全文获取类型
收费全文 | 4702篇 |
免费 | 10篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 56篇 |
金属工艺 | 24篇 |
机械仪表 | 8篇 |
建筑科学 | 18篇 |
能源动力 | 10篇 |
轻工业 | 75篇 |
水利工程 | 4篇 |
无线电 | 44篇 |
一般工业技术 | 63篇 |
冶金工业 | 4366篇 |
原子能技术 | 2篇 |
自动化技术 | 39篇 |
出版年
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 17篇 |
2012年 | 8篇 |
2011年 | 15篇 |
2010年 | 12篇 |
2009年 | 16篇 |
2008年 | 29篇 |
2007年 | 20篇 |
2006年 | 13篇 |
2005年 | 18篇 |
2004年 | 20篇 |
2003年 | 17篇 |
2002年 | 18篇 |
2001年 | 14篇 |
2000年 | 6篇 |
1999年 | 143篇 |
1998年 | 1442篇 |
1997年 | 803篇 |
1996年 | 526篇 |
1995年 | 269篇 |
1994年 | 238篇 |
1993年 | 262篇 |
1992年 | 36篇 |
1991年 | 45篇 |
1990年 | 40篇 |
1989年 | 53篇 |
1988年 | 59篇 |
1987年 | 30篇 |
1986年 | 34篇 |
1985年 | 35篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 17篇 |
1981年 | 20篇 |
1980年 | 51篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 92篇 |
1976年 | 196篇 |
1975年 | 12篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1972年 | 2篇 |
1970年 | 6篇 |
排序方式: 共有4712条查询结果,搜索用时 31 毫秒
951.
The Nuclear Regulatory Commission (NRC) published the Maintenance Rule on July 10, 1991 with an implementation date of July 10, 1996 [1]. Maintenance rule implementation at the Duke Power Company has used probabilistic safety assessment (PSA) insights to help focus the monitoring of structures, systems and components (SSC) performance and to ensure that maintenance is effectively performed. This paper describes how the probabilistic risk assessment (PRA)1 group at the Duke Power Company provides support for the maintenance rule by performing the following tasks: (1) providing a member of the expert panel; (2) determining the risk-significant SSCs; (3) establishing SSC performance criteria for availability and reliability; (4) evaluating past performance and its impact on core damage risk as part of the periodic assessment; (5) providing input to the PRA matrix; (6) providing risk analyses of combinations of SSCs out of service; (7) providing support for the SENTINEL program; and (8) providing support for PSA training. These tasks are not simply tied to the initial implementation of the rule. The maintenance rule must be kept consistent with the current design and operation of the plant. This will require that the PRA models and the many PSA calculations performed to support the maintenance rule are kept up-to-date. Therefore, support of the maintenance rule will be one of the primary roles of the PSA group for the remainder of the life of the plant. 相似文献
952.
Gooding JP Holmer SF Carr SN Rincker PJ Carr TR Brewer MS McKeith FK Killefer J 《Meat science》2009,81(2):364-371
To investigate the striping phenomenon in fresh, enhanced pork, a series of experiments were undertaken to identify possible causes of the problem. No one factor (individual brine components, brine pH, ingredient concentration, enhancement pressure, meat and brine pH, or enhancement level) was specifically identified, which could be used to reduce the severity of the striping problem. Furthermore, tumbling the product for 2h, did not reduce the amount of striping, indicating once striping has occurred, it is permanent. Evaluation of the striping pattern indicates that the stripes are formed not only at the needle injection site, but also follow the muscle fiber orientation. The use of darker pork provided more of a contrast when evaluating striping, thus exacerbating the perceived level of striping. 相似文献
953.
