全文获取类型
收费全文 | 1944篇 |
免费 | 14篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 24篇 |
化学工业 | 173篇 |
金属工艺 | 48篇 |
机械仪表 | 29篇 |
建筑科学 | 35篇 |
矿业工程 | 9篇 |
能源动力 | 12篇 |
轻工业 | 67篇 |
水利工程 | 9篇 |
石油天然气 | 69篇 |
无线电 | 105篇 |
一般工业技术 | 382篇 |
冶金工业 | 789篇 |
原子能技术 | 36篇 |
自动化技术 | 172篇 |
出版年
2021年 | 19篇 |
2020年 | 17篇 |
2019年 | 25篇 |
2018年 | 33篇 |
2017年 | 22篇 |
2016年 | 31篇 |
2014年 | 25篇 |
2013年 | 56篇 |
2012年 | 38篇 |
2011年 | 44篇 |
2010年 | 44篇 |
2009年 | 32篇 |
2008年 | 41篇 |
2007年 | 38篇 |
2006年 | 61篇 |
2005年 | 35篇 |
2004年 | 28篇 |
2003年 | 31篇 |
2002年 | 26篇 |
2001年 | 21篇 |
2000年 | 16篇 |
1999年 | 40篇 |
1998年 | 175篇 |
1997年 | 114篇 |
1996年 | 85篇 |
1995年 | 53篇 |
1994年 | 52篇 |
1993年 | 61篇 |
1992年 | 26篇 |
1991年 | 20篇 |
1990年 | 23篇 |
1989年 | 26篇 |
1988年 | 19篇 |
1987年 | 37篇 |
1986年 | 26篇 |
1985年 | 28篇 |
1984年 | 19篇 |
1983年 | 21篇 |
1982年 | 23篇 |
1981年 | 15篇 |
1980年 | 23篇 |
1978年 | 21篇 |
1977年 | 46篇 |
1976年 | 78篇 |
1974年 | 16篇 |
1973年 | 16篇 |
1970年 | 19篇 |
1969年 | 20篇 |
1968年 | 19篇 |
1966年 | 16篇 |
排序方式: 共有1959条查询结果,搜索用时 15 毫秒
1.
M. N. Levin A. V. Tatarintsev V. A. Makarenko V. R. Gitlin 《Russian Microelectronics》2006,35(5):329-336
A model is formulated that describes how radiation-induced charge accumulates in the gate oxide of a MOS structure and how it decays through tunneling and thermal emission. The model is used in a numerical analysis of the x-ray or UV adjustment of threshold voltage in MOS-circuit manufacture. The limits of this process technique are evaluated. 相似文献
2.
CA Piantadosi J Zhang ED Levin RJ Folz DE Schmechel 《Canadian Metallurgical Quarterly》1997,147(1):103-114
Delayed neurological damage after CO hypoxia was studied in rats to determine whether programmed cell death (PCD), in addition to necrosis, is involved in neuronal death. In rats exposed to either air or CO (2500 ppm), microdialysis in brain cortex and hippocampus was performed to determine the extent of glutamate release and hydroxyl radical generation during the exposures. Groups of control and CO-exposed rats also were tested in a radial maze to assess the effects of the CO exposures on learning and memory. At 3, 7, and 21 days after CO exposure brains were perfusion-fixed and hematoxylin-eosin (H&E) was used to assess injury and to select regions for further examination. DNA fragmentation was sought by examining cryosections with the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) reaction. We found significant increases in glutamate release and .OH generation during and immediately after CO hypoxia. CO-exposed rats showed learning and memory deficits after exposure associated with heterogeneous cell loss in cortex, globus pallidus, and cerebellum. The frontal cortex was affected most seriously; the damage was slight at Day 3, increased at Day 7, and persistent at Day 21 after CO exposure. TUNEL staining was positive at all three time points, and TUNEL-labeled cells were distributed similarly to eosinophilic cells. The number of cells stained by TUNEL was less than by H&E and amounted to 2 to 5% of all cell nuclei in regions of injury. Ultrastructural features of both neuronal necrosis and apoptosis also were observed readily by electron microscopy. These findings indicate that both necrosis and apoptosis (PCD) contribute to CO poisoning-induced brain cell death. 相似文献
3.
PeterL.Levin ReinholdLudwig 《世界电子元器件》2002,(5):43-45
通过简单地剪切和粘贴知识产权(IP)内核可以加快无工厂半导体公司的系统级芯片(SOC)设计。 过去十年中,涌现出大量的为系统制造商提供专用芯片(ASIC)的小型IC设计公司。这些被称为无工厂企业(因为他们将IC制造过程转交给商业芯片制造工厂),需要的启动资金较少,而且如果市场接受他们的产品的话,能够获得丰厚的回报。在大量设计工具的支持下,这些无工厂设计企业在历史悠久的大型芯片制造商,如IBM、Intel、Motorola和德州仪器公司所主导的市场中赢得了一席之地。 相似文献
4.
