全文获取类型
收费全文 | 1145篇 |
免费 | 51篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 218篇 |
金属工艺 | 10篇 |
机械仪表 | 5篇 |
建筑科学 | 37篇 |
能源动力 | 14篇 |
轻工业 | 147篇 |
水利工程 | 11篇 |
石油天然气 | 7篇 |
无线电 | 66篇 |
一般工业技术 | 177篇 |
冶金工业 | 399篇 |
原子能技术 | 1篇 |
自动化技术 | 96篇 |
出版年
2023年 | 11篇 |
2022年 | 23篇 |
2021年 | 40篇 |
2020年 | 29篇 |
2019年 | 22篇 |
2018年 | 22篇 |
2017年 | 31篇 |
2016年 | 27篇 |
2015年 | 24篇 |
2014年 | 41篇 |
2013年 | 57篇 |
2012年 | 61篇 |
2011年 | 82篇 |
2010年 | 65篇 |
2009年 | 49篇 |
2008年 | 83篇 |
2007年 | 58篇 |
2006年 | 67篇 |
2005年 | 59篇 |
2004年 | 48篇 |
2003年 | 27篇 |
2002年 | 31篇 |
2001年 | 17篇 |
2000年 | 28篇 |
1999年 | 23篇 |
1998年 | 24篇 |
1997年 | 25篇 |
1996年 | 23篇 |
1995年 | 12篇 |
1994年 | 13篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有1196条查询结果,搜索用时 31 毫秒
61.
Tenderness, ageing rate and meat quality of pork M. longissimus thoracis et lumborum after accelerated boning 总被引:1,自引:0,他引:1
The impact of accelerated boning on tenderness, ageing rate and meat quality of pork longissimus muscle was investigated. Accelerated boning of eight Large White×Landrace pork carcasses at 30 min post-mortem followed by chilling at 0°C resulted in tougher pork with higher drip loss and a darker surface lightness relative to conventional boning at 24 h post-mortem. The increased toughness was still observed at 4 days post-mortem, a time by which 80% of ageing generally had occurred as seen in experiment 2. The increased toughness could be attributed to cold shortening and a reduction in proteolysis. 相似文献
62.
The sensitive detection and characterization of carbohydrates by means of a strategy based on surface-enhanced Raman spectroscopy is demonstrated. Spectra are obtained after injecting a small amount of saccharide solution onto a roughened silver substrate, with subsequent deposition of silver colloid. The sensitivity achieved by this two-step approach enables high-quality Raman spectra to be obtained for small amounts of aqueous saccharides (5 microL of a 10(-2) M solution) utilizing minimal laser power and small signal acquisition times (a few seconds). Spectral "fingerprints" obtained for seven structurally similar monosaccharides demonstrate clearly an effective means by which each sugar can be identified. The application to more complex analyses is demonstrated for monosaccharide mixtures and a disaccharide, whereby the SERS fingerprints aid in the determination of components. 相似文献
63.
This study is a preliminary exploration of how individual differences in gender role attitudes and ethnic identity might be related to career decision self-efficacy and the gender traditionality of career choice goals in a sample of 102 9th-grade Black and Latina girls. Extending social-cognitive career theory, the authors examined 2 path models in which career decision self-efficacy mediated the effects of gender role attitudes and ethnic identity on the traditionality of the participants' career choice goals. Models depicting full and partial mediation were considered. The results of the path analyses provided confirmation for an extension of the social- cognitive career theory model, indicating that for this sample, career decision self-efficacy fully mediated the influence of egalitarian gender role attitudes and ethnic identity on gender traditionality in career choice goals. These findings offer support for consideration of the role of gender role attitudes and ethnic identity in career self-exploration and vocational guidance with Black and Latina girls. Limitations, implications for counseling, and suggestions for future research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
64.
Neighbors Clayton; Lewis Melissa A.; Bergstrom Rochelle L.; Larimer Mary E. 《Canadian Metallurgical Quarterly》2006,25(5):571
The objectives of this research were to evaluate the efficacy of computer-delivered personalized normative feedback among heavy drinking college students and to evaluate controlled orientation as a moderator of intervention efficacy. Participants (N = 217) included primarily freshman and sophomore, heavy drinking students who were randomly assigned to receive or not to receive personalized normative feedback immediately following baseline assessment. Perceived norms, number of drinks per week, and alcohol-related problems were the main outcome measures. Controlled orientation was specified as a moderator. At 2-month follow-up, students who received normative feedback reported drinking fewer drinks per week than did students who did not receive feedback, and this reduction was mediated by changes in perceived norms. The intervention also reduced alcohol-related negative consequences among students who were higher in controlled orientation. These results provide further support for computer-delivered personalized normative feedback as an empirically supported brief intervention for heavy drinking college students, and they enhance the understanding of why and for whom normative feedback is effective. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
65.
