全文获取类型
收费全文 | 3024篇 |
免费 | 118篇 |
国内免费 | 45篇 |
专业分类
电工技术 | 60篇 |
综合类 | 41篇 |
化学工业 | 330篇 |
金属工艺 | 68篇 |
机械仪表 | 44篇 |
建筑科学 | 70篇 |
矿业工程 | 12篇 |
能源动力 | 93篇 |
轻工业 | 206篇 |
水利工程 | 33篇 |
石油天然气 | 38篇 |
武器工业 | 7篇 |
无线电 | 125篇 |
一般工业技术 | 241篇 |
冶金工业 | 1600篇 |
原子能技术 | 30篇 |
自动化技术 | 189篇 |
出版年
2024年 | 4篇 |
2023年 | 28篇 |
2022年 | 38篇 |
2021年 | 62篇 |
2020年 | 36篇 |
2019年 | 51篇 |
2018年 | 73篇 |
2017年 | 63篇 |
2016年 | 61篇 |
2015年 | 52篇 |
2014年 | 68篇 |
2013年 | 127篇 |
2012年 | 86篇 |
2011年 | 140篇 |
2010年 | 96篇 |
2009年 | 74篇 |
2008年 | 85篇 |
2007年 | 73篇 |
2006年 | 56篇 |
2005年 | 67篇 |
2004年 | 41篇 |
2003年 | 24篇 |
2002年 | 32篇 |
2001年 | 25篇 |
2000年 | 28篇 |
1999年 | 39篇 |
1998年 | 471篇 |
1997年 | 275篇 |
1996年 | 178篇 |
1995年 | 108篇 |
1994年 | 89篇 |
1993年 | 86篇 |
1992年 | 17篇 |
1991年 | 24篇 |
1990年 | 22篇 |
1989年 | 32篇 |
1988年 | 34篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 17篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 18篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 62篇 |
1976年 | 120篇 |
1975年 | 5篇 |
排序方式: 共有3187条查询结果,搜索用时 31 毫秒
41.
Recent reports on the treatment of chylothorax postulate a benefit to ventilator therapy, especially using positive end-expiratory pressure (PEEP). This report describes the use of mechanical ventilation with PEEP in the management of a 24-year-old male motorcyclist who sustained a ligamentous Chance fracture of the thoracic spine at the T6-7 level with bilateral traumatic chylothorax. Treatment of the chylothorax consisted of high PEEP ventilation, bilateral chest tube thoracostomies, and total parenteral nutrition. The chylothoraces resolved within 4 days of treatment and mechanical ventilation was stopped. Ventilator therapy of traumatic chylothorax and the physiologic grounds for its use are discussed. A review of the literature and experimental evidence seem to suggest that ventilator treatment of traumatic chylothoraces is effective. 相似文献
42.
43.
In 3 studies, the authors explored age changes and individual differences in preschool children's sustained attention in several different contexts--watching a videotape, playing with toys, and performing reaction time tasks. Various indexes of attention increased from 30 months to 54 months, whereas inattention decreased. Changes tended to occur earlier for play and television viewing than for the reaction time task. Together, the results also provide evidence for individual differences in measures of attention and inattention through high internal consistency and stability over time within situations. Correlations across situations, however, were low to modest. These results suggest that children have stable tendencies to focus and sustain attention in particular contexts but that their attention varies with the demands of the task and their ability or interest in meeting those demands. 相似文献
44.
45.
46.
