全文获取类型
收费全文 | 43150篇 |
免费 | 924篇 |
国内免费 | 182篇 |
专业分类
电工技术 | 530篇 |
综合类 | 632篇 |
化学工业 | 4618篇 |
金属工艺 | 595篇 |
机械仪表 | 872篇 |
建筑科学 | 855篇 |
矿业工程 | 390篇 |
能源动力 | 415篇 |
轻工业 | 2061篇 |
水利工程 | 610篇 |
石油天然气 | 50篇 |
武器工业 | 4篇 |
无线电 | 1871篇 |
一般工业技术 | 3503篇 |
冶金工业 | 21407篇 |
原子能技术 | 189篇 |
自动化技术 | 5654篇 |
出版年
2024年 | 55篇 |
2023年 | 189篇 |
2022年 | 114篇 |
2021年 | 114篇 |
2018年 | 455篇 |
2017年 | 676篇 |
2016年 | 1050篇 |
2015年 | 776篇 |
2014年 | 422篇 |
2013年 | 425篇 |
2012年 | 2144篇 |
2011年 | 2448篇 |
2010年 | 676篇 |
2009年 | 774篇 |
2008年 | 629篇 |
2007年 | 647篇 |
2006年 | 573篇 |
2005年 | 3359篇 |
2004年 | 2569篇 |
2003年 | 2053篇 |
2002年 | 860篇 |
2001年 | 740篇 |
2000年 | 290篇 |
1999年 | 629篇 |
1998年 | 6152篇 |
1997年 | 3804篇 |
1996年 | 2508篇 |
1995年 | 1453篇 |
1994年 | 1073篇 |
1993年 | 1099篇 |
1992年 | 252篇 |
1991年 | 307篇 |
1990年 | 307篇 |
1989年 | 280篇 |
1988年 | 298篇 |
1987年 | 229篇 |
1986年 | 206篇 |
1985年 | 174篇 |
1984年 | 77篇 |
1983年 | 88篇 |
1982年 | 138篇 |
1981年 | 187篇 |
1980年 | 194篇 |
1979年 | 63篇 |
1978年 | 103篇 |
1977年 | 617篇 |
1976年 | 1325篇 |
1975年 | 105篇 |
1973年 | 53篇 |
1971年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
The effects of adenosine and sodium nitroprusside (SNP) on central hemodynamics and myocardial blood flow and metabolism were investigated postoperatively after elective coronary artery bypass (CABG) surgery in ten sedated and mechanically ventilated patients in the intensive care unit. During three consecutive 15-min periods, SNP (0.8 +/- 0.1 micrograms.kg-1 x min-1), adenosine (88.9 +/- 13.3 micrograms.kg-1 x min-1), and then again SNP (0.7 +/- 0.1 micrograms.kg-1 x min-1) were infused to control postoperative hypertension at a mean arterial pressure of approximately 80 mm Hg. Systemic and pulmonary hemodynamics and global (coronary sinus flow, CSF) as well as regional (great cardiac vein flow, GCVF) myocardial blood flow and metabolic variables were measured. During adenosine infusion, in comparison to SNP, heart rate was unchanged, stroke volume index and cardiac index increased (24% and 32%, respectively), and the systemic vascular resistance index decreased (-26%). Mean pulmonary arterial pressure (24%) as well as pulmonary capillary wedge pressure (27%) and central venous pressure (18%) were higher with adenosine compared to SNP. Adenosine also increased CSF and GCVF (108% and 103%, respectively) without altering the CSF/GCVF flow ratio compared to SNP. Furthermore, adenosine increased the coronary oxygen content (51%) and decreased the arterio-great cardiac vein oxygen content difference (-48%) without changing regional myocardial oxygen consumption, indicating a more pronounced hyperkinetic myocardial circulation compared to SNP. In addition, adenosine infusion decreased arterial PO2 (-11%) and increased the intrapulmonary shunt fraction (57%). The PR interval time of the electrocardiogram was prolonged (12%) and the ST segment was more depressed during adenosine infusion compared to SNP.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
52.
A G?rling 《Canadian Metallurgical Quarterly》1993,47(4):2783-2799
53.
54.
Head and eye movements were simultaneously recorded during locomotory and pecking behavior of 4 pigeons, which were trained to traverse a conditioning chamber, with a pecking key and a food dispenser at each end. Each trial involved key pecking, walking, and feeding. Head movements were registered with a skull-mounted miniature accelerometer, and eye movements were recorded with implanted electrooculogram (EOG) electrodes. An almost perfect temporal coordination between head and eye movements was observed during both walking and feeding bouts. During walking, head movements primarily provide retinal image stability, and eye movements support visual scanning. During feeding, head movements mainly subserve the grasping of food items, and eye movements maintain visual fixation on them. Because the eyes are reflexively closed during the middle phase of pecks, the head and eye movements are then under ballistic control. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
F Jónsson P Madsen LG J?rgensen M Lunding NH Secher 《Canadian Metallurgical Quarterly》1996,158(44):6256-6259
Indices of fluid balance were evaluated during and after aortic surgery in 16 consecutive patients. Thoracic electrical impedance (TI), heart rate (HR), central venous (CVP), pulmonary artery mean (PAMP), pulmonary wedge (PWP) and mean arterial (MAP) pressures as well as fourteen arterial and venous blood gas variables were followed. Consistent with a reduction of TI during the operation, fluid balance was in excess, and it remained elevated on the first postoperative morning. The HR, MAP and PWP remained stable, while CVP and PAMP decreased. Of the determined variables only TI revealed a meaningful correlation to fluid balance (rho = -0.41; p < 0.01). The results indicate that while central venous and pulmonary artery mean pressures gave the impression of a volume deficit, the positive fluid balance was mirrored by thoracic electrical impedance. 相似文献
56.
57.
58.
A modified natural surfactant was administered to a patient with life-threatening adult respiratory distress syndrome caused by viral pneumonia. Subsequently, there was a marked improvement in gas exchange. In order to assess the mechanism for improved oxygenation, computed tomography of the lungs was done. Quantitative analysis of the scans taken before and after surfactant administration indicates that improvement in gas exchange was largely due to the expansion of underinflated and collapsed lung areas. Although this is a single case report, it provides insight into the possible beneficial effect of instilled surfactant in severe respiratory distress from viral pneumonia. 相似文献
59.
J Botling F Oberg H T?rm? P Tuohimaa M Bl?uer K Nilsson 《Canadian Metallurgical Quarterly》1996,7(9):1239-1249
60.