Irradiation effects on meat flavor: A review 总被引:3,自引:0,他引:3
Brewer MS 《Meat science》2009,81(1):1-14
Irradiating fresh meat, even at low doses, can result in off-odors and flavors which have been described as rotten egg, bloody, fishy, barbecued corn, burnt, sulfur, metallic, alcohol or acetic acid. The odors vary with the type of meat, temperature during irradiation, oxygen exposure during and/or after the irradiation process, packaging and presence of antioxidative substances. Irradiation can induce formation of isooctane-soluble carbonyl compounds in the lipid fraction and low molecular weight, acid-soluble carbonyls in the protein fraction of meat. Increasing irradiation dose increases these compounds however, cooking reduces them. Among the volatile components, 1-heptene and 1-nonene are influenced most by irradiation dose, and aldehydes (propanal, pentanal, hexanal) are influenced most by packaging type (aerobic vs vacuum). Sulfur-containing volatiles formed from sulfur-containing compounds (primarily amino acids) also contribute to irradiation odor. Dimethyltrisulfide is one of the most potent off-odor compounds, contributing fishy, putrid odors, followed by bismethylthiomethane (sulfurous). Reducing the temperature during the irradiation process reduces the effects on odor/flavor because free radical generation and dispersion are reduced. Ultimately, radiolysis of water into free radical species (OH,H, H(3)0(+), e(aq)(-)) may be the initiators of both lipid oxidation breakdown products and sulfur-containing volatiles responsible for irradiation odor. Methods to decrease the detrimental effects of irradiation include oxygen exclusion (vacuum packaging), replacement with inert gases (nitrogen), addition of protective agents (antioxidants), and post-irradiation storage to allow flavor to return to near-normal levels (re-packaging or double packaging in oxygen permeable film). 相似文献
954.
955.
Wicklund RA Paulson DD Tucker EM Stetzer AJ Desantos F Rojas M Macfarlane BJ Brewer MS 《Meat science》2006,74(4):704-709
The objective of this study was to evaluate the effects of CO-MAP compared to traditional high oxygen MAP (HiOx-MAP) packaging and enhanced with different phosphate on enhanced pork quality. Pork loins were enhanced to 10.5% over initial weight to contain 0.3% salt and 0.4% phosphate (either sodium tripolyphosphate [STP] or a blend of STP and sodium hexametaphosphate) on a finished weight basis. Chops were cut, packaged in atmospheres containing 0.4% CO/30.0% CO2/69.6% N2 (CO-MAP) or 80% O2/20% CO2 (HiOx-MAP), aged in the dark, then placed in a lighted retail display case for 48 h. Chops packaged in CO-MAP were redder (higher Minolta a* values) and darker (lower Minolta b* values) than chops packaged in HiOx-MAP. Based on sensory scores, the CO-MAP chops were pinker than the HiOx chops after cooking. CO-MAP chops also experienced less purge loss than chops in HiOx-MAP. Results indicate that CO-MAP had no effect on flavor or consumer acceptability and only minimal effects on other characteristics. 相似文献
956.
ABSTRACT: The objective of this study was to evaluate the effects of enhancement solutions containing sodium lactate or sodium lactate/sodium diacetate on E. coli K12 transmission to beef strip steaks and in purge. Solutions containing salt, phosphate, and shelf-life enhancers were injected to 10% over initial weight of the steaks. Lactate or lactate/diacetate addition to a solution inoculated with 6 log10 E. coli K12 CFU/mL was equally effective in limiting growth resulting in a 1-2 log10 CFU/g reduction when compared to salt/phosphate in steaks. When inoculation level was 3 log10 CFU/mL in the enhancement solution, microbial growth was detectable only in the purge of steaks enhanced with salt/phosphate only. Lactate increased CIE L* value and b* and decreased a* values when compared to the control. Lactate-/diacetate-containing solutions decreased L* values when compared to lactate alone. Lactate/diacetate also reduced purge loss from steaks compared to lactate and salt/phosphate solutions. 相似文献
957.