B Ben-David E Solomon H Levin H Admoni Z Goldik 《Canadian Metallurgical Quarterly》1997,85(3):560-565
Recent concern regarding lidocaine neurotoxicity has prompted efforts to find alternatives to lidocaine spinal anesthesia. Small-dose dilute bupivacaine spinal anesthesia yields a comparably rapid recovery profile but may provide insufficient anesthesia. By exploiting the synergism between intrathecal opioids and local anesthetics, it may be possible to augment the spinal anesthesia without prolonging recovery. Fifty patients undergoing ambulatory surgical arthroscopy were randomized into two groups receiving spinal anesthesia with 3 ml 0.17% bupivacaine in 2.66% dextrose without (Group I) or with (Group II) the addition of 10 microg fentanyl. Median block levels reached T7 and T8, respectively (P = not significant [NS]). Mean times to two-segment regression, S2 regression, time out of bed, time to urination, and time to discharge were 53 vs 67 min (P < 0.01), 120 vs 146 min (P < 0.05), 146 vs 163 min (P = NS), 169 vs 177 min (P = NS), and 187 vs 195 min (P = NS) respectively. Motor blockade was similar between groups, but sensory blockade was significantly more intense in Group II (P < 0.01). Six of 25 blocks failed in Group I, whereas none failed in Group II. The addition of 10 microg fentanyl to spinal anesthesia with dilute small-dose bupivacaine intensifies and increases the duration of sensory blockade without increasing the intensity of motor blockade or prolonging recovery to micturition or street fitness. IMPLICATIONS: Concerns about the neurotoxicity of lidocaine have prompted efforts to find alternatives to lidocaine spinal anesthesia. We studied 50 patients undergoing ambulatory surgical arthroscopy and found that although small-dose bupivacaine alone is inadequate for this procedure, the addition of fentanyl makes it reliable. 相似文献
5.
B. M. Levin 《Measurement Techniques》1996,39(4):410-418
Results are presented from a study of a method for determining flow rate in discharge pipes by measuring velocity at one point
of the outlet section of a convergent duct that smoothly connects two pipes of different diameters. A metrological analysis,
of the measurement method is presented.
Translated from Izmeritel'naya Teknika, No. 4, pp. 40–45, April, 1996 相似文献
6.
Three roller/blade tachometric chamber transducers, with capacities of 2, 10, and 20 cm3/rev, have been designed for measuring low flow rates.
Translated from Izmeritel'naya Tekhnika, No. 5, pp. 37–41, May, 1996. 相似文献
7.
8.
9.
The results of block model calculations for multiple discretizations of a dielectric sphere and circular cylinder suggest that it is essential that the cells must be arranged for a best-fit of the body being modeled, the matrix elements must be reasonably accurate, and the cells must be small enough so that the pulse-function basis approximation is not blatantly unreasonable. When these criteria are approximately satisfied the remaining errors appear to be mainly due to imperfect representation of the shape of the object being modeled. It appears that the accuracy can be improved by using discretizations having cells of reduced size near the surface of the object. Geometric factors are defined which allow testing the potential accuracy of a solution without dimensioning or inverting a large matrix. Several unique procedures for discretization are also described that have the potential of partially mitigating the errors due to inaccurate representation of the shape of a scatterer. 相似文献
10.
HS Levin 《Canadian Metallurgical Quarterly》1993,6(6):841-846
Progress in research includes studies concerning the pathophysiology and outcome of pediatric head injury, the pathology of the hippocampus in fatal injury, and the use of multivariate statistics to predict outcome in survivors. Recent research has confirmed and extended findings regarding the differential effects of closed head injury, depending on the age of the individual. These studies indicate that the consequences of head injury are more severe in older adults and in children younger than 2 years. Neuroimaging findings include evidence for delayed brain injury as a major cause of mortality and disability. Functional brain imaging provides evidence for cerebral dysfunction that is not appreciated by structural brain imaging techniques and may have a stronger relationship to neurobehavioral sequelae. The neurobehavioral sequelae frequently implicate frontal dysfunction, even in the absence of structural findings on computed tomography or magnetic resonance imaging. Studies of mild head injury have expanded our knowledge concerning the pathogenesis of postconcussional symptoms, including a preinjury vulnerability based on recent life events. Persistent postconcussional symptoms after mild head injury are frequently associated with emotional disturbance of clinical proportions. 相似文献