全文获取类型
收费全文 | 3564篇 |
免费 | 24篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 5篇 |
综合类 | 3篇 |
化学工业 | 147篇 |
金属工艺 | 14篇 |
机械仪表 | 15篇 |
建筑科学 | 24篇 |
矿业工程 | 4篇 |
能源动力 | 3篇 |
轻工业 | 129篇 |
水利工程 | 19篇 |
石油天然气 | 4篇 |
无线电 | 56篇 |
一般工业技术 | 129篇 |
冶金工业 | 2952篇 |
原子能技术 | 3篇 |
自动化技术 | 82篇 |
出版年
2021年 | 8篇 |
2020年 | 10篇 |
2019年 | 14篇 |
2017年 | 8篇 |
2016年 | 7篇 |
2015年 | 8篇 |
2014年 | 11篇 |
2013年 | 63篇 |
2012年 | 19篇 |
2011年 | 16篇 |
2010年 | 12篇 |
2009年 | 20篇 |
2008年 | 29篇 |
2007年 | 28篇 |
2006年 | 20篇 |
2005年 | 12篇 |
2004年 | 15篇 |
2003年 | 23篇 |
2002年 | 11篇 |
2001年 | 15篇 |
2000年 | 19篇 |
1999年 | 97篇 |
1998年 | 885篇 |
1997年 | 514篇 |
1996年 | 323篇 |
1995年 | 193篇 |
1994年 | 158篇 |
1993年 | 204篇 |
1992年 | 48篇 |
1991年 | 46篇 |
1990年 | 42篇 |
1989年 | 47篇 |
1988年 | 69篇 |
1987年 | 50篇 |
1986年 | 47篇 |
1985年 | 43篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 18篇 |
1981年 | 30篇 |
1980年 | 24篇 |
1979年 | 17篇 |
1978年 | 13篇 |
1977年 | 62篇 |
1976年 | 163篇 |
1975年 | 19篇 |
1974年 | 11篇 |
1973年 | 8篇 |
1972年 | 9篇 |
1967年 | 9篇 |
排序方式: 共有3589条查询结果,搜索用时 31 毫秒
981.
MJ Carella LS Srivastava VV Gossain DR Rovner 《Canadian Metallurgical Quarterly》1993,76(5):1188-1191
"Steroid burst therapy" is commonly used for various acute medical conditions, but its suppressive effect on hypothalamic-pituitary-adrenocortical (HPA) function and the time period for recovery of HPA function is not fully known. We therefore evaluated the HPA function in 10 normal adults before and after a short burst of Prednisone (40 mg/three times daily for 3 days, then tapered over the next 4 days). HPA function was evaluated by iv administration of 100 micrograms of ovine CRH (oCRH) and blood samples for ACTH and cortisol assay were obtained at -30,0,10,15,30,60,90, and 120 min. On another day, 250 micrograms synthetic ACTH (Cosyntropin) were given iv and blood samples for cortisol were obtained at 0,30,60, and 90 min. Basal and peak levels of ACTH and cortisol before and 1,2, and 3 weeks after discontinuation of prednisone in response to oCRH iv are shown below (see Table 1). All values are mean (SEM). Peak levels of cortisol after iv administration of Cosyntropin at week 0 were 922(56.8), week 1 899(63.7), week 2 861(70.9), and week 3 855(53.0). There was no significant difference noted in the levels of ACTH and cortisol in response to oCRH before and after prednisone treatment. Pre- and posttreatment responses of cortisol to Cosyntropin administration were also similar. In addition, cumulative responses (area under the curve) and the change from baseline (delta) before and after administration of prednisone were similar for ACTH and cortisol. We conclude that HPA function is normal 1 week after discontinuation of a short burst of prednisone. These findings suggest that administration of additional steroids may not be required during periods of "stress" for those patients who have previously received similar steroid burst therapy, if at least 1 week has elapsed after such treatment was given. 相似文献
982.
The success obtained by Statistical Pattern Recognition in many disciplines is certainly related to the quality and availability of many data, normally distributed. However, in other disciplines, the data sets consist of few measurements, often binned, correlated, and not normally distributed. Usually, we do not even know which features have an influence on the process. The main goal of this paper is to evaluate the performance of some nonparametric Pattern Recognition algorithms when applied to such data. Finally we show the results of the application of the four nonparametric statistical pattern recognition techniques to real volcanological data. 相似文献
983.
T. L. Mounts K. Warner G. R. List 《Journal of the American Oil Chemists' Society》1981,58(7):A792-A794
The efficacy of tertiary butyl hydroquinone (TBHQ) treatment for enhancement of the storage stability of soybean oil has been
studied by flavor evaluation and chemical analysis. Soybean oils (I) unhydrogenated (IV=137.7; % linolenate=8.3), (II) hydrogenated
with nickel catalyst (IV=109.1; % linolenate=3.3), and (III) hydrogenated with copper-chromium catalyst (IV=112.8, % linolenate=0.4)
were each deodorized. In the cooling stage of the deodorizer, each oil was treated with citric acid plus TBHQ. These freshly
deodorized oils were compared to separate batches of each oil treated with citric acid alone or with citric acid plus butylated
hydroxyanisole and butylated hydroxytoluene. An analytical taste panel performed sensory evaluations by a paired sample test
using an intensity rating scale system. The oils were also evaluated after being subjected to accelerated storage tests (4
days and 8 days at 60 C) and a fluorescent light exposure test (4 hr, ambient temperature). Peroxide development during storage
was beneficially reduced in oils treated with TBHQ. The flavor stability of the three oils was not enhanced by treatment with
TBHQ under any test conditions.
