全文获取类型
收费全文 | 3951篇 |
免费 | 95篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 51篇 |
化学工业 | 540篇 |
金属工艺 | 70篇 |
机械仪表 | 66篇 |
建筑科学 | 123篇 |
矿业工程 | 4篇 |
能源动力 | 92篇 |
轻工业 | 280篇 |
水利工程 | 21篇 |
石油天然气 | 3篇 |
无线电 | 358篇 |
一般工业技术 | 608篇 |
冶金工业 | 1187篇 |
原子能技术 | 47篇 |
自动化技术 | 598篇 |
出版年
2022年 | 22篇 |
2021年 | 26篇 |
2019年 | 34篇 |
2018年 | 44篇 |
2017年 | 48篇 |
2016年 | 34篇 |
2015年 | 40篇 |
2014年 | 75篇 |
2013年 | 182篇 |
2012年 | 77篇 |
2011年 | 120篇 |
2010年 | 105篇 |
2009年 | 104篇 |
2008年 | 110篇 |
2007年 | 124篇 |
2006年 | 91篇 |
2005年 | 82篇 |
2004年 | 82篇 |
2003年 | 94篇 |
2002年 | 86篇 |
2001年 | 91篇 |
2000年 | 85篇 |
1999年 | 95篇 |
1998年 | 329篇 |
1997年 | 193篇 |
1996年 | 157篇 |
1995年 | 108篇 |
1994年 | 99篇 |
1993年 | 97篇 |
1992年 | 56篇 |
1991年 | 56篇 |
1990年 | 51篇 |
1989年 | 58篇 |
1988年 | 55篇 |
1987年 | 53篇 |
1986年 | 35篇 |
1985年 | 45篇 |
1984年 | 61篇 |
1983年 | 53篇 |
1982年 | 44篇 |
1981年 | 49篇 |
1980年 | 52篇 |
1979年 | 56篇 |
1978年 | 42篇 |
1977年 | 56篇 |
1976年 | 94篇 |
1975年 | 41篇 |
1974年 | 33篇 |
1972年 | 24篇 |
1966年 | 22篇 |
排序方式: 共有4048条查询结果,搜索用时 0 毫秒
991.
Chrisantha T. Fernando Anthony M.L. Liekens Lewis E.H. Bingle Christian Beck Thorsten Lenser Dov J. Stekel Jonathan E. Rowe 《Journal of the Royal Society Interface》2009,6(34):463-469
We demonstrate how a single-celled organism could undertake associative learning. Although to date only one previous study has found experimental evidence for such learning, there is no reason in principle why it should not occur. We propose a gene regulatory network that is capable of associative learning between any pre-specified set of chemical signals, in a Hebbian manner, within a single cell. A mathematical model is developed, and simulations show a clear learned response. A preliminary design for implementing this model using plasmids within Escherichia coli is presented, along with an alternative approach, based on double-phosphorylated protein kinases. 相似文献
992.
Michele A. Lewis Magali S. Ferrandon David F. Tatterson Paul Mathias 《International Journal of Hydrogen Energy》2009,34(9):4136-4145
This is the third in a series of papers on alternative cycle evaluation. Part I described the evaluation methodology. Part II described the down-selection process where the most promising of the nine alternative cycles was determined. The Cu–Cl cycle was selected for further development because it alone meets the four criteria used. The current results indicate that the cycle is chemically viable, feasible with respect to engineering, energy-efficient, and capable of meeting DOE's timeline for an Integrated Laboratory Scale (ILS) demonstration. All of the reactions have been proven and the remaining technical challenges should be met with current technologies. The maximum temperature requirement is around 550 °C (823 K), which can be obtained with a variety of heat sources. The lower temperature should mitigate the demands on the materials of construction. This paper, Part III, describes the procedure used to develop the Cu–Cl cycle beyond the relatively simple Level 3 efficiency calculation completed by the universities. The optimization process consisted of (i) updating the thermodynamic database used in the Aspen Plus® simulation, (ii) developing a robust flowsheet and optimizing the energy usage therein, (iii) designing a conceptual process incorporating the Aspen Plus® mass and energy flows, and then (iv) estimating the hydrogen production costs. The results presented here are preliminary because further optimization is ongoing. 相似文献
993.
Lewis Erin E.; Dozier Mary; Ackerman John; Sepulveda-Kozakowski Sandra 《Canadian Metallurgical Quarterly》2007,43(6):1415
This study assessed relations among placement instability, inhibitory control, and caregiver-rated child behavior. The sample included 33 adopted children who had experienced placement instability, 42 adopted children who had experienced 1 stable placement, and 27 children never placed in foster care. Five- and 6-year-old children completed the day-night task, which requires children to inhibit a prepotent response, and a control task that presents similar memory demands but does not require inhibition (C. L. Gerstadt, Y. J. Hong, & A. Diamond, 1994). Adopted children who had experienced placement instability performed worse on the inhibition task than did both other groups of children, when the authors controlled for age, verbal intelligence (as measured with the Wechsler Preschool and Primary Scale of Intelligence--Revised; D. Wechsler, 1989; or the Peabody Picture Vocabulary Test--Third Edition; L. M. Dunn & L. M. Dunn, 1997), and control task performance (p.05). These results suggest that placement instability may adversely affect the social-emotional development of adopted children. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
994.
