全文获取类型
收费全文 | 5144篇 |
免费 | 96篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 48篇 |
综合类 | 3篇 |
化学工业 | 466篇 |
金属工艺 | 83篇 |
机械仪表 | 94篇 |
建筑科学 | 161篇 |
矿业工程 | 6篇 |
能源动力 | 138篇 |
轻工业 | 307篇 |
水利工程 | 17篇 |
石油天然气 | 12篇 |
无线电 | 352篇 |
一般工业技术 | 650篇 |
冶金工业 | 2473篇 |
原子能技术 | 61篇 |
自动化技术 | 374篇 |
出版年
2022年 | 29篇 |
2021年 | 39篇 |
2020年 | 35篇 |
2019年 | 47篇 |
2018年 | 34篇 |
2017年 | 42篇 |
2016年 | 46篇 |
2015年 | 43篇 |
2014年 | 55篇 |
2013年 | 130篇 |
2012年 | 119篇 |
2011年 | 143篇 |
2010年 | 115篇 |
2009年 | 109篇 |
2008年 | 125篇 |
2007年 | 137篇 |
2006年 | 107篇 |
2005年 | 87篇 |
2004年 | 103篇 |
2003年 | 101篇 |
2002年 | 94篇 |
2001年 | 80篇 |
2000年 | 73篇 |
1999年 | 131篇 |
1998年 | 760篇 |
1997年 | 491篇 |
1996年 | 297篇 |
1995年 | 194篇 |
1994年 | 152篇 |
1993年 | 170篇 |
1992年 | 68篇 |
1991年 | 74篇 |
1990年 | 82篇 |
1989年 | 57篇 |
1988年 | 83篇 |
1987年 | 58篇 |
1986年 | 47篇 |
1985年 | 68篇 |
1984年 | 31篇 |
1983年 | 43篇 |
1982年 | 34篇 |
1981年 | 35篇 |
1980年 | 45篇 |
1979年 | 29篇 |
1978年 | 35篇 |
1977年 | 65篇 |
1976年 | 126篇 |
1975年 | 16篇 |
1974年 | 23篇 |
1973年 | 28篇 |
排序方式: 共有5245条查询结果,搜索用时 0 毫秒
51.
This paper presents work directed at capturing the entrepreneurial and collaborative activity of university researchers. The Triple Helix points to the emergence of the entrepreneurial university as well as to an increasing overlay of activities in universities, industry and government. This study explores ways in which patent-based metrics could be utilized in a Triple Helix context, and how hybrid indicators could be developed by combining patent with survey data. More specifically, it aims to develop indicators that connect technological inventiveness of university researchers to both funding organizations and users, as well as to entrepreneurial activities by academics. The paper develops a simplified model of the innovation process to benchmark the relevance of the indicators to the Triple Helix. An analysis of Finnish academic patents illustrates that patent data can already provide useful indicators but, on its own, cannot provide information about how academic patents are interconnected with government or industry through funding or utilization links. An exclusive analysis of patents can point to patent concentrations on certain universities, to inventors and assignees, or to potential gaps in translating applied science into industrial technology. However, the patent data had to be combined with an inventor survey in order to relate academic patents more to their Triple Helix environment. The survey indicated that most patented academic inventions are connected to (often publicly funded) scientific research by the inventors and tend to be utilized in large firms rather than in start-up companies founded by academic entrepreneurs. 相似文献
52.
53.
We look at the task of computing the time-evolution of a non-linear system for a long time, in our case under random external
influences. Our specific example is the fatigue evaluation of a wind turbine. To facilitate such a computation, we look at
a reduction of the computational effort by projecting everything on a low-dimensional basis. In this case we take the Karhunen-Loève
basis generated from running the model a little while under the random loading. It is important that the error which is caused
by this reduction process can be controlled. We estimate the error by dual or adjoint methods. This in turn allows the process
of model reduction to be performed adaptively.
Dedicated to the memory of Prof. Mike Crisfield, for his cheerfulness and cooperation as a colleague and friend over many
years. 相似文献
54.
55.
Conducted 2 laboratory experiments with 117 undergraduates to examine (1) the effect of assigned goal difficulty on arousal (self-report and heart rate), cognition (perceived norm, self-efficacy strength, and personal goal), and behavioral (task performance) measures and (2) the role of heart rate as a mediator of the goal-difficulty–performance relation. All Ss performed a task requiring cognitive and physical responses. Results of both experiments demonstrate that assigned goal difficulty affected heart rate, cognition, and task performance and that heart rate change was positively related to the cognitive and behavioral measures. Regression analyses suggested that a cognitive–affective mechanism may mediate the goal-difficulty–performance relation. Discussion is focused on the theoretical and practical implications of integrating an arousal concept within goal-setting theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
56.
