounts of several glucosinolates than samples from 1999. Within cauliflower the buds of the floret had 1.5 to 2.5‐fold higher concentration of glucobrassicin and 4‐methoxyglucobrassicin than the stalk. In white cabbage several glucosinolates had their highest content in the outer leaves (up to 2‐fold higher). Upper leaves of curly kale contained 5‐fold more of total glucosinolates than lower leaves. Chlorogenic acid was the dominating hydroxycinnamate in curly kale, which also contained at least ten times more of carotenoids (mainly lutein) than white cabbage. Total antioxidant capacity (TAC) assayed with the FRAP method was 0.76 (0.06) µmol/g fw (mean (SD)) in water‐soluble and 0.32 (0.04) in water‐insoluble extracts of cauliflower which was 62–68% higher than in white cabbage. Curly kale contained 6.4 and 6.1 µmol/g fw TAC in water‐soluble and water‐insoluble extracts. TAC did not differ between plant parts. Progoitrin and 4‐hydroxyglucobrassicin were correlated to water‐soluble TAC in white cabbage, probably reflecting a variation in other compounds. Cauliflower contained less glucose, fructose and sorbitol but more sucrose than white cabbage. Curly kale had lower contents of glucose (~2 times), fructose (~4–5 times) and sucrose (20 and 36 times, respectively) than cauliflower and white cabbage, while inositol was only found in curly kale. Storage of white cabbage reduced the amount of sorbitol and sucrose. The study shows that cultivar, plant part and storage affect the content of bioactive compounds in Brassica vegetables. The variation between years, as in cauliflower, is due to environmental factors. Since the cultivar ranking order was rather stable for several components the data could provide a basis for the selection of cultivars optimised for valuable health components for fresh market consumption. Copyright © 2005 Society of Chemical Industry 相似文献
556.
A Survey of Nitrate and Nitrite Concentrations in Conventional and Organic‐Labeled Raw Vegetables at Retail
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Maryuri T. Nuñez de González Wesley N. Osburn Margaret D. Hardin Michael Longnecker Harsha K. Garg Nathan S. Bryan Jimmy T. Keeton 《Journal of food science》2015,80(5):C942-C949
A national survey of the nitrate () and nitrite ( ) concentrations in raw and highly consumed vegetables available at retail in the United States was conducted. A total of 194 samples of fresh broccoli, cabbage, celery, lettuce, and spinach categorized as conventional or organic by label were collected from 5 major cities in different geographic regions of the United States and analyzed to determine and concentrations. There were no differences in the mean values of conventional compared with organic vegetables taken from the 5 metropolitan areas. However, significant differences in mean pairwise comparisons between some conventional and organic vegetables for content were observed. The mean concentration of both conventional and organic vegetables ranged between 0.1 and 1.2 mg/kg of fresh weight (FW) with the exception of conventional spinach that contained 8.0 mg/kg FW. Mean contents of conventional broccoli, cabbage, celery, lettuce, and spinach were 394, 418, 1496, 851, and 2797 mg/kg FW, respectively, while their organic‐labeled counterparts averaged 204, 552, 912, 844, and 1318 mg/kg FW. In most cases, organic vegetables were numerically lower in content than their conventional counterparts. Based on survey results, the finding that low levels were observed in some organic vegetables in different cities may warrant further study to determine if true differences exist, due to production practices, seasonal differences, and the magnitudes of those differences. Furthermore, the geographic differences in content of vegetables may flaw estimates of daily and exposure. 相似文献
557.
第58届年度先锋建筑奖是由美国《建筑师》(《Arch计ecf》)杂志组织举办的2011年度建筑大奖,共有两个项目获奖(Award),另有4个项目受表彰(Citation),而申请参评项目达300个。Hirshhorn这个项目以功能创新、可持续发展、建筑空间对话和视觉;中击力取胜,丰富了建筑的表现力和想象力。本文资料来源为《Architect 》的官方网站www.architectmagazine.com。 相似文献
558.
Brandt AL Castillo A Harris KB Keeton JT Hardin MD Taylor TM 《Journal of food science》2010,75(9):M557-M563
Abstract: Combining food antimicrobials can enhance inhibition of Listeria monocytogenes in ready-to-eat (RTE) meats. A broth dilution assay was used to compare the inhibition of L. monocytogenes resulting from exposure to nisin, acidic calcium sulfate, ɛ-poly-L-lysine, and lauric arginate ester applied singly and in combination. Minimum inhibitory concentrations (MICs) were the lowest concentrations of single antimicrobials producing inhibition following 24 h incubation at 35 °C. Minimum bactericidal concentrations (MBCs) were the lowest concentrations that decreased populations by ≥3.0 log10 CFU/mL. Combinations of nisin with acidic calcium sulfate, nisin with lauric arginate ester, and ɛ-poly-L-lysine with acidic calcium sulfate were prepared using a checkerboard assay to determine optimal inhibitory combinations (OICs). Fractional inhibitory concentrations (FICs) were calculated from OICs and were used to create FIC indices (FICIs) and isobolograms to classify combinations as synergistic (FICI < 1.00), additive/indifferent (FICI= 1.00), or antagonistic (FICI > 1.00). MIC values for nisin ranged from 3.13 to 6.25 μg/g with MBC values at 6.25 μg/g for all strains except for Natl. Animal Disease Center (NADC) 2045. MIC values for ɛ-poly-L-lysine ranged from 6.25 to 12.50 μg/g with MBCs from 12.50 to 25.00 μg/g. Lauric arginate ester at 12.50 μg/g was the MIC and MBC for all strains; 12.50 mL/L was the MIC and MBC for acidic calcium sulfate. Combining nisin with acidic calcium sulfate synergistically inhibited L. monocytogenes; nisin with lauric arginate ester produced additive-type inhibition, while ɛ-poly-L-lysine with acidic calcium sulfate produced antagonistic-type inhibition. Applying nisin along with acidic calcium sulfate should be further investigated for efficacy on RTE meat surfaces. Practical Application: This study demonstrates the potential for combinations of antimicrobials to result in greater pathogen inhibition as compared to the application of a single antimicrobial. The data presented in this study can aid the food industry in developing more efficient and effective application of antimicrobials. These findings should also prompt further studies validating the inhibitory effect of combinations of antimicrobials on ready-to-eat surfaces. 相似文献
559.
560.
Hohmann LJ Eng JK Gemmill A Klimek J Vitek O Reid GE Martin DB 《Analytical chemistry》2008,80(14):5596-5606
Immonium ions have been largely overlooked during the rapid expansion of mass spectrometry-based proteomics largely due to the dominance of ion trap instruments in the field. However, immonium ions are visible in hybrid quadrupole-time-of-flight (QTOF) mass spectrometers, which are now widely available. We have created the largest database to date of high-confidence sequence assignments to characterize the appearance of immonium ions in CID spectra using a QTOF instrument under "typical" operating conditions. With these data, we are able to demonstrate excellent correlation between immonium ion peak intensity and the likelihood of the appearance of the expected amino acid in the assigned sequence for phenylalanine, tyrosine, tryptophan, proline, histidine, valine, and the indistinguishable leucine and isoleucine residues. In addition, we have clearly demonstrated a positional effect whereby the proximity of the amino acid generating the immonium ion to the amino terminal of the peptide correlates with the strength of the immonium ion peak. This compositional information provided by the immonium ion peaks could substantially improve algorithms used for spectral assignment in mass spectrometry analysis using QTOF platforms. 相似文献