全文获取类型
收费全文 | 2374篇 |
免费 | 46篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 37篇 |
综合类 | 24篇 |
化学工业 | 483篇 |
金属工艺 | 38篇 |
机械仪表 | 45篇 |
建筑科学 | 77篇 |
矿业工程 | 17篇 |
能源动力 | 38篇 |
轻工业 | 182篇 |
水利工程 | 27篇 |
石油天然气 | 5篇 |
无线电 | 170篇 |
一般工业技术 | 293篇 |
冶金工业 | 613篇 |
原子能技术 | 37篇 |
自动化技术 | 336篇 |
出版年
2021年 | 27篇 |
2020年 | 24篇 |
2019年 | 30篇 |
2017年 | 23篇 |
2016年 | 43篇 |
2015年 | 37篇 |
2014年 | 32篇 |
2013年 | 128篇 |
2012年 | 67篇 |
2011年 | 83篇 |
2010年 | 84篇 |
2009年 | 80篇 |
2008年 | 93篇 |
2007年 | 91篇 |
2006年 | 78篇 |
2005年 | 89篇 |
2004年 | 65篇 |
2003年 | 44篇 |
2002年 | 63篇 |
2001年 | 40篇 |
2000年 | 28篇 |
1999年 | 33篇 |
1998年 | 42篇 |
1997年 | 28篇 |
1996年 | 42篇 |
1995年 | 37篇 |
1994年 | 31篇 |
1993年 | 39篇 |
1992年 | 38篇 |
1991年 | 23篇 |
1990年 | 37篇 |
1989年 | 38篇 |
1988年 | 26篇 |
1987年 | 22篇 |
1986年 | 39篇 |
1985年 | 47篇 |
1984年 | 52篇 |
1983年 | 43篇 |
1982年 | 53篇 |
1981年 | 25篇 |
1980年 | 35篇 |
1979年 | 31篇 |
1978年 | 30篇 |
1977年 | 40篇 |
1976年 | 36篇 |
1975年 | 37篇 |
1974年 | 29篇 |
1973年 | 25篇 |
1972年 | 24篇 |
1969年 | 22篇 |
排序方式: 共有2422条查询结果,搜索用时 0 毫秒
41.
Asserts that in preparing objectives of television programming for children the instructor must (a) recognize the needs and interests of his/her audience and (b) match them to his/her educational purposes. The techniques used to identify and implement methods of attaining the goals of the television programs "Sesame Street" and "The Electric Company" are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
42.
BCI Meeting 2005--workshop on signals and recording methods. 总被引:4,自引:0,他引:4
Jonathan R Wolpaw Gerald E Loeb Brendan Z Allison Emanuel Donchin Omar Feix do Nascimento William J Heetderks Femke Nijboer William G Shain James N Turner 《IEEE transactions on neural systems and rehabilitation engineering》2006,14(2):138-141
This paper describes the highlights of presentations and discussions during the Third International BCI Meeting in a workshop that evaluated potential brain-computer interface (BCI) signals and currently available recording methods. It defined the main potential user populations and their needs, addressed the relative advantages and disadvantages of noninvasive and implanted (i.e., invasive) methodologies, considered ethical issues, and focused on the challenges involved in translating BCI systems from the laboratory to widespread clinical use. The workshop stressed the critical importance of developing useful applications that establish the practical value of BCI technology. 相似文献
43.
Paul F. Mlakar Donald O. Dusenberry James R. Harris Gerald Haynes Long T. Phan Mete A. Sozen 《Canadian Metallurgical Quarterly》2005,19(3):197-205
On September 11, 2001, an airliner was intentionally crashed into the Pentagon. It struck at the first elevated slab on the west wall, and slid approximately 310?ft (94.5?m) diagonally into the building. The force of the collision demolished numerous columns and the fa?ade of the exterior wall, and induced damage to first-floor columns and the first elevated slab over an area approximately 90?ft (27.4?m) wide and 310?ft (94.5?m) long. None of the building collapsed immediately. The portion that remained standing, even after an intense fire, sustained substantial damage at the first-floor level. 相似文献
44.
Paul F. Mlakar Donald O. Dusenberry James R. Harris Gerald Haynes Long T. Phan Mete A. Sozen 《Canadian Metallurgical Quarterly》2005,19(3):206-211
On September 11, 2001, the reinforced concrete structure of the Pentagon Building was able to resist, without collapse, the impact of a large commercial airliner despite the total loss of 26 columns and severe damage to 15 columns at the ground level. The ensuing fire and related fire-fighting activities led to the collapse of a portion of the building approximately one-half hour after the impact. In this paper, the reasons for the demonstrated toughness of the reinforced concrete structure are examined and attributed to use of spiral columns, effective splicing of reinforcing bars, strong girders, and short span lengths. 相似文献
45.
