全文获取类型
收费全文 | 208篇 |
免费 | 38篇 |
国内免费 | 11篇 |
学科分类
数理化 | 257篇 |
出版年
2023年 | 4篇 |
2022年 | 13篇 |
2021年 | 20篇 |
2020年 | 12篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 6篇 |
2016年 | 11篇 |
2015年 | 21篇 |
2014年 | 13篇 |
2013年 | 23篇 |
2012年 | 21篇 |
2011年 | 15篇 |
2010年 | 9篇 |
2009年 | 10篇 |
2008年 | 8篇 |
2007年 | 12篇 |
2006年 | 8篇 |
2005年 | 5篇 |
2004年 | 1篇 |
2003年 | 7篇 |
2002年 | 5篇 |
2001年 | 2篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有257条查询结果,搜索用时 15 毫秒
1.
Two localized CO2 laser treatment methods for mitigation of UV damage growth in fused silica 下载免费PDF全文
Two methods:high-power,short-time,single-shot irradiation(Method A) and low-power,long-time,multi-shot irradiation(Method B) are investigated to mitigate the UV damage growth in fused silica by using a 10.6-μm CO2 laser.To verify the mitigation effect of the two methods,the laser induced damage thresholds(LIDTs) of the mitigated sites are tested with a 355-nm,6.4-ns Nd:YAG laser,and the light modulation of the mitigation sites are tested with a 351-nm continuous Nd:YLF laser.The mitigated damaged sites treated with the two methods have almost the same LIDTs,which can recover to the level of pristine material.Compared with Method A,Method B produces mitigated sites with low crater depth and weak light modulation.In addition,there is no raised rim or re-deposited debris formed around the crater edge for Method B.Theoretical calculation is utilized to evaluate the central temperature of the CO2 laser beam irradiated zone and the radius of the crater.It is indicated that the calculated results are consistent with the experimental results. 相似文献
2.
Fouling Mitigation in a Heat Exchanger: High Cycles of Concentration for a Cooling-Tower Application
The purpose of the present study is to investigate the effect of a physical water treatment (PWT) technology on fouling mitigation in a simulated cooling tower operating at high cycles of concentration. Hard water was produced by evaporating pure water in a circulating open cooling tower, where dissolved calcium carbonate ions became concentrated with time. Heat transfer tests were conducted in a rectangular channel by varying the cycle of concentration (COC) from 5 to 10, and fouling resistances were measured over 270 hrs for each case with and without the PWT treatment. Another test was conducted with no blowdown case with and without the PWT treatment. The fouling resistance at 5 cycles with the PWT treatment was about 70% less than that in the case without the PWT treatment at the end of 270-hr tests. Even at 10 cycles, the PWT treatment reduced the fouling resistance by 60% from the value for the no treatment case. Thus, one can conclude that the PWT technology can help circulating cooling-tower water at relatively high COC for significant freshwater conservation, while keeping fouling resistances below industry standards. 相似文献
3.
Ryugo S. HAYANO Masaharu TSUBOKURA Makoto MIYAZAKI Hideo SATOU Katsumi SATO Shin MASAKI Yu SAKUMA 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2013,89(4):157-163
The Fukushima Dai-ichi NPP accident contaminated the soil of densely-populated regions in Fukushima Prefecture with radioactive cesium, which poses significant risks of internal and external exposure to the residents. If we apply the knowledge of post-Chernobyl accident studies, internal exposures in excess of a few mSv/y would be expected to be frequent in Fukushima.Extensive whole-body-counter surveys (n = 32,811) carried out at the Hirata Central Hospital between October, 2011 and November, 2012, however show that the internal exposure levels of residents are much lower than estimated. In particular, the first sampling-bias-free assessment of the internal exposure of children in the town of Miharu, Fukushima, shows that the 137Cs body burdens of all children (n = 1,383, ages 6–15, covering 95% of children enrolled in town-operated schools) were below the detection limit of 300 Bq/body in the fall of 2012. These results are not conclusive for the prefecture as a whole, but are consistent with results obtained from other municipalities in the prefecture, and with prefectural data. 相似文献
4.
Ryugo S. HAYANO Ryutaro ADACHI 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2013,89(5):196-199
The first objective data showing the geographical locations of people in Fukushima after the Fukushima Dai-ichi nuclear power plant accident, obtained by an analysis of GPS (Global Positioning System)-enabled mobile phone logs, are presented. The method of estimation is explained, and the flow of people into and out of the 20 km evacuation zone during the accident is visualized. 相似文献
5.
