全文获取类型
收费全文 | 3618篇 |
免费 | 132篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 52篇 |
综合类 | 4篇 |
化学工业 | 582篇 |
金属工艺 | 88篇 |
机械仪表 | 62篇 |
建筑科学 | 116篇 |
矿业工程 | 10篇 |
能源动力 | 86篇 |
轻工业 | 231篇 |
水利工程 | 27篇 |
石油天然气 | 13篇 |
无线电 | 382篇 |
一般工业技术 | 496篇 |
冶金工业 | 1209篇 |
原子能技术 | 31篇 |
自动化技术 | 368篇 |
出版年
2022年 | 33篇 |
2021年 | 32篇 |
2020年 | 25篇 |
2019年 | 43篇 |
2018年 | 52篇 |
2017年 | 45篇 |
2016年 | 55篇 |
2015年 | 50篇 |
2014年 | 68篇 |
2013年 | 144篇 |
2012年 | 78篇 |
2011年 | 121篇 |
2010年 | 73篇 |
2009年 | 101篇 |
2008年 | 108篇 |
2007年 | 111篇 |
2006年 | 82篇 |
2005年 | 69篇 |
2004年 | 72篇 |
2003年 | 62篇 |
2002年 | 87篇 |
2001年 | 68篇 |
2000年 | 45篇 |
1999年 | 74篇 |
1998年 | 353篇 |
1997年 | 232篇 |
1996年 | 132篇 |
1995年 | 114篇 |
1994年 | 88篇 |
1993年 | 91篇 |
1992年 | 60篇 |
1991年 | 34篇 |
1990年 | 44篇 |
1989年 | 40篇 |
1988年 | 58篇 |
1987年 | 65篇 |
1986年 | 39篇 |
1985年 | 51篇 |
1984年 | 49篇 |
1983年 | 46篇 |
1982年 | 47篇 |
1981年 | 37篇 |
1980年 | 40篇 |
1979年 | 24篇 |
1978年 | 24篇 |
1977年 | 36篇 |
1976年 | 79篇 |
1974年 | 32篇 |
1973年 | 34篇 |
1969年 | 23篇 |
排序方式: 共有3757条查询结果,搜索用时 31 毫秒
31.
Lutgendorf Susan K.; Russell Daniel; Ullrich Philip; Harris Tamara B.; Wallace Robert 《Canadian Metallurgical Quarterly》2004,23(5):465
This study prospectively examined the relationship between religious attendance, interleukin-6 (IL-6) levels, and mortality rates in a community-based sample of 557 older adults. Attending religious services more than once weekly was a significant predictor of lower subsequent 12-year mortality and elevated IL-6 levels (> 3.19 pg/mL), with a mortality ratio of .32 (95% confidence interval [CI] = 0.15,0.72; p 相似文献
32.
Laura Peters 《集成电路应用》2007,(11):31-31
成品率预测是可制造性设计(DFM)的基础之,但它还远不止于此。IBM系统和技术群300mm半导体运营副总裁DanArmbrust说:“我们精确预测成品率的能力就是我们的经济模式。”Armbrust是SEMICON West 2007成品率论坛讨论DFM现状的三位参与者之一。与他共同参加讨论的是Synopsys公司DFM解决方案副总裁Anantha Sethuraman和Photronics公司的CTO Chris Progler。 相似文献
33.
34.
35.
Specular X-ray reflectivity from SiO2 thin films prepared on silicon substrates by plasma-enhanced chemical vapor deposition showed the films to have a characteristic width of the decay in density at the free surface of 17 Å, to be about three-quarters the density of -quartz, and to have an interfacial layer at the silicon interface that was of the order of 100 Å wide and less dense than the bulk of the film. After chemical-mechanical polishing the characteristic width of the decay in density at the free surface was reduced to 10 Å; furthermore, the near-surface region to a depth of 30 Å had a greater density than the as-deposited film. Off-specular reflectivity confirmed that the decrease in characteristic width at the free surface was due to reduced roughness upon polishing and also revealed that the lateral correlation length in the limit of long wavelengths was the same for both polished and unpolished samples. The compression of the near-surface region during polishing is believed to enhance the dissolution of SiO2 into the slurry which is necessary to achieve smooth surfaces. 相似文献
36.
