全文获取类型
收费全文 | 2905篇 |
免费 | 112篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 20篇 |
综合类 | 4篇 |
化学工业 | 584篇 |
金属工艺 | 51篇 |
机械仪表 | 68篇 |
建筑科学 | 233篇 |
矿业工程 | 7篇 |
能源动力 | 146篇 |
轻工业 | 300篇 |
水利工程 | 47篇 |
石油天然气 | 5篇 |
无线电 | 195篇 |
一般工业技术 | 507篇 |
冶金工业 | 308篇 |
原子能技术 | 35篇 |
自动化技术 | 509篇 |
出版年
2023年 | 28篇 |
2022年 | 53篇 |
2021年 | 57篇 |
2020年 | 44篇 |
2019年 | 53篇 |
2018年 | 65篇 |
2017年 | 56篇 |
2016年 | 76篇 |
2015年 | 65篇 |
2014年 | 92篇 |
2013年 | 181篇 |
2012年 | 159篇 |
2011年 | 175篇 |
2010年 | 154篇 |
2009年 | 138篇 |
2008年 | 164篇 |
2007年 | 140篇 |
2006年 | 137篇 |
2005年 | 127篇 |
2004年 | 117篇 |
2003年 | 88篇 |
2002年 | 92篇 |
2001年 | 43篇 |
2000年 | 45篇 |
1999年 | 51篇 |
1998年 | 82篇 |
1997年 | 66篇 |
1996年 | 45篇 |
1995年 | 33篇 |
1994年 | 33篇 |
1993年 | 33篇 |
1992年 | 20篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 22篇 |
1988年 | 23篇 |
1987年 | 12篇 |
1986年 | 16篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1978年 | 9篇 |
1976年 | 16篇 |
1943年 | 16篇 |
1942年 | 12篇 |
1941年 | 8篇 |
1940年 | 9篇 |
1939年 | 7篇 |
排序方式: 共有3019条查询结果,搜索用时 0 毫秒
991.
Griebel J. Großfeld Schwaibold E. Dinslage Schormüller Kanitz W. Ludorff W. Schreiber O. Windhausen Beckel M. Gordienko K. Höll G. Steinhoff Konrad Lang J. J. van Eck Diemair W. Sutthoff H. Mohler Rudolf Abderhalden Bäurle H. J. Steinbeck G. Steinhoff Pawletta Damm W. Hämmerle Lars Erlandsen W. Bartels Brüning Jesser Bames Kluge Rob Jungkunz W. Preiß C. Pyriki K. Müller Fr. Bartschat Jahr und A. Hanak 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1939,77(5):493-560
Ohne Zusammenfassung 相似文献
992.
993.
Bergman D.I. Stenbakken G.N. 《IEEE transactions on instrumentation and measurement》2006,55(4):1094-1100
Continued efforts to model the distortion behavior of custom-designed digitizing samplers for accurate measurement of dynamic signals are reported. This work is part of ongoing efforts at the National Institute of Standards and Technology (NIST) to advance the state of the art in waveform sampling metrology. In this paper, an analytic error model for a sampler having a -3-dB 6-GHz bandwidth is described. The model is derived from examination of the sampler's error behavior in the phase plane. The model takes as inputs the per-sample estimates of signal amplitude, first derivative, and second derivative, where the derivatives are with respect to time. The model's analytic form consists of polynomials in these terms, which are chosen from consideration of the voltage dependence of the digitizer input capacitance and the previously studied error behavior in a predecessor digitizer. At 1 GHz, an improvement in total harmonic distortion from -32 to -46 dB is obtained when model-generated sample corrections are applied to the waveform. The effect of timebase distortion in the sampling system is also accounted for and corrected. The inclusion of second-derivative dependence in the model is shown to improve the model's fit to the measured data by providing fine temporal adjustment of the fitted waveform. 相似文献
994.
995.
996.
B?ckman Lars; Hassing Linda; Forsell Yvonne; Viitanen Matti 《Canadian Metallurgical Quarterly》1996,11(4):649
Population-based samples of normal old adults and people with major depression (MD), Alzheimer's disease (AD), and coexisting MD and AD (MD + AD) between 90 and 100 years of age were assessed in face recognition, word recall, and object recall. Results indicated a consistent pattern across tasks: no differences between the normal old and the MD participants or between the AD and MD + AD participants in any task, a clear performance decrement in the AD and MD + AD participants in all task variables reflecting long-term episodic memory, and no group differences in those variables reflecting short-term memory. These data suggest that depression in very old age may not exacerbate the episodic memory deficit that accompanies AD. Further, differences between normal old and MD participants in episodic memory tasks appear to be negligible among the oldest old. The general lack of effects of MD may be due to the fact that those symptoms of this disease that are most likely to affect memory functioning (e.g., loss of energy, concentration difficulties) are common in AD as well as in nondepressed people in the 10th decade of life. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
997.
The influence of cooling rate upon the decomposition of wustite in the system Ca-Fe-O has been studied. By SEM and EDS measurements the eutectic-like decomposition product is shown to be a mixture of wustite, Ca2 Fe2 O5 , and Fe formed by a eutectoid decomposition of wustite. The CaO-FeO section in the Ca-Fe-O system is shown not to be eutectic, as previously suggested. The phase diagram suggested by Abbatista is regarded as the correct alternative. 相似文献
998.
A model for multiphase simulations in 1D previously reported in [H. Larsson, A. Engström, Acta Mater. 54 (2006) 2431] has been further developed and incorporated in the DICTRA software. The model is based on the assumption of local equilibrium and locally averaged kinetic properties, which computationally transforms the problem into a single-phase diffusion process. The applicability of the model is discussed and example simulations are presented. 相似文献
999.
J Beltran ZS Rosenberg M Kawelblum L Montes AG Bergman A Strongwater 《Canadian Metallurgical Quarterly》1994,23(4):277-281
Standard anatomy textbooks describe the mandibular canal as having a consistent, standard path. The fact that variations in its path exist in a significant percentage of the population is of extreme importance for the surgeon who is performing procedures in close proximity to the mandibular canal. A rare, radiographically detectable variation of the standard anatomy of the mandibular canal is reported. 相似文献
1000.