Hiromi NAKANISHI Atsushi MORI Kouki TAKEDA Houdo TANAKA Natsuko KOBAYASHI Keitaro TANOI Takashi YAMAKAWA Satoshi MORI 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2015,91(4):160-174
Six months after the explosion of TEPCO’s Fukushima Dai-ichi nuclear power plant, radioactive
silver (110mAg), was detected in concentrations of 3754 Bq/kg in Nephila
clavata (the orb-web spider; Joro-gumo in Japanese) collected at
Nimaibashi, Iitate village in Fukushima Prefecture, whereas 110mAg in the soil was
43.1 Bq/kg. A survey of 35 faunal species in the terrestrial environment during the 3.5 years
after the accident showed that most of Anthropoda had two orders higher 110mAg in
their tissues than soils, although silver is not an essential element for their life. However,
tracing of the activity of 110mAg detected in spider Atypus karschi
collected regularly at a fixed location showed that it declined much faster than the physical
half-life. These results suggest that 110mAg was at once biologically concentrated
by faunal species, especially Arthropoda, through food chain. The factors affecting the
subsequent rapid decline of 110mAg concentration in faunal species are
discussed. 相似文献
6.
催化材料对病毒的吸附和灭活作用及对哺乳动物细胞的毒性 总被引:4,自引:0,他引:4
刘中民 张卓然 许国旺 杨凌 马磊 孙承林 许磊 齐越 赵春霞 明平文 陈严 郑丛龙 杜逊甫 韩秀文 张涛 黄向阳 包信和 刘波 刘守新 王爱琴 曲振平 缪少军 胡刚 刘页 《催化学报》2003,24(5):323-327
提出了以吸附和催化原理灭活病毒的设想,旨在开发出对病毒有过滤、吸附及灭活作用的高效非特异性催化材料,应用于各种防护设施,有效控制非典型肺炎(SARS)的传播.采用与SARS病毒相似的副流感病毒作为模拟对象,进行了吸附及灭活该病毒的催化材料研究,并考察了催化材料对哺乳动物细胞的毒性.结果表明,病毒气溶胶的阻留及吸附结果与基于DNA吸附的色谱分析结果相一致;部分材料可以强烈地吸附病毒(100%),甚至在强烈振荡下并洗脱至第3次,病毒也不能脱附;一些材料不仅可以吸附病毒,而且强烈振荡后的洗脱液虽然表现出一定的血凝效价,但接种鸡胚后,病毒并不增殖,说明材料具有明显的催化病毒灭活性能;对细胞毒性极低的材料可以用在与人体接触的防护材料和设施中.筛选出的性能优异的催化材料,拟进一步考察其对SARS病毒的灭活作用. 相似文献
7.
8.
Natural convection in an internally heated porous bed of height and diameter of 450 mm and 500 mm, respectively, and superposed with the fluid layer has been experimentally investigated. The onset of natural convection in the bed is indicated by change in the rate of temperature rise within the bed. An empirical model based on local Nusselt number and local Rayleigh number has been developed. A comparison of the present model with the models in literature is made to draw out the differences between the local heat transfer of large multidimensional beds and the average heat transfer of small beds. 相似文献
9.
基于建立的不同工艺尺寸的CMOS器件模型,利用TCAD器件模拟的方法,针对不同工艺CMOS器件,开展了不同工艺尺寸CMOS器件单粒子闩锁效应(SEL)的研究。研究表明,器件工艺尺寸越大,SEL效应越敏感。结合单粒子闩锁效应触发机制,提出了保护带、保护环两种器件级抗SEL加固设计方法,并通过TCAD仿真和重离子试验验证防护效果,得出最优的加固防护设计。结果表明,90nm和0.13μm CMOS器件尽量选用保护带抗SEL结构,0.18μm或更大工艺尺寸CMOS器件建议选取保护环抗SEL结构。 相似文献
10.
A Cu–Fe nanocomposite containing 50 nm thick iron filaments dispersed in a copper matrix was processed by torsion under high pressure at various strain rates and temperatures. The resulting nanostructures were characterized by transmission electron microscopy, atom probe tomography (APT) and Mössbauer spectrometry. It is shown that α-Fe filaments are dissolved during severe plastic deformation leading to the formation of a homogeneous supersaturated solid solution of about 12 at% Fe in fcc Cu. The dissolution rate is proportional to the total plastic strain but is not very sensitive to strain rate. Similar results were found for samples processed at liquid nitrogen temperature. APT data revealed asymmetric composition gradients resulting from deformation-induced intermixing. On the basis of these experimental data, the formation of the supersaturated solid solutions is discussed. 相似文献