BACKGROUND: Because the relative efficacy of antiarrhythmic agents on halothane-epinephrine arrhythmias has not been well characterized, this study was undertaken to comparatively evaluate the antiarrhythmic action of Na(+)-, K(+)- and Ca(2+)-channel blockers on epinephrine-induced ventricular arrhythmias during halothane anesthesia in rats. METHODS: Rats were anesthetized at random with either halothane (1.5%), isoflurane (2.0%), or pentobarbital (50 mg/kg intraperitoneally), and the lungs were mechanically ventilated with oxygen. The rats were studied in three consecutive protocols. Protocol I determined the arrhythmogenic thresholds of epinephrine during the three types of anesthesia in 33 rats. Protocol II determined the arrhythmogenic thresholds of epinephrine during halothane anesthesia in 64 rats receiving saline (control) or one of five antiarrhythmic agents. Protocol III measured the duration of epinephrine-induced arrhythmias during halothane anesthesia in 42 rats receiving saline (control) or one of five antiarrhythmic agents. RESULTS: In protocol I, the arrhythmogenic doses of epinephrine during halothane, isoflurane, or pentobarbital anesthesia were 1.7 +/- 3.2, 11.1 +/- 0.6, and 39.0 +/- 3.9 micrograms/kg, respectively, and the corresponding plasma concentrations were 4.3 +/- 0.8, 103.7 +/- 9.2, and 246.7 +/- 28.9 ng/ml, respectively. In protocol II, the arrhythmogenic doses were similar in rats receiving saline and in those receiving lidocaine. The arrhythmogenic doses in rats receiving verapamil, flecainide (Na(+)- and K(+)-channel blocker), E-4031 (K(+)-channel blocker), or amiodarone(K(+)-channel blocker with Na(+)-, Ca(2+)-, and beta-blocking activity) increased significantly, i.e., 4.2, 4.2, 5.5, and 31.7 times control (P < 0.01). In protocol III, lidocaine had no effect on the duration of arrhythmias. Flecainide, E-4031, and verapamil markedly reduced the duration of arrhythmias induced by epinephrine, 8 micrograms/kg intravenously (P < 0.01), whereas only amiodarone markedly reduced the duration of arrhythmias induced by epinephrine, 16 micrograms/kg intravenously (P < 0.01). CONCLUSIONS: It was concluded that agents with K(+)-channel blocking properties were the most effective in preventing halothane-epinephrine arrhythmias in rats. 相似文献
57.
58.
59.
RE Hughes AG Schneeberger KN An BF Morrey SW O''Driscoll 《Canadian Metallurgical Quarterly》1997,6(5):444-448
A retrospective case reference study examining the use of alcohol and tobacco in 303 women aged 40 or over suffering from oral or oropharyngeal cancer was conducted in the south-west Netherlands. Both alcohol and tobacco consumption are important in the development of oral and oropharyngeal cancer with increased consumption of both markedly increasing the risks of cancer, but alcohol having the greater effect. 相似文献
60.
M Meyer B Keweloh K Güth JW Holmes B Pieske SE Lehnart H Just G Hasenfuss 《Canadian Metallurgical Quarterly》1998,30(8):1459-1470
Diastolic dysfunction at high heart rates may be associated with increased myocardial energy consumption. Frequency-dependent changes of isometric force and oxygen consumption (MVO2) were investigated in strip preparations from endstage failing human hearts exhibiting various degrees of diastolic dysfunction. MVO2 was determined by a new method which was validated. When stimulation rate was increased from 40 to 200 min-1 (n=7), developed force decreased from 16.5+/-4.3 to 7.9+/-2.9 mN/mm2 (P<0.01), diastolic force increased from 15.9+/-3.2 to 22.0+/-3.0 mN/mm2 (P<0.01), and total MVO2 increased from 2.6+/-0.6 to 4.7+/-0.9 ml/min/100 g (P<0.025). Resting MVO2 and resting force were 1.8+/-0.4 ml/min/100 g and 15.9+/-3.0 mN/mm2, respectively. After addition of 30 mm 2,3-butanedione monoxime (BDM) to inhibit crossbridges, resting MVO2 and resting force decreased by 46% (P<0.05) and 15% (P<0.01), respectively, indicating the presence of active force generation in unstimulated failing human myocardium. In each muscle preparation, there was a significant correlation between force-time integral (FTI) and total MVO2 (r=0.96+/-0.01). The strength of these correlations did not vary with the contribution of diastolic FTI to total FTI. The ratio of activity related MVO2 to developed FTI, an inverse index of the economy of contraction, increased depending on the rise of diastolic FTI at higher stimulation rates. In conclusion, in failing human myocardium, diastolic force development is occurring at the same energy expenditure as systolic force generation. Therefore, in muscle preparations with disturbed diastolic function economy of contraction decreases with higher stimulation rates, depending on the rise of diastolic force. 相似文献