全文获取类型
收费全文 | 3030篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 59篇 |
金属工艺 | 5篇 |
机械仪表 | 8篇 |
建筑科学 | 27篇 |
矿业工程 | 1篇 |
能源动力 | 41篇 |
轻工业 | 62篇 |
水利工程 | 5篇 |
石油天然气 | 5篇 |
无线电 | 116篇 |
一般工业技术 | 73篇 |
冶金工业 | 2576篇 |
原子能技术 | 19篇 |
自动化技术 | 37篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 11篇 |
2017年 | 3篇 |
2016年 | 9篇 |
2015年 | 6篇 |
2014年 | 17篇 |
2013年 | 16篇 |
2012年 | 18篇 |
2011年 | 35篇 |
2010年 | 21篇 |
2009年 | 18篇 |
2008年 | 24篇 |
2007年 | 27篇 |
2006年 | 17篇 |
2005年 | 26篇 |
2004年 | 12篇 |
2003年 | 14篇 |
2002年 | 14篇 |
2001年 | 14篇 |
2000年 | 8篇 |
1999年 | 82篇 |
1998年 | 687篇 |
1997年 | 413篇 |
1996年 | 316篇 |
1995年 | 147篇 |
1994年 | 129篇 |
1993年 | 182篇 |
1992年 | 32篇 |
1991年 | 53篇 |
1990年 | 42篇 |
1989年 | 48篇 |
1988年 | 38篇 |
1987年 | 35篇 |
1986年 | 43篇 |
1985年 | 51篇 |
1984年 | 12篇 |
1983年 | 20篇 |
1982年 | 24篇 |
1981年 | 29篇 |
1980年 | 29篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1977年 | 78篇 |
1976年 | 164篇 |
1975年 | 7篇 |
1973年 | 3篇 |
排序方式: 共有3042条查询结果,搜索用时 125 毫秒
51.
52.
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
53.
54.
Giving patients instructions to focus on sensory (vs emotional) stimuli during a root canal procedure significantly reduced self-reported pain, but only among patients who were classified as having strong desire for control and low felt control in dental situations. Among patients with low felt control and low desire for control, sensory-focus instructions produced greater pain reports than did emotion-focus instructions. Finally, high desire–low felt patients reported higher levels of expected pain before treatment than did other patient subgroups. These data suggested limiting conditions for H. Leventhal's (1982) theory of emotion and supported the idea that desire for control might moderate the effects of perceived control. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
56.
RW Hanf RG Schreckhise GW Patton TM Poston RE Jaquish 《Canadian Metallurgical Quarterly》1997,73(4):700-705
In 1989, Pacific Northwest National Laboratory developed a program, for the U.S. Department of Energy, to involve local citizens in environmental surveillance at the Hanford Site. The Community-Operated Environmental Surveillance Program was patterned after similar community-involvement efforts at the Nevada Test Site and the Three Mile Island nuclear facility. Its purpose is to increase the flow of information to the public, thereby enhancing the public's awareness and understanding of surveillance activities. The program consists of two components: radiological air monitoring at nine offsite locations and agricultural product sampling at selected locations near the site. At each air-monitoring station, two local school teachers collect air particulate samples and operate equipment to monitor ambient radiation levels. Atmospheric tritium samples (as water vapor) are also collected at some locations. Four of the air-monitoring stations include large, colorful informational displays for public viewing. These displays provide details on station equipment, sample types, and sampling purposes. Instruments in the displays also monitor, record, and show real-time ambient radiation readings (measured with a pressurized ionization chamber) and meteorological conditions. Agricultural products, grown primarily by middle-school-aged students, are obtained from areas downwind of the site. Following analysis of these samples, environmental surveillance staff visit the schools to discuss the results with the students and their teachers. The data collected by these air and agricultural sampling efforts are summarized with other routinely collected sitewide surveillance data and reported annually in the Hanford Site environmental report. 相似文献
57.
OBJECTIVE: To evaluate the relationship between morphologic findings seen on high-resolution computed tomography (HRCT) of the lung and regional lung perfusion depicted on single photon-emission computed tomography (SPECT) pulmonary perfusion imaging in patients with cystic fibrosis. MATERIALS AND METHODS: Ten HRCT and 10 technetium-99 m macroaggregated albumin SPECT pulmonary perfusion imaging studies were performed on eight young adult patients who were considered to be clinically well and have mild to moderate cystic fibrosis. HRCT scans of the chest were evaluated using a CT scoring system which included grading of bronchiectasis, peribronchial thickening, hyperlucency, bullae, collapse/consolidation, and mucus plugging. Each lung was divided into six anatomic zones which were independently scored. A lung perfusion score (between 0 and 100), reflecting the percentage of compromised lung, was estimated for each zone. Axial lung perfusion SPECT images were matched anatomically to HRCT images. Lung function was considered compromised when the counts per pixel were less than 25 % of the count level seen in an area of the same patient's lung which was judged to be normal. RESULTS: There was a statistically significant relationship (P = 0.0001) between HRCT total scores and SPECT lung perfusion scores as well as between hyperlucency scores by HRCT and the SPECT lung perfusion scores. However, the HRCT score was a poor predictor of the lung perfusion score in zones with intermediate HRCT scores, which constituted 106 of 120 zones. CONCLUSION: Morphologic changes depicted by HRCT correlate with decreased lung pefusion on SPECT. However, HRCT changes accurately predict regional lung function only in the most normal and severely diseased lung zones. 相似文献
58.
59.
JM Larsen RL Rimoldi DA Capen RW Nelson S Nagelberg JC Thomas 《Canadian Metallurgical Quarterly》1996,9(2):117-120
Tribal warfare is a way of life in the highlands of Papua New Guinea. In earlier times direct confrontation with bushknives and axes, and shooting with bows and arrows were common. In recent years there have not been as many instances of direct confrontation with bushknives and axes, but the use of bows and arrows is on the rise. Since 1993, guns have been increasingly used, with devastating results. In 1993, 18 deaths were reported from tribal warfare in one area of the Southern Highlands Province, especially from gunshots, while in 1994, 24 deaths were reported from another area. A five-year review of tribal fight admissions to Mendi Hospital, from 1990 to 1994, showed an increase in the number and proportion of gunshot wounds; there were none in 1990-1992 but they constituted 18% of tribal fight injuries in 1993 and 33% in 1994. 相似文献
60.
JF McCarthy DJ Cook MG Massad Y Sano KJ O''Malley NR Ratliff RW Stewart NG Smedira RC Starling JB Young PM McCarthy 《Canadian Metallurgical Quarterly》1998,14(2):197-200
28 isolates of canine parvovirus type-2 (CPV-2) were obtained from dogs with hemorrhagic gastroenteritis in Italy. The antigenic structure of CPV-2 isolates was characterized, using four discriminating monoclonal antibodies. In addition, four vaccinal strains were examined. Similar to reports from Australia and the United Kingdom, a much higher prevalence of CPV-2a (25/28 isolates) was observed than the other variant type, CPV-2b (3/28 isolates). DNA fragments (2.2 kbp) of representative strains of CPV-2, CPV-2a and CPV-2b were amplified by the polymerase chain reaction (PCR) and the products were digested by the restriction enzymes (RE) RsaI, HpaII, HindIII and PvuII. The RvaI enzyme allows the differentiation of CPV-2 from CPV-2a and CPV-2b. 相似文献