Presented at ISF-AOCS Meeting, New York, NY, April 27–May 1, 1980. 相似文献
984.
Mid-Oleic/Ultra Low Linolenic Acid Soybean Oil: A Healthful New Alternative to Hydrogenated Oil for Frying 总被引:1,自引:0,他引:1
To determine the frying stability of mid-oleic/ultra low linolenic acid soybean oil (MO/ULLSBO) and the storage stability
of food fried in it, tortilla chips were fried in MO/ULLSBO, soybean oil (SBO), hydrogenated SBO (HSBO) and ultra low linolenic
SBO (ULLSBO). Intermittent batch frying tests were conducted up to 55 h of frying, and then tortilla chips were aged up to
4 months at 25 °C. Frying oils were analyzed for total polar compounds to determine the frying stability of the oil. Tortilla
chips were analyzed for hexanal as an indicator of oxidative deterioration and by sensory analysis using a trained, experienced
analytical panel. Results showed no significant differences between the total polar compound levels for MO/ULLSBO and HSBO
after 55 h of frying, indicating a similar fry life. However, total polar compound levels for ULLSBO and SBO were significantly
higher than for either MO/ULLSBO or HSBO, indicating a lower oil fry life. Hexanal levels in aged tortilla chips fried in
SBO were significantly higher than in chips fried in any of the other oils. Tortilla chips fried in MO/ULLSBO and HSBO had
significantly lower hexanal levels than in chips fried in ULLSBO. A sensory analysis of rancid flavor intensity showed similar
trends to those for hexanal formation. The chips fried in SBO had the highest rancid flavor intensity, with significantly
lower hexanal levels in chips fried in HSBO and MO/ULLSBO. Based on these results, MO/ULLSBO not only had a good fry life
but also produced oxidatively stable fried food, and therefore would be a healthful alternative to HSBO.
Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard
of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may
also be suitable. 相似文献
985.
Continuous ultrasonic hydrogenation of soybean oil. II. Operating conditions and oil quality 总被引:1,自引:0,他引:1
K. J. Moulton Sr. S. Koritala K. Warner E. N. Frankel 《Journal of the American Oil Chemists' Society》1987,64(4):542-547
In previous work we found that ultrasonic energy greatly enhanced the rate of hydrogenation of soybean oil. We have now investigated
parameters of ultrasonic hydrogenation and the quality of the resulting products. Refined and bleached soybean oil was hydrogenated
continuously with and without ultrasonic energy at different temperatures, pressures and catalyst concentrations. Flavor and
oxidative stability of the oils were compared with a commercially hydrogenated soybean oil. The extent of hydrogenation (ΔIV)
was not affected by temperature between 245 and 290 C, but was greater at 106 psig than at 65 psig hydrogen pressure. The
ΔIV of hydrogenated oils increased linearly with catalyst concentration from 40 ppm to 150 ppm nickel. At the same catalyst
concentration the IV drop was significantly increased when ultrasonic energy was used. By reducing the amount of power supplied
to the ultrasonic reactor to 40% of full power, the specific power (watts/ΔIV) was lowered by 60%. Linolenate selectivities
and specific isomerization (%trans/ΔIV) remained the same, but linoleate selectivities were lower than for batch hydrogenation under varied operating parameters.
Flavor scores were not significantly different, initially or after storage eight days at 60 C, for oils continuously hydrogenated
with and without ultrasonic energy. Hydrogenation of soybean oil with ultrasonic energy offers a method to produce good quality
products at potentially lower cost than present methods. 相似文献
986.
Jill K. Winkler K. Warner Martin T. Glynn 《Journal of the American Oil Chemists' Society》2007,84(11):1023-1030
The objective of this study was to determine the fate of phytosterols in vegetable oils with varying fatty acid composition
used for frying. High oleic sunflower (HOSun), corn (Corn), hydrogenated soybean (HSBO), expeller pressed soybean (ESBO),
and expeller pressed low-linolenic acid soybean oil (ELLSBO) were used for frying potato chips in a pilot plant-scale continuous
fryer. The same oils, and regular soybean oil (SBO) were also used in intermittent batch frying of tortilla chips. Phytosterols
were measured in oils collected at various times during frying by GC to determine their loss. The formation of polymerized
triacylglycerides (PTAGs) and total polar compounds (TPC) were analyzed to determine the extent of oil degradation. In the
continuous frying system, phytosterol loss ranged between 4 and 6% in ESBO, ELLSBO, HOSun, and Corn, with no loss in HSBO.