The use of a network of shared, heterogeneous workstations each harboring a reconfigurable computing (RC) system offers high performance users an inexpensive platform for a wide range of computationally demanding problems. However, effectively using the full potential of these systems can be challenging without the knowledge of the system's performance characteristics. While some performance models exist for shared, heterogeneous workstations, none thus far account for the addition of RC systems. Our analytic performance model includes the effects of the reconfigurable device, application load imbalance, background user load, basic message passing communication, and processor heterogeneity. The methodology proves to be accurate in characterizing these effects for applications running on shared, homogeneous, and heterogeneous HPRC resources. The model error in all cases was found to be less than 5% for application runtimes greater than 30 s, and less than 15% for runtimes less than 30 s. 相似文献
66.
67.
The effects of varying gossypol intake from whole cottonseed and cottonseed meal on lactation and blood parameters in lactating dairy cows 总被引:1,自引:0,他引:1
Effects of varying amounts of gossypol from whole Upland cottonseed (WCS) and cottonseed meal (CSM) were evaluated in 40 midlactation Holstein cows. After 14 d of pretreatment, cows were assigned to 1 of the 5 treatments for 84 d: control (no gossypol), 931 mg/kg total gossypol (TG) and 850 mg/kg free gossypol (FG) from WCS (moderate TG and high FG); 924 mg/kg TG and 91 mg/kg FG from CSM (moderate TG and low FG), 945 mg/kg TG and 479 mg/kg FG with equal amounts of TG from WCS and CSM (moderate TG and FG), or 1894 mg/kg TG and 960 mg/kg FG with equal amounts of TG from WCS and CSM (high TG and FG). Concentrations of plasma gossypol (PG) and its isomers were directly proportional to FG intake. Concentrations of PG reached a plateau after 28 d on treatment, and they were highest in cows receiving a diet with high TG and FG. Erythrocyte fragility differed among treatments and increased with increasing FG intake. Plasma gossypol returned to negligible concentrations 28 d after withdrawal of cottonseed products from the high TG and FG diet. Serum vitamin A was similar among treatments, but vitamin E increased with increasing FG intake. Serum enzymes were generally unaffected by treatments, but urea N increased in diets higher in TG and FG. Intake of dry matter was higher for the diet high in TG and FG than for the control diet, but was similar for other treatments. Cows receiving the high TG and FG diet produced more milk and 3.5% fat-corrected milk, with no changes in milk composition. Feeding a diet containing 1894 mg/kg TG and 960 mg/kg FG for 84 d increased PG concentrations and erythrocyte fragility and resulted in minor changes in blood metabolites and enzymes, but no detrimental effect on lactation performance was observed. Indicators of liver, kidney, and muscle cell viability suggest that the higher amounts of gossypol consumed in this study had only minor effects on those tissues in lactating dairy cows. 相似文献
68.
Ruckart PZ Borders J Villanacci J Harris R Samples-Ruiz M 《Journal of hazardous materials》2004,115(1-3):27-31
High winds, flooding, lightning, and other phenomena associated with adverse weather can cause power failures, equipment damage, and process upsets resulting in chemical releases. Of the 5000 events in Texas that were reported to the Hazardous Substances Emergency Events Surveillance (HSEES) system during 2000-2001, adverse weather conditions contributed to 110 (2%) events. Rain was the most frequent adverse weather condition. Most events to which adverse weather conditions contributed occurred during June or September; these months correspond with the high temperature and hurricane season in Texas. Most events occurred in coastal counties with large numbers of industrial facilities. Three industries reported the majority of events: industrial and miscellaneous chemicals manufacturing; petroleum refining; and plastics, synthetics, and resin manufacturing. Power failures were associated more often with adverse weather-related events than with nonweather-related events. Releases occurred most commonly from ancillary process equipment and process vessels. Events associated with adverse weather-related conditions involved nine victims. System and process design improvements, such as improved backup power generation and redesigned secondary containment systems, could be explored to reduce the potential negative effects of severe weather. 相似文献
69.
Security in the wild: user strategies for managing security as an everyday,practical problem 总被引:1,自引:0,他引:1
Paul?DourishEmail author Rebecca?E.?Grinter Jessica?Delgado de la Flor Melissa?Joseph 《Personal and Ubiquitous Computing》2004,8(6):391-401
Ubiquitous and mobile technologies create new challenges for system security. Effective security solutions depend not only on the mathematical and technical properties of those solutions, but also on people’s ability to understand them and use them as part of their work. As a step towards solving this problem, we have been examining how people experience security as a facet of their daily life, and how they routinely answer the question, “is this system secure enough for what I want to do?” We present a number of findings concerning the scope of security, attitudes towards security, and the social and organizational contexts within which security concerns arise, and point towards emerging technical solutions. 相似文献
70.
Experimental results show that, among 76 female and 83 male undergraduates, the sex of the individual described as having engaged in suicidal behavior tended to produce a significant difference in the degree of inferred intentionality, with suicidal females being seen as having greater suicidal intentionality than males. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献