Lewis D. Pouget V. Beaudoin F. Haller G. Perdu P. Fouillat P. 《Semiconductor Manufacturing, IEEE Transactions on》2005,18(2):279-288
Several test vehicles were designed in order to validate laser-based failure analysis and process validation techniques. Two vehicles concern defect localization in integrated circuits (ICs); the third one is designed for single event upset sensitivity study in digital ICs. 相似文献
995.
A fibre-optic sensor for the monitoring of hazardous exhaust gases is described. The sensor based on ultraviolet (UV) differential optical absorption spectroscopy (DOAS) was developed for the simultaneous monitoring of several exhaust gases from passenger cars. Experimental results describing the operation of this sensor with calibrated cylinder gases as well as in a full-size engine are presented. The sensor has been developed to operate within an exhaust environment and have low susceptibility to interferences from other gases present. The lower limit of detection for the sensor was found to be 5 ppm for nitric oxide (NO), 1 ppm for both nitrogen dioxide (NO2) and sulphur dioxide (SO2) and response time was found to be 3.4 s. 相似文献
996.
Duggal A.R. Heller C.M. Shiang J.J. Jie Liu Lewis L.N. 《Display Technology, Journal of》2007,3(2):184-192
In this paper, the vapor-deposited and solution-processed organic light-emitting diode (OLED) technology development paradigms are described and then compared with respect to their prospects for enabling general lighting applications. Two key development needs are improved device efficiency and lower cost fabrication methods. Progress in these areas for solution-processed OLEDs is illustrated by describing recent methods for attaining high efficiency blue emission and introducing novel low cost process methods for device fabrication which enable high performance devices without the need for any vacuum processing steps 相似文献
997.
Following the actuation of safety-relief valves in BWR nuclear power plants, first water then air and steam are cleared from the discharge lines through quencher devices into a suppression pool. This clearing results in water spike, air bubble, and condensation pressure loads applied to structures in the pool, and the surrounding containment vessel.The Leibstadt Nuclear Power Plant has the only free-standing steel Mark III containment vessel in the world. All other steel Mark III containment vessels have concrete backing in the suppression pool region, which dampens clearing load responses. As such, it is of interest to note how this steel vessel responds to discharge pressures, and compare these responses to analytically predicted results.The purpose of this paper is to compare the analytical results used to design the steel containment vessel with the responses measured during in-plant testing. The analytical methods considered the effects of fluid-structure interaction. The test program included initial and consecutive actuations of a single valve, and initial actuation of multiple (four) valves. The conclusion of the comparison is that, in general, there are large conservatisms in the analytical predictions versus measured responses. 相似文献
998.
Ronghu Chi Danwei Wang Frank L. Lewis Zhongsheng Hou Shangtai Jin 《Asian journal of control》2015,17(3):952-962
Terminal iterative learning control (TILC) has been developed to reduce the error between system output and a fixed desired point at the terminal end of operation interval over iterations. In this work, the desired terminal point is not fixed but allowed to change run‐to‐run among a set of fixed points and a new adaptive terminal iterative learning control scheme is developed to achieve learning objective over iterations. The control signal is updated from the measured terminal value at the end of a run, instead of the whole output trajectory. Although the reference terminal point is iteration‐varying, the new adaptive TILC guarantees that the tracking error converges to zero iteratively. Both rigorous mathematical analysis and simulation results confirm the applicability and effectiveness of the proposed approach. 相似文献
999.
Andrew Stranieri John Zeleznikow Mark Gawler Bryn Lewis 《Artificial Intelligence and Law》1999,7(2-3):153-183
Few automated legal reasoning systems have been developed in domains of law in which a judicial decision maker has extensive discretion in the exercise of his or her powers. Discretionary domains challenge existing artificial intelligence paradigms because models of judicial reasoning are difficult, if not impossible to specify. We argue that judicial discretion adds to the characterisation of law as open textured in a way which has not been addressed by artificial intelligence and law researchers in depth. We demonstrate that systems for reasoning with this form of open texture can be built by integrating rule sets with neural networks trained with data collected from standard past cases. The obstacles to this approach include difficulties in generating explanations once conclusions have been inferred, difficulties associated with the collection of sufficient data from past cases and difficulties associated with integrating two vastly different paradigms. A knowledge representation scheme based on the structure of arguments proposed by Toulmin has been used to overcome these obstacles. The system, known as Split Up, predicts judicial decisions in property proceedings within family law in Australia. Predictions from the system have been compared to those from a group of lawyers with favourable results. 相似文献
1000.
BACKGROUND: This is the first report on the use of intra-arterial papaverine and percutaneous transluminal angioplasty in two patients with severe, symptomatic cerebral vasospasm who suffered ruptured arteriovenous malformations (AVMs). CASE DESCRIPTIONS: The source of hemorrhage was a venous aneurysm in the first case and a pedicular aneurysm of the distal posterior inferior cerebellar artery in the second case. In both cases, the AVMs were located in the superior vermis and there was minimal subarachnoid hemorrhage. The first patient underwent removal of the AVM before the period of cerebral vasospasm and the second patient underwent removal of the AVM after the cerebral vasospasm had resolved. The outcome was excellent in the first patient and poor in the second patient. CONCLUSION: Arteriovenous malformation with ruptured aneurysms may be at high risk for cerebral vasospasm even when there is minimal subarachnoid hemorrhage. We recommend early treatment of AVMs with ruptured pedicular, intranidal, or venous aneurysms to avoid rebleeding and to allow for aggressive treatment of cerebral vasospasm. The management of cerebral vasospasm after AVM rupture is discussed. 相似文献