PTAGs and TPC were highest in ESBO and ELLSBO, followed by Corn, HOSun, and HSBO. In the batch frying experiment, phytosterol
loss ranged from 1 to 15%, and was highest in Corn followed by SBO and HSBO. There was no significant loss of phytosterols
in ESBO, ELLSBO, and HOSun. Formation of PTAGs and TPC during batch frying was highest in SBO and ESBO, followed by Corn,
ELLSBO, HOSun, and HSBO. In conclusion, phytosterol loss in both the continuous fryer and in the batch frying system appeared
to be unrelated either to fatty acid composition, or to the extent of oil degradation.
Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information
and does not imply recommendation or endorsement by the US Department of Agriculture. 相似文献
987.
Weidong An Jin Ki Hong P. N. Pintauro Kathleen Warner William Neff 《Journal of the American Oil Chemists' Society》1999,76(2):215-222
Soybean oil has been hydrogenated electrochemically in a solid polymer electrolyte (SPE) reactor at 60°C and 1 atm pressure.
These experiments focused on identifying cathode designs and reactor operation conditions that improved fatty acid hydrogenation
selectivities. Increasing oil mass transfer into and out of the Pd-black cathode catalyst layer (by increasing the porosity
of the cathode carbon paper/cloth backing material, increasing the oil feed flow rate, and inserting a turbulence promoter
into the oil feed flow channel) decreased the concentrations of stearic acid and linolenic acid in oil products [for example,
an iodine value (IV) 98 oil contained 12.2% C18:0 and 2.3% C18:3]. When a second metal (Ni, Cd, Zn, Pb, Cr, Fe, Ag, Cu, or Co) was electrodeposited on a Pd-black powder cathode, substantial
increases in the linolenate, linoleate, and oleate selectivities were observed. For example, a Pd/Co cathode was used to synthesize
an IV 113 soybean oil with 5.3% stearic acid and 2.3% linolenic acid. The trans isomer content of soybean oil products was in the range of 6–9.5% (corresponding to specific isomerization indices of 0.15–0.40,
depending on the product IV) and did not increase significantly for high fatty acid hydrogenation selectivity conditions. 相似文献
988.
C. D. Evans K. Warner K. Boundy G. R. List J. C. Cowan J. Dizikes 《Journal of the American Oil Chemists' Society》1974,51(11):509-513
Dried egg mixes prepared commercially with hydrogenated-winterized soybean, corn, or cottonseed oils were evaluated for initial
flavor and for flavor storage stability. Quality evaluations were made on products from two processing plants; flavor, color,
stability, and mix volumes were determined periodically during storage at 100 F for 1 year. All mixes contained 15% of the
specified oil and were air-packaged in 6 oz laminated foil pouches. Replicated triangle flavor tests on reconstituted dried
eggs (scrambled) indicated that neither an analytical-type taste panel nor a palatability panel could distinguish between
the mixes containing the different vegetable oils. All samples, regardless of oil component, deteriorated at ca. the same
rate when stored at elevated temperatures. Minor differences in flavor scores, color indices, and mix volumes were noted in
samples stored at 100 F for 9 or 12 months. A dried egg mix made with hydrogenated-winterized soybean oil could not be distiguished,
after 4 months’ aging at 100 F, from a fresh (unaged) mix made with corn oil. After 6 months’ storage at 100 F all aged mixes,
regardless of the vegetable oil used in their preparation, could be distinguished from the fresh corn oil mix.
Presented at AOCS Meeting, Mexico City, April 1974. 相似文献
989.
G. R. List T. L. Mounts K. Warner A. J. Heakin 《Journal of the American Oil Chemists' Society》1978,55(2):277-279
A lot of commercially extracted crude soybean oil was water degummed with and without a phosphoric acid pretreatment. The
degummed oils were bleached and then deacidified-deodorized in a single step to yield physically (steam) refined soybean salad
oils. Their flavor and oxidative stability were compared to caustic-refined oils given otherwise identical processing treatments.
Physically refined oils without a phosphoric acid pretreatment were of poor initial quality compared to those given the phosphoric
acid pretreatment. However, caustic- and steam-refined oils processed with the phosphoric pretreatment were of comparable
quality.
Presented in part at the AOCS-AACC Symposium, Current Concepts of Food Ingredients, Chicago, March 1977. 相似文献
990.
The linking of atomistic simulations of stress-driven processes to experimentally observed mechanical behavior via the computation of activation energy barriers is a topic of intense current research. Using dislocation nucleation from a crack tip as the reaction process, long-time multiscale molecular dynamics simulations show that the activation barrier can exhibit significant temperature dependence. Using an analytic model for the nucleation process and computing the relevant material properties (elastic constants and stacking fault energies), the temperature dependence is shown to arise primarily from the temperature dependence of the material parameters for both Al and Ni. After thermally activated emission of the first partial dislocation, there is then a competition between two other thermally activated processes: twinning and full dislocation emission. Because the activation barriers depend on temperature, this transition is more complex than usually envisioned. Simulations in Al reveal that a transition from twinning to full dislocation emission back to twinning occurs with increasing temperature, which is counter to traditional metallurgical wisdom. Temperature-dependent activation energies are thus essential to accurate understanding and prediction of those phenomena that control fracture and deformation in metals at realistic loading rates. 相似文献