全文获取类型
收费全文 | 5684篇 |
免费 | 116篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 73篇 |
化学工业 | 443篇 |
金属工艺 | 32篇 |
机械仪表 | 47篇 |
建筑科学 | 109篇 |
矿业工程 | 6篇 |
能源动力 | 82篇 |
轻工业 | 292篇 |
水利工程 | 23篇 |
石油天然气 | 15篇 |
无线电 | 405篇 |
一般工业技术 | 439篇 |
冶金工业 | 3440篇 |
原子能技术 | 55篇 |
自动化技术 | 349篇 |
出版年
2022年 | 23篇 |
2021年 | 47篇 |
2020年 | 22篇 |
2019年 | 52篇 |
2018年 | 50篇 |
2017年 | 53篇 |
2016年 | 70篇 |
2015年 | 35篇 |
2014年 | 61篇 |
2013年 | 164篇 |
2012年 | 85篇 |
2011年 | 113篇 |
2010年 | 101篇 |
2009年 | 92篇 |
2008年 | 131篇 |
2007年 | 111篇 |
2006年 | 85篇 |
2005年 | 77篇 |
2004年 | 63篇 |
2003年 | 72篇 |
2002年 | 63篇 |
2001年 | 83篇 |
2000年 | 60篇 |
1999年 | 154篇 |
1998年 | 929篇 |
1997年 | 561篇 |
1996年 | 408篇 |
1995年 | 198篇 |
1994年 | 194篇 |
1993年 | 257篇 |
1992年 | 59篇 |
1991年 | 61篇 |
1990年 | 82篇 |
1989年 | 80篇 |
1988年 | 78篇 |
1987年 | 71篇 |
1986年 | 71篇 |
1985年 | 84篇 |
1984年 | 33篇 |
1983年 | 35篇 |
1982年 | 41篇 |
1981年 | 57篇 |
1980年 | 58篇 |
1979年 | 25篇 |
1978年 | 41篇 |
1977年 | 109篇 |
1976年 | 217篇 |
1975年 | 39篇 |
1974年 | 15篇 |
1973年 | 16篇 |
排序方式: 共有5810条查询结果,搜索用时 15 毫秒
81.
82.
83.
With the recent advent of accurate orbital volume assessment by computed tomography, a retrospective analysis was made of 31 patients with 'pure' blowout fracture of the orbital floor, managed either surgically or conservatively, to determine whether orbital volume measurement could provide an additional parameter of use in the management of such fractures. There was a significant difference in orbital volume discrepancy between patients managed surgically or conservatively suggesting that this investigation may be of use in decision making on surgical intervention in patients with orbital blowout fractures. 相似文献
84.
Grant Igor; Olshen Richard A.; Atkinson J. Hampton; Heaton Robert K.; Nelson Julie; McCutchan J. Allen; Weinrich James D. 《Canadian Metallurgical Quarterly》1993,7(1):53
The relationship of depressed mood to cognitive disturbance in HIV infection was examined in a sample of 139 homosexual men. Ss were grouped according to the classification of the Centers for Disease Control: 39 were in Group IV, 62 were in Group II or Group III, and 38 were HIV-negative. Ss completed the Profile of Mood States and 10 neuropsychological tests. Analysis employing a classification approach indicated that, although symptoms of depression and neuropsychological impairment were more common in Ss who were HIV-positive, particularly those classified as Group IV, there were no systematic relationships between depression and neuropsychological impairment. Depressed mood and cognitive disturbance each seem to have unique associations to HIV illness status. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
85.
Tobacco use remains the number one cause of preventable morbidity and premature death in the United States. As a result, military leaders are recognizing that tobacco can adversely affect military fitness levels, deployment readiness, and safety and can increase health care costs. Yet military members continue to use tobacco. Tobacco may be viewed as part of the military culture since military members have used tobacco for many decades for pleasure, comfort, and currency and as a morale booster. Most recently, the military has seen an increase in tobacco use among young military members. A number of research studies have examined the prevalence of tobacco and factors related to use in the military, and several have evaluated cessation and prevention interventions. This article provides a brief historical perspective of military tobacco use in the 20th century and a critical review of the literature published between 1991 and 2006 describing prevalence of tobacco use, factors influencing use, and cessation interventions in the military. Recommendations for future research and for interventions are provided. 相似文献
86.
The modality effect in immediate recall refers to superior recall of the last few items within lists presented in spoken as opposed to printed form. The locus of this well-known effect has been unclear. N. Cowan, J. S. Saults, E. M. Elliott, and M. Moreno (2002) introduced a new method to distinguish between the effects of input serial position, output serial position, and the number of items yet to be recalled and found that large modality effects occurred only in conditions in which delay and interference at output (from items already recalled) was high. The authors replicated that finding, even when the response period included output interference acoustically similar to the spoken stimuli to be recalled. However, the authors found that output delay and interference act only by lowering the level of performance to a more sensitive range. The modality effect thus originates during encoding of the list to be recalled, not during output. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
Thin layers of silver and titanium were deposited onto commercial Ti–48Al particles by magnetron sputtering prior to their consolidation by hot isostatic pressing and subsequent heat treatment.
Based on picnometry and electron probe microanalysis results, average values of 1.5 and 2.5 at.%, respectively, were obtained
for the silver and titanium contents in the coated particles. The surface modified Ti–48Al particles exhibited improved sintering ability than the unmodified ones. The consolidated samples have duplex microstructures
formed by γ-TiAl and γ-TiAl + α2-Ti3Al grains. Ag-rich nanoprecipitates were detected in the microstructure of the compacted Ti-48Al + Ag sample. The coatings are no longer visible at the grains boundaries after a subsequent homogenization heat treatment
at 1200°C. The highest values of hardness and Young’s modulus were obtained for the Ti–48Al + Ag sample, associated with a higher density and a lower percentage of pores. 相似文献
88.
WA Cafruny SE Bradley A Brunick DM Nelson RF Nelson 《Canadian Metallurgical Quarterly》1996,59(1-2):83-89
An animal model of dental virus transmission was developed using the lactate dehydrogenase-elevating virus (LDV) of mice to study cross infection. Mouse-to-mouse cross-infection was carried out by scaling the teeth of LDV-infected donor mice with dental instruments, immediately prior to using the contaminated instruments on the teeth of recipient indicator mice. The level of donor viremia was found to correlate with the rate of virus cross-infection, with a viremia threshold level of 10(7.5) ID50/ml observed for dental cross-infection. The blood volume transferred during dental cross-infection was approximately 10(-4) to 10(-5) ml, demonstrating the inefficiency of virus cross-infection, since deposition of about 1000 virions on dental instruments was associated with the threshold limit. Virus transferred during dental cross-infection rapidly entered the blood circulation, showing that dental cross-infection was not dependent on an oral infection. The results from these model studies predict the general inefficiency of dental instrument virus cross-infection, and a further reduced likelihood of dental cross-infection with appropriately cleaned instruments. 相似文献
89.
90.