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991.
Rapid Determination of Free Fatty Acid in Extra Virgin Olive Oil by Raman Spectroscopy and Multivariate Analysis 总被引:2,自引:0,他引:2
Rasha M. El-Abassy Patrice Donfack Arnulf Materny 《Journal of the American Oil Chemists' Society》2009,86(6):507-511
We introduce a visible Raman spectroscopic method for determining the free fatty acid (FFA) content of extra virgin olive
oil with the aid of multivariate analysis. Oleic acid was used to increase the FFA content in extra virgin olive oil up to
0.80% in order to extend the calibration span. For calibration purposes, titration was carried out to determine the concentration
of FFA for the investigated oil samples. As calibration model for the FFA content (FFA%), a partial least squares (PLS) regression
was applied. The accuracy of the Raman calibration model was estimated using the root mean square error (RMSE) of calibration
and validation and the correlation coefficient (R
2) between actual and predicted values. The calibration curve of actual FFA% obtained by titration versus predicted values
based on Raman spectra was established for different spectral regions. The spectral window (945–1600 cm−1), which includes carotenoid bands, was found to be a useful fingerprint region being statistically significant for the prediction
of the FFA%. High R
2 and small RMSE values for calibration and validation could be obtained, respectively. 相似文献
992.
993.
Andrew W Bristow David C Whitehead John E Cockburn 《Journal of the science of food and agriculture》1992,59(3):387-394
Ten samples of urine from dairy cows, five from sheep and four from goats were analysed to assess the distribution of urinary nitrogen (N) among various chemical constituents in order to gain a better understanding of the reactions undergone by urinary N in soil. Total N in the cow urine ranged from 6.8 to 21.6 g N litre?1, of which an average of 69% was present as urea, 7.3% as allantoin, 5.8% as hippuric acid, 3.7% as creatinine, 2.5% as creatine, 1.3% as uric acid, 0.5% as xanthine plus hypoxanthine, 1.3% as free amino acid N and 2.8% as ammonia. In the sheep urine, total N ranged from 3.0 to 13.7 g litre?1 of which an average of 83 % was present as urea; creatine accounted for 5.3% of the N; hippuric acid and allantoin both accounted for 4.3%, while each of the other constituents amounted to less than 1% of the total N. The goat urine was similar to the sheep urine but with a lower ratio of creatine to creatinine and a somewhat higher proportion (2.0 %) of the total N as amino acid. 相似文献
994.
J. Ahvenainen 《Journal of the Institute of Brewing》1982,88(6):367-370
Aerobically grown pitching yeast is very rich in unsaturated fatty acids and sterol esters compared to traditional, anaerobic yeast. The principal fatty acids in aerobic yeast cells are unsaturated palmitoleic and oleic acids, whereas in anaerobic cells saturated palmitic acid predominates. The difference in fatty acid distribution between aerobic and anaerobic cells is most marked in the sterol esters. The fatty acids of phospho-lipids are more stable, although remarkable differences are observed. The sterols of aerobic cells are almost entirely in esterified form and zymosterol is the principal sterol. During the first hours of fermentation a rapid synthesis of palmitoleic acid is observed when anaerobic yeast is used for pitching and the wort is aerated. The synthesis of oleic acid requires more oxygen and time than is available under normal brewing conditions. When aerobic pitching yeast is used no more unsaturated fatty acids are synthesised and the lipid stores of pitching yeast are distributed among the daughter cells. The decrease in acetate ester production by aerobic pitching yeast is concluded to be due to a decrease in acetyl CoA synthesis, which may be caused by the high proportion of unsaturated fatty acids in membrane lipids. 相似文献
995.
996.
997.
Milk fat production is highly influenced by nutrition and rumen fermentation. Rumination is an essential part of the ruminant digestive process and can serve as an indicator of rumen fermentation. The objective of this research was to quantify variation in rumination time between and within dairy herds and test for relationships between rumination time and milk fat production and fatty acid (FA) profile as a proxy of rumen fermentation. Our hypothesis was that rumination may indicate disruptions to rumen fermentation and that cows that spent less time ruminating would have lower milk fat due to these rumen disruptions. Data were collected from 1,733 Holstein cows on 5 commercial dairy farms (4 in Pennsylvania and 1 in New York) of 200 to 700 head using 1 of 2 commercially-available rumination sensing systems, CowManager SensOor ear tags (Agis Automatisering BV) or SCR model HR-LDn neck collars (SCR Engineers). Rumination data were collected for 7 consecutive days leading up to a DHIA test, summed within day, then averaged to obtain mean daily minutes of rumination time. Milk samples from the DHIA test were analyzed for fat content by mid-infrared spectroscopy and for milk FA profile by gas chromatography. Rumination data were analyzed using multiple linear regression models. Rumination time was related to concentration of specific odd- and branched-chain and trans FA in milk but was not directly related to milk fat concentration. Rumination time also did not contribute to models predicting milk fat concentration after accounting for other cow-level variables. There was a linear relationship between trans-10 C18:1 and rumination time that was positive after accounting for the effect of farm (partial R2 of 2.97% across all data, 4.24% in SCR data, and 2.22% in CowManager data). Although rumination time was not related directly to milk fat, it was associated with differences in trans and odd- and branched-chain FA that have been demonstrated to change during subacute ruminal acidosis or biohydrogenation-induced milk fat depression, which may affect milk fat and other production variables. These associations suggest that further investigation into using rumination data from commercial systems to predict or identify the presence of these conditions is warranted. 相似文献
998.
999.
不同脂肪酶催化亚麻油水解反应性能的比较 总被引:6,自引:1,他引:6
从反应温度、水/亚麻油摩尔比、脂肪酶用量等方面比较了L-lipase和N—1ipase脂肪酶在无溶剂体系中对亚麻油水解反应的催化性能。得到了两种脂肪酶的最佳使用温度及催化亚麻油水解反应的适宜条件。结果表明,两种脂肪酶的最佳用量均为3%~5%,适宜的水/亚麻油摩尔比为30:1。L-lipase和N-lipase的最佳温度分别是35℃和67.5℃,与L-lipase相比,N—1ipase的热稳定性和催化活性相对较高。 相似文献
1000.