PA Wallace DE Minnikin K McCrudden A Pizzarello 《Canadian Metallurgical Quarterly》1994,71(2):145-162
Tuberculostearic acid, (R)-10-methyloctadecanoic acid, is a characteristic component of pathogenic mycobacteria and related organisms. Sensitive detection of this acid in infected material allows rapid detection of mycobacterial disease. A novel, convergent synthesis of tuberculostearic acid and key chiral intermediates is described in this communication, to provide a reference compound. Racemic and (R)- and (S)-1-iodo-2-methyldecanes were synthesised from 1-octanal and 1-carboethoxyethylidenetriphenylphosphorane as initial starting materials. 1-Hydroxyoct-7-yne was made from 1,6-hexanediol by two alternative methods and coupled with the above racemic iodide. Hydrogenation and oxidation of the resulting (R,S)-10-methyloctadec-7-yn-1-ol gave racemic tuberculostearic acid. 相似文献
37.
The hydrides of the ternary alloys of CeNi5?xMx (M = Mn or Al and x = 0.5 and 0.75) have been prepared and investigated. The absorption plateau pressure of the system CeNi5—H is reduced 8- to 75-fold, by the replacement of Ni by Mn (or Al), without significantly impairing its hydrogen capacity. This substitution has great influence in reducing the hysteresis effect associated with the hydrogen absorption and desorption. The hysteresis and plateau-sloping factors are very low compared with that in Mischmetal-Ni5 hydride. The enthalpies and entropies of hydrogenation and dehydrogenation for CeNi5?xMx are computed and found to be in the range 20–25 kJ(mole H2)?1) and ~90–100 J(K mole H2)?1, respectively. The high effective entropies of the hydride (high configurational entropy of H in the lattice) are attributed to extensive hydrogen disorder in the interstitial sites of the CeNi5?xMx lattice. Desorption of the hydrogen in the two-phase region (α + β) for CeNi4.25Mn0.75-H follows first-order kinetics with an activation energy of ~33 ± 1 kJ(mole)?1. The favorable physiochemical properties of CeNi5?xMnx-H system make it very attractive for applications. 相似文献
38.
In discussing Waller's paper, we build on his review of medical conditions and the risk of motor vehicle accidents (MVAs) using principles derived from geriatrics, gerontology, and health services research. Three approaches are suggested. The medical model uses discrete diseases as risk factors, but despite its utility and appeal, this model does not sufficiently characterize health and functional status to be the sole approach, and future investigative efforts should at least consider severity of illness concepts. The functional status model emphasizes a functional and physiological approach to health status, but despite its successful application in geriatric assessment and its investigative promise, functional status can be difficult to measure and has not been validated in relation to MVA risk. Finally we consider a behavioral model and within that framework discuss the relation of depressive and other emotional illnesses as well as social vitality to driving patterns and MVA occurrence. 相似文献
39.
40.
OBJECTIVES: In this study, data on violent deaths in the Bronx, New York City, from the 1970, 1980, and 1990 censuses were analyzed. METHODS: The incidence and areal density of intentional deaths were mapped by health area. Simple and stepwise regressions between violent death measures and other factors were performed. RESULTS: The incidence of deaths at levels of those in the highest 1970 quintile spread so that by 1990 only 2 areas saw incidences at levels of the lowest 1970 quintile. Overcrowding, socioeconomic status, population, population change, and drug deaths in simple regressions and overcrowding, socioeconomic status, and low-weight births in stepwise regressions correlated significantly with violent death incidence or density. CONCLUSIONS: Understanding the spatiotemporal development of violence can contribute to public policy on violence. 相似文献