Endocrine studies of captive strepsirrhine primates suggest that physical environment and social factors mediate inter-individual variations in testicular function and serum testosterone (sT) in males. While these studies have made major contributions to our understanding of the individual proximate mechanisms influencing androgen activity in male strepsirrhines, none have investigated how these mechanisms work coincidentally in free-ranging populations. In this study we used fecal steroid analysis to examine androgen-behavior interactions associated with reproduction in free-ranging male Propithecus verreauxi. Behavioral and hormone data were collected from two social groups during the 1990-91 and 1991-92 breeding seasons at Beza Mahafaly, Madagascar. Solid phase and radioimmunoassay techniques were used to quantify testosterone (T) in 105 desiccated fecal samples collected weekly from seven males. Results suggest that 1) solid phase extraction and radioimmunoassay techniques were reliable and accurate methods for quantifying T in sifaka feces; 2) fecal T (fT) elevations spanned a minimum of 4 months, peak levels occurring 1 month prior to the January onset of the breeding season; 3) fecal T concentrations were influenced by developmental factors and, among mature males, social factors associated with rank, intergroup aggression, and group instability. 相似文献
47.
HA Langendijk RJ Lamers GP ten Velde DG Sanders JM de Jong F Kessels EF Wouters 《Canadian Metallurgical Quarterly》1998,41(5):1037-1045
BACKGROUND: The purpose of this study was to evaluate whether the chest radiograph is a reliable tool to assess response to radiotherapy. MATERIALS AND METHODS: Pre- and post-treatment chest radiographs and computed tomographs (CT) of 63 patients with nonsmall cell lung cancer (NSCLC) treated by radiotherapy were reviewed by four observers with regard to suitability for tumor measurement, and response. Suitability for tumor measurement was expressed as the number of measurable diameters. In addition, the consequences to clinical outcome were studied by survival analysis. RESULTS: The CT turned out to be more suited for tumor measurement before as well as after radiotherapy, resulting in an increase of the number of measurable cases. The number of measurable cases with CT was 52 (83%) as compared to 28 (44%) with chest radiography. Especially in case of centrally localized tumors, the presence of an atelectasis, or squamous cell carcinoma, CT contributed to a higher rate of measurable cases. The interobserver agreement with regard to response using chest radiograph was good (mean kappa = 0.74). In 25 of 28 cases (89%) measurable with CT as well as with chest radiograph, response was equally classified. When CT was used, the median survival of the responders was 14.2 months as compared to 6.8 months of the nonresponders. When chest radiograph was used, the median survival of these groups was 12.0 and 6.6 months respectively, which was not significantly different when response was assessed by CT. CONCLUSION: We conclude that CT is more suited for tumor measurement because more measurable lesions can be found and more evaluable lesions on chest radiograph become measurable on CT. The chest radiograph does have a valuable role to play in those lesions that are measurable because of the good interobserver agreement with regard to the response classification, the high overall agreement between CT and chest radiograph in case of measurable cases, and the lack of important differences with regard to survival. 相似文献
48.
Thirty-three HIV-positive women, 12 of whom were pregnant, participated in semistructured interviews to define areas of psychosocial need. Eighty-eight percent of the subjects reported current unemployment. A history of substance abuse was reported by 82 percent, suicide attempts by 52 percent, and sexual problems by 43 percent. Approximately 30 percent reported elevated levels of depressive symptoms on standardized symptom inventories. The pregnant women appeared psychologically healthier than the nonpregnant group. HIV-positive women face multiple psychosocial stressors and may experience significant psychological distress. 相似文献
49.
Aziz Romila Anwar Muhammad Waqas Jamal Muhammad Hasan Bajwa Usama Ijaz 《Neural computing & applications》2021,33(21):14707-14721
Neural Computing and Applications - Detecting and correcting misspelled words in a written text are of great importance in many natural language processing applications. Errors can be broadly... 相似文献
50.
This article focuses on the emerging online Arab public sphere that the web has enabled. It explores how the “local” interacts with the “global,” critically examining their implications on global politics. Specifically looking at online readers' comments about the Swiss minaret ban the so‐called “Ground Zero Mosque,” how does the Arab online public sphere respond to and frame these issues? What implications do these reader frames portend locally and globally? The study analyzes online comments and responses that readers of Al Arabiya.net and Al Jazeera.net posted on related news articles. The article concludes that the new online public sphere does make it possible for Arab citizens to circumvent and challenge traditional authoritarian controls. 相似文献