全文获取类型
收费全文 | 139篇 |
免费 | 9篇 |
国内免费 | 9篇 |
专业分类
化学 | 37篇 |
力学 | 4篇 |
物理学 | 116篇 |
出版年
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2018年 | 4篇 |
2017年 | 8篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 59篇 |
2012年 | 4篇 |
2011年 | 7篇 |
2010年 | 7篇 |
2009年 | 3篇 |
2007年 | 3篇 |
2006年 | 9篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 1篇 |
1999年 | 6篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有157条查询结果,搜索用时 31 毫秒
51.
David A. Stonestrom Brian J. Andraski Clay A. Cooper C. Justin Mayers Robert L. Michel 《Isotopes in environmental and health studies》2013,49(2):250-256
We develop a general equation for converting laboratory-reported tritium levels, expressed either as concentrations (tritium isotope number fractions) or mass-based specific activities, to mass fractions in aqueous systems. Assuming that all tritium is in the form of monotritiated water simplifies the derivation and is shown to be reasonable for most environmental settings encountered in practice. The general equation is nonlinear. For tritium concentrations c less than 4.5×1012 tritium units (TU) – i.e. specific tritium activities<5.3×1011 Bq kg?1 – the mass fraction w of tritiated water is approximated to within 1 part per million by w ≈ c×2.22293×10?18, i.e. the conversion is linear for all practical purposes. Terrestrial abundances serve as a proxy for non-tritium isotopes in the absence of sample-specific data. Variation in the relative abundances of non-tritium isotopes in the terrestrial hydrosphere produces a minimum range for the mantissa of the conversion factor of [2.22287; 2.22300]. 相似文献
52.
K. Winkler A. Peters D. Karstent K.-H. Schneider J. Franke 《Isotopes in environmental and health studies》2013,49(6):206-212
Es wird ein automatischer Drehteller-Probenwechsler mit direkter optischer Ankopplung nur eines Szintillztionsmeßkopfes on die Probenküvetten beschrieben. 相似文献
53.
M. Krimissa L. Chery C. Fouillac J. L. Michelot 《Isotopes in environmental and health studies》2013,49(4):317-331
The thermo-mineral waters of the axial zone of the Eastern Pyrenees form a geochemically homogeneous group. They emerge in granite or orthogneiss and all have a sodium sulphide chemistry. Principal component analysis of their physico-chemical parameters has distinguished three types of fluid, 1) hot water that has evolved in a closed system and whose chemistry may reflect that of deep water, 2) water that is also of unmixed origin, but whose chemical composition has been modified during cooling by conduction, and 3) water cooled by mixing with surface water. Stable isotope (18O, 2H) contents indicate that all the waters are of meteoric origin (from oceanic and/or Mediterranean precipitation). No heavy isotope enrichment has been found that would indicate evaporation or a geothermal effect between water and the host rock. The differences in isotope contents between surface and thermo-mineral waters are attributed to a difference in recharge altitude; altitude gradients in 18O and 2H, estimated by two independent methods, are respectively 0.24‰ and 1.84° per 100m. They may, however, be lower when precipitation is in the form of snow. Applying these calculated gradients to thermo-mineral waters, taking mixing effects into account, has given an estimate of the minimum altitude of recharge of 110 springs in the Eastern Pyrenees. 相似文献
54.
T. M. James M. Schlsser S. Fischer M. Sturm B. Bornschein R. J. Lewis H. H. Telle 《Journal of Raman spectroscopy : JRS》2013,44(6):857-865
The Raman depolarization ratios for individual Q1(J”) branch lines of all diatomic hydrogen isotopologues – H2, HD, D2, HT, DT, and T2 – were measured, for all rotational levels with population larger than 1/100 relative to the Boltzmann maximum at room temperature. For these measurements, the experimental setup normally used for the monitoring of the tritiated hydrogen molecules at KArlsruhe TRItium Neutrino experiment was adapted to optimally control the excitation laser power and polarization, and to precisely define the Raman light collection geometry. The measured Raman depolarization values were compared to theoretical values, which are linked to polarizability tensor quantities. For this, the ‘raw data’ were corrected taking into account distinct aspects affecting Raman depolarization data, including (1) excitation polarization impurities; (2) extended Raman excitation volumes; and (3) Raman light collection over finite solid angles. Our corrected depolarization ratios of the hydrogen isotopologues agree with the theoretical values (based on ab initio quantum calculations by R.J. LeRoy, University of Waterloo, Canada) to better than 5% for nearly all of the measured Q1(J”) lines, with 1σ confidence level. The results demonstrate that reliable, accurate Raman depolarization ratios can be extracted from experimental measurements, which may be substantially distorted by excitation polarization impurities and by geometrical effects. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
55.
