全文获取类型
收费全文 | 696篇 |
免费 | 25篇 |
国内免费 | 24篇 |
专业分类
化学 | 17篇 |
晶体学 | 1篇 |
力学 | 25篇 |
综合类 | 1篇 |
数学 | 13篇 |
物理学 | 42篇 |
综合类 | 646篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 4篇 |
2021年 | 18篇 |
2020年 | 15篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2017年 | 12篇 |
2016年 | 11篇 |
2015年 | 25篇 |
2014年 | 40篇 |
2013年 | 25篇 |
2012年 | 51篇 |
2011年 | 60篇 |
2010年 | 27篇 |
2009年 | 49篇 |
2008年 | 44篇 |
2007年 | 38篇 |
2006年 | 37篇 |
2005年 | 32篇 |
2004年 | 36篇 |
2003年 | 43篇 |
2002年 | 17篇 |
2001年 | 19篇 |
2000年 | 12篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 5篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 10篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1971年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有745条查询结果,搜索用时 12 毫秒
21.
高许 《科技情报开发与经济》2009,19(17):225-227
从矿井中瓦斯存在的形式、瓦斯涌出条件及瓦斯涌出措施等方面入手,通过案例分析说明了砌筑通风设施位王的合理性在防治瓦斯方面的重要性. 相似文献
22.
针对高校化学实验室的特点,提出化学实验室通风系统、自动控制系统、BENTAX净化系统设计方案。通过对设计方案的研究,为类似工程实践提供可参考的思路和方法。 相似文献
23.
为获得攒尖四坡屋面的风致雪漂移规律,基于欧拉-欧拉方法和风雪单向耦合假定,运用计算流体动力学软件,选取Mixture模型分别对立方体周边和高低屋面上的风致雪漂移运动进行数值模拟,将模拟结果与两者的实地观测数据对比,探讨分析数值风洞的关键技术和参数设置,验证数值模拟方法的合理性与可靠性。依据攒尖四坡房屋的使用功能要求,设计分析模型与分析工况,在试算的基础上对屋面进行分区。以风速5 m/s,7 m/s,9 m/s,11 m/s,13 m/s和15 m/s,风向角0°,15°,30°和45°以及屋面坡度25°,30°,34°,40°和45°为分析参数,对攒尖四坡房屋的120种工况进行数值模拟,得到屋面各分区侵蚀沉积的基本规律,提出可用于抗雪设计的屋面积雪分布系数。研究表明,风向角的改变会使屋面积雪分布状态发生较大程度的变化,风速和屋面坡度的变化对屋面整体积雪量有较大影响。 相似文献
24.
Miklos Kassai 《实验传热》2018,31(2):106-120
The object of this research was to investigate the effectiveness of sorption energy exchanger and the impact of the operational and thermal environmental conditions on their efficiency under steady-state conditions. To achieve this object, a test facility was installed into the Indoor Air Quality and Thermal Comfort Laboratory of BUTE University. A molecular 3Å sieve sorption wheel with high latent effectiveness is integrated into the experimental setup. In this study, the correlation between the sensible, latent, total effectiveness under different ambient air temperature and humidity values and different rotational speeds of the wheel is investigated in detailed by experimental tests. 相似文献
25.
按目标分层,用分层模糊优选理论对矿井通风系统设计方案进行优选,分层时允许评价因素重叠,从而便于确定目标与评价因素的权重。本研究成果已应用于中条山有色金属公司胡家峪铜矿通风系统优化研究中,同时本文的方法也可以应用于其它领域中的类似问题。 相似文献
26.
介绍了公路隧道竖井通风方式的分类和特点,探讨了竖井纵向式通风形式的机理,指出对于双向交通隧道宜采用合流型集中排风式;对于单向交通隧道应采用分流型集中排风式或送排式,对于特长隧道,可以采用数个竖井的送排式通风。 相似文献
27.
通风机性能现场测试的可能性、规范性和准确性很大程度上取决于通风机房与峒室系统设计的的合理性。本文结合通风机性能现场测试规范性提出了设计与改进通风机房与峒室系统的建议。图5,参3。 相似文献
28.
Lukas Martin Müller-Wirtz Daniel Kiefer Sven Ruffing Timo Brausch Tobias Hüppe Daniel I. Sessler Thomas Volk Tobias Fink Sascha Kreuer Felix Maurer 《Molecules (Basel, Switzerland)》2021,26(11)
Exhaled aliphatic aldehydes were proposed as non-invasive biomarkers to detect increased lipid peroxidation in various diseases. As a prelude to clinical application of the multicapillary column–ion mobility spectrometry for the evaluation of aldehyde exhalation, we, therefore: (1) identified the most abundant volatile aliphatic aldehydes originating from in vitro oxidation of various polyunsaturated fatty acids; (2) evaluated emittance of aldehydes from plastic parts of the breathing circuit; (3) conducted a pilot study for in vivo quantification of exhaled aldehydes in mechanically ventilated patients. Pentanal, hexanal, heptanal, and nonanal were quantifiable in the headspace of oxidizing polyunsaturated fatty acids, with pentanal and hexanal predominating. Plastic parts of the breathing circuit emitted hexanal, octanal, nonanal, and decanal, whereby nonanal and decanal were ubiquitous and pentanal or heptanal not being detected. Only pentanal was quantifiable in breath of mechanically ventilated surgical patients with a mean exhaled concentration of 13 ± 5 ppb. An explorative analysis suggested that pentanal exhalation is associated with mechanical power—a measure for the invasiveness of mechanical ventilation. In conclusion, exhaled pentanal is a promising non-invasive biomarker for lipid peroxidation inducing pathologies, and should be evaluated in future clinical studies, particularly for detection of lung injury. 相似文献
29.
Lukas M. Müller-Wirtz Daniel Kiefer Joschua Knauf Maximilian A. Floss Jonas Doneit Beate Wolf Felix Maurer Daniel I. Sessler Thomas Volk Sascha Kreuer Tobias Fink 《Molecules (Basel, Switzerland)》2021,26(9)
High inspired oxygen during mechanical ventilation may influence the exhalation of the previously proposed breath biomarkers pentanal and hexanal, and additionally induce systemic inflammation. We therefore investigated the effect of various concentrations of inspired oxygen on pentanal and hexanal exhalation and serum interleukin concentrations in 30 Sprague Dawley rats mechanically ventilated with 30, 60, or 93% inspired oxygen for 12 h. Pentanal exhalation did not differ as a function of inspired oxygen but increased by an average of 0.4 (95%CI: 0.3; 0.5) ppb per hour, with concentrations doubling from 3.8 (IQR: 2.8; 5.1) ppb at baseline to 7.3 (IQR: 5.0; 10.8) ppb after 12 h. Hexanal exhalation was slightly higher at 93% of inspired oxygen with an average difference of 0.09 (95%CI: 0.002; 0.172) ppb compared to 30%. Serum IL-6 did not differ by inspired oxygen, whereas IL-10 at 60% and 93% of inspired oxygen was greater than with 30%. Both interleukins increased over 12 h of mechanical ventilation at all oxygen concentrations. Mechanical ventilation at high inspired oxygen promotes pulmonary lipid peroxidation and systemic inflammation. However, the response of pentanal and hexanal exhalation varies, with pentanal increasing by mechanical ventilation, whereas hexanal increases by high inspired oxygen concentrations. 相似文献