The purpose of this study was to investigate the mediating role of self-efficacy in the development of students' intentions to become entrepreneurs. The authors used structural equation modeling with a sample of 265 master of business administration students across 5 universities to test their hypotheses. The results showed that the effects of perceived learning from entrepreneurship-related courses, previous entrepreneurial experience, and risk propensity on entrepreneurial intentions were fully mediated by entrepreneurial self-efficacy. Contrary to expectations, gender was not mediated by self-efficacy but had a direct effect such that women reported lower entrepreneurial career intentions. The authors discuss practical implications and directions for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
46.
Higher-Order and Symbolic Computation - 相似文献
47.
Christopher T. Chan George A. Kaysen Gerald J. Beck Minwei Li Joan C. Lo Michael V. Rocco Alan S. Kliger 《Hemodialysis international. International Symposium on Home Hemodialysis》2020,24(2):162-174
Background: Frequent hemodialysis modifies serum phosphorus, blood pressure, and left ventricular mass (LVM). We ascertained whether frequent hemodialysis is associated with specific changes in biomarker profile among patients enrolled in the frequent hemodialysis network (FHN) trials. Methods: This was a post hoc analysis of biomarkers among patients enrolled to the FHN trials. In particular, we hypothesized that frequent hemodialysis is associated with changes in a specific set of biomarkers which are linked with changes in blood pressure or LVM. Results: Among 332 randomized patients, 243 had biomarker data available. Of these, 124 patients were assigned to 3‐times‐a‐week hemodialysis (94 [Daily Trial] and 30 [Nocturnal Trial]) and 119 patients were assigned to 6‐times‐a‐week hemodialysis (87 [Daily Trial] and 32 [Nocturnal Trial]). Frequent hemodialysis lowered phosphate, blood pressures, LVM, log fibroblast growth factor (FGF)23, and tissue inhibitors of metalloproteinase (TIMP)—2 levels. The fall in phosphate was associated with changes in FGF23 (r = 0.48, P < 0.001) [Daily Trial] and (r = 0.55, P < 0.001) [Nocturnal Trial]) and tended to be associated with changes in systolic blood pressure (r = 0.18, P = 0.057) [Daily Trial] and (r = 0.31, P = 0.04) [Nocturnal Trial]. Within the Daily Trial, changes in MMP2 (r = 0.20, P = 0.034) were associated with changes in LVM. In the Nocturnal Trial, changes in TIMP‐1 (r = 0.37, P = 0.029) and MMP 9 (r = ?0.38, P = 0.01) were associated with LVM changes. MMP2 changes were associated with changes in systolic blood pressure. Conclusions: Reduction of serum phosphate by frequent hemodialysis may modulate FGF23 levels and systolic blood pressure. Markers of matrix turnover are associated with LVM changes. Frequent hemodialysis may affect pathological mediators of chronic kidney disease‐mineral bone‐metabolism disorder. 相似文献
48.
Integrated real-time dynamic routing (IRR) networks provide dynamic routing features for multiple classes-of-service on an integrated transport network. In a previous Journal paper it is shown that IRR networks allow reduced network management costs since with real-time dynamic routing a number of network operations are simplified or eliminated, leading to savings in operations costs and expenses. In this paper a new algorithm is described for the transport design of IRR networks which achieves near-optimal capacity engineering. In particular, a Karmarkar Algorithm optimal solution to the linear programming flow model achieves approximately a 5 to 8 percentage point reduction in network design cost in comparison to the designs of pre-planned dynamic networks solved with heuristic design techniques. The optimization techniques described in this and the previous Journal paper attain significant capital cost reductions and network performance improvements by properly modeling the more efficient operation of IRR networks. 相似文献
49.
50.
Frank Schwingshandl Max Bodmer Gerald Fox 《电气制造》2010,(3):36-41
时下模块化风机齿轮箱的可靠性是一个普遍存在的问题。为此,Maag开发和试制了一种新型Maag DPPV-7-79齿轮箱,在平衡刚度和柔性的基础上能更好地实现载荷的分配均匀,具有较小的应力和最佳齿轮接触模式。 相似文献