全文获取类型
收费全文 | 29147篇 |
免费 | 3682篇 |
国内免费 | 2210篇 |
专业分类
电工技术 | 3541篇 |
技术理论 | 5篇 |
综合类 | 3200篇 |
化学工业 | 1877篇 |
金属工艺 | 1395篇 |
机械仪表 | 1619篇 |
建筑科学 | 5542篇 |
矿业工程 | 1799篇 |
能源动力 | 864篇 |
轻工业 | 1608篇 |
水利工程 | 1966篇 |
石油天然气 | 1400篇 |
武器工业 | 329篇 |
无线电 | 1351篇 |
一般工业技术 | 3407篇 |
冶金工业 | 1685篇 |
原子能技术 | 342篇 |
自动化技术 | 3109篇 |
出版年
2024年 | 182篇 |
2023年 | 466篇 |
2022年 | 1027篇 |
2021年 | 1254篇 |
2020年 | 1264篇 |
2019年 | 1070篇 |
2018年 | 985篇 |
2017年 | 1099篇 |
2016年 | 1322篇 |
2015年 | 1289篇 |
2014年 | 2155篇 |
2013年 | 2230篇 |
2012年 | 2326篇 |
2011年 | 2389篇 |
2010年 | 1808篇 |
2009年 | 1841篇 |
2008年 | 1674篇 |
2007年 | 1823篇 |
2006年 | 1781篇 |
2005年 | 1296篇 |
2004年 | 1090篇 |
2003年 | 935篇 |
2002年 | 752篇 |
2001年 | 555篇 |
2000年 | 431篇 |
1999年 | 360篇 |
1998年 | 292篇 |
1997年 | 239篇 |
1996年 | 188篇 |
1995年 | 157篇 |
1994年 | 122篇 |
1993年 | 96篇 |
1992年 | 91篇 |
1991年 | 65篇 |
1990年 | 59篇 |
1989年 | 56篇 |
1988年 | 47篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 28篇 |
1984年 | 20篇 |
1983年 | 21篇 |
1982年 | 12篇 |
1980年 | 9篇 |
1979年 | 19篇 |
1963年 | 7篇 |
1961年 | 8篇 |
1960年 | 6篇 |
1959年 | 8篇 |
1955年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
MA Gui-shengSenior Engineer Comprehensive Reconnaissance Bureau Changjiang Water Resources Commission Wuhan China 《人民长江》2002,(Z1)
1 IntroductionBecauseofthecomplicatedsubsoilprofile ,theleveealongmiddleandlowerreachesofYangtze ,about 36 0 0kmlong ,hasmanyhiddenperils .Amongthedangerouseventsduring 1998’sfloodseasoninthewholevalley ,12 .7%oc curredalongthetrunkstreamdykes,ofwhich 6 98werethemostd… 相似文献
52.
Wang Hai-dou Xu Bin-shi Wei Shi-cheng Zhang Xian-cheng Jin Guo Jiang Yi 《中南工业大学学报(英文版)》2005,12(2):30-33
The guide-pieces, used in the process line of steel rolling, were the important components. The guidepieces, which were slide
contacting with the rolled-piece, had a high temperature and high speed. The wear was very serious. The results from failure
analysis showed that there were three failure forms in the guide-pieces: the first was the wear during heat friction, the
second was the heat fatigue under the cycle of deep heating and deep cooling, and the third was the impact rupture. Among
them, the wear was the main reason. To the wear of guidepieces, there were four mechanisms, namely abrasive wear, adhesive
wear, fatigue wear and corrosion wear. The failure analysis to the guide-piece laid the foundation for its remanufacturing.
Foundation item: Project(50235030) supported by the National Natural Science Foundation of China 相似文献
53.
One of the new physical methods that provides much information about the processes going on in a friction contact zone in real time is acoustic emission (AE). Basic experimental results of AE in friction are presented and analysed. Using AE signals we can get an indication about the state of the friction processes, about the quality of solid and liquid layers on the contacting surfaces in real time, sometimes about intensity of wear, changing of wear and friction regimes and so on. The influence of sliding velocity, load, roughness and some physical and mechanical properties of the body on the parameters of AE are also given. Some attention to the practical implementation of these techniques for control of capability for work of friction pairs in real conditions are given. Modern methods and devices enable condition monitoring of sliding and rolling bearings. 相似文献
54.
Norris Fran H.; Murphy Arthur D.; Baker Charlene K.; Perilla Julia L.; Rodriguez Francisco Gutiérrez; Rodriguez José de Jesús Gutiérrez 《Canadian Metallurgical Quarterly》2003,112(4):646
Prevalence rates of trauma and posttraumatic stress disorder (PTSD) were estimated from a probability sample of 2,509 adults from 4 cities in Mexico. PTSD was assessed according to Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1994) criteria using the Composite International Diagnostic Interview (CIDI; WHO, 1997). Lifetime prevalence of exposure and PTSD were 76% and 11.2%, respectively. Risk for PTSD was highest in Oaxaca (the poorest city), persons of lower socioeconomic status, and women. Conditional risk for PTSD was highest following sexual violence, but nonsexual violence and traumatic bereavement had greater overall impact because of their frequency. Of lifetime cases, 62% became chronic; only 42% received medical or professional care. The research demonstrates the importance of expanding the epidemiologic research base on trauma to include developing countries around the world. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
56.
57.
58.
Pulkki-R?back Laura; Elovainio Marko; Kivim?ki Mika; Raitakari Olli T.; Keltikangas-J?rvinen Liisa 《Canadian Metallurgical Quarterly》2005,24(3):307
This study examined associations of temperament at ages 6 to 12 with body-mass index (BMI) and waist circumference (WC) at ages 24 to 30 years. The participants were 619 men and women derived from the population-based Cardiovascular Risk in Young Finns Study. Temperament was operationalized as (negative) emotionality, sociability, and activity. High emotionality predicted increased BMI, independently of WC, and independently of childhood and adulthood risk factors for adult obesity. None of the temperament dimensions had any associations with WC after controlling for BMI. The findings suggest that temperamental difficulty in childhood may be a useful risk indicator for general body mass in adulthood, and the mechanisms relating temperament with body mass should be further explored. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
59.
Investigations of water inrushes from aquifers under coal seams 总被引:6,自引:0,他引:6
In many coal mines, limestone-confined aquifers underlie coal seams. During coal extraction from these mines, water inrushes occur frequently with disastrous consequences. This paper introduces the hydrogeological conditions of the coal mines and the potential water inrush disasters from aquifers under coal seams. It then presents the water inrush mechanism. The main factors which control water inrushes include strata pressure, mining size, geologic structures and the water pressure in the underlying aquifer. Analysis shows that reduction of confinement due to mining is the major cause of the water-conducting failure in the floor strata. The depth of the failure zone is strongly dependent on the mining width. This paper also presents field observation results of the water-conducting failure in the floor strata, and applies the finite element method coupled with stress-dependent permeability to analyze hydraulic conductivity enhancement due to coal extraction. Finally, theoretical and empirical methods to predict water inrushes are given, and technical measures for improving mine design and safety for coal extraction over aquifers are presented. These measures include fault and fracture grouting and mining method modification such as changing long-wall to short-wall mining. 相似文献
60.