Characteristics of Low-fat Beef Patties Formulated with Carbohydrate-Lipid Composites 总被引:1,自引:0,他引:1
G.A. Garzon F.K. Mckeith J.P. Gooding F.C. Felker D.E. Palmquist M.S. Brewer 《Journal of food science》2003,68(6):2050-2056
ABSTRACT: Chemical, physical, and sensory characteristics of low-fat beef patties containing carbohydrate-lipid composites (CLCs) were compared with those of all-beef patties. The CLC gels contained high-amylose cornstarch, maltodextrins, and canola oil. CLC patties had higher moisture, cooking yield, and fat retention than 20%-fat control patties. CLCs improved tenderness and juiciness and decreased cohesiveness of low-fat beef patties compared with 10%-fat control patties. Despite differences in CLC gel firmness, patties made with CLC gels containing corn, potato, and tapioca maltodextrins had similar physical and sensory properties. These results suggest that CLC gels perform well as a partial fat replacer in beef patties while providing flexibility in gel firmness selection. 相似文献
958.
Christian T. Schevey Stoyan Toshkov M. Susan Brewer 《Journal of food science》2013,78(11):S1793-S1799
Antioxidant effects of natural antioxidants in 73%‐lean ground beef patties during refrigeration were studied. Samples were subject to an antioxidant treatment (pomegranate extract, grape seed extract, butylated hydroxyanisole, or no treatment) and an irradiation treatment (0 or 1.5 kGy) before being evaluated for both uncooked and cooked indicators of lipid oxidation. Chemical evaluation of antioxidant activity were determined over 9 d through measurement of thiobarbituric reactive substances values. Physical evaluation of antioxidant activity was monitored by changes in physical color and sensory odor analysis on patties before and after cooking. Butylated hydroxyanisole extended the induction period of oxidation in all unirradiated beef patties better than the natural antioxidants. Panelists were able to distinguish a difference (in terms of oxidation attributes) between patty samples of different antioxidant and irradiation treatments while samples were uncooked, but unable to distinguish a difference between patties after cooking. 相似文献
959.
Preparation of Aluminum Coatings Containing Homogenous Nanocrystalline Microstructures Using the Cold Spray Process 总被引:1,自引:0,他引:1
Nanostructured materials are of widespread interest because of the unique properties they offer. Well-proven techniques, such
as ball milling, exist for preparing powders with nanocrystalline microstructures. Nevertheless, consolidation of nanocrystalline
powders is challenging and presents an obstacle to the use of nanocrystalline metals. This work demonstrates that nanocrystalline
aluminum powders can be consolidated using the cold spray process. Furthermore, transmission electron microscopy (TEM) analysis
of the nanocrystalline cold spray coatings reveals that the cold spray process can cause significant grain refinement. Inert
gas atomized 6061 and 5083 aluminum powders were ball milled in liquid nitrogen resulting in micron-sized powder containing
250-400 nm grains. Cold spray coatings prepared using these feed stock materials exhibited homogenous microstructures with
grain sizes of 30-50 nm. TEM images of the as-received powders, ball-milled powders, and cold spray coatings are shown. 相似文献
960.
Brewer Vickie R.; Fletcher Jack M.; Hiscock Merrill; Davidson Kevin C. 《Canadian Metallurgical Quarterly》2001,15(2):185
Children with congenital hydrocephalus, children with attention deficit-hyperactivity disorder, and normal controls were evaluated with measures of focused attention (Visual Orienting and Detection Task), sustained attention (continuous performance test), and attention shifting (Wisconsin Card Sorting Test). Components from these tasks have been linked to attention systems mediated by anterior or posterior brain networks. Children with congenital hydrocephalus showed an inability to focus and shift attention, which specifically implicated impairment of the disengage and move components of the posterior brain attention system. Children with attention deficit- hyperactivity disorder displayed the expected performance patterns on measures of focused attention once their difficulties with sustained attention were taken into account. However, they showed problems with shifting and sustaining attention, which are commonly associated with the anterior brain attention system. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献