56.
通过计算流体力学(CFD)数值模拟方法,对氚增殖剂球床内部的氦气流动特性进行了初步研究。分析了球床流通长度和流通截面对提氚气体压降的影响,获得了不同入口流速下规则堆积球床和随机堆积球床的压降和阻力系数。 相似文献
57.
根据中国聚变工程实验堆(CFETR)堆芯设计参数及燃料系统流程模型,采用平均停留时间方法,建立燃料循环子系统的氚转移模型用来描述氚在各子系统之间的输运、滞留等过程。采用该模型,分析了不同聚变功率水平、运行因子以及燃烧率对中国聚变工程实验堆的氚平衡以及启动氚投料量的影响。 相似文献
58.
T. Matsuzaki K. Nagamine M. Tanase M. Kato K. Kurosawa K. Ishida S.N. Nakamura I. Watanabe G.H. Eaton 《Hyperfine Interactions》1999,119(1-4):361-363
For muon catalyzed fusion (μCF) experiments at RIKEN-RAL muon facility, a tritium gas handling system for a high purity D–T
target, free from 3 component, has been constructed to perform precise measurements of α-sticking probability in the μCF cycle. The system has
been constructed to enable us to purify the target D–T gas by removing 3He component, to adjust the D/T mixing ratio, and to measure the hydrogen isotope components at the experiment site. The whole
performance has been confirmed and a tritium gas with the inventory of 56 TBq (1500 Ci) has been operated in the system.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
59.
常温核聚变现象实验研究 总被引:2,自引:1,他引:1
介绍了1989~1992年在常温核聚变研究方面的主要进展。使用电解法观测到了中子和氚。使用气体放电法观测到了中子和X射线。使用气体升降温度压力循环法观测到了X光胶片感光现象,并初步弄清了感光原因。 相似文献
60.
A.R. Lakshmanan M.V.R. Prasad D. Ponraju H. Krishnan 《Journal of solid state chemistry》2004,177(10):3460-3468
A new technique of non-violent and fast dissolution of sodium metal in a concentrated aqueous solution of Epsom salt (MgSO4.7H2O) at room temperature (RT) has been developed. The dissolution process is mildly exothermic but could be carried out even in a glass beaker in air under swift stirring condition. The reaction products consist of mixed salts of MgSO4 and Na2SO4 as well as Mg(OH)2 which are only mildly alkaline and hence are non-corrosive and non-hazardous unlike NaOH. A 50 mL solution having Epsom salt concentration of 2 M was found to give the optimal composition for disposal of 1 g of sodium. Supersaturated (>2.7 M), as well as dilute (<1.1 M) solutions, however, cause violent reactions and hence should be avoided. Repeated sodium dissolution in Epsom solution produced a solid waste of 4.7 g per g of sodium dissolved which is comparable with the waste (4 g) produced in 8 M NaOH solution. A 1.4 M Epsom solution sprayed with a high-pressure jet cleaner at RT in air easily removed the sodium blocked inside a metal pipe made of mild steel. The above jet also dissolved peacefully residual sodium collected on the metal tray after a sodium fire experiment. No sodium fire or explosion was observed during this campaign. The Epsom solution spray effectively neutralized the minor quantity of sodium aerosol produced during this campaign. This novel technique would hence be quite useful for draining sodium from fast breeder reactor components and bulk processing of sodium as well as for sodium fire fighting. 相似文献